Transition-metal complexes of di- and tri-phosphines derived from 1,1-bis(diphenylphosphinomethyl)ethene
摘要:
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-Ph2PCH=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-crystal X-ray diffraction. Marked differences are seen in the chelate-ring conformations of 1 b with an exocyclic C=C bond, 2b with an endocyclic C=C bond, and cis-[Mo(CO)4{Ph2P(CH2)3PPh2}] with no C=C bond. Proton, C-13 and P-31 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.
Rearrangements of the unsaturated ligand 1,1-bis(diphenylphosphinomethyl)ethene and its chalcogenides and group VI metal carbonyl complexes
摘要:
In contrast to the behaviour of other unsaturated organophosphines, treatment of the new ligand (Ph2PCH2)2C = CH2 with Ph2PH in the presence of KOBu(t) does not result in addition to the double bond; instead, an allylic rearrangement occurs to give cis and trans Ph2PCH = C(CH3)CH2PPh2 in a 3:7 ratio. In the case of (Ph2P(E)CH2)2C = CH2 [E = S, Se] only the trans isomer is obtained from this reaction, while under similar conditions (CO)4M(Ph2PCH2)2C = CH2 [M = Cr, Mo, W] yields only a cis product in which the two phosphorus atoms remain chelated. The products of these and related reactions are characterized by elemental analysis and C-13 and P-31 NMR spectroscopy.