Interaction between Anions and Molybdenum Allyl Dicarbonyl Complexes of 1,4,7‐Trithiacyclononane

Abstract

The labile complex [MoCl(η3‐methallyl)(CO)2(NCMe)2] reacts with the ligand 1,4,7‐trithiacyclononane ([9]aneS3) and the salt NaBAr′4 to afford [Mo(η3‐methallyl)(CO)2([9]aneS3)][BAr′4] (1⋅BAr′4). An analogous reaction of [MoBr(η3‐allyl)(CO)2(NCMe)2] yields [Mo(η3‐allyl)(CO)2([9]aneS3)][BAr′4] (2⋅BAr′4). The new compounds 1⋅BAr′4 and 2⋅BAr′4 were characterized by IR and NMR spectroscopic analysis and X‐ray diffraction studies. Both compounds feature the cyclic thioether [9]aneS3 coordinated as a tridentate ligand to the molybdenum center. The allyl ligand in 2⋅BAr′4 is aligned with the middle of the OC‐Mo‐CO angle, which is acute. Both of these features are typical of most pseudo‐octahedral allyl dicarbonyl molybdenum complexes. In contrast, the allyl group is rotated in 1⋅BAr′4, which is attributed to steric hindrance between the methyl substituent and the ligated thioether, and the OC‐Mo‐CO angle is obtuse. Compound 1⋅BAr′4 undergoes rapid substitution of [9]aneS3 by either chloride and fluoride ions in dichloromethane, and the products include the known species [{Mo(η3‐methallyl)(CO)2}2(μ‐Cl)3]− and a structurally similar new anionic complex with two fluoro and one hydroxo bridging ligands, respectively. Stable supramolecular adducts were formed in the reactions of 1⋅BAr′4 and 2⋅BAr4 with bromide, iodide, hydrogensulfate, and methanesulfonate compounds. The binding constants of these adducts in dichloromethane were calculated from 1H NMR spectroscopic titration data, and the solid‐state structures of the 1⋅Br, 1⋅HSO4, 1⋅I, and 2⋅I adducts were determined by X‐ray diffraction studies. The surprising slightly higher stability of the iodide adduct relative to that of bromide was investigated theoretically, with the results pointing to an effect of the differential solvation of the halide ions.

Synthesis of Differently Substituted tacn‐Based Ligands: Towards the Control of Solubility and Electronic and Steric Properties of Uranium Coordination Complexes

“…After crystallization, a conglomerate21 of enantiomerically pure crystals was found for 14a· CH 2 Cl 2 · CH 3 CN with an A configuration of the metal center in the X‐ray‐analyzed crystal (Figure 4, top) 22,23. Most interesting, complexes of 14a self‐organize in the solid state into a chiral 1D polymeric superstructure as a result of weak intermolecular C–H ··· Cl contacts between three hydrogen atoms of the tacn‐ligand backbone and the axial chloride ligand ( d C–H ··· Cl = 2.71 Å; Figure 4, bottom) 24. A similar chiral 1D aggregation of one independent molecule with the A configuration was observed in the solid‐state structure of 14b ( d C–H ··· Cl = 2.66 Å; Figure 5, bottom) in which the individual complexes in the 1D polymer are rotated by 60° to each other along the crystallographic c axis.…”

Interaction between Anions and Cationic Metal Complexes Containing Tridentate Ligands with exo‐CH Groups: Complex Stability and Hydrogen Bonding

“…The IR spectra of 6 and 7, each containing two broad nCO bands, indicate their cis-dicarbonyl geometry, and the fact that the more intense band is that at higher frequency indicates acute OCÀMoÀCO angles. [6] The relatively high wavenumber values of the IR nCO bands is in agreement with the presence of cationic complexes. The 1 H NMR spectra confirm the pres- www.chemeurj.org ence of one BAr' 4 anion per molybdenum; that is, a BAr' 4 :methallyl:tris(2-pyridyl) ligand ratio of 1:1:1.…”

“…The addition of tetrabutylammonium chloride shifted the IR nCO bands of 1 only marginally to lower frequencies, indicating hydrogen bonding, rather than formation of a direct ReÀCl bond by a substitution reaction, in contrast with the results found for the molybdenum complexes. [6] The successive additions of [Bu 4 N]Cl shifted the 1 H NMR multiplet initially at 2.74 ppm to higher frequencies, whereas the signal at 3.05 ppm remained virtually unchanged. This demonstrates that the signal at 2.74 ppm in 1 corresponds to the exo hydrogens, pointing outward from the metal and, therefore, more accessible for the contact with the anions (See Scheme 1).…”

“…The latter contrasts with the dynamic behavior of [9]aneS 3 derivatives, which leads to apparent C 3 -symmetry at room temperature. [6] The solid state structures of the cationic complexes, shown in Figures 5 (6) and 6 (7), feature the tris(2pyridyl) ligands coordinated through their three nitrogen atoms to cis-Mo(h 3 -methallyl)(CO) 2 fragments. In these, the two carbonyl groups and the metal form acute angles (80.7(3)8 in 6 and 84.14(18)8 in 7) in agreement with the solution IR spectra discussed above, and, accordingly, the methallyl groups display an exo orientation.…”

“…Therefore, we synthesized and characterized complexes of [9]aneS 3 with the pseudooctahedral fragments Mo(methallyl)(CO) 2 and Mo(allyl)(CO) 2 , and studied their behavior in dichloromethane solution in the presence of several anions. [6] The results demonstrated that the molybdenum complexes were more stable than the Pd-based hosts, because the former were stable in the presence of bromide; in fact, the solid-state structure of the hydrogen bonded bromide-host ion pair could be determined by X-ray diffraction. However, the more nucleophilic chloride anion completely and rapidly displaced the [9]aneS 3 ligand in dichloromethane solution at room temperature to form the known chloride-bridged binuclear anionic [Mo(h 3 -methallyl)(CO) 2 ] 2 (m-Cl) 3 À complexes.…”