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Synthesis and reactivity of a nickel(ii) thioperoxide complex: demonstration of sulfide-mediated N2O reduction.

ABSTRACT: The thiohyponitrite ([SNNO]2-) complex, [K(18-crown-6)][L tBuNiII(?2-SNNO)] (L tBu = {(2,6-iPr2C6H3)NC( t Bu)}2CH), extrudes N2 under mild heating to yield [K(18-crown-6)][L tBuNiII(?2-SO)] (1), along with minor products [K(18-crown-6)][L tBuNiII(?2-OSSO)] (2) and [K(18-crown-6)][L tBuNiII(?2-S2)] (3). Subsequent reaction of 1 with carbon monoxide (CO) results in the formation of [K(18-crown-6)][L tBuNiII(?2-SCO)] (4), [K(18-crown-6)][L tBuNiII(S,O:?2-SCO2)] (5), [K(18-crown-6)][L tBuNiII(?2-CO3)] (6), carbonyl sulfide (COS) (7), and [K(18-crown-6)][L tBuNiII(S2CO)] (8). To rationalize the formation of these products we propose that 1 first reacts with CO to form [K(18-crown-6)][L tBuNiII(S)] (I) and CO2, via O-atom abstraction. Subsequently, complex I reacts with CO or CO2 to form 4 and 5, respectively. Similarly, the formation of complex 6 and COS can be rationalized by the reaction of 1 with CO2 to form a putative Ni(ii) monothiopercarbonate, [K(18-crown-6)][L tBuNiII(?2-SOCO2)] (11). The Ni(ii) monothiopercarbonate subsequently transfers a S-atom to CO to form COS and [K(18-crown-6)][L tBuNiII(?2-CO3)] (6). Finally, the formation of 8 can be rationalized by the reaction of COS with I. Critically, the observation of complexes 4 and 5 in the reaction mixture reveals the stepwise conversion of [K(18-crown-6)][L tBuNiII(?2-SNNO)] to 1 and then I, which represents the formal reduction of N2O by CO.

SUBMITTER: Hartmann NJ

PROVIDER: S-EPMC6115681 | biostudies-other | 2018 Aug

REPOSITORIES: biostudies-other

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Synthesis and reactivity of a nickel(ii) thioperoxide complex: demonstration of sulfide-mediated N2O reduction.

Hartmann Nathaniel J NJ Wu Guang G Hayton Trevor W TW

Chemical science 20180627 31

The thiohyponitrite ([SNNO]2-) complex, [K(18-crown-6)][L tBuNiII(κ2-SNNO)] (L tBu = {(2,6-iPr2C6H3)NC( t Bu)}2CH), extrudes N2 under mild heating to yield [K(18-crown-6)][L tBuNiII(η2-SO)] (1), along with minor products [K(18-crown-6)][L tBuNiII(η2-OSSO)] (<b ...[more]

PMID: 30310590

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Project description:Interest in O2-dependent aliphatic carbon-carbon (C-C) bond cleavage reactions of first row divalent metal diketonate complexes stems from the desire to further understand the reaction pathways of enzymes such as DKE1 and to extract information to develop applications in organic synthesis. A recent report of O2-dependent aliphatic C-C bond cleavage at ambient temperature in Ni(ii) diketonate complexes supported by a tridentate nitrogen donor ligand [(MBBP)Ni(PhC(O)CHC(O)Ph)]Cl (7-Cl; MBBP = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine) in the presence of NEt3 spurred our interest in further examining the chemistry of such complexes. A series of new TERPY-ligated Ni(ii) diketonate complexes of the general formula [(TERPY)Ni(R2-1,3-diketonate)]ClO4 (1: R = CH3; 2: R = C(CH3)3; 3: R = Ph) was prepared under air and characterized using single crystal X-ray crystallography, elemental analysis, 1H NMR, ESI-MS, FTIR, and UV-vis. Analysis of the reaction mixtures in which these complexes were generated using 1H NMR and ESI-MS revealed the presence of both the desired diketonate complex and the bis-TERPY derivative [(TERPY)2Ni](ClO4)2 (4). Through selective crystallization 1-3 were isolated in analytically pure form. Analysis of reaction mixtures leading to the formation of the MBBP analogs [(MBBP)Ni(R2-1,3-diketonate)]X (X = ClO4: 5: R = CH3; 6: R = C(CH3)3; 7-ClO4: R = Ph; X = Cl: 7-Cl: R = Ph) using 1H NMR and ESI-MS revealed the presence of [(MBBP)2Ni](ClO4)2 (8). Analysis of aerobic acetonitrile solutions of analytically pure 1-3, 5 and 6 containing NEt3 and in some cases H2O using 1H NMR and UV-vis revealed evidence for the formation of additional bis-ligand complexes (4 and 8) but suggested no oxidative diketonate cleavage reactivity. Analysis of the organic products generated from 3, 7-ClO4 and 7-Cl revealed unaltered dibenzoylmethane. Our results therefore indicate that N3-ligated Ni(ii) complexes of unsubstituted diketonate ligands do not exhibit O2-dependent aliphatic C-C bond clevage at room temperature, including in the presence of NEt3 and/or H2O.

Dataset Information

Synthesis and reactivity of a nickel(ii) thioperoxide complex: demonstration of sulfide-mediated N2O reduction.

Publications

Synthesis and reactivity of a nickel(ii) thioperoxide complex: demonstration of sulfide-mediated N<sub>2</sub>O reduction.

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