A Modular Strategy for Expanding Electron-Sink Capacity in Noncanonical Cluster Assemblies

Abstract

A modular synthetic strategy is described whereby organometallic complexes exhibiting considerable electron-sink capacity may be assembled by using only a few simple molecular components. The Fe 2 (PPh 2 ) 2 (CO) 5 fragment was selected as a common electroactive component and was assembled around aromatic cores bearing one, two, or three isocyanide functional groups, with the resultant complexes possessing electron-sink capacities of two, four, and six electrons, respectively. The latter complex is noteworthy in that its electron-sink capacity was found to rival that of large multinuclear clusters (e.g., [Ni 32 C 6 (CO) 36 ] 6– and [Ni 38 Pt 6 (CO) 48 ] 6– ), which are often considered as benchmarks of electron-sink behavior. Moreover, the modular assembly bearing three Fe 2 (PPh 2 ) 2 (CO) 5 fragments was observed to undergo reduction to a hexaanionic state over a potential window of about −1.4 to −2.1 V (vs Fc/Fc + ), the relatively compressed range being attributed to potential inversions operative during the addition of the second, fourth, and sixth electrons. Such complexes may be designated noncanonical clusters because they exhibit redox properties similar to those of large multinuclear clusters yet lack the extensive network of metal–metal bonds and the condensed metallic cores that typify the latter.

Synthetic investigations of the diisocyanide‐bridged Cp*‐cobalt rectangles

“…This enables effective electron communication and facilitates electron transfer within the metal–ligand–metal frameworks. Recent studies have focused on the electronic communication properties of organometallic complexes containing 1,4‐diisocyanobenzene bridges, highlighting their unique capacity to act as electron sinks [23]. In our investigation, we employed cyclic voltammetry (CV) to examine the separately electrochemical reduction of complex 2 , 3 , and 4 in acetonitrile.…”

Aza-Diphosphido-Bridged Di-Iron Complexes Related to the [FeFe]-Hydrogenases

“…In recent decades, the chemistry of carbonyl iron complexes has undergone intensive development within the field of biomimicry. Alongside numerous reports on carbonyl dithiolato-bridged di-iron complexes structurally close to the active site of [FeFe]hydrogenases (H-cluster) (Scheme 1a) [1-5], phosphido-bridged analogues (Scheme 1b,c) were studied in order to compare the electronic and stereochemical effects of the replacement of the µ-S 2 R bridge with the µ-PR 2 group on the reactivity and redox properties of such carbonyl di-iron systems [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The chemistry of bis-phosphido-bridged di-iron complexes of general formula [Fe 2 (CO) 6 (µ-PR 2 ) 2 ] and linked-diphosphido [Fe 2 (CO) 6 (µ-(PR) 2 R')] dates back much earlier .…”