[Fe(PNN-iPr)Br2]·xDCM: the first example of merotype-epitaxy of a molecular structure and its solvatomorph

Abstract

Abstract Crystals of the Fe-PNN-pincer complex [Fe(PNN-iPr)Br2] 1 (PNN-iPr=N-(diisopropylphosphanyl)-6-[(isopropylamino)methyl]pyridin-2-amine) grown from a pentane/DCM mixture are made up of two independently diffracting domains with different stoichiometry, viz. 1 [P21/a, Z = 4, a = 14.2995(10) Å, b = 11.8043(8) Å, c = 12.4229(8) Å, β = 93.618(4)°, V = 2092.8(2) Å3] and its solvatomorph 1·DCM [A2/a, Z = 8, a = 14.2449(8) Å, b = 11.8208(8) Å, c = 30.091(2) Å, β = 111.501(4)°, V = 47142.3(5) Å3] with a volume ratio of 64.30:35.70(9). Both domains belong to a family of merotypes (polysomes that feature one common layer). They contain equivalent 1 layers, which are intercalated in 1·DCM by solvent layers. The crystals are therefore an example of solvato-merotype-epitaxy. A crystal made up of only the solvate domain 1·DCM-d2 [A2/a, Z = 8, a = 14.2796(9) Å, b = 11.8868(7) Å, c = 29.9135(19) Å, β = 110.9847(8)°, V = 4740.7(5) Å3] was grown from DCM-d2. An extension of the symmetry concepts of order-disorer (OD) theory to the more general case of merotypes or even polysomes is outlined.