Metalorganic Synthesis of Modified Polycarbosilanes. I. Benzylidene Bridged PolycarbosilanesBy single step reaction of the monomeric silanes diphenyl‐, phenylmethyl, dimethyl‐, methyl‐vinyl‐ and methyldichlorosilanes with α,α‐dibromotoluene as carbosilane bridge builder and magnesium as reducing agent a series of modified linear polycarbosilanes was prepared. This new synthetic route – a simple variation of the Grignard method – allowed the synthesis of the oligomeric products in large amounts. In addition, the sensitive functional groups SiH and SiCH  CH2were completely preserved during the course of the reaction, in contrast to the direct synthesis with sodium as reductive agent.The structures of the viscous polycarbosilanes were characterized by a highly rate of alternating Si‐C‐systems.The modified polycarbosilanes were analysed and investigated by IR‐,1H‐,13C‐ and29Si‐NMR‐spectroscopy. The weight and number averages Mwand Mn, which were determined by gel‐permeation chromatography, clearly reflected the oligom