The reaction of equimolar quantities of trans-[ReOCl3(PPh3)(2)] and 8-hydroxyquinoline (Hhqn) in benzene led to the isolation of the six-coordinate complex [ReOCl2(hqn)(PPh3)] ( 1). With 2-pyridine-ethanol (Hhep) the compound [ReOCl2(hep)(PPh3)] ( 2) was obtained. Both hqn and hep ligands act as monoanionic bidentate N,O-donor chelates. Although the two complexes are very similar, there are some significant differences in certain bond distances and angles in them. Both complexes contain the nearly linear trans O = Re - O axis, with this angle equal to 160.9(2)degrees and 167.8(1)degrees in 1 and 2, respectively.

The neutral, mononuclear complex [ReO(mta)(2)Cl] (1) [Hmta=2-(methylmercapto) aniline] was prepared by reaction of trans-[ReOCl3(PPh3)(2)] with a twofold molar excess of Hmta in methanol. The oxo-bridged dimer (mu-O)[ReO(mta)(2)](2) (2) was synthesized by reacting [ReOCl3(PPh3)(2)] with a twofold excess of Hmta in a 9:1 acetone/water mixture. The compounds were characterized by spectroscopy and complex 1 also by X-ray crystallography. Complex 1 has a distorted octahedral geometry with the chloride coordinated trans to the oxo group, and with the chelating ligands in the equatorial plane in a cis-N cis-S configuration.

Reactions of trans-[ReOCl3(PPh3)(2)] and trans-[ReO(OEt)I-2(PPh3)(2)] with 2- aminophenol (H(2)ap) in acetonitrile led to the formation of cis-[ReOCl2(Hap)(PPh3)] (1) and trans-[Re(ap)(Hap)I(PPh3)(2)]I (2), respectively. The X-ray crystal structures show that Hap is coordinated as a bidentate chelate via the neutral amino nitrogen and deprotonated phenolate oxygen, and ap is coordinated as a monodentate through the imido nitrogen. The complexes have been characterized by IR spectroscopy, NMR spectrometry and X-ray crystallography. The bite angle of the Hap chelate is 76.9(1)degrees and 76.0(1)degrees in 1 and 2, respectively.

2,3-Diaminopyridine (H(2)dap) reacts with (n-Bu4N)[ReOCl4] to form an air-stable salt of composition [ReO(Hdap)(2)]Cl center dot 2H(2)O. Spectroscopic studies and X-ray crystallography show that Hdap is coordinated in the monoanionic diamidopyridinium mode to the oxorhenium(V) center. The protonation of the pyridyl nitrogens and the charge on the complex have no influence on the bond lengths and angles, with the rhenium(V)-oxo and average Re-NH bond lengths equal to 1.688(4) and 1.993(5) angstrom, respectively.

The reactions of the tetradentate amine-phenol type Schiff bases H(2)sal(2)en(1,2-ethylenebis(salicylideneimine) and H(2)sal(2)mp (1,2-benzylenebis(salicylideneimine)) with trans-[ReOCl3(PPh3)(2)] or (n-Bu4N)[ReOCl4] in air gave the products (mu-O)[ReO(sal(2)en)](2) (1) and [ReOCl(sal(2)mp)] (2), respectively. X-ray and spectroscopic studies have shown that 1 contains the linear O=Re-O-Re=O grouping, with the four donor atoms of sal(2)en(2-) coordinating in the square plane cis to the oxo ions. In 2, a cis oxo-chloro arrangement is observed with a phenolic oxygen being coordinated trans to the oxo group. The terminal Re=O bond lengths in 1 and 2 are 1.709(4) and 1.683(3) angstrom, respectively.

The complex [ReOI2(ame)(PPh3)] (Hame=2-(2-aminophenyl)ethanol) was prepared from trans-[ReOI2OEt) (PPh3)(2)] and Hame in benzene. It contains an unusually long Re==O bond (1.717(5) Angstrom) and a large trans O==Re-O (ethanolate) bond angle of 171.4(2)degrees.

The complex [Re(ddcat)(3)] (H(2)ddcat = 3,5-di-ter-butylcatechol) was prepared by the reaction of either cis-[(ReO2I)-O-v(PPh3)(2)] or (n-Bu4N)[(ReOCl4)-O-V] with H(2)ddcat in toluene in air. X-ray structure determination of the product unequivocally illustrates that the bidentate chelates are in the catecholato rather than the semiquinone form and that the metal has a formal oxidation state of +VI.

