After Napoleonic wars Russia was considered the strongest European power and the one which contributted most to allied victory. Both Austria and Prussia were afraid of Russia and its potential.
But Tsar Alexander was under influence of Polish noble Adam Jerzy Czartoryski who was convincing him to change Grand Duchy of Warsaw into Polish kingdom under his reign.
https://en.wikipedia.org/wiki/Adam_Jerzy_Czartoryski
Such solution was very dangerous for both Austria and Prussia because Russian tsar as king of Poland could have in the future claim and demand Polish territories which were occupied by Prussia and Austria during partitions of Poland, becoming its most industrialised part.
Nevertheless Alexander bribed Prussia with part of Polish territory and Austria alone wasnt able to stop Russia from creating Polish so called "Congress Kingdom" which became the liberal experiment of tsar Alexander.
The kingdom recived the most liberal constitution in Europe, had autonomy, separate parliament, treasure, army, administration and educational system and was bound with the Russian Empire by the personal union because according to constitution every tsar of Russia was supposed to be the king of Poland, after separate coronation in Warsaw. The power of tsar was limited by constitution which was written by Alexander and Czartoryski who stayed behind this idea.
It was as I said before in conflict with the Austrian interests because this solution would allow Poles in Austrian monarchy rebel and demand to join to the Polish kingdom or even to get Russian support. The small kingdom had strong army with officer corps coming from Napoleonic army and was economicaly quite strong because its economy was producing about 25% of all GDP of Russian empire.
Edited by Mosquito - 04-Dec-2015 at 19:15