Search

Almost equal molecular sizes of diiodoacetylene (C2I2) and the [Br3]− anion result in isomorphic neutral cocrystal (DMFc–C2I2) and [DMFc]+Br3− salt. This isomorphic pair of neutral and ionic crystals provides a unique example for the analysis of different types of bonding resulting in isotypic solid-state structures. Their energy frameworks visualize the obvious difference between their energetic structures: the lattice of DMFc–C2I2 is built upon the chains stabilized by I···(η5-C5Me5) halogen bonds; at the same time, [DMFc]+Br3− consists of electrostatically assembled layers associated by Br···π(Cp*) XBs interactions.

1,2-trans-diiodo-ethene (C2H2I2) – is an overlooked halogen bond donor, which demonstrate the distinct similarity of the geometry and directionality of I···I halogen bonds around the iodine atoms in its native and CpMn(CO)2(C2H2I2) π-complex crystals. Distortion of the planar geometry of C2H2I2 upon the π-coordination result the distortion of the native planar layered geometry of C2H2I2, so that [CpMn(CO)2](π-C2H2I2) features more complex I···I XB assisted 3D network. Unusual structural parallels between the native C2H2I2 crystals and solid iodine are discussed.

In the cocrystalline salts [(Me5C5)2Fe]+I3−/(4-XC6H4OH) (X = Cl, I), the directionality of X ⋯ I − I 2 halogen bonds is a significant packing factor notwithstanding their relatively low energies (∼10 kcal mol−1), as compared to the fivefold stronger ionic bonding between [(Me5C5)2Fe+] and [I3]− (∼50 kcal mol−1). This adds significant details to the structural landscape of [(Me5C5)2Fe+]I3 and offers an illustrative example of the stronger structure-defining effect of halogen bonding over the hydrogen one.

o-Ferrocenylcarbonylbenzoic acid (η5-C5H5)Fe(η5-C5H4C(O)C6H4COOH) (I) and o-cymantrenylcarbonylbenzoic acid (II) were obtained from ferrocene or (η5-C5H5)Mn(CO)3, respectively, by the Friedel–Crafts reaction with phthalic anhydride. Methyl o-ferrocenylcarbonylbenzoate (η5-C5H5)Fe(η5-C5H4C(O)C6H4COOMe (III) and methyl o-cymantrenylcarbonylbenzoate (CO)3Mn(η5-C5H4C(O)C6H4COOMe) (IV) were synthesized from I and II, respectively using dimethyl carbonate (DMC) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to promote the methylation reaction. 4-Ferrocenylphthalazin-1(2H)-one (V) and 4-cymantrenylphthalazin-1(2H)-one (VI) were obtained by the interaction of hydrazine hydrate with I and II, respectively, by the prolonged reflux or convenient solvothermal synthesis. Cyclic voltammetry measurements showed that compounds III and V undergo reversible one-electron oxidation, localized presumably at the ferrocene unit. For III the irreversible one-electron oxidation is apparently associated with the oxidation of the benzoate fragment. All new compounds were characterized by spectroscopic methods and the molecular structures of II and III were determined by X-ray diffraction analysis.

By the reaction of tetramer [Me3Pt(μ3-Cl)]4 with RhCl3 and [PPN]Cl (PPN = Ph3P = N=PPh3+) in a acetone-DCM mixture under the influence of ultrasound a heterometallic ionic complex [PPN][Me3Pt(μ-Cl)3Rh(μ-Cl)3PtMe3] (I) have been prepared. Tetranuclear complex [PPN]2 [(Me3Pt)2Ru2(μ-O)(μ-Cl)6Cl4]2- (II) have been obtained in a small yield starting from RuCl3 in similar conditions. Complex II has also been prepared purposefully in higher yield by the action of Me3Pt(Me2CO)3][PF6] on [PPN]4[Ru2OCl10]. Both complexes were characterized by elemental analysis, 1H, 13C, and 195Pt NMR spectroscopy, and their structures were determined by single crystal X-ray diffraction.

The crystal structures of PhMeTeI2 (1), FcMeTeI2 (2) and [FcMe2Te]+I− (3), which are the products of iodomethylation of R2Te2 (R = Ph, ferrocenyl (Fc)) by MeI, are reported. Analysis of secondary interactions and packing patterns in 1–3 revealed Te⋯πPh chalcogen bonding in 1, unusual structural parallels between 2 and 3, and unprecedented isomorphic substitution in the crystals of 3 with an admixture of Te–I ionized molecules 2 [FcMeTeI+]I−. In summary, we are discussing the 3c-4e bonding model as a general, seamless scheme for the geometry and electronic structure of hypervalent tellurium atom coordination in both the isolated molecules and crystals, which overcomes the confusing division between the molecular and supramolecular geometry.

