title: Highly unsaturated binuclear butadiene iron carbonyls: quintet spin states, perpendicular structures, agostic hydrogen atoms, and iron-iron multiple bonds.
abstract: The highly unsaturated binuclear butadiene iron carbonyls (C(4)H(6))(2)Fe(2)(CO)(n) (n = 2, 1) have been examined using density functional theory. For (C(4)H(6))(2)Fe(2)(CO)(n) (n = 2, 1), both coaxial and perpendicular structures are found. The global minima of (C(4)H(6))(2)Fe(2)(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 (C(4)H(6))(2)Fe(2)(CO)(2) structure 2Q-1 suggests a formal double bond. The Fe≡Fe bond distance in the (C(4)H(6))(2)Fe(2)(CO) structure 1Q-1 is even shorter at 2.273 Å (M06-L), suggesting a triple bond. Higher energy (C(4)H(6))(2)Fe(2)(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 CH(2) groups. Singlet (C(4)H(6))(2)Fe(2)(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.
authors: School of Physics and Chemistry, Research Center for Advanced Computation, Xihua University, Chengdu, China; E-Mails: zengyi08@hotmail.com (Y.Z.); xhuwsj@163.com (S.W.).
authors: Yi
authors: Y
authors: Zeng
authors: Shijian
authors: S
authors: Wang
authors: Hao
authors: H
authors: Feng
authors: Yaoming
authors: Y
authors: Xie
authors: R Bruce
authors: RB
authors: King
mesh_terms: D000475:Alkenes / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry; D008968:Molecular Conformation; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D000475:Alkenes; D002070:Butadienes; D056831:Coordination Complexes; D058085:Iron Compounds; C515100:iron pentacarbonyl; D006859:Hydrogen; D007501:Iron; C031763:1,3-butadiene