Photoinduced rearrangements of ring-coupled bis(cyclopentadienylrutheniumdicarbonyl) compounds of the form Ru2(CO)4(η5,η5-C5H4LC5H4) (L  CHn2-, (CH3)2C-, C2H4- and (CH3)2S-) The molecular structure of [Ru(CO)2][Ru(CO)2Cl](η5,η5:η1-C5H4CH2C5H3)

Bitterwolf, Thomas E.; Shade, Joyce E.; Hansen, Julie A; Rheingold, Arnold L.

doi:10.1016/0022-328x(95)06018-r

Cited by 35 publications

(27 citation statements)

References 13 publications

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“…[7a] The finding that CCl 4 as a solvent does not affect this step may simply be due to noncompetitive intermolecular trapping kinetics at room temperature. [20] This extraordinary labilization of the normally strong Fv linkage by the homolysis of a metalÀmetal bond has been an unrecognized feature in this class of compounds.…”

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confidence: 99%

Mechanism of Thermal Reversal of the (Fulvalene)tetracarbonyldiruthenium Photoisomerization: Toward Molecular Solar–Thermal Energy Storage

et al. 2010

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In the currently intensifying quest to harness solar energy for the powering of our planet, most efforts are centered around photoinduced generic charge separation, such as in photovoltaics, water splitting, other small molecule activation, and biologically inspired photosynthetic systems.1 In contrast, direct collection of heat from sunlight has received much less diversified attention, its bulk devoted to the development of concentrating solar thermal power plants, in which mirrors are used to focus the sun beam on an appropriate heat transfer material.2 An attractive alternative strategy would be to trap solar energy in the form of chemical bonds, ideally through the photoconversion of a suitable molecule to a higher energy isomer, which, in turn, would release the stored energy by thermal reversal. Such a system would encompass the essential elements of a rechargeable heat battery, with its inherent advantages of storage, transportability, and use on demand. 3 The underlying concept has been explored extensively with organic molecules (such as the norbornadiene-quadricyclane cycle), 4 often in the context of developing photoswitches. 5 On the other hand, organometallic complexes have remained relatively obscure in this capacity, 6 despite a number of advantages, including expanded structural tunability and generally favorable electronic absorption regimes. A highly promising organometallic system is the previously reported, robust photo-thermal fulvalene (Fv) diruthenium couple 1!2 (Scheme 1).7 However, although reversible and moderately efficient, lack of a full, detailed atom-scale understanding of its key conversion and storage mechanisms have limited our ability to improve on its performance or identify optimal variants, such as substituents on the Fv, ligands other than CO, and alternative metals. Here we present a theoretical investigation, in conjunction with corroborating experiments, of the mechanism for the heat releasing step of 2!1 and its Fe (4) and Os (6) For the mechanism of the conversion of 2 to 1, our calculations reveal an enthalpy (neglecting the small temperature dependence) of 20.8 kcal mol -1 , in excellent agreement with experiment, 19.8±1.4 kcal mol -1 . 7,12 This value corresponds to an energy density of ~0.2 MJ/kg, comparable to that of lithium ion batteries, ~0.5 MJ/kg. Analyzing the computed MEP, a two step process was uncovered, in which 2 rearranges by initial Cp-Cp coupling via TS A to deliver biradical intermediate B, which in turn proceeds through TS C to 1 (Figure 1). The underlying energetics are depicted in Figure 2. Proceeding along this reaction coordinate, the first step defines a preequilibrium and involves an unusual TS structure (A), 22.4 kcal mol -1 above 2 (Figure 1). It can be viewed as a pseudo-triple decker complex, in which the bridging Fv ligand contains two nearly planar Cp halves twisted by 46.3° with respect to each other. The nascent C-C bond distance is 1.54 Å, elongated, but well on the way to that in B (1.43 Å). This connection, featuring two form...

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confidence: 99%

Mechanism of Thermal Reversal of the (Fulvalene)tetracarbonyldiruthenium Photoisomerization: Toward Molecular Solar–Thermal Energy Storage

et al. 2010

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“…complex 1 was obtained from the treatment of the permethylated dimethylsilyl-bridged ligand with 0.66 equiv. Ru 3 (CO) 12 in refluxing octane [Equation (1)]. [8,9] When the reaction according to Equation (1) was carried out under rigorously oxygen-free conditions, the 1 H NMR spectrum of the crude reaction mixture displayed, along with the signals of the major product 1, additional peaks for a C 2v symmetrical minor product.…”

Section: Resultsmentioning

confidence: 99%

“…[1] In the latter case, however, the reaction has been found to be more complicated, and competition between SiϪC and, in addition, CϪH activation of the cyclopentadienyl ring CϪH group in the position ortho to the bridgehead atom was noticed. The apparent difference be- tween the outcome of the photochemical reactions of complexes 1 and its unsubstituted congener 2 is best explained with a more difficult CϪH activation step (higher activation barrier) at the sp 3 -hybridized methyl group in 1, as compared to the aromatic CϪH group in 2; there is ample evidence for this in the literature.…”

Section: Photochemical Reaction Ofmentioning

confidence: 99%

“…[6] Recently, we have extended our research program to include the group 8 transition metals ruthenium and osmium. In the course of these studies, we observed facile, and quantitative, photochemically induced SiϪC bond cleavage in the dimethylsilylbridged permethylated complex Me 2 Si[(C 5 Me 4 )Ru(CO) 2 ] 2 (1). While this work was in progress, Bitterwolf et al reported similar results in the parent complex Me 2 Si[(C 5 H 4 )Ru(CO) 2 ] 2 (2), [7] which was shortly followed by an alternative synthesis for 2 and a short discussion on fluxionality in the parent compound by Zhou and coworkers.…”

Section: Introductionmentioning

confidence: 99%

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Photochemically Induced Silicon−Carbon Bond Cleavage in a Dimethylsilyl-Bridged Dicyclopentadienyl Diruthenium Complex

Fox

Burger

2001

Eur. J. Inorg. Chem.

