SYNTHESIS, STRUCTURE, AND DYNAMIC BEHAVIOR OF U-ALDIMIDO)(MU-ETA(1)ETA(2)-ALKYNE)-BISZIRCONOCENE CATION COMPLEXES THAT CONTAIN PLANAR-TETRACOORDINATE CARBON

The benzonitrile hydrozirconation product Cp2ZrCl(N=CHPh) 8 was treate d with propynyl Lithium to yield the (propynyl) (benzaldimido)ZrCp2+ c omplex 9. Subsequent treatment with trityl tetraphenylborate generated [Cp2Zr(C=C-CH3)+BPh4-] that instantaneously added to 9 to eventually form the (mu-aldimido)(mu-eta(1):eta(2)-hexadiyne)ZrCp2 cation 11. The X-ray crystal structure analysis showed that 11 contains a planar-tet racoordinate carbon atom that is stabilized by forming a three-center- two-electron bond with the two adjacent metal atoms. Similarly, comple x 9 reacted with [Cp2Zr(CH3)+CH3B(C6F5)(3)(-)] to yield the planar-tet racoordinate carbon containing (mu-aldimido)(mu-eta(1):eta(2)-2-butyne )Zr Cp-2(+) cation 12. Both complexes 11 and 12 exhibit dynamic NMR sp ectra due to their rapid reorganization of the dimetallabicyclic frame works (Delta G double dagger approximate to 10 kcal mol(-1)) in additi on to an anchimerically assisted C=N bond rotation (Delta G double dag ger approximate to 15 kcal mol(-1)).