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Iridacyclohexadienone complexes, a new class of unsaturated six-membered metallacycles, have been synthesized, and their reactions with acids have been investigated. Treatment (“iridabenzene” 1) with nitrous oxide produces the iridacyclohexadienone which upon stirring in diethyl ether solution slowly isomerizes to (1,2,5-η-2,4-dimethylpenta-1,3-dien-5-oyl)Ir(PMe3)3 (3). Treatment of 2 with methyl trifluoromethanesulfonate leads to removal of the metal hydride and production In acetone solution, 4 forms an equilibrium mixture with a ring-contracted iridacyclopentadiene Treatment of 4 with trimethylphosphine generates the tetrakis(trimethylphosphine)iridacyclohexadienone Iridacyclohexadienone 2 reacts with trifluoromethanesulfonic acid to produce the iridacyclopentene In contrast, treatment of iridacyclohexadienones 4 and 6 with trifluoromethanesulfonic acid leads to protonation of oxygen and production of the corresponding “iridaphenols” 8 and 10. When 4 is treated with trifluoroacetic acid, an iridaphenol...

A rare example of a stable metallabenzene complex has been synthesized in three high-yield steps from (Cl)Ir(PEt3)3. In the first step, (Cl)Ir(PEt3)3 is treated with potassium 2,4-dimethylpentadienide to produce the metallacyclohexadiene complex mer-CHC(Me)CHC(Me)CH2Ir(PEt3)3(H) (1b) via metal-centered CH bond activation. Treatment of 1b with methyl trifluoromethanesulfonate removes the hydride ligand, producing [CHC(Me)CHC(Me)CH2Ir(PEt3)3]+O3SCF3- (2). Finally, deprotonation of 2 with base yields the metallabenzene complex CHC(Me)CHC(Me)CHIr(PEt3)3 (3). The X-ray crystal structure of 3 shows the coordination geometry about iridium to be square pyramidal. The metallabenzene ring is nearly planar, and the ring π-bonding is delocalized. In the 1H NMR spectrum of 3, the ring protons (H1/H5 and H3) are shifted downfield, consistent with the presence of an aromatic ring current. Compound 3 reacts with a variety of small 2e- ligands under mild conditions to produce monosubstituted metallabenzenes, CHC(Me)CHC(Me...

The CS2 adduct of “iridabenzene” undergoes dimerization and cyclotrimerization reactions by linking subunits through thiocarbonyl sulfur centers. The cyclotrimerization product (compound 4) has been structurally characterized and contains a novel organometallic trithia-12-crown-3 ring system.