No abstract

A simple and efficient synthesis and crystallographic analysis of the partially fluorinated 7:8,9:10-dibenzo-1,2,3,4-tetrafluorotriphenylene, 1, in 59% yield is reported. Compound 1 is a blue luminescent [5]helicene in both solution and the solid state. It spontaneously forms enantiomorphous single crystals from racemic samples and exhibits slipped, face-to-face F...C(pi) contacts within the stacks of molecules.

2,2'-Distannyl derivatives of dodecafluorobinaphthalene are converted to a novel D2 symmetric borane dimer, which can be oxidized to (+)-F12BINOL; resolution using (S)-acetoxypropanoyl chloride affords enantiopure material.

3 ) 2 ) in moderate yield. Direct protonolysis of Zr(CH 2 Ph) n Cl 4-n (n ) 2-4) or Zr[N(SiMe 3 ) 2 ] n Cl 4-n (n ) 2, 3) with 1 or 2 (1 equiv) affords the zirconium complexes Zr(Ar). The structures of 1, 4, 5, and 7 were established by X-ray crystallography with the zirconium complexes 4, 5, and 7 all adopting a monocapped trigonal bipyramidal geometry in the solid state. However, in solution, these complexes display higher symmetry due to rapid ligand rearrangement. The silylamido complex 4 shows restricted rotation of the C 6 F 5 rings in solution (∆G q ) 49 ( 3 kJ mol -1 ). Abstraction of a benzyl group from 6 by B(C 6 F 5 ) 3 affords {Zr[CH 2 OCH 2 CH 2 N(C 6 F 5 )] 2 (CH 2 Ph)} + {(PhCH 2 )B(C 6 F 5 ) 3 } -(9). This complex shows evidence for η 2 -benzyl coordination and does not polymerize ethylene at room temperature. Treatment of 3 with excess MAO (500 equiv) and ethylene (1 atm, 50 °C) affords polyethylene at a modest rate (3.2 kg mol -1 Zr h -1 ).

[reaction: see text] PhB(C(6)F(5))(2) exhibits much higher activity as a Lewis acid catalyst for the allylstannation of aromatic aldehydes than the stronger Lewis acid B(C(6)F(5))(3). This anomalous enhancement of catalytic activity for the weaker LA is shown to be partly due to decreased thermodynamic stability of ion pair 2b relative to 2a in the product-forming step of the reaction. A mechanistic path where the borane serves as the true LA catalyst is more important for the weakly Lewis acidic borane.