The fused-ring diheteroaromatic 3a,7a-azaborindenyl anion (1) has been prepared by a synthesis using the Grubbs ring-closing metathesis. 1 has been converted to the Cp*ZrCl2 complex 2, which closely resembles the corresponding (Ind)Cp*ZrCl2.

The heteroaromatic anion lithium 2-(diisopropylamino)-1,2-thiaborolide (3) has been prepared by a synthesis using the Grubbs ring-closing metathesis. 3 has been converted to the Cp*Ru complex 10, the Cp*ZrCl2 complex 11, and the Me2Si-bridged CpZrCl2 complex 15.

1-Arsanaphthalene (3) and 2-trimethylsilyl-1-arsanaphthalene (4) have been prepared from the corresponding 1,4-dihydro-1,1-dimethyl-1-stannanaphthalenes 7 and 17, respectively, via an exchange reaction with AsCl 3 followed by dehydrohalogenation by DBU. Both 3 and 4 are in mobile equilibrium with their head-to-head Diels-Alder dimers. The reaction of 4 with Mo(CO) 3 (Py) 3 and BF 3 ‚OEt 2 affords Mo(CO) 3 complex 5. The crystal structure of 5 shows that the Mo(CO) 3 group is η 6 -bound to the C 5 As ring of the arsanaphthalene.

The reaction of 1-chloro-1-boracyclohexadiene (12) with N,N′-dimethyl-N, N′-bis(trimethylsilyl)ethylene-1,2-diamine followed by LDA afforded the dilithium salt of N,N′-bis(1boratabenzene)-N,N′-dimethylethylene-1,2-diamine ( 14). The reaction of 14 with ZrCl 4 afforded the boron-bridged dimethylethylenediamino bis(boratabenzene) zirconium dichloride complex 8, while reaction of 14 with FeCl 2 afforded the corresponding dimethylethylenediamino-bridged iron(II) complex 9. The structures of 8 and 9 were determined by X-ray diffraction. In each case the boratabenzene units are bridged by an approximately C 2 -symmetric dimethylethylenediamino bridge which makes 8 and 9 chiral. A barrier to interconversion of the enantiomeric conformers of 8 was determined by 2D 1 H NOESY as 21.2 ( 0.2 kcal/mol, while the corresponding barrier of 9 was determined from variabletemperature 13 C NMR spectroscopy to be 16.9 ( 0.5 kcal/mol. Both barriers involve rotation about the exocyclic B-N π-bonds. Comparison has been made with the corresponding bridged cyclopentadienyl complexes 10 and 11.