A Pentacoordinate Chlorotrimethylsilane Derivative: A very Polar Snapshot of a Nucleophilic Substitution and its Influence on 29 Si Solid State NMR Properties

The reaction of 1‐methyl‐2‐mercaptoimidazole (methimazole) with chloromethyldimethylchlorosilane (ClCH 2 )Si(CH 3 ) 2 Cl in the presence of triethylamine afforded the 1‐methylimidazol‐2‐ylthiomethyl‐substituted silane 1 . The pentacoordinate silicon atom of 1 is housed within an almost trigonal bipyramidal coordination sphere, i.e., the three equatorially situated C–Si–C angles sum up to 359.5(3)°. The axial situation of the still Si‐bound chlorine atom with its remarkably long Si‐Cl separation of 2.5123(3) Å and a trans ‐situated imidazolyl nitrogen donor constitute a very polar molecule, the resulting intermolecular interactions of which in the solid state were investigated crystallographically and by 29 Si CP/MAS NMR spectroscopy. Single crystals of 1 revealed significantly lower susceptibility towards temperature changes along the crystallographic a ‐axis, which is the axis along which chains of the polar molecules are aligned. Hence, the 29 Si NMR shielding tensor, experimentally determined by CP/MAS NMR spectroscopy, could only be simulated to a satisfactory extent when taking these intermolecular interactions into account.