Symmetry Lab › D4h › Cyclobutadiene dianion (planar)
C₄H₄²⁻ Cyclobutadiene dianion (planar)
Planar 4-membered ring · point group D4h · order 16
- Point group
- D4h — A C4 principal axis, 4 perpendicular C2 axes and a horizontal mirror plane; these also give 4 vertical planes and a centre of inversion.
- Order
- 16
- Operations
- E, 2C₄, C₂, 2C₂′, 2C₂″, i, 2S₄, σh, 2σᵥ, 2σd
- Shape
- Planar 4-membered ring
- Atoms
- 8 (C × 4, H × 4)
Symmetry elements of C₄H₄²⁻
- C₄ — perpendicular to the ring
- C₂′ (1) — in the plane, through two opposite atoms
- C₂′ (2) — in the plane, through two opposite atoms
- C₂″ (1) — in the plane, through two opposite bond midpoints
- C₂″ (2) — in the plane, through two opposite bond midpoints
- i — centre of inversion
- σh — the plane of the ring
- σᵥ (1) — perpendicular to the plane, through two opposite atoms
- σᵥ (2) — perpendicular to the plane, through two opposite atoms
- σd (1) — perpendicular to the plane, through two opposite bond midpoints
- σd (2) — perpendicular to the plane, through two opposite bond midpoints
- S₄ — rotate 90°, then reflect in σh
Structure
- C–C 1.44 Å (all equal)
- Six π electrons: aromatic
- The neutral molecule is rectangular (D2h) and antiaromatic
Other D4h molecules
[Pt(NH₃)₄]²⁺ (N atoms shown)Tetraammineplatinum(II) ion[AuCl₄]⁻Tetrachloroaurate(III) ion[ICl₄]⁻Tetrachloroiodate(III) ion[PdCl₄]²⁻Tetrachloropalladate(II) ion[PtCl₄]²⁻Tetrachloroplatinate(II) ion[BrF₄]⁻Tetrafluorobromate(III) ionXeF₄Xenon tetrafluoridetrans-[CoCl₂(NH₃)₄]⁺trans-Tetraamminedichlorocobalt(III) (N atoms shown)[Ni(CN)₄]²⁻Tetracyanonickelate(II) ion[Pt(CN)₄]²⁻Tetracyanoplatinate(II) ion[Re₂Cl₈]²⁻Octachlorodirhenate(III) iontrans-[OsCl₂(CO)₄]trans-Dichlorotetracarbonylosmium(II)