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

The use of [Cp''2 Zr(η1:1 -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 [CpR NiBr]2 (CpR =CpBn (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 En unit, a degradation as well as aggregation can be observed. Thus, the prismane derivatives [(Cp'''Ni)2 (μ,η3:3 -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 [(CpR Ni)3 {Ni(μ-Br)}(μ3 -E)4 ]2 (CpR =Cp''': 6 a (E=P), 6 b (E=As), CpR =CpBn : 8 a (E=P), 8 b (E=As)) can be isolated. Here, a stepwise transfer of En units is possible, with a cyclo-E4 2- ligand being introduced and unprecedented triple-decker compounds of the type [{(CpR Ni)3 Ni(μ3 -E)4 }2 (μ,η4:4 -E'4 )] (CpR =CpBn , Cp'''; E/E'=P, As) are obtained.