Reactions of a Dicarbenium Fulvalenyl Complex with Aromatic Nucleophiles and Synthesis of (μ-Alkyne)(fulvalenyl)tetracarbonyldimolybdenum Compounds:  A Structure−Reactivity Relationship

Abstract

The compound [FvMo2(CO)4(μ-η3:η3-CH2C⋮CCH2)][BF4]2 (3) reacts with weak nucleophiles to give the related carbenium complexes [FvMo2(CO)4(μ-η2:η3-CH2C⋮CCH2Nu)][BF4] (Nu = −C6H4OH, −C6H4OMe), where attack occurs exclusively on one carbenium center (−CH2 +). Subsequent treatment by NaBH4 reduces the second carbenium center (−CH2 +) to yield the disubstituted alkyne fulvalenyl adducts. The difference in reactivity between 3 and the analogous dicarbenium Cp system [Cp2Mo2(CO)4(μ-η3:η3-CH2C⋮CCH2)][BF4]2 is attributed to the fulvalene effect.

Transformation of Dimetallacyclopentanes into β-Substituted Enamine-, Alkylidene-, and α,β-Unsaturated Acyl-Bridged Diiron Complexes

“…Trimethyl phosphite was purchased from Strem Chemical Co. and used without further purification. The diiron complex [Fe 2 (CO) 6 (μ-PPh 2 ){μ−η 1 :η 2 -C(H)CCH 2 }] was prepared as previously described 10a…”

“…Since the discovery of rational, high-yield synthetic routes to binuclear allenyl complexes, which include the addition of diazoalkanes to μ−η 1 :η 2 -acetylides, S N 2‘ attack of a dimetalate at a propargyl halide, and template synthesis, a detailed examination of their reaction chemistry has revealed more disparate and varied reactivity patterns than their mononuclear counterparts. In this regard, examples of unusual coupling reactions (Scheme ), the addition of nucleophiles to C α , C β , and C γ (Scheme ), the formation of acyl−allenyl complexes via migratory insertion/elimination of CO into a μ−η 1 :η 2 -allenyl ligand (Scheme ), and the generation of diiron coordinated β,γ-unsaturated amides, esters, and ketones 14 (eq 5) all suggest that the σ−η-coordinated allenyl fragment offers immense potential as a building block for the synthesis of a wide range of unsaturated organic molecules, provided these products can be liberated from the metal center. Methods currently under investigation include protonation, oxidative cleavage by Ce(IV), and intramolecular oxidative-addition−reductive-elimination pathways.…”

Cobalt-Complexed Conjugated Diyne Salts: A Family of Rigid Masked Dielectrophiles. Syntheses, Structures, and Double Nucleophilic Substitutions

“…Our interest in “M 2 L 6 modifications” of propargyl alcohols, or more specifically, 2-butyne-1,4-diol where {M 2 L 6 = Co 2 (CO) 6 }, led us recently to prepare a family of metal-stabilized masked 1,4- and 1,6-dicarbenium complexes. The chemistry of metal-stabilized carbenium ions has been well studied in the literature by us and several authors; however, less is known about related dicarbenium complexes . Pursuing our research program, we focused our investigations on the isolation and stabilization of dicarbenium ions possessing one or more conjugated cobalt − alkyne units .…”