Zinc Complexes with Cyanoxime: Structural, Spectroscopic, and Catalysis Studies in the Pivaloylcyanoxime–Zn System

Abstract

Reaction of 2-hydroxyimino-4,4-dimethyl-3-oxo-pentanenitrile (common abbreviation HPiCO, pivaloyl-cyanoxime) with zinc sulfate in an aqueous solution results in the formation of the two new complexes: [Zn(PiCO){H(PiCO)}(HO)] (I) and tetranuclear Zn complex [Zn(μ-OH)(PiCO) (HO)] (II). Both complexes were characterized by elemental analysis, IR- and UV-visible spectra, DSC/TGA studies, and X-ray analysis. In complex II, the PiCO cyanoxime anion adopts three bidentate binding modes: O-monodentate, chelating (κ), and bridging (η) coordinations. Also, the ligand represents the mixture of two diasteromers (cis-anti and cis-syn) that form five- and six-membered chelate rings with Zn atoms and cocrystallize in one unit cell at population of 0.57-0.43. There are two crystallographically different Zn-centers in the ASU, and two μ-bridging hydroxo-groups arrange via inversion center the formation of an elegant tetranuclear complex. Each Zn atom has a molecule of coordinated water and is in the distorted octahedral environment. Because of the structural flexibility and multidentate propensity of the pivaloyl-cyanoxime, complex II may act as a structural model of naturally occurring Zn-containing enzymes. Indeed, compound I exhibits an efficient catalytic performance for transesterification reaction of various esters in ethanol under mild reaction conditions. Therefore, obtained results allow assignment of observed activity as green catalysis.

New Route to Polynuclear Ni(II) and Cu(II) Complexes with Bridging Oxime Groups That Are Inaccessible by Conventional Preparations

“…It is reflected in the rising of the ν­(N–O) frequency and lowering of the ν­(CN) frequency, since the fragment attained more nitroso- character, as opposed to the oxime group (Table ). Similar changes have previously been observed in complexes of other cyanoximes. ,,− …”

Dinucleating Schiff base ligand in Zn/4f coordination chemistry: synthetic challenges and catalytic activity evaluation

“…With these optimised conditions in hand [1.0 mol% catalyst loading, AcOEt, rt], we next compared the catalytic activity of our four catalysts (1)(2)(3)(4). Interestingly, catalysts 1 and 2 ( Table 3, entries 1-12) displayed on average a higher efficacy than the pre-catalysts 3 and 4 ( Table 3, entries [13][14]. Overall, the Y III compounds showed a higher catalytic activity than the Dy III derivatives, pre-catalyst 2 being the most effective.…”

“…Coordination clusters (CCs) 1 have recently been the centre of intense scrutiny due to their fascinating magnetic [2][3][4] and luminescent properties 5,6 as well as the very diverse core topologies [7][8][9][10][11] they display. Remarkably, several well characterized or in situ formed homometallic [12][13][14][15] or heterometallic [16][17][18][19] CCs were found to promote organic transformations, whereas fewer examples of heterometallic 3d/4f CCs have been tested for their catalytic activity. These can be classified into two kinds.…”

Emerging catalysis in biomass valorisation: simple Zn(II) catalysts for fatty acids esterification and transesterification

“…[47] Methyl butyrate was efficiently converted using cyclohexanol and octanol and the catalyst showed reusability with very low reduction in activity (entries 21.2, 22.2). In 2017 Opalade et al [48] reported the synthesis of zinc(II) cyanoxime-based complexes, that were characterized using spectroscopic methods, thermal analysis, and X-ray crystallography. One of the new Zn(II) compounds showed some activity in the transesterification of methyl and ethyl butyrate (entries 20.2, 23.2).…”