Late transition-metal multiple bonding: Platinum phosphinidenes and ruthenium alkylidenes

Benson, Michael; Cundari, Thomas R.

doi:10.1002/(sici)1097-461x(1997)65:5<987::aid-qua61>3.0.co;2-r

Cited by 8 publications

(4 citation statements)

References 38 publications

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“…In many respects, TMMG hvy complexes, despite the amount of recent research, represent a virtually untapped resource for novel chemistry. Computations suggest that weaker π-bonding, although detracting from stability, may give TMMG hvy utility in synthetic transformations by providing a platform that is easily tunable through ligand/substituent modification . One area which is virtually unexplored, experimentally and computationally, is TMMG hvy species involving the later transition metals.…”

Section: Multiply Bonded Complexes In Inorganic and Organometallic Ch...mentioning

confidence: 99%

Computational Studies of Transition Metal−Main Group Multiple Bonding

2000

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Section: Multiply Bonded Complexes In Inorganic and Organometallic Ch...mentioning

confidence: 99%

Computational Studies of Transition Metal−Main Group Multiple Bonding

2000

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“…Given the huge experimental interest in the metathesis process, a number of theoretical studies have appeared in recent years. 19 Many of these have used small models of the catalyst system (e.g. with L = PH 3 ) to study its structure and reactivity.…”

Section: Introductionmentioning

confidence: 99%

Substituent effects and the mechanism of alkene metathesis catalyzed by ruthenium dichloride catalysts

2005

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Density functional theory calculations are reported concerning the dissociative mechanism for alkene metathesis by ruthenium dichloride catalysts, including both bisphosphine and diaminocarbene/phosphine complexes. The calculations use a hierarchy of models, ranging from [(L)(PH(3))Ru(Cl)(2)(CH(2))](L=PH(3) or diaminocarbene) through the larger [(L)(PMe(3))Ru(Cl)(2)(CHPh)] to the "real"[(L)(PCy(3))Ru(Cl)(2)(CHPh)]. Calculations show that the rate-limiting step for metathesis is either ring closing from an alkene complex to form a ruthena-cyclobutane, or ring-opening of the latter intermediate to form an isomeric alkene complex. The higher efficiency of the diaminocarbene based catalysts is due to the stabilization of the formal +iv oxidation state of the ruthenium centre in the metallacycle. This effect is partly masked in the smaller model systems due to a previously unnoticed stereoelectronic effect. The calculations do not reproduce the experimental observation whereby the initiation step, phosphine dissociation, is more energetically demanding and hence slower for the diaminocarbene-containing catalyst system than for the bisphosphine. Further calculations on the corresponding bond energies using a variety of DFT and hybrid DFT/molecular mechanics methods all find instead a larger phosphine dissociation energy for the bisphosphine catalyst. This reversed order of binding energies would in fact be the one expected based on the stronger trans influence of the diaminocarbene ligand. The discrepancy with experiment is small and could have a number of causes which are discussed here.

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“…To understand the chemistry of transition-metal complexes, it is necessary to consider the fundamental nature of the chemical bonding between the transition-metal and main-group elements. In the last few decades, there have been several reports about transition-metal−main-group bonds. ,− However, there have been few quantitative studies of the nature of multiple bonds between transition-metal and main-group elements. The multiple bonds between transition-metal and main-group elements are of interest in many important chemical and industrial processes.…”

Section: Introductionmentioning

confidence: 99%

MCSCF Study of Multiple Bonding between Ti and the Main-Group Elements C, Si, N, and P

Chung

Gordon

2002

Organometallics

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The nature of the multiple bonding of H2TiEH2 (E = C, Si) and H2TiEH (E = N, P) molecules has been investigated with the multiconfiguration SCF (MCSCF) method. It is shown that the Ti−C and Ti−P bond lengths decrease with bond rotation, whereas the Ti−Si bond length increases. MCSCF geometry optimization shows that Ti−N has triple-bond character with a linear Ti−N−H bond angle that results from strong back-bonding from the N lone pair into the empty Ti d orbitals. The rotation barrier and bond dissociation energy for TiE are estimated with the MCSCF + multireference second-order perturbation theory (MRMP2) method. The singlet rotation barriers in TiC, TiSi, and TiP are estimated to be 15.9, 8.6, and 9.3 kcal/mol, respectively. The TiC and TiSi bond dissociation energies are estimated to be 83.4 and 56.9 kcal/mol, respectively. The Ti⋮N triple-bond energy is about 30 kcal/mol larger than that of the carbon species, whereas the energy of the TiP bond is about 8 kcal/mol smaller than that of the silicon species. Disciplines Chemistry CommentsReprinted (adapted) with permission from Organometallics 22 (2003) The nature of the multiple bonding of H 2 TidEH 2 (E ) C, Si) and H 2 TidEH (E ) N, P) molecules has been investigated with the multiconfiguration SCF (MCSCF) method. It is shown that the Ti-C and Ti-P bond lengths decrease with bond rotation, whereas the Ti-Si bond length increases. MCSCF geometry optimization shows that Ti-N has triplebond character with a linear Ti-N-H bond angle that results from strong back-bonding from the N lone pair into the empty Ti d orbitals. The rotation barrier and bond dissociation energy for TidE are estimated with the MCSCF + multireference second-order perturbation theory (MRMP2) method. The singlet rotation barriers in TidC, TidSi, and TidP are estimated to be 15.9, 8.6, and 9.3 kcal/mol, respectively. The TidC and TidSi bond dissociation energies are estimated to be 83.4 and 56.9 kcal/mol, respectively. The TitN triple-bond energy is about 30 kcal/mol larger than that of the carbon species, whereas the energy of the TidP bond is about 8 kcal/mol smaller than that of the silicon species.

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Late transition-metal multiple bonding: Platinum phosphinidenes and ruthenium alkylidenes

Cited by 8 publications

References 38 publications

Computational Studies of Transition Metal−Main Group Multiple Bonding

Computational Studies of Transition Metal−Main Group Multiple Bonding

Substituent effects and the mechanism of alkene metathesis catalyzed by ruthenium dichloride catalysts

MCSCF Study of Multiple Bonding between Ti and the Main-Group Elements C, Si, N, and P

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