The Template Effect of Palladium(II): Synthesis, Characterization, and Crystal Structures of 2,4‐Substituted 1,3,5‐Triazapentadienatopalladium(II) Complexes

Abstract

The reaction of LiN(SiMe 3 ) 2 with two equivalents of 2-, 3-, or 4-cyanopyridine followed by the addition of half an equivalent of [PdCl 2 (PhCN) 2 ] gives neutral 1,3,5-triazapentadienato complexes of the general formula [Pd{HNC(Py)NC(Py)NH} 2 ] (Py = 2-pyridyl 1, 3-pyridyl 2, 4-pyridyl 3). When the above reaction was carried out with benzonitrile and then 3-or 4-cyanopyridine was added followed by half an equivalent of [PdCl 2 (PhCN) 2 ] neutral unsymmetrical 1,3,5-triazapentadienato complexes of the general formula [Pd{HNC(Ph)-NC(Py)NH} 2 ] (Py = 3-pyridyl 4, 4-pyridyl 5) were obtained. When LiN(SiMe 3 ) 2 was treated with one equivalent of benzonitrile in THF, followed by the addition of a quarter of an equivalent of anhydrous palladium chloride and workup in air, the trinuclear complex tetrakis(benzamidinato)bis(2,4-di-

PdII‐Promoted Single‐Pot Template Transformations of Benzonitriles, Cyanoguanidine and Sodium Dicyanamide with the Formation of Symmetrical and Asymmetrical (1,3,5‐Triazapentadienate)palladium(II) Complexes

“…The IR spectra of 4a-4d show no ν(CϵN) bands and display one or two strong vibrational bands for the C=N imine moieties within the 1600-1700 cm -1 range, which is typical for tap-Pd II complexes, [10,16] while the ν(N-H) vibrations emerge in the 3300-3400 cm -1 range. The 1 H and 13 C NMR spectra of these complexes show more than one set of signals, most probably due the presence of different isomers.…”

“…[10] The 1 H and 13 C NMR spectra of 6a-6d show, in almost all cases, more than one set of signals conceivably due the presence of different isomers in solution. For example, in the 1 H NMR spectrum of complex 6a, the protons of the methoxy group (OCH 3 ) appear as a multiplet within the δ = 3.66-3.75 ppm range, while the 13 C NMR spectrum shows five signals in the δ = 54.9-55.7 ppm range for the methoxy carbon (OCH 3 ) and also five signals in the δ = 160.9-162.0 ppm range due to the imino group (C=NH).…”

“…phenyls, and can be synthesized by the reaction of primary amines, RNH 2 , with the fluorinated imine C 3 F 7 -CF=N-C 4 F 9 [6] or by the Ley and Muller method [23] where amidine is treated with an N-imidoyl chloride. [3][4][5]12] Another route to tap-Pd complexes involves template transformations of cyanopyridines [10,16] through lithium amidinate, which is produced in situ from LiN(SiMe 3 ) 2 [10] or via an oxime-mediated process. [16] In the latter case, the synthesized complexes were shown [16] to display catalytic activity towards Suzuki-Miyaura and Heck cross-coupling reactions.…”

“…[17][18][19][20] Until now only copper, nickel and platinum ions have been studied in these transformation reactions and no data on palladium(II)-mediated transformations have been reported, irrespective of the potential ability of Pd II to form tap complexes [3,5,6,10,12,16] and its expected behavioural similarity to that of Pt II in promoting nucleophilic addition reactions with substrates containing the CϵN group, namely organonitriles. [24][25][26][27] Thus, one can conclude that the template conversions of CϵN-containing reagents to tap ligands bound to Pd II cen-ters deserve to be explored further as a convenient route to new tap-palladium(II) complexes.…”

Gold(I) Complexes [N{(C3F7)C(Dipp)N}2]AuL (L = Ethylene, tert‐Butyl Isocyanide, Tetrahydrothiophene, Triphenylphosphine) and Different Triazapentadienyl Ligand Coordination Modes

“…They have been used very successfully as supporting ligands for most of the metals of the d‐block. 1,3,5‐Triazapentadienyl ligands ( 2 ) are tri‐nitrogen analogues of the 1,5‐diazapentadienyl systems but they have received less attention (Figure ) . We have been interested in the development of this promising class of ligands, in particular the fluorinated ligand versions, and their use in main‐group and transition‐metal chemistry as supporting ligands , , , .…”