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

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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)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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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