Substituted Cyclopentadienyl Osmium Complexes from the Reactions of OsH3Cl(PPh3)3 with Fulvenes and Cyclopentadienes

Two methodologies were developed for the preparation of half-sandwich osmium complexes with the general formula (η5-cyclopentadienyl)OsCl(PPh3)2. The first approach involves the reactions of OsH3Cl(PPh3)3 with cyclopentadienes. Treatment of OsH3Cl(PPh3)3 with cyclopentadienes gives (η5-cyclopentadienyl)OsCl(PPh3)2 via C−H oxidative addition of cyclopentadienes followed by reductive elimination of hydrogen. The methodology has enabled us to synthesize a series of half-sandwich osmium complexes containing Cp, Cp*, indenyl, and C5Me4R (R = H, Et, n-Pr). The second approach involves the insertion reactions of OsH3Cl(PPh3)3 with fulvenes. Treatment of OsH3Cl(PPh3)3 with C6-substituted fulvenes produces cleanly monosubstituted cyclopentadienyl osmium complexes (η5-C5H4CHRR′)OsCl(PPh3)2 (R = H, R′ = p-C6H4CH3, p-C6H4OCH3, CMe3; R = R′ = Ph) via hydride transfer to the electrophilic exocyclic carbon of fulvenes. Under similar conditions, OsH3Cl(PPh3)3 reacts with C6-monosubstituted 1,2,3,4-tetramethylfulvenes to give pentasubstituted cyclopentadienyl osmium complexes (η5-C5Me4CH2R)OsCl(PPh3)2 (R = p-C6H4CH3, p-C6H4OCH3, pyrenyl).