Is there a commercial liquid with refractive index greater than n=2?
Definition of refractive index:

$n=\frac {c}{v}$

If n>2 then this means that the velocity of light in the material is less than half than in vacuum so there must be a strong interaction with the material.

 One of the highest refractory index in liquids is 1.79(20°C) possessed by a solution of sulfur in methylene iodide($CH_2I_2$). Liquids are less dense than solids and this explains why it's difficult to have a refractory index greater than 2.
I found a nature article that says:


  Selenium monobromide, Se2Br2, has a higher
  refractive index than that of any pure liquid hitherto
  recorded. Prepared by direct combination, the value
  for $\nu$ is 1.96±0.01 rising to 2.02 on exposure to the
  atmosphere, owing to decomposition of the bromide,
  with separation and reabsorption of selenium. 


https://www.nature.com/articles/133066b0

EDIT: From a more recent paper(2016), selenium monobromide is confirmed as one of the liquid with the highest refraction index(>2). However, diiodomethane is more easily accessible commercially.  


  A promising candidate solvent is the organic liquid diiodomethane (CH2I2), which is one of the liquids with the highest
  known refractive index values (n = 1.74). While other high
  refractive index liquids exist (phenyldi-iodoarsine (C6H5AsI2)
  with n = 1.85 and selenium monobromide (Se2Br2) with n=
  2.1), diiodomethane has the key advantage of being commercially available. In addition, diiodomethane is an excellent
  solvent, and many liquid formulations using salts dissolved in
  diiodomethane are reported to increase the refractive index
  and are even available commercially.


https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-12-3165