Tetraphenylcyclobutadienenickel bromide

Tetraphenylcyclobutadienenickel bromide (XXXIII) on pyrolysis yields nickel bromide and hydrocarbon products including octaphenylcyclo-... 

A similar reaction on tetraphenylcyclobutadienenickel bromide (XXXIII) gave tetraphenylfuran (LXV), not the expected diol (40),... 

Some of the cyclobutadiene complexes [e.g., (XIII) and (XXVIII)] appear to be inert to the action of donor ligands such as phosphines, pyridine, etc. However, a number form adducts. These have not been fully described, but triphenylphosphine adducts of tetramethylcyclobutadienenickel chloride (XIV) (28) and tetraphenylcyclobutadienenickel bromide (XXXIII) (41) and an o-phenanthroline complex (29) of the former have been reported. Other reactions with donor molecules in which the cyclobutadiene-metal bond remains intact are mentioned in Section VI, G. 

Reagents. The lithium metal, containing a maximum of 0.05% sodium, was obtained from the Lithium Corporation of America. Bis(l,5-cycloocta-diene)nickel [(Cod)2Ni)] was prepared by a modification of a known procedure (13). This complex was used to prepare tetrakis(triethylphosphine)nickel [(Et3P)4Ni]. Tetraphenylcyclobutadienenickel(II) bromide dimer was synthesized from stilbene-free diphenylacetylene (14). 

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