SYNTHESIS OF DICARBOLLYL COMPLEXES OF THE ELEMENTS PHOSPHORUS AND ARSENIC - X-RAY STRUCTURAL-ANALYSIS OF CLAS[C2ME2B9H9]

The lithium salt Li2[Me2C2B9H9] reacts with the element(III) chlorides PCl3 and AsCl3 to yield the heterodicarbollyl compounds 1 and 2, respectively, of the type ClEl[Me2C2B9H9] (1, El = P; 2, El = As). Reaction of 1 and 2 with (i)PrMgCl leads to the corresponding isopropyl-derivatives (i)PrEl[Me2C2B9H9] (3, El = P; 4, El = As). 3 can also be obtained in low yields from the reaction of Li2[Me2C2B9H9] with (i)PrPCl2. 1 and 2 react with AlCl3 to give the adducts ClEl[Me2C2B9H9].AlCl3 (5, El = P; 6, El = As). Treatment of 1 with AgBF4 gives, under elimination of AgCl and BF3, the fluorinated analogon FP[Me2C2B9H9] (7). Comparison of the bonding situation in 1-7 with that in known isoelectronic cage-compounds of group 14 elements suggests a distorted icosahedral structure for 1-7, which has been proved in the case of 2 by an X-ray diffraction study.