Synthesis and structural studies of germyl and germyl/stannyl substituted tungstenocenes

Abstract

One-pot reactions of [WCp₂(H)₂] and [WCp₂(H)(SnMe₃)] with ⁿBuLi followed by an equivalent of GeMe₂Cl₂ afford mono(germyl) substituted tungstenocenes [WCp₂(H)(GeMe₂Cl)] (1) and [WCp₂(SnMe₃)(GeMe₂Cl)] (7). Reactions of the products with tin halides in the presence NEt₃ afford the mixed complexes [WCp₂(SnR₂X)(GeMe₂Y)] (X, Y = Cl, Br, RMe, Et), which were further converted to moderately stable compounds [WCp₂(SnR₂H)(GeMe₂H)] (R = Me (10), Et (11)). A number of asymmetric mono(halo)-substituted germyl/stannyl tungstenocenes [WCp₂(SnMe₂X)(GeMe₂H)] (X = Cl (12), Br (13)) and [WCp₂(SnEt₂Y)(GeMe₂H)] (Y = Br (14), I (15)) were prepared by selective halogenation of the Sn–H bond in 10 and 11. X-Ray studies of [WCp₂(H)(GeMe₂Cl)] (1), [WCp₂(SnEt₂Br)(GeMe₂Cl)] (4), and [WCp₂(SnEt₂Br)(GeMe₂H)] (14) established classical structures of these compounds. X-Ray study of complex [WCp₂(SnMe₂Cl)(GeMe₂Cl)] (3) revealed the presence of interligand Ge–Cl⋯Sn–Cl interactions in a highly Ge/Sn disordered structure. Analyses of molecular parameters of 1, 4, and 14 suggest the presence of a negative hyperconjugation between metal lone pairs and the σ*-orbital of the E–X bond, which is stronger in bromo substituted complexes in comparison with chloro substituted ones.