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Pentacoordinate Silicon Complexes with N-(2-pyridylmethyl)­salicylamide as a Dianionic (ONN′) Tridentate Chelator


  • Dedicated to Professor Klaus Jurkschat on the Occasion of His 60th Birthday

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The title compound, N-(2-pyridylmethyl)salicylamide (1), was synthesized by ester aminolysis of methyl salicylate and 2-picolylamine. In the presence of triethylamine as a supporting base, the salicylamide moiety reacts with the organodichlorosilanes RR′SiCl2 to form the desired six-membered heterocycles of the type RR′Si–O–(o-C6H4)–C(=O)N(pic), with pic being the 2-pyridylmethyl (i.e., 2-picolyl) moiety and RR′ = Me, Me (2a); Me, Ph (2b); Ph, Ph (2c); Bn, Bn (2d); All, Ph (2e) and Ph, H (2f). Despite the absence of notable ring strain release Lewis acidity (i.e., only a six-membered chelate is formed by the dianion, and smaller rings are not present in the compound), the poor electron withdrawal from silicon by its C– or H– substituents and the flexible methylene bridge between the salicylamide and the pyridine moiety, the pyridine N donor atom furnishes pentacoordinate silicon coordination spheres in all of these compounds 2a2f. The coordination number of the silicon atom was confirmed by single-crystal X-ray diffraction analysis for the solid state and by 29Si NMR spectroscopy for the solution state.