Shedding Light on the Interactions of Hydrocarbon Ester Substituents upon Formation of Dimeric Titanium(IV) Triscatecholates in DMSO Solution

Abstract

The dissociation of hierarchically formed dimeric triple lithium bridged triscatecholate titanium(IV)h elicates with hydrocarbyle sters as side groups is systematically investigated in DMSO. Primary alkyl, alkenyl, alkynyl as well as benzyl esters are studied in order to minimize steric effects close to the helicate core. The 1 HNMR dimerizationc onstants for the monomer-dimer equilibrium show some solvent dependent influenceo ft he side chains on the dimer stability.I nt he dimer,t he ability of the hydrocarbyle ster groups to aggregate minimizes their contacts with the solvent molecules. Due to this, most solvophobic alkyl groups show the highest dimerization tendency followed by alkenyls, alkynyls and finally benzyls.F urthermore, trends within the different groups of compounds can be observed. For example,t he dimer is destabilized by internal double or triple bonds due to p-p repulsion. As trong indication for solvent supported London dispersion interaction between the ester side groups is found by observation of an even/odd alternation of dimerizationconstants within the series of n-alkyls, n-W-alkenyls or n-W-alkynyls. This corresponds to the interaction of the parenth ydrocarbons, as documented by an even/odd melting point alternation. Figure 1. Wilcox molecular torsion balance. [a] A. Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.Figure 13. Dimerization constantsi n[ D 6 ]DMSOo fb enzyl derivatives Li[Li 3 (4 3 Ti) 2 ].Figure 14. Domains in whicht he dimerization constantso fa lkyl (green), alkenyl (red), alkynyl (blue) and benzyl ester (magenta) substituted complexes Li[Li 3 (L 3 Ti) 2 ]a re observed.

Alkyl‐Alkyl Interactions in the Periphery of Supramolecular Entities: From the Evaluation of Weak Forces to Applications

“…This is different in case of the thio‐Li[Li 3 ( 5 ) 6 Ti 2 ] in methanol‐d 4 or oxoesters Li[Li 3 ( 6 ) 6 Ti 2 ] in DMSO‐d 6 (Figure ) …”

“…Thus, mainly a solvophobic effect is responsible for the observed behavior. However, due to London dispersion the interaction of the side chains is not repulsive but attractive, so that the chain‐chain interaction may be described as a dispersion supported solvent effect or as solvent supported London dispersion …”

“…Comparison of the n ‐alkyl ester complexes with the corresponding terminal alkene and alkyne derivatives show decreasing dimerization constants in the order alkyl>alkenyl>alkynyl due to the highest solvophilicity of alkynes in DMSO and an intermediate solvophilicity of the alkenes. The mobility of the terminal alkenes or alkynes in the solvents reduces the entropic effect and a steadily increasing K dim with longer chains is observed (Figure ) …”

Bis(catecholato-κ2 O,O′)bis(dimethyl sulfoxide-κO)titanium(IV)

“…A database survey of titanium catecholate complexes reveals a plethora of homoleptic triscatecholates but only a few in monometallic assemblies. A search of the Cambridge Structural Database (CSD, Version 5.42, accessed Feb 2021;Groom et al, 2016) yields, in addition to 2 Et3NH (Borgias et al, 1984), eleven other monocationic homoleptic triscatecholate titanium complexes with only one metal center: SUKNUK (Kwamen et al, 2020), SUKQAT (Kwamen et al, 2020), GOJMIC (Tinoco et al, 2008), LEXQUD (Dong et al, 2018), LEXRAK (Dong et al, 2018), MAGLAK (Van Craen et al, 2016), VEPJUW (Davis et al, 2006), VEPKAD (Davis et al, 2006), VILXIX (Hahn et al, 1991), XIKLOV (Chen et al, 2018), and YUPNEF (Johnson et al, 2020).…”

London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction

“…Thei ntermolecular stabilization by all-meta substitution in dispersion-driven systems has been demonstrated recently, e.g.,i nt he stabilization of molecular dimers [19] and in the catalytic hydroamination of olefins. [3d] Here we also find that DEDs in meta-aryl positions provide additional attractive interactions with, e.g.,the ethyl substituent of 2-butanone,as indicated in the NCI plots ( Figure 5).…”