Detailed Update of Diruthenium and Diosmium Chemistry

These new porphyrin compounds of Ru2+ are comparable to the previously known105) Ru2(C22H22N4)2, in which the bond length was found to be 2.379(1) A. There is only one other structurally characterized diruthenium(II,II) compound, namely, Ru2(mhp)4, where bridging by the 6-methyl-2-oxopyridine ligands occurs and the Ru-Ru distance is much shorter, 2.238(1) A106). 

It has been shown that Ru2(02CCH3)4C1 also reacts with molten benzamide to afford Ru2(HNOCPh)4Cl, a brown microcrystalline solid, rather insoluble in common solvents11. In DMSO solution it exhibits a reduction presumed to be to the Ru2(II,II) species at - 0.66 V. The most interesting thing about this compound, however, is the way in which it reacts with triphenylphosphine, to give a product with the following composition and structure  

Two more reactions of Ru2(02CCH3)4C1 with molten reagents have more recently been carried out,u). The reactions with 2-anilinopyridine and hydroxypyridine both lead 

Compound Os-Os dist., A Os-Cl dist., A Color Magnetic Moments, B.M. Ref. 

Diosmium(II,II) Compounds. The only known examples of these are porphyrin compounds, Os2(P)2, that are quite comparable to their ruthenium analogs123. They are prepared in a similar way, i.e., by pyrolysis of Os(P)py2 compounds. Again, mixed ligand dimers can be obtained, such as (TTP)Os=Os(OEP), and in addition the mixed metal compound, (OEP)Ru=Os(OEP) has also been formed and identified by NMR, although not isolated. No structural data have yet been reported for an Os2(P)2 compound. 

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