The key difference between dπ-dπ bond and delta bond is that dπ-dπ bond forms between a filled d atomic orbital and an empty d atomic orbital whereas delta bond forms between four lobes of one involved atomic orbital and four lobes of another involved atomic orbital.
Both dπ-dπ bond and delta bond form via the overlapping of atomic orbitals. The overlapping of orbitals in dπ-dπ bond formation creates a coordinate bond while the overlapping in delta bond formation forms a covalent chemical bond.
CONTENTS
1. Overview and Key Difference
2. What is dπ-dπ Bond
3. What is Delta Bond
4. Side by Side Comparison – dπ-dπ Bond vs Delta Bond in Tabular Form
5. Summary
What is dπ-dπ Bond?
A dπ-dπ bond is a type of covalent chemical bond where a metal binds with a ligand through the overlapping of their d orbitals. In other words, this type of covalent chemical bonds forms when the filled d orbital of the transition metal donates some of its electrons to the empty d orbitals of a ligand to form coordination chemical bonds. Therefore, these chemical compounds are named as coordination complexes.
Figure 01: A Coordinate Covalent Compound
Unlike delta bonds, which resemble the structure of a dπ-dπ bond, dπ-dπ bond occurs between a filled d orbital and an empty d orbital. Also, a delta bond can occur between any two atoms having involved atomic orbitals while a dπ-dπ bond occurs between a transition metal having completed d electron configuration and a ligand having empty orbitals in d electron shell.
What is a Delta Bond?
Delta bond is a type of chemical bond where four lobes of one involved atomic orbital tend to overlap with four lobes of another involved atomic orbital to form this bond. This type of orbital overlap leads to the formation of a molecular orbital (bonding) which is consisting of two nodal planes containing the internuclear axis, and that goes through both atoms. The Greek letter for delta sign “” is used for the notation of a delta bond.
Figure 02: Formation of a Delta Chemical Bond
Generally, the orbital symmetry of the delta bond is similar to the usual type of d atomic orbital when considering the bond axis. We can observe this type of chemical bonding in atoms having occupied d atomic orbitals which contains low energy to participate in covalent chemical bonding. For example, transition metals that are in organometallic chemical species show delta bonding; chemical compounds of some metals such as rhenium, molybdenum, and chromium contain quadruple bonds. A quadruple bond consists of a sigma bond, two pi bonds, and a delta bond.
When considering the orbital symmetry of a delta bond, we can observe that the symmetry is different from that of a pi antibonding orbital. A pi antibonding orbital contains one nodal plane consisting of the internuclear axis and another nodal plane that is perpendicular to the axis between atoms.
The scientist Robert Mulliken introduced the delta notation in 1931. He identified this bond first using the chemical compound potassium octachlorodirhenate(III).
What is the Difference Between dπ-dπ Bond and Delta Bond?
dπ-dπ bond and delta bond are two types of covalent chemical bonds. The key difference between dπ-dπ bond and delta bond is that dπ-dπ bond forms between a filled d atomic orbital and an empty d atomic orbital whereas delta bond forms between four lobes of one involved atomic orbital and four lobes of another involved atomic orbital.
Before infographic summarizes the differences between dπ-dπ bond and delta bond in tabular form.
Summary – dπ-dπ Bond vs Delta Bond
dπ-dπ bond and the delta bond are two types of covalent chemical bonds. The key difference between dπ-dπ bond and delta bond is that dπ-dπ bond forms between a filled d atomic orbital and an empty d atomic orbital whereas delta bond forms between four lobes of one involved atomic orbital and four lobes of another involved atomic orbital.
Image Courtesy:
1. “CoA6Cl3” – Smokefoot assumed – No machine-readable source provided. Own work assumed (based on copyright claims). (Public Domain) via Commons Wikimedia
2. “Delta-bond-formation-2D” By Ben Mills – Own work (Public Domain) via Commons Wikimedia