Saleem Al-Ahmad

BORATABENZENES : FROM CHEMICAL CURIOSITIES TO PROMISING CATALYSTS

Abstract Boratabenzenes ( 4 ) are six π-electron aromatic anions which can serve as versatile ligands towards Zr(IV) and Zr(II). The reaction of 4 with ZrCl 4 affords bis(boratabenzene)zirconium(IV) dichlorides ( 11 ), which on treatment with BuLi and excess PMe 3 give bis(boratabenzene)bis(trimethylphosphine)zirconium(II) ( 27 ). On activation by excess methylaluminoxane 11 are the catalysts for the polymerization or oligomerization of ethylene. Bridged boratabenzene zirconium dichlorides 19 , 20 , and 21 , which closely resemble the corresponding ansa-zirconocenes, can be similarly activated for polymerization of ethylene. Compound 27 reacts with 1,3-diynes to afford zirconacycles 31 and with acetylene by ring annulation to afford 32 .

Boratabenzene Zirconium Complexes

1-Substituted boratabenzenes (1) are six π-electron aromatic anions which can serve as surrogates for cyclopentadienyl in important organometallic compounds. The reaction of 1 with ZrCl4 produces bis(boratabenzene) zirconium(IV) dichlorides 3, which when activated by excess methylaluminoxane react with ethylene to produce either high molecular weight polyethylene or smaller ethylene oligomers, depending upon the substituents at boron. The reaction of 3 with BuLi in the presence of PMe3 affords the corresponding zirconium(II) complexes (4). The reaction of 4 with acetylene involves an unprecedented ring annulation to afford complexes which contain the novel ligand lOH-5-boratanaphthalene.

1,1′-Diheteroferrocenes of the Group 15 Elements

Abstract Polymethyl-1,1′-diheteroferrocenes have been prepared. Their X-ray structures and chemistry are compared.