Advanced Topic 712 of 1102 Inorganic Chemistry
Cluster Compounds
Compounds containing metal-metal bonded groups of atoms.
In-depth explanation of Cluster Compounds
Cluster compounds contain groups of metal atoms held together by direct metal-metal bonds, often with bridging or surrounding ligands. Their bonding can include multiple metal-metal bonds, including quadruple bonds. The classic example is the rhenium anion Re2Cl8 2-, which has a quadruple Re-Re bond made from sigma, two pi and one delta component. Octahedral clusters such as Mo6Cl8 4+ have a metal octahedron with bridging chlorides on the faces. Carbonyl clusters, such as Os3(CO)12, have metal triangles. Clusters link molecular and solid-state chemistry.
Going deeper: Cluster Compounds
Key ideas: Contain metal-metal bonded polyhedral cores: Re2Cl8 2- with a quadruple bond (sigma, two pi, one delta), Mo6Cl8 4+ octahedral cluster, Fe3(CO)12 and boranes with deltahedral shapes. Wade-Mingos rules: for closo clusters the number of skeletal electron pairs is n + 1, for nido n + 2, arachno n + 3 (n vertices). Metal clusters are common among 4d and 5d elements because of larger orbitals.
Common mistakes and connections: Students overlook that bond order can exceed three, as in Re2Cl8 2-, with eclipsed geometry required for the delta bond. Counting electrons for each vertex requires care: BH counts 2, C-H 3 skeletal electrons. Links to boranes, metal carbonyl clusters, bonding theory and catalysis on nanoclusters.
Visualization of Cluster Compounds
Metal cluster compounds contain bonded M-M polyhedra; a cube of atoms is the simple picture of a cluster with metal-metal bonds. The interactive lesson shows this as a live animation or chart.
Worked example and use case
The Re2Cl8 2- ion contains a quadruple bond, giving a Re-Re bond order of four.
Frequently asked questions about Cluster Compounds
What is Cluster Compounds?
Compounds containing metal-metal bonded groups of atoms.
Is Cluster Compounds a beginner, intermediate or advanced topic?
Cluster Compounds is a advanced topic in Inorganic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Cluster Compounds?
Study these earlier topics in Inorganic Chemistry first: Ceramics, Superconductors, Zintl Phases.
What comes after Cluster Compounds?
The next topics in Inorganic Chemistry are Solid State Inorganic Structures and Perovskites.
Can I practise Cluster Compounds with quizzes?
Yes. The interactive lesson includes a self-check question on Cluster Compounds, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Cluster Compounds fits in Inorganic Chemistry
Cluster Compounds is topic 97 of 113 in Inorganic Chemistry.