Synthesis and reactivity of nitrido-rhenium and -osmium complexes with an oxygen tripod ligand

Interaction of [ReNCl3(PPh3)(2)] or [ReOCl2(PPh3)(3)] with NaLOEt (L-OEt=[Co(eta(5)-C5H5){PO(OEt)(2)}(3)]) afforded [ReLOEtN(PPh3)Cl] 1 and [ReLOEtOCl2] 2, respectively. Reaction of 1 with AgBF4 gave the nitridorhenium(VI) complex [ReLOEtN(PPh3)Cl]BF4 1 . BF4, which has a mu(eff) of 1.8 mu(B). Treatment of 1 with MeOSO2CF3, PhCH2Br or [Ph3C]BF4 afforded the respective organoimido species [ReLOEt(NMe)(PPh3)Cl][CF3SO3] 3, [ReLOEt(NCH2Ph)(PPh3)Cl]Br 4, and [ReLOEt(NCPh3)(PPh3)Cl] 5. Reaction of 1 with [Au(PPh3)(CF3SO3)], [Ru(Et(2)dtc)(PPh3)(2)(CO)(CF3SO3)], or [ReMeO3] yielded the bimetallic nitrido complexes [Au(PPh3){NReLOEt(PPh3)Cl}][CF3SO3] 6, [Ru(Et(2)dtc)(PPh3)(H2O)(CO){NReLOEt(PPh3)Cl}][CF3SO3] 7 or [ReMeO3{NReLOEt(PPh3)Cl}] 8, respectively. Treatment of [NBu4n][OsNCl4] with NaLOEt gave [OsLOEtNCl2] 9. The average Os-O, Os-Cl and Os-N distances in 9 are 2.066, 2.289 and 2.58(1) Angstrom, respectively. Reaction of 9 with PPh3 afforded the osmium(IV) phosphoran iminate species [OsLOEt(NPPh3)Cl-2] 10, which has a mu(eff) of 2.0 mu(B). The average Os-O, Os-Cl and Os-N distances in 10 are 2.099, 2.342, 1.893(5) Angstrom, respectively, the Os-N-P angle being 137.5(3)degrees. The formal potentials of the L-OEt-Re and -Os complexes have been determined by cyclic voltammetry. On the basis of the Re-VI-Re-V formal potential, the pi-donor strength was found to decrease in the order N3->[NAu(PPh3)](2-)> NMe2-.