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

Complexes [κ2-TpmMe2Ir(2,3,5,6-η-2-R-1,4-benzoquinone)Cl] (R = H, 1a; Cl, 1b; Ph, 1c; t Bu, 1d; TpmMe2 = tris(3,5-dimethylpyrazolyl)methane) and [κ3-TpmMe2Ir(2,3,5,6-η-1,4-benzoquinone)][BF4], 2a-BF 4 , have been prepared from the dimeric complex [Ir(μ-Cl)(coe)2]2 and structurally characterized. Compounds 1a–d were then thermally transformed to the corresponding iridacyclohexa-2,5-dien-4-one complexes [κ3-TpmMe2Ir(1,5-η-CHC(R)C(O)CHCH−)(CO)][BF4], 3-BF 4 , and for 1a the reactivity toward CO, phosphines, and HBF4–OEt2 was examined. Compounds 1a, 1b, 2a-BF 4 , 3a-BF 4 , 3b-BF 4 , carbonyl complex [κ3-TpmMe2Ir(2,3-η-1,4-benzoquinone)(CO)][Ir(CO)2Cl2], 4-[Ir(CO) 2 Cl 2 ], phosphine complexes [(PR3)2Ir(2,3,5,6-η-1,4-benzoquinone)Cl] (PR3 = PPh3, PPhMe2, PMe3), 5–7, and [(μ-PPh2CH2CH2PPh2)Ir(2,3,5,6-η-1,4-benzoquinone)Cl]2, 8, were characterized by X-ray diffraction analysis. Treatment of 1a with HBF4 led, through the intermediacy of [κ 2 -TpmMe2Ir(2-6-η-semiquinone)Cl][BF4], 9-BF 4 , to the isolation of hydroquinone [κ2-TpmMe2Ir(1-6-η-1,4-hydroquinone)Cl][BF4]2, 10-(BF 4 ) 2 , and treatment of 3-BF 4 with HSO3CF3 led to dicationic iridaphenol complexes [κ3-TpmMe2Ir(1,5-η-CHC(R)-C(OH)CH–CH)(CO)][SO3CF3]2 (R = H, t Bu), 11-(O 3 SCF 3 ) 2 .