[(μ‐C){Re(CO)₂(η‐C₅H₅)}₂]: A Surprisingly Simple Bimetallic Carbido Complex

Abstract

The bonding in the majority of binuclear m-carbido complexes may, to a first approximation, be described by one of two extreme canonical forms (A and B; Scheme 1). Symmetrical bimetallic complexes in which similar metal centers are bound to the central carbon atom are generally considered to adhere to a dimetallaallene-like bond localization (class A). [1,2] Most examples of this type of bonding have so far arisen from the reduction of Group 8 porphyrin complexes in the presence of CI 4 ; [1] this synthetic strategy ensures that both metal termini are identical, though examples do exist which involve disparate metals. [3] The alternative, and more commonly encountered class B "metallacarbyne" carbido complex involves essentially localized triple and single metal-carbon bonds that reflect the electronic requirements of the necessarily different metals. [4] A third class (C) of bridging carbido ligand has been observed, which might be described as polar covalent or dative in nature; however, at present few examples exist. [5] Despite the attempt above to delineate bonding profiles for bridging carbido complexes, it should be stressed that the scattered examples of such complexes still remain rare. Furthermore, no computational interrogation has appeared other than an early extended Hückel MO treatment by Hoffmann [5] of [(m-C){Fe(TPP)} 2 ] in which he predicted the viability of such a (diamagnetic) compound in advance of its discovery by Mansuy. [1] Given the importance of electronic communication between oxo bridges in all manner of [*] Dr.

Activation of CS2 and COS at a Rhodium(I) Germyl Complex: Generation of CS and Carbido Complexes

“…The rhodium–carbon bond lengths [Rh1–C1 1.788(4), Rh2–C1 = 1.798(4) Å] are in a typical range for Rh=C bond lengths when compared to carbene and vinylidene complexes . Iron carbido complexes show in contrast to 9 shorter metal–carbon bonds, whereas Rh, Re, Ru, and Nb complexes exhibit comparable values , ,. [20a], b The bond lengths and angles of the structurally related rhodium µ‐carbido complex trans , trans ‐[Rh 2 (µ‐C)(SBpin) 2 (PEt 3 ) 4 ] ( 10 ) are very similar .…”

“…of the highly reactive rhodium boryl complex [Rh(Bpin)(PEt 3 ) 3 ] ( 7 ) with CS 2 leading to the formation of a dinuclear rhodium µ‐carbido complex trans , trans ‐[Rh 2 (µ‐C)(SBpin) 2 (PEt 3 ) 4 ] ( 10 ) . Comparable fragmentation reactions breaking both C–S bonds in CS 2 are scarce . However, the stoichiometric conversion of 7 with CS 2 led to the formation of the thiocarbonyl complex [Rh(SBpin)(CS)(PEt 3 ) x ] ( x = 2, 3).…”

A Dirhoda‐Heterocyclic Carbene

“…In contrast, the simple μ‐carbido complex [Re 2 (μ‐C)(CO) 4 (η‐C 5 H 5 ) 2 ] has a negligible rotation barrier (ca. <16 kJ mol −1 ), which is attributed to the bonding being better described as a 2σ,4π 3‐center, 12‐electron system which is not significantly disrupted at any rotational angle . To further test the allene analogy, one might ask how the nature of the μ‐carbido center might respond to departure from linearity: Is there a μ‐carbido version of a bent allene?…”

Synthesis and characterization of redox active cyrhetrene–triazole click products

“…4 Cyclopentadienyl tricarbonyl rhenium (I), 1, is the next commercially available complex in the group 7 series (with the technetium analogue being radioactive), 5 that we wished to focus our attention upon. The applications of cyclopentadienyl rhenium(I) tricarbonyl, 1, have recently been reported in a wide array of research areas, including examples that have shown the photolysis of CO ligands allowing the coordination of new ligands (CS 2 , PPh 3 ), 6 utilizing the CO ligands of 1 as non-natural labels for probing protein electrostatics, 7 and modification of the cyclopentadienyl moiety to allow the formation of new cyrhetrene complexes with bidentate ligands, capable of forming new palladacycles. 8 Geiger has previously investigated the anodic behaviour of cyclopentadienyl tricarbonyl rhenium(I) 1, and has shown that the half-cell potential for the cyclopentadienyl tricarbonyl rhenium(I) redox couple +1/+2 is +1.16 V vs the ferrocene/ferricenium couple.…”

“…8 Geiger has previously investigated the anodic behaviour of cyclopentadienyl tricarbonyl rhenium(I) 1, and has shown that the half-cell potential for the cyclopentadienyl tricarbonyl rhenium(I) redox couple +1/+2 is +1.16 V vs the ferrocene/ferricenium couple. 9 Interestingly, this oxidation is only partly reversible in CH 2 Cl 2 (with [n-Bu 4 N][B(C 6 F 5 ) 4 ] as the supporting electrolyte), 10 due to the formation of the dimer, [Re 2 Cp 2 (CO) 6 ] 2+ , which shows an irreversible cathodic wave around ca 0.55 V vs the ferrocene/ferricenium couple. Furthermore, the use of [ReCp(CO) 3 ] + , 1 + , as a strong one-electron oxidant proved to be an excellent electron-transfer mediator in the case of coupling unactivated olefin substrates.…”