Effect of a κ¹-Bonded-M-1,2,3-triazole (M = Co, Ru) on the Structure and Reactivity of Group 6 Alkoxy (Fischer) Carbenes

Abstract

The [3 + 2] cycloaddition of two different metal-bound azides, [(Mecyclam)Co(N)]ClO and (η-CH)(dppe)Ru(N), (dppe = PhPCHCHPPh) with Cr(0) and W(0) (ethoxy)(alkynyl) Fischer carbenes has been efficiently used for the preparation of polymetallic metal-carbene complexes. The presence of the κ-bonded metal triazole causes a significant influence on the electronic properties, structure, and reactivity of this new class of Fischer alkoxycarbenes. For the Ru(II) derivatives, their chemical behavior is considerably influenced by the interaction of the (η-CH)(dppe)Ru-triazole moiety with the empty p-carbene orbital that provokes a noticeable decrease in the electrophilicity of the M═C carbon (manifested by the shielding of the C NMR chemical shifts). In turn, in the Co(II) derivatives, the incorporation of the (Mecyclam)Co moiety diminishes the aromaticity of the triazole ring and has a marked effect on the energy and distribution of the LUSO orbital, mostly resident on the Co(II) fragment. The almost negligible participation of the carbene moiety in the LUSO makes this position unable to react with nucleophiles. The reactions reported in this work constitute the first examples of [3 + 2] cycloaddition of azides and alkynyl Fischer carbene complexes in solution.

Synthesis of Triazole Derivatives of Levoglucosenone As Promising Anticancer Agents: Effective Exploration of the Chemical Space through retro-aza-Michael//aza-Michael Isomerizations

“…This serendipitous base-catalyzed isomerization of 4a to 7a not only provided a useful alternative to explore more deeply the chemical space in our preliminary screening of levoglucosenone derivatives as anticancer compounds but also represented a novel synthetic strategy for the preparation of N2-substituted 1,2,3-triazoles, for which extensive research has been conducted in the recent past . In this regard, it is important to note that the isomerization of N1-substituted 1,2,3-triazolyl-ketones to the corresponding N2-substituted counterparts has been covered by Sharpless and co-workers, whereas the isolation of N2-substituted triazoles derived from metallic azides and alkynes has also been studied. − However, the lack of reports on such isomerization when dealing with disubstituted metal-free triazole moieties motivated us to perform a comprehensive study on this system.…”

Isostructural Series of Ni(II), Pd(II), Pt(II), and Au(III) Azido Complexes with a N^C^N Pincer Ligand to Elucidate Trends in the iClick Reaction Kinetics and Structural Parameters of the Triazolato Products

“…While the scope of alkynes that easily undergo the iClick reaction at room temperature is continuously expanding, , only a limited number of metal-azido building blocks have been explored so far, with those derived from the linear Au­(I) azido complex [Au­(N 3 )­(PPh 3 )], as originally described by Veige, or based on a [Ru­(N 3 )­(η 6 -arene)] motif being among the most frequently used ones. However, beyond a comparison of isoelectronic and isostructural Mo/W and Pd/Pt “pairs,” ,, little is known about the effect of metal replacement along a full group of the transition metals from 3d to 5d, and there is also a notable under-representation of earth-abundant 3d metals among the reported iClick reactions. , Furthermore, when trying to access a Au­(III) azido complex with 2,2′:6′,2″-terpyridine (terpy), we unexpectedly isolated [Au­(N 3 ) 3 (terpy-κ 1 N 1 )] instead of the intended [Au­(N 3 )­(terpy-κ 3 - N 1,1 ′ ,1 ″ )] 2+ building block . Although Paul and Nag described a pair of Ni­(II) and Pd­(II) complexes with a tridentate N^N^S chelating ligand, the potential extension of this chemistry to the related Pt­(II) and Au­(III) compounds is questionable.…”

Understanding the Reactivity of Group 6 Metal (M = Cr, W) Alkynyl Fischer Carbene Complexes with Multi‐Reactive Masked Dienes

“…Owing to the participation of the metal in the cycloaddition process, not only [4+2] [2e] and [3+2], [7] but also higher-order cycloadditions have been reported. [8] Pursuing our studies on the reactivity of conjugated Fischer carbene complexes with nucleophiles able to generate new types of structures having new properties, [5,9] we considered that bidentate dienes such as anthrone (1) could be interesting reagents to study the competition between 1,2-and 1,4-additions as well as [4+2] cycloaddition reactions. Anthrone (1) is a highly reactive masked diene [10] that reacts through an aromatization/dearomatization pathway via the anthrolate anion (2), a bidentate charged species that could act as an O or C nucleophile (Scheme 1).…”