Co-ordination of highly substituted alkenes to transition-metal complexes: preparation and crystal and molecular structures of the complexes [{RhCl(Ph2PO2CCHCMe2)}2] and [{RhCl(Ph2PO2CCHCHCHCHMe)}2]

Abstract

Reaction of Ph₂PCl with RR′CCR″C(X)OH in the presence of triethylamine produces Ph₂POC(X)CR″CRR′(X = O; R = R′= Me, R″= H; R = R″= H, R′= Me; R = R″= H, R′= CHCHMe; R = Ph, R′= H, R″= Me; X = H₂, R = R′= Me, R″= H) in high yield. These ligands react with [(RhClL₂)₂](L = C₂H₄ or cyclo-octene) to give high yields of [{RhCl(Ph₂POC(X)CR″CRR′)}₂] in which the ligands are bound through phosphorus and the double bond. The new compounds have been fully characterised by spectroscopic means, as well as by the crystal structures of [{RhCl(Ph₂PO₂CCHCMe₂)}₂] and [{RhCl(Ph₂PO₂CCHCHCHCH-Me)}₂]. Crystal data: for [{RhCl(Ph₂PO₂CCHCMe₂)}₂], monoclinic, a= 8.485(1), b= 28.070(3), c= 14.253(1)Å, β= 93.96(1)°, space group P2₁/n; for [{RhCl(Ph₂PO₂CCHCHCHCHMe)}₂], monoclinic, a= 17.372(2), b= 22.070(1), c= 9.986(2)Å, β= 104.51(1)°, space group P2₁/a. Both complexes contain dimeric structures with bridging chlorine atoms. Each rhodium atom is in an approximately square-planar configuration, and is bonded to two chlorine, one phosphorus atom, and one π-bonded CC double bond, the phosphorus and π system being part of a chelate ring structure. In [{RhCl(Ph₂PO₂CCHCHCHCHMe)}₂] the α,β unsaturated linkage is bonded to the rhodium only, the γ,δ double bond being free.