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

Abstract

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 NMRmore » 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.« less