The use of chloroalkyldichloroarsines in hybrid ligand synthesis. The preparation of but-3-enylbis(3-dimethylarsinopropyl)arsine and 3-dimethylarsinopropylbis(but-3-enyl)arsine,and their reaction with nickel(II) salts to form pentacoordinate complexes. Novel nickel(II)—olefin bonds

Routes have been developed to the hitherto unobtainable arsine-olefin ligands (CH₂CHCH₂CH₂)_nAs(CH₂CH₂CH₂AsMe₂)_3-n (n = 1, tasol, but-3-enylbis(3-dimethylarsinopropyl)arsine; n = 2, dasdol, 3-dimethylarsinopropylbis(but-3-enyl)arsine) by making use of the difference in reactivity between the ClC and AsCl bonds in the precursor Cl(CH₂)_mAsCl₂ (m = 2,3) molecules. Thus, the triarsine obtained by reaction of 2-chloroethyldichloroarsine with the Grignard reagent of 3-chloropropyldimethylarsine yields 2-chloroethylbis(3-dimethylarsinopropyl)arsine, from which tasol is obtainable by subsequent reaction with either the Grignard reagent of vinyl bromide or, preferably, with vinyllithium. Similarly, 3-chloropropyldichloroarsine reacts with the Grignard reagent of 4-chlorobut-1-ene to form 3-chloropropylbis(but-3-enyl)arsine which, on reaction with sodium dimethylarsenide yields dasdol. The tasol ligand reacts with nickel(II) salts to form NiX(tasol)]⁺ (X = Cl, Br) and NiI₂(tasol)], the former are trigonal bipyramidal and contain a nickel(II)—olefin bond, and the latter are square pyramidal containing a NiI₂As₃] coordination sphere. In addition, tasol forms a number of polynuclear complexes with nickel(II). The dasdol ligand acts as a bidentate arsine to form only NiX(dasdol)₂)]⁺ The formation of novel nickel(II)—olefin bonds in the NiX(tasol)]⁺ cations is discussed.