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; tBu, 1d; TpmMe2 =
tris­(3,5-dimethylpyrazolyl)­methane) and [κ3-TpmMe2Ir­(2,3,5,6-η-1,4-benzoquinone)]­[BF4], 2a-BF4, 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-BF4, and for 1a the reactivity toward CO, phosphines, and HBF4–OEt2 was examined. Compounds 1a, 1b, 2a-BF4, 3a-BF4, 3b-BF4, carbonyl complex [κ3-TpmMe2Ir­(2,3-η-1,4-benzoquinone)­(CO)]­[Ir­(CO)2Cl2], 4-[Ir­(CO)2Cl2], 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 [κ2-TpmMe2Ir­(2-6-η-semiquinone)­Cl]­[BF4], 9-BF4, to the isolation of hydroquinone [κ2-TpmMe2Ir­(1-6-η-1,4-hydroquinone)­Cl]­[BF4]2, 10-(BF4)2, and treatment of 3-BF4 with HSO3CF3 led
to dicationic iridaphenol complexes [κ3-TpmMe2Ir­(1,5-η-CHC­(R)-C­(OH)CH–CH)­(CO)]­[SO3CF3]2 (R = H, tBu), 11-(O3SCF3)2.