Stabilization of the labile metal configuration in halfsandwich complexes [CpRh(PN)Hal]X |
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Authors: | Henri Brunner Andreas Köllnberger |
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Institution: | a Institut für Anorganische Chemie, Universität Regensburg, 93040 Regensburg, Germany |
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Abstract: | PN ligands 3 and 4, derived from 2-diphenylphosphanylmethylpyridine 2a, were synthesized, to which in the backbone a tether to a cyclopentadiene system and for comparison an iPr substituent were attached. The chiral compounds were resolved by introduction of a menthoxy substituent into the 2-position of the pyridine system and/or palladium complexes with enantiomerically pure co-ligands. The tripod ligand 3b contains three different binding sites (Cp, P, N) connected by a resolved chiral carbon atom. (SC)-configuration of this tripod ligand enforces (RRh)-configuration at the metal atom in the halfsandwich rhodium complex (LMent,SC,RRh)-7b. The opposite metal configuration is inaccessible. Substitution of the chloro ligand in (LMent,SC,RRh)-7b by halide (Br, I) or pseudohalide (N3, CN, SCN) ligands occurs with retention of configuration to give complexes 8b-11b. However, in the reaction of (LMent,SC,RRh)-7b with PPh3 the pyridine arm of the tripod ligand in compound 13b becomes detached from the metal atom. In the Cp*Rh and CpRh compounds of the bidentate PN ligands 4a and 4b both metal configurations are accessible and in complexes 14a-17a and 14b-17b they equilibrate fast. The stereochemical assignments are corroborated by 9 X-ray analyses. |
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Keywords: | Rhodium Chirality Metal configuration Retention |
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