VIBRATIONAL AND SOLID-STATE P-31 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPIC STUDIES OF 1 1 COMPLEXES OF PPH(3) WITH GOLD(I) HALIDES - CRYSTAL-STRUCTURE OF [AUBR(PME(3))]/

The crystal structure of [AuBr(PMe(3))], like that of the correspondin g chloride, was found to consist of three crystallographically indepen dent molecules linked through weak Au Au contacts to form helical chai ns. The Au ... Au distances [3.648(1), 3.980(2), 3.548(2) Angstrom] ar e, however, significantly longer than in the chloro- and iodo-complexe s, implying that the Au ... Au interaction is weakest in the bromide. The far-IR and Raman spectra of [AuX(PMe(3))] (X=Cl, Br or I) have bee n measured, and assignments made for the bands observed. The spectra w ere analysed to see whether they show any effects of the weak Au ... A u bonding evident in the crystal structures. In particular, the low-wa venumber limit of previously reported Raman spectra for these species has been extended in order to search for v(Au-2) bands. The X=Cl or I compounds show a strong Raman band which can be assigned to the delta( PAuX) deformation, but no v(Au-2) bands were found in the region predi cted on the basis of recent assignments for such modes in other comple xes which display Au Au contacts of Similar length. possible reasons, including an interaction between v(Au-2) and delta(PAuX) modes, are di scussed. The solid-state cross polarization magic angle spinning P-31 NMR spectra of the chloride and iodide complexes consist of doublets d ue to the presence of (1)J(Au-197-(31)p) coupling. This is a rare obse rvation of spin-spin coupling between the spin I=1/2(31)P nucleus and the strongly quadrupole coupled Au-197 nucleus, and permits estimation of the (1)J((197)AU-(31)p) coupling constants for these complexes.