New silanediyl (silylene) complexes of ruthenium(0)

Abstract

The ruthenium(O)-silanediyl complexes (t-BuO) 2(HMPA)Si Ru(CO) 4 ( 6), Me 2(HMPA)SiRu(CO) 4 ( 7), Cl 2(HMPA)SiRu(CO) 4 ( 8), (C 6H 5) 2(HMPA)SiRu(CO) 4 ( 9) and HCl(HMPA)SiRu(CO) 4 ( 10) have been obtained from chlorosilanes and carbonylruthenate and characterized by 1H NMR, 13C NMR, 29Si (INEPT)NMR and IR spectroscopy. VT 1H NMR spectra in the range 22.0–100.1 °C show a rigid coordination of the HMPA donor to silicon in all cases. The rotation of the metal silicon bond is unrestricted down to −95.0 °C for 6. Furthermore the TBP framework of the ruthenium complexes is fluxional (Berry pseudorotation). A comparison of the force constants v(CO) of the CO stretching vibration trans to silicon allows the deduction of the donor capacity of the coordinated silanediyl ligands according to the sequence [(t-BuO) 2(HMPA)Si] > [Me 2(HMPA)Si] > [Cl 2(HMPA)Si]. This gradation correlates with the net charge densities at silicon calculated for the free silanediyls [(t-BuO) 2Si]>[Me 2Si]>[Cl 2Si]. A single crystal X-ray structure determination for 6 shows a RuSi bond distance of 2.414(1) Å and a partial covalent HMPA(O3)−Si donor bond of 1.735(3) Å (SiO1 1.641(3), SiO2 1.634(3) Å Σ=342.2°). A force field calculation for 6 reproduces the conformer found in the crystal as the global minimum of energy ( E tot=26.0 kcal mol −1).