Dinickelametallocenes: Sandwich Compounds of the First-Row Transition Metals (M = Fe, Co, Ni) with Two Pentahapto Planar Nickelacycle Ligands

作者：Zeng Yi; Feng Hao^*; King R Bruce; Schaefer Henry F III

来源：Organometallics, 2014, 33(17): 4410-4416.

DOI：10.1021/om500574m

Buchalski and co-workers showed in 2008 that reactions of the nickelafluorenyl anion CpNiC12H8- with MX2 (M = Co, Ni) give the dinickelametallocene sandwich compounds (CpNiC12H8)(2)M. We now report theoretical studies on the related bis(nickelacyclopentadienyl)metal derivatives (CpNiC4H4)(2)M and bis(nickelaindenyl)metal derivatives (CpNiC8H6)(2)M as well as the bis(nickelafluorenyl)metal derivatives. The structures of the lowest energy bis(nickelacyclopentadienyl) sandwich compounds (CpNiC4H4)(2)M may be derived from those of the corresponding metallocenes Cp2M by replacing a CH group in each Cp ring with an isolobal CpNi unit. The Ni-M distances of similar to 2.5 angstrom indicate formal single bonds and thus a pentahapto eta(5)-CpNiC4H4 ligand. The spin states of the lowest energy (CpNiC4H4)(2)M derivatives are similar to those of the corresponding metallocenes Cp2M, namely, singlet, doublet, and triplet for M = Fe, Co, and Ni, respectively. Fusion of benzene rings to the nickelacyclopentadienyl rings to give first the bis(nickelaindene) sandwich compounds (CpNiC8H6)(2)M and then the experimentally known bis(nickelafluorene) sandwich compounds (CpNiC12H8)(2)M lowers the energy of the higher spin state. As a result, the lowest energy (CpNiC12H8)(2)Co structure is not the doublet spin state of Cp2Co and (CpNiC4H4)(2)Co but instead a quartet spin state. This is in accord with experimental work showing (CpNiC12H8)(2)Co to have a magnetic moment of similar to 3.7 mu(B), indicating three unpaired electrons and thus the predicted quartet spin state.

• 出版日期2014-9-8
• 单位西华大学