Meyer's complex OsH2Cl2(P-i;Pr-3)(2) as a precursor for the preparation of new cyclopentadienylosmium compounds

The six-coordinate complex OsH2Cl2((PPr3)-Pr-1)(2) (1) reacts with cyclopentadienylthallium to give Os(eta(5)-C5H5)Cl((PPr3)-Pr-1)(2) (2). In methanol and acetone, 2 dissociates the chlorine ligand and the resulting metallic fragment is capable of activating a methyl C-H bond of a triisopropylphosphine to afford [OsH(eta(5)-C5H5){CH2CH(CH3)(PPr2)-Pr-i}((PPr3)-Pr-i)](+) (3), which can be isolated as the PF6 salt by addition of either NaPF6 or TIPF6. Treatment of a 1:10 mixture of 2 and NaBH4 in toluene with 1.0 mL of methanol affords OsH(eta(5)-C5H5)((PPr3)-Pr-i)(2) (4), which by protonation with HBF4 . OEt2 yields [OsH2(eta(5)-C5H5)((PPr3)-Pr-i)(2)]BF4 (5) In pentane, complex 2 reacts with trimethyl phosphite to give Os(eta(5)-C5H5)Cl{P(OMe)(3)}((PPr3)-Pr-i) (6). Similarly, the addition of methyl vinyl ketone and dimethyl acetylenedicarboxylate to toluene solutions of 2 produces the displacement of a phosphine ligand from 2 and the formation of Os(eta(5)-C5H5)Cl{eta(2)-CH2=CHC(O)CH3}((PPr3)-Pr-i) (7) and Os(eta(5)-C5H5)Cl{eta(2)-C(CO2CH3)=CCO2CH3}((PPr3)-Pr-i) (8), respectively. Complex 2 also reacts with ethyl diazoacetate to give Os(eta(5)-C5H5)Cl{eta(2)-(Z)-CH(CO2C2H5)=CHCO2C2H5}((PPr3)-Pr-i) (9) and with 1-ethynyl-1-cyclohexanol and 2-methyl3-butyn-2-ol to afford Os(eta(5)-C5H5)Cl{eta(2)-HC=C-C(OH)(CH2}(4)CH2)((PPr3)-Pr-i) (10) and Os(eta(5)C(5)H(5))Cl{eta(2)-HC=C-C(OH)(CH3)(2)}((PPr3)-Pr-i) (11) In toluene at 85 degrees C, complexes 10 and 11 evolve to the corresponding alkenylvinylidene derivatives Os(eta(5)-C5H5)Cl{=C=CH-C=CH(CH2)(3)CH2}((PPr3)-Pr-i) (12) and Os(eta(5)-C5H5)Cl{=C=CH-C(CH3)=CH2}((PPr3)-Pr-i) (13). Complex 13 can also be prepared by reaction of 2 with 2-methyl-1-buten-3-yne at room temperature. In this case, a sr-alkyne intermediate related to 10 and 11 was not detected even at -60 degrees C. However, the reaction of 2 with phenylacetylene initially gives Os(eta(5)-C5H5)Cl{eta(2)-HC=CPh}((PPr3)-Pr-i) (14), which subsequently evolves into Os(eta(5)-C5H5)Cl{=C=CHPh} ((PPr3)-Pr-i) (15). Protonation of 12, 13, and 15 with HBF4 afford the carbyne derivatives [Os(eta 5-C5H5)Cl{=C-CH=C(CH2)(4)CH2}((PPr3)-Pr-i)]BF4 (16), [Os(eta(5)-C5H5)Cl{=C-CH=C(CH3)(2)}((PPr3)-Pr-i)]BF4 (17), and [Os(eta(5)-C5H5)C-l(=C-CH2Ph)((PPr3)-Pr-i)]BF4 (18), respectively. The structure of 16 was determined by an X-ray investigation. The Os=C bond length is 1.756(8) Angstrom, while the OsC-C angle is 167.8(6)degrees.