Int. J. Mol. Sci. 2011, 12(4), 2216-2231; doi:10.3390/ijms12042216
Article

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

1 School of Physics and Chemistry, Research Center for Advanced Computation, Xihua University, Chengdu, China 2 Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, GA 30602, USA
* Authors to whom correspondence should be addressed.
Received: 22 February 2011; in revised form: 8 March 2011 / Accepted: 14 March 2011 / Published: 30 March 2011
(This article belongs to the Special Issue Advances in Molecular Electronic Structure Calculations)
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Abstract: 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.
Keywords: iron carbonyls; iron-iron bonding; agostic hydrogen atom; metal-olefin complexes

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MDPI and ACS Style

Zeng, Y.; Wang, S.; Feng, H.; Xie, Y.; King, R.B. Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds. Int. J. Mol. Sci. 2011, 12, 2216-2231.

AMA Style

Zeng Y, Wang S, Feng H, Xie Y, King RB. Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds. International Journal of Molecular Sciences. 2011; 12(4):2216-2231.

Chicago/Turabian Style

Zeng, Yi; Wang, Shijian; Feng, Hao; Xie, Yaoming; King, R. Bruce. 2011. "Highly Unsaturated Binuclear Butadiene Iron Carbonyls: Quintet Spin States, Perpendicular Structures, Agostic Hydrogen Atoms, and Iron-Iron Multiple Bonds." Int. J. Mol. Sci. 12, no. 4: 2216-2231.

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