Derivatives of N-phenylpyrazoles

• US 5,232,940 A
• Filed: 05/07/1990
• Issued: 08/03/1993
• Est. Priority Date: 12/20/1985
• Status: Expired due to Term

• Current Assignee: BASF Agro BV Arnhem (NL) Wadenswil Branch (BASF SE)
• Original Assignee: Rhone-Poulenc Agriculture Limited
• Inventors: Roberts, David A., Hawkins, David W., Buntain, Ian G., Pearson, Christopher J., Parnell, Edgar W., Hatton, Leslie R.
• Primary Examiner(s): Lee, Mary C.
• Assistant Examiner(s): McKane, Joseph K.
• Application Number:
  US07/520,290
• Time in Patent Office: 1,184 Days
• Field of Search: 548/375, 548/376, 548/377, 548/371.4, 548/372.1, 548/372.5, 514/407
• US Class Current: 514/407
• CPC Class Codes: A01N 43/56 1,2-Diazoles; Hydrogenated 1,2-diazoles
• CPC Class Codes: A01N 47/02 the carbon atom having no bond to a nitrogen atom
• CPC Class Codes: A01N 55/00 Biocides, pest repellants or attractants, or plant growth regulators, containing organic compounds containing elements other than carbon, hydrogen, halogen, oxygen, nitrogen and sulfur containing organo-phosphorus compounds A01N57/00
• CPC Class Codes: A61K 31/415 1,2-Diazoles
• CPC Class Codes: C07D 231/12 with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 231/14 with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
• CPC Class Codes: C07D 231/16 Halogen atoms or nitro radicals
• CPC Class Codes: C07D 231/18 One oxygen or sulfur atom
• CPC Class Codes: C07D 231/38 Nitrogen atoms nitro radicals C07D231/16
• CPC Class Codes: C07D 231/40 Acylated on said nitrogen atom
• CPC Class Codes: C07D 231/44 Oxygen and nitrogen or sulfur and nitrogen atoms
• CPC Class Codes: C07D 231/52 Oxygen atom in position 3 and nitrogen atom in position 5, or vice versa
• CPC Class Codes: C07D 403/04 directly linked by a ring-member-to-ring-member bond
• CPC Class Codes: C07F 7/0812 comprising a heterocyclic ring
• CPC Class Codes: C07F 7/0814 said ring is substituted at a C ring atom by Si

Abstract

N-Phenylpyrazole derivatives of the formula: ##STR1## wherein R¹ represents cyano, nitro, halogen, acetyl or formyl;

R² represents R⁵ SO₂, R⁵ SO or R⁵ S in which R⁵ is optionally halogen substituted alkyl, alkenyl or alkynyl;

R³ represents a hydrogen atom or a group NR⁶ R⁷ wherein R⁶ and R⁷ each represent hydrogen, alkyl, alkenylalkyl, alkynylalkyl, formyl, optionally halogen substituted alkanoyl, optionally halogen substituted alkoxycarbonyl, or alkoxymethyleneamino, halogen, or R⁶ and R⁷ together form a cyclic imide and R⁴ represents a substituted phenyl group possess arthropodicidal, plant nematocidal, anthelmintic and anti-protozoal properties; their preparation, compositions containing them and their use are described.

Claims

1. A method for the control or arthropod, plant nematode or helminth pests at a locus which comprises treatment of the locus with a pesticidally effective amount of a compound of the formula:

wherein;

R² represents a halogen atom, the cyano or nitro group or a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms, a cycloalkyl group having from 3 to 5 carbon atoms, a straight- or branched-chain alkenyl group having from 2 to 6 carbon atoms, or R² represents the thiocyanato group, the sulphamoyl group which is unsubstituted or substituted by one or two straight- or branched-chain alkyl groups which may be the same or different and which have from 1 to 6 carbon atoms, the carbamoyl group which may be unsubstituted or substituted by one or two straight- or branched-chain alkyl groups which may be the same or different and which have from 1 to 6 carbon atoms, a straight- or branched-chain alkoxycarbonyl group having from 2 to 7 carbon atoms, a straight- or branched-chain alkanoyl group having from 2 to 7 carbon atoms, or a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms;

