A new Ring Opening Metathesis Polymerization (ROMP)-initiator based on an aryloxy-tungsten complex (activated with Me4Sn) anchored on the lowest generation of a carbosilane dendrimer (G0) has been synthesized. The catalytic activity of the W-initiator is studied for the ROMP of norbornene as model substrate, generating starpolymers. However, after complete conversion of the monomer, the Si-core starpolymers react further by a dismutation reaction resulting in branched high molecular weight starpolymers.