Uncommon Anionic Dioxorhenium(V) and Neutral Monooxorhenium(V) Mixed-Ligand Complexes Containing Heterofunctionalized Phosphine Ligands: Syntheses and Structural Characterization

The potentially bidentate hybrid ligand ( o -hydroxyphenyl)diphenylphosphine, abbreviated POH, reacted via ligand-exchange with pentavalent rhenium precursors to give a series of six-coordinate mono- and dioxo complexes. Accurate control of the metal:ligand stoichiometric ratio allowed for the isolation of the mono-substituted [ReOCl 3 (PO)] - ( 1 ) and [ReOCl 2 (PO)(PPh 3 )] ( 2 ) derivatives. 1 was found to be the key intermediate for the syntheses of three more types of bis-substituted compounds: anionic dioxo [ReO 2 (PO) 2 ][A] (A = NBu 4 ( 3 ), AsPh 4 ( 4 )), neutral monooxo [ReOX(PO) 2 ] (X = Cl ( 5 ), Br ( 6 ), I ( 7 )), and neutral monooxo mixed-ligand [ReOX(PO)(PNH)] [PNH = ( o -amidophenyl)diphenylphosphine; X = Cl ( 8 ), Br ( 9 ), I ( 10 )] complexes. In the mono-substituted complexes, the P,O-donors of the bidentate ligand spanned an equatorial (P) and the apical position (O) trans to the Re O linkage in a distorted octahedral arrangement. In all of the bis-substituted monooxo compounds, the second chelate ligated on the equatorial plane almost orthogonally positioned with respect to the first one, the two phosphorus donors showing a mutual cis -(P,P) orientation. Dioxo complexes retained the cis -(P,P) configuration with the bidentate ligands symmetrically coordinated on the equatorial plane normal to the trans- ReO 2 core. All the complexes were characterized by various physical techniques, including IR, MS, and 1 H/ 31 P{ 1 H} NMR. The X-ray structure of a representative compound for each category, namely [ReOCl 3 (PO)][NBu 4 ] ( 1 ), [ReO 2 (PO) 2 ][AsPh 4 ] ( 4 ), [ReOCl(PO) 2 ] ( 5 ), and [ReOCl(PO)(PNH)] ( 8 ), were determined. Crystals of 1 were monoclinic, P 2 1 / n, a = 10.840(3) Å, b = 22.167(6) Å, c = 15.210(4) Å, β = 95.91(2)°, and Z = 4; those of 4 were triclinic, P 1̄, a = 12.679(7) Å, b = 13.082(7) Å, c = 19.649(8) Å, α = 82.64(4)°, β = 81.16(4)°, γ = 62.27(3)°, and Z = 2; those of 5 were orthorhombic, a = 10.225(4) Å, b = 14.208(6) Å, c = 21.771(9) Å, P 2 1 2 1 2 1, and Z = 4; and those of 8 were orthorhombic, a = 10.199(2) Å, b = 14.147(4) Å, c = 21.772(6) Å, P 2 1 2 1 2 1, and Z = 4. The four structures were solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.050, 0.063, 0.043, and 0.039 for 1, 4, 5 and 8, respectively. Both solution state ( 31 P{ 1 H} NMR) and solid state (X-ray) demonstrated a cis -(P,P) arrangement for each bis-substituted complex, with the Re atom at the center of a highly distorted octahedron. Detailed analyses of the IR spectra of this series of Re(V) compounds in the region 900−580 cm - 1 allowed us the possibility to distinguish between symmetrical and asymmetrical bis-substituted complexes.