Chemistry of the 17-electron compound [(.eta.5-C5Me5)Cr(CO)3]

Jaeger, Tilman; Baird, Michael C.

doi:10.1021/om00099a035

Cited by 40 publications

(65 citation statements)

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“…Solution samples for optical experiments were prepared on a vacuum line in sealable cuvettes; those for photophysical measurements were degassed by at least five freeze-pump-thaw cycles and sealed under purified nitrogen. Transient-absorption spectroscopic experiments were performed using λ ≥ 670-nm probe light to ensure that transient 1a• and 1b• were not irradiated, because they are reported to be photosensitive (37).…”

Section: Methodsmentioning

confidence: 99%

Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore

Porte

Moravec

Hopkins

2014

Proc. Natl. Acad. Sci. U.S.A.

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Energy-storing artificial-photosynthetic systems for CO 2 reduction must derive the reducing equivalents from a renewable source rather than from sacrificial donors. To this end, a homogeneous, integrated chromophore/two-catalyst system is described that is thermodynamically capable of photochemically driving the energy-storing reverse water-gas shift reaction (CO 2 + H 2 → CO + H 2 O), where the reducing equivalents are provided by renewable H 2 . The system consists of the chromophore zinc tetraphenylporphyrin (ZnTPP), H 2 oxidation catalysts of the form [Cp R Cr(CO) 3 ] -, and CO 2 reduction catalysts of the type Re(bpy-4,4′-R 2 )(CO) 3 Cl. Using time-resolved spectroscopic methods, a comprehensive mechanistic and kinetic picture of the photoinitiated reactions of mixtures of these compounds has been developed. It has been found that absorption of a single photon by broadly absorbing ZnTPP sensitizes intercatalyst electron transfer to produce the substrate-active forms of each. The initial photochemical step is the heretofore unobserved reductive quenching of the low-energy T 1 state of ZnTPP. Under the experimental conditions, the catalytically competent state decays with a second-order half-life of ∼15 μs, which is of the right magnitude for substrate trapping of sensitized catalyst intermediates.artificial photosynthesis | catalysis | dual catalysis | photoredox | photocatalysis T he inexorable growth of global energy consumption and concern over its attendant environmental consequences has spurred considerable research into developing means to store solar energy in the form of renewable chemical fuels (1, 2). Among the potential feedstocks for these solar fuels, CO 2 is a desirable target because it is the end product of the combustion of fossil fuels. Thus, developing solar-driven mechanisms for chemically reducing CO 2 to energy-rich products holds the potential to recycle conventional fuels and mitigate their carbon impact (3-7).Numerous studies over the past 30 y have investigated homogeneous artificial-photosynthetic systems for CO 2 reduction, in which a photoexcited chromophore accomplishes the transfer of electrons from a source of reducing equivalents to a CO 2 reduction catalyst (8-14). With very rare exceptions (15), the reducing equivalents consumed in these photochemical CO 2 reduction reactions have been supplied by sacrificial electron donors. These reagents are used because their prompt decomposition following photoinitiated oxidation suppresses unproductive back-electron-transfer pathways, which are generally fast compared with substrate transformation, and because their decomposition products can provide additional reducing equivalents needed for some CO 2 reduction reactions, thus circumventing the one-photon/one-electron limit of molecular photosensitizers. Offsetting these practical advantages, however, is the fact that the stoichiometric consumption of conventional sacrificial donors in these reactions negates their energy-storing potential. In order for homogeneous systems to drive ...

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Section: Methodsmentioning

confidence: 99%

Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore

Porte

Moravec

Hopkins

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…There are two general methods for the synthesis of [M 2 (CO) 6 Cp 2 ] (1). Reaction of the metal hexacarbonyl with lithium or sodium cyclopentadienide in diglyme or THF followed by oxidation with iron(III) salts (method A) gives excellent yields for all three metals (60-85% for Cr, 90-98% for Mo and W).…”

Section: (I) Synthesismentioning

confidence: 99%

“…Reaction of the metal hexacarbonyl with lithium or sodium cyclopentadienide in diglyme or THF followed by oxidation with iron(III) salts (method A) gives excellent yields for all three metals (60-85% for Cr, 90-98% for Mo and W). 3 The direct thermolysis of the cyclopentadiene with [M(CO) 6 ] or more commonly [M(CO) 3 (NCMe) 3 ] (method B) can also give good yields under controlled conditions. 4 For [Cr 2 (CO) 6 Cp 2 ] and its Cp* analogue, dehydrogenation of the intermediate [CrH(CO) 3 Cp] with isoprene gives the best yield, 5 ' 6 and a related procedure for [Mo 2 (CO) 6 Cp* 2 ] with cyclohexadiene also exists.…”

Section: (I) Synthesismentioning

confidence: 99%

“…3 The direct thermolysis of the cyclopentadiene with [M(CO) 6 ] or more commonly [M(CO) 3 (NCMe) 3 ] (method B) can also give good yields under controlled conditions. 4 For [Cr 2 (CO) 6 Cp 2 ] and its Cp* analogue, dehydrogenation of the intermediate [CrH(CO) 3 Cp] with isoprene gives the best yield, 5 ' 6 and a related procedure for [Mo 2 (CO) 6 Cp* 2 ] with cyclohexadiene also exists. 7 [W 2 (CO) 6 Cp 2 ] has also been prepared by thermolysis of [W(CO) 3 (CH 2 Ph)Cp], with [W 2 (CO) 6 (ufulvalene)] appearing as a by-product.…”

