N,N 0 -Di(S-phenylethyl)-2-amino-4-iminopent-2-ene, S,S-nacnac CH(Me)Ph H, 1a, and N,N 0 -dibenzyl-2amino-4-iminopent-2-ene, nacnac Bn H, 1b, react with ZnEt 2 to form the corresponding nacnacZnEt complexes 2a and 2b. Neither complex is reactive with 2-propanol or methyl lactate to produce the corresponding alkoxide complexes. In reactions with 2b, ligand redistribution occurs and nacnac Bn 2 Zn was obtained. Reaction of 1a and 1b with Zn(N(SiMe 3 ) 2 ) 2 yielded nacnacZnN(SiMe 3 ) 2 , 6a and 6b. From further reactions with 2-propanol nacnacZnOiPr, 7a and 7b, were obtained. Both complexes were catalytically active for polymerization of rac-lactide with apparent first-order rate constants of k app =0.013-0.019 min -1 and 0.019-0.038 min -1 for 7a and 7b, respectively. Obtained polymers were highly heterotactic, with P r =0.84-0.87 (7a) and 0.65-0.71 (7b). Analysis of remaining monomer after 75% conversion showed negligible ee and indicates that chiral 7a does not show enantioselectivity in rac-lactide polymerization. Complex 7a, but not 7b, catalyzes unselective transesterification of the polymer during and after polymerization. PLA microstructures in polymerizations with 7b were independent of temperature (23 or 0 °C) or monomer/catalyst ratio (100:1 to 400:1). However, slightly higher P r values were obtained in the presence of 10-100 equiv of MeCN or pyridine. Complexes nacnac Bn 2 Zn, 2b, 6b, and 7a were characterized by an X-ray diffraction study.

The chiral diketiminate ligand bis-N,N 0 -(2-phenylethyl)-2,4-diiminopentane, 1H, was synthesized in good yields in a one-step reaction from chiral amine and acetylacetone. Reaction of 1Li(THF) with N-bromosuccinimide yielded the succinimide-substituted ligand 2H. Copper complexes were obtained by reaction of the ligand with a basic copper source in the presence of coordinating Lewis bases, and 1Cu(NCMe), 1Cu(DMAP), 1Cu(PPh 3 ), 1Cu(2,6-xylyl isonitrile), 2Cu(PPh 3 ), and 2Cu (2,6-xylyl isonitrile) have been prepared and, for the most part, characterized by X-ray diffraction studies. Compared to their more common analogues with aromatic substituents on N, 1 and 2 seem to be more basic (1 > 2) and sterically more demanding (2 > 1). Their copper complexes are less stable than those of aryl-substituted diketiminates and tend to decompose by disproportionation, most probably after dissociation of the coordinated Lewis base. Despite the rotational freedom around the N-R* bond, the complexes are sterically rigid, a necessary requirement for potential applications in enantioselective catalysis.

N,N'-Dibenzyl-4-amino-2-iminopent-3-ene, nacnac Bn H, was obtained in a one-step synthesis starting from benzylamine and acetylacetone. Reaction of nacnac Bn H with CuOtBu in the presence of various Lewis bases gave the corresponding copper complexes (nacnac Bn )CuL (L: 2, styrene; 3, η 2acrylonitrile; 4, allyl phenyl ether; 5, stilbene; 7, xylylisonitrile; 8, triphenylphosphine). With diphenylacetylene (DPA) the dimeric complex {(nacnac Bn )Cu} 2 (μ-DPA), 6, was obtained. In the presence of excess DPA, 6 coordinates additional acetylene to form the monomeric complex (nacnac Bn )Cu(DPA), 6b. All complexes, with the exception of 4 and 6b, were characterized by X-ray diffraction studies. Structural and spectroscopic data indicate that π back-bonding in 2-8 is still weak when compared to other transition metals, but stronger than in most Cu(I) complexes. Olefin exchange experiments indicate preferred binding of electron-deficient olefins. Reaction of 3 with morpholine did not yield any hydroamination products, in agreement with significant π backbonding toward the olefin.

Symmetric N,N′-dialkyl-2-amino-4-imino-pent-2-enes (nacnacRH) can be prepared in high yields in a simple one-pot reaction from acetylacetone and 2 equiv. of amine. Optimized conditions require the azeotropic removal of water, use of a minimum amount of solvent, and of 1 equiv. of acid. Either para-toluenesulfonic acid, hydrochloric acid, or a mixture of both can be employed, with the latter being most advantageous. Symmetric nacnacRH are thus obtained in higher than 95% purity and with 65% yield for R = Me and 80%–95% yields for R = n-Pr, i-Pr, i-Bu, Bn, Cy, and (+)-CH(Me)Ph.

Among the various new challenges of chemical processes in water, research on stable, highly active, and recyclable catalysts is a prosperous field. We present here a palladium−NHC catalyst that was synthesized with good yields through a series of simple synthetic steps. This organometallic species was used as a heterogeneous catalyst in low loadings for Suzuki−Miyaura coupling in neat water, under mild conditions. Reaction conditions were optimized for a simple, green, and support-free procedure, without using any phase transfer agent. The catalyst shows excellent reactivity in short times toward different substrates and a very good recyclability.