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KNaC2 (I) is prepared by reacting 2 equivs.

Three Inter-Alkali Metal Acetylides: KNaC 2, KRbC2, and NaRbC2: Syntheses, Crystal Structures, and Structural Systematics. -KNaC 2 (I) is prepared by reacting 2 equivs. KC 2H with 2.5 equivs. Na in liquid NH3 (-70 C) followed by heating the residue in dynamic vacuum (200 C, 12 h). A similar route is used for NaRbC2 (II) with RbC 2H as the precursor. KRbC2 (III) is prepared by heating equimolar amounts of Rb 2C2 and K2C2 in a dynamic vacuum (200 C, 12 h). Compounds (I) and (III) crystallize as a variant of the anti-PbCl 2-type structure (Pnma, Z = 4, powder XRD), whereas (II) crystallizes as a variant of the anti-PbFCl-type structure (Pmmn, Z = 2). Based on a systematic approach developed by Sabrowsky et al. for inter-alkali metal chalcogenides, all known inter-alkali metal acetylides are classified into two classes: variants of the anti-PbCl2 type structure and variants of the anti-PbFCl type structure. Acetylides with molar volumes (Q(ABC 2)) 1.45 crystallize in the anti-PbCl2-type structure, whereas for Q(ABC 2) >1.45 the anti-PbFCl-type structure is found. -(LIEBIG, S.; BILLETTER, H.; WALLRAFF, T.; BUSCH, S.; MUELLER, S.; RUSCHEWITZ*, U.; Z. Anorg. Allg. Chem. 642 (2016) 1, 66-72, http://dx.