25703-58-6Relevant articles and documents
Alkyl and hydrido phenoxo complexes of nickel(II), palladium(II), and platinum(II) hydrido amido complexes of palladium
Seligson, Allen L.,Cowan, Robert L.,Trogler, William C.
, p. 3371 - 3381 (2008/10/08)
The compound trans-NiHCl(PBz3)2, where Bz = CH2C6H5, has been synthesized in good yield by the reduction of NiCl2(PBz3)2 with Super-Hydride, whereas the Pd and Pt analogues may be prepared by reduction of the corresponding MCl2(PBz3)2 complexes with sodium naphthalide under an ethylene atmosphere, followed by the addition of HCl. Addition of NaOPh to trans-NiHCl(PiPr3)2 or trans-NiHCl(PCy3)2, where iPr = i-C3H7 and Cy = c-C6H11, produces the corresponding hydrido phenoxo complexes, while the addition of NaOPh to trans-NiHCl(PBz3)2 yields trans-NiH(OPh)(PBz3)2·HOPh. Crystals of the latter complex belong to the triclinic space group P1 with a = 10.149 (3) A?, b = 14.448 (4) A?, c = 16.090 (4) A?, α = 84.29 (2)°, β = 84.64 (2)°, γ = 80.22 (2)°, V = 2306 (1) A?3, and Z = 2. Refinement of 148 least-squares parameters for 2358 reflections of I > 3σ(I) converged to R = 0.055. The structure about Ni is square planar with Ni-O = 1.949 (7) A? and Ni-O-C = 123.0 (4)°. The phenol of crystallization is hydrogen-bonded to the oxygen of the coordinated phenoxide, as evidenced by the O?O distance between them of 2.54 (1) A?. The O-H group for the hydrogen-bonded phenol occurs at 3370 cm-1 in the solid-state IR spectrum. In CH2Cl2 solution the O-H stretch shifts to 3588 cm-1 because of dissociation to form free phenol. When phenol is added to a solution of Pt(C2H4)(PBz3)2, the complex trans-PtH(OPh)(PBz3)2 is isolated. Crystals of this complex form as the toluene solvate and belong to the space group P1 with a = 10.105 (5) A?, b = 14.762 (4) A?, c = 15.964 (6) A?, α = 84.10 (3)°, β = 87.74 (4)°, γ = 69.44 (3)°, V = 2231 (2) A?3, and Z = 2. Least-squares refinement of 187 parameters for 5646 observed reflections of I > 3σ(I) converged to R = 0.0511. The structure about Pt conforms to a trans square-planar geometry with Pt-O = 2.130 (6) A? and Pt-O-C = 124.2 (5)°. Addition of phenol to Pd(CH3)2(dmpe), where dmpe = 1,2-bis(dimethylphosphino)ethane, yields Pd(CH3)(OPh)(dmpe), which crystallizes in the orthorhombic space group Pbca with a = 10.667 (3) A?, b = 16.460 (6) A?, c = 18.449 (5) A?, V = 3239 (2) A?3, and Z = 8. The geometry about Pd is square planar with Pd-C = 2.101 (9) A?, Pd-O = 2.098 (6) A?, and Pd-O-C = 124.3 (5)°. 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)L2, where L = P(iPr)3 or PCy3, were prepared by addition of NaNHPh to the corresponding hydrido chloro complexes. With the use of Na15NHPh 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. Corresponding hydrido anilido complexes of nickel were unstable when generated by similar procedures. 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.
