Reaktionen von Pentaphenylcyclopentadienylnickel-Komplexen mit Thiuramen und Dithiocarbamat: Nickel in den Oxidationsstufen I, II and III

Abstract Tetramethylthiuram monosulfide and tetramethylthiuram disulfide react with [(C 5 Ph 5 )Ni(NCCH 3 ) 2 ]BF 4 ( 2 ) to give the black pentaphenylcyclopentadienyl nickel complex [(C 5 Ph 5 )Ni{S 2 CN(CH 3 ) 2 }]BF 4 ( 7 ). Its crystal structure has been determined. It is the first 17-electron cyclopentadienyl nickel(III) compound to be structurally characterized. The formation reaction corresponds formally to an oxidative addition of tetramethylthiuram monosulfide and tetramethylthiuram disulfide to the nickel(II) complex 2 . The solid-state magnetic moment of the paramagnetic nickel(III) complex 7 is μ eff = 1,77 B.M. The reaction of sodium dimethyldithiocarbamate with [(C 4 Ph 5 )Ni(CO)Br] yields the dark-red pentaphenylcyclopentadienyl nickel(II) complex [(C 5 Ph 5 )Ni{S 2 CN(CH 3 )}] ( 6 ). Cyclic voltammetry reveals that the dithiocarbamate complex 6 can be oxidised electrochemically and chemically reversibly at +0.265 V vs. SCE to give the cation 7 . The reduction at −1.43 V leads to the nickel(I) complex [(C 5 Ph 5 Ni{S 2 CN(CH 3 ) 2 }] − . The nickel(III) complex 7 can also be prepared on a preparative scale by oxidation of 6 with ferrocene(1 + )tetrafluoroborate in dichloromethane. The reduction of 7 to give 6 is possible in dichloromethane with tetrakis(dimethylamino)ethylene as the reducing agent.