Isomerization of the diphosphine ligand 3,4-bis(diphenylphosphino)-5- methoxy-2(5H)-furanone (bmf) at a triosmium cluster and P-C bond cleavage in the unsaturated cluster 1,1-Os3(CO)9(bmf): Synthesis and X-ray diffraction structures of the isomeric Os3(CO) 10(bmf) clusters and HOs3(CO)8(μ-C 6H4)

Srikanth Kandala, Li Yang, Charles F. Campana, Vladimir Nesterov, Xiaoping Wang, Michael G. Richmond

Research output: Contribution to journalArticlepeer-review

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Abstract

The labile cluster 1,2-Os3(CO)10(MeCN)2 (1) reacts with the chiral diphosphine ligand 3,4-bis(diphenylphosphino)-5- methoxy-2(5H)-furanone (bmf) to furnish 1,2-Os3(CO)10(bmf) (2a) in high yield. Heating cluster 2a over the temperature range 358-383 K under CO leads to isomerization of the bmf ligand and formation of the diphosphine-chelated cluster 1,1-Os3(CO)10(bmf) (2b) and an equilibrium mixture consisting of 2a and 2b in a 15:85 ratio. Extended thermolysis of an equilibrium mixture of Os3(CO)10(bmf) is accompanied by CO loss and ortho-metalation of an aryl ring to afford an inseparable mixture of three diastereomeric hydride clusters HOs 3(CO)9(C29H23O3P 2) (3a-c). Thermolysis of HOs3(CO)9(C 29H23O3P2) (3a-c) in refluxing toluene leads to P-C bond cleavage and formation of the benzyne-substituted clusters HOs3(CO)8(μ-C6H4)(μ- C23H19O3P2) (4a,b) as a 4:1 mixture of diastereomers. The unequivocal identity of the major benzyne-substituted cluster has been determined by X-ray diffraction analysis, where the activation of one of the phenyl groups situated α to the furanone carbonyl group in the bmf ligand has been established. The isomerization and activation of the bmf ligand are contrasted with other Os3(CO)10(diphosphine) derivatives prepared by our groups.

Original languageEnglish
Pages (from-to)2814-2821
Number of pages8
JournalPolyhedron
Volume29
Issue number14
DOIs
StatePublished - Sep 22 2010

Funding

Financial support from the Robert A. Welch Foundation (Grant B-1093-MGR) is greatly appreciated. X. Wang acknowledges the support by the US Department of Energy, Office of Science, under Contract No. DE-AC05-00OR22725 managed by UT Battelle, LLC. Prof. Arnold Rheingold is thanked for his hospitality and the use of his X-ray diffractometer that was used to collect the X-ray data on the isomeric clusters 2a,b during the 2004 ACS-PRF summer school on Crystallography for Organic Chemists.

Keywords

  • Crystallography
  • Diphosphine ligand
  • Ligand substitution
  • Osmium clusters
  • P-C bond-activation

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