The influence of N-heterocyclic carbenes (NHC) on the reactivity of [Ru(NHC)(4)H](+) with H(2), N(2), CO and O(2).
The influence of N-heterocyclic carbenes (NHC) on the reactivity of [Ru(NHC)(4)H](+) with H(2), N(2), CO and O(2).
复制标题
N-杂环卡宾 (NHC) 对 [Ru(NHC)(4)H]( ) 与 H(2)、N(2)、CO 和 O(2) 反应性的影响。
DOI:
10.1002/chem.200901736
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发表时间:
2009
期刊:
影响因子:
--
通讯作者:
Burling S
中科院分区:
文献类型:
--
作者:
Burling S
The five‐coordinate ruthenium N‐heterocyclic carbene (NHC) hydrido complexes [Ru(IiPr2Me2)4H][BArF4] (1; IiPr2Me2=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene; ArF=3,5‐(CF3)2C6H3), [Ru(IEt2Me2)4H][BArF4] (2; IEt2Me2=1,3‐diethyl‐4,5‐dimethylimidazol‐2‐ylidene) and [Ru(IMe4)4H][BArF4] (3; IMe4=1,3,4,5‐tetramethylimidazol‐2‐ylidene) have been synthesised following reaction of [Ru(PPh3)3HCl] with 4–8 equivalents of the free carbenes at ambient temperature. Complexes1–3have been structurally characterised and show square pyramidal geometries with apical hydride ligands. In both dichloromethane or pyridine solution,1and2display very low frequency hydride signals at aboutδ−41. The tetramethyl carbene complex3exhibits a similar chemical shift in toluene, but shows a higher frequency signal in acetonitrile arising from the solvent adduct [Ru(IMe4)4(MeCN)H][BArF4],4. The reactivity of1–3towards H2and N2depends on the size of the N‐substituent of the NHC ligand. Thus,1is unreactive towards both gases,2reacts with both H2and N2only at low temperature and incompletely, while3affords [Ru(IMe4)4(η2‐H2)H][BArF4] (7) and [Ru(IMe4)4(N2)H][BArF4] (8) in quantitative yield at room temperature. CO shows no selectivity, reacting with1–3to give [Ru(NHC)4(CO)H][BArF4] (9–11). Addition of O2to solutions of2and3leads to rapid oxidation, from which the RuIIIspecies [Ru(NHC)4(OH)2][BArF4] and the RuIVoxo chlorido complex [Ru(IEt2Me2)4(O)Cl][BArF4] were isolated. DFT calculations reproduce the greater ability of3to bind small molecules and show relative binding strengths that follow the trend CO ≫ O2> N2> H2.
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DOI:
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发表时间:
1978
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1991
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2001
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