Synthesis, characterisation, crystal structures and reactivity of a series of ruthenium-cobalt mixed-metal nitrido carbonyl clusters with iodide ligands

摘要

Reaction of [Ru_3(#mu#t-H)(CO)_9(#mu#_3-NOMe)] (I) with two equivalents of [Cp~*Co(CO)I_2] (Cp~* =#eta#-C_5Me_5) in refluxing THF resulted in the isolation of four new heterometallic tetranuclear nitndo clusters, namely [Ru_3Co(#mu#-H)(CO)_6(Cp~*){#mu#-#eta#~2- C(OMe)O}(#mu#_4-N)(#mu#-I)_2] (2), [Ru_3CoH(#mu#-H)_2(CO)_6(Cp~*){#mu#-#eta#~2- C(OMe)O}(#mu#_4-N)I(#mu#-I)_2](3), [Ru_3CoH(#mu#-H)_2(CO)_6(Cp~*){#mu#-#eta#~2- C(OMe)O}(#mu#_4-N)I(#mu#-I)_2] (4) and [Ru_3Co(#mu#-H)_2(CO)_8(#eta#~5-C_5Me_5)(#mu#_4-N)(#mu#-I)] (5), together with a triruthenium nitrene cluster [Ru_3(#mu#-H)_3(CO)_8(#mu#3-NOMe)I] (6) in moderate yields. The first four clusters have either a chain (2) or a spiked triangle (3—5) metal skeleton with the central nitrido atom capping all four metal atoms; alternatively, these four clusters can also be viewed as having a highly distorted butterfly arrangement. Clusters 2. 3 and 4 are isomers with different ligand dispositions. The hinge and an Ru—Ru wing-edge are missing in 2, whereas a wing-edge is lost in each of 3 and 4 (Ru—Ru) and 5 (Ru—Go). Opening up the hinge metal—metal bond has a significant effect upon the nitrido chemical shift in the ~(15)N-NMR spectrum. Clusters 3 and 4 differ from each other in the coordination site of a terminal iodide ligand, and both clusters are inter-convertible under vigorous conditions. Cluster 6 is a trihydrido nitrene cluster with a terminal iodide ligand. ~(15)N-NMR studies were performed in order to investigate the environment of the nitrogen atoms in these nitrido and nitrene clusters.