Synthesis and Reactions of Mono- and Dinuclear Ni(I) Thiolate Complexes

The dinuclear and mononuclear nickel(I) thiolates, [Ni(PPh3)(μ-SR)]2 (1a: R is 2,4,6-triisopropylphenyl (Tip), 1b: R is 1-adamantyl (Ad)), (DxpS)Ni(μ-SDxp)Ni(PPh3) (2) (Dxp is 2,6-dixylylphenyl), and Ni(SDmp)(PPh3) (3) (Dmp is 2,6-dimesitylphenyl), have been synthesized by the reaction of the nickel(I) amide Ni{N(SiMe3)2}(PPh3)2 with the corresponding thiols. The two nickel centers of 1a and 1b are equivalent, and are linked by two thiolato sulfurs and a Ni−Ni bond, whereas the two inequivalent nickels of 2 are connected by a SDxp sulfur, a η2/η3-xylyl group of the other SDxp ligand, and a Ni−Ni bond. A slightly bulkier m-terphenyl thiolate, SDmp, prevents its nickel complex from forming a Ni−Ni bond, and the mononuclear nickel(I) center of 3 is bound to PPh3 and SDmp through interactions with the sulfur and a η2-mesityl. The coordinatively unsaturated nickel(I) complex 3 is reactive, and the reaction of 3 with TEMPO generated diamagnetic Ni(SDmp)(PPh3)(O,N:η2-TEMPO) (4). N-Heterocyclic carbenes, 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe′) and 1,3-bis-(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes), also react with 3 to afford a dinuclear nickel(I) complex, [Ni(IMe′)(μ-SDmp)]2 (5), and a mononuclear nickel(I) complex, Ni(SDmp)(IMes) (6), respectively. The reaction of 3 with 1 equiv of tBuNC afforded the dinuclear complex [Ni(CNtBu)(μ-SDmp)]2 (7), whereas the analogous reaction with 1 equiv of CO resulted in a mixture of Ni(PPh3)2(CO)2 and Ni(CO)(SDmp)2(PPh3) (8).