Synthesis and crystal structure of a novel aluminum±¯uorine±potassium compound [Me 3 Si) 3 C) 2 Al 2 m-F)F 4 K] x with a supramolecular chain Hagen Hatop, Marcus Schiefer, Herbert W. Roesky * , Hans-Georg Schmidt, Mathias Noltemeyer Institut fu Èr Anorganische Chemie der Universita Èt Go Èttingen, Tammannstrasse 4, D-37077 Go Èttingen, Germany Received 29 May 2001; accepted 31 August 2001 Abstract [Me 3 Si) 3 C) 2 Al 2 m-F)F 4 K] x 6) is a new organoaluminum alkali ¯uoride with an in®nite potassium zig-zag chain. The compound is accessible either by reaction of [Me 3 Si) 3 CAlF 2 ] 3 with KF or by treating [Me 3 Si) 3 CAlF 2 ] 3 with potassium metal. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Aluminum; Fluorine; Alkali ions; Chain; Supramolecular 1. Introduction There are several known compositions of [Me 3 Si) 3- CAlF 2 ] 3 with alkali ¯uorides [1±5]. The cations are structure directing to yield cubic arrays like [MMe 3 Si) 3 CAlF 3 - THF)] 4 M Li 1) [1], Na 2) [2]) and unusual aggre- gates [Agtoluene) 3 ] [{Me 3 Si) 3 C) 2 Al 2 m-F)F 4 } 2 Li] 3) [3] Scheme 1), [Me 3 Si) 3 C) 4 Al 4 K 2 m-F) 2 F 8 THF) 4 ]4) [4], and [{LiMe 3 Si) 3 CAlF 3 THF)} 3 LiFTHF)] 5) [5] Scheme 2). They contain the chelating [Me 3 Si) 3 CAlF 3 ] 1, 2, and 5) or [Me 3 Si) 3 CAlF 2 m-F)F 2 AlCSiMe 3 ) 3 ] 3 and 4) anion. It is known that organoaluminum di¯uorides form various aggregates in the presence of THF due to the LewisbasecharacterofthissolventandtheLewisaciditysite of the aluminum. Consequently different structural arrange- ments were isolated when these systems were treated with THF [6]. Compound 4 for example contains four molecules of coordinated THF. Therefore, we were interested in the THF free analogous compound. The result is a compound of composition [Me 3 Si) 3 C) 2 Al 2 m-F)F 4 K] x 6) containing a potassium zig-zag chain with a complete different coordina- tion sphere at the potassium atom compared to 4. 2. Results and discussion Compound 6 was prepared from [Me 3 Si) 3 CAlF 2 ] 3 with water free KF in toluene under re¯ux in moderate yield. At room temperature compound 6 is only slightly soluble in toluene. Suitable crystals for X-ray structural analysis were obtained from hot toluene. An alternative method for the preparation of 6 is the treatment of [Me 3 Si) 3 CAlF 2 ] 3 with metallic potassium under re¯ux in toluene. The by-product of this reaction could not be characterized. The yield of 6 is slightly higher than the latter method Scheme 3). The structure of 6 consists of an endless potassium zig-zag chain with a K±K distance of 4.78007) A Ê which is slightly longer than that in potassium metal avg. 4.54 A Ê ) [7] Fig. 1). The potassium atoms are four-fold coordinated by terminal ¯uorine atoms of the [Me 3 Si) 3 CAlF 2 m- F)F 2 AlCSiMe 3 ) 3 ] anions Fig. 2). The K±F bond length ranges from 2.599017) to 2.658718) A Ê which is slightly shorter or comparable to that in KF 2.664 A Ê ) [7] or in the range of those in 4 2.610±2.860 A Ê ). Within the four term- inal ¯uorine atoms of 6 F4) is weakly coordinating to a second potassium atom with a distance of 3.1472) A Ê which is slightly 0.5 A Ê ) longer than the other observed K±F distances in this molecule. The Al±F terminal) bond length 1.682018)±1.694019) A Ê ) is slightly longer than those in 3 1.657±1.688 A Ê )andin 4 1.672±1.677 A Ê ),respectively.The Al±F bridging) bond length 1.802817)±1.814417) A Ê ) is comparable to that in 3 1.7881±1.802 A Ê ) and in 4 1.817±1.823 A Ê ). The F±K±F angles are acute for F2)#1± K1)±F4)#1 73.305)8) and F3)±K1)±F5) 72.575)8) and more open for F3)±K1)±F4)#1 114.146)8) and F2)#1±K1)±F5) 109.566)8). All potassium atoms in the chain are in plane with a K±K±K angle of 137.743)8 Fig. 3). The potassium in 4 is six-fold coordinated by four ¯uorine and two oxygen of the THF molecules. In contrast, Journal of Fluorine Chemistry 112 2001) 219±223 * Corresponding author. Tel.: 49-551-393001; fax: 49-551-393373. E-mail address: hroesky@gwdg.de H.W. Roesky). 0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0022-113901)00525-5