A modified preparation of the hydrochloride adduct of the potentially tridentate ligand bis(o-hydroxyphenyl)-phenylphosphine (abbreviated H2PO2 . HCl) is described. From this ligand and a potentially bidentate analog, (o-hydroxyphenyl)diphenylphosphine (HPO), POxx- (x = 1, 2) complexes of rhenium(V) and technetium(V) were prepared by metathesis reactions with the appropriate metal(V) precursor and/or by reduction/ligand-exchange reactions with ammonium perrhenate or pertechnetate. The new complexes fall into four categories : bis(PO) complexes (MOCl(PO)(2), M = Re or Tc, and ReN(PO)(2)(PPh(3))); mono(PO2) complexes (ReZCl(PPh(3))(PO2), Z = O or NPh); mixed(PO/PO2) complexes (ReZ(PO)(PO2), Z = O or NPh); and bis(PO2) complexes (MO(PO2)-(HPO2), M = Re or Tc). For the mono(PO2) phenylimido complexes, two facial isomers, cis- and trans-(P,P)-Re(NPh)Cl(PPh(3))(PO2), were isolated from different solvents. For the mixed(PO/PO2) complexes, fac-cis-(P,P)-ReO(PO)(PO2) and fac-trans-(P,P)-Re(NPh)(PO)(PO2) were prepared. Two non-interconvertible diastereomers were present in ReO(PO2)(HPO2) as evinced by P-31{H-1} NMR. The isomerism was shown to be derived from the orientation of the unligated hydroxyphenyl group of the HPO2- ligand. All the complexes were characterized by various physical techniques, including IR, MS, and (HP)-H-1-P-beta 1{H-1} NMR. The X-ray structures of fac-cis(P,P)-[Re(NPh)Cl(PPh(3))(PO2)]. 2CHCl(3) (1, C44H35Cl7NO2P2Re) and fac-cis-(P,P)-[ReO(PO)(PO2)] (2, C36H27O4P2Re) were determined. Crystals of 1 are triclinic, P (1) over bar, a = 11.997(1) Angstrom, b = 20.637(2) Angstrom, c = 10.511(1) Angstrom, alpha = 103.772(9)degrees, beta = 113.504(8)degrees, gamma = 76.072(9)degrees, Z = 2; and those of 2 are monoclinic, P2(1)/n, a 10.132(2) Angstrom, b = 14.026(3) Angstrom, c = 22.046(2) Angstrom, beta = 102.38(1)degrees, Z = 4. The two structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.034 and 0.030 (R(w) = 0.034 and 0.026) for 8203 and 5957 reflections with I greater than or equal to 3 sigma(I), respectively. The stnrctures of 1 and 2 reveal that the anchoring o-oxyphenyl groups strengthen the Re-P bonds significantly. The solution P-31{H-1} NMR spectra and the crystal structures both demonstrated cis-(P,P) geometry for each complex, with the Re atom being in the center of a highly distorted octahedron of cis-(chloro, phenylimido) atoms, two cis-(P,P) phosphine phosphorus atoms, and two phenolate oxygen atoms of the PO22- ligands for 1 and of one oxo oxygen atom, two cis-(P,P) phosphine phosphorus atoms, and three phenolate oxygen atoms of the PO22- and PO- ligands for 2.