Synthesis and Characterization of [Fe3(As3)3(As4)]3−, a Binary Fe/As Zintl Cluster With an Fe3 Core

We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe3(As3)3(As4)]3−, present in both [K([2.2.2]crypt)]3[Fe3(As3)3(As4)] (1) and [K(18‐crown‐6)]3[Fe3(As3)3(As4)]⋅en (2). The cluster contains an Fe3 triangle with three short Fe−Fe bond lengths (2.494(1) Å, 2.459(1) Å and 2.668(2) Å for 1, 2.471(1) Å, 2.473(1) Å and 2.660(1) Å for 2), bridged by a 2‐butene‐like As4 unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe−Fe bonds stabilizing the Fe3 core. The binary iron arsenide cluster, [Fe3(As3)3(As4)]3−, contains a triangular Fe3 core with short Fe−Fe bonds.