Chiral Ground State Research Articles

Self-induced effective gauge fields in the copper-oxygen plane of high-Tc perovskites: A lattice and a continuum formulation.

We present an exact formulation of the self-induced effective gauge fields both in the Hubbard model and in the true continuum description of the Cu-O planes of the high-${\mathit{T}}_{\mathit{c}}$ perovskites. We bypass the solution of the ground state in favor of the chirality order parameter as the intrinsic variable. The constraint of gauge symmetry greatly narrows the admissible forms for the gauge fields. We find that these fields can produce broken-symmetry chiral ground states on a lattice, but the intrinsic frustration in the continuum form of the gauge field seems to rule out such a state in the real Cu-O plane.

Thermally induced reaction of the ylide CH 3CHPPh 3 with diarylzirconocene complexes; the formation of unusual metallacyclic phospha-allyl type products

Diphenylmetallocene complexs (RCp) 2ZrPh 2 ( 4a, 4b: RH, CH 3) react with the phosphorous ylide Ph 3PCHCH 3 (5) at 80°C to yield six-membered metallocyclic ylides (RCp) 2 ZrCH 2CHP(Ph) 2(C 6 H 4) (8a,8b) plus two equivalents of benzene. The reaction presumably proceeds through a thermally generated (η 2-benzyne) zirconocene intermediate which takes up 5 to form a metallocene ylide (RCp) 2Zr(Ph)C(CH 3)PPh 3 ( 6). β-Hydride elimination and readdition followed by ortho-metallation then leads to the six-membered metallacycle. Complexes 8 have a stable chiral ground state geometry as judged by NMR spectroscopy. The presence of a distorted Cp 2Zr (phospha-allyl) moiety is suggested to explain theobserved characteristic spectroscopic features of the metallacyclic ylides 8.