156958-63-3Relevant academic research and scientific papers
RuHX(CO)(PR3)2: Can vCO be a probe for the nature of the Ru-X bond?
Poulton, Jason T.,Sigalas, Michael P.,Folting, Kirsten,Streib, William E.,Eisenstein, Odile,Caulton, Kenneth G.
, p. 1476 - 1485 (2008/10/08)
The relative electron-donating ability of X in the new five-coordinate RuHX(CO)(PtBu2Me)2 (X = I, Br, Cl, F, OPh, OH, OCH2CF3, OEt, OCPh3, OB(Mesityl)2, OSiR3, NHPh, SPh, C2Ph) has been evaluated based on the CO stretching frequency. In all cases, the CO frequency is lower than that of the free CO and the reduction increases in the order I π) interactions are two-orbital/four-electron ones and thus are net destabilizing. However, the CO π* orbitals interact to stabilize the Ru-X π* orbital, thereby retaining some degree of net Ru-X π bonding. The structure of RuH(OSiPh3)(CO)(PtBu2Me)2 is shown to be square pyramidal with H at the apical site of the pyramid and the siloxy group trans to CO. EHT and core-potential ab initio calculations (full optimization at the HF and partial optimization at the MP2 level) have been performed to determine the structure of RuHX(CO)(PH3)2 (X = F, Cl, OH, OCH3, OSiH3 with d orbitals on the Si atom). The square pyramid is preferred for all X. This structure permits optimal push-pull effects between the π-donating X group and the π* of CO. The CO frequency has been calculated at the MP2 level, and the ranking is identical to the experimental ones, π effects are shown to be larger for alkoxy than for halide, but the variation in π-effects alone is not sufficient to account for the ranking of the CO frequencies down a column of the periodic table; the σ effect is also involved. In particular, it is shown that strongly ionic Ru-X bonds lead to lower CO frequency. This last effect causes large changes in the 19F chemical shift for RuH(F)(CO)(PtBu2Me)2 species upon adding a sixth ligand to Ru. It also causes strong hydrogen bonding of fluoride to added alcohol. In spite of Ru/X multiple bonding in the five-coordinate species, they are Lewis acidic toward amines and phosphines. Crystal data for RuH(OSiPh3)(CO)(PtBu2Me)2 at -160°C: a = 11.263(1) A?, b = 31.713(4) A?, c = 22.311(3) A?, and β = 100.07(0)° with Z = 4 in space group P21/n.
