Synthesis and reactivity of [Ir(C₂H₄) ₂Tpm^Me2]PF₆ (Tpm^Me2 = Tris(3,5-dimethylpyrazolyl)methane): Comparison with the analogous Tp ^Me2 derivatives (Tp^Me2 = Hydrotris(3,5-dimethylpyrazolyl) borate)

A series of cationic Ir complexes of the neutral Tpm^Me2 ligand (Tpm^Me2 = tris(3,5-dimethylpyrazolyl)methane) have been investigated and compared, chemically and structurally, with the analogous derivatives of the monoanionic Tp^Me2 (Tp^Me2 = hydrotris(3,5- dimethylpyrazolyl)borate). The bis(ethene) compound [Ir(C₂H ₄)₂Tpm^Me2]PF₆ (1) undergoes olefinic C-H activation under very mild conditions to give first [Ir(H)(CH=CH ₂)(C₂H₄)-Tpm^Me2]⁺ (2) (all cationic species described have been isolated in the form of PF ₆- salts) and subsequently hydride-crotyl products derived from C-C coupling of the hydrocarbon ligands of 2. A different bond-forming reaction has been encountered during the solid-state thermal activation of 1 (suspended in C₆H₁₂), leading to the hydride-α,ω-butenyl derivative 4. X-ray studies on the latter compound show close structural analogies with related complexes of the Tp^Me2 ligand and, specifically, a striking similarity of the structural parameters of the IrTpm^Me2 and IrTp^Me2 moieties. Compound 4 reacts with hard donors, giving [Ir(CH₂CH₂-CH₂CH ₂)(L)Tpm^Me2]+ adducts (9; L = py, NCMe), whereas the soft donors PR₃ (R = Me, Et) and CN^- allow the isolation of complexes derived from the attack of the soft nucleophile at the internal coordinated olefinic carbon (complexes 10a-c). Hydrogenation of 1 under different experimental conditions permits the production of different hydride products, e.g. [Ir(H)₂(C₂H₄)Tpm ^Me2]⁺ (13) and [Ir(H)(C₂H₅)(C ₂H,)Tpm^Me2]⁺ (12). Carbene derivatives resulting from the regioselective double C-H bond activation of THF (compounds 11 and 16) have been produced using 4 and 13 as the reactants.