Dimeric Ru(II) complexes Ru2(CO)4L2X4 (L = CO or PPh3; X = Cl or Br) have been found to catalyze the hydrolysis of silanes to produce hydrogen gas and silanols with turnover numbers in excess of 104 at room temperature. Deuteration and mass spectrometric studies have established that the hydrogen gas originates from one hydrogen atom from water and the other from silane. Ruthenium hydride intermediates have been detected in the NMR spectrum during the early stage of the reaction, while the FTIR spectra of more stable complexes such as Ru(CO)2(PPh3)(THF)Br2 and Ru(CO)2(PPh3)2(H)Br have been recorded upon completion of catalysis. A mechanism has been proposed to account for the ruthenium-catalyzed silane hydrolysis based on the experimental data.
Photolysis of CpMn(CO)3 in a hexane/water biphasic system has been shown to generate hydrogen peroxide and hydrogen in 40−50% yield. Photolysis of the title compound results in loss of a CO ligand followed by coordination of a water molecule. The initially formed CpMn(CO)2(H2O) intermediate was detected using time-resolved IR spectroscopy. The cyclopentadiene (CpH) monomer is generated as the major product, formed by the transfer of an H atom from the coordinated H2O solvent to the Cp ring. A simple mechanism for H2 generation is proposed on the basis of deuteration studies which demonstrate the production of D2 and CpD upon photolysis of CpMn(CO)3 in a hexane/D2O biphasic system.
The UV photolysis of CpMn(CO)3 with thiols at room temperature effected the following catalytic transformation: 2 RSH → R2S2 + H2. This reaction is a cleaner and greener way toward making disulfides, as it produces dihydrogen as the only side-product. The manganese system exhibits high chemoselectivity as the transformation proceeds efficiently even in the presence of numerous functional groups. A manganese dicarbonyl complex, CpMn(CO)2RSH, and cyclopentadiene have also been detected using FTIR and NMR spectroscopic techniques, respectively. Based on our experimental data, a mechanism has been proposed to account for the catalysis.
The UV−visible photolysis of CpMn(CO) 3 in methanol generates CpMn(CO) 2 (CH 3 OH), which upon H atom abstraction using either O 2 , dpph, or H 2 O 2 gives the CpMn(CO) 2 (CH 3 O) radical complex. The radical with a lifetime of 10 to 20 min has been mainly characterized using FTIR and ESR spectroscopy and chemical oxidation studies. Together with density functional theory calculations, it is shown that the O−H bond is significantly weakened in the CpMn(CO) 2 (CH 3 OH) complex compared to free methanol. NBO spin density analysis suggests that the bond cleavage is facilitated by the formation of the CpMn(CO) 2 (CH 3 O) radical in which the electron spin is localized at the metal center rather than at the oxygen atom.
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