BONDING IN CRYSTALS CONTAINING ONE-DIMENSIONAL BRIDGED AND UNBRIDGED GROUP 11 AND 12 LINEAR, ZIGZAG, AND HELICAL CHAINS

Metal-metal (Cu–Cu, Ag–Ag, Au–Au, Cd–Cd, and Hg–Hg) distances in d10 metal chains (formally d10) exhibit a large variety, the closest contacts being even shorter than in the elemental metals. Extended Hückel calculations (EHT) have been performed on a number of crystals containing one-dimensional chains of group 11 and 12 transition-metal atoms and related silver-rich compounds. We find that from the point of view of metal–metal bonding, the compounds fall into two main categories. In the first group, in which an anion of a main-group atom is the bridging ligand, there is slight or no M–M bonding due to the effect of the ligand, which reduces the metal–metal bonding between naked d10 centers. The short M–M bond distances for some of these chains come from metal–metal coupling through ligands. A typical example of such a compound is Na2CuP. In the second group of compounds in which bridging ligands are absent, such as [Ag(CCR)2(PPh3)]x, there is some M–M bonding producing the short M–M bond distances. The analysis of orbital interactions shows that if the bridging ligand is a typical two-electron a donor, such as CH3−, some metal–metal bonding is induced by the ligand. An EHT calculation on Ag2O indicates that the color and conductivity for a number of silver-rich compounds result from excitation from oxygen 2p and metal 4d orbitals to metal 5s and 5p orbitals. MNDO calculations show that the helical conformation of mercuric sulfide and oxide can be attributed to the flatness of the torsional potential curves over a broad range of twist angles. © 1990, American Chemical Society. All rights reserved.