Iridium- and rhodium-silanol complexes

Synthesis and reactivity

Roman Goikhman, Michael Aizenberg, Linda J W Shimon, David Milstein

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

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 structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-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 treatment of (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, the reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter shifting 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 a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. 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 metallosilanol (PPh3)2Ir(CO)(H)2(SiiPr2O H) (6). A stable PPh3-containing Ir-silanol was prepared by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).

Original languageEnglish
Pages (from-to)4020-4024
Number of pages5
JournalOrganometallics
Volume22
Issue number20
DOIs
Publication statusPublished - Sep 29 2003

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Iridium
Rhodium
iridium
rhodium
phosphine
phosphines
reactivity
synthesis
adducts
Carbon Monoxide
propane
chlorine
lithium
crystal structure
silanol
silicon
oxygen
hydrogen
geometry
configurations

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

Iridium- and rhodium-silanol complexes : Synthesis and reactivity. / Goikhman, Roman; Aizenberg, Michael; Shimon, Linda J W; Milstein, David.

In: Organometallics, Vol. 22, No. 20, 29.09.2003, p. 4020-4024.

Research output: Contribution to journalArticle

Goikhman, Roman ; Aizenberg, Michael ; Shimon, Linda J W ; Milstein, David. / Iridium- and rhodium-silanol complexes : Synthesis and reactivity. In: Organometallics. 2003 ; Vol. 22, No. 20. pp. 4020-4024.
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abstract = "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 structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-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 treatment of (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, the reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter shifting 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 a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. 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 metallosilanol (PPh3)2Ir(CO)(H)2(SiiPr2O H) (6). A stable PPh3-containing Ir-silanol was prepared by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).",
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N2 - 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 structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-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 treatment of (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, the reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter shifting 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 a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. 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 metallosilanol (PPh3)2Ir(CO)(H)2(SiiPr2O H) (6). A stable PPh3-containing Ir-silanol was prepared by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).

AB - 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 structure of 2 exhibits a trigonal-bipyramidal geometry, and intermolecular Si-O-H- - -Cl hydrogen bonding is present. Deprotonation of 2 results in the highly thermodynamically stable metallo-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 treatment of (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, the reaction is dependent on the concentration of the silanol and Et3P, an excess of the latter shifting 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 a 10-fold excess of the silanol, indicating that the cis-phosphine configuration in the adduct is unfavorable. 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 metallosilanol (PPh3)2Ir(CO)(H)2(SiiPr2O H) (6). A stable PPh3-containing Ir-silanol was prepared by starting from (PPh3)2Ir(CO)(H)2(Si(SEt)3). Following reaction with Et3SiOSO2CF3 to exchange one SEt substituent with OSO2CF3, reaction with NaOH generates the stable silanol complex (PPh3)2Ir(CO)(H)2(Si(SEt)2OH) (14).

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