827339-92-4Relevant academic research and scientific papers
Stabilization of the labile metal configuration in halfsandwich complexes [CpRh(PN)Hal]X
Brunner, Henri,K?llnberger, Andreas,Mehmood, Arshad,Tsuno, Takashi,Zabel, Manfred
, p. 4244 - 4262 (2007/10/03)
In contrast to bidentate ligands, e.g. PN, tripod ligands CpPN- predetermine a single metal configuration preventing formation of the opposite metal configurations. 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 (L Ment,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 (L Ment,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.
