Hydrido{(acylphosphine)(diphenylphosphinous acid)}rhodium(III) Complexes. Catalysts for the Homogeneous Hydrolysis of Ammonia- or Amine-Boranes under Air

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• 作者：Virginia San Nacianceno ; Lourdes Ibarlucea ; Claudio Mendicute-Fierro ; Antonio Rodr铆guez-Di茅guez ; Jos茅 M. Seco ; Itziar Zumeta ; Carlos Ubide ; Mar铆a A. Garralda
• 刊名：Organometallics
• 出版年：2014
• 出版时间：November 10, 2014
• 年：2014
• 卷：33
• 期：21
• 页码：6044-6052
• 全文大小：545K
• ISSN：1520-6041

文摘

The reaction of [RhCl(COD)]₂ (COD = 1,5-cyclooctadiene) with PPh₂(o-C₆H₄CHO) (Rh/P = 1:1) in the presence of 4-methylpyridine (4-pic) or isoquinoline (iquin) leads to hydridoacyl complexes [RhHCl(PPh₂(o-C₆H₄CO))L₂] (L = 4-pic, 1; iquin, 2). Their reaction with diphenylphosphine oxide affords neutral complexes [RhHCl{(PPh₂(o-C₆H₄CO))(PPh₂O)H}L] (L = pyridine (py), 4; 4-pic, 5; iquin, 6) with trans P-ligands belonging to a formally PCP pincer ligand due to the formation of a O---H---O hydrogen bond between the oxygen atom of the diphenylphosphinous acid and the oxygen atom of the coordinated acyl. The reaction of 4 with chelating N-donors (LL) leads to displacement of pyridine and chloride to afford cationic [RhH{(PPh₂(o-C₆H₄CO))(PPh₂O)H}(LL)]BPh₄ (LL = 2,2鈥?bipyridine, 7; biacetyldihydrazone, 8; biacetyloximehydrazone, 9; 2-aminomethylpyridine, 10), which undergo cleavage of the O---H---O hydrogen bond in solution. Complex 9, containing a nonsymmetric ligand, exists in solution as an equimolar mixture of two isomers in equilibrium leading to fluxional behavior for which 螖G^{鈥?/sup> = 52 卤 1 kJ mol鈥? has been determined using the Eyring equation. The complexes were fully characterized spectroscopically. Single crystal X-ray diffraction analysis was performed on 8. Complexes 1鈥?b>10 have been tested as homogeneous catalysts for the hydrolysis of amine- or ammonia-borane (AB) to generate up to 3 equiv of hydrogen in the presence of air. When using 0.5 mol % loading of 5, at 40 掳C, complete hydrogen release from 0.46 M solutions of AB, TBAB (tert-butylamine-borane), and DMAB (dimethylamine-borane) requires 12.5, 9, or 15 min, respectively. The catalyst maintains its activity in consecutive runs. Kinetic studies indicate a first-order behavior in substrate in every case. The catalytic hydrolysis of AB shows first-order dependence on the catalyst concentration.}