Electron‐Reservoir Complexes [Fe^ICp(arene)] as Selective Initiators for a Novel Electron Transfer Chain Catalyzed Reaction: General Synthesis of Fulvalene‐Bridged Homo‐ and Heterodinuclear Zwitterions

Abstract

Within only five minutes at 20°C bimetallic fulvalene complexes 1 undergo intramolecular disproportionation in the presence of PMe3 or P(OMe)3 when electron‐reservoir complexes of the type [FeICp(arene)] serve as catalysts. MI = Mo, W, Fe, Ru; M2 = Mo, W; n = 2, 3; m = 3; arene = C6H6, C6Me6. The heterodinuclear complexes react with regioselectivity.

Zwitterionic Organometallates

“…[{η 1 :η 6 -C 6 H 5 (TiCp 2 Cl)}Cr(CO) 3 ]), [92] zwitterionic bimetallic complexes of Group 6 metals are found in the fulvalene series. Homodinuclear complexes, in which the metals exhibit different CO vs. phosphane substitution patterns, can be prepared by several methods (A, [93] B, [94] or C [95] ) from (fulvalene)Mo 2 (CO) 6 and basic phosphanes. After metalmetal bond cleavage, the steric repulsion between the metal centers overrides the electrostatic attraction and results in a 180°rotation of the cyclopentadienyl metal moieties, which, in turn, leads to a trans arrangement of the opposite charges with respect to the cyclopentadienyl plane.…”

On the Roles of Electron Transfer in Catalysis by Nanoclusters and Nanoparticles

“…[111,112] One of the properties of electron-reservoir systems is their ability to initiate electron-transfer chain (ETC) catalytic reactions, [113] because these reactions require that the catalyst be robust enough in the two oxidation states involved in the ETC process (for instance E and E À in Scheme 4). [59,113] The reaction follows an efficient ETC mechanism (i. e. with a sufficiently high turnover number) if the radical anion of the product D *À is more electron rich than A *À the radical anion of the substrate, in order to design an exergonic redox step closing the ETC cycle (otherwise better try an ETC reaction using an oxidizing initiator). [48,52,59,113] This situation is encountered with the prototypical atomically precise nanocluster [Au 25 (SH 2 CH 2 Ph) 18 ], provided the counter cation involved in the ETC process is bulky enough to inhibit kinetic instability.…”

“…[59,113] The reaction follows an efficient ETC mechanism (i. e. with a sufficiently high turnover number) if the radical anion of the product D *À is more electron rich than A *À the radical anion of the substrate, in order to design an exergonic redox step closing the ETC cycle (otherwise better try an ETC reaction using an oxidizing initiator). [48,52,59,113] This situation is encountered with the prototypical atomically precise nanocluster [Au 25 (SH 2 CH 2 Ph) 18 ], provided the counter cation involved in the ETC process is bulky enough to inhibit kinetic instability. [86] This interesting reaction reported by Zhu's group is the reduction of ortho-nitrobenzonitrile by NaBH 4 to ortho-aminobenzamide catalyzed by the ETC initiator [Au 25 (SCH 2 CH 2 Ph) 18 ] À , TOA + , and during which the substrate Scheme 3.…”

“…In this way, the electron transfer process can be accompanied or followed by and combined with successive steps for efficient stoichiometric and catalytic complex reactions. In this way, NCs and NPs behave as electron reservoirs, a concept defined forty years ago with late first-row transition-metal sandwiches and fullerenes [55][56][57] that also withstand monoelectronic oxidation and reduction without breakdown and present redox-catalytic [58] and electrocatalytic properties [59,60] likewise applicable to metal clusters and NPs. These steps may be successive electron transfers ("cascades") [60][61][62] and atom transfers eventually composed of proton-coupled electron transfers.…”

Electron-reservoir complexes and other redox-robust reagents: functions and applications

“…57 Substitution of CO by the second PMe 3 ligand can be only achieved using the more powerful reductant [Fe I (Z 5 -C 5 Me 5 )(Z 6 -C 6 Me 6 )] as a catalyst (Scheme 8). 58 In the cluster [Ru 3 (CO) 12 ], substitution of carbonyl by phosphane ligands leads to mixtures when it is carried out thermally. Using ETC catalysis, CO substitution by phosphanes was shown by Bruce's group to be very selective and clean.…”