Redox-active metallodithiolene groups separated by insulating tetraphosphinobenzene spacers

Compounds of the type [(S2C2R2)M(μ-tpbz)M(S2C2R2)] (R = CN, Me, Ph, p-anisyl; M = Ni, Pd, Pt; tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene) have been prepared by transmetalation with [(S2C2R2)SnR′2] reagents, by direct displacement of dithiolene ligand from [M(S2C2R2)2] with 0.5 equiv of tpbz, or by salt metathesis using Na2[S2C2(CN)2] in conjunction with X2M(μ-tpbz)MX2 (X = halide). X-ray crystallography reveals a range of topologies (undulating, chair, bowed) for the (S2C2)M(P2C6P2)M(S2C2) core. The [(S2C2R2)M(μ-tpbz)M(S2C2R2)] (R = Me, Ph, p-anisyl) compounds support reversible or quasireversible oxidations corresponding to concurrent oxidation of the dithiolene terminal ligands from ene-1,2-dithiolates to radical monoanions, forming [(−S•SC2R2)M(μ-tpbz)M(−S•SC2R2)]2+. The R = Ph and p-anisyl compounds support a second, reversible oxidation of the dithiolene ligands to their α-dithione form. In contrast, [(S2C2(CN)2)Ni(tpbz)Ni(S2C2(CN)2)] sustains only reversible, metal-centered reductions. Spectroscopic examination of [(−S•SC2(p-anisyl)2)Ni(μ-tpbz)Ni(−S•SC2(p-anisyl)2)]2+ by EPR reveals a near degenerate singlet–triplet ground state, with spectral simulation revealing a remarkably small dipolar coupling constant of 18 × 10–4 cm–1 that is representative of an interspin distance of 11.3 Å. This weak interaction is mediated by the rigid tpbz ligand, whose capacity to electronically insulate is an essential quality in the development of molecular-based spintronic devices

Heterotrimetallic assemblies with 1,2,4,5-tetrakis(diphenylphosphino)benzene bridges: Constructs for controlling the separation and spatial orientation of redox-active metallodithiolene groups

Metallodithiolene complexes of the type (R2C2S2)M($\eta$2-tpbz) R = CN, Ph, or p-anisyl; M = Ni2+, Pd2+, or Pt2+; tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene chelate transition metals ions to form trimetallic arrays (R2C2S2)M(tpbz)]2M']n+, where M' is square planar Pt2+, tetrahedral Cu+, Ag+, or Au+, or octahedral {ReBr(CO)}/{Re(CO)2}+. Forcing conditions (190 °C reflux in decalin, 72 h) are demanded for the Re+ compounds. With third-row metals at the nexus, the compounds are stable to air. Twelve members of the set have been characterized by X-ray diffraction and reveal dithiolene centroid-centroid distances ranging from 22.4 to 24.0 Å. Folding around each tpbz intrachelate P···P axis such that the MP2/M'P2 planes meet the tpbz P2C6P2 mean plane at non-zero values gives rise to core topologies that appear ``S-like'' or herringbone-like for M' = Pt2+ or {ReBr(CO)}/{Re(CO)2}+. Calculations reveal that departure from idealized D2h/D2d/C2v symmetries is induced by steric crowding between Ph groups and that dynamic, fluxional behavior is pertinent to the solution phase because multiple, lower-symmetry minima of comparable energy exist. Spectroscopically, the formation of the trimetallic arrays is marked by a shift of the open end 31P nuclear magnetic resonance signal from approximately -14.5 ppm to approximately +41, approximately +20.5, and approximately +28.5 ppm for M' = Pt2+, Au+, and {ReBr(CO)}/{Re(CO)2}+, respectively. Electrochemically, dithiolene-based oxidations are observed for the R = Ph and M' = Pt2+ or Au+ compounds but at potentials that are anodically shifted relative to charge-neutral (R2C2S2)M]2(μ-tpbz)]. The compounds reported clarify the possibilities for the synthesis of assemblies in which weakly coupled spins may be created in their modular (R2C2S2)M and M' parts

Open-ended metallodithiolene complexes with the 1,2,4,5-tetrakis(diphenylphosphino)benzene ligand: modular building elements for the synthesis of multimetal complexes

