COMPLEXES OF RHENIUM(V) WITH TRIDENTATE LIGANDS HAVING O-DONOR, N-DONOR AND P-DONOR ATOMS - THE X-RAY CRYSTAL-STRUCTURES OF REOCL2[OC6H4-2-CH=N(CH2)3PPH2] AND ITS REDUCED COUNTERPART REOCL2[OC6H4-2-CH2NH(CH2)3PPH2]

The tridentate ligand HOC6H4-2-CH2NH(CH2)3PPh2, which contains both "hard" and "soft" potential donor atoms, has been synthesized along with its rehenium(V) complex ReOCl2[OC6H4-2-CH2NH(CH2)3PPh2]. Single crystal X-ray diffraction studies show that this molecule has a qualitatively similar structure to its Schiff base counterpart ReOCl2[OC6H4-2-CH = N(CH2)3PPh2], despite the change in bonding at the central ligating nitrogen atom from sp3 to sp2. At a more detailed level, significant differences in structural parameters are found to occur. In both cases the coordination site trans to the Re = O oxygen [Re = O = 1.680(7) and 1.695(9) angstrom, respectively] is occupied by the phenolic oxygen [Re-O = 1.943(7) and 1.953(9) angstrom, respectively] and the rhenium atom has a distorted octahedral coordination environment. The Re-N distance lengthens on reduction of the ligand [Re-N(H)- = 2.224(8) angstrom, Re-N = = 2.111(11) angstrom] while the Re-N = C(sp2.) bond angle decreases by 12.7-degrees on reduction.