The crystallographically determined structural features of Na(isodiCp)(15-crown-5) and [K-cryptand(2.2.2)]+(isodiCp)- are compared to those of the corresponding Li(TMEDA) complex and the sandwich dimer involving Li+ (cocrystallized with Li(12-crown-4)2). The features of the potassium salt are distinctively different from those of its congeners. As a consequence of the encapsulation of the K+ ion by the cryptand, no interaction occurs with the isodiCp anion, which is “naked”. Notwithstanding the complete dissociation that exists, the stand-alone isodiCp anion exhibits appreciable folding about the bond that it shares with the norbornyl framework. The dihedral angle is 8.3(1)° in a downward direction away from the exo surface. This unrivaled opportunity to observe the free isodicyclopentadienide anion is shown to be in agreement with the results of HF−SCF calculations.

Exo,exo derivatives of the efficient catalyst precursors (diisodicyclopentadienyl)titanium and -zirconium dichloride substituted at the central position have been synthesized. These compounds have been characterized by solution NMR measurements, which also permitted the calculation of rotational barriers. The solid-state structures of exo,exo-bis(3-diphenylphosphinoisodicyclopentadienyl)titanium and -zirconium dichloride were determined by X-ray crystallography. Unfortunately, after activation by methylalumoxane, these complexes are shown to serve as poor catalysts for the polymerization of propene.

The exo,exo-bis(isodicyclopentadienyl)magnesium sandwich and the monomeric exo-(isodicyclopentadienyl)butylmagnesium TMEDA complex have been synthesized and characterized by 1H and 13C NMR spectroscopy in C6D6 solution. The solid-state structures were determined by X-ray crystallography. The stereoselectivity with which both moisture-sensitive compounds react with TiCl3·3THF and ZrCl4 was assessed and suitably compared to related observations recorded for alkali metal (Li+, Na+, and K+) complexes of isodicyclopentadiene.