Fischer carbene complexes remain favourite targets, and vehicles for new discoveries

Abstract

Exciting new variations in Fischer-type carbene complex composition and reactivity have been realised by following or modifying well-established synthetic approaches such as metal carbonyl functionalization and modification of existing carbene ligands. The formation of targeted complexes for organic synthesis, carbene-containing chelates, and polynuclear carbene complexes, by employing 'click chemistry', warrants discussion. Transmetallation and α,α-dehydrogenation of ethers and amines have come into their own as viable synthetic methods to access carbene complexes with unique properties and activities. Successful mediation of carbene complex formation with pincer ligands has proved its worth. Quantum chemistry has become essential for supporting or initiating mechanistic proposals, but heuristic approaches such as invoking the vinylology principle to describe substituted phenylcarbene complexes are still valuable in the interpretation of bonding properties and the classification of complex types. Electrochemical studies now also constitute a powerful part of the experimental characterization tool kit.

Constructing Organometallic Architectures from Aminoalkylidyne Diiron Complexes

“…According to the fact that the sequential nucleophile/electrophile addition to a coordinated isocyanide represents a classical strategy to access aminoalkylidene ligands, complexes 20 were converted into the alkynyl‐alkylidene 22 by methylation (Scheme a) . The reactivity with nucleophiles of one compound of the series 22 was explored, revealing to be substantially localized at the alkynyl function (an example of structure growing is shown in Scheme b).…”

Synthesis and XPS characterization of Si-supported chromium(0) Fischer aminocarbene complexes

“…Fischer-type carbene complexes (FCCs) have been the interest of many synthetic, 1 structural, 2 electrochemical, electronic, theoretical and spectroscopic studies. [3][4][5][6][7][8][9][10]11,12 In particular, Fischer carbene complexes of chromium have found application in a variety of different organic transformations, 13 cyclization reactions, 14 metal-templated conversions, 15 benzannulation reactions 16 and are particularly useful in the activation of organic molecules. 13 The applicable mechanisms in the syntheses and reaction mechanisms of FCCs in organic reactions are typically explored by quantum chemical calculations 17 and in addition to yielding organic products, substrate-carbene interactions afford numerous novel coordination complexes.…”

Synthesis and properties of mono- and dimetal Fischer multicarbene complexes derived from thiophene and thieno[2,3-b]thiophene

“…This means that 3 co-crystallized with 5 in a ratio of 38 : 62 and was confirmed by peak integration in the 1 H NMR spectrum of 5. The mono-and biscarbene complexes (1)(2)(3)(4)(5) all have the ethoxy substituent on the same side of the adjacent thiophene sulfur atom, while the orientation of the ethoxy substituents in 6-15 are determined by the rigidity of the chelate rings. In the molecular structures, one linear pair of the cis-pentacarbonyl ligands usually bend away from the carbene.…”

“…After absorbing the reaction mixture on silica, it was dry loaded onto a silica gel column. The respective products (1)(2)(3)(4) were separated by column chromatography using gradient elution with hexane and DCM. [2,3-b]thiophene in 20.0 mL of THF was treated with 1.40 mL (2.2 mmol) of n-BuLi at −78°C and stirred for 30 minutes.…”

“…1 Literature on the synthesis and reactivity of Fischer carbene complexes often reports a series of similar substrates to prepare classical monocarbene complexes, but the approach neglects the possibilities that a single substrate has to offer in multiple carbene complex synthesis. Although N-heterocyclic carbene complexes have found extensive application in multiple carbene functionalities on single substrates, 2 a similar strategy has not been developed in the chemistry of classic heteroatom-stabilized Fischer carbene complex-types.…”