Ruthenium complexes carbonyl donor ligands

Similarly, treatment of the nickel-ruthenium complex 62 with a variety of donors (CO, CNCy, NCfBu, PPh3) affords the doubly bridged complexes 78-81 (Scheme 7), wherein the donor binds to ruthenium. However, upon treatment with PhC=CH, only one carbonyl adopts a bridging mode, the second bridge being provided by a r2 vinylidene (63), derived from a 1,2-hydride shift within the PhC=CH ligand. 

This reaction has been extended further to other porphyrins, and also to other axial ligands such as DMSO, THF, and amines. A similar photodecarbonylation is observed when the osmium(II) carbonyl complex Os(OEP)(CO)py is photolyzed in the presence of pyridine. Room temperature transient absorption studies on ruthenium(II) porphyrin carbonyl complexes show that there are significant differences in the nature of the lowest excited state for series of complexes having different axial ligands. For the complexes Ru(OEP)L2 and Ru(TPP)L2, where L is a (T-donor ligand such as pyridine, the complexes exhibit charge transfer... 

The reaction mechanism is similar to the one employed by Raubenheimer el al. for their chromium(O) thiazol-2-ylidene complex [48], In the case of the ruthenium imidazol-2-ylidene complexes, 4,5-dimethylimidazole stabilised the carbene complex compared with unsubstituted imidazole. Likewise, the carbonyl ligand in trans position was necessary to isolate and crystallise the complex. This can be expected, when an excellent o-donor (NHC) is trans to an excellent tr-acceptor (CO). 

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