Tetrazole and triazole carbene complexes of group 6 metal carbonyls |
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Authors: | Guido D Frey Karl Öfele Herbert G Krist Eberhardt Herdtweck Wolfgang A Herrmann |
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Institution: | Department Chemie, Lehrstuhl für Anorganische Chemie, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching, Germany |
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Abstract: | In order to study the relative stability of cis- and trans-isomers of bis(NHC)tetracarbonyl complexes of group 6 metals, we synthesized the corresponding complexes with triazolin- and tetrazolinylidene ligands. By reaction of the free carbene (L = 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazolin-5-ylidene) - first synthesized by Enders - with the hexacarbonyls of Cr, Mo and W the corresponding M(L)(CO)5 complexes are generated. Depending on an excess of carbene also the cis-(L)2Mo(CO)4 complex was obtained. The latter can be photolytically converted to the trans-(L)2Mo(CO)4 complex. The corresponding complexes with the 1,4-dimethyltetrazolin-5-ylidene ligand (L′), Cr(L′)(CO)5, cis-(L′)2Cr(CO)4 and trans-(L′)2Cr(CO)4 can be obtained by reaction of hexacarbonyl-μ-trihydroxy-dichromate with dimethyltetrazolium salt. In the cis-(L′)2Cr(CO)4 complex, one carbonyl ligand can be replaced by donor ligands such as pyridine or phenylisocyanide to form sym-mer-tricarbonyl complexes. All new complexes are fully characterized by spectroscopy and most by single-crystal X-ray analysis. |
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Keywords: | Carbene complexes Group 6 carbonylcomplexes N-heterocyclic carbenes 1 2 4-Triazolin-5-ylidene 1 2 3 4-Tetrazolin-5-ylidene |
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