The rhenium polyhydride complex ReH7(PPh3)2 reacts with various organic acids to give neutral monohydrido rhenium(III) complexes of stoichiometry ReH(L)2(PPh3)2, where L represents the monoanion of pyridine-2-carboxylic acid (pic), l-iso-quinolinecarboxylic acid (isoquin), pyridine-2,3-dicarboxylic acid (quin), 2-hydroxypyridine (hp), 2-hydroxy-6-methylpyridine (mhp), and acetylacetone (acac). These complexes display a reversible couple in their cyclic voltammograms (recorded in 0.1 M n-Bu4NPF6/CH2Cl2), which is associated with a one-electron oxidation to their 17-electron cations. The complexes where L = pic, isoquin, mhp, and acac have been oxidized to form their paramagnetic Re(IV) congeners [ReH(L)2(PPh3)2]PF6, using [(η5-C5H5)2Fe]PF6 as the oxidant. These are rare examples of mononuclear Re(IV) hydride complexes; their reduction back to the neutral Re(III) precursors has been accomplished with the use of (η5-C5H5)2Co. The complexes [ReH(pic)2(PPh3)2]PF6 (1), ReH(acac)2(PPh3)2 (2), and [ReH(acac)2(PPh3)2]PF6 (3) have been structurally characterized by X-ray crystallography. Crystal data for 1 at 20 °C: space group C2/c, a = 18.730 (5) Å, b = 19.877 (2) Å, c = 24.355 (4) Å, β = 90.46 (2)°, V = 9066 (5) Å3, and Ζ = 8. The structure was refined to R = 0.036 and Rw = 0.041 for 3814 data with I > 3.0σ(I). Crystal data for 2 at 20 °C: space group P1, a = 11.892 (3) Å, b = 12.436 (2) Å, c = 15.713 (4) Å, α = 90.45 (2)°, β = 98.21 (2)°, γ = 115.53 (2)°, V = 2069 (2) Å3, and Ζ = 2. The structure was refined to R = 0.032 and Rw = 0.042 for 4920 data with I > 3σ(I). Crystal data for 3 at 21 °C; space group P21/c, a = 10.644 (3) Å, b = 19.803 (4) Å, c = 21.298 (6) Å, β = 92.48 (2)°, V= 4485 (4) Å3, and Ζ = 4. The structure was refined to R = 0.051 and Rw = 0.060 for 4088 data with I > 3.0σ(I). All three complexes have closely similar structures, which can be described in terms of distorted-pentagonal-bipyramidal or capped-octahedral geometries. Only in the case of 2 was the hydride ligand located in the structure analysis. The Re-Η distance in 2 is 1.54 (5) Å. © 1990, American Chemical Society. All rights reserved.
