Supported σ-Complexes of Li-C Bonds from Coordination of Monomeric Molecules of LiCH3, LiCH2CH3 and LiC6H5 to Mo(sic)Mo Bonds

LiCH3 and LiCH2CH3 react with the complex [Mo-2(H)(2)(mu-Ad(Dipp2))(2)(thf)(2)] (1 center dot thf) with coordination of two molecules of LiCH2R (R=H, CH3) and formation of complexes [Mo-2{mu-HLi(thf)CH2R}(2)(Ad(Dipp2))(2)], 5 center dot LiCH3 and 5 center dot LiCH2CH3, respectively (Ad(Dipp2)=HC(NDipp)(2); Dipp=2,6-(Pr2C6H3)-Pr-i; thf=C4H8O). Due to steric hindrance, only one molecule of LiC6H5 adds to 1 center dot thf generating the complex [Mo-2(H){mu-HLi(thf)C6H5}(mu-Ad(Dipp2))(2)], (4 center dot LiC6H5). Computational studies disclose the existence of five-center six-electron bonding within the H-Mo(sic)Mo-C-Li metallacycles, with a mostly covalent H-Mo(sic)Mo-C group and predominantly ionic Li-C and Li-H interactions. However, the latter bonds exhibit non-negligible covalency, as indicated by X-ray, computational data and the large one-bond Li-6,Li-7,H-1 and Li-6,Li-7,C-13 NMR coupling constants found for the three-atom H-Li-C chains. By contrast, the phenyl group in 4 center dot LiC6H5 coordinates in an eta(2) fashion to the lithium atom through the ipso and one of the ortho carbon atoms.

Automated summary

LiCH3 and LiCH2CH3 react with complex [Mo-2(H)(2)(μ-Ad(Dipp2))(2)(thf)(2)] (1 center dot thf) to form complexes with coordination of LiCH2R (R=H, CH3). Computational studies reveal the existence of five-center six-electron bonding within the H-Mo(sic)Mo-C-Li metallacycles, with predominantly ionic Li-C and Li-H interactions.