R³ represents the hydrogen atom, or the amino group --NR"R"'"'"' wherein R" and R"", which may be the same or different, each represent a hydrogen atom or a straight- or branched-chain alkyl group (having from 1 to 6 carbon atoms, and which is unsubstituted or substituted by straight- or branched-chain alkoxycarbonyl of 2 to 5 carbon atoms), cycloalkyl group having from 3 to 6 carbon atoms, formyl group, straight- or branched-chain alkanoyl group (which has from 2 to 7 carbon atoms or together form a 5- or 6-membered cyclic imide with the nitrogen atom to which they are attached and themselves are unsubstituted or substituted by one or more halogen atoms) or cycloalkylcarbonyl group (which has from 4 to 7 carbon atoms) or straight- or branched-chain alkoxycarbonyl group (which has from 2 to 7 carbon atoms and themselves are unsubstituted or substituted by one or more halogen atoms), or R³ represents a straight- or branched-chain alkylsulphenylamino group having from 1 to 4 carbon atoms, a straight- or branched-chain alkoxymethyleneamino group having from 2 to 5 carbon atoms which is unsubstituted or substituted on methylene by a straight- or branched-chain alkyl group having from 1 to 4 carbon atoms, or represents a halogen atom, a straight- or branched-chain alkyl group having from 1 to 4 carbon atoms, the carboxy group, or a straight- or branched-chain alkylthio, alkylsulphinyl or alkylsulphonyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms, or represents a straight- or branched-chain trialkylsilylmethyl group having from 1 to 6 carbon atoms in each alkyl group which may be the same or different, a trialkylsilyl group having from 1 to 6 carbon atoms in each alkyl group which may be the same or different or the cyano or nitro group;

R⁴ -R⁸ each represent a hydrogen atom, a halogen atom, a straight- or branched-chain alkyl or alkoxy group having from 1 to 4 carbon atoms which is unsubstituted or substituted by one or more halogen atoms, a straight- or branched-chain alkylthio or alkylsulphinyl group having from 1 to 4 carbon atoms which is substituted by one or more halogen atoms, the nitro or cyano group or a straight- or branched-chain alkylsulphonyl group having from 1 to 4 carbon atoms which is unsubstituted or substituted by one or more halogen atoms, provided that at least one of R₄ -R₈ must be other than a hydrogen atom; and

R¹ represents a halogen atom, or a cyano or nitro group;

or when R³ represents a carboxy group, a slat thereof with a pesticidally acceptable base;

provided that R¹, R² and R³ do not simultaneously represent three groups of the same genus selected from the genera (i) nitro, (ii) cyano, (iii) halogen, and (iv) unsubstituted alkyl.

2. A method according to claim 1, wherein the compound of formula (I) is 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole or 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole.

3. An arthropodicidal, plant nematocidal or anthelmintic composition comprising a pesticidally effective amount of a compound of formula (I) as defined in claim 1, or a pesticidally acceptable salt thereof, in association with one or more compatible carriers, with the provisos that (1) when R¹ represents chloro, R² represents nitro, R³ represents methyl, R⁶ represents nitro and R⁴, R⁵ , R⁷ and R⁸ each represent hydrogen, the composition is other than a plant nematocidal composition and comprises a pharmaceutically acceptable adjuvant or a feedstuff or is substantially sterile and pyrogen-free or is in unit dosage form;

and (2) the composition excludes 1-(4-nitrophenyl)-3-nitro-4-pyrazolecarbonitrile or carboxamide.

4. A compound of the formula ##STR7## wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are as defined in claim 1, excluding:

(1) a compound of formula (I) wherein R¹ represents chloro, R² represents nitro, R³ represents methyl, R⁶ represents nitro and R⁴, R⁵, R⁷ and R⁸ each represent hydrogen;

(2) a compound of formula (I) wherein R¹ represents nitro, R² represents cyano or --CONH₂, R³ represents hydrogen, R⁶ represents nitro and R⁴, R⁵, R⁷ and R⁸ each represent hydrogen;

(3) a compound of formula (I) wherein R¹ and R² each represent cyano, R³ represents amino and (a) R⁵ represents nitro and R⁴, R⁶, R⁷ and R⁸ each represent hydrogen, or (b) R⁶ represents nitro and R⁴, R⁵, R⁷ and R⁸ each represent hydrogen, or (c) R⁶ represents chloro and R⁴, R⁵, R⁷ and R⁸ each represent hydrogen;

(4) a compound of formula (I) wherein R¹ represents bromine, R² represents methyl, R³ represents hydrogen and (a) R⁴ and R⁶ each represent nitro and R⁵, R⁷ and R⁸ each represent hydrogen, or (b) R⁴, R⁶ and R⁸ each represent nitro and R⁵ and R⁷ each represent hydrogen;

