Circulardichroism—LXXV : Cottonogenic derivatives of chiral bidentate ligands with the complex [Mo 2 (O 2CCH 3) 4

Abstract

[Mo 2(O 2CCH 3) 4] forms optically active complexes in DMSO after addition ofchiral ligands. Bidentate ligands (carboxylic acids, diols, and amino alcohols) but also a primary amine (α-phenylethylamine) were shown to form these complexes. For molar ratios of less than appr. 1.5:1 (ligand to complex) up to 5 Cotton effects (A to E from 600 to 270 nm) can be observed. The signs of those between 300 and 400 nm can be used for empirical determination of absolute configuration of complexing ligands. Bands A-D are assigned to the following transitions: A: mainly π Mo-Mo→ δ * (A 1g→ E g); B: δ →ρ * Mo-O (A 1g → A 2g C: mainly δ → π * Mo-Mo (A 1g → E g ) D: δ → δ * (A 1g → A 2u ). Sector rules for the pair of CD-bands A/C (hexadecant rule) and for CD-band B (hexadecant rule with two additional nodal planes through the MoO 4- planes) are derived from qualitative MO theory.