LEWIS BASE STABILIZED TRANSITION-METAL COMPLEXES OF DIVALENT SILICON SPECIES

A direct photochemical synthesis of silanediyl-iron tetracarbonyl complexes Ph(2)Si(B)=Fe-(CO)(4) [B = 1,3-dimethylimidazolidinone (DMI) or hexamethylphosphoric triamide (HMPA)] is described. The Lewis base character of DMI is strong enough to quantitatively convert the dimeric [Fe-2(CO)(8)(SiPh(2))(2)] to more stable Ph(2)Si(DMI)=Fe(CO)(4). A series of organosilanediyl-transition metal complexes, of general formula ArAr'Si=MLn [Ar = Ph, Ar' = [2-(Me(2)NCH(2))C6H4], [8-(Me(2)NCH(2))C10H6], [8-(Me(2)N)C10H6]; Ar, Ar' = [2-(Me(2)NCH(2))C6H4]; Ar = 1-Np, Ar' = [8-(Me(2)NCH(2))C10H6]; or Ar = Me, Ar' = [2-(Me(2)NCH(2))C6H4]] is directly obtained in the photochemical reaction of ArAr'SiH2 with Fe(CO)(5), Cr(CO)(6), Mo(CO)(6), and RCpMn(CO)(3) (R = Me, H). Single-crystal X-ray structure analysis of the complex [2-(Me(2)NCH(2))C6H4]C6H5Si = Fe(CO)(4) (5a) reveals a N-->Si bond length of 1.962(2)Angstrom and Si-Fe bond distance of 2.259(1)Angstrom. The sum of bond angles at silicon, excluding the N-atom, is to 346.7 degrees. Crystal data: C19H17FeNO4Si, triclinic, space group P1 (No. 2), a = 8.284(2), b = 8.404(2), c = 13.497(3)Angstrom; alpha = 97.02(1)degrees, beta = 93.68(1)degrees, gamma = 91.25(1)degrees, V = 930.3 Angstrom(3), Z = 2, R = 0.027, R omega = 0.030 based on 3171 reflections with (I > 0.00, all data). Strong intramolecular donor stabilization with the 8-[(dimethylamino)methyl]naphthyl ligand directly bonded to the silicon atom prevents further reactions, but typical experiments have been performed with less coordinated 8-[(dimethylamino)methyl]phenyl derivatives. Silanediyl-iron tetracarbonyl complexes react with acetylenes, dienes, and alcohols under UV irradiation, and trapping products of silylenes are isolated in good yields. A comparative study of different coordinating ligands has been carried out.