The complexes cis-Tp(Pr)Mo(VI)O(2)(OAr-R) (Tp(Pr) = hydrotris(3-isopropylpyrazol-1-yl)borate, -OAr-R = hydrogen-bonding phenolate derivative) are formed upon reaction of Tp(Pr)MoO(2)Cl, HOAr-R, and NEt3 in dichloromethane. The orange, diamagnetic, dioxo-Mo(VI) complexes exhibit strong V(MoO2) IR bands at ca. 935, and 900 cm(-1) and NMR spectra indicative of C, symmetry. They undergo electrochemically reversible, one-electron reductions at potentials in the range -0.836 to -0.598 V vs SCE; the only exception is the 2-CO2Ph derivative, which exhibits an irreversible reduction at -0.924 V. The complexes display distorted octahedral geometries, with a cis arrangement of terminal oxo ligands and with d(MO=O)(av) = 1.695 angstrom and angle(MoO2)(av) = 103.2 degrees. The R groups of the 2-CHO and 2-NHCOMe derivatives are directed away from the oxo groups and into a cleft in the Tp(Pr) ligand; these derivatives are characterized by Mo-O-C-ipso angles of ca. 131 degrees (conformation 1). The R group(s) in the 2-CO2Me and 2,3-(OMe)(2) derivatives lie above the face of the three O-donor atoms (directed away from the Tp(Pr) ligand) and the complexes display Mo-O-C-ipso angles of 153.1(2) and 149.7(2)degrees, respectively (conformation 2). Conformations 1 and 2 are both observed in the positionally disordered 2-COMe and 2-COEt derivatives, the two conformers having Mo-O-C-ipso angles of 130-140 and >150 degrees, respectively. The 8-COMe and 3-NEt2 derivatives have substituents that project away from the TpPr ligand and Mo-O-C-ipso angles of 134.2(2) and 147.7(2)0, respectively. Many of the complexes exhibit fluxional behavior on the NMR time scale, consistent with the rapid interconversion of two conformers in solution.