(5) a compound of formula (I) wherein R¹ and R² each represent bromine, R³ represents methyl and (a) R⁴ and R⁶ each represent nitro and R⁵, and R⁷ and R⁸ each represent hydrogen, or (b) R⁴, R⁶ and R⁸ each represent nitro and R⁵ and R⁷ each represent hydrogen;

(6) a compound of formula (I) wherein R¹ and R² each represent bromine, R³ represents hydrogen, R⁴ and R⁶ each represent nitro and R⁵, R⁷ and R⁸ each represent hydrogen;

(7) a compound of formula (I) wherein R¹ and R² each represent chlorine, R³ represents methyl, R⁴ and R⁶ each represent nitro and R⁵, R⁷ and R⁸ each represent hydrogen;

(8) a compound of formula (I) wherein R¹ represents chlorine, R² represents bromine, R³ represents methyl, R⁴ and R⁶ each represent nitro and R⁵, R⁷ and R⁸ each represent hydrogen;

(9) a compound of formula (I) wherein R¹ represents nitro, R² represents methyl, R³ represents hydrogen, R⁴, R⁶ and R⁸ each represent nitro and R⁵ and R⁷ each represent hydrogen;

(10) a compound of formula (I) wherein R¹ and R² each represent bromine, R³ represents hydrogen, R⁶ represents bromine and R⁴, R⁵, R⁷ and R⁸ each represent hydrogen;

(11) a compound of formula (I) wherein R⁴ and R⁶ each represent nitro, R⁵, R⁷ and R⁸ each represent hydrogen, and R¹, R² and R³ represent, respectively;

chlorine, bromine and hydrogen;

or chlorine, methyl and hydrogen;

(12) a compound of formula (I) wherein R⁶ represents nitro, R⁴, R⁵, R⁷ and R⁸ each represent hydrogen, and R¹, R² and R³ represent, respectively;

bromine, methyl and hydrogen;

nitro, methyl and hydrogen; and

cyano, methoxycarbonyl and amino; and

(13) R¹, R² and R³ represent, respectively, nitro, methyl and nitro, R⁴ and R⁶ each represent nitro and R⁵, R⁷ and R⁸ each represent hydrogen.

5. A compound according to claim 4, which is 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole or 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole.

6. An arthropodicidal, plant nematocidal or anthelmintic composition comprising a pesticidally effective amount of a compound of formula (I) as defined in claim 4, or a pesticidally acceptable salt thereof, in association with one or more compatible carriers.

9. A method according to claim 1, wherein R¹ represents a cyano group.

10. A method according to claim 1, wherein R² represents a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms.

11. A composition according to claim 3, wherein R¹ represents a cyano group.

12. A composition according to claim 3, wherein R² represents a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms.

13. A compound according to claim 4, wherein R¹ represents a cyano group.

14. A compound according to claim 4, wherein R² represents a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms.

15. A composition according to claim 6, wherein R¹ represents a cyano group.

16. A composition according to claim 6, wherein R² represents a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms.

20. The method according to claim 1, wherein the compound of formula I is:

5-amino-3,4-dicyano-1-(2,4,6-trichlorophenyl)pyrazole;

5-amino-3,4-dicyano-1-2,3,5,6-tetrachlorophenyl)-pyrazole;

5-amino-3-chloro-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-bromo-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-iodo-4-cyano-1(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-acetamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-dichloroacetamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-cyclopropylcarbonamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-pentanamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-propionamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole

5-amino-1-(2-chloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-3,4-dicyano-1-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)pyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-(2,2-dimethylpropionamido)pyrazole;

5-amino-3,4-dicyano-1-(2,6-dichloro-4-trifluoromethylthiophenyl)pyrazole;

5-amino-1-(2-chloro-3,5,6-trifluoro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-3,5-difluoro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-4-nitrophenyl)-3,4-dicyanopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-methylaminopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-ethylaminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-trimethylacetylaminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-bis(ethoxycarbonyl)aminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-ethoxycarbonylaminopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(ethoxycarbonyl)amino-3,4-dicyanopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-ethoxycarbonylaminopyrazole;

4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-fluoropyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-3-nitropyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-nitropyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-3-fluoropyrazole;

5-amino-3-chloro-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-cyanopyrazole;

or

5-amino-3-chloro-4-cyano-1-(2,6-dichloro-3,5-difluoro-4-trifluoromethylphenyl)pyrazole.

