Carbon monoxide cleavage by (silox)3Ta (silox = tert-Bu3SiO-): physical, theoretical, and mechanistic investigations

Neithamer, David R.; LaPointe, Robert E.; Wheeler, Ralph A.; Richeson, Darrin S.; Duyne, Gregory D. Van; Wolczanski, Peter T.

doi:10.1021/ja00207a011

Cited by 200 publications

(144 citation statements)

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“…[8] Examples, so far reported, mainly concerns: carbonyl clusters, which generally provide metal carbides, [9] polynuclear early transitionmetal complexes, that take advantage of the oxophilic character of these metals for promoting CO dissociation, [10] and dinuclear tungsten complexes, with multiple metal-metal bonds. [11] Our results further support the conviction [8b] that dinuclear complexes are effective organometallic models for studying CO cleavage and C-C bond formation.…”

Section: Resultsmentioning

confidence: 99%

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

et al. 2006

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The vinyliminium complex [Fe2{μ‐η1:η3‐C(Me)=C(Me)C=N(Me)(Xyl)}(μ‐CO)(CO)(Cp)2][SO3CF3] (1; Xyl = 2,6‐Me2C6H3) reacts with LiC≡CR [R = C6H4Me = Tol, Ph, H, nBu, SiMe3, C(Me)=CH2] affording the amido‐functionalized allylidene complexes [Fe2{μ‐κ1(O):η1(C):η3(C)‐C(C≡CR)C(Me)C(Me)C(O)N(Me)(Xyl)}(μ‐CO)(Cp)2] [R = C6H4Me = Tol, 2; R = Ph, 3; R = H, 4; R = nBu, 5; R = SiMe3, 6; R = C(Me)=CH2, 7] in good yields. Labelling experiments with 13CO‐enriched 1 indicate that formation of 2–7 occurs through cleavage of the carbon–oxygen bond of a coordinated CO ligand. The molecular structure of 2 has been determined by an X‐ray diffraction study. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Section: Resultsmentioning

confidence: 99%

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

et al. 2006

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“…[31] Although some aspects of the mechanism remain unclear, it seems likely that the reaction proceeds through a mechanism involving a polynuclear [OCTa-…”

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Breaking Chemistry's Strongest Bond: Can Three‐Coordinate [M{N(R)Ar}₃] Complexes Cleave Carbon Monoxide?

Christian

Stranger

Petrie

et al. 2007

Chemistry A European J

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The reaction pathway for the interaction of CO with three-coordinate TaIII, WIII and ReIII complexes (modelled on the experimental [M{N(tBu)Ar}3] system) has been explored by using density functional methods. Calculations show that CO binds without a barrier to [Re(NH2)3], forming the encounter complex [OC--Re(NH2)3], which is stabilized by approximately 280 kJ mol-1 relative to the reactants. The binding of [Ta(NH2)3] to the oxygen terminus of CO is inhibited by a barrier of only 20 kJ mol-1 and is followed by spontaneous cleavage of the C--O bond to form the products [C--Re(NH2)3] and [O--Ta(NH2)3]. The salient features of the potential energy surface are more favourable to CO cleavage than the analogous N2 cleavage by [Mo(NH2)3], which is less exothermic (335 vs. 467 kJ mol-1) and is impeded by a significant barrier (66 kJ mol-1). The ReIII/TaIII/CO system therefore appears to be an excellent candidate for cleaving the exceptionally strong C--O bond under mild laboratory conditions. The related WIII/TaIII dimer, which significantly weakens but does not cleave the CO bond, may be a suitable alternative when the chemistry is to be performed on activated CO rather than on the strongly bound oxide and carbide cleavage products.

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“…[5][6][7][8][9][10][11][12][13] As a synthetic route to (silox) 3 WN (4, silox ) t Bu 3 SiO), the deoxygenation of (silox) 3 WNO (2) by (silox) 3 Ta (1-Ta) was attempted without success, despite ample precedent in cleavages of epoxides, 10 N 2 O, NO, 11 CO 2 , and CO. 12 A comparison study involving sources of M(silox) 3 (1-M; M ) V, Nb, Ta) revealed that features of deoxygenations of 2 and R 3 PO (R ) Me, Ph, t Bu) are the consequences of electronic effects enforced by a limiting steric environment. ) converted 2 to the nitride.…”

