Transition-metal complexes of di- 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 1a, Mo 1b or W 1c) lead to cis-[M(CO)4{cis-Ph2PCH=C(Me)CH2PPh 2}] 2a-2c and to fac-single-crystal X-ray diffraction. Marked differences are seen in the chelate-ring conformations of 1b with an exocyclic C=C bond. 2b with an endocyclic C=C bond, and cis-[Mo(CO)4{Ph2P(CH2)3PPh 2}] with no C=C bond. Proton, 13C and 31P NMR data for 3b and 3c were obtained and a two-dimensional rotating frame nuclear Overhauser experiment was used to identify anisochronous methylene resonances in the proton NMR spectrum of 3b thus confirming a dependence of 3J(PH) on dihedral angle in these rigid polycyclic systems.