DECOMPOSITION REACTIONS OF THE DIALANE RADICAL-ANION [R(2)AL-ALR(2)]- IN DME .1. CRYSTAL-STRUCTURE OF R(2)AL(ME)OC(2)H(4)OMEK(DME) AND R(2)AL(OC(2)H(4)OME)(2)K (R=CH(SIME(3))(2))

Tetrakis[bis(trimethylsilyl)methyl]dialane(4) (1) reacts as recently reported with potassium in 1,2-dimethoxyethane (DME) to yield after purification the surprisingly stable radical monoanion [R(2)Al-AlR(2)](.-) [K(DME)(3)](+) (2) (R=CH(SiMe(3))(2)). With a longer reaction time of some days at room temperature and an excess of potassium, however, complete decomposition occurs under cleavage of ether molecules and formation of several new products. One of these compounds was identified as R(2)AlMe(OC(2)H(4)OMe)K(DME) (3) and characterized by a crystal structure determination. Two further derivatives were synthesized and their spectroscopic data compared to the decomposition products: R(2)Al(OC(2)H(4)OMe)(2)K (6), also characterized by crystal structure determination, and [R(2)AlMe(2)](-) [K(DME)(6)](+) (9), but due to the NMR characterization only 9 could be a component of the above-mentioned reaction mixture. In both aluminium alcoholates (3 and 6) the potassium ion is bound in a chelating manner by oxygen atoms of the aluminate unit, probably for this reason they are very soluble in non-polar solvents. In the solid state 3 polymerizes by intermolecular K...H3C-Al bridges forming one-dimensional chains along a crystallographic glide plane, and 6 forms dimers via K-O-K bridges and fourfold coordinated oxygen atoms.