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Deoxygenations of (silox)₃WNO and R₃PO by (silox)₃M (M = V, Ta) and (silox)₃NbL (silox = ^tBu₃SiO): Consequences of Electronic Effects

et al. 2001

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Oxygen atom transfers involving terminal metal-oxo functionalities are central to many biological transformations, 1 prominent in applications to organic synthesis, 2-4 and of increasing importance in inorganic systems as synthetic tools, 5-7 objectives in biomimicry, 1,8,9 and targets of fundamental studies. [5][6][7][8][9][10][11][12][13] As a synthetic route to (silox) 3 WN (4, silox ) t Bu 3 SiO), the deoxygenation of (silox) 3 WNO (2) by (silox) 3 Ta (1-Ta) was attempted without success, despite ample precedent in cleavages of epoxides, 10 N 2 O, NO, 11 CO 2 , and CO. 12 A comparison study involving sources of M(silox) 3 (1-M; M ) V, Nb, Ta) revealed that features of deoxygenations of 2 and R 3 PO (R ) Me, Ph, t Bu) are the consequences of electronic effects enforced by a limiting steric environment. ) converted 2 to the nitride. (silox) 3 Nb(η 2 -N,C-4-picoline) (1-Nb-(4-pic), S ) 0) 11 and (silox) 3 NbPMe 3 (1-NbPMe 3 , S ) 1) 14 deoxygenated 2 and formed 4 and (silox) 3 NbO (3-Nb) swiftly at first, then more slowly as the released 4-picoline and PMe 3 inhibited the reactions, respectively. With a 4-picoline scavenger (1-Ta) present in the former, swift cyclometalation to (silox) 2 -HNbOSi t Bu 2 CMe 2 CH 2 (5-Nb, 23°C, <5 min) 14 competed with deoxygenation; 5-Nb then slowly deoxygenated 2, presumably via reversible formation of 1-Nb. The thermodynamics of deoxygenation 15 were investigated by high-level quantum calculations, 16 with (HO) 3 M serving as the model of respective tris-silox centers in 1-M and 3-M. In each case the reaction was extremely exoergic (25°C: M ) V, ∆G°r xn ) -66 kcal/mol; M ) Nb, Ta, -100 kcal/mol). With favorable thermodynamics, the uncompetitive (1-Ta) and relatively slow (1-V, 1-Nb) deoxygenations are puzzling.Since (silox) 3 V (1-V, S ) 1) binds various L (L ) THF, py, etc.), while (silox) 3 Ta (1-Ta, S ) 0) does not, 17 the singlet and triplet states of 1-M were examined via quantum calculations. 16 Figure 1 reveals that 1-V is a triplet at the optimized geometries for, and the TfS barrier is 17 kcal/mol, assuming a facile intersystem crossing. 1-Ta is a singlet at the optimized S ) 0 and S ) 1 geometries and its intersystem crossing barrier is 17 kcal/mol. 1-Nb is a singlet, but the conversion barrier to a triplet of nearly the same energy is 2 kcal/mol. If the approach of (silox) 3 WNO (2) to the 1-M center is linear because of intermolecular silox/silox interactions, then a 4e-repulsion will result in the case of 1-Ta, but successful docking to an S ) 1 intermediate (silox) 3 MONW(silox) 3 (1-M-2) will occur for M ) V, Nb. The additional S-T barrier forced on 1-Ta allows unimolecular cyclometalation to compete with the bimolecular deoxygenation of 2. Table 1 lists the results of R 3 PO deoxygenations by (1-V, Ta) and 1-NbL (L ) 4-pic, PMe 3 ), which are predicted by quantum calculations to be exothermic for V (-15 kcal/mol) and Nb or Ta (-45 kcal/mol) with Me 3 PO. Curiously, 1-Ta and 1-NbL both deoxygenated Me 3 PO and Ph 3 PO, but failed with t Bu 3 PO; 1-Ta cyclomet...

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Carbon monoxide cleavage by (silox)3Ta (silox = tert-Bu3SiO-): physical, theoretical, and mechanistic investigations

Cited by 200 publications

References 4 publications

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

Breaking Chemistry's Strongest Bond: Can Three‐Coordinate [M{N(R)Ar}₃] Complexes Cleave Carbon Monoxide?

Deoxygenations of (silox)₃WNO and R₃PO by (silox)₃M (M = V, Ta) and (silox)₃NbL (silox = ^tBu₃SiO): Consequences of Electronic Effects

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Carbon monoxide cleavage by (silox)3Ta (silox = tert-Bu3SiO-): physical, theoretical, and mechanistic investigations

Cited by 200 publications

References 4 publications

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

CO Cleavage Promoted by Acetylide Addition to Vinyliminium Diiron Complexes

Breaking Chemistry's Strongest Bond: Can Three‐Coordinate [M{N(R)Ar}3] Complexes Cleave Carbon Monoxide?

Deoxygenations of (silox)3WNO and R3PO by (silox)3M (M = V, Ta) and (silox)3NbL (silox = tBu3SiO): Consequences of Electronic Effects

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Resources

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Breaking Chemistry's Strongest Bond: Can Three‐Coordinate [M{N(R)Ar}₃] Complexes Cleave Carbon Monoxide?

Deoxygenations of (silox)₃WNO and R₃PO by (silox)₃M (M = V, Ta) and (silox)₃NbL (silox = ^tBu₃SiO): Consequences of Electronic Effects