Stereoselective addition reactions of diphenylphosphine to pyridyl and pyrimidylalkynes: chiral 1,2-diheteroaryl-1,2-bis(diphenylphosphino)ethanes and their Group 6 metal carbonyl complexes

摘要

The base-catalysed addition of diphenylphosphine to the diarylethynes RC ident to CR' (R = R' = 2-pyridyl 1; R = R' = 3-pyridyl 2; R = 2-pyridyl, R' = 3-pyridyl 3; R = phenyl, R' = 2-pyridyl 4, 3-pyridyl 5, 2-pyrimidyl 6) yield diphosphines of general formula Ph_2PCH(R)CH(R')PPh_2 together with alkene by-products Ph_2PC(R)=CHR' and HC(R)=C(R')PPh_2 in all cases except 1. Selected P,P'-coordinated M(CO)_4 complexes (M = Mo, W) of the diphosphines have been prepared and their ~1H-, ~(13)C- and ~(31)P-NMR data are presented. The pattern of ~(13)CO-NMR signals for the tetracarbonyl complexes was used unambiguously to determine the stereochemistry of the parent diphosphine. At moderately elevated temperatures, nitrogen coordination of 2-pyridyl and 2-pyrimidyl groups occurred for tetracarbonyl complexes of meso- or erythro-stereochemistry, but not for complexes of rac- or threo-form, to yield corresponding fac-tricarbonyl complexes. At 162 deg C the complex cis-rac-(CO)_4W{P,P'-Ph_2PCH(R)CH(R)PPh_2} (R = R' = 2-pyridyl) is converted quantitatively into fac-erythro-(CO)_3W{P',N-Ph_2PCH(R)CH(R)PPh_2} via an inversion/N-coordination pathway.