Stereospezifische umlagerung von P-halogensubstituierten phosphorylid-komplexen in phosphan-komplexe

摘要: Abstract At low temperatures the benzylidene complexes (C))5WC(R)H (1) [R = C6H5 (a), C6H4Me-p (b)] add PPhCl2 at carbene carbon to form ylide (CO)5WC(R)HPPhCl2 (3). These isomerize room temperature give phosphine (CO)5WP(Ph)ClC(R)(H)Cl (4). The rearrangement is stereospecific with only one diastereomer, (RS,SR)-4a and (RS,SR)-4b, respectively, being formed. In a slower succeeding reaction this diastereomer epimerizes until an equilibrium attained [e.g. (RS,SR)4a/(RR,SS)-4a ca. 3:2]. structure of complex (RS,SR)-4b has been established by X-ray analysis. epimerization accelerated free chloride. However, P-bound, rather than C-bound bromide in (CO)5WP(Ph)BrC(Ph)(H)Br (7) may be exchanged Isomerization 3a 4a presence excess leads partial substitution migrating (in C-bound) chloride giving (CO)5WP(Ph)ClC(PH)(H)Br obtained via addition PPh2Cl, PCl3, PPhBr2, PPh2Br, PBr3 PPh(Me)Cl 1a also rearrange corresponding complexes. rates isomerization (RS,SR)- (RR,SS)-(CO)5WC(Ph)HPPh(Me)Cl into RR,SS)(CO)5WPPh(Me)C(Ph)(H)Cl differ (RS,SR)-diastereomer rearranging faster. stereochemical results studies are discussed on basis intramolecular C,P-migration (CO)5W, accompanied dissociation halide from phosphorus atom. proposed proceed associative mechanism intermediate formation pentacoordinated phosphorus.