137039-41-9Relevant academic research and scientific papers
Rotational isomerism and fluxional behavior of bis(carbon dioxide) adducts of molybdenum
Carmona, Ernesto,Hughes, Andrew K.,Mu?oz, Miguel A.,O'Hare, Dermot M.,Pérez, Pedro J.,Poveda, Manuel L.
, p. 9210 - 9218 (1991)
The exchange reactions involving the bis(carbon dioxide) complex trans-Mo(CO2)2(PMe3)4 (1) and chelating phosphines P-P (Me2PCH2PMe2, dmpm; Me2PCH2PMe2, dmpe; Et2PCH2CH2PEt2, depe; and Ph2PCH2CH2PPh2, dppe) and isocyanides, CNR, provide efficient routes to the new (CO2)2 adducts trans-Mo(CO2)2(P-P)(PMe3)2 (P-P = dmpe (3a), depe (3b), dmpm (3c), dppe (3d)), trans-Mo(CO2)2(P-P)2 (P-P = dmpe (4a), depe (4b)), and trans-Mo(CO2)2(depe)(PMe3)(CNR) (R = But (5a), Cy (5b)). Due to the asymmetric nature of the coordinated CO2 groups and to the existence of different ligands (PMe3, P-P, CNR) in the plane perpendicular to the O2C-Mo-CO2 bond axis, several isomers arising from the different conformations of the CO2 ligands are possible for each of the above type of complex. Their existence has been demonstrated by variable-temperature NMR spectroscopy, and they have furthermore been shown to interconvert in solution. Four nondissociative mechanisms have been considered for this exchange process, of which one that involves exchange of the coordinated and free oxygen atoms of one of the CO2 ligands has been shown to be inoperative. Two rotational mechanisms, namely an independent rotation and a disrotatory motion, have also been excluded. A concerted rotation of the CO2 groups in which both molecules rotate in the same direction is in accord with all the experimental results.
