876349-63-2Relevant academic research and scientific papers
Dizinc alkoxides and amides supported by binucleating bis(amidoamine) ligands
Hlavinka, Mark L.,McNevin, Michael J.,Shoemaker, Richard,Hagadorn, John R.
, p. 1815 - 1822 (2006)
Several new dizinc complexes that are supported by dianionic bis(amidoamine) ligands are reported. Reaction of N,N′-bis(2- dimethylaminoethyl)dibenzofuran-4,6-diamine (MeLH2) with 2 equiv of EtZn(OiPr) forms the dizinc bis-(alkoxide) MeLZn2(OiPr)2 (1), which was isolated in 76% yield. Similarly, MeLH2 reacts cleanly with EtZn(OPh) and EtZn(OCHPh2) to form MeLZn 2(OPh)2 (2) and MeLZn2(OCHPh 2)2 (3), respectively. The solid-state structures of 1 and 2 feature puckered [Zn2(μ-OR)2]2+ cores, with short intermetal separations (2.81-2.88 A). Overall, the molecules have approximate (noncrystallographic) C2v symmetry. The use of the more-hindered iPr-substituted ligand N,N′-bis(2- diisopropylaminoethyl)dibenzofuran-4,6-diamine (iPrLH2) to prepare zinc alkoxides gave similar results. Thus, reaction of iPrLH2 with 2 equiv of EtZn(OPh), EtZn(OMe), EtZn(OCHPh2), and EtZn(OCH2Ph) forms iPrLZn2(OPh)2 (4), iPrLZn 2(OMe)2 (5), iPrLZn2(OCHPh 2)2 (6), and iPrLZn2(OCH 2Ph)2 (7), respectively (isolated yields 48-63%). At 70°C, C6D6 solutions of 6 undergo β-hydride transfer with 2 equiv of benzaldehyde to form 7 and benzophenone in quantitative yield (according to 1H NMR spectroscopy). Benzene solutions of 1 react with 1 equiv of trimethylsilyl trifluoromethanesulfonate (Me 3SiOTf) to form MeLZn2(OiPr)(OTf) (8) in 70% isolated yield. In the solid state, 8 features a bridging alkoxide donor as well as a 1,3-bridging triflate group. The previously reported dinuclear organozinc species MeLZn2Ph2 (9) reacts with 1 equiv of tert-butylamine to form the protonolysis product MeLZn2(Ph)(NHtBu) (10) in 66% isolated yield. The solid-state structure of 10 (two independent molecules) reveals a somewhat asymmetric [Zn2(μ-Ph)(μ-NHtBu)]2+ core with short Zn-Zn separations [2.6761(5) and 2.6518(5) A]. In CD 2Cl2 solution, the Ph bridge of 10 undergoes rapid reversible cleavage. Cleavage of this bridging interaction followed by rotation about the Zn-Ph bond and re-formation of the bridging interaction results in exchange of the inequivalent ortho (and meta) protons of the phenyl ligand. Variable-temperature 1H NMR spectroscopic data indicate that this exchange occurs with ΔG≠ = 12.7(1) kcal·mol -1 (-27°C). At 75°C, toluene solutions of MeLH2 react with 2 equiv of EtZn-NHtBu to form the dizinc bis(amido) product MeLZn2(NH tBu)2 (11) in 46% isolated yield. The solid-state structure of 11 (two independent molecules) features a puckered and fairly symmetric [Zn2(μ-NHtBu)2]2+ core with short intermetal separations [2.775(1), 2.760(1) A].
