Iridium( III ) Silyl Alkyl and Iridacyclic Compounds Supported by 4,4′‐Di‐ tert ‐butyl‐2,2′‐bipyridyl

Treatment of IrCl 3 ⋅ x  H 2 O with one equivalent of 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridyl (dtbpy) in N , N ‐dimethylformamide (dmf) afforded [IrCl 3 (dmf)(dtbpy)] ( 1 ). Alkylation of 1 with Me 3 SiCH 2 MgCl resulted in CSi cleavage of the Me 3 SiCH 2 group and formation of the Ir III silyl dialkyl compound [Ir(CH 2 SiMe 3 )(dtbpy)(Me)(SiMe 3 )] ( 2 ), which reacted with t BuNC to afford [Ir( t BuNC)(CH 2 SiMe 3 )(dtbpy)(Me)(SiMe 3 )] ([ 2 ( t BuNC)]). Reaction of 2 with phenylacetylene afforded dimeric [{Ir(CCPh)(dtbpy)(SiMe 3 )} 2 (μ‐CCPh) 2 ] ( 3 ), in which the bridging PhCC − ligands are bound to Ir in a μ‐σ:π fashion. Alkylation of 1 with PhMe 2 CCH 2 MgCl afforded the cyclometalated compound [I r(dtbpy)(CH 2 CMe 2 C 6 H 4 )(2‐C 6 H 4 CMe 3 )] ( 4 ), which features an agostic interaction between the Ir center and the 2‐ tert ‐butylphenyl ligand. The cyclic voltammogram of 4 in CH 2 Cl 2 shows a reversible Ir IV –Ir III couple at about 0.02 V versus ferrocenium/ferrocene. Oxidation of 4 in CH 2 Cl 2 with silver triflate afforded an Ir IV species that exhibits an anisotropic electron paramagnetic resonance (EPR) signal in CH 2 Cl 2 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)(CH 2 CMe 2 Ph)Cl} 2 (μ‐Cl) 2 ] ( 5 ) and [Ir(dtbpy)(CH 2 CMe 2 Ph)(OTs) 2 ] ( 6 ), respectively. Reaction of 5 with Li[BEt 3 H] gave the cyclometalated complex [{I r(dtbpy)(CH 2 CMe 2 C 6 H 4 )} 2 (μ‐Cl) 2 ] ( 7 ). Reaction of 4 with tetracyanoethylene in refluxing toluene resulted in electrophilic substitution of the iridacycle by C 2 (CN) 3 with formation of [I r(dtbpy)(CH 2 CMe 2 C 6 H 3 {4‐C 2 (CN) 3 })(2‐C 6 H 4 CMe 3 )] ( 8 ). Reaction of 4 with diethyl maleate in refluxing toluene gave the iridafuran compound [I r(dtbpy)(CH 2 CMe 2 C 6 H 4 ){ κ 2 ( C , O )‐C(CO 2 Et)CH(CO 2 Et)}] ( 9 ). Treatment of 9 with 2,6‐dimethylphenyl isocyanide (xylNC) led to cleavage of the iridafuran ring and formation of [I r(dtbpy)(CH 2 CMe 2 C 6 H 4 ){C(CO 2 Et)CH(CO 2 Et)}(xylNC)] ( 10 ). Protonation of 9 with HBF 4 afforded the dinuclear neophyl complex [(Ir(dtbpy)(CH 2 CMe 2 Ph){ κ 2 ( C , O )‐C(CO 2 Et)CH(CO 2 Et)}) 2 ][BF 4 ] 2 ( 11 ). The solid‐state structures of complexes 2 – 5 and 8 – 11 have been determined.