Alkyl and hydrido phenoxo complexes of nickel(II), palladium(II), and platinum(II). Hydrido amido complexes of palladium

The compound trans-NiHCl(PBz{sub 3}){sub 2}, where Bz=CH{sub 2}C{sub 6}H{sub 5}, has been synthesized in good yield by the reduction of NiCl{sub 2}(PBz{sub 3}){sub 2} with Super-Hydride, whereas the Pd and Pt analogues may be prepared by reduction of the corresponding MCl{sub 2}(PBz{sub 3}){sub 2} complexes with sodium naphthalide under an ethylene atmosphere, followed by the addition of HCl. Addition of NaOPh to trans-NiHCl(P{sup 1}Pr{sub 3}){sub 2} or trans-NiHCl(PCy{sub 3}){sub 2}, where {sup i}Pr = i-C{sub 3}H{sub 7} and Cy = c-C{sub 6}H{sub 11}, produces the corresponding hydrido phenoxo complexes, while the addition of NaOPh to trans-NiHCl(PBz{sub 3}){sub 2} yields trans-NiH(OPh)(PBz{sub 3}){sub 2}{center dot}HOPh. Addition of phenol to Pd(CH{sub 3}){sub 2}(dmpe), where dmpe = 1,2-bis(dimethyl-phosphino)ethane, yields Pd(CH{sub 3})(OPh)(dmpe). The reactivity of these late-transition-metal phenoxides suggests a high nucleophilicity for the metal-bound phenoxide, as evidenced by alkylation at oxygen by methyl iodide or by the insertion of an electrophile such as phenyl isocyanate. Thermally unstable hydrido anilido complexes trans-PdH(NHPh)L{sub 2}, where L = P({sup i}Pr){sub 3} or PCy{sub 3}, were prepared by addition of NaNHPh to the corresponding hydrido chloro complexes. With the use of Na{sup 15}NHPh it was possible to definitively characterize the solution structures of these unstable species by NMR spectroscopy. Besides exhibiting alkylation and insertion reactivity similar to the phenoxide complexes, these compounds were extremely susceptible to reductive elimination of aniline on addition of ligands, such as acrylonitrile. A consideration of bond strengths, along with the observed tendencies for reductive elimination, suggests that catalytic animation of olefins by a cycle that requires N-H oxidative addition has thermodynamic limitations for the late transition metals.