Organo-di-Metallic Compounds (or Reagents)

Table of Contents

1. Frontmatter

2. Organo-di-Lithio Reagents: Cooperative Effect and Synthetic Applications

   Shaoguang Zhang, Wen-Xiong Zhang, Zhenfeng Xi

   Abstract

   The development of organometallic reagents remains one of the most important frontiers in synthetic chemistry. In this review, we summarize our research on the structures, reactions, and synthetic applications of 1,4-dilithio-1,3-butadienes as organo-di-lithio reagents. The 1,4-dilithio-1,3-butadienes bearing a wide variety of substitution patterns on the butadienyl skeleton can be readily prepared in high efficiency. The configuration has been predicted and demonstrated to favor a double dilithium bridging structure in both solution and solid states. The two Li atoms are bridged by a butadiene moiety and are in close proximity. By taking advantage of this unique configuration, we have developed useful and interesting synthetic methodologies. Three types of reactions of 1,4-dilithio-1,3-butadienes have been developed and are discussed: intramolecular reaction, intermolecular reaction, and transmetallation. First, intramolecular reaction is introduced as a result of the intra-cooperative effect among the two C–Li moieties, the butadienyl bridge, and the substituents. A useful transformation from silylated 1,4-dilithio-1,3-butadienes to α-lithio siloles is described. Second, we discuss an intermolecular reaction that results from the inter-cooperative effect of the two C–Li moieties toward substrates. The intermolecular reactions are featured with formation of oxy-cyclopentadienyl dilithium via the reaction of di-lithio reagents with CO and formation of a series of N-heterocycles via the reaction of di-lithio reagents with nitriles. Third, we discuss transmetallation of di-lithio reagents with aluminum, copper, iron, zinc, or barium salts to generate diversified organo-di-metallic or metallacyclic compounds. The dimetallic 1,4-dilithio-1,3-butadienes and their transmetallated derivatives provide unique synthetic organometallic reagents that are different from monometallic reagents, both in terms of reactivity and in synthetic application. These organo-di-metallic reagents provide the access to interesting and useful compounds that are not available by other means, such as N-, O-, and Si-containing heterocycles, strained ring systems, metal-containing macrocycles, and metal complexes bearing new types of ligand.

3. Dynamics of the Lithium Amide/Alkyllithium Interactions: Mixed Dimers and Beyond

   Anne Harrison-Marchand, Nicolas Duguet, Gabriella Barozzino-Consiglio, Hassan Oulyadi, Jacques Maddaluno

   Abstract

   This review summarizes detailed investigations on the enantioselective nucleophilic addition of organolithiums onto prochiral electrophilic substrates, one of the simplest reaction meant to create a C–C bond, using dipolar bimetallic systems. Interestingly, these very popular and useful chemical transformations, even if taught at the undergraduate level, have remained underdeveloped when it comes to their enantioselective versions. The systems we present consist of a nucleophilic organolithium (NuLi) in strong dipolar interaction with a second lithiated entity bearing the source of asymmetry, i.e., a chiral lithium amide (CLA) derived from a 3-aminopyrrolidine (3APLi). Several 1:1 3APLi/NuLi noncovalent mixed aggregates are described and their relevance to the enantioselective process is discussed. Since the Curtin–Hammett principle forbids to correlate the complexes to the final ee's of the products, we have run complementary experiments of which results led us to propose the participation of an ephemeral, but more reactive, triptych aggregate.

4. Stable Geminal Dianions as Precursors for Gem-Diorganometallic and Carbene Complexes

   Marie Fustier-Boutignon, Nicolas Mézailles

   Abstract

   In this chapter, recent advances in the use of stable gem-dilithio compounds for the synthesis of carbene complexes or bimetallic complexes of groups 1–4, lanthanides, actinides and groups 13–14 are presented. This chemistry is based on the precise understanding of the factors that govern the stabilization of the gem-dilithio species. It is particularly noticeable that at least one high valent phosphorus moiety is needed to isolate the desired precursor in high yield and purity. For each family of complexes, the question of the nature of the metal–ligand interaction is addressed as well as their general reactivity.

5. FascinATES: Mixed-Metal Ate Compounds That Function Synergistically

   Robert E. Mulvey, Stuart D. Robertson

   Abstract

   Ate complexes are generally thought of as having a cationic and an anionic moiety, each containing a metal atom, though these moieties can be contacted or separated depending on the system. They have been known for over 150 years but yet only recently has it dawned on synthetic chemists that ates can bring about lots of improvements to the metalation reaction. Alkali-metal magnesiates, zincates and aluminates in particular have been successfully utilized in metal-hydrogen exchange reactions of challenging weakly acidic aromatic substrates. The fascination of these mixed-metal reagents lies in their ability to effect unique deprotonations at ambient temperatures without attacking functional groups on the aromatic scaffold where conventional organolithium reagents would require subambient temperatures to reduce such attacks, to direct metalation to the meta position of certain substrates where ortho or lateral deprotonation is more common and to strip more than one hydrogen atom from multi-C-H bonded compounds where lithiation methods would generally fail. Furthermore some of these superficially simple ate-metal-induced deprotonation reactions produce complex but beautiful host-guest macrocyclic architectures referred to as inverse crowns. Since magnesium, zinc and aluminium organic compounds cannot replicate these metalation reactions, these alkali-metal-mediated reactions are synergistic in origin. This article is not intended to be comprehensive but provides a representative selection of these fascinates in action, with emphasis on their synergistic nature. Reactions of the heteroleptic alkyl-amido magnesiate TMEDA·Na(TMP)(nBu)Mg(TMP) and zincate TMEDA·Na(TMP)(tBu)Zn(tBu) are featured prominently (TMP is 2,2,6,6-tetramethylpiperidide).

6. New Formulas for Zincate Chemistry: Synergistic Effect and Synthetic Applications of Hetero-bimetal Ate Complexes

   Masanobu Uchiyama, Chao Wang

   Abstract

   Organozincates are the oldest class of organometallic ate compounds in the history of chemistry. Their special molecular structures lead to synergetic operations which contribute to unique chemical properties. Therefore, these compounds have attracted considerable attention from organometallic chemists nowadays and also have been widely employed as an efficient synthetic tool towards various functional molecules. As a representative example, lithium zincates present many advantages such as easy preparation, adjustable reactivity/selectivity as well as diversified applicability. This chapter provides an overview of the research advances on lithium zincate, including observation history, general characterization, preparative methods, synthetic utilities as well as further applications.

7. Backmatter