Structures and Reactions of Organic ate‐Complexes

Abstract

SummaryIn this brief review, we have attempted to point up the importance of chemical equilibria in structural inorganic chemistry and to show how the kind and yield of various molecules may be treated quantitatively. Because of the importance of kinetic control in organic chemistry and because the chemistry of carbon compounds is by far the most advanced branch of general and descriptive chemistry, preparative inorganic chemists have often overemphasized the value of reactionmechanism theory to their studies and have thereby neglected the powerful quantitative approach of thermodynamics which may be used in equilibrated systems. The general theorems for treating in terms of small molecular segments the multitude of equilibria present in families of compounds have been surveyed superficially with the hope that the interested reader will turn to the original papers for details. In these days of high-speed computers, not only physical-inorganic chemists, but also those interested solely in preparative work can advantageously employ the theoretical ideas discussed above. Future Developments a) T h e o r yAtomic-interaction theories are being developed for correlation and prediction of the deviations from randomness in the equilibria involving chains. Work is also under way on the theoretical basis of ring-chain equilibria and the time needed to reach equilibrium in various systems. The concept of order of environment within molecules can be extended to the interpretation of what might be called atomically additive properties, such as density, refractive index: or bulk magnetic susceptibility. In addition, we are studying several examples of the effect of solution nonideality on deviations from randomness in equilibria. b) AnalysisNew and improved analytical techniques for assaying molecules in mixtures are surely to be expected in a reasonably near future. In particular, nuclear magnetic resonance spectrometers of very high resolution will become available with improvements in field-strength uniformity of superconducting magnets. These should allow one to see molecules in considerably greater depth than is possible today, as well as to extend practical high-resolution NMR to samples having the natural abundance of chemically interesting nuclei such as 13C, 15N, 29Si, 77Se, 111Cd or 113Cd, 119Sn, 125Te, 195Pt, 199Hg, and 207Pb, all of which have spin 112. Moreover, with very high field strengths, it will be possible to measure much more rapid exchange rates and to observe uncoalesced resonances under conditions where either exchange or quadrupole broadening now makes the spectra difficult and sometimes impossible to interpret. Another way of increasing the range of elements that can be studied by NMR is to use isotopic enrichment of those magnetically suitable nuclei which are naturally present in low abundance (e.g. 29Si).

Structural Organozinc Chemistry

“…This phenomenon had already been recognized by Frankland and has plagued chemists ever since 25 . When it was recognized that 'ate' compounds often have enhanced reactivity and selectivity profiles compared to their parent organometallic compounds 26,27 , systematic studies of synthetic applications and structural features of organozincates started. Nowadays, organozincates and other organozinc reagents are valuable synthetic tools in organic chemistry which have had comparable impact in organic synthesis as the corresponding organocopper and -cuprate reagents 28 .…”

Main Group Lewis Acids in Frustrated Lewis Pair Chemistry: Beyond Electrophilic Boranes

“…In this review, we focus our attention on the studies that have exploited less conventional main-group Lewis acids in the context of FLP chemistry. 4 ] could be used as a metal-free catalyst for the hydrogenation of imines and enamines. 54 In a manner similar to B(C 6 F 5 ) 3 -catalyzed imine hydrogenation, the borenium cation and the imine act as an FLP to heterolytically cleave H 2 , generating an NHCborane adduct and an iminium cation.…”

“…An unusual carbon-based Lewis acid, reported by our group, 80 4 ]. This species acts as a carbon-based Lewis acid at the ortho and para positions of the η 6 -arene.…”

Reaction of conjugated enones with divinylcopperlithium tri-n-butylphosphine complex. A new preparation of γ,δ-unsaturated ketones

“…The discovery of lithium dimethylcuprate, (CH3),CuLi, by Gilman and coworkers (1) has sparked renewed interest in the properties and reactions of ate complexes (2). Reagents of the type R,CuLi, or analogs in which an alkyl (or aryl) copper reagent is stabilized by complexation with phosphorus-or sulfur-containing ligands possess considerable synthetic value for the construction of new carbon-carbon bonds (3)(4)(5)(6).…”

“…The reagent, formulated (merely for convenience), as (CH,=CH),CuLiP(n-C4H,),, is easily and rapidly prepared by the addition of two equivalents of a solution of vinyllithium in tetrahydrofuran (THF) to one equivalent of tetra- (9) dissolved in T H F at -78" under n i t r~g e n .~ Addition of a conjugated enone to the resultant deeply colored mixture gives, after suitable pro-'Holder of a 1967 Science Scholarship. 'We intend no structural implications by employing this designation; rather, this formulation is used for sin~plicity and by consideration of stoichiometry and analogy (2,5).…”