title: m-Metallaphenol: synthesis and reactivity studies.
abstract: Treatment of the osmium complex [Os{CHC-(PPh3 )CH(OH)-η(2) -C≡CH}(PPh3 )2 (NCS)2 ] (1) with excess triethylamine produces the first m-metallaphenol complex [Os{CHC(PPh3 )CHC(OH)CH}(PPh3 )2 (NCS)2 ] (2). The NMR spectroscopic and structural data as well as the nucleus-independent chemical-shift (NICS) values suggest that osmaphenol 2 has aromatic character. The reactivity studies demonstrate that 2 can react with different isocyanates to form the annulation reaction products [Os{CHC(PPh3 )CHC(OCONR)C}(PPh3 )2 (NCS)2 ] (R=Ph (3), iPr (7), Bn (8)) via the carbamate intermediates [Os{CHC(PPh3 )CHC(O-CONHR)CH}(PPh3 )2 (NCS)2 ] (R=Ph (4), iPr (5), Bn (6)). In addition, the similar annulation reactions can be extended to other unsaturated compounds containing N-C multiple bonds, for example, isothiocyanates, pyridine, and sodium thiocyanate, which can produce the corresponding fused osmabenzene complexes. In contrast, the reactions of 2 with common electrophiles, such as NOBF4 , NO2 BF4 , N-bromosuccinimide, and N-chlorosuccinimide only led to the decomposition of the metallaphenol ring. The experimental results suggest that 2 is very electrophilic and readily reacts with nucleophiles, which is mainly due to the metal center and the strong electron-withdrawing phosphonium group.
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005 (P. R. China).
authors.forename: Feifei
authors.initials: F
authors.lastname: Han
authors.forename: Tongdao
authors.initials: T
authors.lastname: Wang
authors.forename: Jinhua
authors.initials: J
authors.lastname: Li
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Haiping
authors.initials: H
authors.lastname: Xia
keywords: annulation reactions; metallaphenols; nucleophilic aromatic substitution; reactivity studies; synthesis