Synthesis, Characterization and Electrochemical Properties of Stable Osmabenzenes Containing PPh₃ Substituents

Abstract

Treatment of [OsCl(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond]CH/PPh(3) produces the osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)][OH] (2), which is air stable in both solution and solid state. The key intermediate of the one-pot reaction, [OsCl(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (3), and the related complex [Os(NCS)(2){CHC(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (7) have been isolated and characterized, further supporting the proposed mechanisms for the reaction. Reactions of 3 with PPh(3), NaI, and NaSCN give osmabenzene 2, iodo-substituted osmabenzene [Os{CHC(PPh(3))CHCICH}I(2)(PPh(3))(2)] (4), and thiocyanato-substituted osmabenzene [Os{CHC(PPh(3))CHC(SCN)CH}(NCS)(2)(PPh(3))(2)] (5) respectively. Similarly, reaction of [OsBr(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond] CH in THF produces [OsBr(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (9), which reacts with PPh(3)/Bu(4)NBr to give osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Br(2)(PPh(3))(2)]Br (10). Ligand substitution reactions of 2 produce a series of new stable osmabenzenes 11-17. An electrochemical study shows that osmabenzenes 2, 12, and 14-17 have interesting different electrochemical properties due to the different co-ligand. The oxidation potentials of complexes 2, 12, 16, and 17 with Cl, NCS, and N(CN)(2) ligands gradually positively shift in the sequence of Cl<NCS<N(CN)(2). Among the six compounds, only 12 and 17 undergo a well-behaved, nearly reversible and a quasi-reversible reduction process, respectively, indicating that two NCS or N(CN)(2) ligands contribute to the stabilization of their reduced states.

m‐Metallaphenol: Synthesis and Reactivity Studies

“…Similar to our previously reported mechanism for the formation of osmabenzene [(SCN) 2 (Ph 3 P) 2 Os{CHC(PPh 3 )CHC(SCN)CH}] from complex 1 ,7b the formation of osmaphenol may also involve the nucleophilic addition and elimination process. As shown in Scheme , 1 could undergo intermolecular nucleophilic addition with the H 2 O present in solution to give the O‐protonation intermediate A .…”

Interconversion of Metallabenzenes and Cyclic η2‐Allene‐Coordinated Complexes

“…However, the carbon–carbon bond distances of the metallacycle are in the range of 1.389(9)–1.422(9) Å. A similar delocalized metallabenzene structure without a planar metallacycle was observed in our previously reported metallabenzene with a 2,2′‐dipyridyl ligand 10b. 11…”

Synthesis, Structure, and Reactivity of an Osmacyclopentene Complex

“…From our previous work on metallacycle chemistry, we know that exchanging the ligands from Cl to SCN would make metallaorganic complexes more stable. 5,13 As expected, complex 8 and stable chloro-osmabenzene 9 can be isolated and characterized successfully by addition of NaSCN to the reaction mixture (see Scheme 5).…”