The complex trans -[Os(H)(CH 3 CN)(dppe) 2 ]BF 4 (2) is prepared from the known complex trans -[Os(η 2 -H 2 )(H)(dppe) 2 ]BF 4 (1), dppe = Ph 2 PCH 2 CH 2 PPh 2, by substitution of the η 2 -H 2 ligand with CH 3 CN. 2 was identified as a potential precursor for a highly acidic and stable η 2 -H 2 complex on the basis of its electrochemical potential E 1/2 (Os III /Os II ). The stable complex trans -[Os(η 2 -H 2 )(CH 3 CN)(dppe) 2 ](BF 4 ) 2 (3) is formed when 2 is protonated with excess HBF 4 ·Et 2 O in anhydrous CH 2 Cl 2 . The p K a of 3 is estimated to be −2 because it is partially deprotonated by Et 2 O. This makes it the most acidic, stable dihydrogen complex to be fully characterized. Its properties are compared to the known complex trans -[Os(η 2 -H 2 )(CH 3 CN)(en) 2 ](CF 3 SO 3 ) 2 (5), en = H 2 NCH 2 CH 2 NH 2, to illustrate the influence of the chelating ligand (π-acidic dppe versus σ-basic en), and to the complexes trans -[Os(η 2 -H 2 )(X)(dppe) 2 ]PF 6, X = H (1), Cl (4), and Br (6), to illustrate the influence of the trans ligand on the characteristic properties of the η 2 -H 2 ligand. The ligand field strength of X is an important factor. The structures of 2 and 3a,b ( 3 crystallizes in 2 forms) were determined by X-ray diffraction. In 3a the hydrogen atoms of the η 2 -H 2 ligand were isotropically refined, resulting in an H−H distance of 0.9(1) Å. In 3b there is residual electron density associated with the η 2 -H 2 ligand, but the hydrogen atoms were not located. There is a close dihydrogen−fluorine contact of approximately 2.4 Å in 3a .
No takes yet. Share an insight, caveat, or question.
Schlaf et al. (1996) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: