Silyl and σ-silane ruthenium complexes: Chloride substituent effects on the catalysed silylation of ethyleneElectronic supplementary information (ESI) available: DFT data. CCDC reference numbers 765257(8MeCl2) and 765258(6MeCl2). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt00065e

Silylation of ethylene by the chlorosilanes HSiMe2Cl and HSiMeCl2was catalysed by the bis(dihydrogen) complex RuH2(η2-H2)2(PCy3)2(1). Dehydrogenative silylation leading to the formation of the corresponding vinylsilanes was in competition with hydrosilylation. The rate and selectivity of the reactions were influenced by the number of chloro substituents and the ethylene pressure. A comparative mechanistic study was performed in toluene-d8with the two chlorosilanes. Reaction of 1with an excess of HSiMe2Cl (10 equiv.) produced the σ-silane complexes RuH2(η2-H2)(η2-HSiMe2Cl)(PCy3)2(2Me2Cl), RuH2(η2-HSiMe2Cl)2(PCy3)2(3Me2Cl) and the silyl complex RuCl(SiMe2Cl)(η2-H2)(PCy3)2(4Me2Cl), all characterised by multinuclear NMR spectroscopy. Complexes 2Me2Cland 3Me2Cladopt a cisconfiguration for the two bulky phosphine ligands as a result of stabilising SISHA (Secondary Interactions between Silicon and Hydrogen Atoms) interactions. Complex 4Me2Clresulted from the stoichiometric reaction of HSiMe2Cl with 1producing RuHCl(η2-H2)(PCy3)2in situwhich further reacted with evolution of H2and formation of 4Me2Cl. When reacting 1with 10 equiv. of HSiMeCl2, the corresponding complexes 3MeCl2and 4MeCl2were detected as well as traces of 2MeCl2. The reactivity toward ethylene was then examined. Under catalytic conditions (excess silane in toluene-d8, ethylene atmosphere) only two compounds could be characterised: free PCy3and the new (η6-aryl)(disilyl) complexes of the general formula Ru(η6-C6D5CD3)(SiMe3−nCln)2(PCy3) (6Me3−nCln-d8, n= 1,2). The X-ray structure of 6MeCl2was obtained on a single-crystal at 160 K. When only 2 equiv. of HSiMe2Cl were added, the ethylene(silyl) complex RuH(SiMe2Cl)(C2H4)(PCy3)2(7Me2Cl) was obtained in addition to the organic products resulting from catalytic hydrogenation, hydrosilylation and dehydrogenative silylation, i.e.C2H6(major one), C2H3SiMe2Cl and C2H5SiMe2Cl. In the case of 2 equiv. of HSiMeCl2, upon ethylene addition, 7MeCl2was formed in minority compared to a new disilyl complex Ru(SiMeCl2)2(PCy3)2(8MeCl2) characterised by NMR spectroscopy and X-ray diffraction on a single crystal at 160 K. In 8MeCl2, a formal 14-electron species, stabilisation through two agostic C–H bonds of the cyclohexyl groups was ascertained by DFT calculations. [ABSTRACT FROM AUTHOR]