Heterotrimetallic Assemblies with 1,2,4,5-Tetrakis(diphenylphosphino)benzene Bridges: Constructs for Controlling the Separation and Spatial Orientation of Redox-Active Metallodithiolene Groups

[Image: see text] Metallodithiolene complexes of the type [(R(2)C(2)S(2))M(η(2)-tpbz)] [R = CN, Ph, or p-anisyl; M = Ni(2+), Pd(2+), or Pt(2+); tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene] chelate transition metals ions to form trimetallic arrays [[(R(2)C(2)S(2))M(tpbz)](2)M′](n+), where M′ is square planar Pt(2+), 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 MP(2)/M′P(2) planes meet the tpbz P(2)C(6)P(2) mean plane at non-zero values gives rise to core topologies that appear “S-like” or herringbone-like for M′ = Pt(2+) or {ReBr(CO)}/{Re(CO)(2)}(+). Calculations reveal that departure from idealized D(2h)/D(2d)/C(2v) 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 (31)P nuclear magnetic resonance signal from approximately −14.5 ppm to approximately +41, approximately +20.5, and approximately +28.5 ppm for M′ = Pt(2+), Au(+), and {ReBr(CO)}/{Re(CO)(2)}(+), respectively. Electrochemically, dithiolene-based oxidations are observed for the R = Ph and M′ = Pt(2+) or Au(+) compounds but at potentials that are anodically shifted relative to charge-neutral [[(R(2)C(2)S(2))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 (R(2)C(2)S(2))M and M′ parts.