Formation and Properties of the Trichloroberyllate Ion

Abstract

The activation of C-Cl bonds in dichloromethane and chloroform was observed by BeCl in the presence of PMe and PCy. This leads to the formation of [MePCHCl]Cl and [CyPCHCl][BeCl]. The latter compound is the first example of a tricoordinated beryllium species with nonbulky ligands and proof of the existence and stability of the long-predicted [BeCl] ion. In analogy to the isoelectronic BCl, the trichloroberyllate anion exhibits Lewis acidic behavior toward electron-pair donors and was probed for the electronic and steric influence of the Lewis base. [BeCl] can also act as a chloride ion donor or acceptor, leading to the formation of neutral phosphane adducts to BeCl and [BeCl]. The existing equilibria between these species were investigated and showed high chloride mobility.

Recent Contributions to the Coordination Chemistry of Beryllium

“…Thisi sa lso evident from dynamic exchange equilibria betweent hese species in solution at ambient temperature. [56] Similar-even though more complex-equilibria exist between different azidoberyllate speciesi ns olution( Scheme 17). Te traazidoberyllates 137 can be synthesized from Be(N 3 ) 2 and two equivalents of organic azide salts.…”

“…The decomposition of dinuclear complex 51 in chloroform proceeds through the same route, though significantly faster.H owever,i nt his case no simple phosphonium chloride is formed butacorresponding trichloroberyllate. [56] The properties of the latter anion are discussed further below.…”

“…Until the year 2018, no homoleptic beryllium carboxylates were known.T he first example of this fundamentall igand Scheme7.CÀCl bond activation by beryllium-phosphine complexes (a:X= H, R = Me;b:X= Cl, R = Cy). [56] Figure 6. Beryllium chloride coordinated by crowne thers.…”

“…[109] Hexachlorodiberyllate 128 b dissociates in solution to the threefold-coordinated monomeric trichloroberyllate 62 b. [56] The analogousr eactions with tricyclohexyl(dichloromethyl)phosphonium chloride [110] lead to the respective tetrachloroberyllate 129 a andt richloroberyllate 62 a.T he latter is also present in the solid state, which allowed for the first crystallographic examination of at hreefold-coor- Figure 14. Beryllium complex dications.…”

“…[16,90,97,106,107] dinated beryllium speciesw ithouts terically very demanding ligands. [56] The fact that only slight changesi nt he counterion induce two different anionic forms-monomeric trichloroberyllate or dimerich exachlorodiberyllate-indicates that there are only marginal differences in the energy of these two ions.…”