21. The compound according to claim 4, which is:

5-amino-3,4-dicyano-1(2,4,6-trichlorophenyl)pyrazole;

5-amino-3,4-dicyano-1-(2,3,5,6-tetrachlorophenyl)pyrazole;

5-amino-3-chloro-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-bromo-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-iodo-4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-acetamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-dichloroacetamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-cyclopropylcarbonamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-pentanamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4dicyanopyrazole;

5-propionamido-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-3,4-dicyano-1-(2,3,5,6-tetrafluoro-4-trifluoromethylphenyl)pyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-(2,2-dimethylpropionamido)pyrazole;

5-amino-3,4-dicyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-1-(2-chloro-3,5,6-trifluoro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-3,5-difluoro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,5-dicyanopyrazole;

5-amino-1-(2,6-dichloro-4-nitrophenyl)-3,4-dicyanopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-methylaminopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-ethylaminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-trimethylacetylaminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-bis(ethoxycarbonyl)aminopyrazole;

3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-5-ethoxycarbonylaminopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(ethoxycarbonyl)amino-3,4-dicyanopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-ethoxycarbonylaminopyrazole;

4-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-fluoropyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-3-nitropyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyano-5-nitropyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyano-3-fluoropyrazole;

5-amino-3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-cyanopyrazole;

or

5-amino-3-chloro-4-cyano-1-(2,6-dichloro-3,5-difluoro-4-trifluoromethylphenyl)pyrazole.

39. A method according to claim 1 for the control of arthropod pests wherein, in formula I, R² is other than a group R'"'"'SO or R'"'"'S in which R represents a straight- or branched-chain alkyl group containing from 1 to 6 carbon atoms which is substituted by one or more halogen atoms or the thiocyanato group;

R³ is other than an amino group--NR"R"'"'"' wherein R" or R"'"'"' represents a cycloalkyl group containing from 3 to 6 carbon atoms, or straight- or branched-chain alkylthio, alkylsulphinyl or alkylsulphonyl which is substituted by one or more halogen atoms, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group;

R⁴ -R⁸ each represent a hydrogen atom, halogen atom, a straight- or branched-chain alkyl or alkoxy group containing from 1 to 4 carbon atoms, a trifluoromethyl, trifluoromethoxy, trifluoromethylthio, trifluoromethylsulphinyl or trifluoromethylsulphonyl, a nitro or cyano group or a straight- or branched-chain alkylsulphonyl group containing from 1 to 4 carbon atoms; and

R¹ is other than nitro.

40. A method according to claim 1 for the control of arthropods or helminths which are parasitic internally or externally upon vertebrates.

41. A method according to claim 1 for the control of arthropod or nematode pests of plants at a locus which comprises the application to the locus of a pesticidally effective amount of a compound of formula I or a pesticidally acceptable salt thereof.

42. A method according to claim 1 for the control of arthropods or helminths in man and domestic animals by oral, parenteral, percutaneous or topical administration.

43. A method according to claim 1 wherein in formula I R⁴ -R⁸ represent 2,4,6-trichloro, 2,3,5,6-tetrachloro, 2-chloro-4-trifluoromethyl, 2,3,5,6-tetrafluoro-4-trifluoromethyl, 2,6-dichloro-4-trifluoromethylthio, 2-chloro-3,5,6-trifluoro-4-trifluoromethyl, 2,6-dichloro-3,5-difluoro-4-trifluoromethyl, 2,6-dichloro-4-nitro, 2,6-dichloro-4-trifluoromethylsulphinyl, 2,6-dichloro-4-methanesulphonyl or 2,6-dichloro-4-trifluoromethanesulphonyl substitution.

44. A method according to claim 1 in formula I R⁴ -R⁸ represent 2,6-dichloro-4-trifluoromethyl or 2,6-dichloro-4-trifluoromethoxy substitution.

45. A method according to claim 1 wherein formula I:

(a) R² and R¹ each represent a cyano group and R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group;

(b) R² represents an alkylsulphonyl group which is optionally halogen substituted, a cycloalkylsulphonyl group or an alkenylsulphonyl group, R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the cyano or nitro group and R¹ represents a halogen atom or the cyano or nitro group;

(c) R¹ represents the nitro group, R² represents the cyano or nitro group, a carbamoyl group or an alkoxycarbonyl group and R³ represents the hydrogen atom, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group; and

(d) R¹ represents a halogen atom, R² represents the cyano or nitro group, a carbamoyl group or an alkoxycarbonyl group and R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group.

