Synthesis and reactivity of [Ir(C2H4)2TpmMe2]PF6 (TpmMe2 = tris(3,5-dimethylpyrazolyl)methane):: Comparison with the analogous TpMe2 derivatives (TpMe2 = 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(C2H4)(2)Tpm(Me2)]PF6 (1) undergoes olefinic C-H activation under very mild conditions to give first [Ir(H)(CH=CH2)(C2H4)Tpm(Me2)](+) (2) (all cationic species described have been isolated in the form of PF6- 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 I (suspended in C6H12), leading to the hydride-alpha,omega-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 lrTp(Me2) moieties. Compound 4 reacts with hard donors, giving [Ir(CH2CH2CH2CH2)(L)TPmMe2](+) 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 I under different experimental conditions permits the production of different hydride products, e.g. [Ir(H)(2)(C2H4)Tpm(Me2)](+) (13) and [Ir(H)(C2H5)(C2H4)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.