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)2/3K
1b, (DME)Rb 1c, and (DME)Cs 1d] and 2,3,4,5-tetraethylstibolides (L)M-SbC4Et4 [(L)M =
(DME)1/2Na 2a, (DME)Rb 2c, and (DME)Cs 2d]. These compounds are characterized by NMR
spectroscopy and X-ray structure determinations. Whereas 1a crystallizes with discrete
dimeric molecules, all other compounds form one-dimensional polymers. With the exception
of the sodium derivatives, all polymers show exclusively η5-coordination of the arsolide and
stibolide substituents. For the sodium compounds 1a and 1b also Na−As and Na−Sb σ-bonds,
respectively, are observed.