The syntheses and structures of ‘3+2’ and ‘2+2+1’ oxorhenium mixed-ligand complexes employing 8-hydroxy-5-nitroquinoline as the bidentate N,O donor ligand

The syntheses and structural characterizations of a series of novel ‘3+2’ and ‘2+2+1’ mixed-ligand complexes carrying 8-hydroxy-5-nitroquinoline (HL) as the bidentate N,O donor atom system are reported. Thus, one-pot reactions of [ReOCl3(PPh3)2] with dianionic tridentate ligands H2Ln (where H2L1=HOC6H4-2-CHNC6H4-2-OH; H2L2=HOC6H4-2-CHNC6H4-2-SH; H2L3=HOC6H4-2-CHNNC(NHC6H5)SH; H2L4=2-CH2OHC5H3N-6-CH2SH; and H2L5=2-CO2HC5H3N-6-CO2H) and HL afforded a series of ‘3+2’ oxorhenium complexes of the type [ReO(H2Ln)(L)] 2–6, which exhibit distorted octahedral geometries. Crystals of 1 are monoclinic, space group C2/c, a=16.702(1), b=14.275(1), c=22.363(2) Å, β=108.083(1)°, V=5068.2(7) Å3 and Z=8; those of 2 are monoclinic, space group P21/n, a=8.5093(4), b=38.518(2), c=11.6092(5) Å, β=97.708(1)°, V=3770.7(3) Å3 and Z=8; those of 5 are triclinic, space group P1̄, a=7.5899(8), b=10.322(1), c=11.905(1) Å, α=78.636(2)°, β=74.229(2)°, γ=71.391(2)°, V=844.3(2) Å3, and Z=2. Upon reaction of 2,6-pyridinedimethanol (H2L6) with the intermediate complex [ReOCl2(L)(PPh3)] (1), only one of the two methylene hydroxy group was deprotonated and a new ‘2+2+1’ complex [ReO(OCH3)(HL6)(L)]·CH3OH (7) was obtained. Crystal data for 7: monoclinic, P21/n, a=12.0579(6), b=11.0993(6), c=14.9262(8) Å, β=107.872(1)°, V=1901.2(2) Å3, and Z=8. In the preparation of complex 3, cleavage of the CN bond of the Schiff base H2L2 was observed, and the ‘2+2+1’ complex 8 [ReO(PPh3)(η2-NHC6H4-2-S)(L)]·CH2Cl2 having 2-aminothiophenol as a dianionic bidentate ligand was isolated. Crystals of 8 are monoclinic, space group C2/c, a=25.627(2), b=8.1305(6), c=31.404(2) Å, β=96.147(1)°, V=6505.7(8) Å3, and Z=8. Reduction of HL to 8-hydroxy-5-aminoquinoline was realized during the formation of complex 6, and a new complex 9 was thus isolated involving the coordination of two sets of N,O donor atoms from L and 8-hydroxy-5-aminoquinoline, while a methoxy oxygen atom completes the octahedral coordination geometry. Crystals of 9 are monoclinic, space group P21/n, a=7.5330(6), b=15.095(1), c=16.394(1) Å, β=99.690(2)°, V=1837.7(3) Å3, and Z=4.