287944-36-9Relevant academic research and scientific papers
(η5-pentamethylcyclopentadienyl)rhodium complexes of upper-rim monophosphinated calix[4]arene
Vézina, Martin,Gagnon, Jonathan,Villeneuve, Karine,Drouin, Marc,Harvey, Pierre D.
, p. 273 - 281 (2008/10/08)
A new and convenient synthesis of the upper-rim monobrominated calix[4]arene Br-calixPR2 is reported and has been used as the key precursor for the preparation of both the diphenyl- (6a) and diisopropylphosphine ligands (6b). Reactions of these new ligands with [(C5Me5)RhCl2]2 afford the complexes (calixPR2)(C5Me5)Rh(Cl)2 (8a,b), which can be converted into their corresponding dihydrides (calixPR2)(C5Me5)Rh(H)2 (9a,b) using NaBH4. 6a also reacts with (C5Me5)Rh(CO)2 to form (calixPPh2)(C5Me5)Rh(CO) (10). The X-ray structures for both 8a and 8b confirm the cone geometry of the calix[4]arene bowl and reveal the presence of the phenyl and isopropyl groups over the cavity. With respect to the Rh-P bond, a gauche conformation is depicted in the solid state. Complexes 8a,b and 9a,b appear to be fluxional in solution, as demonstrated from VT 1H and 31P NMR measurements for 8a,b. Molecular modelings confirm the presence of 13 conformers associated with the rotation around the C(calix)-P and P-Rh bonds and the cavity locking groups above it. The minimum energy conformation for the unsaturated (calixPPh2)(C5Me5)Rh complex exhibits the Rh atom well located at the opening of the free cavity.
