Oxygen atom transfer from nitrogenous ReVO reagents to diphosphines and subsequent transformations. Rhenium(III) products and reaction models

Abstract

The concerned diphosphines are Ph₂P(CH₂)_nPPh₂ (1), abbreviated PnP, and the Re^VO reagents are ReOCl₃L (2) and ReOCl₃L' (3), where L and L' are the azopyridine and pyridine-imine ligands p-ClC₆H₄NNC₅H₄N and p-MeC₆H₄NCHC₅H₄N, respectively. One atom transfer from 2 to 1 has afforded Re(OPnP)Cl₃L (4a, n = 1; 4b, n = 2; 4c, n = 3). Of these 4b and 4c are stable, but 4a undergoes spontaneous isomerization to Re(PlPO)Cl3L (5) in solution. Two-atom transfer studied with both 2 and 3 has afforded binuclear LCl₃Re(OPnPO)ReCl₃L (8a, n = 2; 8b, n = 3) and L'Cl₃Re(OPnPO)ReCl₃L' (9a, n = 2; 9b, n = 3) for n = 2, 3 and mononuclear Re(OP1PO)Cl3L (11) and Re(OP1PO)Cl3L' (12) for n = 1. The mixed system L'Cl3Re(OP2PO)ReCl₃L (10) has been prepared from 3 and 4b. The complex Re(PPh₃)Cl₃L (7a) is furnished by the reaction of Re(OPPh3)Cl₃L (6a) or 4b or 11 with PPh₃. The species have been characterized with the help of spectral, electrochemical, and X-ray structural data. All the complexes have mer geometry except 5 and 7a, which have fac geometry. The latter is best suited for concurrent Re-N and Re-P back-bonding. Variable-temperature rate data of the reaction 4a → 5 are consistent with an intramolecular strongly associative transition state (ΔS++, -22.6 eu) in which the dangling phosphine function lies close to the metal. Two-atom transfer to P1P is believed to proceed via a transient binuclear intermediate which undergoes cleavage at one end due to steric crowding, affording 11 and 12. Crystal data for the complexes are as follows: 5·1.5 C₆H₆, empirical formula C₄₅H₃₉Cl₄N₃OP₂Re, crystal system triclinic, space group P, a = 10.034(2) Å, b = 10.737(2) Å, c = 20.357(4) Å, α= 89.38(3)°, β = 87.79(3)°, γ= 80.22(3)°, V = 2159.7(7) A3, Z = 2; 7a·CH₂Cl₂, empirical formula C₃₀H₂₅Cl₆N₃PRe, crystal system monoclinic, space group P21/n, a = 11.695(6) Å, b = 17.745(7) Å, c = 15.459(9) Å, β = 100.94(5)°, V = 3150(3) Å3, Z = 4; 9a, empirical formula C₅₂H₄₈Cl₆N₄O₂P₂Re₂, crystal system monoclinic, space group C2/c, a = 19.769(12)Å, b = 12.864(6) Å, c = 22.20(2) Å, β = 101.76(6)°, V = 5530(6) Å3, Z = 4; 11, empirical formula C₃₆H₃₀Cl₄N₃O₂P₂Re, crystal system monoclinic, space group I2/a, a = 16.866(6) Å, b = 12.583(6) Å, c = 34.78(2) Å, β = 99.22(4)°, V = 7285(7) Å3, Z = 8.