CHIROPTIC EFFECTS OF CHIRAL LANTHANOID OR GANYLS .2. BIS(CYCLOPENTADIENYL)YTTERBIUM(III) ALKOXIDES EACH WITH AN ASYMMETRIC LIGAND ATOM - MOLECULAR-STRUCTURE AND CHIROPTIC EFFECTS

Reaction of (C5H5)3Yb with (R)-(+)-, (s)-(-)-isobutyllactate or (S)-()-2-butanol in a molar ratio of 1:1 affords the new bis(cyclopentadien yl)ytterbium(III)alkoxides 4a, 4b and 5, respectively, which could be characterized by H-1-NMR spectroscopy. The single-crystal X-ray analys is of 4a reveals a particulary rigid dinuclear framework, [(eta5-C5H5) 2Yb(mu-OCH(Me)COO(i)Bu}]2. 4a: Monoclinic P, P2(1); a 1067.3(1), b 100 2.6(1), c 1622.9 (2) pm; beta 96.84(1)-degrees; R = 0.038 (R(w) = 0.04 0). While 4a and 4b display notable f-f-circular dichroism (f-f-CD), t he f-f-absorption range of the likewise chiral complex 5 with a less r igid configuration is devoid of any CD effects.