No covalent bond formation due to repulsion

[Maria Malik]

Hi,
I want to ask , is there any example in chemistry when during covalent bond formation the repulsive forces dominate and no bond is formed.
Thanks

 

[TeethWhitener]

It's tough to know exactly what you mean. Plenty of diatomics have zero bond order (He₂, for example), but I'm not sure I'd call the cause of that a "repulsive force." In fact, the helium dimer is weakly bound by dispersion forces. The closest thing I can think to what you're asking is a case like He₂²⁺, which is isoelectronic with H₂, so it has a bond order of 1, but it is unstable because the two nuclei repel each other electrostatically.