Novel intramolecular C-H bond activation in an iridium dppm complex

Reaction of TpIr(C(2)H(4))(2) (Tp = tris-pyrazolylborate) with various chelating phosphine ligands has been explored. Reaction with bis-diphenylphosphinoethane leads to complete displacement of the Tp ligand. With bis-diphenylphosphinomethane, an intramolecular proton transfer from the methylene bridge to the iridium center occurs to give an iridium hydride complex formally resulting from oxidative C-H bond activation. Reaction with 2,2-bis(diphenylphosphino)propane (dppip) affords an Ir(I) complex formulated as kappa(2)-TpIr(dppip). Protonation of this Ir(I) complex gives a six coordinate Ir(III) hydride species.     

Silane complexes of electrophilic metal centers

Photolysis of solutions of M(CO)6 (M = Cr, Mo, and W) in the presence of Et3SiH affords the silane complexes Cr(CO)5(eta2-HSiEt3), Mo(CO)5(eta2-HSiEt3), and W(CO)5(eta2-HSiEt3). Observed values of J(SiH) in these complexes are consistent with modest elongation of the Si-H bond. With Ph3SiH, complexes of Cr(CO)5 and W(CO)5 were obtained, but no complex with Mo was observed. When Ph2SiH2 was employed, only one Si-H bond interacts with the metal center. A dynamic exchange process observable on the magnetic resonance time scale exchanges the pendant and coordinated Si-H bonds of the coordinated diphenylsilane. Silanes bound to M(CO)5 are activated with respect to reaction with nucleophiles. With methanol, catalytic methanolysis of HSiEt3 has been observed in the presence of Cr(CO)5(eta2-HSiEt3), affording Et3SiOMe.     

A Convenient One-Pot Synthesis of Di-t-butylphosphinic Chloride

A convenient one-pot synthesis of (t-Bu)₂P(O)Cl (1) from m-chloroperbenzoic acid and (t-Bu)₂PCl is described. The byproduct m-chlorobenzoic acid is neutralized by addition of Et₃N. Complex 1 crystallizes in the monoclinic space group P2₁/c (No. 14), with a = 5.9637(2) Å, b = 11.4734(4) Å, c = 16.2400(5) Å and β = 107.7160(14).     

Characterization of a Palladium Dihydrogen Complex

The preparation and isolation of the first palladium dihydrogen complex is described. NMR spectroscopy reveals a very short H? H bond length, but the hydrogen molecule is activated toward heterolytic cleavage. An X‐ray crystal structure suggests that proton transfer to the ^tBuPCP (κ³‐2,6‐(^tBu₂PCH₂)₂C₆H₃) pincer ligand is possible. The basicity of the ipso‐carbon atom of the pincer ligand was investigated in a related complex.