Conformation and electronic configuration of complexes with multiple dimetal units
MetadataShow full item record
By using the building blocks Mo2(DAniF)3(O2CCH3) (DAniF = N,N'-di-panisylformamidinate) and [Mo2(cis-DAniF)2(NCCH3)4](BF4)2, a series of complexes with multiple dimolybdenum units, bridged by a variety of linkers and having various oxidation states, has been synthesized and studied by various physical and chemical methods. The isomeric neutral diamidate-bridged molecules, α– and β– (DAniF)3Mo2(ArN(O)CC(O)NAr)Mo2(DAniF)3 (Ar = p-anisyl), have been oxidized to give the PF6 salts of the four cations α1+, α2+, β1+, β2+; all four structures together with supporting evidence show that in α1+ and α2+ the unpaired electrons are localized while in β1+ and β2+ they are delocalized in the time scale of these experiments. It is also found that a hydroxide bridged complex having a [Mo2](µ-OH)2[Mo2] core undergoes a oxidative deprotomation, both in solution and in crystals, to a compound with a [Mo2](µ-O)2[Mo2] core. A probable key intermediate with one OH and one O bridge has also been characterized. One electron oxidation of the tetrabridged compounds [Mo2(cis-DAniF)2]2(µ-X)4, where X is a halogen atom (Cl, Br, I), produces a decrease of about 0.24 Å in the separation between the midpoints of the multiply bonded dimolybdenum units. DFT calculations suggest partial bond formation during the oxidation, which is consistent with NIR, EPR and electrochemical measurements. Additionally, a pair of isomeric cyclic triads containing three [Mo2(cis-DAniF)2]2+ units, bridged by six fluoride anions, have been synthesized and crystallographically characterized. The symmetry of the α isomer is C2v because the three [Mo2] units are oriented in two orthogonal directions while that of the other isomer is D3h because the three [Mo2] units are parallel. No direct interconversion between isomers has been detected by heating or irradiation of solutions but oxidation of the α isomer first generates an α+ species that changes to β+. Finally, reaction of [Mo2(cis-DAniF)2(NCCH3)4](BF4)2 and Bun 4NBH4 in ether gives [Mo2(cis-DAniF)2]2(µ-H)4 (14), a compound whose Mo4H4 core may be described as an elongated tetrahedron in which the four H atoms are along the four long edges and the Mo2 units along the short edges.
Zhao, Qinliang (2007). Conformation and electronic configuration of complexes with multiple dimetal units. Doctoral dissertation, Texas A&M University. Available electronically from