The synthesis and characterization of tungsten and molybdenum complexes of the xanthene-based bis(silyl) ligand (xantsil) with a kappa3(Si,Si,O) coordination mode are reported, where an insertion of tBuCN into a tungsten-silicon bond leads to formation of an eta2-iminoacyl complex.

Photoinduced decarbonylation of Cp*M(CO)(3)Me (M = Mo and W, Cp* = η(5)-C(5)Me(5)) in the presence of xantsilH(2) [xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)] in pentane gave bis(silyl)hydrido complexes Cp*M(κ(2)Si,Si-xantsil)(CO)(2)(H) (1a: M = Mo and 1b: M = W) through two-fold Si-H oxidative addition and methane elimination. Further irradiation of 1a,b in toluene afforded tridentate xantsil complexes Cp*M(κ(3)Si,Si,O-xantsil)(CO)(H) (2a: M = Mo and 2b: M = W) via CO dissociation. Reactions of complexes 2a,b with nitriles led to stoichiometric hydrosilylation at the C[triple bond, length as m-dash]N triple bond. Thus, reaction of 2a,b with t-BuCN at room temperature afforded N-silyliminoacyl complexes 3a,b, through insertion of a nitrile into the M-Si bond, and the products slowly isomerised to the corresponding N-silylimine complexes 4a,bvia intramolecular hydrogen migration. On the other hand, reaction of 2a,b with PhCN afforded N-silylimine complexes 5a,b directly. The molecular structures of 1a, 3a and 5b were determined by X-ray crystallography, revealing that complex 3a has a 3-centre-2-electron (3c-2e) Mo-Si-H bond.

The cyclic (2+2) template condensation of 2,6-pyridinedicarboxaldehyde with 1,2-bis(2-aminoethoxy) ethane using Pb(SCN) 2 as the metal source gave dinuclear lead(II) complex, Pb 2 L 1 (SCN) 4 (1), where L 1 is tetra-Schiff-base macrocycle. The transmetallation treatment of 1 with suitable metal perchlorate yield [FeL 1 ](ClO 4 ) 2 (2) and [NiL 1 ](ClO 4 ) 2 (3). The complexes (2 & 3) have been characterized by elemental analyses, IR, UV-visible, and ESI-MS spectroscopy. Based on spectral data, octahedral geometry may be proposed for these complexes. The electrochemical behavior of iron and nickel complexes is reported.

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Treatment of a tungsten bis(silyl) complex Cp*W{κ3(Si,Si,O)-xantsil}(CO)(H) [xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)] with 4-(dimethylamino)pyridine (DMAP) causes ortho-metallation in a DMAP-stabilized silylene complex that is generated from the bis(silyl) complex through silicon-to-tungsten 1,2-methyl migration and methane elimination. Resulting W–Si–N–C four-membered metallacycle Cp*W[κ3(Si,Si,C)-(SiMe2){SiMe(NC5H3NMe2)}(C15H12O)](CO)(H) can be regarded as the resonance hybrid of silyl–carbene and pyridyl–silylene complexes.