Chemical applications of topology and group theory: 37. Pentalene as a ligand in transition metal sandwich complexes

King, R. B.

doi:10.1002/aoc.444

Cited by 20 publications

(17 citation statements)

References 17 publications

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“…In addition, elementary group theory considerations show that a pair of pentalene ligands in a D 2d (C 8 H 6 ) 2 Ti structure can only donate 14 (rather than the full 16) electrons to a central titanium atom. 15 Our theoretical results show the unsymmetrical octahaptohexahapto structure (Z 8 -C 8 H 6 )(Z 6 -C 8 H 6 )Ti to be the lowest energy (C 8 H 6 ) 2 Ti structure and the D 2d bis(octahapto) (Z 8 -C 8 H 6 ) 2 Ti structure to be a transition state B10 kcal mol À1 above this global minimum with a significant imaginary vibrational frequency of B90i cm À1 . We therefore conclude that the (C 8 H 6 ) 2 Ti obtained experimentally but not characterized structurally [10][11][12] is the unsymmetrical 18-electron octahaptohexahapto complex (Z 8 -C 8 H 6 )(Z 6 -C 8 H 6 )Ti, rather than the symmetrical bis(octahapto) complex (Z 8 -C 8 H 6 ) 2 Ti.…”

Section: Discussionmentioning

confidence: 72%

“…Such a bis(octahapto) (Z 8 -C 8 H 6 ) 2 Ti structure is interesting since it appears to give the central titanium atom an unfavorable 20-electron configuration. However, a grouptheoretical analysis 15 shows that a pair of Z 8 -C 8 H 6 ligands in a sandwich-type (C 8 H 6 ) 2 Ti structure can donate a total of only 14 rather than 16 electrons because of a lack of suitable titanium orbitals for two of the 16 available electrons from the pair of Z 8 -C 8 H 6 ligands. Subsequent DFT studies 16 suggest that the D 2d (Z 8 -C 8 H 6 ) 2 Ti structure is a transition state rather than a true minimum and predict lower symmetry (Z 8 -C 8 H 6 )(Z 6 -C 8 H 6 )Ti structures for bis(pentalene)titanium with one uncomplexed CQC double bond in the hexahapto Z 6 -C 8 H 6 ligand.…”

Section: Introductionmentioning

confidence: 99%

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Mononuclear bis(pentalene) sandwich compounds of the first-row transition metals: variable hapticity of the pentalene rings and intramolecular coupling reactions

Feng

Sun

et al. 2011

New J. Chem.

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Section: Discussionmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Mononuclear bis(pentalene) sandwich compounds of the first-row transition metals: variable hapticity of the pentalene rings and intramolecular coupling reactions

Feng

Sun

et al. 2011

New J. Chem.

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“…1 COT and Pn are isoelectronic. However, Pn is constrained by its bridgehead bond, forcing a near-planar geometry, and is therefore antiaromatic by Huckel's 4n definition.…”

Section: ■ Introductionmentioning

confidence: 99%

Zirconium and Hafnium Permethylpentalene Compounds

2016

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A selection of new η 8 -permethylpentalene zirconium and hafnium complexes are reported. The first d-block metal bis-(permethylpentalene) sandwich complexes, (Pn* 2 M ; Pn* = C 8 Me 6 ; M = Zr, Hf) have been synthesized and structurally characterized. The bis-allyl species Pn*M(C 3 H 5 ) 2 (M = Zr, Hf) have been synthesized; these complexes are fluxional in solution and react with CO 2 to give the double-insertion product Pn*M(κ 2 -O 2 CCH 2 CHCH 2 ) 2 (M = Zr, Hf). We also report monometallic, bimetallic, and polymeric σ-bonded alkyl derivatives such as (Pn*Zr) 2 (μ-CH 2 )(μ-Me) 2 , [Pn*Hf(CH 2 Ph) 3 ][Li(1,4-dioxane) 4 ], and [Pn*ZrPh(μ-Ph) 2 Li(μ-1,4-dioxane)] n .

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“…This suggestion has attracted much attention from both experimental [4][5][6][7][8][9] and theoretical [10,11] chemists. Organometallic derivatives of pentalene were first synthesized in 1963 by Katz and co-workers [12] using the pentalene dianion as the pentalene source.…”

Section: Introductionmentioning

confidence: 99%

Binuclear Pentalene Iron Carbonyl Complexes

Feng

Sun

et al. 2011

Eur J Inorg Chem

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The bicyclic hydrocarbon pentalene, although unstable in the free state, forms a stable iron carbonyl derivative cis‐(η5,η5‐C8H6)Fe2(CO)4(μ‐CO). In this connection, the series of binuclear pentalene iron carbonyl derivatives C8H6Fe2(CO)n (n = 7, 6, 5, 4) have been investigated by density functional theory. The lowest energy C8H6Fe2(CO)6 structure is predicted to be trans‐(η5,η5‐C8H6)Fe2(CO)6 without an iron–iron bond. However, a cis‐(η5,η1‐C8H6)Fe2(CO)6 structure with an uncomplexed pentalene C=C double bond and a formal Fe–Fe bond of length 2.646 Å (BP86) lies only ca. 3 kcal/mol above this global minimum. The CO dissociation energy of C8H6Fe2(CO)6 to give C8H6Fe2(CO)5 is predicted to be only ca. 12 kcal/mol, explaining the formation of C8H6Fe2(CO)5 rather than C8H6Fe2(CO)6 in reactions of dihydropentalene with iron carbonyls. In addition, the experimentally known cis‐(η5,η5‐C8H6)Fe2(CO)4(μ‐CO) structure is found to be the lowest energy C8H6Fe2(CO)5 structure by more than 25 kcal/mol (BP86). For the tetracarbonyl two triplet and two singlet cis‐C8H6Fe2(CO)4 structures lie within 7 kcal/mol of each other (BP86) with the triplet structures being of slightly lower energies. The singlet C8H6Fe2(CO)4 structure is predicted to be thermodynamically unfavorable with respect to disproportionation into C8H6Fe2(CO)5 + C8H6Fe2(CO)3.

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Chemical applications of topology and group theory: 37. Pentalene as a ligand in transition metal sandwich complexes

Cited by 20 publications

References 17 publications

Mononuclear bis(pentalene) sandwich compounds of the first-row transition metals: variable hapticity of the pentalene rings and intramolecular coupling reactions

Mononuclear bis(pentalene) sandwich compounds of the first-row transition metals: variable hapticity of the pentalene rings and intramolecular coupling reactions

Zirconium and Hafnium Permethylpentalene Compounds

Binuclear Pentalene Iron Carbonyl Complexes

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