Vyacheslav was the fifth son of Grand Prince Vladimir II
Monomakh of Kievan Russia
. He led armies for his father and brother.
Vyacheslav came to the Grand Prince's throne on the death of his brother Yaropolk II in 1139, apparently brought there by his nephew, who would later reign himself as Izyaslav II. His reign is given differently by different historians -- all agree that it started in 1139 and ended when he died, probably in 1154, but some list him as always on the throne during that period, and some as having been ousted for some periods. The difficulty is that the Prince of the city of Kiev was considered to be the Grand Prince, the ruler of Russia at the time, but by the 12th century the power of Kiev was declining and the princes of other cities may have held more actual power. This period has the descendants of Vladimir II (the Monomashchi) fighting other branches of the royal family.
Vyacheslav's cousin Vsevolod II, prince of Cherngiv, sent Vyacheslav back to the city of Turov where he had been prince and essentially ruled until his death in 1146, at which point another cousin, Igor II, became Grand Prince for a few months, was deposed, and then died. At this point Izyaslav II (son of Mstislav I) became Grand Prince, putting the Monomashchi back in control, but not Vyacheslav. Izyaslav ruled for a few years, but then Vyacheslav's brother Yuri I also set himself up as Grand Prince by sacking Kiev and ruling from the city of Suzdal.
Vyacheslav ruled jointly with his nephew Rostislav (son of Mstislav I) for the last years of his reign and died about 1154. As you can imagine from all this fighting, Vyacheslav did not get a chance to accomplish much that is remembered (except perhaps staying alive through all these other rulers' reigns).