title: A Highly Reactive Seven-Coordinate Osmium(V) Oxo Complex: [Os(V)(O)(qpy)(pic)Cl](2+).
abstract: Seven-coordinate ruthenium oxo species have been proposed as active intermediates in catalytic water oxidation by a number of highly active ruthenium catalysts, however such species have yet to be isolated. Reported herein is the first example of a seven-coordinate group 8 metal-oxo species, [Os(V)(O)(qpy)(pic)Cl](2+) (qpy = 2,2':6',2'':6'',2'''-quaterpyridine, pic = 4-picoline). The X-ray crystal structure of this complex shows that it has a distorted pentagonal bipyramidal geometry with an Os=O distance of 1.7375 Å. This oxo species undergoes facile O-atom and H-atom-transfer reactions with various organic substrates. Notably it can abstract H atoms from alkylaromatics with C-H bond dissociation energy as high as 90 kcal mol(-1). This work suggests that highly active oxidants may be designed based on group 8 seven-coordinate metal oxo species.
authors.affiliation: Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China).
authors.forename: Yingying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China).
authors.forename: Siu-Mui
authors.initials: SM
authors.lastname: Ng
authors.affiliation: Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China).
authors.forename: William W Y
authors.initials: WW
authors.lastname: Lam
authors.affiliation: Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China).
authors.forename: Shek-Man
authors.initials: SM
authors.lastname: Yiu
authors.affiliation: Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China). bhtclau@cityu.edu.hk.
authors.forename: Tai-Chu
authors.initials: TC
authors.lastname: Lau
keywords: CH activation; X-ray diffraction; osmium; oxidation; structure elucidation