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Preparation of a Family of Hexanuclear Rhenium Cluster Complexes Containing 5-(Phenyl)tetrazol-2-yl Ligands and Alkylation of 5-Substituted Tetrazolate Ligands

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posted on 20.02.2016, 17:12 by Jessica L. Durham, Joan N. Tirado, Stanley A. Knott, Meghan K. Oh, Robert McDonald, Lisa F. Szczepura
The preparation of two new families of hexanuclear rhenium cluster complexes containing benzonitrile and phenyl-substituted tetrazolate ligands is described. Specifically, we report the preparation of a series of cluster complexes with the formula [Re6Se8(PEt3)5L]2+ where L = benzonitrile, p-aminobenzonitrile, p-methoxybenzonitrile, p-acetylbenzonitrile, or p-nitrobenzonitrile. All of these complexes undergo a [2 + 3] cycloaddition with N3 to generate the corresponding [Re6Se8(PEt3)5(5-(p-X-phenyl)­tetrazol-2-yl)]+ (or [Re6Se8(PEt3)5(2,5-p-X-phenyltetrazolate)]+) cluster complexes, where X = NH2, OMe, H, COCH3, or NO2. Crystal structure data are reported for three compounds: [Re6Se8(PEt3)5(p-acetylbenzonitrile)]­(BF4)2•MeCN, [Re6Se8(PEt3)5(2,5-phenyltetrazolate)]­(BF4)•CH2Cl2, and [Re6Se8(PEt3)5(2,5-p-aminophenyltetrazolate)]­(BF4). Treatment of [Re6Se8(PEt3)5(2,5-phenyltetrazolate)]­(BF4) with HBF4 in CD3CN at 100 °C leads to protonation of the tetrazolate ring and formation of [Re6Se8(PEt3)5(CD3CN)]2+. Surprisingly, alkylation of the phenyl and methyl tetrazolate complexes ([Re6Se8(PEt3)5(2,5-N4CPh)]­(BF4) and [Re6Se8(PEt3)5(1,5-N4CMe)]­(BF4)) with methyl iodide and benzyl bromide, leads to the formation of mixtures of 1,5- and 2,5-disubstituted tetrazoles.