Chelation Processes to an Oxorhenium(V) Center by N,N,N,O-Tetradentate and N,N,O-Tridentate Ligands As Verified by Structural and Mechanistic Studies of Intermediate Species

The reaction of [ReO(OEt)Cl2(PPh3)2] with N-(2-pyridylmethyl)-2-aminoethanol (mpenOH) afforded a mixture of ReV−oxo complexes, from which the dichloro complex [ReOCl2(mpenO-N,N‘,O)] (1) and the chlorotriphenylphosphine complex [ReOCl(PPh3)(mpenO-N,N‘,O)]PF6 (2) were isolated by addition of NH4PF6. Similarly, [ReO(OEt)Cl2(PPh3)2] reacted with N,N-bis(2-pyridylmethyl)-2-aminoethanol (bpenOH) to give the dichloro complex [ReOCl2(bpenO-N,N‘,O)] (3) and the monochloro complex [ReOCl(bpenO-N,N‘,N‘‘,O)]PF6 (4). When ethylene glycol (H2eg) was added to the mixture of [ReO(OEt)Cl2(PPh3)2] and bpenOH, [ReO(eg)(bpenOH-N,N‘,N‘‘)]ReO4 (5) was obtained. These five newly prepared complexes were structurally characterized. A mechanistic insight into the stepwise complex formation reaction of [ReO(OEt)Cl2(PPh3)2] with pyridylmethylamine derivatives (mpenOH and bpenOH) is discussed. Crystal data:  [ReOCl2(mpenO)] (1), monoclinic, space group P21/c, a = 8.632(1) Å, b = 9.288(1) Å, c = 14.802(1) Å, β = 100.627(9)°, Z = 4; [ReOCl(PPh3)(mpenO)](PF6)·0.5CH3CN (2·0.5CH3CN), monoclinic, space group P21/a, a = 19.758(6) Å, b = 9.463(3) Å, c = 16.297(4) Å, β = 93.40(2)°, Z = 4; [ReOCl2(bpenO)] (3), monoclinic, space group P21, a = 6.577(1) Å, b = 13.269(2) Å, c = 9.686(2) Å, β = 105.00(2)°, Z = 2; [ReOCl(bpenO)](PF6) (4), triclinic, space group P1̄, a = 6.766(1) Å, b = 14.538(2) Å, c = 19.373(3) Å, α = 91.57(1)°, β = 97.43(1)°, γ = 91.62(1)°, Z = 4; [ReO(eg)(bpenOH)](ReO4) (5), monoclinic, space group P21/n, a = 12.691(2) Å, b = 14.030(2) Å, c = 11.153(2) Å, β = 90.72(1)°, Z = 4.