SYNTHESIS, STRUCTURE, AND DYNAMIC BEHAVIOR OF U-ALDIMIDO)(MU-ETA(1)ETA(2)-ALKYNE)-BISZIRCONOCENE CATION COMPLEXES THAT CONTAIN PLANAR-TETRACOORDINATE CARBON
W. Ahlers et al., SYNTHESIS, STRUCTURE, AND DYNAMIC BEHAVIOR OF U-ALDIMIDO)(MU-ETA(1)ETA(2)-ALKYNE)-BISZIRCONOCENE CATION COMPLEXES THAT CONTAIN PLANAR-TETRACOORDINATE CARBON, Chemische Berichte, 130(8), 1997, pp. 1069-1077
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)).