Halogen exchange reactions in preparing catalysts and their precursors

Abstract

Chloropentafluorobenzene or bromopentafluorobenzene is formed by heating perhalobenzene, C,F,X,where n is 0 to 4, and each X is, independently, a chlorine or bromine atom, with alkali metal fluoride, and an aminophosphonium catalyst (e.g., (Et,N),PBr). The resultant chloropentafluorobenzene or bromopentafluorobenzene can be converted into a pentafluorophenyl Grignard reagent or a pentafluorophenyl alkali metal compound. This in turn can be converted into tris(pentafluorophenylborane), which can be converted into a single coordination complex comprising a labile tetra(pentafluorophenyl)boron anion (e.g., a trialkylammonium tetra(pentafluorophenyl) boron complex or an N,N-dimethylanilinium tetra(pentafluorophenyl)boron complex). The complex can be used in the preparation of an active catalyst by mixing the complex with a cyclopentadienyl metal compound containing a Group 4 metal in suitable solvent or diluent so that the cation of the complex reacts irreversibly with a ligand of the cyclopentadienyl compound, and such that the pentafluorophenyl anion forms a non-coordinating ion pair with a resulting cation produced from the cyclopentadienyl metal compound. Alternatively, the tris(pentafluorophenylborane) can be contacted with a metallocene of the formula LMX,wherein L is a derivative of a delocalized pi-bonded group imparting a constrained geometry to the metal active site and where L contains up to 50 non-hydrogen atoms, M is a Group 4 metal, and each X is, independently, hydride, or a hydrocarbyl, silyl, or germyl group having up to 20 carbon, silicon, or germanium atoms to form a catalyst having a limiting charge separated structure of the formula LMX,XA,wherein A is an anion formed from the tris(pentafluorophenyl)borane.