Iridium- and Rhodium-Silanol Complexes: Synthesis and Reactivity
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- 作者：Roman Goikhman ; Michael Aizenberg ; Linda J. W. Shimon ; and David Milstein
- 刊名：Organometallics
- 出版年：2003
- 出版时间：September 29, 2003
- 年：2003
- 卷：22
- 期：20
- 页码：4020 - 4024
- 全文大小：85K
- 年卷期：v.22,no.20(September 29, 2003)
- ISSN：1520-6041
文摘
Methods of metallo-silanol synthesis have been developed. The Ir(I) complex (Et3P)2Ir(C2H4)Cl (1) oxidatively adds secondary silanols R2SiHOH (R = iPr, tBu) to yield the iridium-silanol complexes [(Et3P)2Ir(H)(Cl)(SiR2OH)] (R = iPr, 2; R = tBu, 3). The crystal structureof 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogenbonding is present. Deprotonation of 2 results in the highly thermodynamically stablemetallo-silanolate [(Et3P)2Ir(H)(Cl)(SiiPr2OLi)]2 (4). Compound 4 has an almost planar core,consisting of two atoms each of iridium, silicon, chlorine, oxygen, and lithium. Upon treatmentof (Et3P)3RhCl with HSiiPr2OH, the first Rh-silanol complex, trans-[(Et3P)2Rh(H)(Cl)(iPrSi2OH)], is formed in an equilibrium with the starting complex (Keq = 4 × 10-3); hence, thereaction is dependent on the concentration of the silanol and Et3P, an excess of the lattershifting the equilibrium to the starting compounds. Reaction of the bis-phosphine complex[(Et3P)2RhCl]2 with the silanol, which does not generate free phosphine, results in 96%conversion to the adduct. On the other hand, the chelating bis-phosphine complex [(bis(diisopropylphosphino)propane)RhCl]2 does not add the silanol even in the presence of a10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct isunfavorable. In contrast to the Et3P-containing Ir complex, and similarly to the Rh complex,(PPh3)3Ir(CO)H reacts with iPr2SiHOH reversibly, leading to 60% conversion to the metallo-silanol (PPh3)2Ir(CO)(H)2(SiiPr2OH) (6). A stable PPh3-containing Ir-silanol was preparedby starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 toexchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stablesilanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).