Synthesis of 2,2 ',5,5 '-tetraphenyl-1,1 '-diarsacalcocene and -strontocene

The metalation of H2As-SiiPr(3) with bis(tetrahydrofuran-O)calcium- and -st rontium bis[bis(trimethylsilyl)amide] yields tetrakis(tetrahydrofuran-O)cal cium- (1a) and -strontium bis(triisopropylsilylarsanide) (2a). These compou nds are in equilibrium with their dimers 1b (Ca) and 2b (Sr) by elimination of THE The addition of diphenylbutadiyne to a THF/toluene solution of 1 an d 2 gives bis (tetrahydrofuran-O) calcium- (3) and -strontium bis(2,5-diphe nylarsolide) (4). The proposed reaction mechanism explains the formation of the (iP(3)Si)(2)As- and 2,5-diphenyl-3,4-bis(phenylethynyl)arsolide anions based on an intermolecular H/SiiPr(3) exchange reaction. The latter anion was characterized by X-ray crystallography with the binuclear cation [(THF) (3)Ca{mu-As(H)SiiPr(3)}(3)Ca(THF)(3)](+) (5). The arsolide ligands of 3 and 4 are eta(5)-bonded to the metal centers, whereas 5 crystallizes as a solv ent-separated ion pair.