Titanium Phosphinidene and Phosphide Moieties from Oxidative Phosphorylation and Desilylation

A unique entry into mononuclear titanium complexes bearing phosphinidene and phosphide ligand moieties is reported. Reaction of [K(crypt)][(PN)₂TiCl] (<b>1</b>, crypt = 2.2.2-cryptand) with [Na(OCP)] results in [K(crypt)][(PN)₂Ti(OCP)] (<b>2</b>) and such species can be oxidized to the derivative [(PN)₂Ti(OCP)] (<b>3</b>), both of which do not undergo decarbonylation. However, the reaction of <b>1</b> and [NaP(SiMe₃)₂] leads to an unprecedented Ti^III phosphinidene, [K(crypt)][(PN)₂Ti═PSiMe₃] (<b>4</b>), through an oxidative phosphorylation reaction. To promote the formation of a Ti≡P bond, complex <b>4</b> was treated with 0.5 equivalent XeF₂, resulting in an oxidative desilylation step forming a molecular titanium phosphide complex, [K(crypt)][(PN)₂Ti≡P] (<b>5</b>), which showed a characteristic downfield chemical shift at 1449.8 pmm in the ³¹P NMR spectrum. Complex <b>5</b> can be further functionalized to generate a terminal Ti^IV phosphinidene, [(PN)₂Ti═PSiMe₃] (<b>6</b>), and the latter can be independently accessed through oxidation of <b>4</b>. All new complexes were characterized structurally and as appropriate by multinuclear NMR, CW X-band EPR (for Ti^III), and HFEPR (for Ti^II) spectroscopies.