Transition metal–carbon bonds. Part XXXIII. Internal metallations of secondary and tertiary carbon atoms by platinum(II) and palladium(II)

Abstract

The internally metallated complexes [Pt₂Cl₂(P–C)₂][(P′–C)= CH(CH₃)C₆H₄PBu^t₂ or (P″–C)= C(CH₃)₂C₆H₄PBu^t₂] are readily prepared by treating [PtCl₂(PhCN)₂] with L[L′= PBu^t₂(o-ethylphenyl) or L″= PBu^t₂(o-isopropylphenyl)]. Treatment of Na₂PdCl₄ with L′ yields trans-[PdCl₂L′₂], which on heating produces [Pd₂Cl₂(P′–C)₂]. The metallation occurs at the α-carbon atom of the ligand, L, in all cases. The chelate ligand (P′–C) contains an asymmetric carbon atom. The complexes [M₂Cl₂(P–C)₂](M = Pd or Pt) undergo bridge-splitting reactions with various ligands (e.g. pyridine, PPh₃, PMeBu^tPh, etc.) giving mononuclear species. Treatment of Na₂PdCl₄ with L″ gives [Pd₂Cl₄L″₂] which does not undergo internal metallation. ¹H, ¹³C, and ³¹P N.m.r. data are given and discussed.