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Synthesis, Structural Characterization, Solvatochromism, and Electrochemistry of Tetra‐Osmium Carbonyl Clusters Containing Azo‐Ligands
Author(s) -
Li Yat,
Lin ZhenYang,
Wong WingTak
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200112)2001:12<3163::aid-ejic3163>3.0.co;2-q
Subject(s) - chemistry , osmium , solvatochromism , tetra , electrochemistry , characterization (materials science) , photochemistry , polymer chemistry , inorganic chemistry , combinatorial chemistry , organic chemistry , molecule , ruthenium , nanotechnology , electrode , medicinal chemistry , catalysis , materials science
The reaction of [Os 4 (μ‐H) 4 (CO) 12 ] with 4‐(2‐pyridylazo)‐ N , N ‐dimethylaniline (PNNDA) in dichloromethane afforded the new clusters [Os 4 (μ‐H) 4 (CO) 11 {NC 5 H 4 (N=N)C 6 H 4 NMe 2 }] ( 1 ) and [Os 4 (μ‐H) 4 (CO) 10 {η 2 ‐NC 5 H 4 (N=N)C 6 H 4 NMe 2 }] ( 2 ) in 34% and 15% yields, respectively. Upon heating in toluene under reflux, compound 1 converted into 2 in 80% yield. The MLCT transition of compound 2 shows strong solvent dependency, displaying unusually large positive solvatochromism in different organic solvents. Treatment of [Os 4 (μ‐H) 4 (CO) 12 ] with 2‐(5‐bromo‐2‐pyridylazo)‐5‐(diethylamino)phenol (Br‐PADAP) in dichloromethane gives [Os 4 (μ‐H) 3 (CO) 10 {μ‐η 3 ‐Et 2 NC 6 H 3 (O)(N=N)C 5 NH 3 Br}] ( 3 ). The O−H bond activation is observed and the azo‐ligand behaves as a five‐electron donor. The clusters [Os 4 (μ‐H) 2 (CO) 10 {μ‐η 3 ‐NC 5 H 4 (N=N)C 5 H 4 N}] ( 4 ) and [Os 4 (μ‐H) 4 (CO) 10 {μ‐η 2 ‐NC 5 H 4 (N=N)C 5 H 4 N}] 2 ( 5 ) were isolated from the reaction of [Os 4 (μ‐H) 4 (CO) 10 (NCMe) 2 ] with 2,2′‐azopyridine and 3,3′‐azopyridine, respectively. In compound 4 , both pyridine and azo nitrogen atoms were found to coordinate to the cluster core. Dehydrogenation was also observed in this compound. For compound 5 , two tetra‐osmium metal cores were connected by two azo ligands through their pyridyl nitrogen atoms to form a novel cyclic structure. The redox properties of the compounds described herein were investigated by means of cyclic voltammetry and controlled potential coulometry. Both compound 2 and 5 exhibit a reversible cathodic wave, which indicates that they undergo addition of one electron without significant structural changes. Furthermore, compound 5 displays an electronic interaction between two redox centers, the extra electrons are believed to delocalize throughout the cyclic structure.