Cationic dihydrogen/dihydride complexes of osmium: Structure and dynamics

Jonathan D. Egbert, R Morris Bullock, D. Michael Heinekey

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Reaction of Cp*Os(CO)2Cl with [Et3Si][BAr 4F] under hydrogen gas affords the cationic hydrogen complex [Cp*Os(CO)2(H2)][BAr4 F] (1) (Cp* = C5Me5; ArF = C6F5). When this reaction is carried out with HD gas, complex 1-d1 results, with JHD -24.5 Hz. When solutions of complex 1 are monitored by 1H NMR spectroscopy over several days, the gradual formation of a trans dihydride species is observed. Similarly, reaction of CpOs(dppm)Br with Na[BArF*4] (Ar F* = 3,5-(CF3)2C6H 3) under hydrogen affords the cationic dihydride complex [CpOs(dppm)H2][BArF*4] (2). At 295 K, complex 2 exists as a 10:1 mixture of cis and trans isomers. The 1H NMR spectrum of the cis form in the hydride region exhibits a triplet with JHP = 6.5 Hz, due to rapid exchange of the hydrogen atoms. At low temperature, static spectra of the HH′PP′ spin system can be obtained, revealing quantum mechanical exchange coupling between the two hydride ligands. The observed JHH′ is temperature dependent, varying from 133 Hz at 141 K to 176 Hz at 198 K. This is the first report of detectable exchange coupling between pairs of chemically equivalent hydrogen atoms.

Original languageEnglish
Pages (from-to)2291-2295
Number of pages5
JournalOrganometallics
Volume26
Issue number9
DOIs
Publication statusPublished - Apr 23 2007

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Osmium
dihydrides
osmium
Hydrogen
hydrides
hydrogen atoms
hydrogen
Exchange coupling
nuclear magnetic resonance
Hydrides
gases
Gases
isomers
Atoms
ligands
Isomers
Nuclear magnetic resonance spectroscopy
Ion exchange
spectroscopy
Nuclear magnetic resonance

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

Cationic dihydrogen/dihydride complexes of osmium : Structure and dynamics. / Egbert, Jonathan D.; Bullock, R Morris; Heinekey, D. Michael.

In: Organometallics, Vol. 26, No. 9, 23.04.2007, p. 2291-2295.

Research output: Contribution to journalArticle

Egbert, Jonathan D. ; Bullock, R Morris ; Heinekey, D. Michael. / Cationic dihydrogen/dihydride complexes of osmium : Structure and dynamics. In: Organometallics. 2007 ; Vol. 26, No. 9. pp. 2291-2295.
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abstract = "Reaction of Cp*Os(CO)2Cl with [Et3Si][BAr 4F] under hydrogen gas affords the cationic hydrogen complex [Cp*Os(CO)2(H2)][BAr4 F] (1) (Cp* = C5Me5; ArF = C6F5). When this reaction is carried out with HD gas, complex 1-d1 results, with JHD -24.5 Hz. When solutions of complex 1 are monitored by 1H NMR spectroscopy over several days, the gradual formation of a trans dihydride species is observed. Similarly, reaction of CpOs(dppm)Br with Na[BArF*4] (Ar F* = 3,5-(CF3)2C6H 3) under hydrogen affords the cationic dihydride complex [CpOs(dppm)H2][BArF*4] (2). At 295 K, complex 2 exists as a 10:1 mixture of cis and trans isomers. The 1H NMR spectrum of the cis form in the hydride region exhibits a triplet with JHP = 6.5 Hz, due to rapid exchange of the hydrogen atoms. At low temperature, static spectra of the HH′PP′ spin system can be obtained, revealing quantum mechanical exchange coupling between the two hydride ligands. The observed JHH′ is temperature dependent, varying from 133 Hz at 141 K to 176 Hz at 198 K. This is the first report of detectable exchange coupling between pairs of chemically equivalent hydrogen atoms.",
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