| 15606213 |
Tisato F, Refosco F, Porchia M, Bolzati C, Bandoli G, Dolmella A, Duatti A, Boschi A, Jung CM, Pietzsch HJ, Kraus W: The crucial role of the diphosphine heteroatom X in the stereochemistry and stabilization of the substitution-inert [M (N)(PXP)] 2+ metal fragments (M = Tc, Re; PXP = diphosphine ligand). Inorg Chem. 2004 Dec 27;43(26):8617-25.
The nature of the heteroatom X incorporated in the five-membered PXP-diphosphine bridging chain was found to play a primary unit role both in the overall stability and in the stereochemical arrangement of nitrido-containing [M (N)(PXP)](2+) metal fragments (M = Tc, Re). Thus, by mixing PXP ligands with labile [Re (N) Cl (4)](-) and Tc (N) Cl (2)(PPh (3))(2) nitrido precursors in CH (2) Cl (2)/MeOH mixtures, a series of neutral M (N) Cl (2)(PXP) complexes (M = Tc, 1-5; M = Re, 8, 9) was collected. In the resulting distorted octahedrons, PXP adopted facial or meridional coordination, and combination with halide co-ligands produced three different stereochemical arrangements, that is, fac,cis, mer,cis, and mer,trans, depending primarily on the nature of the diphosphine heteroatom X. When X = NH, mer,cis-Tc (N) Cl (2)(PNP1), 1, was the only isomer formed. Alternatively, when a tertiary amine nitrogen (X = NR; R = CH (3), CH (2) CH (2) OCH (3)) was introduced in the bridging chain, fac,cis-M (N) Cl (2)(PN (R) P) complexes (M = Tc, 2, 3; M = Re, 8f) were obtained. Isomerization into the mer,cis-Re (N) Cl (2)(PN (R) P), 8m, species was observed only in the case of rhenium when the tertiary amine group carried the less encumbering methyl substituent. fac,cis-Tc (N) Cl (2)(PSP), 4f, was isolated in the solid state when X = S, but a mixture of fac,cis-Tc (N) Cl (2)(PSP) and mer,trans-Tc (N) Cl (2)(PSP), 4m, isomers was found in equilibrium in the solution state. A similar equilibrium between fac,cis-M (N) Cl (2)(POP) (M = Tc, 5f; M = Re, 9f) and mer,trans-M (N) Cl (2)(POP) (M = Tc, 5m; M = Re, 9m) species was detected in POP-containing complexes. The molecular structure of all of these complexes was assessed by means of conventional physicochemical techniques including multinuclear NMR spectroscopy and X-ray diffraction analysis of representative mer,cis-Tc (N) Cl (2)(PN (H) P), 1, fac,cis-Tc (N) Cl (2)(PSP), 4f, and mer,cis-Re (N) Cl (2)(PN (Me) P), 8m, compounds. |
1(0,0,0,1) |