Research Projects

The selective cleavage and functionalization of unreactive C H bond of organic molecules catalyzed by transition metal complexes has been a long term research goal in organic synthesis.1 Functionalizing traditionally inert C-H bonds under mild and efficient catalytic reaction conditions represents a powerful transformation, providing new entries to valuable structural motifs and improving the overall synthetic efficiancy. Particularly, alkanes are the major constituents of natural gas and crude oil. Thus, the direct transformation of the C H bond of abundant and low-cost hydrocarbon feedstocksinto highly valuable organic products have a great impact on the chemical industry. Generally, the C H bond of organic molecules can be activated in two different ways: a) directed C-H bond activation and b) non-directed C H bond activation. In the directing group assisted C H bond activation, the reaction typically proceeds by a mechanism involving initial formation of a [C–H⋯M] σ-complex. The presence of a directing group such as a lewis basic functional group containing non-bonding lone pair of electrons, facilitates C-H bond cleavage by inducing pre-association with the metal and substrate. However, the π-bond assisted C H bond activation is difficult and highly challengingowing to its weaker coordination and less chelating nature than the lonepair coordination with the metal complexes. On the otherhand, non-directed C−H bond functionalization reactions are less focused than the directed C−H bond functionalization mainly due to the lack of regioselectivity.It has been clearly observed that the C H bond can coordinate with the metal species which weakness the bond via the π-back donation from a filled π(d) orbital of the metal to the empty σ*(C H) orbital of the alkane. Few reactions are known in this area, however controlling the regioselectivity of the product is a difficult task and often leads to mixture of products. Selective activation of the targeted C-H bond is difficult since the metal cannot distingush various C-H bonds present in the molecule. Due to the selectivity issue, only less focus has been devoted in this area. In thisproposal, several cationic and neutral ruthenium complexes would be synthesized and can be utilised for various direct organic transformation of alkanes in the absence of a directing group.