Synthesis and characterization of arsacycloalkanes and their palladium and platinum complexes, and X-ray structure of [PdCl<inf>2</inf>(PhAsCH<inf>2</inf>CH<inf>2</inf>CH<inf>2</inf>CH <inf>2</inf>CH<inf>2</inf>)<inf>2</inf>]

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)n with MCl2(RCN)2 (M = Pd or Pt; R = Ph or 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(PhAsCH2CH2CH2CH 2CH2)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.