Synthesis of the 13-Vertex Rhodacarborane Anion [4-(1,2:5,6-<i>η</i>-cod)-<i>c</i><i>loso</i>-4,1,6-RhC₂B₁₀H₁₂]^-and Its Reactions with Electrophiles

Abstract

Reduction of closo-1,2-C2B10H12, with sodium naphthalide in THF (THF = tetrahydrofuran), followed by addition of [Rh2(μ-Cl)2(cod)2] (cod = 1,2:5,6-η-cyclooctadiene) and [N(PPh3)2]Cl, affords the monoanionic 13-vertex rhodacarborane [N(PPh3)2][4-(cod)-closo-4,1,6-RhC2B10H12] (2). Treatment of compound 2 with sources of the cations {Cu(PPh3)}+, {Rh(PPh3)2}+, {Rh(cod)}+, and {RuCl(PPh3)2}+ yields, respectively, the neutral bimetallic species [4-(cod)-3,4,7-{Cu(PPh3)}-3,7-(μ-H)2-closo-4,1,6-RhC2B10H10], [4-(cod)-3,8-{Rh(PPh3)2}-3,8-(μ-H)2-closo-4,1,6-RhC2B10H10], [4-(cod)-3,8-{Rh(cod)}-3,8-(μ-H)2-closo-4,1,6-RhC2B10H10], and [4-(cod)-3,7,8-{RuCl(PPh3)2}-3,7,8-(μ-H)3-closo-4,1,6-RhC2B10H9], of which only the copper derivative has a metal−metal bond. In addition, the reaction of 2 with CF3SO3H results in protonation of the cyclooctadiene ligand with concomitant oxidation of the rhodium center, yielding the ostensibly 16-electron RhIII compound [4-(1−3-η3-C8H13)-closo-4,1,6-RhC2B10H12], which is stabilized by a C−H···Rh agostic interaction. Alternatively, treatment of 2 with hydride-abstracting reagents in the presence of THF results in substitution at a cage BH vertex, forming the zwitterionic complex [4-(cod)-7-{O(CH2)4}-closo-4,1,6-RhC2B10H11].