Bimetallic Coordination Polymers via Combination of Substitution-Inert Building Blocks and Labile Connectors

Abstract

A rational approach to the synthesis of silver-chromium mixed-metal coordination polymers is presented: 3-cyanoacetylacetone (HacacCN) features two potential binding sites. After deprotonation, it has been used as a chelating dionato ligand in the pseudo octahedral complex Cr(acacCN) 3; two polymorphs of this compound have been identified. In its protonated form, HacacCN was employed as a N donor toward Ag(I). Both functionalities may be exploited within the same solid: The chromium complex and silver salts of weakly coordinating anions have been successfully combined to mixed-metal coordination polymers. Cr(acacCN) 3 plays the role of a substitution-inert tecton with predictable bonding geometry which interacts with the conformationally soft silver cations via two or all three of its peripheric nitrile groups. From an equimolar amount of both constituents, six solids featuring a 1:1 ratio between Cr- and Ag-derived building blocks were obtained in good yield; their structures depend on the counteranions and the cocrystallized solvent and correspond either to 2D networks with (6,3) or augmented (4,4) topology or, in one case, adopt a 3D connectivity. In addition, three products with a Cr/Ag = 2:1 stoichiometry have been isolated: they adopt two-dimensional network structures.

Interplay of ligand chirality and metal configuration in mononuclear complexes and in a coordination polymer of Cr(iii)

“…PF 6 − counter anions and hydrate water molecules occupy the voids in the resulting cationic framework. PF 6 − counter anions and hydrate water molecules occupy the voids in the resulting cationic framework.…”

Silver coordination polymers with remarkably high packing coefficients

“…In the absence of alternative N donor atoms, this coordination is not surprising. In this and the following figures which summarize silver coordination, not only conventional bonds between metal cations and donor ligands have been included for good reason: In recent contributions by our own [16,28] and other groups [18,19,21,22,45], AgÁÁÁAg distances of ca 3 Å have been discussed; it is obviously not acceptable to emphasize interactions of this [46,47]. When compared to other salts with organic anions, the calculated density of 1 is remarkably high: Our silver squarate ranks ninth amongst 3755 carbon-containing entries for which silver is the heaviest element documented in the CSD; four of the eight entries associated with a higher density refer to the same compound, namely silver oxalate.…”

“…In addition to coordination networks based on one type of cations, more complex bimetallic systems have also been described [12][13][14][15][16]. Polymers based on silver cations are particularly attractive: Their lability facilitates crystallization and dissolution processes [17], and closed-shell interactions between Ag(I) cations have recently emerged as candidates for crystal engineering [18][19][20].…”

Crosslinking of the Pd(acacCN)2 building unit with Ag(i) salts: dynamic 1D polymers and an extended 3D network

“…In addition, the pyridine derivatives in Scheme 1 (ligands a-c) behave as good N nucleophiles to metal cations. Earlier work with this ligand has covered the O, O′ coordination chemistry of Cu, Fe, 19 Cr, 20 Al, 21 and rare earth cations. 18 In contrast, the N donor capabilities of the nitrile-substituted 3-cyanoacetylacetone HacacCN (Scheme 1, d) are much less pronounced.…”