46. A method according to claim 1 wherein the compound of formula I is 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3,4-dicyanopyrazole.

47. A method according to claim 1 wherein the compound of formula I is 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole.

48. A composition according to claim 6 suitable for administration to vertebrates or man by oral, parenteral, percutaneous or topical administration to control arthropod or helminth pests.

49. A composition according to claim 6 for application to growing crops and crop growing loci or as a seed dressing.

50. A solid or liquid composition according to claim 6 for application topically to animals, timber, stored products or household goods which comprises from 0.001% to 10% by weight of a compound of formula I or a pesticidally acceptable salt thereof.

51. A solid or liquid composition according to claim 6 for oral or parenteral, including percutaneous, administration to animals which comprises from 0.1% to 90% by weight of compound of formula I or a pesticidally-acceptable salt thereof.

52. A dust or liquid composition according to claim 6 for application to livestock, persons, goods, premises or outdoor areas which comprises from about 0.005% to about 2.0% by weight of a compound of formula I or a pesticidally-acceptable salt thereof.

53. A composition according to claim 6 wherein the compound of formula I is 5-amino-1-(2,6-dichloro-4-trifluoromethyl-phenyl)-3,4-dicyanopyrazole.

54. A compound according to claim 4 wherein R⁴ -R⁸ represent 2,4,6-trichloro, 2,3,5,6-tetrachloro, 2-chloro-4-trifluoromethyl, 2,3,5,6-tetrafluoro-4-trifluoromethyl, 2,6-dichloro-4-trifluoromethylthio, 2-chloro-3,5,6-trifluoro-4-trifluoromethyl, 2,6-dichloro-3,5-difluoro-4-trifluoromethyl, 2,6-dichloro-4-nitro, 2,6-dichloro-4-trifluoromethylsulphinyl, 2,6-dichloro-4-methanesulphonyl or 2,6-dichloro-4-trifluoromethanesulphonyl substitution.

55. A compound according to claim 1 wherein R⁴ -R⁸ represent 2,6-dichloro-4-trifluoromethyl or 2,6-dichloro-4-trifluoromethoxy substitution.

56. A compound according to claim 1 wherein

R² and R¹ each represent a cyano group and R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl of alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group;

(b) R² represents an alkylsulphonyl group which is optionally halogen substituted, a cycloalkylsulphonyl group or an alkenylsulphonyl group, R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the cyano or nitro group and R¹ represents a halogen atom or the cyano or nitro group;

(c) R¹ represents the nitro group, R² represents the cyano or nitro group, a carbamoyl group or an alkoxycarbonyl group and R³ represents the hydrogen atom, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group; and

(d) R¹ represents a halogen atom, R² represents the cyano or nitro group, a carbamoyl group or an alkoxycarbonyl group and R³ represents the hydrogen atom, the amino group --NR"R"'"'"' or an alkylsulphenylamino group, an alkoxymethyleneamino group which is unsubstituted or substituted on methylene by an alkyl group, a halogen atom, an alkyl group, the carboxy group, an alkylthio, alkylsulphinyl or alkylsulphonyl group which is optionally halogen substituted, a trialkylsilylmethyl group, a trialkylsilyl group or the nitro group.

57. A compound according to claim 1 wherein R¹ represents a trifluoromethyl or methyl group.

58. An N-phenylpyrazole derivative according to claim 1, comprising ##STR12## wherein n is 0, 1, or 2.

59. An N-phenylpyrazole derivative according to claim 1, consisting of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole.

60. An N-phenylpyrazole derivative according to claim 1, consisting of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole.

61. An N-phenylpyrazole derivative according to claim 1, consisting of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole.

7. A compound of the formula ##STR8## wherein:

R¹ represent a cyano or nitro group, a halogen atom, or an acetyl or formyl group;

R² represents a group R'"'"'SO₂, R'"'"'SO, or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl, alkenyl or alkynyl group of up to 4 carbon atoms which may be unsubstituted or substituted by one or more halogen atoms which may be the same or different;

