F-19 and P-31 NMR spectra are used to demonstrate that the reaction between HfF4 (.) H2O and Ph2P(O)-N=PPh2OH (HL) in a mixture of equal volumes of dmso and CH2Cl2 results in the octahedral complexes cis-HfF2L2, cis-HfF2(dmso)(2)(+), fac-HfF3L(dmso), and cis-HfF4L- with chelating ligand L- and HfF62-. The existence of isomers of dimeric complexes (mu-F-2)(HfF(3)Q)(2), where Q = dmso or H2O, with CN = 7 is suggested on the basis of the F-19 NMR spectra obtained at temperatures below 203 K. With a twofold excess of HL, HfF2L2(dmso) single crystals are isolated. The crystals are characterized by IR spectroscopy and X-ray crystallography. The monoclinic unit cell parameters are as follows: space group P21/c, a = 11.560(3) Angstrom, b = 23.444(4) Angstrom, c = 18.198(4) Angstrom, beta = 101.06(2)degrees, V = 4840(4) Angstrom(3), Z = 4, mu(MoKalpha) = 0.44 mm(-1). In HfF2L2(dmso), the central ion has a distorted octahedral surrounding (which is atypical of fluorine compounds of hafnium) with two cis fluorine atoms and two cis-chelating ligands L-. One of the chelate rings has a half-boat conformation; the other is a flattened chair. When HfF2L2(dmso) reacts with SbF3, fluoride ions displace the coordinated L- from the inner sphere of the complex.