NOE-derived solution structures of a benzylborato-azasilazirconacyclobutane complex, {(Me3Si)2N}Zr(CH2SiMe2NSiMe3){η6-PhCH2B(C6F5)3}

The benzylborato-azasilazirconacyclobutane complex 1 was formed by ligand cyclometalation upon reaction of {(Me3Si)(2)N}(2)Zr(CH2Ph)(2) with B(C6F5)(3). Quantitative analysis of the H-1 NOESY time course of 1 using the conformer population analysis method demonstrates that the dominant conformers in solution are rapidly exchanging benzyl berate rotamers, closely bound to the asymmetric zirconium. The ring rotates such that the benzylic methylene eclipses the metallocyclobutylmethylene in the majority of the population and the free amide nitrogen in the minority of the population. A molecular dynamics approach was required to solve this solution structure because a mixture of static conformations does not satisfactorily explain the observed spectra.