Titanoxycarbene complexes of Ti(iv) with O- and N-donor ligands

Abstract

Heterobimetallic complexes of the general formula [{(OC)₅MC(Me)OTi(OiPr)₂}(µ-OiPr)]₂ with M = Cr (1), W (2) were synthesized by reacting (OC)₅MC(Me)OLi (M = Cr, W) with ClTi(OiPr)₃. X-Ray crystallography revealed dimeric molecular structures based on four-membered Ti₂O₂-rings for both compounds. Most intriguingly crystals of 1 virtually “shattered” upon cooling below −60 °C. Treatment of 1 and 2 with an excess of pyridine did not effect symmetric cleavage of the dimers, but afforded the unique rearrangement products [(OC)₅MC(Me)O]₂Ti(OiPr)₂(C₅H₅N)₂ with M = Cr (3) and W (4). The isomorphous structures, determined by means of X-ray diffraction, are only the second examples of an unrestrained titanium center coordinated by four OR and two N-donor ligands. Complexes 3 and 4 were also accessible from Cl₂Ti(OiPr)₂(C₅H₅N)₂ (5) and (OC)₅MC(Me)OLi. Owing to the inherent dynamic behaviour of all complexes, low-temperature NMR studies were undertaken. The formation of nanoparticles upon thermolysis of complex 2 lends support to the notion that the presented (or related) compounds could be useful as single source precursors for nano-sized mixed metal oxides or oxo nitrides.