Carbonylmetallates—A Special Family of Nucleophiles in Aromatic and Vinylic Substitution Reactions

Abstract

Carbonylmetallates, [M(CO)(n)L](-), anionic transition-metal carbonyl complexes, represent a large family of metal-centered nucleophiles, and studying carbonylmetallates allows us to understand the differences in the behavior of the metal-centered complexes versus heteroatom-based nucleophiles. The mechanisms of carbonylmetallate reactions with aryl- and alkenyl halides have been examined by employing radical and, especially, carbanion trapping techniques. Carbonylmetallates show a marked preference for halogenophilic attack, and nucleophilic substitution with carbonylmetallates is often not a direct process, but proceeds through the initial attack at halogen with subsequent coupling of carbanion and HalM(CO)(n)L intermediates. Factors governing the competition between the halogenophilic and more common "carbophilic" reaction pathways, as well as the means of predicting the actual course of reaction are discussed. The review also considers other aspects of carbonylmetallate reactivity, including ion-pairing effects, radical-mediated nucleophilic substitution pathways, and the carbonylmetallate nucleophilicity scale in the reactions with π-electrophiles.

Reduction and Rearrangement of a Boron(I) Carbonyl Complex

“…The two‐electron reduction of transition metal (TM) carbonyl complexes, [TM(CO) n ], generally proceeds with loss of CO to the corresponding [TM(CO) n −1 ] 2− dianions (Figure 1 a), and/or anionic metal carbonyl clusters [1–4] . Studied extensively throughout the last century, [TM(CO) n −1 ] 2− dianions are highly air‐sensitive nucleophiles [5, 6] with a rich reactivity toward organometallic, inorganic, and organic compounds [7–12] . Our group and others have used [TM(CO) n −1 ] 2− precursors (TM=Cr, Mo, W, n =6; M=Fe, n =5) for the synthesis of terminal borylene complexes of the form [(OC) n TM=BR] (R=anionic substituent) [13–17] in which the BR ligand is isolobal with CO.…”

“…[1][2][3][4] Studied extensively throughout the last century, [TM(CO)n-1] 2dianions are highly air-sensitive nucleophiles [5,6] with a rich reactivity toward organometallic, inorganic and organic compounds. [7][8][9][10][11][12] Our group and others have used [TM(CO)n-1] 2precursors (TM = Cr, Mo, W, n = 6; M = Fe, n = 5) for the synthesis of terminal borylene complexes of the form [(OC)nTM=BR] (R = anionic substituent), [13][14][15][16][17] in which the BR ligand is isolobal with CO. The two-electron reduction of aryl-and aminoborylene complexes of this type proceeds quite distinctly, however, from that of [TM(CO)n], resulting in double B-CO coupling and the release of an iminoborane dimer, respectively (Figure 1b).…”

Multicomponent Coupling Reaction of Perfluoroarenes with 1,3-Butadiene and Aryl Grignard Reagents Promoted by an Anionic Ni(II) Complex

“…An anionic organoplatinum complex (Zeise’s salt) was prepared almost two centuries ago as the first example of an organometallic complex . Despite such a long history of anionic complexes of transition metals, they are not often employed in synthetic reactions as catalysts, − except for the case of Cu . This is in contrast to the well-developed and still growing use of neutral or cationic transition metal catalysts in organic synthesis.…”

Lithium Hexaphenylrhodate(III) and -Iridate(III): Structure in the Solid State and in Solution

“…When 2 Ir was reacted with CO 2 gas (1 atm) in THF-d 8 at room temperature for 24 h, no reaction occurred, and 2 Ir remained intact. In addition, CO, which is a good π-accepting ligand and is often used for preparing ate-complexes, 26 did not react with 2 Ir . These results imply that the dissociation of PhLi from 2 Ir does not proceed at ambient temperatures.…”