Tri and hexaosmium clusters bearing saccharinate and diphosphine ligands: Synthesis, structure and fluxionality

• Published in: Journal of organometallic chemistry Vol. 1015; p. 123212
• Main Authors: Hasan, Md. Sohag, Alam, Md. Mahbub, Parvin, Mir Khaleda, Rajbangshi, Subas, Nesterov, Vladimir N., Kabir, Shariff E., Ghosh, Shishir
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-07-2024
• Subjects: Carbonyls; Dppf; Dppm; Osmium clusters; Saccharinate (sac); X-ray structures; Dppm; Dppf; Osmium clusters; Saccharinate (sac); X-ray structures; Carbonyls
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2024.123212

•Reactions of saccharinate-bridged triosmium cluster with diphosphines.•Synthesis and structure of tri- and hexaosmium clusters bearing saccharinate and diphosphine ligands.•Different coordination modes of diphosphines.•Fluxional behavior of coordinated diphosphines in solution.
The reactivity of saccharinate-bridged triosmium cluster [Os3(CO)10(μ-H)(μ-sac)] (1) with two diphosphines namely bis(diphenylphosphino)methane (dppm) and 1,1′-bis(diphenylphosphino)ferrocene (dppf) have been investigated. Cluster 1 reacts with dppm in refluxing toluene to yield triosmium [Os3(CO)9(κ1-dppm)(μ-H)(μ-sac)] (2), [Os3(CO)9(κ1-dppm)(μ-H)(μ-sac)] (3) and [Os3(CO)8(µ-dppm)(μ-H)(µ-sac)] (4) along with the hexaosmium [{Os3(CO)9(μ-H)(µ-sac)}2(κ2-dppm)] (5). The dppm ligand acts as a monodentate ligand in 2 and 3 by coordinating to a single osmium, while it bridges an osmium-osmium edge in 4 and connects to triosmium units in 6. A similar reaction with dppf furnishes [Os3(CO)9(κ1-dppf)(μ-H)(μ-sac)] (6), [Os3(CO)8(µ-dppf)(μ-H)(μ-sac)] (7) and [{Os3(CO)9(μ-H)(µ-sac)}2(κ2-dppf)] (8) which are dppf analogues of 3–5, respectively. Control experiments confirms that 3 is the precursor of 4 and 5, while 6 is the precursor of 7 and 8. All the products are formed via substitution of carbonyl by the diphosphine, and have been characterized by analytical and spectroscopic data. The molecular structures of 2 and 4–7 have been determined by X-ray crystallography. Cluster 7 shows fluxional behavior in solution at room temperature, and its fluxionality has been probed by VT NMR experiments.
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