A new polynorbornene skeleton has been found that contains bicyclic norbornane units and cyclohexenyl methyl linkages. The polymers have been synthesized using a nickel catalyst in the presence of a...

A large variety of α-(pentafluorophenylmethyl)benzylic palladium complexes with different ligands have been synthesized and characterized. Multinuclear NMR spectroscopic data allow to determine the σ-or η 3-benzylic nature of the complexes in solution. The adoption of either coordination mode is a function of the number of ligands coordinated to palladium and, remarkably, the presence of bulky phosphines favors the adoption of a bidentate η 3-benzylic mode and palladium pentacoordinated complexes. Experimental data and DFT calculations indicate that this fivecoordination could alleviate the steric hindrance of two cis bulky phosphines. The benzylic complexes show a rich fluxional behavior that involves both ligand exchange and σ-to η 3-benzylic interconversion.

New routes to functionalize the robust VA-polynorbornene skeleton by Pd-catalyzed cross-coupling reactions use p-bromoaryl- and ω-bromoalkyl-VA-PNBs as versatile starting materials.

The adoption of a pseudoallylic (η 3) form makes palladium benzylic derivatives a class of stabilized palladium alkyls that can undergo β-H elimination reactions in a more controlled way. α-(Pentafluorophenylmethyl)benzyl palladium complexes have been studied and they decompose by β-H elimination to give palladium hydrides that, depending on the auxiliary ligands can: a) transmetalate to another palladium atom and, by reductive elimination, give hydrogenated products; this process is favored for a combination of bridging ligands (i.e halogens) and low coordinating ligands. b) Be used as a hydride source and get trapped by a diene to give palladium allylic derivatives. The presence of carbon monoxide does not induce a β-H elimination reactions and only CO insertion into the Pdbenzyl bond to give acyl derivatives is observed.

The incorporation of functional groups in the skeleton of vinylic addition polynorbornenes (VA-PNBs) is a difficult task due to the reluctant VA homo- and copolymerization of substituted norbornenes. We have...