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 2,3-bis(diphenylphosphino)propene (1) and its Group 6 metal tetracarbonyl complexes are described. The attempted base-catalysed addition of PR₂H to (1) results in rearrangement to trans-1,2-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)₄ complexes of the new ligand 1,2,3-tris(diphenylphosphino)propane by adjustment of the reaction conditions. These on heating yield the corresponding M(CO)₃ complexes. Proton, ¹³C, and ³¹P 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.