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Phosphorus and Arsenic Atom Transfer to Isocyanides to Form π-Backbonding Cyanophosphide and Cyanoarsenide Titanium Complexes

Abstract:

Decarbonylation along with E atom transfer from Na(OCE) (E=P, As) to an isocyanide coordinated to the tetrahedral TiII complex [(TptBu,Me)TiCl], yielded the [(TptBu,Me)Ti(η3-ECNAd)] species (Ad=1-adamantyl, TptBu,Me−=hydrotris(3-tert-butyl-5-methylpyrazol-1-yl)borate). In the case of E=P, the cyanophosphide ligand displays nucleophilic reactivity toward Al(CH3)3; moreover, its bent geometry hints to a reduced Ad−NCP3− resonance contributor. The analogous and rarer mono-substituted cyanoarsenide ligand, Ad−NCAs3−, shows the same unprecedented coordination mode but with shortening of the N=C bond. As opposed to TiII, VII fails to promote P atom transfer to AdNC, yielding instead [(TptBu,Me)V(OCP)(CNAd)]. Theoretical studies revealed the rare ECNAd moieties to be stabilized by π-backbonding interactions with the former TiII ion, and their assembly to most likely involve a concerted E atom transfer between Ti-bound OCE− to AdNC ligands when studying the reaction coordinate for E=P.