Ligand Exchange Mechanism in Novel Hexacoordinate Silicon Complexes

Novel neutral hexacoordinate silicon complexes 1-6 were prepared and the mechanism of ligand exchange studied. Two simultaneous nondissociative N-methyl exchange processes were found. On the basis of persistence of ¹J_Si-F and ²J_N-Si-H in 5 and 1a, respectively, dissociative exchange was ruled out. The two consecutive processes were assigned (in order of increasing activation energy) to (X, Cl)- and (O, O)-1,2-shifts, based on the low-temperature NOESY and Saturation Transfer spectrum. The first observation of ¹⁵N¹H coupling across the Si-N coordinative bond is reported.