Base free N-alkylation of anilines with ArCH₂OH and transfer hydrogenation of aldehydes/ketones catalyzed by the complexes of η⁵-Cp*Ir(iii) with chalcogenated Schiff bases of anthracene-9-carbaldehyde

Abstract

The condensation of anthracene-9-carbaldehyde with 2-(phenylthio/seleno)ethylamine results in Schiff bases [PhS(CH)C[double bond, length as m-dash]N-9-CH](L1) and [PhSe(CH)C[double bond, length as m-dash]N-9-CH] (L2). On their reaction with [(η-Cp*)IrCl(μ-Cl)] and CHCOONa at 50 °C followed by treatment with NHPF, iridacycles, [(η-Cp*)Ir(L-H)][PF] (1: L = L1; 2: L = L2), result. The same reaction in the absence of CHCOONa gives complexes [(η-Cp*)Ir(L)Cl][PF] (3-4) in which L = L1(3)/L2(4) ligates in a bidentate mode. The ligands and complexes were authenticated with HR-MS and NMR spectra [H, C{H} and Se{H} (in the case of L2 and its complexes only)]. Single crystal structures of L2 and half sandwich complexes 1-4 were established with X-ray crystallography. Three coordination sites of Ir in each complex are covered with η-Cp* and on the remaining three, donor atoms present are: N, S/Se and C/Cl, resulting in a piano-stool structure. The moisture and air insensitive 1-4 act as efficient catalysts under mild conditions for base free N-alkylation of amines with benzyl alcohols and transfer hydrogenation (TH) of aldehydes/ketones. The optimum loading of 1-4 as a catalyst is 0.1-0.5 mol% for both the activations. The best reaction temperature is 80 °C for transfer hydrogenation and 100 °C for N-alkylation. The mercury poisoning test supports a homogeneous pathway for both the reactions catalyzed by 1-4. The two catalytic processes are most efficient with 3 followed by 4 > 1 > 2. The mechanism proposed on the basis of HR-MS of the reaction mixtures of the two catalytic processes taken after 1-2 h involves the formation of an alkoxy and hydrido species. The real catalytic species proposed in the case of iridacycles results due to the loss of the Cp* ring.

Ultra-small palladium nano-particles synthesized using bulky S/Se and N donor ligands as a stabilizer: application as catalysts for Suzuki–Miyaura coupling

“…The syntheses of L1 0 and L2 0 have been carried out using a method similar to reported procedures. 24 Ligands L1 and L2 have been synthesized using a methodology shown in Scheme 1. Ligands L1 and L2 have been characterized using 1 H and 13 C { 1 H} NMR techniques.…”

“…[22][23][24][25][26][27][28][29] These have shown good to excellent catalytic activity for the coupling of aryl halides. [22][23][24][25][26][27][28][29] Presence of neutral chalcogen donor in stabilizers affects the catalytic efficiency, composition, size, recyclability, and dispersion of the nanoparticles to a great extent. 30,31 The use of organochalcogen ligands in the development of molecular catalysts has been studied in a variety of cases.…”

“…30,31 The use of organochalcogen ligands in the development of molecular catalysts has been studied in a variety of cases. [22][23][24][25][26][27][28][29] However, the use of such ligands in the stabilization of nanoparticles is limited. 30,31 To the best of our knowledge, no such compound containing a combination of hard-hard or hard-so donors have been reported for this purpose.…”

Supramolecular aggregation patterns featuring Se⋯N secondary-bonding interactions in mono-nuclear selenium compounds: A comparison with their congeners

“…11d, and 65 [107], with Se … N π-hole type interactions suggested for the latter two chains. In 66 [108], the contact involves an imine-nitrogen atom and in 67 [109], the Se … N π-hole type interaction involves an uracil-nitrogen atom. While all preceding examples involve diorganoselenium species, in 68 [110], a bent CS donor set is apparent for selenium, with the resulting chain shown in Fig.…”

Ruthenacycles and Iridacycles as Transfer Hydrogenation Catalysts

“…Singh and coworkers reacted a bidentate imino thio (or seleno) ligand with [Ir(Cp*)Cl 2 ] 2 in methanol at room temperature and isolated the complexes Ia and Ib in good yields ( Scheme 57 ) [ 81 ]. If the same reaction was performed at 50 °C in the presence of sodium acetate, the iridacycles 87a and 87b were obtained.…”