Reactions of Ph2P(O)(OH) and t-BuP(O)(OSiMe3)(OH) with Ti(O-i-Pr)(4) in equimolar ratios gave titanium phosphonates of the type [(O-i-Pr)(3)Ti(mu-O)(2)(PRR2)-R-1](2) (1, R-1 = R-2 = Ph; 2, R-1 = t-Bu, R-2 = OSiMe3) as colorless crystalline solids in moderate yields. Reactions of Ph2P(O)(OH) and the isopropoxides of zirconium and hafnium resulted in products of the composition [(O-i-Pr)(3)M(mu-O-i-Pr)(2)(mu-OPOPh2)M(O-i-Pr)(2)]Ph2P(O)(OH) (M = Zr (3), Hf (4)) in high yields. The compounds were characterized by H-1, (31)p, and Si-29 NMR, infrared (IR), and mass spectroscopic (MS) techniques. The molecular structures of 2 and 3 were confirmed by X-ray crystallography.