Sulfur difluoride, SF2 is an inorganic compound that consists of one sulfur and two fluorine atoms. It is basically generated from the chemical reaction between sulfur dichloride and potassium fluoride or mercury(II) fluoride at low pressures:
SCl2 + 2 KF → SF2 + 2 KCl
SCl2 + HgF2 → SF2 + HgCl2
Sulfur difluoride is a highly unstable compound because of the unsymmetrical isomer of S2F4 which is proposed to arise via insertion of SF2 into the S−F bond of a second molecule SF2 resulting in decomposing to FSSF3 (1,1,1,2-tetrafluorodisulfane).
It can also be formed from the reaction between oxygen difluoride and hydrogen sulfide:
OF2 + H2S → SF2 + H2O
Sulfur difluoride is not considered a toxic compound. So special handling is not needed while using it.
Uses of Sulfur difluoride
- It is used in the laboratory
- It is used as targets and substrates in the development of new synthetic methods.
- It is also used as electrophilic warheads by both medicinal chemists and chemical biologists.
| Name of molecules | Sulfur difluoride |
| IUPAC Name | sulfoxylic difluoride |
| Chemical Notation | SF2 |
| SF2 Valence electrons | 20 |
| Hybridization of SF2 | sp3 type |
| Molecular Geometry of SF2 | Bent |
| Electron geometry of SF2 | Tetrahedral |
| Bond Angle | 98 degrees |
| Dipole moment | 0.52D |
| SF2 Polar or Nonpolar? | Polar |
Now, the overview lewis dot structure of Sulfur difluoride, its molecular geometry, and hybridization are explained in this article.
SF2 Lewis Structure
Before illustrating the lewis structure of sulfur difluoride, we must have some basic ideas about valence electrons, the octet rule, and the formal charge for clear concepts.
What are Valence shell and Valence electrons?
The valency of an element is determined by the number of electrons present in the outermost shell of its atom. Hence, the outermost shell of an atom is called the valence shell and its corresponding electrons are called valence electrons.
Now looking at the periodic table, we know that the valence electron of sulfur is 6 and that of fluorine is 7.
Calculating the total sum of valence electrons,
The total sum of valence electrons of SF2= 6+7*2=20
Thus, the valence electron of SF2 is 20.
What is the Octet rule?
Atoms of other elements have a tendency to acquire an octet(i.e.,8 electrons) in their outermost shell to attain the configuration of nearest noble gas (i.e., stable electronic configuration). This is known as the octet rule. There are many exceptions to the octet rule. The octet rule fails in dealing with ionic compounds of the transition metals.
What is the Formal charge?
The formal charge of an atom is a parameter that indicates whether the atom in question is electrostatically balanced or unbalanced.
As we know,
The formal charge of any compound is calculated with the below formula
Formal Charge = Valence electrons – Unbonded electrons – Half of the bonded electrons
Steps for drawing Lewis dot structure of SF2
Step 1. Count the total number of valence electrons present on each atom of the SF2 molecule
From the periodic table, we know that the valance electron of sulfur is 6. Similarly, the valence electron of fluorine is 7.
The valence electrons of SF2 are the sum of the valence electrons of sulfur and fluorine. As SF2 contains 2 fluorine atoms. The valence electrons of SF2 are 20.
Step 2. Determine the total number of valence electrons pairs for SF2 molecules
The total valence electrons of the molecules are the sum of sigma bonds, pi bonds, and the lone pairs present at the valence shells i.e. Mathematically,
Total valence electrons= sigma bonds+pi bonds+lone pairs at valence shell
But simply, we can calculate it by diving the total valance electrons by 2 which will give valence electrons pairs.
For SF2, the total number of valence electrons pairs are found to be 20/2 i.e 10.
Step 3. Identify the Central atom and draw a simple skeleton diagram.
To be a central atom, the atom must have the ability to have greater valence. But mostly, it is important to consider both the number of atoms as well as the electronegativity of atoms to determine which one to take the central atom.
In the SF2 compound, sulfur is less electronegativity than fluorine. So, sulfur lies as a central atom while fluorine lies at terminal ends.
Step 4. Put lone pairs of electrons on each atom.
After identifying the central atom and drawing a skeleton diagram, It became easy to point out the lone pairs of electrons on each atom.
For SF2 compounds, Sulfur has four valence electrons that have not participated in any bond formation. So, the lone pairs for this compound are four.
In the lewis structure of SF2, we can notice single bonds between sulfur and fluorine that left out two lone pairs of electrons on the central sulfur atom.
Step 5. Complete the octet of all the atoms and make a covalent bond if necessary.
In the lewis structure, it is very necessary for atoms of the compound to fulfill their octet state to acquire a stable state. Fluorine needs one electron to complete its stable state so it will share that one electron with sulfur and acquire its stable state. In this way, fluorine atoms form a single bond with sulfur.
