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

An improved synthetic route to the previously reported dicarbonyl complexes [W(CO) 2 (S 2 C 2 R 2 ) 2 ] (R = Ph ( 1 ), Me ( 2 )) has been developed via the thermal reaction of [W(CO) 3 (MeCN) 3 ] and [Ni(S 2 C 2 R 2 ) 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 Et 4 NOH, Na 2 S, and Li 2 Se afford the previously unknown bis(dithiolene) series [W IV Q(S 2 C 2 Ph 2 ) 2 ] 2 - (Q = O ( 3 ), S ( 6 ), Se ( 7 ), 65−76%). Complex 2 and Et 4 NOH give [W IV O(S 2 C 2 Me 2 ) 2 ] 2 - ( 5, 68%). Members of the series manifest absorption spectra that are strongly dependent on Q and redox potentials for W IV Q/W V Q couples that are independent of Q. Reaction of 3 and 5 with MeI or EtI results in mono-S-alkylation as shown by the 1 H NMR spectra of [WO(EtS 2 C 2 R 2 )(S 2 C 2 R 2 )] 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(MeS 2 C 2 Ph 2 )(S 2 C 2 Ph 2 )] 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 [W V O(S 2 C 2 Ph 2 ) 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 C 7 H 7 + resulted in electron transfer rather than alkylation and the formation of binuclear [W V 2 (μ-S) 2 (S 2 C 2 Ph 2 ) 4 ] 2 - ( 11, 53%). No alkylated species were isolated from selenido complex 7; [W(S 2 C 2 Ph 2 ) 3 ] ( 13 ) was identified as a reaction product. Electrochemical data and X-ray structural results for 1, 2, 13 (trigonal prismatic), Et 4 N + salts of 3, 5, 6 (square pyramidal), 8 (distorted square pyramidal), and 11 (distorted octahedral), and (PhCH 2 NEt 3 )[W(S 2 C 2 Ph 2 ) 3 ] (distorted trigonal prismatic) are presented.