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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]

Heteroleptic bis(dithiolene)-phosphine iron and cobalt complexes [Fe(adt) 2 (PMe 3 )] ( 1 ) and [Co(adt) 2 (PMe 3 )] ( 2 ) (adt = para -anisyldithiolene) have been synthesized from corresponding bis(dithiolene) dimers [M 2 (adt) 4 ] 2 (M = Fe, Co) by reacting with excess PMe 3 in dichloromethane. Solid-state structures of 1 and 2 have been determined by single crystal X-ray crystallography, and the dithiolene ligands C S (≈1.72 Å) and C C (≈1.37 Å) bond distances reveal the coordination of π-radical monoanionic dithiolene (adt• 1− ) ligands to metal centers. Intense low energy ligand-to-ligand-charge transfer (LLCT) absorption band (743 nm for 1 ; 905 nm for 2 ) in UV–vis spectra and characteristic ν (C S•) (1168 cm −1 for 1 ; 1170 cm −1 for 2 ) in IR spectra affirms coordination of π-radical monoanionic dithiolenes to divalent metal ions. The cyclic voltammogram of 1 and 2 shows reversible oxidation and reduction waves attributed to M II → M III + e − (+0.52 V for 1 ; +0.29 V for 2 ) and adt• 1− + e − → adt 2− (−0.63 V for 1 ; −0.46 V for 2 ) redox process respectively. Comprehensive structural and spectroscopic investigations conclude, [M 2 III (adt 2− ) 2 (adt• 1- ) 2 ] → 2 [M II (adt• 1- ) 2 (PMe 3 )] intramolecular redox interplay during phosphine coordination induced cleavage of homoleptic bis(dithiolene) dimers to produce square pyramidal complexes. [ABSTRACT FROM AUTHOR]