The novel copper(i) ethylene complex [Bu t 2 P(NSiMe 3 ) 2k 2 N]Cu(h 2 -C 2 H 4 ) and its norbornene analogue have been synthesized and characterized and their solid state structures determined.

Cationic Ru carbene complexes with tBu PCH PtBu (dtbpm) as a chelating ligand, which are accessible by chloride abstraction from neutral precursors [(κ -dtbpm)Cl Ru=CHR] with trimethylsilyl triflate, are established as highly efficient ring opening metathesis polymerization catalysts (see scheme). Solv=solvent.

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γ‐C−H agostic stabilization of the 14‐electron metal center by a saturated hydrocarbon group characterizes the structure of the first neutral, three‐coordinate alkylrhodium(I) complex [(κ2‐dtbpm)RhNp] (1; dtbpm = bis(di‐tert‐butylphosphanyl)methane, Np=neopentyl). Some of its reactions, for example, N2 complexation and C−H bond activation, are reported.

The preparation of a series of nickel dichloride complexes with bulky diphosphinomethane chelate ligands R2PCH2PR′2 is reported. Reaction with the appropriate Grignard reagent leads to the corresponding dimethyl and dibenzyl complexes. Cationic monomethyl and mono-η3-benzyl complexes are generated from these dialkyl complexes by protonation with [H­(OEt2)2]+[B­(3,5-(CF3)2C6H3)4]−, while the complex [(dtbpm-κ2 P)­Ni­(η3-CH­(CH2Ph)­Ph]+[B­(3,5-(CF3)2C6H3)4]− is obtained from protonation of the Ni(0) olefin complex (dtbpm-κ2 P)­Ni­(η2-trans-stilbene). Crystal structures of examples of dichlorides, dimethyl, dibenzyl, cationic methyl, and cationic η3-benzyl complexes are reported. Solutions of the cations polymerize ethylene under mild conditions and without the necessity of an activating agent, to form polyethylene having high molecular weights and low degrees of chain branching. In comparison to the Ni methyl cations, the η3-benzyl cation complexes are more stable and somewhat less active but still very efficient in C2H4 polymerization. The effect on the resulting polyethylene of varying the substituents R, R′ on the phosphine ligand has been examined, and a clear trend for longer chain PE with less branching in the presence of more bulky substituents on the diphosphine has been found. Density functional calculations have been used to examine the rapid suprafacial η3 to η3 haptotropic shift processes of the [(R2PCH2PR′2)­Ni] fragment and the η3–η1 change of the coordination mode of the benzyl group required for polymerization in those cations.