Bichler Bernhard, Holzhacker Christian, Glatz Mathias, Stöger Berthold, Kirchner Karl
Institute of Applied Synthetic Chemistry, Getreidemarkt 9/163, 1060 Vienna, Austria.
Institute of Chemical Technologies and Analytics, Division of Structural Chemistry, Getreidemarkt 9/164-SC, 1060 Vienna, Austria.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2015 Oct;71(Pt 5):524-34. doi: 10.1107/S2052520615015097. Epub 2015 Sep 19.
The systematic twinning of three 2,6-diaminopyridine-based Fe-PNP complexes is interpreted using order-disorder (OD) theory. The monoclinic [Fe(0)(PNP(Et)-(i)Pr)(CO)2] [P112(1)/b, Z' = 4] possesses pseudo-orthorhombic metrics and crystallizes as a reflection twin by pseudo-merohedry with the twin plane (100). The structure is made up of layers with idealized p2(1)a(b) symmetry. The a glide planes of adjacent layers do not overlap, leading to OD polytypism. trans-[Fe(II)(PNP-Et)Br2(CO)] [P2(1)/n, Z' = 1] is systematically twinned via twofold rotation about [001]. It is made up of OD layers with idealized p2(1)2(1)(2) symmetry. OD polytypism is caused by the twofold rotation axes of adjacent layers which do not overlap. [Fe(II)(κ(2)P,N-PNP-(i)Pr,TAD)Cl2]·THF [P1, Z^{\prime} = 2] is systematically twinned via a twofold rotation about [010]. It is made up of layers with idealized p121(1) symmetry. OD polytypism is caused by screw rotations relating adjacent layers with an intrinsic translation along a fourth of a primitive lattice vector. In all three structures the twin individuals are a polytype with a maximum degree of order (MDO) and at the twin interface is located a fragment of the second MDO polytype.
利用有序-无序（OD）理论解释了三种基于2,6-二氨基吡啶的铁-磷氮磷（Fe-PNP）配合物的系统孪晶现象。单斜晶系的[Fe(0)(PNP(Et)-(i)Pr)(CO)2] [P112(1)/b，Z' = 4]具有假正交晶系的度量，并且通过假旋转反映形成孪晶，孪晶面为(100)。该结构由具有理想化p2(1)a(b)对称性的层组成。相邻层的a滑移面不重叠，导致OD多型性。反式-[Fe(II)(PNP-Et)Br2(CO)] [P2(1)/n，Z' = 1]通过围绕[001]的二次旋转系统地孪晶化。它由具有理想化p2(1)2(1)(2)对称性的OD层组成。OD多型性是由相邻层不重叠的二次旋转轴引起的。[Fe(II)(κ(2)P,N-PNP-(i)Pr,TAD)Cl2]·THF [P1，Z' = 2]通过围绕[010]的二次旋转系统地孪晶化。它由具有理想化p121(1)对称性的层组成。OD多型性是由沿着原始晶格向量的四分之一具有固有平移的相邻层之间的螺旋旋转引起的。在所有三种结构中，孪晶个体都是具有最大有序度（MDO）的多型体，并且在孪晶界面处位于第二MDO多型体的一个片段。