R³ represents a hydrogen atom or an amino group --NR"R"'"'"' wherein R" and R"'"'"', which may be the same or different, each represent a hydrogen atom or a straight- or branched-chain alkyl, alkenylalkyl or alkynylalkyl group of up to 5 carbon atoms, a formyl group, a straight- or branched-chain alkanoyl group (which is of 2 to 5 carbon atoms and which may be optionally substituted by one or more halogen atoms), or R" and R"'"'"' together with the nitrogen atom to which they are attached form a 5 or 6 membered cyclic imide, or represents a straight- or branched-chain alkoxycarbonyl group (which is of 2 to 5 carbon atoms and is unsubstituted or substituted by one or more halogen atoms), or R³ represents a straight- or branched-chain alkoxymethyleneamino group of 2 to 5 carbon atoms which may be unsubstituted or substituted on methylene by a straight- or branched-chain alkyl group of 1 to 4 carbon atoms or represents a halogen atom;

R⁴ represents a fluorine, chlorine, bromine or iodine atom;

R⁶ represents a straight- or branched-chain alkyl or alkoxy group of 1 to 4 carbon atoms, which may be unsubstituted or substituted by one or more halogen atoms which may be the same or different, or a chlorine or bromine atom;

R⁵ and R⁷ are hydrogen; and

R⁸ is hydrogen or a fluorine, chlorine, bromine or iodine atom, with the exclusion of the compound wherein R¹ represents cyano, R² represents methanesulphonyl, R³ represents amino, R⁴ and R⁸ each represent chlorine, and R⁶ represents trifluoromethyl.

17. A compound according to claim 7, wherein R¹ represents a cyano group.

18. A compound according to claim 7, wherein R² represents a group R'"'"'SO₂, R'"'"'SO or R'"'"'S in which R'"'"' represents a straight- or branched-chain alkyl group having from 1 to 6 carbon atoms which is unsubstituted or substituted by one or more halogen atoms.

22. A compound according to claim 7 wherein R¹ is other than a formyl group and neither R" nor R"'"'"' represents an alkenylalkyl or alkynylalkyl group.

23. A compound according to claim 7 wherein R² represents an alkylsulphonyl/sulphinyl/thio group which is optionally halogen substituted and of 1 to 4 carbon atoms, or an alkenyl- or alkynyl-sulphonyl/-sulphinyl/thio group which is optionally halogen substituted and of up to 4 carbon atoms, R³ represents the hydrogen atom, an amino or methylamino group and R¹ represents a halogen atom or a cyano or nitro group.

24. A compound according to claim 23 wherein R¹ represents a cyano or nitro group.

25. A compound according to claim 7 wherein at least one of R⁴ -R⁸ is a trifluoromethyl or trifluoromethoxy group and R² represents an optionally halogenated alkylsulphonyl/sulphinyl/thio group of 1 to 4 carbon atoms.

26. A compound according to claim 25 wherein R² represents a trifluoromethylthio, trifluoromethylsulphinyl or trifluoromethylsulphonyl group.

27. A compound according to claim 7 wherein the substituent ##STR10## represents a 2,4,6-trichloro-, 2-6-dichloro-4-difluoromethoxy-, 2-chloro-4-trifluoromethyl-, 2-bromo-6-chloro-4-trifluoromethyl-, 2,6-dibromo-4-triflouromethyl- or 2-bromo-4-trifluoromethyl-phenyl group.

28. A compound according to claim 7 wherein the substituent ##STR11## represents a 2,6-dichloro-4-trifluoromethyl- or 2,6-dichloro-4-trifluoromethoxy-phenyl group.

29. The compound according to claim 7, which is

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-difluoromethoxyphenyl)-4-trifluoromethylthiopyrazole;

5-amino-1-(2-chloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,4,6-trichlorophenyl)-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dibromo-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

5-amino-1-(2-bromo-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-difluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-heptafluoropropylthiopyrazole;

5-amino-1-(2-bromo-6-chloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trichloromethylthiopyrazole;

5-amino-3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-fluoro-4-trifluoromethylthiopyrazole;

5-amino-4-chlorodifluormethylthio-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-chloro-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

5-amino-3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxymethyleneamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxyethylideneamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxymethyleneamino-4-methanesulphonylpyrazole;

5-acetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(propionyl)amino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-propionamido-4-trifluoromethylthiopyrazole;

5-acetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthio-5-trimethylacetamidopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(methoxycarbonyl)amino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(ethoxycarbonyl)amino-4-trifluoromethylthiopyrazole;

5-chloroacetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(ethoxycarbonyl)amino-4-methanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonyl-5-trimethylacetamidopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-dimethylamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-isopropylamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-propylamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-dipropylamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(propargyl)amino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-methylamino-4-methanesulphonylpyrazole;

5-bromo-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole;

