Experimental (IR, Raman) and computational analysis of a series of PtBr(2) derivatives: vibrational coupling in the coordinated ethylene and Pt-Br modes.
Compounds ((n)Bu(4)P)[PtBr(3)(C(2)H(4))] (1), trans-[PtBr(2)(NH(2)Ph)(C(2)H(4))] (2), cis-[PtBr(2)(NH(2)Ph)(C(2)H(4))] (3), ((n)PBu(4))(2)[PtBr(4)] (4), ((n)PBu(4))[PtBr(3)(NH(2)Ph)] (5), and cis-[PtBr(2)(NH(2)Ph)(2)] (6), as well as the trichlorido analogue of 1, ((n)Bu(4)P)[PtCl(3)(C(2)H(4))] (1(Cl)), have been investigated experimentally by both IR and Raman spectroscopy, and theoretically by geometry optimization and normal-mode analysis by the DFT approach. An analysis of the normal modes of coordinated ethylene in compounds 1, 1(Cl), 2, and 3 followed by a potential energy distribution investigation shows extensive vibrational coupling between the nu(C=C) and delta(s)(CH(2)) A(1) modes in two bands at around 1510-1520 and 1230-1250 cm(-1), the latter one having greater nu(C=C) contribution. The rho(w)(CH(2)) A(1) mode, the contribution of which the above two bands is negligible, is responsible for a lower-frequency band at 995-1005 cm(-1). A complete vibrational analysis, backed up by the DFT calculations, has also been carried out on the Pt-Br stretching vibrations of the tetrabromido complex 4, the tribromido complexes 1 and 5, and the dibromido complexes 2, 3, and 6, and on the Pt-Cl vibrations of the analogous complex 1(Cl). The study illustrates the advantages of coupling high-level computations to the vibrational analyses to make unambiguous band assignments in IR and Raman spectroscopy.
CNRS, LCC (Laboratoire de Chimie de Coordination), Université de Toulouse, UPS, INPT, 205, route de Narbonne, F-31077 Toulouse, France.
Pavel A
PA
Dub
Oleg A
OA
Filippov
Natalia V
NV
Belkova
Mireia
M
Rodriguez-Zubiri
Rinaldo
R
Poli