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 [(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 2 h / D 2 d / C 2 v 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.