Cyclopentadienyl-bis(oxazoline) Magnesium and Zirconium Complexes in Aminoalkene Hydroaminations

A new class of cyclopentadiene-bis­(oxazoline) compounds and their piano-stool-type organometallic complexes have been prepared as catalysts for hydroamination of aminoalkenes. The two compounds MeC­(OxMe2)2C5H5 (BoMCpH; OxMe2 = 4,4-dimethyl-2-oxazoline) and MeC­(OxMe2)2C5Me4H (BoMCptetH) are synthesized from C5R4HI (R = H, Me) and MeC­(OxMe2)2Li. These cyclopentadiene-bis­(oxazolines) are converted into ligands that support a variety of metal centers in piano-stool-type geometries, and here we report the preparation of Mg, Tl, Ti, and Zr compounds. BoMCpH and BoMCptetH react with MgMe2(O2C4H8)2 to give the magnesium methyl complexes {BoMCp}­MgMe and {BoMCptet}­MgMe. BoMCpH and BoMCptetH are converted to BoMCpTl and BoMCptetTl by reaction with TlOEt. The thallium derivatives react with TiCl3(THF)3 to provide [{BoMCp}­TiCl­(μ-Cl)]2 and [{BoMCptet}­TiCl­(μ-Cl)]2, the former of which is crystallographically characterized as a dimeric species. BoMCpH and Zr­(NMe2)4 react to eliminate dimethylamine and afford {BoMCp}­Zr­(NMe2)3, which is crystallographically characterized as a monomeric four-legged piano-stool compound. {BoMCp}­Zr­(NMe2)3, {BoMCp}­MgMe, and {BoMCptet}­MgMe are efficient catalysts for the hydroamination/cyclization of aminoalkenes under mild conditions.