Silyl-substituted Tetrylene Carbonyl Complexes

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Transition metal carbonyl complexes are common organometallic reagents and widely used as powerful catalysts in various chemical transformations. In search of environmentally benign and cost-efficient alternatives for transition metals, silicon and tin comprise great interest due to their high natural abundance and low-toxicity. Recently, we have succeeded in synthesis and isolation of silyl-substituted silicon carbonyl complexes (R2Si:⇄:CO) as stable compounds. In a very similar fashion to transition metals, the Si-CO bonding is achieved via sigma-donation of CO lone pair to an empty p orbital of the silylene and the strong C≡O bond is activated by the pi-backdonation, reinforced by bulky sigma-donating silyl groups on the Si center. The preliminary reactivity of silicon carbonyl complexes resembles that of transition metal carbonyls. The main objectives of this project are further reactivity investigations of silicon carbonyl complexes and development and reactivity studies of Ge and Sn analogues. The work programme contains two main parts. WP-1 describes the synthetic routes and preliminary results toward development of the heavier Group 14 carbonyl analogues R2E:⇄:CO (E = Ge, Sn). WP-2 consists of detailed description of the reactivity studies and strategies for development of catalytic transformations mediated by the silyl-substituted tetrylene carbonyl complexes R2E:⇄:CO (E = Si, Ge, Sn). Development of low-valent group 14 element carbonyl complexes will provide greater insights into the fundamental chemical properties of these species, which may emerge as ecologically friendly and cost-effective surrogates for industrially used catalysts.