Revising the chemistry of κ2-dppe-closo-RuC2B9H11 fragment: Synthesis of novel diamagnetic complexes and its transformations

Abstract

Anovel facile way of synthesis of closo-ruthenacarboranes with chelate 1,2-bis(diphenylphosphino)ethane (dppe) with high yields was proposed. It was found that the interaction of the three-bridged 5,6,10-{Cl(Ph3P)2Ru}-[5,6,10-(μ-H)3-10-H-exo-nido-7,8-C2B9H10] (1) with dppe in acetonitrile or CH2Cl2/acetonitrile mixture leads to the formation of novel diamagnetic ruthenacarborane cluster 3-СNMe-3,3-[κ2-dppe]-closo-3,1,2-RuC2B9H11 (2) along with some amount of ionic compound [trans-(CH3CN)RuCl(dppe)2]+[C2B9H12]− (3) which may be also converted to 2 increasing its total yield. The reaction of 2 bearing divalent ruthenium with carbon tetrachloride or HCl gives the known 17-electron paramagnetic complex 3-Сl-3,3-[κ2-dppe]-closo-3,1,2-RuC2B9H11 (4)..The detailed investigation of the previously described method of synthesis of 4 from 3-H-3Cl-3,3-(PPh3)2-closo-3,1,2-RuC2B9H11 (5) allowed us to characterize the forming by-products as 3-PPh3-3,3,8-(Ph2P(CH2)2PPh-μ-(C6[H4-о)-closo-3,1,2-RuC2B9]H10 (6) and 3-[κ1-dppe]-3,3-[κ2-dppe]-closo-3,1,2-RuC2B9H11 (7). The obtained ruthenacarborane clusters undergo reversible Ru(II)/Ru(III) transition. It was shown that the complexes 2, 4 and 6 show good activity as catalysts for Atom Transfer Radical Polymerization of methyl methacrylate.