FUNCTIONALIZATION OF THE MU-SILYLENE LIGAND IN CP2FE2(CO)(3)(MU-SIH(T)BU) - SYNTHESES OF MU-HALOSILYLENE COMPLEXES CP2FE2(CO)(3)(MU-SIX(T)BU) (X=CL, BR, I) AND DONOR-STABILIZED CATIONIC MU-SILYLYNE COMPLEXES [CP2FE2(CO)(3)(MU-SI(T)BU-CENTER-DOT-BASE)]I (BASE=N-METHYLIMIDAZOLE, 4-(DIMETHYLAMINO)PYRIDINE)

The mu-silylene complex Cp(2)Fe(2)(CO)(3)(mu-SiH(t)Bu) (1) reacts with CCl4, CHBr3, and CH2I2 at room temperature to afford mu-halosilylene complexes Cp(2)Fe(2)(CO)(3)(mu-SiX(t)Bu) (2, X = Cl; 3, X = Br; 4, X = I, respectively). The iodine atom on the silylene bridge in 4 is replaced by strong Lewis bases, N-methylimidazole (NMI) and C(dimethylamino)pyridine (DMAP), to give the first donor-stabilized mu-silylyne dinuclear complexes [Cp(2)Fe(2)(CO)(3)(mu-Si(t)Bu.Base)](+) ([7](+), base = NMI; [8](+), Base = DMAP). The crystal structures of [7]I.CD3CN and [8]I have been determined by X-ray crystallography. Crystals of [7]I.CD3CN are orthorhombic, Pbnm, a = 16.371(4) Angstrom, b = 17.043(3) Angstrom, c = 9.975(1) Angstrom, Z = 4, and R = 0.056. Crystals of [8]I are orthorhombic, Pbnm, a = 14.564(2) Angstrom, b = 18.412(4) Angstrom, c = 10.290(1) Angstrom, Z = 4, and R = 0.070. These compounds have short Fe-Si bond lengths 2.262(2) Angstrom ([7]I.CD3CN) and 2.266(3) Angstrom ([8]I). In contrast, Si-N distances ([7]I.CD3CN, 1.885(7) Angstrom; [8]I, 1.866(9) Angstrom) are considerably longer than typical Si-N single bonds (ca. 1.75 Angstrom), which is consistent with dative interaction between the nitrogen and silicon atoms. Spectroscopic properties of 2[8](+) are also discussed.