Synthesis and Crystal Structure of Iridium-1,4-benzoquinone Complexes of Tris(3,5-dimethylpyrazolyl)methane Ligand: Decarbonylation, Protonation, and Substitution Reactions

Complexes [kappa(2)-Tpm(Me2)Ir(2,3,5,6-eta-2-R-1,4-benzoquinone)Cl] (R = H, 1a; Cl, 1b; Ph, 1c; Bu-t, 1d; Tpm(Me2) = tris(3,5-dimethylpyrazolyl)methane) and [kappa(3)-Tpm(Me2)Ir(2,3,5,6-eta-1,4-benzoquinone)][BF4], 2a-BF4, have been prepared from the dimeric complex [Ir(mu-Cl)(coe)(2)](2) and structurally characterized. Compounds 1a-d were then thermally transformed to the corresponding iridacyclohexa-2,5-dien-4-one complexes [kappa(3)-Tpm(Me2)Ir(1,5-eta-CH=C(R)C(O)CH=CH-)(CO)] [BF4], 3-BF4, and for la the reactivity toward CO, phosphines, and HBF4-OEt2 was examined. Compounds 1a, 1b, 2a-BF4, 3a-BF4, 3b-BF4, carbonyl complex [kappa(3)-Tpm(Me2)Ir(2,3-eta-1,4-benzoquinone)(CO)][Ir(CO)(2)Cl-2], 4-[Ir(CO)(2)Cl-2], phosphine complexes [(PR3)(2)Ir(2,3,5,eta-1,4-benzoquinone)Cl] (PR3 = PPh3, PPhMe2, PMe3), 5-7, and [(mu-PPh2CH2CH2PPh2)Ir(2,3,5,-eta-1,4-benzoquinone)Cl](2), 8, were characterized by X-ray diffraction analysis. Treatment of la with HBF4 led, through the intermediacy of [kappa(2)-Tpm(Me2)Ir(2-6-eta-semiquinone)Cl]BF4], 9-BF4, to the isolation of hydroquinone [kappa(2)-Tpm(Me2)Ir(1-6-eta-1,4-hydroquinone)Cl][BF4](2), 10-(BF4)(2), and treatment of 3-BF4 with HSO3CF3 led to dicationic iridaphenol complexes [kappa(3)-Tpm(Me2)Ir(1,5-eta-CH=C(R)-C(OH)=CH-CH=)(CO)][SO3CF3](2) (R = H, Bu-t), 11-(O3SCF3)(2).