title: Phosphorus-stabilized titanium carbene complexes: synthesis, reactivity and DFT studies.
abstract: The synthesis of two novel titanium carbene complexes from the bis(thiophosphinoyl)methanediide geminal dianion 1 (SCS(2-) ) is described. Dianion 1 reacts cleanly with 0.5 equivalents of [TiCl4 (thf)2 ] to afford the bis-carbene complex [(SCS)2 Ti] (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.
authors.affiliation: Laboratoire "Hétérochimie Fondamentale et Appliquée", Université Paul Sabatier, CNRS UMR 5069, 31062 Toulouse Cedex (France).
authors.forename: Mathieu
authors.initials: M
authors.lastname: Lafage
authors.forename: Hadrien
authors.initials: H
authors.lastname: Heuclin
authors.forename: Xavier-Frédéric
authors.initials: XF
authors.lastname: Le Goff
authors.forename: Nathalie
authors.initials: N
authors.lastname: Saffon-Merceron
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mézailles
keywords: carbene ligands; density functional calculations; geminal dianions; reaction mechanisms; titanium