Influence of the Group 14 Element on the Deprotonation of OsH(η⁵-C₅H₅)(C⋮CPh)(EPh₃)(PⁱPr₃) (E = Si, Ge):  Two Different Organometallic Chemistries

The complexes OsH(η⁵-C₅H₅)Cl(EPh₃)(PⁱPr₃) (E = Si (1), Ge (2)) react with lithium phenylacetylide to give the hydride−alkynyl derivatives OsH(η⁵-C₅H₅)(C⋮CPh)(EPh₃)(PⁱPr₃) (E = Si (3), Ge (4)). The structure of 4 has been determined by X-ray diffraction analysis. The distribution of ligands around the osmium atom can be described as a four-legged piano-stool geometry with the monodentate ligands lying in the four-membered face. Treatment of 3 with n-butyllithium and the subsequent addition of methanol, methanol-d₄, and methyl iodide to the resulting solution leads to OsH(η⁵-C₅H₄SiPh₃){CC(H)Ph}(PⁱPr₃) (5), OsH(η⁵-C₅H₄SiPh₃){CC(D)Ph}(PⁱPr₃) (5-d), and (6), respectively. Similarly to 3, the reaction of the perdeuterated cyclopentadienyl complex OsH(η⁵-C₅D₅)(C⋮CPh)(SiPh₃)(PⁱPr₃) (3-d₅) with n-butyllithium and methanol gives OsH(η⁵-C₅D₄SiPh₃){CC(H)Ph}(PⁱPr₃) (5-d₄). The structure of 6 has been also determined by X-ray diffraction analysis. In this case, the distribution of ligands around the osmium atom can be described as a piano-stool geometry with the metalated carbon atom transoid to the phosphine and cisoid to the hydride. Complex 5 reacts with HBF₄ to give the hydride−carbyne derivative [OsH(η⁵-C₅H₄SiPh₃)(⋮CCH₂Ph)(PⁱPr₃)]BF₄ (7), which is stable. Initially, the addition of HBF₄ to diethyl ether solutions of 6 also leads to a hydride−carbyne complex, [OsH(η⁵-C₅H₄SiPh₃){⋮CCH(CH₃)Ph}(PⁱPr₃)]BF₄ (8). However, in solution, complex 8 evolves into the hydride−allyl compound [OsH(η⁵-C₅H₄SiPh₃){η³-CH₂C(Ph)CH₂}(PⁱPr₃)]BF₄ (9). The structure of 9 has been determined by X-ray diffraction analysis. The distribution of ligands around the osmium atom can be described as a piano-stool geometry, where the allyl ligand occupies two cisoid positions. Treatment of 4 with n-butyllithium and the subsequent addition of methanol, methanol-d₄, and methyl iodide to the resulting solution gives the germyl−vinylidene complexes Os(η⁵-C₅H₅)(GePh₃){CC(H)Ph}(PⁱPr₃) (10), Os(η⁵-C₅H₄D)(GePh₃){CC(D)Ph}(PⁱPr₃) (10-d₂), and Os(η⁵-C₅H₄CH₃)(GePh₃){CC(CH₃)Ph}(PⁱPr₃) (11), respectively. The protonation of 10 and 11 with HBF₄ affords the corresponding carbyne derivatives [Os(η⁵-C₅H₅)(GePh₃)(⋮CCH₂Ph)(PⁱPr₃)]BF₄ (12) and [Os(η⁵-C₅H₄CH₃)(GePh₃){⋮CCH(CH₃)Ph}(PⁱPr₃)]BF₄ (13).