Iridium(III) silyl alkyl and iridacyclic compounds supported by 4,4′-Di-tertbutyl-2,2′-bipyridyl

Treatment of IrCl₃·xH₂O with one equivalent of 4,4′-di-tertbutyl-2,2′-bipyridyl (dtbpy) in N,N-dimethylformamide (dmf) afforded [Ir-Cl₃(dmf)(dtbpy)] (1). Alkylation of 1 with Me ₃SiCH₂MgCl resulted in C-Si cleavage of the Me ₃SiCH₂ group and formation of the Ir^III silyl dialkyl compound [Ir(CH₂SiMe₃)(dtbpy)(Me)(Si-Me ₃)] (2), which reacted with tBuNC to afford [Ir(tBuNC)(CH ₂SiMe₃)-(dtbpy)(Me)(SiMe₃)] ([2(tBuNC)]). Reaction of 2 with phenylacetylene afforded dimeric [{Ir(O≡CPh)(dtbpy)(Si- Me₃)}₂(μ-C≡CPh)₂] (3), in which the bridging PhC≡C^- ligands are bound to Ir in a μ-σ:π fashion. Alkylation of 1 with PhMe₂CCH₂MgCl afforded the cyclometalated compound [Ir(dtbpy)-(CH₂CMe₂C ₆H₄)(2-C₆H₄CMe₃)] (4), which features an agostic interaction between the Ir center and the 2-tert-bu tylphenyl ligand. The cyclic voltammogram of 4 in CH₂Cl₂ shows a reversible Ir^IV_Ir^III couple at about 0.02 V versus ferrocenium/ferrocene. Oxidation of 4 in CH₂Cl₂ with silver triflate afforded an Ir^IV species that exhibits an anisotropic electron paramagnetic resonance (EPR) signal in CH ₂Cl₂ glass at 4 K with g_∥ = 2.430 and g_⊥=2.110. Protonation of 4 with HCl and p-toluenesulfonic acid (HOTs) afforded [(Ir(dtbpy)-(CH₂CMe₂Ph)Cl} ₂(μ-Cl)₂] (5) and [Ir-(dtbpy)(CH₂CMe ₂Ph)(OTs)₂] (6), respectively. Reaction of 5 with Li-[BEt₃H] gave the cyclometalated complex [{Ir(dtbpy)(CH ₂CMe₂C₆H₄)}₂-(μ-Cl) ₂] (7). Reaction of 4 with tetra cyanoethylene in refluxing toluene resulted in electrophilic substitution of the iridacycle by C ₂(CN)₃ with formation of [Ir(dtbpy)(CH₂CMe ₂C₆H₃{4-C₂-(CN)₃})(2- C₆H₄CMe₃)] (8). Reaction of 4 with diethyl maleate in refluxing toluene gave the iridafuran compound [Ir(dtbpy)(CH ₂CMe₂C₆H₄){k₂(C,O)-C- (CO₂Et)CH(CO₂Et)}] (9). Treatment of 9 with 2,6-dimethylphenyl isocyanide (xylNC) led to cleavage of the iridafuran ring and formation of [Ir(dtbpy)-(CH₂CMe₂C₆H ₄){C(CO₂Et)CH(CO₂-Et)}(xylNC)] (10). Protonation of 9 with HBF₄ afforded the dinuclear neophyl. complex [(Ir(dtbpy)(CH₂CMe₂-Ph){k²(C,O)-C(CO ₂Et)CH(CO₂Et)})2]-[BF₄]₂ (11). The solid-state structures of complexes 2-5 and 8-11 have been determined.