Alkali Metal Chlorine and Bromine Carbenoids: Their Thermal Stability and Structural Properties

Abstract

Abstract:The synthesis and structures of aseries of M/X carbenoids of the type [Ph 2 P(S)] 2 CMX with M = Li, Na, and K and X = Cl and Br are reported,a mongstt he first isolated Na/Br and K/Br carbenoids.N MR spectroscopic as well as crystallographic studies showed distinct differences between the lithiumc arbenoids and their heavierc ongeners. In the solid state, all carbenoids showedn od irectmetal-carbon interaction,b ut an interaction between the metal and the halogen atom. This contact is only very weak in the case of the Li/Br carbenoid, but much more pronounced in the corresponding potassium and sodium compounds. Nevertheless, these interactions did not significantly influence the stability of the carbenoids by weakening the CÀXb onda nd facilitating the MX elimination. As such all compounds were found to be stable up to approximately 60 8Ci ns olution. Hence, MÀXi nteractions-albeitb eing an essential feature fort he structure formation of carbenoids-arenot the only criterion determining the stabilityo fs uch compounds.I nt he present systems, the stabilization by the thiophosphinoyl moieties is more important than the metal/halogen combination.

Adsorption and Visualization of Solvated Na/Br Carbenoids on Ag(111)

“…In the liquid and the solid phases, three THF solvent molecules stabilize the Na/Br carbenoid . Our gas-phase calculations confirm the stability of a trisolvated Na/Br carbenoid with the three THF molecules bonding to the Na atom (cf.…”

“…The solvation of carbenoids significantly affects their reactivity and selectivity in organic reactions . Studying carbenoids at the nanoscale, which is feasible when adsorbed on surfaces, could deliver a better understanding of the solvent effects on their reactivity and selectivity.…”

“…13 Nevertheless, they are particularly interesting organometallic reagents since, unlike simple carbanions, they exhibit nucleophilic and electrophilic properties. 12 The solvation of carbenoids significantly affects their reactivity and selectivity in organic reactions. 12 Studying carbenoids at the nanoscale, which is feasible when adsorbed on surfaces, could deliver a better understanding of the solvent effects on their reactivity and selectivity.…”

Synthesis, Characterization, and Trapping of a Cyclic Diborylcarbene, an Electrophilic Carbene

“…Chlorine-substituted diborylcarbenoid 2 Cl has a 1D polymeric structure in the solid state bridged by potassium cations coordinated by one THF molecule (Figure b and Figure S78). The C–Cl bond [1.780(3) Å] is the shortest among the ones reported for K/Cl-type carbenoids; − however, it still lies in the typical single-bond length range. The theoretical calculation on 2 Cl showed only a negligible elongation of the C–Cl bond compared to its protonated form (1.804 Å for 2 Cl , 1.800 Å for the protonated form), in contrast to the case of fluorine analogue 2 F .…”

“…In 1958, Simmons and Smith invented a synthetic carbene equivalent, carbenoid, wherein the carbon atom was bound to both a metal cation and a (pseudo)­halogen (Figure b, left) . Since the use of zinc carbenoid I-CH 2 -ZnI for cyclopropanation, carbenoid has been widely used as a stable synthetic equivalent to carbene. − Efforts have also been devoted to isolation and characterization of carbenoids. − In addition to stable Li, Mg, and Zn carbenoids, recently, Gessner’s research group successfully isolated heavier alkali-metal (Na, K) carbenoids. − …”