The cationic complex [ReO(ahp)2(PPh3)]+ was isolated as the chloride salt from the reaction of trans-[ReOCl3(PPh3)2] and 2-amino-3-hydroxypyridine (Hahp) in ethanol. Coordination of the chelates only occurs through the amino nitrogen and the phenolate oxygen of ahp−. The X-ray crystal structure shows a distorted octahedral geometry, in which a phenolate oxygen coordinated trans to the oxo group and the rhenium atom is displaced by 0.2520(1) Å out of the mean equatorial plane towards the oxo oxygen.

The complex [ReO(Hamb)(H2amb)(PPh3)] (1) was prepared by the reaction of cis-[ReO2I(PPh3)2] with two equivalents of 2-amino-3-methylbenzoic acid (H3amb) in toluene under reflux conditions. Crystallographic data show that 1 contains the coordinated amidobenzoate chelate (Hamb) and symmetrically chelating carboxylate ion (H2amb) in a pseudo-octahedral geometry.

The reaction of a twofold molar excess of 2-aminothiophenol (H2L) with trans-[ReOCl3(PPh3)(2)] in benzene led to the isolation of the oxo-free rhenium(V) complex [ReCl(PPh3)L-2] (1). IR, H-1 NMR and X-ray crystallographic results indicate that the ligands L coordinate ill a dianionic amidothiolate form to the metal and that the complex has the unusual skew-trapezoidal bipyramidal geometry. The ligands L have an average bite angle of 78.8(1)degrees, with average Re-N and Re-S bond lengths equal to 1.978(5) and 2.297(1) Angstrom, respectively.

The reaction of a twofold molar excess of 2-amino-3-methylbenzoic acid (H(3)amb) with cis-[ReO2I(PPh3)(2)] in ethanol led to the isolation and characterization of the six-coordinate [Re(amb)(OEt)I(PPh3)(2)] (1). The X-ray crystal structure of 1 illustrates that the trianionic ligand amb acts as a bidentate chelate via the doubly deprotonated amino nitrogen, which is present in 1 as an imide, and the deprotonated acetoxy oxygen. The Re=N bond length is 1.751(3) Angstrom, and the Re=N-C angle [143.6(3)degrees] deviates considerably from linearity.

The reaction of cis-[ReO2I(PPh3)2] with 3-methyl-2-aminophenol (H2map) in ethanol led to the formation of trans-[Re(map)(Hmap)I(PPh3)2]I. The X-ray crystal structure shows that the ligand map is coordinated monodentately through the doubly deprotonated amino nitrogen and is therefore present as an imide. The chelate Hmap is coordinated via the neutral amino nitrogen and the singly deprotonated phenolate oxygen, which is coordinated trans to the imido nitrogen. In benzene equimolar quantities of cis-[ReO2I(PPh3)2] and 4-methyl-2-aminophenol (H2amp) produced the five-coordinate cis-[ReO2(Hamp)(PPh3)]. A twofold molar excess of 2-aminophenol (H2ap) yielded the six-coordinate [ReO(Hap)(ap)(PPh3)]. The chelate ap is coordinated through the deprotonated phenolate oxygen and the singly deprotonated amino nitrogen (amide).

Reactions of trans-[ReO2(py)4Cl] and cis-[ReO2I(PPh3)2] with 2,3-diaminophenol (H2dab-OH) and 1,2-diaminobenzene (H2dab), respectively, in ethanol under aerobic conditions led to the corresponding isolation of [Re(sbqdi-OH)3]Cl (1) and [Re(sbqdi)3]I (2). Crystallographic data show that the ligand sbqdi represents the monoanionic N,N-coordinated π-radical form of the 1,2-benzosemiquinone diimine of H2dab. The ligands in Complex 1 clearly show semiquinoid character; e.g., the two C-N and two Re-N bondlengths differ considerably. In 2, the phenyl rings display typical quinoid distortions with two localized double bonds, and the C-N bondlengths are short, approaching double bonds. Rhenium is formally in the +IV oxidation state.

The complex cis-[ReO2(Hdab)(py)2] (1) (H2dab=1,2-diaminobenzene) has been prepared by reacting trans-[ReO2(py)4]I with H2dab in ethanol. This is the first example of a neutral hexacoordinate rhenium(V) complex with a cis arrangement of the two oxo groups. The compound also provides the first example of a bidentate monoanionic monoimino coordination mode of H2dab. Crystal data for 1·(H3dab)I·H2O: C22H26IN6O2Re·H2O, triclinic, space group P1̄, a=9.570(2), b=12.493(3), c=12.851(3) Å, α=61.60(3), β=70.56(3), γ=78.68(4)°, V=1273.1(4) Å3 and Z=2.