Tetrakisdimethylamidozirconium and its dimethylamido lithium adduct: Structures of [zr(nme2)4]2 and zr(nme2)6li2(thf)2

The molecular structure of [Zr(NMe2)4]2 has been determined by an x-ray study and shown to involve a central Zr2N8 moiety involving the fusing of two trigonal bipyramidal units along a common axial-equatorial edge. The terminal ZrNMe2 units have trigonal planar coordination about the nitrogen atoms: ZrN = 2.050(5) and 2.104(5) Å, and ZrN (bridge) = 2.224(3) and 2.453(4) Å for equatorial and axial bonds, respectively. The ZrZr distance is 3.704(1) Å as expected for a non-MM bonding bridged compound. In tetrahydrofuran solution, Zr(NMe2)4 and LiNMe2 react irreversibly giving Zr(NMe2)6 Li2(THF)2 which has been isolated and characterized by an X-ray study. The central ZrN6 octahedral moiety is capped on two opposite faces by Li atoms which are also coordinated to an oxygen atom of a THF molecule. Pertinent distances are: ZrN = 2.22(7) (av.), NLi = 2.155(25) (av.) and LiO = 1.915(10) Å.