Highly Fluxional [Y(C(SiH(CH3)2)3)3]: A DFT Characterization of Structure and NMR Spectra

The structure and NMR spectroscopic properties of [Y(C(SiH(CH3)(2))(3))(3)] are investigated with density functional theory calculations. The existence of a C-3 principal axis that was found experimentally is reproduced, but the calculations also find that the symmetry of the equilibrium structure of [Y(C(SiH(CH3)(2))(3))(3)] has to be reduced from the experimentally suggested C-3v or C-3h to C-3 in order to explain the observed SiH NMR chemical shifts. We show that the apparent mirror plane relating two agostic SiH(CH3)(2) groups on each ligand is caused by the rapid interchange of the position of the third ligand, which could only be observed at much lower temperatures than used previously in the experiments.