Isomerization of a cationic (η5-C5Me5)Ir(III) complex involving remote C–C and C–H bond formation

Abstract

The reactivity of an unsaturated, cationic (C 5 Me 5 )Ir(III) complex (2(Xyl) þ ) bearing the xylyl-substituted terphenyl phosphine PMe 2 Ar Xyl2 (Ar Xyl2 = C 6 H 3 -2,6-(C 6 H 3 -2,6-Me 2 ) 2 ) towards triethylamine (NEt 3 ) is studied and compared to our previous investigations based on the related complex 2(Dipp) þ containing the bulkier phosphine PMe 2 Ar Dipp2 (Ar Dipp2 = C 6 H 3 -2,6-(C 6 H 3 -2,6-i Pr 2 ) 2 ). Low-temperature multinuclear NMR studies support the formation of a C-C bond between the deprotonated C 5 Me 5 ligand and a flanking xylyl ring of the phosphine, which becomes dearomatized (complex 4(Xyl) þ ). Interestingly, this complex presents divergent reactivity relative to the bulkier diisopropylphenyl counterpart, undergoing formal addition of HCl to yield complex 5 (Xyl) þ , isomeric to the starting complex 2(Xyl) þ . These transformations are rationalized by means of Density Functional Theory (DFT) calculations.

Mechanism of Dihydrogen Splitting by An Apparent Bimetallic Frustrated Lewis Pair based on Ir(III)/Pt(0)

“…Such an unusual process was previously reported by our group upon treating 1 with triethylamine. [11] Nonetheless, the acidbase reaction with the Pt(0) base was slow at room temperature (t 1/2 � 2 h, 25 °C, see Figure S1) particularly when compared to the use of NEt 3 as the base (t 1/2 � 0.5 h, À 20 °C) and thus the study of the bimetallic FLP behavior of the system was still possible.…”

“…[8,9] Besides, the model heterolytic splitting of dihydrogen was achieved, which did not take place with the individual mononuclear components and for which our mechanistic investigations strongly supported a truly genuine frustrated pathway as opposed to a more traditional bimetallic route. [8,10] To further contribute to this emerging field, we have now examined the potential of compound [(η 5 -C 5 Me 5 )IrCl(PMe 2 Ar Dipp2 )] + (1; Ar Dipp2 =C 6 H 3 À 2,6-(C 6 H 3 À 2,6-i Pr 2 ) 2 ) [11] as a bulky Lewis acid fragment. This selection substantiates on prior results from our group on FLP-type systems constructed around its lighter congener rhodium, [12] as well as on the known electrophilic character of cationic Ir(III) complexes, particularly in low-coordination environments.…”

Unveiling the Latent Reactivity of Cp* Ligands (C5Me5–) toward Carbon Nucleophiles on an Iridium Complex

“…With this goal, we have selected our recently published terphenyl phosphine iridium compound 1 [(η 5 -C 5 Me 5 )­Ir­(Cl)­(PMe 2 Ar Dipp2 )]­[BAr F ] (Ar Dipp2 = C 6 H 3 –2,6-(C 6 H 3 –2,6- i Pr 2 ) 2 ) , to carry out a systematic study of its reactivity toward highly polarized organolithium and organomagnesium reagents. This platform is particularly attractive for these endeavors because (i) it presents a vacant coordination site at the electrophilic Ir­(III) center and a chloride ligand susceptible of participating in salt metathesis, yet both the ring and methyl groups of the Cp* can react preferentially toward nucleophiles and/or bases; (ii) the proven noninnocence of the Cp* ligand in this complex, encompassing deprotonation, reversible C–C bond formation and C–H bond breaking; (iii) its great stability toward cyclometallation; (iv) the possibility of accessing a bulkier analogue of Bergman’s complex [(η 5 -C 5 Me 5 )­Ir­(Me)­(PMe 3 )­(ClCH 2 Cl)] + ; , and (v) the in general prominent position of Cp*Ir complexes in the field of C–H bond activation. − …”