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The complexes [Pt(mdt)2] (4; mdt = methyl dithiolene, [Me2C2S2]n-), [Pt(adt)2] (5; adt = p-anisyldithiolene, [(MeO-p-C6H4)2C2S2]2-), and [Pd(adt)2] (10) have been prepared in yields of ≥ 90% via transmetalation reactions with the corresponding [R2Sn(S2C2R'2)] complexes (R = "Bu, R' = Me; R = Me, R' = C6H4-p-OMe, 3). Intrahgand C--S and C--CchclaIe bond lengths (~1.71 and ~1.40 A, respectively) obtained by X-ray crystallography show these compounds to be comprised of radical monoanions mdt*- and adt*- . The six-coordinate octahedral adducts [Pt(adt)2(dppe)J [6; dppe = 1,2-bis(diphenylphosphino)ethane], trans-[Pt(adt)2(PMe3)2] (8), and frans-[Pt(mdt)2(PMe3)2] (9) have also been prepared, and crystal structures reveal dithiolene ligands that are fully reduced ene-l,2-dithiolates (C--S and C--Cchelate = ~1.77 and 1.35 A, respectively). Reduction of the dithiolene ligand thus occurs to accommodate the +IV oxidation state typical of octahedral sixcoordinate platinum. The cyclic voltammogram of 5 shows twofully reversible reductions at --0.11 and --0.84 V in CH2C12 (vs Ag/AgCl), attributed to successive (adt*- + e- → adt2-) processes, and a reversible oxidation at +1.01 V. The cyclic voltammogram of 9 shows two reversible oxidations at +0.38 and +0.86 V, which are assigned as successive (adt2- &#8594 adt*- + e-) oxidations. Consistent with their formulation as having fully reduced dithiolene ligands, the UV--vis spectra for 6, 8, and 9 show no low-energy absorptions below 700 nm, and the S K-edge XAS spectra of 6 and 8 show dithiolene sulfur that is reduced relative to that in 5. The introduction of PMe3 to 10 did not produce the palladium analogue of 8 but rather [Pd(adt)(PMe3)2] (11) . The reaction of [PdCl2(PPh3)2] with Li2(mdt) produced a mixture of [Pd(mdt)(PPh3)2] (12, 20%) and [(Ph3P)Pd(p-l,2-mdt- S,S':S)2Pd(PPh3)] (13, 28%), with the latter having C2 symmetry with a Pd2S2 core structure folded along the S…S axis. [ABSTRACT FROM AUTHOR]

A new, high yield synthesis of [Ni(S[sub2]C[sub2]Me[sub2])[sub2]] (3) is described using 4,5-dimethyl-1 ,3-dithiol-2-one, Me[sub2]C[sub2]S[sub2]C==O (1), as dithiolene ligand precursor. Reaction of (Me[sub2]C[sub2]S[sub2])Sn[supn]Bu[sub2], 2, with WCI[sub6] produces tris(dithiolene) [W(S[sub2]C[sub2]Me[sub2])[sub3]] (6) and demonstrates the potential synthetic utility of this compound in metallodithiolene synthesis. The series of compounds [W(S[sub2]C[sub2]Me[sub2])[subx](CO)[sub6-2x]] (x = 1 -3), obtained as a mixture via the reaction of [Ni(S[sub2]C[sub2]Me[sub2])[sub2]] with [W(MeCN)[sub3](CO)[sub3]], has been characterized structurally. A trigonal prismatic geometry is observed for [W(S[sub2]C[sub2]Me[sub2])(CO)[sub4]) (4) and confirmed by a DFT geometry optimization to be lower in energy than an octahedron by 5.1 kcal/mol. The tris(dithiolene) compound [W(S[sub2]C[sub2]Me[sub2])[sub3]] crystallizes in disordered fashion upon a 2-fold axis in C2/c, a different space group than that observed for its molybdenum homologue (P¯1), which is attributed to a slightly smaller chelate fold angle, α, in the former. The reactivity of 4 and [W(S[sub2]C[sub2]Me[sub2])[sub2](CO)[sub2]] (5) toward PMe[sub3] has been examined. Compound 4 yields only [W(S[sub2]C[sub2]Me[sub2])(CO)[sub2](PMe[sub3])[sub2]] (7), while 5 produces either [W(S[sub2]C[sub2]Me[sub2])[sub2](CO)(PMe[sub3])] (8) or [W(S[sub2]C[sub2]Me[sub2])[sub2](PMe[sub3])[sub2]] (9) depending upon reaction conditions. Crystallographic characterization of 5, 8, and 9 reveals a trend toward greater reduction of the dithiolene ligand (i.e., more ene1 ,2-dithiolate character) across the series, as manifested by C-C and C-S bond lengths. These structural data indicate a profound effect exerted by the π-acidic CO ligands upon the apparent state of reduction of the dithiolene ligand in compounds with ostensibly the same oxidation state. [ABSTRACT FROM AUTHOR]