Crystal Structure of K[CpFe(CO)2]: Helical Chains with Strong Cation-Anion Interactions between the Helices

Abstract

The reaction of KSi with [CpFe(CO)2]2 in DME (1,2-dimethoxyethane) yields deep red crystalline K[CpFe(CO)2] (1). 1 crystallizes monoclinically in the space group P21/a (No. 14) with a = 10.953(4), b = 10.159(3), c = 7.347(2) Å, β = 107.89(2)°, Ζ = 4, R = 0.028, Rw = 0.030. Crystals of 1 consist of polymeric chains, formed by strong K-O interactions [d(K-O) 2.915(2), 2.773(2) A], while van-der-Waals interaction between neighboring helices leads to formation of a three-dimensional network with short distances d(K-C) [3.173(3) to 3.292(3) A].