In the co-crystals of diphenyl dichalcogenides Ph2E2 (E = Se, Te), the E–E and E–π(Ph) chalcogen bonds assemble Ph2E2 molecules into the chains, which imitate the typical packing patterns of the parent Ph2E2 crystals. These co-crystals consist of quite stable tectonic 1D and 2D Ph2E2 chain architectures, which are repeated in the crystals of pure Ph2E2 as well as in their co-crystals with the halogen bond donor molecules. These chains can be clearly visualized as separate parallel 1D and 2D structures in the energy framework diagrams in CrystalExplorer. From this point of view, the supramolecular reaction of Ph2E2 with the halogen bond donor 1,4-diiodotetrafluorobenzene (p-DITFB) can be considered as the insertion of p-DITFB molecules between the Ph2E2 chains in such a way that I–E and I–π(Ph) halogen bonds come in place of E–E and Te–π(Ph) chalcogen bonds, which are responsible for the close packing of these chains in the parent crystal form. Persistent packing patterns found in parent and binary crystals can provide insight into the mechanism of the crystallization process.

The supramolecular arrangement of 4-cyanopyridine (4CNpy) in its native crystal form and its co-crystals with halogen bond (XB) donors is discussed in terms of long-range synthon aufbau modules (LSAMs) and energy frameworks. Dissociations of 2D zigzag chains of parent 4CNpy into 1D dimers observed in its co-crystals are in good agreement with the aufbau model. Its co-formers, XB donors 1,4-I2(CF2)4, C2I2, 1,3- and 1,4-I2C6F4 (m- and p-DITFB), provide equal energy of I⋯N XBs, but perfluorinated iodo-alkane 1,4-I2(CF2)4 and diiodoacetylene C2I2 cannot achieve the same strength of homomolecular aggregation as π–π stacking in columnar DITFB modules. As a result, DITFBs form I⋯N XBs with both Npy and NCN nitrogen atoms of 4CNpy, while 1,4-I2(CF2)4 and C2I2 only with the Npy atom. This is not a particular case of 4CNpy co-crystals, but in general, DITFB appears to be a more effective XB donor co-former than C2I2, 1,4-I2(CF2)n and other iodo-XB donors, which has similar potential to an iodine atom but lacks homomolecular aggregation. In supramolecular reactions of p-DITFB with (η6-Ar)RuX2(4CNpy) (Ar = p-cymene, X = Cl, I) bearing Npy-coordinated 4CNpy, the former gives definite preference to the XBs with the halogen atoms, but not to the CN group of the 4CNpy ligand.

Claisen condensation of acetylferrocene (η5-C5H5)Fe(η5-C5H4COCH3) and methyl ether of cymantrenecarboxylic acid (CO)3Mn(η5-C5H4COOMe) results in β-diketone (η5-C5H5)Fe(η5-C5H4)-C(O)CH2C(O)-(η5-C5H4)Mn(CO)3 (I) which reacts with hydrazine to form a heterometallic pyrazole (η5-C5H5)Fe(η5-C5H4)-N2C3H3-(η5-C5H4)Mn(CO)3 (II) or reacts with diiodo(p-cymene)ruthenium(II) dimer giving chelate β-ketoenolate complexes of ruthenium, (p-cymene)RuI[(η5-C5H5)Fe(η5-C5H4)-C(O)CHC(O)-(η5-C5H4)Mn(CO)3] (III). The structures of complexes I–III were determined by single crystal X-ray diffraction. Electrochemical properties were studied too.

Formal substitution of aryl group on to the ferrocenyl in [CpFe(CO)(μ-TeR)]2 (R = Ar, Fc) complex dramatically changes its Fe2Te2 core structure and chemical properties. Introduction of electron-rich and bulky ferrocenyl moiety instead of Ph in [CpFe(CO)TePh]2 provide flattening of Fe2Te2 core in [CpFe(CO)(μ-TeFc)]2 (1), further photochemical decarbonylation resulting unusual [(CpFe)3(μ-TeFc)3(μ-CO)(CO)] cluster (2). The electrochemical oxidation of 1 shows two reversible one-electron oxidation waves attributed to oxidation of Fe2Te2 core. Chemical oxidation of 1 is accompanied by isomerization of its core and results in dicationic salt cis-[CpFe(CO)(μ-TeFc)]2 (PF6)2 (3). This study also provides an illustrative example of the increasing nuclearity in Fe1 → Fe2 → Fe3 row, upon the stepwise electron-compensating decarbonylation of iron-carbonyl complexes and (apart from this) insight into the distribution of toluene molecules inclusion inside the channels of crystals of compound 2.