Skip to main content

N-heterocyclic carbene and phosphine complexes of osmium and ruthenium carbonyls

Resource type
Thesis type
(Thesis) Ph.D.
Date created
1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene-silver(I)chloride ([IMes]AgCl), a carbene transfer agent, was employed in the reaction with various osmium clusters. Reaction of ([IMes]AgCl) with [Os3(µ-H)2(CO)10] gave [Os3(µ-H)(µ-Cl)(CO)9(IMes)] (1), an osmium N-heterocyclic carbene complex. The reaction of ([IMes]AgCl) with the cluster [Os3(CO)10(CH3CN)2] yielded two products, [Os3(µ-Cl)(CO)10(µ-Ag(IMes)] (2) and [(IMes-H)][Os3(µ-Cl)(CO)10](µ4-Ag)[Os3(µ-Cl)(CO)10] (3). Compound (2) is a heterobimetallic carbene complex resulting from the complete incorporation of ([IMes]AgCl). Transmetalation of the IMes fragment resulted in the formation of [Os4(µ-H)4(CO)11(n•IMes)] (4) (n denotes normal carbene bonding) and [Os4(µ-H)4(CO)10(IMes)2] (5). Compound (5) was found to be sensitive to silica gel column chromatography in the presence of dichloromethane decomposing to [Os4(µ-H)3(µ-Cl)(CO)11(IMes)] (6) which possessed a butterfly metal skeleton. The ruthenium analogue of (4), [Ru4(µ-H)4(CO)11(IMes)] (7), was prepared and found to be thermally unstable. Thermolysis of (4) in benzene yielded four products. The abnormal carbene complex [Os4(µ-H)4(CO)11(a•IMes)] (9) (a denotes abnormal carbene bonding), an isomer of (4), and {Os4(μ-H)(CO)10[(η-C)N(Mes)C2H2NC6H2 (CH3)2(η2-C)(η-C)C4H4(η2-C)]} (10), an unusual complex resulting from the activation of benzene, were isolated in modest yields. Two higher-nuclearity clusters, {Os5(µ5-C)(CO)14[η-C-η-NC2H2(Mes)]} (8) and [Os6(µ-H)4(µ5-C)(CO)15(IMes)] (11), both of which contain carbide ligands, were also isolated. {Os4(μ-H)(CO)10[(η-C)N(Mes)C2H2NC6H2(CH3)2(η2-C)(η-C)CHC(CH3)C2 H2(η2-C)]} (12), an analogue of (10), resulted from the thermolysis of (4) in toluene. Systematic synthesis of pentanuclear osmium hydride clusters was achieved by reaction of [Os4(µ-H)4(CO)12] with [Os(CO)4(PMe3)] giving three products, [Os5(µ-H)2(CO)15(PMe3)] (13), [Os5(µ-H)4(CO)14(PMe3)] (14) and [Os5(µ-H)2(CO)14(PMe3)] (15). (13) and (14) contain edge-bridged metal skeletons. Heating of (13) or (14) resulted in the formation of [Os5(µ-H)2(CO)14(PMe3)] (16), with a trigonal bipyramidal skeletal structure similar to (15) but differing in the location of the phosphine. Trinuclear mixed-metal clusters of the form [Ru2Os(CO)11(PR3)] (PR3 = PMe3, PEt3, P(OMe)3, PPh3, PMe¬2Ph, P(OCH2)3CMe), (17) to (22), have been systematically synthesized. The structure of the PMe3 derivative (17) had a staggered carbonyl conformation attributed to the electron-donating properties of the phosphorus ligand. Carbonyl exchange in the clusters was studied by 13CO labelling, if needed, and by variable-temperature 13C NMR spectroscopy.
Copyright statement
Copyright is held by the author.
The author has not granted permission for the file to be printed nor for the text to be copied and pasted. If you would like a printable copy of this thesis, please contact
Scholarly level
Member of collection
Download file Size
etd3498.pdf 18.59 MB

Views & downloads - as of June 2023

Views: 9
Downloads: 2