In this paper, we compare and discuss the very different crystal structures and supra­molecular arrangements obtained when using different crystallization solvents with the same organometallic moiety. The new title tetra­hydro­furan (THF) solvate, [Rh₂(C₂H₃O₂)₄(C₂₇H₃₆N₂)₂]·4C₄H₈O, is compared with the toluene tri­solvate reported previously by us [Góis, Trindade, Veiros, Andre, Duarte, Afonso, Caddick & Cloke (2007). Angew. Chem. Int. Ed. 46, 5750–5753]. The mol­ecular structures of the two complex mol­ecules display a similar conformation, but due to the presence of different solvent mol­ecules, the two solvates crystallize in different space groups and exhibit quite diverse supra­molecular assemblies. The toluene solvate crystallizes in the triclinic space group P, while in the presence of THF, the monoclinic P2₁/c space group is obtained, with the complex mol­ecule residing on an inversion centre. The resulting crystal packing displays no classical hydrogen bonds but different supra­molecular synthons give rise to different packing motifs. In this work, we highlight the different supra­molecular architectures obtained when organometallic moieties crystallize with different solvent mol­ecules. We compare the novel structure of the THF derivative with that of the toluene solvate of a dirhodium(II) complex belonging to a new family of catalyst compounds exhibiting very high performance in aryl­ation processes.

A second polymorphic form (form II) of the previously reported 1,4,7-tris­(p-tolyl­sulfon­yl)-1,4,7-triaza­cyclo­nonane (form I), C₂₇H₃₃N₃O₆S₃, is presented. The mol­ecular structures of the two forms display very different conformations, thus prompting the two forms to crystallize in two different space groups and exhibit quite diverse crystal structure assemblies. Form I crystallizes in the triclinic space group P, while form II crystallizes in the monoclinic space group P2₁/n. The main differences between the two mol­ecular structures are the conformations of the p-tosyl groups relative to each other and to the macrocyclic ring. The resulting crystal packing displays no classical hydrogen bonds, but different supra­molecular synthons give rise to different packing motifs.

In the title complex, trans-{2,2′-[cyclo­hexane-1,2-diyl­bis­(ni­t­rilo­methyl­idyne)]­di­phenol­ato-κ⁴O,N,N′,O′}­nickel(II)–chloro­form (1/1), [Ni(C₂₀H₂₀N₂O₂)]·CHCl₃, the Ni atom has a square-planar geometry, slightly tetrahedrally distorted. The Ni—N and Ni—O bonding distances are within the expected ranges for Ni–Schiff base derivatives. The di­imine bridge has a gauche conformation with the cyclo­hexyl ring almost coplanar with the NiN₂O₂ plane. The complex mol­ecules pack in dimers with an NiNi distance of 3.59 (1) Å and form a three-dimensional structure displaying a herring-bone configuration. Channels are occupied by solvent mol­ecules, which are involved in C—HO hydrogen bonds with the ligand O atoms.

The title compound, [1,2-bis(diphenylphosphino)ethane](η⁵-cyclo­penta­dienyl)(4-nitro­benzonitrile)iron(II) iodide, [Fe(η⁵-C₅H₅)(C₇H₄N₂O₂)(C₂₆H₄P₂)]I, crystallizes in the non-centrosymmetric space group Cc, which is a promising result for obtaining quadratic non-linear optical properties. However, the packing shows that the iodide counter-ion promotes the cancellation of almost all the dipoles, resulting in a supra­molecular motif of cationic chains aligned in opposite directions making an angle of 35.2°. The use of PF₆⁻ as counter-ion induces the crystallization of the complex in a centrosymmetric space group. These results show that the introduction of different counter-ions, of different size and geometry, allows specific and directional inter­molecular inter­actions that can determine the formation of a particular type of crystal packing.

The title compound, (⁵-cyclo­penta­dienyl)(4-nitro­benzo­nitrile-N)(trimethyl­phosphine-P)(triphenyl­phosphite-P)iron(II) hexa­fluoro­phosphate, [Fe(C₅H₅)(C₇H₄N₂O₂)(C₁₈H₁₅O₃P)(C₃H₉P)]PF₆, has been characterized by spectroscopic and X-ray diffraction in order to evaluate the tuning of the electron density at the metal centre and the extension of the delocalization on the mol­ecule due to the presence of phosphite and phosphine co-ligands. The compound crystallizes in the centrosymmetric space group P2₁/c, which destroys the possibility of exhibiting any quadratic non-linear optical properties. The packing shows a supramolecular zigzag chain of antiparallel cations connected via the PF₆^- anions through C-HF^- inter­actions, with HF distances ranging from 2.39 to 2.67 Å. Each zigzag chain is composed of isomeric organometallic fragments containing either R or S mol­ecules. These chains are connected through weak inter­molecular C-HC inter­actions, forming a two-dimensional plane parallel to (101).

The structure of the title compound, [Ti(C₂H₆N)₂(C₆H₈N)Cl], displays a ⁵-coordination mode for the pyrrolyl ring, confirmed by the values of the slip parameter [0.073 (9) Å] and the fold angle [4.6 (6)°]. This coordination is confirmed by NMR data, which point to the involvement of the complex in a fluxional process in solution above 285 K, passing through an intermediate involving simultaneously a metal-aza­allyl and a metal-olefin bond.