Square planar molecular geometry

A molecular geometry in which a central atom is bonded to four surrounding atoms arranged in one plane at the corners of a square.

Valence shell electron pair repulsion theory: A model that predicts molecular shapes from repulsions between regions of valence-shell electron density. Its electron-pair repulsions help explain the preferred arrangement of ligands around a central atom.
Xenon tetrafluoride: A noble-gas compound with four fluorine atoms bonded to xenon in a square-planar arrangement. It is a familiar nonmetal example with two lone pairs completing an octahedral electron-domain arrangement.
Tetrahedral molecular geometry: A molecular shape with four surrounding atoms directed toward the corners of a tetrahedron. It is the principal alternative for four-coordinate centers, with bonds extending out of one plane.
Coordination number: The number of atoms directly bonded to a central atom in a coordination entity. Square-planar centers have four directly bonded surrounding atoms.
Crystal field theory: A model that describes how surrounding charges split the energies of a metal ion’s d orbitals. Its orbital splitting helps account for square-planar stability in some transition-metal complexes.
Platinum(II) complexes: Coordination compounds in which platinum has oxidation state +2, commonly with four ligands in a square plane. Many platinum(II) compounds provide the characteristic transition-metal example of this geometry.
Seesaw molecular geometry: A molecular shape with four bonded atoms and one lone pair around a central atom in a trigonal-bipyramidal electron arrangement. Its nonplanar ligand arrangement distinguishes it from the four-ligand square plane.
Bond angle: The angle between two bonds that share an atom. Adjacent square-planar bonds form angles of about 90 degrees; opposite bonds form angles of 180 degrees.
Ligand field theory: A theory of coordination complexes that treats metal–ligand bonding through molecular orbitals. It refines the orbital explanation of why certain metal complexes favor this geometry.
cisplatin: A square-planar platinum(II) anticancer drug with two chloride and two ammonia ligands. Its geometry fixes the relative positions of the ligands involved in DNA binding.

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