Hypercoordination

{
  "id": "MLC-T-CHM-005511",
  "term": "Hypercoordination",
  "field": "Chemistry",
  "definition": "A property of main-group atoms that reach a coordination number greater than four, the number allowed by the Lewis octet rule, as in PCl5, SF6 and the five-coordinate carbon of the methonium ion CH5+. It overlaps with hypervalency but also covers electron-deficient species with multicenter sigma bonding. Modern bonding analyses explain the extra bonds through multicenter interactions such as three-center four-electron bonds, not through d-orbital participation.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "Lewis octet rule",
    "cation",
    "coordination",
    "hydrogen bond",
    "hypervalency",
    "power"
  ],
  "references": [
    "PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1945 (https://doi.org/10.1351/pac199971101919)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/hypercoordination/"
}