Reaction of [Tc-99(CO)(6)]ClO4 with alkali in aqueous solutions yields yellow (Tc3H)-Tc-99(CO)(14) as the major product. On the other hand, [(TcH)-Tc-99(CO)(5)] becomes the major product when the reaction with alkali is combined with the extraction into hexane. The molecular structure of (Tc3H)-Tc-99(CO)(14), determined by SCXRD, is composed of the Tc-99(2)(CO)(9) fragment bound to the Tc-99(CO)(5) fragment via the hydrogen bridge and weak metal-metal bond. This compound crystallizes in the monoclinic system, space group P2(1)/n, a = 9.6954(2) angstrom, b = 15.0985(3) angstrom, c = 14.5090(3) angstrom, and beta = 104.925(2)degrees. (Tc3H)-Tc-99-(CO) 14 was additionally characterized by IR spectroscopy. The mechanism of hydrolysis of [Tc-99(CO)(6)]ClO4 was suggested.