Dihydrogen as a Reactant in the Photochemistry of Bimetallic Cyclopentadienyl Carbonyl Compounds

Bitterwolf, Thomas E.; Linehan, and John C.; Shade, Joyce E.

doi:10.1021/om000292c

Cited by 22 publications

(23 citation statements)

References 16 publications

(17 reference statements)

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“…[68] Aspects of the dimerisation mechanism have been subsequently questioned. [69] The rhodium analogue of 19, complex 51, can be formed by addition of H 2 to 50. Interestingly, complex 51 does not lose H 2 readily on standing, nor does it exchange with D 2 appreciably after one week.…”

Section: Photochemically Reversiblementioning

confidence: 99%

Reversible Binding of Dihydrogen in Multimetallic Complexes

Weller

McIndoe

2007

Eur J Inorg Chem

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The interaction of hydrogen with metal surfaces is one of the most important and fundamental processes in the chemical industry. Hydrogen is also strongly tipped to play a central role in new challenges that are emerging in terms of climate change and energy supply, and the reversible binding of H 2 to suitable materials will play a keystone role in the realisation of the hydrogen economy. The reversible interaction of hydrogen with multimetallic centres is also an important theme in biological processes; the role of hydrogenases in the metabolism of H 2 is an example. Thus the reversible interaction of H 2 with multimetallic metal complexes is an area that spans considerable breadth. This review is concerned

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Section: Photochemically Reversiblementioning

confidence: 99%

Reversible Binding of Dihydrogen in Multimetallic Complexes

Weller

McIndoe

2007

Eur J Inorg Chem

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“…In contrast to nearly all other known metal carbonyl radicals, 10 this metal-centered radical does not cleanly dimerize back to the metal-metal bonded complex, but instead undergoes other reactions that appear to involve a C-H bond of the Cp ring. 11 When continuous photolysis (λ > 300 nm) of [Cp(CO) 2 Os] 2 is carried out in C 6 D 6 or THF-d 8 in the presence of excess 1,4-cyclohexadiene, the osmium hydride Cp(CO) 2 OsH forms in 83-88% yield, together with benzene (eq 1). Photochemical homolysis of the Os-Os bond provides Cp(CO) 2 Os • (eq 2), an osmiumcentered radical that abstracts a hydrogen atom from cyclohexadiene, giving Cp(CO) 2 OsH and the cyclohexadienyl radical (eq 3).…”

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confidence: 99%

Carbon-to-Metal Hydrogen Atom Transfer: Direct Observation Using Time-Resolved Infrared Spectroscopy

et al. 2005

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We report the direct spectroscopic observation of hydrogen atom transfer reactions from carbon to metals, in which homolytic cleavage of a C-H bond is accomplished at a single metal center. Laser flash photolysis (355 nm) of a solution of [Cp(CO)2Os]2 leads to homolysis of the Os-Os bond and formation of the osmium-centered radical, Cp(CO)2Os*, as observed by time-resolved infrared (TRIR) spectroscopy. DFT computations on Cp(CO)2Os* support this assignment. Continuous photolysis (lambda > 300 nm) of [Cp(CO)2Os]2 in the presence of excess 1,4-cyclohexadiene produces the osmium hydride Cp(CO)2OsH. The kinetics of this carbon-to-metal hydrogen atom transfer were examined by TRIR spectroscopy. The second-order rate constant for hydrogen atom transfer from 1,4-cyclohexadiene to Cp(CO)2Os* in hexane at 23 degrees C is kH = (2.1 +/- 0.2) x 106 M-1 s-1. The pKa of Cp(CO)2OsH was determined as 32.7 in CH3CN, and use of a thermochemical cycle provided an estimated lower limit of 82 kcal/mol for the Os-H bond dissociation energy, indicating that it is an exceptionally strong M-H bond. Photolysis of [Tp(CO)2Os]2 (Tp = hydridotris(pyrazolyl)borate) results in carbon-to-metal hydrogen atom transfers from even stronger C-H bonds (THF or toluene) and produces Tp(CO)2OsH.

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“…Experimentally, few ruthenium carbene complexes exhibit hindered rotation. 7 Complex 4 reacts with PhC᎐ ᎐ ᎐ CH and adventitious H 2 O to produce the carbonyl complex 8 (Scheme 2) by nucleophilic attack of H 2 O on a vinylidene intermediate according to a Ru(1)-P(1), 2.359(4); Ru(1)-P(2), 2.347(4); Ru(1)-P(3), 2.362(4); Ru(1)-C(average), 2.238 (15); P(1)-Ru(1)-P(2), 94.33 (13); P(1)-Ru(1)-P(3), 95.021 (14); P(2)-Ru(1)-P(3), 95.41 (13). D a l t o n T r a n s .…”

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confidence: 99%