Synthesis and spectroscopic and structural investigations of the 2,3,4,5-tetraethylarsolides and -stibolides of the alkali metals sodium, potassium, rubidium, and cesium

The reduction of 1-chloro-2,3,4,5-tetraethylarsole and -stibole with the alkali metals sodium, potassium, rubidium, and cesium in 1,2-dimethoxyethane (DME) or TMEDA yields the corresponding 2,3,4,5-tetraethylarsolides (L)M-AsC4Et4 [(L)M = (TMEDA)Na 1a, (DME)(2/3)K 1b, (DME)Rb 1c, and (DME)Cs 1d] and 2,3,4,5-tetraethylstibolides (L)M-SbC4Et4 [(L)M = (DME)(1/2)Na 2a, (DME)Rb 2c, and (DME)Cs 2d]. These compounds are characterized by NMR spectroscopy and X-ray structure determinations. Whereas la crystallizes with discrete dimeric molecules, all other compounds form one-dimensional polymers. With the exception of the sodium derivatives, all polymers show exclusively eta(5)-coordination of the arsolide and stibolide substituents. For the sodium compounds 1a and 1b also Na-As and Na-Sb sigma-bonds, respectively, are observed.