E4 Transfer (E=P, As) to Ni Complexes

Abstract

The use of [Cp''₂ Zr(η^1:1 -E₄ )] (E=P (1 a), As (1 b), Cp''=1,3-di-tert-butyl-cyclopentadienyl) as phosphorus or arsenic source, respectively, gives access to novel stable polypnictogen transition metal complexes at ambient temperatures. The reaction of 1 a/1 b with [Cp^R NiBr]₂ (Cp^R =Cp^Bn (1,2,3,4,5-pentabenzyl-cyclopentadienyl), Cp''' (1,2,4-tri-tert-butyl-cyclopentadienyl)) was studied, to yield novel complexes depending on steric effects and stoichiometric ratios. Besides the transfer of the complete E_n unit, a degradation as well as aggregation can be observed. Thus, the prismane derivatives [(Cp'''Ni)₂ (μ,η^3:3 -E₄ )] (2 a (E=P); 2 b (E=As)) or the arsenic containing cubane [(Cp'''Ni)₃ (μ₃ -As)(As₄ )] (5) are formed. Furthermore, the bromine bridged cubanes of the type [(Cp^R Ni)₃ {Ni(μ-Br)}(μ₃ -E)₄ ]₂ (Cp^R =Cp''': 6 a (E=P), 6 b (E=As), Cp^R =Cp^Bn : 8 a (E=P), 8 b (E=As)) can be isolated. Here, a stepwise transfer of E_n units is possible, with a cyclo-E₄ ^2- ligand being introduced and unprecedented triple-decker compounds of the type [{(Cp^R Ni)₃ Ni(μ₃ -E)₄ }₂ (μ,η^4:4 -E'₄ )] (Cp^R =Cp^Bn , Cp'''; E/E'=P, As) are obtained.

Keywords: arsenic; nickel; phosphorus; polypnictogen complexes; transfer reactions.