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

详细信息    查看全文

• 作者：Yi Zeng ; Hao Feng ; R. Bruce King ; Henry F. Schaefer ; III
• 刊名：Organometallics
• 出版年：2014
• 出版时间：September 8, 2014
• 年：2014
• 卷：33
• 期：17
• 页码：4410-4416
• 全文大小：493K
• ISSN：1520-6041

文摘

Buchalski and co-workers showed in 2008 that reactions of the nickelafluorenyl anion CpNiC<sub>12sub>H<sub>8sub><sup>鈥?/sup> with MX<sub>2sub> (M = Co, Ni) give the dinickelametallocene sandwich compounds (CpNiC<sub>12sub>H<sub>8sub>)<sub>2sub>M. We now report theoretical studies on the related bis(nickelacyclopentadienyl)metal derivatives (CpNiC<sub>4sub>H<sub>4sub>)<sub>2sub>M and bis(nickelaindenyl)metal derivatives (CpNiC<sub>8sub>H<sub>6sub>)<sub>2sub>M as well as the bis(nickelafluorenyl)metal derivatives. The structures of the lowest energy bis(nickelacyclopentadienyl) sandwich compounds (CpNiC<sub>4sub>H<sub>4sub>)<sub>2sub>M may be derived from those of the corresponding metallocenes Cp<sub>2sub>M by replacing a CH group in each Cp ring with an isolobal CpNi unit. The Ni鈥揗 distances of 鈭?.5 脜 indicate formal single bonds and thus a pentahapto 畏<sup>5sup>-CpNiC<sub>4sub>H<sub>4sub> ligand. The spin states of the lowest energy (CpNiC<sub>4sub>H<sub>4sub>)<sub>2sub>M derivatives are similar to those of the corresponding metallocenes Cp<sub>2sub>M, 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 (CpNiC<sub>8sub>H<sub>6sub>)<sub>2sub>M and then the experimentally known bis(nickelafluorene) sandwich compounds (CpNiC<sub>12sub>H<sub>8sub>)<sub>2sub>M lowers the energy of the higher spin state. As a result, the lowest energy (CpNiC<sub>12sub>H<sub>8sub>)<sub>2sub>Co structure is not the doublet spin state of Cp<sub>2sub>Co and (CpNiC<sub>4sub>H<sub>4sub>)<sub>2sub>Co but instead a quartet spin state. This is in accord with experimental work showing (CpNiC<sub>12sub>H<sub>8sub>)<sub>2sub>Co to have a magnetic moment of 鈭?.7 渭<sub>Bsub>, indicating three unpaired electrons and thus the predicted quartet spin state.