Synthesis and Structural Characterization of Phosphine–Borane-Stabilized Dicarbanions with either Rigid or Flexible Spacers
详细信息 查看全文
- 作者：Keith Izod ; Casey M. Dixon ; Emma McMeekin ; Lee Rodgers ; Ross W. Harrington ; Ulrich Baisch
- 刊名：Organometallics
- 出版年：2014
- 出版时间：January 13, 2014
- 年：2014
- 卷：33
- 期：1
- 页码：378-386
- 全文大小：527K
- ISSN：1520-6041
文摘
The reaction between 1,2-C6H4(CH2Cl)2 and 2 equiv of in situ generated [R2P(BH3)]Li in THF gives the corresponding o-phenylene-bridged bis(phosphine鈥揵oranes) 1,2-C6H4{CH2P(BH3)R2}2 (R = iPr (1a), Ph (2a), Cy (3a)). Treatment of 1a鈥?b>3a with 2 equiv of nBuLi and 2 equiv of tmeda yields the corresponding phosphine鈥揵orane-stabilized carbanion (PBC) complexes [1,2-C6H4{CHP(BH3)R2}2][Li(tmeda)]2路nL (R = iPr, n = 0 (1b); R = Ph, nL = THF (2b); R = Cy, nL = 2PhCH3 (3b)). In contrast, treatment of 1a with 2 equiv of MeK, followed by 2 equiv of pmdeta, yields the monodeprotonation product [1,2-C6H4{CHP(BH3)iPr2}{CH2P(BH3)iPr2}][K(pmdeta)] (1c), due to a competing side reaction with the solvent. Treatment of 1a and 3a with the less aggressive metalating agent PhCH2K gives the corresponding dipotassium salts, the latter of which was isolated as the adduct [1,2-C6H4{CHP(BH3)Cy2}2][K(pmdeta)]2 (3c). X-ray crystallography reveals that 1b鈥?b>3b adopt similar structures in which the lithium ions are coordinated by the carbanion centers and the borane hydrogen atoms of the phosphine鈥揵orane-stabilized carbanions. The potassium ion in 1c is coordinated by the carbanion center and by B鈥揌路路路K contacts with both borane groups, whereas the two potassium ions in 3c exhibit multihapto interactions with the aromatic ring of the PBC ligand, along with B鈥揌路路路K contacts. The reaction between ClSiMe2CH2CH2SiMe2Cl and 2 equiv of in situ generated [R2P(BH3)CH2]Li gives the bis(phosphine鈥揵oranes) [CH2SiMe2CH2P(BH3)R2]2 (R = Me (4a), Ph (5a)). Treatment of 4a or 5a with 2 equiv of nBuLi in THF readily yields the 1,6-dicarbanion complexes [CH2SiMe2CHP(BH3)R2]2[Li(THF)2]2 (R = Me (4b), Ph (5b)). A similar reaction of 5a, 2 equiv of PhCH2K, and 2 equiv of pmdeta in THF gives the potassium complex [CH2SiMe2CHP(BH3)Ph2]2[K(pmdeta)]2 (5c). Complex 5b adopts a linear structure in the solid state, while 5c adopts an unusual polycyclic structure by virtue of bridging K路路路H鈥揃鈥揌路路路K contacts.