| Abstract
| - The synthesis, characterization, and hemithioacetal isomerization reactivity of a mononuclearNi(II) deprotonated amide complex, [(bppppa-)Ni]ClO4·CH3OH (1, bppppa- = monoanion of N,N-bis-[(6-phenyl-2-pyridyl)methyl]-N-[(6-pivaloylamido-2-pyridyl)methyl]amine), are reported. Complex 1 was characterized by X-ray crystallography, 1H NMR, UV−vis, FTIR, and elemental analysis. Treatment of 1 withan equimolar amount of the hemithioacetal PhC(O)CH(OH)SCD3 in dry acetonitrile results in the productionof the thioester PhCH(OH)C(O)SCD3 in ∼60% yield. This reaction is conveniently monitored via 2H NMRspectroscopy. A protonated analogue of 1, [(bppppa)Ni](ClO4)2 (2), is unreactive with the hemithioacetal,thus indicating the requirement of the anionic chelate ligand in 1 for hemithioacetal isomerization reactivity.Complex 1 is unreactive with the thioester product, PhCH(OH)C(O)SCD3, which indicates that the pKavalue for the PhCH(OH)C(O)SCD3 proton of the thioester must be significantly higher than the pKa valueof the C−H proton of the hemithioacetal (PhC(O)CH(OH)SCD3). Complex 1 is the first well-characterizedNi(II) coordination complex to exhibit reactivity relevant to Ni(II)-containing E. coli glyoxalase I. Treatmentof NiBr2·2H2O with PhC(O)CH(OH)SCD3 in the presence of 1-methylpyrrolidine also yields thioester product,albeit the reaction is slower and involves the formation of multiple −SCD3 labeled species, as detected by2H NMR spectroscopy. The results of this study provide the first insight into hemithioacetal isomerizationpromoted by a synthetic Ni(II) coordination complex versus a simple Ni(II) ion.
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