Deprotonation Induced Ligand-to-Metal Electron Transfer: Synthesis of a Mixed-Valence Rh(−I,I) Dinuclear Compound and Its Reaction with Dioxygen

Abstract

Treatment of bis(2-picolyl)amine (bpa) with [{Rh(nbd)(mu-OMe)}2] leads to the unexpected and unique redox asymmetric dinuclear Rh-I,Rh+I complex [{Rh(nbd)}2(bpa-2H)] (2) with a pi-coordinating imine bound to a tetrahedral low valent rhodate(-I). Mono-oxygenation of the deprotonated bpa ligand in 2 by O2 leads to the mononuclear carboxamido complex [Rh(nbd)(bpam-H)] (3) (bpam = N-(2-picolyl)picolinamide). The second O atom of O2 ends up as a hydroxo fragment in [{Rh(nbd)(mu-OH)}2].

Influence of N‐Substitution on the Oxidation of 2‐Pyridylmethylamines with Bis(trimethylsilyl)amides of Iron(III) – Synthesis of Heteroleptic Iron(II) 2‐Pyridylmethylamides

“…-(dipicolylamide) and (L ox2 ) 0 [N-picolyl(2-pyridylmethylidene)-amine] were found in the vicinity of rhodium(I) [26] and iridium(I) starting from metalated dipicolylamine. [27] In order to further elucidate the influence of the Nbound substituent, we investigated the reaction of ironbased metalation reagents with N-diphenylphosphanyl-picolylamine [28] which offers an additional Lewis base.…”

Ligand Oxidation of a Deprotonated Bis(picolyl)amine IrI(cod) Complex

“…It seems that increased Ir!C=C p-back donation to the cod double bonds upon deprotonation of the bpa fragment is at least in part responsible for the ease of these reactions. Deprotonation of [1] + to 2 leads to dissociation of one of the pyridine arms, and thus the average Ir!C=C p-back donation hardly changes (average olefinic 13 C chemical shifts: [1] + : d = 56.6 ppm; 2: d = 59.0 ppm). However, the two cod olefins in 2 are non-equivalent, and not exchanging on the NMR timescale, with substantially lower field 13 C chemical shifts for the olefinic carbons trans to the anionic amido fragment (d = 53.5 ppm) compared with the olefinic carbons trans to the neutral Py fragment (d = 64.4 ppm).…”

“…Deprotonation of [1] + to 2 leads to dissociation of one of the pyridine arms, and thus the average Ir!C=C p-back donation hardly changes (average olefinic 13 C chemical shifts: [1] + : d = 56.6 ppm; 2: d = 59.0 ppm). However, the two cod olefins in 2 are non-equivalent, and not exchanging on the NMR timescale, with substantially lower field 13 C chemical shifts for the olefinic carbons trans to the anionic amido fragment (d = 53.5 ppm) compared with the olefinic carbons trans to the neutral Py fragment (d = 64.4 ppm). After the second deprotonation in formation of [3] À , the two olefinic fragments are shifted further upfield, but now have almost identical chemical shifts (d = 48.0 and 46.0 ppm).…”

“…[13] In marked contrast, methylene deprotonated (picolyl)phosphane-type ligand (late) TM complexes have been reported, [14] and interestingly the resulting anionic ligands are not just "spectator" ligands; they directly participate in (catalytic) heterolytic H À H and C À H bond-breaking reactions. [15] Radical ligands are more reactive, and thus comparable cooperative substrate activation by the metal and a radical ligand should allow faster reactions and/or conversion of less reactive substrates.…”

Developing Synthetic Approaches with Non‐Innocent Metalloligands: Easy Access to IrI/Pd0 and IrI/Pd0/IrI Cores

“…[13] Considering the importance of palladium in catalysis, [14] and the very few studies on palladium chemistry incorporating non-innocent ligands, [15] we decide to explore the potential reduction of Pd II by the {bpa 2H} 2 ligand. Herein we report our success in developing this idea, which in addition opens new ways to prepare unprecedented heteronuclear Ir I /Pd 0 and Ir I /Pd 0 /Ir I complexes with an unusuallycoordinated -iminopyridine ligand.…”