Structural Chemistry of “Defect” Cyanometalate Boxes:  {Cs⊂[CpCo(CN)₃]₄[Cp*Ru]₃} and {M⊂[Cp*Rh(CN)₃]₄[Cp*Ru]₃} (M = NH₄, Cs)

Abstract

A series of heptametallic cyanide cages are described; they represent soluble analogues of defect-containing cyanometalate solid-state polymers. Reaction of 0.75 equiv of [Cp*Ru(NCMe)3]PF6, Et(4)N[Cp*Rh(CN)3], and 0.25 equiv of CsOTf in MeCN solution produced (Cs subset [CpCo(CN)3]4[Cp*Ru]3)(Cs subset Rh4Ru3). 1H and 133Cs NMR measurements show that Cs subset Rh4Ru3 exists as a single Cs isomer. In contrast, (Cs subset [CpCo(CN)3]4[Cp*Ru]3) (Cs subset Co4Ru3), previously lacking crystallographic characterization, adopts both Cs isomers in solution. In situ ESI-MS studies on the synthesis of Cs subset Rh4Ru3 revealed two Cs-containing intermediates, Cs subset Rh2Ru2+ (1239 m/z) and Cs subset Rh3Ru3+ (1791 m/z), which underscore the participation of Cs+ in the mechanism of cage formation. 133Cs NMR shifts for the cages correlated with the number of CN groups bound to Cs+: Cs subset Co4Ru4+ (delta 1 vs delta 34 for CsOTf), Cs subset Rh4Ru3 where Cs+ is surrounded by ten CN ligands (delta 91), Cs subset Co4Ru3, which consists of isomers with 11 and 10 pi-bonded CNs (delta 42 and delta 89, respectively). Although (K subset [Cp*Rh(CN)3]4[Cp*Ru]3) could not be prepared, (NH4 subset [Cp*Rh(CN)3]4[Cp*Ru]3) (NH4 subset Rh4Ru3) forms readily by NH4+-template cage assembly. IR and NMR measurements indicate that NH4+ binding is weak and that the site symmetry is low. CsOTf quantitatively and rapidly converts NH4 subset Rh4Ru3 into Cs subset Rh4Ru3, demonstrating the kinetic advantages of the M7 cages as ion receptors. Crystallographic characterization of CsCo4Ru3 revealed that it crystallizes in the Cs-(exo)1(endo)2 isomer. In addition to the nine mu-CN ligands, two CN(t) ligands are pi-bonded to Cs+. M subset Rh4Ru3 (M = NH4, Cs) crystallizes as the second Cs isomer, that is, (exo)2(endo)1, wherein only one CN(t) ligand interacts with the included cation. The distorted framework of NH4 subset Rh4Ru3 reflects the smaller ionic radius of NH4+. The protons of NH4+ were located crystallographically, allowing precise determination of the novel NH4...CN interaction. A competition experiment between calix[4]arene-bis(benzocrown-6) and NH4 subset Rh4Ru3 reveals NH4 subset Rh4Ru3 has a higher affinity for cesium.

Cyanometalate Cages with Exchangeable Terminal Ligands

“…The interaction between the MeCN protons and the cyanide linkers of the cage framework was previously indicated with the solid-state structure of CsʚCo 4 Ru 3 . [2] Labeling studies provided further evidence that the CsʚCo 4 Ru 3 cage undergoes partial disassembly in solution. Two Ru-N bonds must break to dissociate a "rim" CpCo(CN) 3 -did not increase the rate vertex exchange, suggesting that vertex exchange is dissociative, being dependent only on [CsʚCo 4 Ru 3 ].…”

“…The centuries old field of metal cyanide chemistry [1] has experienced a renaissance due the zeolitic, [2,3] magnetic, [4] and electronic properties [5] of cyanometalate materials. Parallel to these application-driven studies, we have focused on synthetic methodologies leading to discrete molecular architectures that can be characterized in solution.…”

The first anion template cubic cyanometallate cage and its 3,5-dimethyltris(pyrazolyl)methane iron(II,III) tricyanide building blocks

“…Significant distortions of the cage 3 allow for formation of the pseudocubic structure from octahedral and tetrahedral corners; these occur at the 12 unique Fe-N"C angles around four coordination Fe sites. This distortion is present at each of the four coordination Fe sites to 166.3 (9)°. An examination of the cube body diagonals reveals a slight compression along one of the C 3 axes, which lowers the overall symmetry of the cage.…”

“…Polymerization could be thus inhibited, and a family of cages with a box-like architecture results. Some early examples showed that the reaction of fac À LMðCNÞ nÀ 3 with LMðH 2 OÞ mþ 3 or LMðMeCNÞ mþ 3 resulted in cyanometallate boxes, ½M 8 ðCNÞ 12 4ðnÀmþÞ , from the displacement of the labile MeCN or H 2 O ligand [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. As part of our interest in this area, we are focusing on the coordination complexes of iron, which have the same components as classic Prussian blue materials and will offer the potential for comparison with classic Prussian blue materials.…”

Ribose-protected thioguanosine-based 1H NMR spectroscopic probe for the detection of cesium from solid cesium-containing sources in acetonitrile

“…A single resonance was observed for both solutions with chemical shifts of 0.003 and 7.291 ppm (relative values), respectively. The small chemical shift difference suggested that weak interactions occur between Cs + ions and TG in CD 3 CN, because strong interactions between cesium ions and ligands will cause 133 Cs NMR resonance a large downfield shift [32].…”