Early transition-metal complexes of ?-keto-stabilized phosphorus ylides

Abstract

The complexation behaviour of the α-keto-stabilized phosphorus ylides Ph3PCHC(O)R (R = Ph, Me) towards the early transition metal ions titanium(IV), zirconium(IV) and niobium(III) was investigated. The complex [Ph3P­CHC(Ph)O]TiBr2(NMe2)2 was obtained from the reaction of the phosphonium bromide [Ph3PCH2C(O)Ph]Br with Ti(NMe2)4. The crystal structure of this complex is discussed. It is frequently observed that the complex formed from the ylide with the early transition metal is very unstable (not isolable) and stabilizes by migration of one NMe2 group from the starting metal complex to the ylide. Thus the reaction of Ph3PCHC(O)Me with Ti(NMe2)4 provides an access to the novel ylide Ph3PCHC(NMe2)­CH2. Niobium complexes of the α-keto-stabilized phosphorus ylides Ph3PCHC(O)R (R = Ph, Me) were obtained by reacting these ylides with NbCl3(TMSC≡CPh)·DME (TMS, trimethylsilyl; DME, dimethoxyethane) in CH2Cl2. A binuclear structure could be confirmed by X-ray crystal structure analysis. Copyright © 2000 John Wiley & Sons, Ltd.