Paramagnetic (1,3‐Diborolyl)ruthenium Triple‐Decker Complexes and Transformation into Diamagnetic Complexes Having Bridging 1,3‐Diborafulvene Ligands

The paramagnetic triple-decker complexes [(Cp*Ru) 2 {μ-(CMe) 3 (BCl)(BMe))] (3b) and [(Cp*Ru) 2 {μ-(CMe) 3 (BCl) 2 }] (3c) are formed by refluxing a mixture of [Cp*RuCl] 4 and pentamethyl-2,3-dihydro-1,3-diborole in thf. In CH 2 Cl 2 under air complex 3b slowly looses a hydrogen atom with formation of the diamagnetic triple-decker [(Cp*Ru) 2 {μ-η 5 :η 6 -(CMe) 3 -(BCl)(BCH 2 )}] (4b) with the unsymmetrical dihydrodiborafulvene derivative in a bridging position. The analogous complex [(Cp*Ru) 2 {μ.η 5 :η 6 -(CMe) 3 (BMe)-(BCH 2 )}] (4a) is obtained by interaction of HCl with the triple-decker [(Cp*Ru) 2 -{μ-(CMe) 3 (BMe) 2 }] (3a). According to calculations, complexes 4a and 4b have an almost non-distorted triple-decker arrangement with a strong bending of the B=CH 2 group toward one of the Ru atoms. For the formation of 3b and 3c the chloro-containing sandwich complexes [Cp*Ru{η 5 -(CMe) 3 -(BCl)(BR 1 )}] (2b,c; R 1 = Me, Cl) are proposed as intermediates. The constitutions of the complexes are derived from NMR, MS and DFT data, and the molecular structure of 3b is confirmed by an X-ray diffraction analysis.