Palladium complexes of a phosphorus ylide with two stabilizing groups: Synthesis, structure, and DFT study of the bonding modes

13 pages, 7 tables, 1 scheme, 5 figures, 2 equations, 1 chart.-- Supporting Information Available: http://pubs.acs.org.The phosphorus ylide ligand [Ph3PC(CO2Me)C(NPh)CO2Me] (L1) has been prepared and fully characterized by spectroscopic, crystallographic, and density functional theory (DFT) methods (B3LYP level). The reactivity of L1 toward several cationic PdII and PtII precursors, with two vacant coordination sites, has been studied. The reaction of [M(CX)(THF)2]ClO4 with L1 (1:1 molar ratio) gives [M(CX)(L1)]ClO4 [M = Pd, CX = C6H4CH2NMe2 (1), S-C6H4C(H)MeNMe2 (2), CH2-8-C9H6N (3), C6H4-2-NC5H4 (4), o-CH2C6H4P(o-tol)2 (6), η3-C3H5 (7); M = Pt, CX = o-CH2C6H4P(o-tol)2 (5); M(CX) = Pd(C6F5)(SC4H8) (8), PdCl2 (9)]. In complexes 1−9, the ligand L1 bonds systematically to the metal center through the iminic N and the carbonyl O of the stabilizing CO2Me group, as is evident from the NMR data and from the X-ray structure of 3. Ligand L1 can also be orthopalladated by reaction with Pd(OAc)2 and LiCl, giving the dinuclear derivative [Pd(μ-Cl)(C6H4-2-PPh2C(CO2Me)C(CO2Me)NPh)]2 (10). The X-ray crystal structure of 10 is also reported. In none of the prepared complexes 1−10 was the Cα atom found to be bonded to the metal center. DFT calculations and Bader analysis were performed on ylide L1 and complex 9 and its congeners in order to assess the preference of the six-membered N,O metallacycle over the four-membered C,N and five-membered C,O rings. The presence of two stabilizing groups at the ylidic C causes a reduction of its bonding capabilities. The increasing strength of the Pd−C, Pd−O, and Pd−N bonds along with other subtle effects are responsible for the relative stabilities of the different bonding modes.Funding by the Dirección General de Investigación Científica y Técnica (Spain; Projects CTQ2005- 01037, CTQ2005-09000-C02-01, CTQ2005-03141, and CTQ2005-06909-C02-01) is gratefully acknowledged. The authors thank Dr. Teodor Parella (Servei RMN, Universitat Autónoma de Barcelona) for his invaluable support in HOESY experiments. T.S. thanks the MECD (Spain) for a postdoctoral fellowship.Peer reviewe