Mechanism of Me–Re Bond Addition to Platinum(II) and Dioxygen Activation by the Resulting Pt–Re Bimetallic Center

• Published in: Inorganic chemistry 2017-02, Vol.56 (4), p.2145-2152
• Main Authors: Pichaandi, Kothanda Rama, Kabalan, Lara, Amini, Hashem, Zhang, Guanghui, Zhu, Hanyu, Kenttämaa, Hilkka I, Fanwick, Phillip E, Miller, Jeffrey T, Kais, Sabre, Nabavizadeh, S. Masoud, Rashdi, Mehdi, Abu-Omar, Mahdi M
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.6b02801

Unusual cis-oxidative addition of methyltrioxorhenium (MTO) to [PtMe2(bpy)], (bpy = 2,2′-bipyridine) (1) is described. Addition of MTO to 1 first gives the Lewis acid–base adduct [(bpy)­Me2Pt–Re­(Me)­(O)3] (2) and subsequently affords the oxidative addition product [(bpy)­Me3PtReO3] (3). All complexes 1, MTO, 2, and 3 are in equilibrium in solution. The structure of 2 was confirmed by X-ray crystallography, and its dissociation constant in solution is 0.87 M. The structure of 3 was confirmed by extended X-ray absorption fine structure and X-ray absorption near-edge structure in tandem with one- and two-dimensional NMR spectroscopy augmented by deuterium and 13C isotope-labeling studies. Kinetics of formation of compound 3 revealed saturation kinetics dependence on [MTO] and first-order in [Pt], complying with prior equilibrium formation of 2 with oxidative addition of Me–Re being the rate-determining step. Exposure of 3 to molecular oxygen or air resulted in the insertion of an oxygen atom into the platinum–rhenium bond forming [(bpy)­Me3PtOReO3] (4) as final product. Density functional theory analysis on oxygen insertion pathways leading to complex 4, merited on the basis of Russell oxidation pathway, revealed the involvement of rhenium peroxo species.