Insertion reactions of carbon dioxide into Zn-N bonds: syntheses and structures of tetrameric and dimeric alkylzinc carbamato complexes.

The formal insertions of carbon dioxide into a series of methylzinc dialkylamide complexes (MeZnNR(2)) initially form solvent-free, tetrameric zinc carbamato complexes [Me(4)Zn(4)(O(2)CNR(2))(4)] (NR(2) = N(i-Pr)(2) (1), N(i-Bu)(2) (2), and piperidinyl (3)). These compounds have been characterized by traditional techniques as well as by single-crystal X-ray diffraction analyses. The tetrameric backbones seen in the solid state for 1-3 were structurally similar to each other. Addition of excess pyridine (py) to 1-3 breaks apart the tetramers and converts them into solvated dimeric species [Me(2)Zn(2)(O(2)CNR(2))(2)(py)(2)] (NR(2) = N(i-Pr)(2) (4), N(i-Bu)(2) (5), and piperidinyl (6)). X-ray crystallographic analyses of 4 and 5 confirmed the dimeric structure in the solid state. This study significantly increases the number of well-characterized zinc carbamates prepared via CO(2) insertion into zinc amides.