Transition metal complexes with sulfur ligands. 149 Mononuclear carbene dithiolate [Ni(NHX)('S2C')] complexes with HNX = HNPiPr(3) or HNSPh2 coligands ('S2C'(2-)=1,3-imidazolidinyl-N,N'-bis(2-benzenethiolate) (2-))

Cleavage reactions of the dinuclear [(Ni('S2C')](2)]. DMF ('S2C'(2-)= 1,3-i midazolidinyl-N,N'-bis(2-benzenethio- late)(2-)) with HNPiPr(3) or HNSPh2 y ielded the mononuclear complexes [Ni(NHPiPr(3))('S2C')] (1) and [Ni(NHSPh2) -('S2C')] (2) which have been completely characterized. The nickel-carbene- dithiolate [Ni('S2C')] moiety is one of the very rare complex fragments tha t are able to coordinate both HNPR3 or HNSR2. IR spectra and X-ray structur e determinations show that 1 and 2 exhibit intramolecular N-H . . .S(thiola te) hydrogen bonds. Geometric parameters and NMR spectroscopic data of 1 an d 2 are compatible with N-X single bonds and ylidic structures of the HNPiP r3 and HNSPh2 ligands. Comparison of Ni-N distances in diamagnetic and para magnetic [Ni(NHSPh2)1 complexes was rendered possible through the X-ray str ucture determination of the homoleptic [Ni(NHSPh2)(6)]Cl-2 (3) which formed as minor by-product in the synthesis of 2.