Synthesis and Reactivity Aspects of the Bis(dithiolene) Chalcogenide Series [W^IVQ(S₂C₂R₂)₂]^2-(Q = O, S, Se)

Abstract

An improved synthetic route to the previously reported dicarbonyl complexes [W(CO)2(S2C2R2)2] (R = Ph (1), Me (2)) has been developed via the thermal reaction of [W(CO)3(MeCN)3] and [Ni(S2C2R2)2] in dichloromethane (60−70%). Complexes 1 and 2 are shown to be useful synthetic precursors by means of carbonyl ligand displacement. Reactions of 1 with Et4NOH, Na2S, and Li2Se afford the previously unknown bis(dithiolene) series [WIVQ(S2C2Ph2)2]2- (Q = O (3), S (6), Se (7), 65−76%). Complex 2 and Et4NOH give [WIVO(S2C2Me2)2]2- (5, 68%). Members of the series manifest absorption spectra that are strongly dependent on Q and redox potentials for WIVQ/WVQ couples that are independent of Q. Reaction of 3 and 5 with MeI or EtI results in mono-S-alkylation as shown by the 1H NMR spectra of [WO(EtS2C2R2)(S2C2R2)]1-, which indicate a single stereoisomer with a diastereotopic methylene group. S-alkylation of 3 was further confirmed by the structure of the reaction product with MeI, [WO(MeS2C2Ph2)(S2C2Ph2)]1- (8, 65%), which reveals the exo stereoisomer with a pyramidal sulfur atom whose methyl carbon atom is displaced 1.27 Å from the chelate ring plane. Treatment of 3 with hard alkylating agents caused oxidation to [WVO(S2C2Ph2)2]-, independently prepared by reaction of 3 with iodine (78%). Sulfido complex 6 with soft alkylating agents such as MeI gave mixtures. Reaction of 6 with C7H7+ resulted in electron transfer rather than alkylation and the formation of binuclear [WV2(μ-S)2(S2C2Ph2)4]2- (11, 53%). No alkylated species were isolated from selenido complex 7; [W(S2C2Ph2)3] (13) was identified as a reaction product. Electrochemical data and X-ray structural results for 1, 2, 13 (trigonal prismatic), Et4N+ salts of 3, 5, 6 (square pyramidal), 8 (distorted square pyramidal), and 11 (distorted octahedral), and (PhCH2NEt3)[W(S2C2Ph2)3] (distorted trigonal prismatic) are presented.