Synthesis, structure, spectral properties and theoretical studies of two half-sandwich titanium-complexes with adamantoxy ligands
Abstract
Two novel half-sandwich Ti complexes, both incorporating two adamantoxy (OAd) ligands coordinated to their central atoms were synthesized. The complexes were characterized by H-1, C-13, F-19 NMR, El-MS and IR spectroscopy and by single-crystal X-ray diffraction.
In both complexes, the coordination environment is pseudo-tetrahedral and is assembled of two O-coordinated adamantoxy and one eta(5)-coordinated permethylcyclopentadienyl ligand. The fourth ligand in complex 1 is a methyl group coordinated through a regular sigma-bond, whereas in complex 2 the same.coordination site is occupied by the methyl group of the balancing (C6F5)(3)BMe- anion.
DFT computations complemented with NBO analyses of 2 have unveiled, that in addition to the electrostatic interactions occurring between the half-sandwich titanocene moiety and the anionic ligand, delocalization of one methyl C-H bond into the available acceptor orbital on the central atom takes place. AIM analyses of 2 have revealed the presence of a Bond Critical Point between the metal atom and the anionic methyl group.
These results prove foundation for the description of 2 as a zwitterionic complex coupled with a concurrent Ti...C-H agostic interaction in its molecule. The comparison of 2 with its analogous complex equipped with two Ot-Bu ligands instead of both OAd has suggested only a minor change in the extent of the agostic interaction, despite significant geometric differences between the two complexes. 2017 Elsevier B.V.
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