Chiral molecules containing metal-metal bonds

Many chiral compounds having metal-metal bonds are now known in which the M-M unit is the chromophore. In this review they are classified as those where it is either (1) an inherently chiral chromophore owing to helical stacking of metal-ligand bonds, or (2) not inherently chiral but surrounded by a collection of ligands bearing chiral substituents. In only a few cases have the actual CD and/or ORD spectra been measured and analyzed. These include M2X4-(PP)(2) molecules (PP = a bridging diphosphane) and M-2(O-2-CR)(4) molcules where R is chiral. The more recently discovered helical extended metal atom chain (EMAC) molecules are also mentioned. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).