Butyllithium Deprotonation vs Alkali Metal Reduction of Cobalt Dicarbollide: A New Synthetic Route to C-Substituted Derivatives

Citations Over TimeTop 19% of 1997 papers

Abstract

Reduction of Cs[Co(1,2-C2B9H11)2] (Cs[I]) with 1 equiv of Na(Hg) amalgam or Cs metal forms the cobalt(II) dianion, [Co(1,2-C2B9H11)2]2- (II), which reverts to I upon exposure to 0.5 equiv of I2. The molecular structure of [Cs2(DME)4][Co(1,2-C2B9H11)2] shows the carbon atoms of dianion II occupy transoid rotational geometry about the cobalt center, consistent with isoelectronic nickel(III) bis(dicarbollide). Reaction of THF solutions of I with 1.0 and 2.0 equiv of n-butyllithium forms purple Cs[Co(LiC2B9H10)(C2B9H11)] (Cs[I-Li]) and blue Cs[Co(LiC2B9H10)2] (Cs[I-Li2]), respectively. Treating I-Li and I-Li2 with water causes reversion to I; reaction with D2O forms a dicarbollide C−D bond (IR: ν(CD/CH) = 2275/3040 cm-1). Mono- and dilithio(cobalt dicarbollide) react with alkyl halides (R−X) to form the corresponding alkyl(cobalt dicarbollide) complexes, [Co(RC2B9H10)(C2B9H11)]- and [Co(RC2B9H10)2]- (I-R and I-R2; R = CH3, C6H13). Alkylation of I-Li2 using methyl iodide gives a mixture of meso and rac isomers of [Co(1-Me-1,2-C2B9H10)2]- (I-1,1‘-Me2). In contrast, treating I-Li,Me (generated via deprotonation of I-Me) with methyl iodide forms [Co(1,2-Me2-1,2-C2B9H9)(C2B9H11)]- (I-1,2-Me2; 30%), plus meso- and rac-I-1,1‘-Me2 (70% total). The stereochemistry of alkylation is kinetically determined by the sites of deprotonation. Reaction of I-Li2 with 2 equiv of CH3OCH2CH2OCH2Cl (MEM-Cl) produces only the structurally characterized rac isomer of Cs[I-1,1‘-MEM2]. Crystal data for [Cs2(DME)4][Co(C2B9H11)2]: triclinic P1̄, a = 9.7930(10) Å, b = 10.1300(10) Å, c = 12.1010(10) Å, α = 101.13°, β = 98.16°, γ = 114.09°, V = 1042.1(2) Å3, Z = 1. Crystal data for Cs[Co(1-MEM-1,2-C2B9H10)2]: monoclinic P21/c, a = 11.5780(10) Å, b = 14.0880(10) Å, c = 16.998(2) Å, β = 96.21°, V = 2756.3(4) Å3, Z = 4.

Related Papers

• → Partially and fully deprotonated sulfuric acid in H2SO4(H2O) (n=6–9) clusters(2004)45 cited
• → Deprotonation of Iron Vinylidene Complexes Containing a dppe Ligand(2007)15 cited
• → Deprotonation and acidity characterization of biomass sugars: a first-principles study(2016)6 cited
• → Deprotonation of lipid-depleted bacteriorhodopsin.(1988)29 cited
• Deprotonation reactions of the non-rigid bis-(2,5-diamidopyrrole) induced by anions(2009)