New N -heterocyclic plumbylenes (NHPbs) and their complexes with palladium and platinum by DFT
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ORIGINAL RESEARCH
New N-heterocyclic plumbylenes (NHPbs) and their complexes with palladium and platinum by DFT Nazanin Mohebi 1 & Mohamad Zaman Kassaee 1 Received: 18 March 2020 / Accepted: 28 July 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Following our quest for stable group 14 divalents, novel N-heterocyclic plumbylenes (NHPbs), composed of 2,4,6cycloheptatriene-2,7-diazaplumbylene (1), benzannulated with one (2), two (3, 4), and three benzene rings (5), are compared and contrasted at the density functional theory level. Results indicate that in going from 1 to 5, the absolute values of singlettriplet energy gap (ΔEs-t) and band gap (ΔEH-L) increase, while nucleophilicity (N), electrophilicity (ω), and chemical potential (μ) decrease. The most benzannulated structure, ([a,c,e]tribenzo)cyclohepta-2,7-diazaplumbylene (5), turns out as the most stable plumbylene for showing the most negative ΔEs-t of − 194.94 kcal/mol. Furthermore, 5 shows the highest ΔEH-L (− 2.75 eV), with the lowest N (1.31 eV), ω (8.20 eV), μ (− 7.15 eV), and charge of (+ 0.736) on Pb atom. Isodesmic reactions of 1-5 with common transition metal halides, MX2, give forty new metal complexes of 1M-X-5M-X, where M = Pt and Pd, while X = F, Cl, Br, and I. Their complexation energies (ΔECom) indicate that 1-5 are rather stronger ligands with Pt than Pd. Bader’s atoms in molecules (AIM) and NBO analyses show the partial covalent and partial electrostatic nature of Pb-M bonds. Keywords Plumbylene . Platinum . Palladium . Halogen . Complexation . DFT
Introduction The heavier divalent analogs of carbenes are represented by silylenes, germylenes, stannylenes, and to a lesser extent plumbylenes [1]. In contrast to carbenes, the reactivity of its heavier analogs is usually dominated by their higher electrophilicity [2–6]. This property makes germylenes and stannylenes as good Lewis acid catalysts in many catalytic reactions, while plumbylenes are less considered [7–10]. The umpolung of such reactivity leads to the discovery of the unusual plumbylene-transition metal complexes [11–13]. The first stable N-heterocyclic carbene and its carbenic analogs are also known as Arduengo-type carbenes [14]. Replacing divalent C with divalent heavier
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11224-020-01603-y) contains supplementary material, which is available to authorized users. * Mohamad Zaman Kassaee [email protected] 1
Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
group 14 atoms gives another class of Arduengo-type analogs which encompasses powerful ligands in organometallic catalytic reactions. Up to now, the Arduengo-type carbenes [15], silylenes [16], germylenes [17], stannylenes [18], and plumbylenes [19] have been synthesized. The first stable benzannulated N-heterocyclic plumbylene (NHPbs) was synthesized by Hahn et al. in 2008 [20]. The application of N-heterocyclic carbene (NHC) catalysts in the synthesis of polyl
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