Unusual Synthesis of Triosmium Carbene Clusters by Tandem Activation of Chlorohydrocarbons and Heterocyclic Amines

Reactions of the [Os3H2(CO)(10)] cluster complex (1) with six-membered heterocyclic amines (morpholine, thiomorpholine, piperidine) and halohydrocarbons (CH2Cl2, ClHC=CHCl, CH2=CCl2) at similar to 25 degrees C have been studied. Two main types of products are formed in all studied reactions. One product is carbene cluster [Os-3(mu-H)(mu-Cl){eta(1)-C(CH3)N(CH2CH2)(2)X}(CO)(9)] (X=O, S, CH2) (3, 3 a and 3 b). Second product is cluster containing enamine ligand [Os-3(mu-H){mu-CH=CHN(C2CH2)(2)X)}(2)(CO)(10)] (X=O, S, CH2) (2, 2 a and 2 b). The carbene ligand is assembled on a cluster, from three organic molecules, thus representing the first example of carbene ligands formed in this way. Clusters with carbene ligand exist as two stable isomers (rotamers hindered towards the Os-C bond), as confirmed by NMR studies and conformational analysis. We have found that in reactions of cluster 1 with acyclic amines containing an oxygen atom in gamma-position (likely morpholine in CH2Cl2), only complexes with bridging enamine ligands are formed. Compounds 2 a, 2 b, 3 and 3 b are characterized by single-crystal X-ray diffraction.

Automated summary

Reactions of the [Os3H2(CO)(10)] cluster complex with six-membered heterocyclic amines and halohydrocarbons at around 25 degrees C lead to the formation of two main types of products: carbene cluster and cluster containing enamine ligand. The carbene ligand is assembled on the cluster from three organic molecules, representing the first example of carbene ligands formed in this manner. The clusters with carbene ligand exist as two stable isomers, as confirmed by NMR studies and conformational analysis.