Relationship between structure and reactivity for metal clusters formed in ion-molecule reactions in decacarbonyldimanganese and pentacarbonyl(pentacarbonylmanganio)rhenium

Abstract

Relative rate constants for ion-molecule reactions in Mn/sub 2/(CO)/sub 10/ and ReMn(CO)/sub 10/ are reported. Electron-impact-produced fragment ions react with the parent to form cluster ions containing three and four metal atoms. Subsequent sequential reactions lead to cluster ions containing as many as eight metal atoms. Most of the clusters formed in ReMn(CO)/sub 10/ contain equal numbers of Re and Mn atoms. A rough correlation is found between the average electron deficiency per metal atom and the rate constant. Electron deficiencies are assigned with use of the effective atomic number rule and on the assumption of closed-polyhedral structures for most of the ions. The rate constants tend to increase with electron deficiency until the deficiency reaches two per metal atom. Exceptions to this behavior are rationalized in terms of ligand crowding and electronic effects such as multiple bonding and ligand-induced restructuring analogous to that observed in coordinatively unsaturated metal surfaces. Several cases are identified where substituting Mn for Re in a metal cluster changes its behavior substantially. 22 references, 5 figures, 7 tables.