Section: (I) Synthesismentioning

confidence: 99%

“…4 For [Cr 2 (CO) 6 Cp 2 ] and its Cp* analogue, dehydrogenation of the intermediate [CrH(CO) 3 Cp] with isoprene gives the best yield, 5 ' 6 and a related procedure for [Mo 2 (CO) 6 Cp* 2 ] with cyclohexadiene also exists. 7 [W 2 (CO) 6 Cp 2 ] has also been prepared by thermolysis of [W(CO) 3 (CH 2 Ph)Cp], with [W 2 (CO) 6 (ufulvalene)] appearing as a by-product. 8 I n a n interesting development, T y l e r a n d co-workers have p r e p a r e d oligomeric u r e t h a n e s containing Mo 2 (CO) 6 6 Cp* 2 ].…”

Section: (I) Synthesismentioning

confidence: 99%

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Cyclopentadienyl Complexes of Chromium, Molybdenum and Tungsten

Morris

1995

Comprehensive Organometallic Chemistry II

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C−S Bond Cleavage and C−C Coupling in Cyclopentadienylchromium Complexes To Give the First Dithiooxamide-Bridged and Doubly Dithiocarbamate-Bridged Double Cubanes: [Cp6Cr8S8{(C(S)NEt2)2}] and [Cp6Cr8S8(S2CNEt2)2]

et al. 2001

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There have been extensive studies on the use of the dithiocarbamate ligand in a variety of bonding modes for stabilizing a wide range of oxidation states in coordination compounds of main-group and transition metals. [1] Although generally unreactive in the majority of its complexes, this ligand can undergo CÀS bond cleavage, a phenomenon first observed in a Mo complex in 1972 and becoming increasingly common in the last two decades. [2] In most cases, the cleaved S atom takes on a distinctly different coordination role in the complex, except where it is abstracted by an S acceptor such as PEt 3 . [2c] For example, the cleaved S atom can assume a bridging mode (M-S-M), [2a,b,f, 3] form an MS bond, [2d,g] or interact with a neighboring ligand (e.g., the MC bond of a coordinated alkyne). [2e] Cleavage of both CÀS bonds of the ligand was reported for reactions with [Ru 3 (CO) 12 ] [2h] and [Mo 2 (m-O 2 CMe) 4 ]. [3] Other reactions of the dithiocarbamate ligand include oxidative addition of a C À S bond to alkynes [4] and coupling reactions with coordinated alkyne, [2c, 5] alkylidene, [6] vinylidene/allenylidene, [7] and cyanide [8] ligands. Most of these studies involved Mo and W complexes, except for a few examples containing Cu, [4d] Nb and Ta, [2g] and Ru. [2h, 7] In the course of our investigations on the reactivity of [{CpCr(CO) 3 } 2 ] (Cp h 5 -C 5 H 5 ) towards the EÀE bonds of organic substrates such as diphenyl dichalcogenides Ph 2 E 2 (E S, Se, Te), [9] and bis(diphenylthiophosphinyl)disulfane [Ph 2 P(S)S] 2 , [10] we studied reactions with tetraalkylthiuram disulfides [R 2 NC(S)S] 2 , and here we report the first organochromium complexes containing dithiocarbamate and dithiooxamide ligands.The instantaneous reaction of [{CpCr(CO) 3 } 2 ] with one molar equivalent of tetraethylthiuram disulfide [Et 2 NC(S)S] 2 in toluene at ambient temperature gave a dark red solution, which upon concentration yielded air-stable deep red crystals of [CpCr(CO) 2 (S 2 CNEt 2 )] (1) in 87 % yield. A similar reaction at 90 8C for 2 h gave a dark brown mixture, from which were obtained, in order of elution from a silica gel column, the following compounds: [{CpCr(CO) 2 } 2 S] (7) as a dark green solid (ca. 1 % yield), (1) (22 % yield), [CpCr(CO) 2 (SCNEt 2 )] (2) as a dark red crystalline solid (11 % yield), [Cp 4 Cr 4 S 4 ] (3) as a dark solid (22 % yield), [Cp 6 Cr 8 S 8 {(C(S)NEt 2 ) 2 }] (4) as a brown solid (6.8 % yield), suggests stable trap site for the hole, the position of which is not far from the acceptor. The slow recombination of the geminate ion pair with the relatively short distance would be related to the trap-site structure or some sorts of reorganizations because of the charge shift in the PVCz film.

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Chemistry of the 17-electron compound [(.eta.5-C5Me5)Cr(CO)3]

Cited by 40 publications

References 2 publications

Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore

Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore

Cyclopentadienyl Complexes of Chromium, Molybdenum and Tungsten

C−S Bond Cleavage and C−C Coupling in Cyclopentadienylchromium Complexes To Give the First Dithiooxamide-Bridged and Doubly Dithiocarbamate-Bridged Double Cubanes: [Cp6Cr8S8{(C(S)NEt2)2}] and [Cp6Cr8S8(S2CNEt2)2]

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Chemistry of the 17-electron compound [(.eta.5-C5Me5)Cr(CO)3]

Cited by 40 publications

References 2 publications

Electron-transfer sensitization of H 2 oxidation and CO 2 reduction catalysts using a single chromophore

Electron-transfer sensitization of H 2 oxidation and CO 2 reduction catalysts using a single chromophore

Cyclopentadienyl Complexes of Chromium, Molybdenum and Tungsten

C−S Bond Cleavage and C−C Coupling in Cyclopentadienylchromium Complexes To Give the First Dithiooxamide-Bridged and Doubly Dithiocarbamate-Bridged Double Cubanes: [Cp6Cr8S8{(C(S)NEt2)2}] and [Cp6Cr8S8(S2CNEt2)2]

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Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore

Electron-transfer sensitization of H ₂ oxidation and CO ₂ reduction catalysts using a single chromophore