Open-ended, singly metalated dithiolene complexes with 1,2,4,5-tetrakis(diphenylphosphino)benzene (tpbz) are prepared either by ligand transfer to [Cl2M(tpbz)] from (R2C2S2)SnR′2 (R = CN, R′ = Me; R = Me, R′ = nBu) or by a direct reaction between tpbz and [M(S2C2R2)2] (M = Ni, Pd, Pt; R = Ph, p-anisyl) in a 1:1 ratio. The formation of dimetallic [(R2C2S2)M(tpbz)M(S2C2R2)] attends these syntheses in modest amounts, but the open-ended compounds are readily separated by silica chromatography. As affirmed by X-ray crystallographic characterization of numerous members of the set, the [(R2C2S2)M(tpbz)] compounds show dithiolene ligands in their fully reduced ene-1,2-dithiolate form conjoined with divalent Group 10 ions. Minor amounts of octahedral [(Ph2C2S2)2PtIV(tpbz)], a presumed intermediate, are isolated from the preparation of [(Ph2C2S2)PtII(tpbz)]. Heterodimetallic [(Ph2C2S2)Pt(tpbz)Ni(S2C2Me2)] is prepared from [(Ph2C2S2)PtII(tpbz)]; its cyclic voltammogram, upon anodic scanning, shows two pairs of closely spaced, but resolved, 1e– oxidations corresponding first to [R2C2S22–] – 1e– → [R2C2S•S–] and then to [R2C2S•S–] – 1e– → [R2(C═S)2]. The open diphosphine of [(R2C2S2)M(tpbz)] can be oxidized to afford open-ended [(R2C2S2)M(tpbzE2)] (E = O, S). Synthesis of the octahedral [(dppbO2)3Ni][I3]2 [dppbO2 = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(R2C2S2)M(tpbzE2)] is moderated enough that three could be accommodated as ligands around a metal ion

Redox-Active Metallodithiolene Groups Separated by Insulating Tetraphosphinobenzene Spacers

Compounds of the type [(S₂C₂R₂)­M­(μ-tpbz)­M­(S₂C₂R₂)] (R = CN, Me, Ph, <i>p</i>-anisyl; M = Ni, Pd, Pt; tpbz = 1,2,4,5-tetrakis­(diphenylphosphino)­benzene) have been prepared by transmetalation with [(S₂C₂R₂)­SnR′₂] reagents, by direct displacement of dithiolene ligand from [M­(S₂C₂R₂)₂] with 0.5 equiv of tpbz, or by salt metathesis using Na₂[S₂C₂(CN)₂] in conjunction with X₂M­(μ-tpbz)­MX₂ (X = halide). X-ray crystallography reveals a range of topologies (undulating, chair, bowed) for the (S₂C₂)­M­(P₂C₆P₂)­M­(S₂C₂) core. The [(S₂C₂R₂)­M­(μ-tpbz)­M­(S₂C₂R₂)] (R = Me, Ph, <i>p</i>-anisyl) compounds support reversible or quasireversible oxidations corresponding to concurrent oxidation of the dithiolene terminal ligands from ene-1,2-dithiolates to radical monoanions, forming [(⁻S^<b>•</b>SC₂R₂)­M­(μ-tpbz)­M­(⁻S^<b>•</b>SC₂R₂)]²⁺. The R = Ph and <i>p</i>-anisyl compounds support a second, reversible oxidation of the dithiolene ligands to their α-dithione form. In contrast, [(S₂C₂(CN)₂)­Ni­(tpbz)­Ni­(S₂C₂(CN)₂)] sustains only reversible, metal-centered reductions. Spectroscopic examination of [(⁻S^<b>•</b>SC₂(<i>p</i>-anisyl)₂)­Ni­(μ-tpbz)­Ni­(⁻S^<b>•</b>SC₂(<i>p</i>-anisyl)₂)]²⁺ by EPR reveals a near degenerate singlet–triplet ground state, with spectral simulation revealing a remarkably small dipolar coupling constant of 18 × 10^–4 cm^–1 that is representative of an interspin distance of 11.3 Å. This weak interaction is mediated by the rigid tpbz ligand, whose capacity to electronically insulate is an essential quality in the development of molecular-based spintronic devices