Metalation of N, benzamidine (1a) and -pivalamidine (1b) in tetrahydrofuran (THF) with nbutyllithium and potassium bis(trimethylsilyl)amide gives the corresponding N,NЈ-bis(2,6-diisopropylphenyl)benzamidinates and -pivalamidinates of lithium, [(thf) ). Because metalation of these amidines is not possible with [(thf) 2 Ca{N(SiMe 3 ) 2 } 2 ], a metathetical approach has been [a] 1312 chosen. Hence, the reaction of 3a with calcium iodide in THF yields (tetrahydrofuran)calcium bis[N,NЈ-bis(2,6-diisopropylphenyl)benzamidinate] (4a). For the bulkier N,NЈ-bis(2,6diisopropylphenyl)pivalamidinate, heteroleptic [(thf)Ca-{(Dipp-N) 2 C-tBu}{N(SiMe 3 ) 2 }] (4b) forms. Depending on the softness and charge-to-radius ratio, syn configuration of the amidinate ligands is observed for 2a, 4a, and 4b, whereas the anti configuration is realized in complexes 2b, 3a, and 3b, the latter being stabilized by intramolecular metal-π interactions.
Although carbon monoxide (CO) delivery materials (CORMAs) have been generated, remote-controlled delivery with light-activated CORMAs at a local site has not been achieved. In this work, a fiber optic-based CO delivery system is described in which the photoactive and water insoluble CO releasing molecule (CORM) manganese(i) tricarbonyl [(OC)3Mn(μ3-SR)]4 (R = nPr, 1) has been non-covalently embedded into poly(l-lactide-co-d/l-lactide) and poly(methyl methacrylate) non-woven fabrics via the electrospinning technique. SEM images of the hybrid materials show a porous fiber morphology for both polymer supports. The polylactide non-woven fabric was attached to a fiber optical device. In combination with a laser irradiation source, remote-controlled and light-triggered CO release at 405 nm excitation wavelength was achieved. The device enabled a high flexibility of the spatially and timely defined application of CO with the biocompatible hybrid fabric in aqueous media. The rates of liberated CO were adjusted with the light intensity of the laser. CO release was confirmed via ATR-IR spectroscopy, a portable electrochemical CO sensor and a heterogeneous myoglobin assay.
Metalation of 1-(2-furanylmethyl)-(1a) and 1-(2-pyridylmethyl)-2-tert-butyl-3-(2,6-diisopropylphenyl)-1,3-diazaprop-2-ene (1b) with n-butyllithium and potassium bis(trimethylsilyl)amide in tetrahydrofuran (THF) yields the corresponding lithium (2a,b) and potassium derivatives (3a,b), with the alkali metals binding to the furanylmethylamido and pyridylmethylamido pockets. The calcium derivatives are accessible via a metathetical approach of the potassium complexes with calcium iodide in THF. Whereas bis[1-(2-furanylmethyl)-2-tertbutyl-3-(2,6-diisopropylphenyl)-1,3-diazaallyl]calcium (4a) precipitates as a thf adduct, bis[1-(2-pyridylmethyl)-2-tert-butyl-3-(2,6-diisopropylphenyl)-1,3diazaallyl]calcium (4b) crystallized without solvent coligands. Instead of coordinated solvent molecules, strong calcium−π interactions to an aryl group saturate the coordination sphere. Bidentate 1,2-dimethoxyethane (DME), however, is able to replace this side-on bound aryl group, leading to the dme adduct of bis[1-(2-pyridylmethyl)-2-tert-butyl-3-(2,6-diisopropylphenyl)-1,3-diaallyl]calcium ( 4c). In all of these s-block metal complexes, strong agostic interactions between the cations and the tert-butyl groups stabilize these complexes.
The amidines Dipp-N=C(tBu)-N(H)-Qu (1a) (Dipp = 2,6-diisopropylphenyl, Qu = 8-quinolyl) and Dipp-N=C(tBu)-N(H)-Py (1b) (Py = 2-pyridyl) are deprotonated with KN(SiMe3)2, yielding potassium N-(2,6-diisopropylphenyl)-N'-(8-quinolyl)pivalamidinate (2a) and potassium N-(2,6-diisopropylphenyl)-N'-(2-pyridyl)pivalamidinate (2b). Metalation of 1a with [(thf)2Ca{N(SiMe3)2}2] in tetrahydrofuran (thf) leads to the formation of ether-free calcium bis[N-(2,6-diisopropylphenyl)-N'-(8-quinolyl)pivalamidinate] (3a) with a strong intramolecular calcium-π interaction with one Dipp group. Furthermore, agostic bonds to one tert-butyl substituent complete the coordination sphere of the metal center and stabilize this bonding situation. The metathesis reaction of 2b with [(thf)4CaI2] yields the thf adduct of calcium bis[N-(2,6-diisopropylphenyl)-N'-(2-pyridyl)pivalamidinate] (3b). In addition to the bonds between calcium and the hard Lewis bases (oxygen of thf, nitrogen atoms of the pyridylamido moieties), anagostic Ca-H bonds to the tert-butyl substituents complete the coordination sphere. The intramolecular calcium-π interaction with an aryl group as observed in 3a requires steric shielding of the alkaline earth metal center, safely excluding the formation of a complex with more than one thf ligand.
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