Syntheses and structures of cyclopentadienyl arsenic (III) compounds Part III: Tetraisopropylcyclopentadienyl arsenic (III) dibromide and tetraisopropylcyclopentadienyl arsenic (III) diiodide (TipCpAsBr(2), TipCpAsI(2))

摘要

1,2,3,4-Tetraisopropylcyclopenta-2,4-dien-1-yl arsenic (III) dihalides, viz. TipCpAsX(2) (1 X = Br, 2 X = I), have been prepared by direct metathesis reaction between the corresponding arsenic (III) trihalides with one equivalent of TipCpK at low temperature in good yields. Alternatively, 2 has been prepared via halogen exchange reaction between TipCpAsCl(2) (3) and KI. New compounds have been characterised by spectroscopic methods (H-1, (CNMR)-C-13, EI-MS) and elemental analyses. The crystal structures of 1 and 2 have been determined by X-ray diffraction methods. The AsX2-moiety in 1 and 2 occupies an allylic position neighbouring to an isopropyl substituent. The arsenic fragment is sigma-bound to the cyclopentadienyl ligand, indicating remarkable pi-interactions with the diene part of the cyclopentadienyl ring. [References: 32]