Open chains versus closed rings: comparison of binuclear butadiene iron carbonyls with their cyclobutadiene analogues

Zeng, Yi; Wang, Shijian; Feng, Hao; Xie, Yaoming; King, R. B.; Schaefer, Henry F.

doi:10.1039/c0nj00884b

Cited by 9 publications

(13 citation statements)

References 46 publications

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“…Carbonyl-free iron atoms are even more positive but their natural positive charges span a wide range from 0.28 to 0.83. Thus the previously observed [ 4 ] general trend of increasing natural negative charges on the iron atoms with increasing number of carbonyl ligands is also found here. However, other factors besides the number of carbonyl groups also affect significantly the natural charges on the iron atoms.…”

Section: Resultssupporting

confidence: 89%

“…[4]. The predicted energy for loss of a single carbonyl group from (C 4 H 6 ) 2 Fe 2 (CO) 2 is large, namely ∼30 kcal/mol as well as a free energy of ∼20 kcal/mol.…”

Section: Resultsmentioning

confidence: 99%

“…The natural charges on the iron atoms and the Wiberg Bond Indices (WBIs) for the iron-iron bonds are listed in Table 7 along with the Fe–Fe distances, the iron electronic configurations, and formal iron-iron bond orders. For the less unsaturated binuclear butadiene iron carbonyls (C 4 H 6 ) 2 Fe 2 (CO) n ( n = 7, 6, 5, 4, 3) studied previously [ 4 ] the natural charges on the iron atoms correlate mainly with the numbers of carbonyl groups on the iron atoms and the WBIs correlated with the formal iron-iron bond orders. However, the much greater variety of iron electronic configurations and spin states encountered in the highly unsaturated (C 4 H 6 ) 2 Fe 2 (CO) n ( n = 2, 1) structures reported in this paper make the interpretations much less clear.…”

Section: Resultsmentioning

confidence: 99%

“…However, no binuclear butadiene iron carbonyl derivatives with short iron-iron distances suggesting iron-iron bonds have been synthesized. In order to assess the possibilities for binuclear iron carbonyl derivatives with iron-iron bonds we have performed a density functional theory (DFT) study on possible structures for (η 4 -C 4 H 6 ) 2 Fe 2 (CO) n ( n = 5, 4, 3), predicted to have structures with formal Fe–Fe single bonds, Fe═Fe double bonds, and Fe≡Fe triple bonds, respectively [ 4 ]. In general, the lowest energy structures for these (η 4 -C 4 H 6 ) 2 Fe 2 (CO) n derivatives were found to be coaxial structures in which each metal atom is bonded to a single butadiene ligand ( Figure 1B ).…”

Section: Introductionmentioning

confidence: 99%

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Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds

Zeng

Wang

Feng

et al. 2011

IJMS

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The highly unsaturated binuclear butadiene iron carbonyls (C4H6)2Fe2(CO)n (n = 2, 1) have been examined using density functional theory. For (C4H6)2Fe2(CO)n (n = 2, 1), both coaxial and perpendicular structures are found. The global minima of (C4H6)2Fe2(CO)n (n = 2, 1) are the perpendicular structures 2Q-1 and 1Q-1, respectively, with 17- and 15-electron configurations for the iron atoms leading to quintet spin states. The Fe=Fe distance of 2.361 Å (M06-L) in the (C4H6)2Fe2(CO)2 structure 2Q-1 suggests a formal double bond. The Fe≡Fe bond distance in the (C4H6)2Fe2(CO) structure 1Q-1 is even shorter at 2.273 Å (M06-L), suggesting a triple bond. Higher energy (C4H6)2Fe2(CO)n (n = 2, 1) structures include structures in which a bridging butadiene ligand is bonded to one of the iron atoms as a tetrahapto ligand and to the other iron atom through two agostic hydrogen atoms from the end CH2 groups. Singlet (C4H6)2Fe2(CO) structures with formal Fe–Fe quadruple bonds of lengths ∼2.05 Å were also found but at very high energies (∼47 kcal/mol) relative to the global minimum.

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Section: Resultssupporting

confidence: 89%

“…[4]. The predicted energy for loss of a single carbonyl group from (C 4 H 6 ) 2 Fe 2 (CO) 2 is large, namely ∼30 kcal/mol as well as a free energy of ∼20 kcal/mol.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds

Zeng

Wang

Feng

et al. 2011

IJMS

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“…The still higher WBI value of 0.83 for 4S-1 can be interpreted as indicating a strong formal CrCr triple bond. These WBI values are consistent with those in our previous theoretical studies37 where formal Fe−Fe single bonds were found to have values of 0.12−0.19.…”

supporting

confidence: 92%

Nickelacyclopentadienylchromium Tricarbonyl Unit as a Bulky Pseudohalogen in Cyclopentadienylchromium Complexes Leading to Low-Energy High-Spin Structures

Zeng

Feng

et al. 2015

Inorg. Chem.

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Recent studies, particularly from the laboratory of Buchalski and co-workers, have resulted in the syntheses of nickelacyclopentadienyl and nickelafluorenyl metallacycles that can function as pentahapto ligands in transition-metal complexes, similar to the ubiquitous cyclopentadienyl ligand. The structures and energetics of the neutral binuclear chromium carbonyls (CpNiC4H4)2Cr2(CO)n (n = 6, 5, 4, 3; Cp = η(5)-C5H5) containing the unsubstituted nickelacyclopentadienyl ligand have been investigated by density functional theory. The lowest energy (CpNiC4H4)2Cr2(CO)n (n = 6, 4) structures are similar to the corresponding experimentally characterized Cp2Cr2(CO)n structures with predicted Cr-Cr distances of ∼3.22 and ∼2.27 Å corresponding to the formal single and triple bonds, respectively. This gives the chromium atoms, as well as the nickel atoms, the favored 18-electron configuration. These species appear to be promising synthetic targets. However, the lowest energy (CpNiC4H4)2Cr2(CO)n (n = 5, 3) structures, as well as two (CpNiC4H4)2Cr2(CO)4 structures ∼10 to 12 kcal/mol in energy above the global minimum, can be dissected into a discrete pseudohalogen (CpNiC4H4)Cr(CO)3 unit and a (CpNiC4H4)Cr(CO)n-3 unit linked by a Cr-Cr bond flanked by one to three generally weakly semibridging CO groups. In most cases, the chromium atoms in the (CpNiC4H4)Cr(CO)n-3 units of these structures have 14-16-electron configurations rather than the favored 18-electron configuration. This leads to triplet and even quintet spin states in the lowest energy structures.

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The rigidity of the central C4Fe2 unit in binuclear ferrole iron carbonyl derivatives upon decarbonylation

et al. 2014

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Open chains versus closed rings: comparison of binuclear butadiene iron carbonyls with their cyclobutadiene analogues

Cited by 9 publications

References 46 publications

Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds

Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds

Nickelacyclopentadienylchromium Tricarbonyl Unit as a Bulky Pseudohalogen in Cyclopentadienylchromium Complexes Leading to Low-Energy High-Spin Structures

The rigidity of the central C4Fe2 unit in binuclear ferrole iron carbonyl derivatives upon decarbonylation

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