Synthesis and Crystal Structures of K 2 SnAs 2 and a New Modification of NaAs

Solid state reactions of potassium or sodium with tin and arsenic resulted in the formation of a new ternary Zintl phase, K 2 SnAs 2 ( 1 ) and a new modification of the binary Zintl phase NaAs ( 2 ), the syntheses and structures we report herein. Compound 1 is described in the orthorhombic space group Cccm with the unit cell dimensions a = 14.653(5), b = 25.415(6), c = 6.953(4) Å, V = 2589(2) Å 3 at 203 K, R (int) = 0.1686 and final R values R 1 = 0.0780 [ I > 2σ( I )); wR 2 = 0.1810 (all data)). Compound 2 crystallizes in the monoclinic space group P 2 1 / c and accords to the LiAs structure type with the unit cell dimensions a = 6.242(9), b = 5.849(7), c = 11.55(2) Å, β = 117.1(2)°, V = 375(1) Å 3 at 173 K, R (int) = 0.0812 and final R values R 1 = 0.0677 [ I > 2σ( I )); wR 2 = 0.1541 (all data).