185221-92-5Relevant academic research and scientific papers
Synthesis of alkyl- and aryl[hydrotris(pyrazolyl)borato]carbonylruthenium complexes by decarbonylation of alcohols. Synthesis of TpRuH(H2)(PPh3) [Tp = hydrotris(pyrazolyl)borate], an observable intermediate in the decarbonylation reaction
Chen, Yu-Zhong,Chan, Wai Chung,Lau, Chak Po,Chu, Hei Shing,Lee, Hin Ling,Jia, Guochen
, p. 1241 - 1246 (1997)
Treatment of TpRuCl(PPh3)(CH3CN) (Tp = hydrotris(pyrazolyl)borate) with NaBH4 in ethanol did not yield the expected hydride complex TpRuH(PPh3)(CH3CN) (2) but rather the methyl carbonyl complex TpRu(CH3)(CO)(PPh3) (1b). Formation of Ib was due to decarbonylation of ethanol by 2 generated in situ by NaBH4 reduction of TpRuCl(PPh3)(CH3-CN). Analogous reactions in the presence of other primary alcohols RCH2OH (R = H, C2H5, n-C3H5, C6H5, C6H4CH3-4, and C6H4Cl-4) led to the corresponding σ-organyl complexes TpRuR(CO)(PPh3). A common feature of the reactions is that the R groups of alcohols RCH2-OH become the σ-organyl groups in the final metal complexes. A mechanism involving metal-η2-aldehyde and -η2-dihydrogen intermediates is proposed for the decarbonylation reaction. This is supported by the observation of the η2-dihydrogen complex TpRuH(H2)-(PPh3) (3) during the decarbonylation reaction. 3 was synthesized independently by heating a THF solution of 2 under 40 atm of H2 at 60 °C for 48 h or by heating 2 in CH3OH at 60 °C under 6 atm of H2 for 5-6 h.
Syntheses and characterization of hydrotris(1-pyrazolyl)borate dihydrogen complexes of ruthenium and their roles in catalytic hydrogenation reactions
Chan, Wai-Chung,Lau, Chak-Po,Chen, Yu-Zhong,Fang, Yi-Qun,Ng, Siu-Man,Jia, Guochen
, p. 34 - 44 (1997)
A series of new hydrotris(1-pyrazolyl)borate complexes of ruthenium were synthesized. Reaction of RuCl(HB(pz)3)(PPh3)2 with NaBH4 in ethanol produced the yellow monohydride complex RuH(HB(pz)3)(PPh3)2. Protonation of the monohydride complex RuH(HB(pz)3)-(PPh3)2 with HBF4·Et2O in dichloromethane gave the molecular dihydrogen complex [Ru-(HB(pz)3)(PPh3)2(H2)]BF 4. Reactions of the dihydrogen complex [Ru(HB(pz)3)(PPh3)2(H2)]BF 4 with L (L = CH3CN, H2O, N2) produced the adducts [Ru(HB(pz)3)(PPh3)2(L)]BF4. The dihydrogen complex [Ru(HB(pz)3)(PPh3)2(H2)]BF 4 could be regenerated by reactions of [Ru-(HB(pz)3)(PPh3)2(L)]BF4 (L = CH3CN, H2O) with pressurized H2. Deprotonation of the molecular dihydrogen complex [Ru(HB(pz)3)(PPh3)2(H2)]BF 4 occurred with NEt3 or H2O under hydrogen pressure. Treatment of RuCl(HB(pz)3)(PPh3)2 with LiBF4 in acetonitrile produced the bis-solvento complex [Ru(HB(pz)3)(PPh3)(CH3CN)2]BF 4. Heating a THF/CH3CN (9/1) solution of RuCl(HB(pz)3)(PPh3)2 at 60 °C led to the formation of RuCl(HB(pz)3)(PPh3)(CH3-CN). Reaction of RuCl(HB(pz)3)(PPh3)(CH3CN) with NaBH4 in THF produced the yellow monohydride complex RuH(HB(pz)3)(PPh3)(CH3CN). Acidification of the monohydride with HBF4·Et2O yielded [Ru(HB(pz)3)(PPh3)(CH3CN)(H 2)]BF4. Both complexes [Ru(HB(pz)3)-(PPh3)2(CH3CN)]BF 4 and [Ru(HB(pz)3)(PPh3)(CH3CN)2]BF 4 were found to be active catalysts for the hydrogenation of olefins in either anhydrous or hydrous THF. Enhanced catalytic activities were observed in the presence of water or NEt3. In addition, deuterium was incorporated into the catalytic hydrogenation products when D2O was present in the reaction mixture. The enhanced catalytic activity in the presence of water, and incorporation of deuterium in the hydrogenation products, could be best explained with mechanisms which involve dihydrogen complexes.
Experimental and theoretical studies of highly fluxional TpRu(PPh3) H2SiR3 complexes (Tp = hydridotris(pyrazolyl)borate)
Ng, Siu Man,Lau, Chak Po,Fan, Man-Fai,Lin, Zhenyang
, p. 2484 - 2490 (2008/10/08)
Reactions 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-HbSiR 3) - TpRu(PPh3)(Hb)(η2-HaSiR 3). 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/mol). Together with the experimental findings, a mechanistic cycle is proposed. The complexes TpRu(PPh3)(H)(η2-HSiR3) react reversibly with pressurized H2, CH3CN, and PPh3 to give TpRuH(H2)(PPh3), TpRuH(CH3CN)(PPh3), and TpRuH(PPh3)2, respectively.
