Alkali Metals: Organometallic Chemistry

Abstract

Organolithium complexes, such as the organomagnesium Grignard reagents, are important reactants in organic synthesis. The similarity in structure, bonding, and reactivity of organolithium and ‐magnesium compounds exemplifies the common chemistry exhibited by representative elements that appear in the same diagonal in the periodic table. Although much debate exists over the degree of covalency within lithium–carbon bonding interactions—the presence of some covalent characters in Li–C bonds of alkyllithium compounds is widely accepted. The bonding interactions within organoalkali metal complexes of the heavier alkali metals are generally considered to be strongly electrostatic or ionic in nature. This is supported by a large collection of evidence, consisting primarily of solution NMR data, single‐crystal X‐ray analyses, and gas‐phase computational studies. Many of the organolithium compounds are soluble in hydrocarbons, but organometallic compounds of the heavier Group 1 metals generally require more polar media to dissolve. In general, the reactivity of the alkali metals and the reactivity of the organometallic compounds of these metals increase as the group descends. Although organoalkali metal compounds are similar to Grignard reagents, they are more reactive and are both air‐ and moisture‐sensitive and sometimes pyrophoric. In addition, organoalkali metal compounds will react as Brønsted bases with protic reagents. Specific details regarding the synthesis, reactivity, and structures of various types of organoalkali metal compounds are discussed.

Sulfinyl-aminotroponiminates: alkali- (Li, Na, K) and heavy-metal (Bi) complexes

“…(2-K) were prepared in moderate to good yields (42-74%) by reaction of 5-( phenylsulfinyl)aminotroponimine 1 19 with the respective alkali-metal base LiCH 2 (SiMe 3 ) 2 or M-HMDS (M = Na or K, HMDS = N(SiMe 3 ) 2 , see Scheme 1). 42,43 Compounds 2-M show unexpected solubility properties: contrary to common trends in alkali metal chemistry, 44 the lithium species shows a lower solubility than the higher homologues (e.g. : 2-Li precipitates from THF, while 2-Na and 2-K are THFsoluble).…”

The quest for organo-alkali metal monomers: unscrambling the structure–reactivity relationship

“…From a bonding perspective, the M–C bond gets more polar (can be superficially understood as the metals’ electronegativity gets smaller) and ionic and hence, more reactive. 1,9,10 The steric and electronic properties of the carbanion substituent affects the level of aggregation as well. Electron donating groups destabilise the carbanion, whereas electron withdrawing groups help to stabilise it.…”

Reaction of electrons trapped in cryogenic matrices with benzophenone

“…[ 18,19 ] These radical anions are usually short‐lived reactive intermediates that are synthetically useful in a variety of organic and organometallic reactions as strong reductants. [ 20–22 ]…”

“…[18,19] These radical anions are usually short-lived reactive intermediates that are synthetically useful in a variety of organic and organometallic reactions as strong reductants. [20][21][22] Benzophenone in its lowest excited state plays an important role in a variety of photochemical reactions and is known to be highly electrophilic. Benzophenone derivatives with low singlet-triplet energy gaps are used in organic light-emitting diodes.…”