Four‐Center Nodes: Supramolecular Synthons Based on Cyclic Halogen Bonding

Abstract

The isocyanide trans‐[PdBr2(CNC6H4‐4‐X′)2] (X′=Br, I) and nitrile trans‐[PtX2(NCC6H4‐4‐X′)2] (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four‐center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen‐bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic‐like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol−1.

Dihalomethanes as Bent Bifunctional XB/XB‐Donating Building Blocks for Construction of Metal‐involving Halogen Bonded Hexagons

“…When CH 2 X 2 and trans ‐[MX M 2 (CNC 6 H 4 ‐4‐X C ) 2 ] are mixed together, the situation resembles that when two different metal centers compete for one ligand and the result of this interplay depends on thermodynamic stability of one or another complex. In our case (Figure ), assembly of trans ‐[MX M 2 (CNC 6 H 4 ‐4‐X C ) 2 ] by the four‐center cyclic XB nodes was achieved in the absence of any external XB donor, whereas in the presence of an external CH 2 X 2 , the σh of the halomethanes starts to compete with X for the nucleophilic X M ligands to give the rectangular structures (Figure , ).…”

“…Palladium(II) and platinum(II) complexes have been previously applied as the primary scaffolds for XB‐crystal engineering due to the rigid 90/180° orientation of σh donor (σhD) and σh acceptor (σhA) sites . Recently we explored assembly of various Pd II ‐ and Pt II ‐based 2σhD/2σhA systems including, in particular, the isocyanide trans ‐[PdBr 2 (CNC 6 H 4 ‐4‐X C ) 2 ] (X C =Br, I) complexes (Figure ). The assembly was conducted in the absence of any external XB‐donor and it gave 2D structures linked by four‐center cyclic nodes, where 2σhD/2σhA systems are linked exclusively by XBs.…”

“… Schematic representation of the assembly of the isocyanide complexes (Ref. , top) and the assembly of the isocyanide complexes in the presence of CH 2 X 2 (bottom).…”

The halogen bond with isocyano carbon reduces isocyanide odor

“…Taking into account our general interest in the isocyanide chemistry (for our relevant review see ref. 21 ) and, in particular, isocyanide involving crystal engineering [22][23][24][25][26] , we focused our efforts on isocyanide species (CNR) featuring potential lp at the C atom. As a model XB acceptor for this study we addressed the isocyanide CNMes because of its broad usage, commercial availability, and excellent solubility in nonpolar solvents.…”

Non-Covalent Interactions in Coordination and Organometallic Chemistry

“…Furthermore, other dihalomethanes were also considered as bent bifunctional building blocks for the construction of metal-involving halogen bonded hexagons [18]. In [19], [24]. The halogen bonding-assisted assembly of bromoantimonate(V) and polybromide-bromoantimonate-based frameworks was reported in [25].…”