Photochemistry of bis-{chloro(dicarbonyl)rhodium} in low temperature frozen gas matrices at 12 K and in Nujol mulls at 77 K: infrared and electronic spectroscopic evidence for retention of the bis-{(chloro)rhodium} bridging unit but photoejection of

摘要

Infrared and electronic spectroscopic evidence is presented in relation to the photochemical reactions of {(Cl)(CO)(2)Rh}(2), whose bent structure has been confirmed by Fourier transform Raman spectroscopy. Photolysis in Ar, CH4 and N-2 gas matrices at ca. 12 K and in Nujol mulls at ca. 77 K leads to facile and reversible ejection of the terminal CO ligands but retention of the {(Cl)Rh}(2) bridging unit. The primary species formed were Rh-2(Cl)(2)(CO)(3) in Ar, CH4 and Nujol media and Rh-2(Cl)(2)(CO)(3)(N-2) in N-2 matrices. Further reversible CO loss afforded {Rh(Cl)(CO)}(2) and {Rh(Cl)(CO)(N-2)}(2), respectively. In CO matrices the modest photoreaction was interpreted in terms of CO addition to give an 18 electron dimeric species {Rh(Cl)(CO)(3)}(2) rather than bridge cleavage to give the 16 electron species Rh(Cl)(CO)(3). In view of the facility of the CO ejection/recombination processes it is suggested that such reaction pathways could be important in the substitution reactions of {Rh(Cl)(CO)(2)}(2) and could aid the interpretation of the kinetic data. (C) 1998 Elsevier Science S.A. [References: 37]