REACTIONS OF COORDINATED LIGANDS .57. SYNTHESIS, STRUCTURE AND INTERRELATIONSHIP OF 2-SIGMA-BUTADIENYL AND CATIONIC (1,2,3-ETA)-TRANS-BUTADIENYL-PLATINUM AND (1,2,3-ETA)-TRANS-BUTADIENYL-PALLADIUM COMPLEXES - CRYSTAL-STRUCTURES OF CIS-[PTCL(SIGMA-C(CH2)C(ET)=CH2)(DPPF)] AND [PT((1,2,3-ETA)-TRANS-CH2C(ET)C=CH2)(PPH3)2][PF6] [DPPF = 1,1'-BIS(DIPHENYLPHOSPHINO)FERROCENE]

Reaction of the platinum(o) complexes [Pt(C2H4) (PPh3)2], [Pt(C2H4) (dppf)] [dppf = 1,1-bis(diphenylphosphino)ferrocene], [Pt(cod)2] (cod = cyclocta-1,5 diene) and the palladium(o) complex [Pd(PPh3)4] with the 4-chlorobuta-1,2-dienes CH2=C=C(R)CH2Cl (R = Me or Et) affords trans or cis 2-sigma-butadienyl complexes of the general formula [MCI{sigma-C(CH2)C(R)=CH2}L2]; the structural identity of cis-[PtCl{sigma-C(CH2)C(Et)=CH2}(dppf)] was confirmed by single-crystal X-ray diffraction. Treatment of [Pt(C2H4)(PPh3)2] or [Pt(C2H4)(dppf)] with an excess of 2-chlorobuta-1,3-diene leads to the formation of the corresponding unsubstituted 2-sigma-butadienyl platinum complexes. Addition of thallium hexafluorophosphate to these 2-sigma-butadienyl complexes results in elimination of TlCl and formation in high yield of a range of cationic (1,2,3-eta)-trans-butadienyl complexes characterised by NMR spectroscopy, and in the case of [Pt{1,2,3-eta)-trans-CH2C(Et)C=CH2}(PPh3)2][PF6] by single crystal X-ray diffraction.