<i>Aufbau</i> Approach to Multimetallic Ensembles Based on\nTetrathiooxalate:  [Cp*₄Rh₄(C₂S₄)₂]²⁺, [Cp*₃Rh₂Ru(C₂S₄)]⁺,\nand [Cp*₆Rh₆(C₂S₄)₂]⁴⁺

Abstract

Experiments aimed at the characterization of new coordination modes for tetrathiooxalate\n(TTO) are described. Cyclic voltammetric (CV) measurements on Cp*₂Rh₂(C₂S₄) (<b>1</b>) revealed\nan irreversible oxidation as part of an ECE process that results in the chemically reversible\ndimerization of <b>1</b>⁺. Treatment of <b>1</b> with CpFe[C₅H₄C(O)Me]BF₄ followed by anion exchange\ngave [Cp*₄Rh₄(C₂S₄)₂](BPh₄)₂, the dication of which consists of a dimer of <b>1</b>⁺ linked through\ntwo pairs of Rh−S bonds. A second new bonding mode for TTO was generated by treatment\nof <b>1</b> with [Cp*Ru(MeCN)₃]PF₆ to give [Cp*₃Rh₂Ru(C₂S₄)]⁺ (<b>3</b>) wherein Cp*Ru⁺ is η⁵-bonded\nto one RhS₂C₂ ring. A third new bonding mode for TTO is illustrated by [Cp*₆Rh₆(C₂S₄)₂]⁴⁺,\nformed by the reaction of Cp*Rh(MeCN)₃²⁺ and <b>1</b>. The structure can be viewed as a dimer\nof <b>3</b>, except that there are no M−M bonds: the Cp*Rh²⁺ fragments are bonded via an η⁴-interaction to RhS₂C₂ rings. Furthermore, the [Cp*₃Rh₃(C₂S₄)]²⁺ subunits, which are\notherwise isoelectronic with <b>3</b>, dimerize, such that all eight sulfur atoms are triply bridging.