Synthesis and characterization of arsacycloalkanes and their palladium and platinum complexes,and X‐ray structure of [PdCl2(PhAsCH2CH2CH2CH2CH2)2]

Reactions of PhAsCl₂ with BrMg(CH₂)_nMgBr (n = 4 or 5) in THF gave phenylarsacycloalkanes as colourless oily liquids which could be distilled under vacuum. Treatment of PhAs(CH₂)_n­with MCl₂(RCN)₂ (M = Pd or Pt; R = Ph­or Me) afforded mononuclear complexes, [MCl₂{PhAs(CH₂)_n}₂]. Reactions with [Pt₂Cl₂(μ‐Cl)₂(PEt₃)₂] gave mixed‐ligand complexes, [PtCl₂(PEt₃){PhAs(CH₂)_n]. The palladium complexes adopt a trans geometry whereas the platinum complexes exist in a cis configuration. The crystal and molecular structure of [PdCl₂(PhAsCH₂CH₂CH₂CH₂CH₂)₂] was determined by X‐ray diffraction methods. The molecule consists of a square‐planar palladium atom with trans chlorides and trans arsa ligands. The six‐membered ‘AsC₅′ ring adopts a chair conformation. Copyright © 1999 John Wiley & Sons, Ltd.