Synthesis, characterization and crystal structures of a series of ruthenium μ₄-nitrene carbonyl clusters

Methylation of [Ru3(CO)10(NO)]-anion has led to the isolation of [Ru6(μ-H)(CO)16(μ-CO)(μ4-NH){μ3-η2-C(O)OMe}] 1 in addition to the major product [Ru3(CO)10(NOMe)] 2. Hydrogenation of 2 in refluxing hexane gave [Ru3(μ-H)2(CO)9(NH)] 3 and [Ru3(μ-H)2(CO)9(NOMe)] 4 in moderate yields, but in the presence of [Ru3(CO)12] it gave [Ru6(μ-H)(CO)16(μ-CO)2(μ4-NH)(μ-OMe);] 5 and [Ru5(μ-H)3(CO)13(μ4-NH)(μ3-OMe)] 6 in addition. Thermolysis of 2 in toluene at 90°C for 3 h yielded [Ru4(CO)12(μ4-N)(μ-OMe)] 7 and [Ru6(CO)16(μ-CO)2(μ4-NH)(μ-OMe)2] 8. Pyrolysis of 4 at 140°C for 2 h afforded [Ru6(CO)15(μ-CO)2(μ4-NH)(μ-OMe){μ3-η2-N(H)C(O)OMe}] 9, [Ru6(μ-H)2(CO)14(μ-CO)2{μ5-η2-NC(O)OMe}] 10 and [Ru6(CO)16(μ-CO)2(μ4-NH)(μ-OMe)(μ-NCO)] 11 together with the known clusters [Ru4H2(CO)13] and [Ru3(μ-H)(CO)10(NH2)]. The crystal structures of 1 and 3-11 have been determined. Clusters 1, 5, 6, 8, 9 and 11 consist of a square-pyramidal 'Ru4(CO)8(μ4-NH)' moiety with four ruthenium atoms forming a square-planar base which is capped by a quadruply bridging nitrene ligand. For 1, 5, 8, 9 and 11, two additional ruthenium fragments bridge the opposite edges of the Ru4(CO)8(μ4-NH) metal core to give 'boat' form hexaruthenium nitrene compounds. Compound 6 also has a Ru4(CO)8(μ4-NH) moiety, but with only one bridging Ru(CO)4fragment at one of the Ru-Ru edges of the tetraruthenium plane while the remaining three are bridged by hydrides. Compound 10 comprises a square-pyramidal array of five ruthenium atoms with a Ru(CO)3unit bridging one of the Ru-Ru edges of the base. The other side of the square plane is quadruply capped by the nitrogen atom of a NC(O)OMe ligand with the oxygen atom of the acyl group bonded to the apical Ru(CO)3unit. Compound 7 possesses a butterfly arrangement of four Ru atoms with the methoxy group bridging the hinge.