A new nonsymmetric bis(aryl‐imino)acenaphthene (Ar‐BIAN) ligand, 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. The series of the monocationic complexes [Pd(CH3)(L)(Ar‐BIAN)][PF6] (L=CH3CN, dmso) has been extended to dimethyl sulfoxide derivatives. The monocationic complexes are tested as precatalysts for the ethylene/methyl acrylate cooligomerization under mild reaction 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.

The dimethylaluminum compounds Al(CH 3 ) 2 [(O-2-{(C 6 F 5 )NCH}-4,6-R 2 C 6 H 2 )], R = H (1) or cumyl (2), were synthesized and tested as initiators in the homo-and copolymerization of rac-lactide and glycolide. These complexes resulted active for the production of PLGA copolymers with variable microstructure. All the copolymers were fully characterized by NMR, GPC, and DSC analysis. The copolymerization reactions were performed in bulk and in solution, by varying comonomers ratio, monomer/catalyst feed ratio, temperature, reaction time, and solvent. Interestingly, by changing the reaction conditions, copolymers from random, to blocky, to diblock were obtained, demonstrating the effectiveness and versatility of such systems in modulating the copolymers microstructure and the related thermal properties.

The homo and co-polymerization of a large ring size lactone afforded unsaturated poly(esters), further modified to functional thermoplastic materials.

Publication informationOrganometallics, 31 (3) In one set, the pyridine and the carbene are linked by a flexible CH 2 group (a), in the other two sets, the two ligand units are directly linked and feature a shielding mesityl substituent on the carbene and either an unsubstituted pyridine (b) or a xylyl-substituted pyridine unit (c).Investigation of the reactivity of cationic complexes [Pd(C^N)Me(NCMe)] + , 6, analogues to Brookhart's α-diimine system, towards alkenes showed a strong correlation between the catalytic activity and selectivity and the ligand setting. While 6a was inactive in ethylene conversion, 6b afforded low-molecular weight olefins (oligomerization), and 6c produced exclusively butene (dimerization). With styrene as substrate, exclusive dimerization occurred with all three complexes. Steric and electronic factors were identified that govern the disparate activity and selectivity, and that allow for efficient tailoring of the catalytic performance.2

The catalytic CO/styrene and ethylene/methyl acrylate copolymerizations are compared for the first time by applying the same precatalysts. With this aim, PdII neutral, [Pd(CH3)Cl(N–N)], and monocationic, [Pd(CH3)(L)(N–N)][PF6] (L=CH3CN, DMSO), complexes with 1-naphthyl- and 2-naphthyl-substitued α-diimines with both an acenaphthene and a diazabutadiene skeleton as chelating nitrogen-donor ligands (N–N) have been studied. In the case of the complexes with the 1-naphthyl-substituted ligands, syn and anti isomers are found both in solid state and in solution. All the monocationic complexes generate active catalysts for the CO/styrene copolymerization leading to atactic or isotactic/atactic stereoblock copolymers depending on the ligand bonded to palladium. Instead, in the case of the ethylene/methyl acrylate copolymerization only the complexes with the 1-naphthyl-substituted ligands generate catalysts for this reaction