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The synthesis and X‐ray crystal structure of the novel permethylated dimethylsilyl‐bridged diruthenium complex Me2Si[(C5Me4)Ru(CO)2]2 (1) is reported. The molecular structure displays a metal−metal bond of 2.7121(4) Å, which is supported by two symmetrical μ‐bridging CO groups and, in addition, two terminal carbonyl ligands. In solution, exchange of these carbonyl groups is observed, as shown by 13C NMR EXSY and VT IR‐measurements. It is suggested that the exchange process proceeds via the energetically disfavoured intermediate 1a, which displays four terminal CO ligands. This view is supported by density functional calculations, which indicate a C2‐symmetrical structure for 1a. Photochemically induced cleavage of the silicon−carbon and Ru−Ru bonds in 1 results in complex 3, which is thermodynamically uphill from 1 according to our DFT calculations. The molecular structure of complex 3 was unambiguously confirmed by X‐ray crystallography.

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“…The first example is the photochemically induced rearrangement of the diruthenium complex (η 5 ,η 5 -C 5 H 4 -C 5 H 4 )Ru 2 (CO) 4 with directly linked Cp rings, reported by Vollhardt and coworkers, which could be thermally reversed (eq 1). 6 Another example is the photochemical rearrangement of the siliconbridged diruthium complexes (η 5 ,η 5 -C 5 R 4 SiMe 2 C 5 R 4 )Ru 2 (CO) 4 , reported first by Bitterwolf and co-workers as a side process and developed later by Burger into the clean reaction (eq 2).…”

Section: Introductionmentioning

confidence: 97%

Synthesis and Properties of Structural Variants of the Si−Si Bridged Bis(cyclopentadienyl)tetracarbonyldiiron Complexes: Modification on the Bridge

Sun

Liu

et al. 2008

Organometallics

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A series of new structural variants of the Si-Si bridged bis(cyclopentadienyl)tetracarbonyldiiron complex (η 5 ,η 5 -C 5 H 4 XC 5 H 4 )Fe 2 (CO) 4 , where X ) MeSi[µ-(CH 2 ) 4 ]SiMe (3), CH 2 SiMe 2 (7), and SiMe 2 SiPh 2 (10), were synthesized and their properties studied with emphasis on the thermal rearrangement that had been demonstrated to occur when X ) SiMe 2 SiMe 2 . It was found that the presence of the cyclic structure on the Si-Si bridge for complex 3 prohibited the thermal rearrangement, but oxygen insertion into the Si-Si bond took place under thermal conditions to give the new Si-O-Si bridged complex {η 5 ,η 5 -C 5 H 4 MeSi(µ-O)[µ-(CH 2 ) 4 ]SiMeC 5 H 4 }Fe 2 (CO) 4 (4). Using CH 2 SiMe 2 as the bridging group in complex 7 also resulted in failure of the rearrangement because the C-Si bond could not be activated by the iron center. Complex 10, with the unsymmetric bridging group SiMe 2 SiPh 2 , underwent thermal rearrangement, producing the expected product cyclic-[(Me 2 Si-η 5 -C 5 H 4 )Fe(CO) 2 (Ph 2 Si-η 5 -C 5 H 4 )Fe(CO) 2 ]-( 11) with two Si-Fe bonds. When the reaction was performed in the presence of P(OPh) 3 , incorporation of the phosphite ligand in the rearranged product took place, providing two regioisomers, cyclic-{(Me 2 Si-η 5 -C 5 H 4 )Fe(CO)[P(OPh) 3 ](Ph 2 Si-η 5 -C 5 H 4 )Fe(CO) 2 }-(12a) and cyclic-{(Me 2 Si-η 5 -C 5 H 4 )Fe(CO) 2 (Ph 2 Si-η 5 -C 5 H 4 )Fe(CO)[P(OPh) 3 ]}-(12b), in a 1:1.8 ratio. The reaction of 10 with I 2 led to Fe-Fe bond cleavage, affording di-iodide (η 5 ,η 5 -C 5 H 4 Me 2 SiSiPh 2 C 5 H 4 )[Fe(CO) 2 I] 2 (13). The molecular structures of 3, 4, 7, 10, 11, and 13 have been determined by X-ray diffraction methods.

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Photoinduced rearrangements of ring-coupled bis(cyclopentadienylrutheniumdicarbonyl) compounds of the form Ru2(CO)4(η5,η5-C5H4LC5H4) (L  CHn2-, (CH3)2C-, C2H4- and (CH3)2S-) The molecular structure of [Ru(CO)2][Ru(CO)2Cl](η5,η5:η1-C5H4CH2C5H3)

Cited by 35 publications

References 13 publications

Mechanism of Thermal Reversal of the (Fulvalene)tetracarbonyldiruthenium Photoisomerization: Toward Molecular Solar–Thermal Energy Storage

Mechanism of Thermal Reversal of the (Fulvalene)tetracarbonyldiruthenium Photoisomerization: Toward Molecular Solar–Thermal Energy Storage

Photochemically Induced Silicon−Carbon Bond Cleavage in a Dimethylsilyl-Bridged Dicyclopentadienyl Diruthenium Complex

Synthesis and Properties of Structural Variants of the Si−Si Bridged Bis(cyclopentadienyl)tetracarbonyldiiron Complexes: Modification on the Bridge

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