Cocatalysts with cyclopentadienyl groups

Palladium complexes with an heterocyclic N-containing ligand have been used in the carbonylation of aromatic nitro compounds with cocatalysts such as cyclopentadienyl halides or oxyhalides of transition metals belonging to group V e.g. CP2VCI) [168], a cyclopentadienyl halide or oxyhalide together with phosphorus oxytrichloride [169], or a 1,3-diketone derivative of vanadium [170], even also in the presenee of phosphorus oxychloride [171]. 

The most investigated homogeneous catalyst systems are based on bis(cyclopenta-dienyl)titanium(lV), bis(cyclopentadienyl)zirconium(rV), tetrabenzyltitanium, vanadium chloride, and trialkylaluminum or alkylaluminum halides as cocatalysts. Subsequent research on these and other systems with various alkyl groups has been conducted by Patat and Sinn [4], Shilov [5], Hemici-Olive and Olive [6], Reichert and Schoetter [7], and Fink et al. [8]. 

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