A series of neutral radical CpNi(dithiolene)• complexes

The heteroleptic neutral radical dithiolene complexes CpNi(dmit)(center dot), CpNi(dsit)(center dot) and CpNi(dmid)(center dot) (dmit = 1,3-dithiole-2-thione-4,5-dithiolate; dsit = 1,3-dithiole-2-thione-4,5-diselenolate; dmid = 1,3-dithiole-2-one-4,5-dithiolate) are obtained from the reaction of (Cp2Ni)BF4 with either (n-Bu4N)[Ni(dmit)(2)] and (n-Bu4N)[Ni(dmid)(2)] or PhSb(dmit) and PhSb(dsit), respectively. The three complexes reduce reversibly to the corresponding Ni(II) anions and oxidize reversibly to the cationic state. As deduced from DFT calculations performed on CpNi(dmit)(center dot), the SOMO of these complexes is essentially localized on the dithiolene moiety with little metal contribution. CpNi(dsit)(center dot) is isostructural with CpNi(dmit)(center dot) and crystallizes in the monoclinic system, space group P2(1). In the solid-state structures of both CpNi(dmit)(center dot) and CpNi(dsit)(center dot), molecules interact through a three-dimensional set of intermolecular interactions mediated by short S center dot center dot center dot S, Se center dot center dot center dot Se and S center dot center dot center dot Se contacts, as confirmed from the temperature and field dependence of the magnetic susceptibility by the observation of an antiferromagnetic ground state below T-Neel = 27 K in CpNi(dmit)(center dot), 18 K in CpNi(dsit)(center dot). Finally, CpNi(dmid)(center dot) crystallizes in the orthorhombic system, space group Pnma. Molecules organize into uniform chains through the stacking of the dmid moieties in a sigma-type face-to-face overlap.