Phosphorus‐Stabilized Titanium Carbene Complexes: Synthesis, Reactivity and DFT Studies

The synthesis of two novel titanium carbene complexes from the bis(thiophosphinoyl)methanediide geminal dianion 1 (SCS2−) is described. Dianion 1 reacts cleanly with 0.5 equivalents of [TiCl4(thf)2] to afford the bis-carbene complex [(SCS)2Ti] (2) in 86 % yield. The mono-carbene complex [(SCS)TiCl2(thf)] (3) can also be obtained by using an excess of [TiCl4(thf)2]. The structures of 2 and 3 are confirmed by X-ray crystallography. A strong nucleophilic reactivity towards various electrophiles (ketones and aldehydes) is observed. The reaction of 3 with N,N′-dicyclohexylcarbodiimide (DCC) and phenyl isocyanate leads to the formation of two novel diphosphinoketenimines 8 a and 8 b. The bis-titanium guanidinate complex 9 is trapped as the by-product of the reaction with DCC. The X-ray crystal structures of 8 a and 9 are presented. The mechanism of the reaction between complex 3 and DCC is rationalized by DFT studies.