047 475 preferred bridging groups are dialkyl silyls u2014 especially dimethyl silyl the amine portion of the ligand preferably has an alkyl substituent on the nitrogen atom especially tertiary butyl with the remaining nitrogen bands bonding to the transition metal preferably titanium and the silicon atome of the preferred dimethyl silyl bridging group the cyclopentadienyl ligand is pi bonded to the transition metal and covalently bonded to the bridging group the cyclopentadienyl group is preferably substituted especially tetra methyl cyclopentadienyl preferred catalyst compounds include dimethylsilyltetramnethyl cyclopentadienyl tertiary butyl amido titanium di chloride and the alkyl analogues u2014 i e with the two chloride ligands being replaced by simple alkyls especially methyl and the catalyst compounds illustrated in the present examples u s pat nos 5 057 475 and 5 064 802 are also illustrated in the present examples where m is a group 3 to 16 metal atom or a metal selected from the group of actinides and lanthanides of the periodic table of elements preferably m is a group 4 to 12 transition metal and more preferably m is a group 4 5 or 6 transition metal and most preferably m is a group 4 transition metal in any oxidation state especially titanium l c is a substituted or unsubstituted bulky ligand bonded to m j is bonded to m a is bonded to m and j j is a heteroatom ancillary ligand and a is a bridging group q is a univalent anionic ligand and n is the integer 0 1 or 2 in formula iii pr 2 u2014 h and substituted or unsubstituted aryl groups with the proviso that when q is u2014 nr u2014 then z is selected from one of the group consisting of u2014 or u2014.