Experimental and Theoretical Studies of Highly Fluxional TpRu(PPh 3 )“H 2 SiR 3 ” Complexes (Tp = Hydridotris(pyrazolyl)borate)
1999; American Chemical Society; Volume: 18; Issue: 13 Linguagem: Inglês
10.1021/om980830+
ISSN1520-6041
AutoresSM Ng, Chak Po Lau, Man-Fai Fan, Zhenyang Lin,
Tópico(s)Organoboron and organosilicon chemistry
ResumoReactions of TpRuH(CH3CN)(PPh3) with free silanes HSiR3 (R3 = Et3, (EtO)3, Ph3, HEt2, HPh2, and H2Ph) in THF yield the complexes TpRu(PPh3)(H)(η2-HSiR3), the formulation of which is inferred from NMR spectroscopic data. The chemical equivalence of the two hydrogen atoms of TpRu(PPh3)(H)(η2-HSiR3) down to −100 °C is attributed to rapid fluxionality between the two, i.e., TpRu(PPh3)(Ha)(η2-HbSiR3) ⇋ TpRu(PPh3)(Hb)(η2-HaSiR3). Molecular orbital calculations at the B3LYP level have been performed to investigate the stereochemistry and the interconversion processes of various structural isomers for TpRu(PPh3)(H)(η2-HSiR3). The results further support the existence of a η2-silane formulation for these complexes. Two stable structures, with a nonclassical η2-silane ligand, have been found. These two structural isomers are found to be in equilibrium with a low reaction barrier (7.5 kcal/mol). The interconversion between the enantiomeric pair of the most stable structure has almost no reaction barrier (0.5 kcal/mo...
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