Addition reactions and rearrangements of 2,3-bis(diphenylphosphino)propene and its complexes with Group 6 metal carbonyls: routes to complexes of 1,2,3-tris(diphenylphosphino)propane

Abstract

The preparation of 2,3bis(diphenylphosphino)propene (1 ) and its Group 6 metal tetracarbonyl complexes are described. The attempted base-catalysed addition of PR,H to (1 ) results in rearrangement to trans-I ,2-bis(diphenylphosphino)propene ( 2 ) instead of the expected triphosphine. Under the same conditions the Group 6 metal carbonyl complexes of (1) can rearrange to complexes of the cis isomer of (2), but may also undergo the addition reaction to yield M (CO), complexes of the new ligand 1,2,3-tris(diphenyIphosphino)propane by adjustment of the reaction conditions. These on heating yield the corresponding M (CO), complexes. Proton, I3C, and ,'P n.m.r. spectral parameters of the new compounds are presented and are discussed in terms of metal-and backbone-mediated contributions and co-ordination chemical shifts.