Tetranuclear [Rh₄(μ-PyS₂)₂(diolefin)₄] Complexes as Building Blocks for New Inorganic Architectures: Synthesis of Coordination Polymers and Heteropolynuclear Complexes with Electrophilic d⁸ and d¹⁰ Metal Fragments

The reaction of [Rh4(μ-PyS2)2(cod)4] (PyS2 = 2,6-pyridinedithiolate, cod = 1,5-cyclooctadiene) with CF3SO3Me gave the cationic complex [Rh4(μ-PyS2Me)2(cod)4][CF3SO3]2 (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical conditions [Rh4(μ-PyS2)2(tfbb)4] (tfbb = tetrafluorobenzobarrelene) reacted with CF3SO3Me to give the mixed-ligand complex [Rh4(μ-PyS2)(μ-PyS2Me)(tfbb)4][CF3SO3] (2). The nucleophilicity of the bridging ligands in the complexes [Rh4(μ-PyS2)2(diolefin)4] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh3)(Me2CO)][ClO4] gave the hexanuclear complexes [(PPh3)2Au2Rh4(μ-PyS2)2(diolefin)4][ClO4]2 (diolefin = cod (3), tfbb (4)). The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh3)]+ fragments to the peripheral sulfur atoms in [Rh4(μ-PyS2)2(diolefin)4] along with their interaction with the neighbor rhodium atoms. Neutral coordination polymers of formula [ClMRh4(μ-PyS2)2(diolefin)4]n (M = Cu (5, 6), Au (7)) result from the self-assembly of alternating [Rh4(μ-PyS2)2(diolefin)4] ([Rh4]) blocks and MCl linkers. The formation of the infinite polymetallic chains was found to be chiroselective for M = Cu; one particular chain contains exclusively homochiral [Rh4] complexes. Cationic heterometallic coordination polymers of formula [MRh4(μ-PyS2)2(diolefin)4]n[BF4]n (M = Ag (8, 9), Cu (10, 11)) and [Rh5(μ-PyS2)2(diolefin)5]n[BF4]n (12, 13) result from the reactions of [Rh4] with [Cu(CH3CN)4]BF4, AgBF4, and [Rh(diolefin)(Me2CO)2]BF4, respectively. The heterometallic coordination polymers exhibit a weak electric conductivity in the solid state in the range (1.2−2.8) × 10-7 S cm-1.