Coordination polymers with [Au(CN)4]- building blocks: a 1-d chain of molecular NiII 2AuIII 2 squares

The Use of Polarizable [AuX2(CN)2]− (X = Br, I) Building Blocks Toward the Formation of Birefringent Coordination Polymers

“…The X-ray structure reveals the expected square-planar Au(III) center with trans-Br and -CN ligands. The Au−C and Au−Br bond lengths of 2.003(6) and 2.4120(5) Å, respectively, are unremarkable and comparable to other such distances. ,, Of greater interest is the intermolecular packing of the [AuBr 2 (CN) 2 ] − units. Rather than crystallizing as well-separated ion pairs, or forming M···M interactions typical for Au(I) and Pt(II), or forming Au−CN···Au interactions as observed for [Au(CN) 4 ] − , the anions form 1-D chains along the [110] and [11̅0] directions by virtue of Br···Br interactions. , The latter direction also corresponds to the principal plane of crystal growth when grown via slow evaporation of a MeOH solution.…”

“…The Au-C and Au-Br bond lengths of 2.003(6) and 2.4120(5) A ˚, respectively, are unremarkable and comparable to other such distances. 41,42,49 Of greater interest is the intermolecular packing of the [AuBr 2 (CN) 2 ]units. Rather than crystallizing as well-separated ion pairs, or forming M 3 3 3 M interactions typical for Au(I) and Pt(II), 37 or forming Au-CN 3 3 3 Au interactions as observed for [Au-(CN) 4 ] -, 40 the anions form 1-D chains along the [110] and [110] directions by virtue of Br 3 3 3 Br interactions.…”

“…A critical requirement vis a vis toward using the [AuX 2 (CN) 2 ] − units as birefringence-enhancing units is that their supramolecular alignment must be “favorable”. For example, alignment of the [Au(CN) 2 ] − units in related cyanoaurate(I) coordination polymers is enhanced by the formation of attractive aurophilic interactions. ,, However, analogous d 8 −d 8 Au(III) interactions are rare and have never been observed in the few examples of related [Au(CN) 4 ] − -containing coordination polymers. − On the other hand, weak halogen−halogen interactions − could play a similar role as aurophilicity in impacting the supramolecular structures of [AuX 2 (CN) 2 ] − -containing coordination polymers.…”

“…19,37,38 However, analogous d 8 -d 8 Au(III) interactions are rare 37 and have never been observed in the few examples of related [Au(CN) 4 ] --containing coordination polymers. [39][40][41][42][43] On the other hand, weak halogen-halogen interactions [44][45][46] could play a similar role as aurophilicity in impacting the supramolecular structures of [AuX 2 (CN) 2 ] --containing coordination polymers.…”

Heterobimetallic Coordination Polymers Based on the [Pt(SCN)4]2– and [Pt(SeCN)4]2– Building Blocks

“…On a more general note, when compared to similar structures synthesized using d 8 square-planar [Au(CN) 4 ] − instead of [Pt(XCN) 4 ] 2– (X = S, Se), no interactions were denoted between the Pt(II) centers and any other donors (e.g., adjacent – NCS units), as opposed to the readily observed apical/axial Au(III)–NC interactions between the Au(III) centers and the N(cyano) units from adjacent [Au(CN) 4 ] − moieties. ,− Importantly, compared to the d 8 [Pt(CN) 4 ] 2– unit, no Pt–Pt metallophilic interactions were observed in any of these systems, which is somewhat surprising given the fact that soft ligands such as S and Se donors tend to favor such metallophilic interactions in d 10 Au-based systems. It is possible that the nonplanarity of the [Pt(XCN) 4 ] 2– units may restrict their ability to form such metal-based attractive interactions.…”