Distorted square planar nickel(II) carbonyl complexes containing terminal thiolate/selenolate ligands

Abstract

Distorted square planar [Ni(CO)(SR)n(SePh)3 − n]− (n = 0 (1), 3 (2), 1 (3) or 2 (4); R = Ph or C4H3S) complexes, were prepared by unique Cp−/PhS− (PhSe−) exchange reactions and oxidative addition. (SC4H3S)2, [NiCp(CO)]2 and 2 equivalents of fac-[N(PPh3)2][Fe(CO)3(SC4H3S)3] in thf led to the isolation of [N(PPh3)2][Ni(CO)(SC4H3S)3] and [FeCp(CO)2(SC4H3S)]. Complex [Ni0(CO)3(SePh)]− was obtained upon chemical reduction of complex [NiII(CO)(SePh)3]− with [BH4]− under a CO atmosphere in thf. [NiII(CO)(SePh)3]− was reobtained upon oxidative addition of diphenyl diselenide and benzeneselenol to [Ni0(CO)3(SePh)]− in thf. The mixed-chalcogenolate nickel(II) carbonyl complexes [Ni(CO)(SPh)n(SePh)3 − n]− (n = 1 or 2) were prepared by PhSe−/PhS− ligand exchange reaction and oxidative addition of diphenyl disulfide to [Ni(CO)3(SePh)]− individually. Complexes [NiII(CO)(SePh)3]−, [NiII(SC5H4N)3]−, [Ni0(CO)3(SC5H4N)]− and [Ni0(CO)3(SePh)]− are chemically interconvertible at ambient temperature. Coordinative addition of the metalloanion [Mn(CO)5]− ([Fe(CO)4(SePh)]−) to complex [Ni(CO)(SePh)3]− and subsequent redox under a CO atmosphere led to formation of cis-[Mn(CO)4(SePh)2]− (fac-[Fe(CO)3(SePh)3]−) and [Ni0(CO)3(SePh)]−. Nickel(II)/nickel(0) carbonyl thiolate complexes are more unstable thermally than the corresponding carbonyl selenolate complexes. Isotopic shift experiments demonstrate the lability of carbonyl ligand(s) of complexes 1–4 and [Ni(CO)3(SePh)]− species. The vibrational spectroscopy of the NiII(CO) fragment (ν(CO) ranges from 2023 to 2043 cm−1) found in 1–4 may be regarded as a spectroscopic reference for the carbonyl binding site of [NiFe] hydrogenases and CO dehydrogenase.