Synergic anion and cation coordination using the tripodal aluminate anion [MeAl(2-py)3]− (py = 2-pyridyl)

Abstract

The coordination of AlCl(3) by the complex [{MeAl(2-py)(3)}Li.thf] () gives the unusual product [{MeAl(2-py)(3)}(2)Al](+)[{MeAl(2-py)(3)}Li](2)(mu-Cl)(-) (), in which the [MeAl(2-py)(3)](-) aluminate anion of acts cooperatively in the coordination of an Al(3+) cation and Cl(-) anion.

Postfunctionalization of Tris(pyridyl) Aluminate Ligands: Chirality, Coordination, and Supramolecular Chemistry

“…However,t hought he 3-N and 4-N atoms of 4 Li and 5 Li are not involved in any secondary intra-or intermolecular interactions, in the case of 3 Li the OCH 2 py arm is involved in intramolecular coordination throught he 2-N atom to the Al III centre of each [EtAl(6-Me-2-py) 2 (2-OCH 2 py)] À anion, resulting in ad istorted trigonal bipyramidal geometry.T his interaction [2.309(2) ]i sa tt he upper end of neutrald onor-Al III interactions found in the Cambridge Structural Database. [18] An indication of the dynamic nature of the long-range Al III À Ni nteractions in 3Li is provided by 1 Ha nd 7 Li NMR spectroscopy,c arried out in toluene. Whereas the 360 K 1 Hs pectra of 4 Li and 5 Li show sharp resonances, the OCH 2 py and 2-py resonances of 3 Li exhibit significant broadening.Reducing the temperature from 360 to 235 Kr esultsi nt he appearance of at least Scheme2.Reactionof1 Li with chiral alcohols and the formation of RR, SS,and RS dimers, with the magnetically inequivalent 6-Me environments highlighted.…”

“…2018, 24,17019 -17026 www.chemeurj.org three resonances for the CH 2 protons of the OCH 2 py group (Figure 4a). The 7 Li NMR spectrum also shows the appearance of several resonances over approximately the same temperature range (Figure 4b). The factt hat the 1 Ha nd 7 Li NMR spectra do not changes ignificantly with concentration suggests that the dynamic process involved is intramolecular (presumeably involving the intact dimer units).…”

“…The lithium salts 3 Li, 4 Li, and 5 Li were isolated in crystalline form after workup of the reactions in 29-57 %y ields and were characterized by elementala nalysis and heteronuclear ( 1 H, 13 C, 7 Li, and 27 Al) NMR spectroscopy,i na ddition to obtainingt heir single-crystal X-ray structures. They all form dimeric structures in the solid state, which are similar to the previously reported dimers 2a and 2b (Scheme 1), containing central Li 2 O 2 cores (see Figure 3).…”

“…We have been particularly interested in Group 13 tris(2‐pyridyl)aluminates ([RAl(2‐py) 3 ] − ; Figure B ) as they are unusual in this area in having an overall negative charge (rather than being neutral) . As one of the few anionic members of the tris(pyridyl) family, they exhibit a strong affinity for metal cations and have extensive coordination chemistry with a broad range of transition metals, main‐group metals, and lanthanides . The closely related tris(2‐pyridyl)borates have also attracted recent interest, stemming from their potential applications in polymer and supramolecular chemistry…”

“…with racemic mixtures of the chiral alcohols R'(Me)CH(OH)( R ' = C 2 H 5 ,C 6 H 13 ,a nd C 6 H 5 )l eads to mixtures of dimeric SS/RS-a nd SR-diastereomers. Owing to their differentm olecular symmetries, the RR/SS and RS dimers exhibit different signals in their 1 Ha nd 7 Li NMR spectra,w itht he 6-Me groupsa cting as reporter groups (Scheme 2). [12] With the above background in mind, we present here a study of the ways in which ligand exchangeo ft he 6-Me-py groups of 1 can be used to 1) access the previously unexplored 3-and 4-py functionality,l eading to supramolecular assemblies, and 2) build chirality at the Al centre by the incorporation of three different substituents.…”