Formation of Triniobocene Cationic and Neutral Mononiobocene Species as a Function of Solvent in the Reaction of Cp2Nb{(-H)
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- 作者：Shengming Liu ; Fu-Chen Liu ; Gordon Renkes ; and Sheldon G. Shore
- 刊名：Organometallics
- 出版年：2001
- 出版时间：December 24, 2001
- 年：2001
- 卷：20
- 期：26
- 页码：5717 - 5723
- 全文大小：104K
- 年卷期：v.20,no.26(December 24, 2001)
- ISSN：1520-6041
文摘
Reactions of the niobocene cyclic organohydroborates Cp2Nb{(
-H)2BR2} (R2 = C4H8, C5H10,C8H14), with B(C6F5)3 in the poorly coordinating solvent toluene and in the coordinatingsolvent diethyl ether give different products. In toluene, the salt [Cp2Nb(-H)(
5-1-C5H4)Nb(5-1-C5H4)2Nb{(-H)(5-C5H4B(C6F5)2)}]+[HB(C6F5)3]-, 1, which contains a triniobocenecation, is formed. On the other hand in diethyl ether, the reaction of Cp2Nb{(-H)2BR2}with B(C6F5)3 produces the covalent complex CpNb(C6F5){(-H)(5-C5H4B(C6F5)2)}, 2. In theformation of these compounds NbIII is oxidized to NbIV. Upon the basis of ESR spectra, 1and 2 are paramagnetic, each with one unpaired electron. The structures of 1 and 2 weredetermined by single-crystal X-ray analysis. Complex 2 forms weak adducts in the solventsTHF and pyridine. The Nb-H-B bridge is cleaved at the Nb-H site to form CpNb(C6F5)(L){5-C5H4B(H)(C6F5)2} (L = THF, pyridine). In pyridine, a second adduct in much smalleryield is also formed, CpNb(C6F5)(H){5-C5H4B(Py)(C6F5)2, with the Nb-H-B bridge beingcleaved at the H-B site.
-H)2BR2} (R2 = C4H8, C5H10,C8H14), with B(C6F5)3 in the poorly coordinating solvent toluene and in the coordinatingsolvent diethyl ether give different products. In toluene, the salt [Cp2Nb(-H)(5-1-C5H4)Nb(5-1-C5H4)2Nb{(-H)(5-C5H4B(C6F5)2)}]+[HB(C6F5)3]-, 1, which contains a triniobocenecation, is formed. On the other hand in diethyl ether, the reaction of Cp2Nb{(-H)2BR2}with B(C6F5)3 produces the covalent complex CpNb(C6F5){(-H)(5-C5H4B(C6F5)2)}, 2. In theformation of these compounds NbIII is oxidized to NbIV. Upon the basis of ESR spectra, 1and 2 are paramagnetic, each with one unpaired electron. The structures of 1 and 2 weredetermined by single-crystal X-ray analysis. Complex 2 forms weak adducts in the solventsTHF and pyridine. The Nb-H-B bridge is cleaved at the Nb-H site to form CpNb(C6F5)(L){5-C5H4B(H)(C6F5)2} (L = THF, pyridine). In pyridine, a second adduct in much smalleryield is also formed, CpNb(C6F5)(H){5-C5H4B(Py)(C6F5)2, with the Nb-H-B bridge beingcleaved at the H-B site.