Alkali-metal alkylberyllium alkoxides

Abstract

Three series of alkali-metal t-butoxyberyllate complexes are described, including MBe(OBut)3(M = Li, Na, K, Rb, or Cs), [MEtBe(OBut)2]2(M = Li or Na), and [MEt2Be(OBut)]2(M = Na or K). The series MBe(OBut)3 is formed from MOBut and Be(OBut)2, from Na2BeH4 and ButOH, or from K and Be(OBut)2 in ButOH. The Li and Rb complexes crystallise from benzene though the others are insoluble in that solvent. The Li and Na complexes dissolve in bis(2-methoxyethyl) ether yielding hexane-soluble 1:1 monomeric co-ordination complexes. The LiBe(OSiMe3)3 and LiBe(OBut)2(OCEtMe2) complexes are dimeric in benzene solution. In contrast, LiBe(OCEt3)3 exists in a dimer-monomer equilibrium in benzene solution. The series [MEtBe(OBut)2]2 are conveniently prepared from EtLi and Be(OBut)2 or from NaOBut and EtBeOBut. Replacement of the ethyl group in the former with a t-butyl group yields dimeric [LiBut(OBut)2]2, though Li2But2Be(OBut)2 has a degree of association of between 1 and 2 in benzene solution. Complexes of the type [MEt2Be(OBut)]2 are readily prepared from equimolar mixtures of NaOBut or KOBut with Et2Be, though Rb2Et3Be2(OBut)3 is isolated from equimolar portions of RbOBut and Et2Be. Sodium diethyl t-butoxyberyllate reacts with toluene or mesitylene giving red K5Et3Be3(OBut)4(PhCH2)4 or orange diamagnetic K3Et2Be2(OBut)2(mesityl)2, respectively. The rubidium complex gives red Rb5Et3Be3(OBut)2(mesityl)4 on reaction with mesitylene. Sparingly benzene-soluble LiButBe(NMe2)2 is also described.