Different Coordination Modes of the Polyfunctional Ylide Ph3P=C(H)C(O)CH2C(O)OEt: C‐ vs. O,O′‐Bonding in PdII, PtII and AuI Complexes

Treatment of the polyfunctional ylide Ph3P=C(H)C(O)CH2COOEt (1) with the solvated complexes [M(C∧X)(THF)2]ClO4 gave the O,O′ derivatives [M(C∧X)(Ph3PCH2C(O)=C(H)−C(=O)OEt‐κ‐O,O′]ClO4 [M(C∧X) = Pd(C6H4CH2NMe2) (2), Pd(CH2C9H6N) (3), Pd(NC5H4‐2‐C6H4) (4), Pd(NC13H8) (5), Pd[(S)−C6H4C(H)MeNMe2] (6), Pt[o‐CH2C6H4P(o‐tol)2] (7), Pd[o‐CH2C6H4P(o‐tol)2] (8), and Pd(C6F5)(SC4H8) (9)]. During the reaction, one proton of the methylene unit is transferred to the ylidic carbon, which is transformed into a phosphonium group generating the zwitterion [Ph3PCH2C(O)=C(H)−C(=O)OEt], which coordinates to the metal center as an O,O′‐chelating ligand. Treatment of 1 with [AuCl(SC4H8)] or [Au(PPh3)(OCMe2)]ClO4 gave [AuCl{C(H)(PPh3)C(O)CH2COOEt}] (10) or [Au{C(H)(PPh3)C(O)CH2COOEt}(PPh3)]ClO4 (11), in which the ylide is C‐bonded. The X‐ray crystal structures of complexes 2a, 9 and 10 have been determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)