Transition-metal complexes of di- and tri-phosphines derived from 1,1-bis(diphenylphosphinomethyl)ethene

Abstract

Base-catalysed rearrangements of and/or additions of PPh₂H to [M(CO)₄{(Ph₂PCH₂)₂CCH₂}](M = Cr 1a, Mo 1b or W 1c) lead to cis-[M(CO)₄{cis-Ph₂PCHC(Me)CH₂PPh₂}]2a–2c and to fac-single-crystal X-ray diffraction. Marked differences are seen in the chelate-ring conformations of 1b with an exocyclic CC bond. 2b with an endocyclic CC bond, and cis-[Mo(CO)₄{Ph₂P(CH₂)₃PPh₂}] with no CC 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.