5-bromo-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

5-bromo-3-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-iodo-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-iodo-4-trifluoromethanesulphonylpyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-iodo-4-methanesulphonylpyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3-iodo-4-methanesulphonylpyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3-iodo-4-trifluoromethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-trifluoromethanesulphonylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-4-trifluoromethylsulphinylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-(1-methylprop-2-ynylsulphinyl)pyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methylsulphinylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-isopropylsulphinylpyrazole;

5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole;

5-amino-4-tert-butanesulphonyl-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-propylamino-4-trifluoromethylsulphonylpyrazole;

5-acetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonyl-3-nitropyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonyl-3-nitropyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3-nitro-4-trifluoromethylsulphinylpyrazole;

5-amino-1-(2-bromo-6-chloro-4-trifluoromethylphenyl)-3-cyano-4-methanesulphonylpyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethoxyphenyl)-3-cyano-4-methanesulphonylpyrazole;

3-acetyl-5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methanesulphonylpyrazole;

5-amino-3cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-ethylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-propylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-isopropylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-(2-methylpropylthio)pyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-(1-methylpropylthio)pyrazole;

4-allylthio-5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-(prop-2-ynylthio)pyrazole;

5-amino-3-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-(1-methylprop-2-ynylthio)pyrazole;

5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methylthiopyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-tert-butylthiopyrazole;

5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-methylsulphinylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-ethanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-methylamino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-(N-ethoxycarbonyl-N-methyl)amino-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-trifluoroacetamido-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-(ethoxycarbonylamino)-4-trifluoromethylthiopyrazole;

3-acetyl-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole;

1-(2,6-dichloro-4-trifluoromethylphenyl)-3-formyl-4-trifluoromethylthiopyrazole;

5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-formyl-4-trifluoromethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-fluoro-4-trifluoromethanesulphonylpyrazole;

5-amino-3-cyano-4-dichlorofluoromethylthio-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

5-amino-3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethanesulphonylpyrazole;

5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-pentafluoroethylthiopyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-dimethylamino-4-trifluoromethylsulphinylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-iodo-4-trifluoromethylsulphinylpyrazole;

5-bromo-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole;

5-acetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulphinylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-bis(ethoxycarbonyl)amino-4-trifluoromethanesulphonylpyrazo;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxycarbonylamino-4-trifluoromethanesulphonylpyrazole;

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxymethyleneamino-4-trifluoromethanesulphonylpyrazole;

5-amino-4-(2-chloro-1,1,2-trifluoroethylthio)-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole;

or

3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-dimethylamino-4-trifluoromethanesulphonylpyrazole.

30. An arthropodicidal, plant nematocidal, anthelmintic or anti-protozoal composition which comprises a pesticidally effective amount of a compound according to claim 7 in association with one or more compatible carriers.

31. A method for the control of arthropod, plant nematode, helminth or protozoal pests at a locus which comprises treatment of the locus with a pesticidally effective amount of a compound according to claim 7.

62. A composition according to claim 30, comprising an effective amount of a compound as defined in claim 30 wherein R¹ is other than a formyl group and neither R" nor R"'"'"' represents an alkenylalkyl or alkynylalkyl group.

63. A composition according to claim 30, comprising an effective amount of a compound as defined in claim 30 wherein R² represents an alkylsulphonyl/sulphinyl/thio group which is optionally halogen substituted and of 1 to 4 carbon atoms, or an alkenyl- or alkynyl- sulphonyl/sulphinyl/thio group which is optionally halogen substituted and of up to 4 carbon atoms, R³ represents the hydrogen atom, an amino or methylamino group and R¹ represents a halogen atom or a cyano or nitro group.

64. A composition according to claim 63, wherein R¹ represents a cyano or nitro group.

65. A composition according to claim 30, comprising an effective amount of a compound as defined in claim 30 wherein at least one of R⁴ -R⁸ is a trifluoromethyl or trifluoromethoxy group and R² represents an optionally halogenated alkylsulphonyl/sulphinyl/thio group of 1 to 4 carbon atoms.

66. A composition according to claim 65, wherein R² represents a trifluoromethylthio, trifluoromethylsulphinyl or trifluoromethylsulphonyl group.

67. A composition according to claim 30, comprising an effective amount of a compound as defined in claim 30 wherein the substituent ##STR13## represents a 2,6-dichloro-4-trifluoromethylphenyl) or 2,6-dichloro-4-trifluoromethoxyphenyl group.

