Rational Design of the First Closed Coordination Capsule with Octahedral Outer Shape

Abstract

The rational synthesis of an octahedral coordination capsule in which the triangular faces are covered by single ligands is described herein. Starting with tris(2-hydroxybenzylidene)triaminoguanidinium chloride [H(6)L]Cl, we observed an oxidative cyclization of this ligand in the presence of PPh(4) (+) ions resulting in the complex [Pd(H(2)L')(PPh(3))] (1). The use of 5,5-diethylbarbiturate (bar(2-)) as a bridging ligand in the presence of [Co(en)(3)](3+) (en=ethylenediamine) leads to the formation of a rectangular box with the formula (Et(4)N)(6)[[Co[(PdCl)(Pd)L](2)(mu-bar)](2)] (2). The analysis of the architecture of compounds 1 and 2 enables the development of a self-assembly strategy for the synthesis of an octahedral coordination cage 3 with the formula Na(4)(Et(3)NH)(12)[(Pd(3)L)(8)[mu-(bar)](12)].x H(2)O. Compound 3 was characterized by (13)C-MAS-NMR spectroscopy and single-crystal structure analysis.

Rational Design of a Double‐Walled Tetrahedron Containing Two Different C3‐Symmetric Ligands

“…This design principle can be used for the construction of even more complex coordination compounds with additional ligands, such as octahedral or trigonal-bipyramidal cages. [7,8] However, we are just starting to understand the reactions that take place when the ligands and metal centers do not match exactly, and a prediction of the products is not usually possible. Herein, we report the rational design of the first double-walled tetrahedron containing a ligand-metal pair that is not perfectly matched.…”

Rational Design of a Coordination Cage with a Trigonal‐Bipyramidal Shape Constructed from 33 Building Units

“…At the corners of the octahedron close contacts between two aromatic protons were observed (2.5(2) ). [5] The replacement of these hydrogen atoms with bulkier Br atoms should prevent the formation of the octahedral cage. Therefore, we allowed tris(5-bromo-2-hydroxybenzyl)triaminoguanidinium chloride, [H 6 Br 3 L]Cl, [11] to react with PdCl 2 and NaHbar under similar conditions.…”

“…One equatorial corner in the intended trigonal bipyramid is similar to the corner in an octahedron, which we previously constructed from the ligands tris(2-hydroxybenzyl)triaminoguanidinium chloride, [H 6 L]Cl, and sodium 5,5-diethylbarbiturate, NaHbar, which have threefold and twofold symmetry, respectively ( Figure 2). [5] The obvious question is how formation of such an octahedral cage of higher symmetry can be prevented. At the corners of the octahedron close contacts between two aromatic protons were observed (2.5(2) ).…”

Gezielte Synthese eines doppelwandigen Tetraeders, aufgebaut aus zwei unterschiedlichen C3‐symmetrischen Liganden

“…Das Baukastenprinzip kann sogar auf kompliziertere Systeme angewendet werden: So führt der zusätzliche Einbau von zweifach verbrückenden Liganden zur Bildung von Koordinationskäfigen mit der äußeren Gestalt eines Oktaeders oder einer trigonalen Bipyramide. [7,8] : 0.97 [9] ). Dieser kleinere Radius würde dazu führen, dass die Tetraederflächen einander zu nahe kommen, was sterisch ungünstig ist.…”