NiII, CuII and ZnII complexes with a sterically hindered scorpionate ligand (TpmsPh) and catalytic application in the diasteroselective nitroaldol (Henry) reaction

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 43; no. 40; pp. 15192 - 15200
• Main Authors: Rocha, Bruno G M, Mac Leod, Tatiana C O, Guedes da Silva, M Fátima C, Luzyanin, Konstantin V, Martins, Luísa M D R S, Pombeiro, Armando J L
• Format: Journal Article
• Language: English
• Published: England 28.10.2014
• Subjects: Catalysis; Copper - chemistry; Crystallography, X-Ray; Heterocyclic Compounds, 3-Ring - chemistry; Ligands; Mesylates - chemistry; Models, Molecular; Nickel - chemistry; Nitro Compounds - chemistry; Stereoisomerism; Zinc - chemistry
• ISSN: 1477-9234
• DOI: 10.1039/c4dt01509f

The Ni(II) and Zn(II) complexes [MCl(Tpms(Ph))] (Tpms(Ph) = SO3C(pz(Ph))3, pz = pyrazolyl; M = Ni 2 or Zn 3) and the Cu(II) complex [CuCl(Tpms(Ph))(H2O)] (4) have been prepared by treatment of the lithium salt of the sterically demanding and coordination flexible tris(3-phenyl-1-pyrazolyl)methanesulfonate (Tpms(Ph))(-) (1) with the respective metal chlorides. The (Tpms(Ph))(-) ligand shows the N3 or N2O coordination modes in 2 and 3 or in 4, respectively. Upon reaction of 2 and 3 with Ag(CF3SO3) in acetonitrile the complexes [M(Tpms(Ph))(MeCN)](CF3SO3) (M = Ni 5 or Zn 6, respectively) were formed. The compounds were obtained in good yields and characterized by analytic and spectral (IR, (1)H and (13)C{(1)H} NMR, ESI-MS) data, density functional theory (DFT) methods and {for 4 and [(n)Bu4N](Tpms(Ph)) (7), the latter obtained upon Li(+) replacement by [(n)Bu4N](+) in Li(Tpms(Ph))} by single crystal X-ray diffraction analysis. The Zn(II) and Cu(II) complexes (3 and 4, respectively) act as efficient catalyst precursors for the diastereoselective nitroaldol reaction of benzaldehydes and nitroethane to the corresponding β-nitroalkanols (up to 99% yield, at room temperature) with diastereoselectivity towards the formation of the anti isomer, whereas the Ni(II) complex 2 only shows a modest catalytic activity.