A series of neutral radical CpNi(dithiolene)˙ complexes

Abstract

The heteroleptic neutral radical dithiolene complexes CpNi(dmit)˙, CpNi(dsit)˙ and CpNi(dmid)˙ (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)˙, the SOMO of these complexes is essentially localized on the dithiolene moiety with little metal contribution. CpNi(dsit)˙ is isostructural with CpNi(dmit)˙ and crystallizes in the monoclinic system, space group P2₁. In the solid-state structures of both CpNi(dmit)˙ and CpNi(dsit)˙, molecules interact through a three-dimensional set of intermolecular interactions mediated by short S⋯S, Se⋯Se and S⋯Se contacts, as confirmed from the temperature and field dependence of the magnetic susceptibility by the observation of an antiferromagnetic ground state below T_Néel = 27 K in CpNi(dmit)˙, 18 K in CpNi(dsit)˙. Finally, CpNi(dmid)˙ crystallizes in the orthorhombic system, space group Pnma. Molecules organize into uniform chains through the stacking of the dmid moieties in a σ-type face-to-face overlap.