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(Ox)2C5H5 (BoCpH; Ox = 4,4-dimethyl-2-oxazoline) and MeC(Ox)2C5Me4H (Bo CpH) are synthesized from C5R4HI (R = H, Me) and MeC(Ox)2Li. These cyclopentadienebis(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. BoCpH and BoCpH react with MgMe2(O2C4H8)2 to give the magnesium methyl complexes {BoCp}MgMe and {BoCp}MgMe. BoCpH and BoCpH are converted to BoCpTl and BoCpTl by reaction with TlOEt. The thallium derivatives react with TiCl3(THF)3 to provide [{Bo Cp}TiCl(μ-Cl)]2 and [{Bo Cp}TiCl(μ-Cl)]2, the former of which is crystallographically characterized as a dimeric species. BoCpH and Zr(NMe2)4 react to eliminate dimethylamine and afford {Bo Cp}Zr(NMe2)3, which is crystallographically characterized as a monomeric four-legged piano-stool compound. {BoCp}Zr(NMe2)3, {BoCp}MgMe, and {BoCp}MgMe are efficient catalysts for the hydroamination/cyclization of aminoalkenes under mild conditions.