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 5Ph 5)Ni(NCCH 3) 2]BF 4 ( 2) to give the black pentaphenylcyclopentadienyl nickel complex [(C 5Ph 5)Ni{S 2CN(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 4Ph 5)Ni(CO)Br] yields the dark-red pentaphenylcyclopentadienyl nickel(II) complex [(C 5Ph 5)Ni{S 2CN(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 5Ph 5Ni{S 2CN(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.