Supported σ‐Complexes of Li−C Bonds from Coordination of Monomeric Molecules of LiCH(3), LiCH(2)CH(3) and LiC(6)H(5) to Mo≣Mo Bonds

LiCH(3) and LiCH(2)CH(3) react with the complex [Mo(2)(H)(2)(μ‐Ad(Dipp2))(2)(thf)(2)] (1⋅thf) with coordination of two molecules of LiCH(2)R (R=H, CH(3)) and formation of complexes [Mo(2){μ‐HLi(thf)CH(2)R}(2)(Ad(Dipp2))(2)], 5⋅LiCH(3) and 5⋅LiCH(2)CH(3) , respectively (Ad(Dipp2)=HC(NDipp)(2); Dipp=2,6‐( i )Pr(2)C(6)H(3); thf=C(4)H(8)O). Due to steric hindrance, only one molecule of LiC(6)H(5) adds to 1⋅thf generating the complex [Mo(2)(H){μ‐HLi(thf)C(6)H(5)}(μ‐Ad(Dipp2))(2)], (4⋅LiC(6)H(5) ). Computational studies disclose the existence of five‐center six‐electron bonding within the H−Mo≣Mo−C−Li metallacycles, with a mostly covalent H−Mo≣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 (6,7)Li,(1)H and (6,7)Li,(13)C NMR coupling constants found for the three‐atom H−Li−C chains. By contrast, the phenyl group in 4⋅LiC(6)H(5) coordinates in an η(2) fashion to the lithium atom through the ipso and one of the ortho carbon atoms.