68. The composition according to claim 30, comprising an effective amount of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole.

69. A method according to claim 31, comprising treating the locus with an effective amount of a compound as defined in claim 31 wherein R¹ is other than a formyl group and neither R" nor R"'"'"' represents an alkenylalkyl or alkynylalkyl group.

70. A method according to claim 31, comprising treating the locus with an effective amount of a compound as defined in claim 31 wherein R² represents an alkylsulphonyl/sulphinyl/thio group which is optionally halogen substituted and of 1 to 4 carbon atoms, or an alkenyl- or alkynyl- sulphonyl/sulphinyl/thio group which is optionally halogen substituted and of up to 4 carbon atoms, R³ represents the hydrogen atom, an amino or methylamino group and R¹ represents a halogen atom or a cyano or nitro group.

71. A method according to claim 70, wherein R¹ represents a cyano or nitro group.

72. A method according to claim 31, comprising treating the locus with an effective amount of a compound as defined in claim 31 wherein at least one of R⁴ -R⁸ is a trifluoromethyl or trifluoromethoxy group and R² represents an optionally halogenated alkylsulphonyl/sulphinyl/thio group of 1 to 4 carbon atoms.

73. A method according to claim 72, wherein R² represents a trifluoromethylthio, trifluoromethylsulphinyl or trifluoromethylsulphonyl group.

74. A method according to claim 31, comprising treating the locus with an effective amount of a compound as defined in claim 31 wherein the substituent ##STR14## represents a 2,6-dichloro-4-trifluoromethylphenyl or 2,6-dichloro-4-trifluoromethoxyphenyl group.

75. The method according to claim 31, comprising treating the locus with an effective amount of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylthiopyrazole.

8. A compound of the formula ##STR9## wherein R⁸ represents a fluorine, chlorine or bromine atom, R⁶ represents a chlorine or bromine atom, or a straight- or branched-chain alkyl or alkoxy group of 1 to 4 carbon atoms which may be unsubstituted or substituted by one or more halogen atoms, R⁴ is as defined for R⁸ or represents the hydrogen atom, R¹ represents a halogen atom or the cyano or nitro group, R³ represents the hydrogen atom, or the amino group --NR"R"'"'"' wherein R" and R"'"'"', which may be the same or different, each represent the hydrogen atom or a straight- or branched-chain alkyl group of 1 to 6 carbon atoms, the formyl group, a straight- or branched-chain alkanoyl group of 2 to 7 carbon atoms, (or R" and R"'"'"' together form a 5 or 6 membered cyclic imide with the nitrogen atom to which they are attached) which may be unsubstituted or substituted by one or more halogen atoms, or a straight- or branched-chain alkoxycarbonyl group of 2 to 7 carbon atoms, which may be unsubstituted or substituted by one or more halogen atoms, or R³ represents a straight- or branched-chain alkoxymethyleneamino group of 2 to 5 carbon atoms which may be unsubstituted or substituted on methylene by a straight- or branched-chain alkyl group of 1 to 4 carbon atoms, or represents a fluorine, chlorine, bromine or iodine atom.

19. A compound according to claim 8, wherein R¹ represents a cyano group.

32. A compound according to claim 8 wherein R⁶ represents a trifluoromethyl or trifluoromethoxy group.

33. A compound according to claim 8 wherein R⁸, R⁶ and R⁴ together represent 2,4,6-trichloro, 2,6-dichloro-4-trifluoromethyl or 2,6-dichloro-4-trifluoromethoxy substitution of the phenyl group.

34. A compound according to claim 8 wherein R³ represents the hydrogen atom or --NR"R"'"'"' and R⁸, R⁶ and R⁴ together represent 2,6-dichloro-4-trifluoromethyl or 2,6-dichloro-4-trifluoromethoxy substitution of the phenyl group.

35. A compound according to claim 8 wherein R³ represents an amino or acetamido group.

36. A compound according to claim 8 is 5-acetamido-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole, 5-acetamido-3-chloro-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole, 5-acetamido-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole, 5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole, 5-amino-3-chloro-1-(2,6-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole and 5-bromo-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole.

37. An arthropodicidal, plant nematocidal, anthelmintic or anti-protozoal composition which comprises an effective amount of a compound according to claim 8 in association with one or more compatible diluents or carriers.

38. A method for the control of arthropod, plant nematode, helminth or protozoal pest at a locus which comprises treatment of the locus with an effective amount of a compound according to claim 8.