Cyano substituted cycloalkanes

A compound of formula (I); wherein R is Ar-(CH2)n- where n is zero or one and Ar is an optionally substituted phenyl or an optionally substituted 5- or 6-membered heterocyclic ring system containing from 1 to 3 heteroatoms independently selected from nitrogen, oxygen and sulfur atoms, and at least one unsaturation (double bond) between adjacent atoms in the ring, wherein the substituents, if present, are selected from halogen atoms, alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, haloalkenyl, haloalkoxy, alkylthio and alkyl amino groups, said groups having up to six carbon atoms; wherein R and R and independently hydrogen or a group selected from alkyl, aryl, heteroaryl, aralkyl, formyl, alkylcarbonyl, arylcarbonyl, heteroarylalkyl, alkenyl, aralkenyl, alkynyl, alkoxycarbonyl, alkanesulfonyl, phenylsulfonyl, alkenyloxycarbonyl, aralkyloxycarbonyl, aryloxycarbonyl, heterocyclylalkyl, carbamyl or dithiocarboxyl groups; alkyl moieties of R and R comprise from 1 to 15 carbon atoms, and are optionally substituted with one or more substituents selected from halogen, cyano, carboxyl, carboxylic acyl, formyl, carbamyl, alkoxycarbonyl, alkoxy, alkylenedioxy, hydroxy, nitro, amino, acylamino, imidate and phosphonato groups; aryl, heteroaryl, aralkyl, heteroarylalkyl, alkenyl, aralkenyl, alkynyl, alkoxycarbonyl, alkanesulfonyl, phenylsulfonyl, alkenyloxycarbonyl, aralkyloxycarbonyl, aryloxycarbonyl, heterocyclylalkyl, carbamyl and dithiocarboxyl moieties of R and R are optionally substituted with one or more substituents selected from halogen, cyano, carboxyl, carboxylic acyl, formyl, carbamyl, alkoxycarbonyl, alkoxy, alkylenedioxy, hydroxy, nitro, haloalkyl, alkyl, amino, acylamino, imidate and phosphonato groups; or an acid addition salt, quaternary ammonium salt or N-oxide derived therefrom; compositions comprising a compound of formula (I) and a carrier or diluent; and a method of combating insect, acarine or nematode pests using a compound or composition as defined hereinbefore.