title: Comparative chemistry of isolable divalent compounds of silicon, germanium, and tin.
abstract: Recent studies of the synthesis, structures, spectroscopic properties, and reactions of a series of isolable metallylenes (R2E:, E = Si (1), Ge (2), and Sn (3); R2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) are summarized. Because these group-14 metallylenes bear the same helmet-like ligand, a straightforward discussion of the element-dependence of the intrinsic properties of the group-14 element divalent compounds is possible. All these metallylenes were monomeric both in solution and in the solid state, indicating the effective steric protection by the ligand against dimerization. A small sigma-pi conjugation between C-Si(substituent) sigma orbitals and the vacant npz orbitals of divalent atoms in R2E: exists and the extent decreases in the order E = Si > Ge > Sn, as evidenced by UV-vis and NMR spectroscopies and X-ray crystallography. However, the extent of the sigma-pi conjugation in metallylenes 1-3 was much smaller than the electron-donating effects of neighboring nitrogen atoms in known stable cyclic diamino-substituted metallylenes, and hence metallylenes 1-3 are regarded as the least electronically perturbed. Comparative studies of the unique reactions among these metallylenes are also discussed.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan. mkira@si.chem.tohoku.ac.jp
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kira
authors.forename: Shintaro
authors.initials: S
authors.lastname: Ishida
authors.forename: Takeaki
authors.initials: T
authors.lastname: Iwamoto
mesh_terms: D002073:Butanes / Q000138:chemical synthesis* / Q000737:chemistry* / Q000302:isolation & purification; D018360:Crystallography, X-Ray; D005857:Germanium / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry* / Q000302:isolation & purification; D012825:Silicon / Q000737:chemistry*; D017655:Silicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry* / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013329:Structure-Activity Relationship; D014001:Tin / Q000737:chemistry*
chemical_list: C493262:1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl; D002073:Butanes; D008024:Ligands; D009942:Organometallic Compounds; D017655:Silicon Compounds; D005857:Germanium; D014001:Tin; D012825:Silicon