Sp and d orbitals
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Understanding sp and d Orbitals in Chemistry
Introduction to Orbital Hybridization
Orbital hybridization is a fundamental concept in chemistry that explains the mixing of atomic orbitals to form new hybrid orbitals. These hybrid orbitals are crucial in determining the geometry and bonding properties of molecules. The most common types of hybridization involve s and p orbitals, but d orbitals also play a significant role, especially in transition metals and certain main group elements.
d-sp Orbital Hybridization in Transition Metal Catalysts
Recent research has highlighted the importance of d-sp orbital hybridization in enhancing the catalytic properties of transition metals. Unlike the conventional d-d hybridization, d-sp hybridization involves the interaction between d orbitals of transition metals and s or p orbitals of p-block elements. This interaction can significantly alter the electronic properties and catalytic activities of the metals, making them more effective for various reactions, particularly in energy-related electrocatalytic applications1. Theoretical and experimental studies have shown that p-block element-doped metal catalysts, intermetallic catalysts, and supported metal catalysts benefit greatly from d-sp hybridization, which tunes their catalytic performances1.
Maximum Overlap Hybrid Orbitals
The concept of maximum overlap hybrid orbitals provides insight into the distribution of s and d character in various hybridization schemes. For instance, in square planar and tetrahedral molecules, the overlap integrals for different ligand orbitals (s, p, sp, sp2, and sp3) have been calculated, showing that the contribution of d orbitals in these hybrids is generally smaller compared to those based on Pauling's criterion of hybrid strengths2. This understanding helps in predicting the bonding and structural properties of complex molecules.
d Orbitals in Excited States and Hypervalent Compounds
The role of d orbitals extends beyond ground-state configurations. In excited states, such as the sp3d2 configuration of sulfur, d orbitals exhibit significant changes in their mean radii, affecting the overall electronic structure and stability of the molecule3. Similarly, in hypervalent compounds like sulfur hexafluoride (SF6), d orbitals contribute to the binding energy and molecular stability by allowing strong back transfer from negatively charged ligands to the central atom5. This back transfer results in shorter bond lengths and increased stability, challenging traditional models that require sp3d2 hybridization5.
Structural Correlations and Coordination Polyhedra
The topology of coordination polyhedra formed by s, p, d, and f orbitals can be understood by adding or subtracting orbitals from spherical sp3 and sp3d5 manifolds. For example, five-coordinate trigonal bipyramids and square pyramids arise from adding specific d orbitals to an sp3 manifold, while six-coordinate polyhedra like octahedrons are formed by adding pairs of d orbitals4. This approach helps in predicting the geometry and flexibility of coordination complexes, which is crucial for understanding their reactivity and stability.
d Orbitals in Phosphorus Compounds
In phosphorus compounds, d orbitals play a significant role in various hybridization schemes such as sp3d, sp2d2, and p3d2. The wavefunctions and energy matrices for these configurations reveal that d orbitals in phosphorus are more diffuse in the sp3d configuration compared to the more compact forms in sp2d2 and p3d2 configurations7. This information is essential for understanding the electronic structure and reactivity of phosphorus-containing compounds.
Conclusion
The study of sp and d orbitals, particularly their hybridization, is crucial for understanding the electronic structure and reactivity of various molecules. From enhancing catalytic properties in transition metals to explaining the stability of hypervalent compounds, the role of d orbitals is diverse and significant. Advances in theoretical and experimental methods continue to shed light on these complex interactions, paving the way for the rational design of new materials and catalysts.
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Most relevant research papers on this topic
d-sp orbital hybridization: a strategy for activity improvement of transition metal catalysts.
D-sp orbital hybridization can enhance the activity of transition metal catalysts for energy-related electrocatalytic applications.
Quadricovalent Maximum Overlap Hybrid Orbitals
Maximum overlap hybrid orbitals for tetragonal plane and tetrahedral molecules show a smaller contribution of d orbitals in hybridization compared to those based on Pauling's criterion of hybrid strengths.
d Orbitals in the Excited Sulfur Atom
The d orbitals in the sp3d2 configuration have mean radii upwards from 1.85 A (7F) to 2.65 A (1S), with a single-configuration valence state having a mean radius of 2.39 A and a multiconfiguration valence state having a mean radius
On the role of d orbitals in sulfur hexafluoride
Sulfur d orbitals contribute strongly to the binding energy of SF/sub 6/, allowing strong back transfer from fluorine ligands to positively charged sulfur, increasing molecular stability.
Highly CitedStructural Correlations in Small Molecules: A Simple Molecular Orbital Treatment of sp Mixing
The angular-overlap model accurately explains bond shortenings and elongations in small molecules due to sp mixing, highlighting differences between transition-metal and main-group systems.
d Orbitals in the sp3d, sp2d2, and p3d2 Configurations of Phosphorus
Phosphorus's d orbitals in the sp3d configuration are diffuse and large, while those in sp2d2 and p3d2 configurations are compact and smaller.
First-principles theory of intrinsic spin and orbital Hall and Nernst effects in metallic monoatomic crystals
The orbital Nernst effect (ONE) is significantly larger than the spin Nernst effect (SNE) and has maximum values for group 10 elements (Ni, Pd, and Pt).
The chemistry of silicon involving probable use of d-type orbitals
Silicon may utilize its 3d-orbitals in compounds with greater than four ligancy, tetravalent bonding, and unusual chemical reactivities compared to analogous carbon compounds.
Toward surface orbitronics: giant orbital magnetism from the orbital Rashba effect at the surface of sp-metals
The orbital Rashba effect at the surface of sp-metals leads to electric polarization of surface states, making it a key platform for surface orbitronics.
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