Osmium complexes ethylenediamine

There are now a substantial number of nitrido complexes of osmium(VI) and osmium(IV) as well as the osmiamate ion [OsVII 03N]. In addition to the ammine and ethylenediamine complexes, much recent work has been carried out on the bipy, phen and terpy complexes, often in connection with research into the photodissociation of water. The nitrosyl chemistry of the element, though seemingly not as extensive as that of ruthenium, has received much attention, and there has been considerable work on the phosphine, arsine and stibine complexes. 

Nitrogen is, after oxygen, the most frequently encountered donor atom in the coordination chemistry of osmium. There is a large and growing body of work on the ammine, pyridine, ethylenediamine and porphyrin complexes, but the most popular and rapidly growing field of study at the present time is that of the polypyridyls , the 2,2 -bipyridyl, 1,10-phenanthroline and 2,2,2,6 - terpyridyl complexes of the metal. 

As ligands for osmium, ammonia and ethylenediamine (en 1,2-diaminoethane) would be expected to have broadly similar properties, and this is on the whole true — there are stable osmium(III) complexes such as [Os(en)3]3+, trans-[Os(en)2 X2]+ (X — Cl, Br) and [Os(en)Cl4], and more recently the tetravalent Os(en)X4 (X = Cl, Br, I) has been made. There is, however, an interesting chemistry of the l,2-ethanediaminato-(l —) and -(2 —) ligands with osmium in the higher IV, V and VI states, and another unusual feature is the existence of the hydride [OsH2(en)2f. ... 

There are however several substituted ethylenediamine complexes, the most unusual being the hydride [Os(en)2H2] " which can be obtained as a [ZnCl4] salt (by reaction of [0s02(en)2]Cl2 with zinc in HCl) or as a chloride. The salts are diamagnetic or almost so ( efr 0.22 BM at 298 K and O.IOBM at 183K for the [ZnCl4] salt). Although this is formally an osmium(IV) complex there seems to be no abnormality in the HNMR shift ((Sqsh = 15.4p.p.m.) the Os—H stretch lies at 2150 cm in the IR. ... 

---