And sulfur has four electrons that don’t take part in any bond formation. So, it is considered as lone pairs or unbonded electrons.
Step 6. Calculate the formal charge distribution on all atoms and check the stability.
Now, the formal charge distribution on all-atom i.e sulfur and fluorine in sulfur difluoride molecules is calculated to check whether atoms are electrostatically balanced or unbalanced.
Now, as we already found out the valence electrons of SF2 are 20. The bonded atoms in SF2 are 4, one from each fluorine and two from sulfur. The unbounded electrons in SF2 are 18.
So, By using the given formula,
Formal charge= 20-18-2 (because half of the bonded electrons needed)
This means the formal charge of SF2 is found to be zero. This indicates that the atom of this compound is electrostatically balanced.
From this, we can predict that the atoms of sulfur difluoride are electrostatically balanced.
SF2 Molecular Geometry & Shape
As the Molecular Geometry and the shape of compounds are determined by Lewis structure by comparing the arrangements of given atoms and their electrons in the valence shells. The molecular geometry is basically calculated with VSEPR theory or from AXN notation.
As we already know, In VSEPR theory each atom in the compound is arranged such that the compound becomes stable in nature giving a compound a unique shape. Basically, lone pairs, bonding electrons determine the molecular geometry and the shape of the compound.
This table shows the molecular shape and their electron geometry based on the lone pairs and bond pairs of compounds.
For the SF2 compound, we know that the sulfur has two lone pairs and two bonded electrons with respective fluorine. So according to the above table, the molecular Geometry of SF2 is found to be type AX2E2 which means the compound is either bent or nonlinear.
Also Read:
- SF4 Lewis structure, Molecular geometry, Bond angle, Hybridization
- O3 Molecular geometry and Hybridization (with Lewis structure)
Bond Angle of SF2
Since the molecular geometry of SF2 is bent that means it has a bond angle. The bond angle of SF2 is expected somewhere around 98 degrees.
SF2 Hybridization
To find out the SF2 hybridization, the above diagram clarifies the concept more. The SF2 hybridization is sp3 hybridization.
The electronic configuration of Sulfur is 1s2 2s2 2p6 3s2 3p4. First, the electrons are filled in 1s, then in 2s, and so on.
Similarly, the electronic configuration of Fluorine is 1s2 2s2 2p5. And, when we combine the electronic configuration of SF2 then it comes to 3s2 3Px2 3Py1 3Pz1. By that, we can deduce the hybridization of the compound, which comes as sp3.
Or simply, we can predict the hybridization of any compound from the given steps:
1. If the total number of valence electrons is less or equal to 8, divided by 2.
(V.E. < 8 divided by 2)
2. If the total number of valence electrons of a molecule is between 8 to 56, divided it by 8.
(8 < V.E < 56 divided by 8)
3. Similarly, if the valence electrons of a given molecule are more than 56, divided by 18.
| Orbitals Number | Hybridization type |
| 2 | sp |
| 3 | sp2 |
| 4 | sp3 |
| 5 | sp3d |
| 6 | sp3d2 |
| 7 | sp3d3 |
In our case, SF2 has 20 electrons so it is divided by 8 which gives 2 quotients, remaining 8 which is again divided by 2 gives 4 quotients. That means we get 4 orbitals in total which is sp3 hybridization.
MO Diagram of SF2 Molecule
Is SF2 Polar or Nonpolar?
The polarity of the molecule results from the non-symmetrical sharing of the valence electron, creating a region of unequal charges in the molecule.
As the sulfur has an electronegativity of 2.58 while that of fluorine is 3.98. Their difference in electronegativity results in the dipoles of the S-F bond not canceling out each other. And the compound also has a bent molecular geometry shape. Thus, we can conclude that SF2 is not rendered symmetrical and the molecule gets polarity on it.
Hence, SF2 is a polar molecule and also contributes some dipole moments.
Electronegativity of SF2
As we know, Electronegativity explains the degree to which an atom attracts electrons in a chemical bond. The difference in electronegativity of two atoms determines the chemical bond.
- If the electronegativity difference is greater than 1.7, the bond will have an ionic character.
- If the electronegativity difference is between 0.4 and 1.7, the bond will have a polar covalent character.
- If the electronegativity difference is less than 0.4, the bond will have a nonpolar covalent character.
As we early explain the electronegativity value of sulfur(2.58) and fluorine(3.98), their difference is 1.4 which means the bond will have a polar covalent character.
Summary
- Sulfur difluoride is a highly unstable compound because of the unsymmetrical isomer of S2F4
- The valence electrons of SF2 are 20 and sulfur is less electronegativity than fluorine. So, sulfur lies as a central atom while fluorine lies at terminal ends.
- The bond angle of SF2 is expected somewhere around 98 degrees.
- SF2 is a polar molecule and also contributes to some dipole moments.
- The SF2 hybridization is sp3 hybridization.
