Patent ID: 7041841

Claim:
A compound represented by the formula: wherein M is Hf or Zr in its highest formal oxidation state; where the cyclopentadienyl ring which is symmetrically substituted with two or four substituent groups R, with “x” denoting the degree of substitution (x=2 or 4) and each R is, independently, a radical selected from a group consisting of C 1 –C 20 hydrocarbyl radicals, substituted C 1 –C 20 hydrocarbyl radicals wherein one or more hydrogen atoms is replaced by a halogen radical, an amido radical, a phosphido radical, an alkoxy radical or any other radical containing a Lewis acidic or basic functionality, C 1 –C 20 hydrocarbyl-substituted metalloid radicals wherein the metalloid is selected from the Group IV A of the Periodic Table of Elements, and halogen radicals, amido radicals, phosphido radicals, alkoxy radicals, alkylborido radicals and radicals containing Lewis acidic or basic functionality, or at least two adjacent R-groups are joined forming C 4 –C 20 ring to give a saturated or unsaturated polycyclic cyclopentadienyl ligand; (JR′ z-2 ) is a heteroatom ligand in which J is an element with a coordination number of three from Group V A or an element with a coordination number of two from Group VI A of the Periodic Table of Elements, and each R′ is, independently a radical selected from a group consisting of C 1 –C 20 hydrocarbyl radicals, substituted C 1 –C 20 hydrocarbyl radicals where one or more hydrogen atom is replaced by a halogen radical, an amido radical, a phosphido radical, and alkoxy radical and any other radicals containing a Lewis acidic or basic functionality, and “z” is the coordination number of the element J; each Q is, independently, any univalent anionic ligand, such as a halide, hydride, or a substituted or unsubstituted C 1 –C 20 hydrocarbyl, alkoxide, aryloxide, amide, arylamide, phosphide or arylphosphide, or both Q together are an alkylidene, or a cyclometallated hydrocarbyl or any divalent anionic chelating ligand; T is a covalent bridging group containing a Group IV A or V A element; and L is a neutral Lewis base where “w” denotes a number from 0 to 3.