Electron‐Precise 1,3‐Bishomocubanes – A Combined Experimental and Theoretical Study

Abstract

A combined experimental and quantum-chemical study of a series of homometallic metallaheteroboranes [(Cp*M)2E6B2H2] (M = Rh or RuH; E = S or Se; Cp* = η5-C5Me5), which are analogues of 1,3-bishomocubane, is reported. The thermolysis of nido-[(Cp*Rh)2B3H7] (1) in the presence of S or Se powder in toluene yielded bishomocubane clusters [(Cp*Rh)2(μ-E)2(μ3-E)4B2H2], (3: E = S; 4: E = Se). In a similar fashion, the treatment of nido-[(Cp*RuH)2B3H7] (2) with S or Se powder in p-xylene yielded [(Cp*Ru)2(μ-E)2(μ3-E)4B2H2] (5: E = S; 6: E = Se) and [(Cp*Ru)2(μ3-Se)(μ4-Se)B3H5] (7). One of the noteworthy features of 3–6 is the presence of an electron-precise trichalcogenoborato ligand. All of the compounds have been characterized by mass spectrometry; IR spectroscopy; and 1H, 11B, and 13C NMR spectroscopy. The structures of 3, 4, 6, and 7 were established unequivocally by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for 3, 4, and 6 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO–LUMO gaps are consistent with the high stabilities of these complexes.