TRANSITION-METAL COMPLEXES OF DI-PHOSPHINES AND TRI-PHOSPHINES DERIVED FROM 1,1-BIS(DIPHENYLPHOSPHINOMETHYL)ETHENE

Base-catalysed rearrangements of and/or additions of PPh2H to [M(CO)4{ (Ph2PCH2)2C=CH2}] (M = Cr la, Mo lb or W lc) lead to cis-[M(CO)4{cis-P h2PCH=C(Me)CH2PPh2}] 2a-2c and to fac-[M(CO)3{(Ph2PCH2)2C(Me)PPh2}] 3b , 3c. The structures of lb, 2b and 3b have been determined by single-c rystal X-ray diffraction. Marked differences are seen in the chelate-r ing conformations of 1 b with an exocyclic C=C bond, 2b with an endocy clic C=C bond, and cis-[Mo(CO)4{Ph2P(CH2)3PPh2}] with no C=C bond. Pro ton, C-13 and P-31 NMR data for 3b and 3c were obtained and a two-dime nsional rotating frame nuclear Overhauser experiment was used to ident ify anisochronous methylene resonances in the proton NMR spectrum of 3 b thus confirming a dependence of 3J(PH) on dihedral angle in these ri gid polycyclic systems.