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© The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.The novel class of bis-arylaminoacenaphthylenes (Ar-BIANH2) was employed for the preparation of zirconium and yttrium complexes to be used as catalysts for cyclohydroamination of a number of primary and secondary aminoalkenes. The complex [(2,6-iPr2C6H3-BIAN)Zr(NMe2)2(η1-NHMe2)] was isolated and completely characterized, including X-ray diffraction analysis. Despite its easy and almost quantitative isolation, it showed only moderate catalytic performance in the intramolecular hydroamination, irrespective of the cyclization precursor used. On the other hand, in situ generated YIII complexes obtained using the same class of ligands were found to be very active, leading to the hydroamination of substrates including those normally reluctant in undergoing cyclization such as those featuring an internal non-activated C...C double bond. Electron donating substituents and especially steric hindrance on the ligand improve the performance of the catalysts, allowing us to decrease the catalyst loading to 1 mol% in the latter case.

A new nonsymmetric bis(aryl-imino)acenaphthene ligand (Ar-BIAN), featured by a subtle steric and electronic unbalance of the N-donor atoms, is reported. With the new ligand and the corresponding symmetrically substituted derivatives both neutral and monocationic Pd-CH3 compounds have been synthesized and characterized. In particular, the series of the monocationic complexes [Pd(CH3)(L)(Ar-BIAN)][PF6] (L = CH3CN, dmso) has been now extended to dimethyl sulfoxide derivatives. The monocationic complexes were tested as precatalysts for the ethylene/methyl acrylate cooligomerization under mild conditions of temperature and ethylene pressure. The catalytic product is a mixture of ethylene/acrylate cooligomers and higher alkenes. The catalysts containing the new nonsymmetric ligand are found to be more productive than those with the symmetric Ar-BIANs. The Pd-dmso catalysts are more productive and show a longer lifetime than their Pd-NCCH3 counterparts.

One of the major unsolved problems in polymer chemistry is represented by the synthesis of functionalized polyolefines, that are currently produced through radical processes, a technology that suffers from high energy consumption, low cost efficiency and poor control over the macromolecule structure.1 The direct, controlled, homogeneously catalyzed copolymerization of ethylene with polar vinyl monomers represents a sustainable technology to overcome these limits. The main catalytic systems reported in the literature are based on Pd(II) compounds with either -diimines or phosphino-sulfonate ligands.2 Their productivity is thus far low from the values required for an industrial application, and better performing catalysts are strongly needed. With this aim we are studying Pd(II) complexes with new nonsymmetric -diimines (Ar,Ar'-BIAN) featured by an acenaphthene skeleton and one aryl ring substituted in meta positions with electron-withdrawing groups, while the other ring bears electron-releasing substituents on the ortho positions (Figure up). The related monocationic complexes, [Pd(CH3)(Ar,Ar'-BIAN)(L)][PF6], that include both acetonitrile and dimethyl sulfoxide derivatives, have been applied as precatalysts in the ethylene/methyl acrylate copolymerization under mild conditions of temperature and pressure showing a remarkably different catalytic behaviour depending on the nature of the L ligand (Figure below).3 While the catalyst originated from the acetonitrile precursor was found to be less active than the dmso counterpart and to deactivate within 16 h of reaction, that obtained from the dmso derivative was still active after 48 h achieving a productivity of 350 g P/g Pd. The catalysts with the nonsymmetric Ar,Ar'-BIAN showed a productivity twice as high as that of the catalysts with the corresponding symmetric ligands together with a higher incorporation of the polar monomer into the catalytic product. The latter is a mixture of ethylene oligomers and ethylene/methyl acrylate cooligomers, having the polar monomer at the end of the branches. Detailed investigation on the studied catalytic system will be presented. 1A. Nakamura, S. Ito and K. Nozaki, Chem. Rev., 2009, 109, 5215. 2 a) L.K. Johnson, S. Mecking and M. Brookhart, J. Am. Chem. Soc., 1996, 118, 267; b) E. Drent, R. van Dijk, R. van Ginkel B. van Oort and R.I. Pugh, Chem. Commun., 2002, 744. 3A. Meduri, T. Montini, F. Ragaini, P. Fornasiero, E. Zangrando and B. Milani, ChemCatChem published on the web, DOI: 10.1002/cctc.201200520.