Organic Azide and Auxiliary-Ligand-Free Complexes of Coinage Metals Supported by N-Heterocyclic Carbenes

Abstract

Organic azide complexes of copper­(I) and silver­(I), [(SIPr)­CuN­(1-Ad)­NN]­[SbF6], [(SIPr)­CuN­(2-Ad)­NN]­[SbF6], [(SIPr)­CuN­(Cy)­NN]­[SbF6], and [(SIPr)­AgN­(1-Ad)­NN]­[SbF6] have been synthesized by using Ag­[SbF6] and the corresponding organic azides with (SIPr)­CuBr and (SIPr)­AgCl (SIPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolin-2-ylidene). The copper and silver organic azide complexes were characterized by various spectroscopic techniques and X-ray crystallography. Group trends of isoleptic Cu­(I), Ag­(I), and Au­(I) organic azide complexes are presented on the basis of experimental data and a detailed computational study. The νasym(N3) values of the metal-bound 1-AdNNN in [(SIPr)­MN­(1-Ad)­NN]+ follow the order Ag < Cu < Au. DFT calculations show that gold­(I) forms the strongest bond with 1-AdNNN in this series, while silver has the weakest interaction. Furthermore, auxiliary ligand free coinage metal N-heterocyclic carbene complexes, [(SIPr)­M]­[SbF6], have been synthesized via metathesis reactions of (SIPr)­MCl (M = Cu, Ag, Au) with Ag­[SbF6]. X-ray crystal structures of dinuclear [(SIPr)­Ag]2[SbF6]2 and [(SIPr)­Au]2[SbF6]2 are also reported. They show close metallophilic contacts. [(SIPr)­Au]2[SbF6]2 reacts with OEt2, SMe2, and CN t Bu to afford [(SIPr)­Au­(OEt2)]­[SbF6], [(SIPr)­Au­(SMe2)]­[SbF6], and [(SIPr)­Au­(CN t Bu)]­[SbF6] adducts, respectively.

Mercury(II) Complexes of Anionic N-Heterocyclic Carbene Ligands: Steric Effects of the Backbone Substituent

“…Furthermore, to our knowledge, mercury(II) complexes of anionic N -herterocyclic carbene ligands, such as maloNHC, have not been investigated. As a continuation of our interest in the NHCs and their metal chemistry [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ], we have set out to probe the use of anionic N -heterocyclic carbene ligands in mercury chemistry. In particular, we describe the synthesis and spectroscopic data of three new mercury(II) complexes ( Figure 1 ), (Me-maloNHC Dipp )HgCl ( 1b ), ( t -Bu-maloNHC Dipp )HgCl ( 2b ) and ( t -Bu-maloNHC Dipp )HgMe ( 2c ), involving a bulkier maloNHC.…”

A Digallane Gold Complex with a 12-Electron Auride Center: Synthesis and Computational Studies

“…The aryl substituents (Ar iPr4 ) on gallium atoms have their ortho -phenyl groups extending to the front (Au) and back (Cl) of the AuGa 2 Cl core (Figure ). On the gold side, the Au–C aryl distances range from 2.973(6) to 3.346(6) Å between the Au and ring A, slightly shorter than those between the Au and ring B (3.300(6)–3.685 Å, Table ) indicating weak metal–arene interactions. ,− Covalently bound alkene and alkyne π complexes of Au­(I) typically have Au–C distances shorter than 2.4 Å. − These Au–aryl weak interactions in 2 and the steric bulk of Ar iPr4 groups prevent rotation along the Ga–C bond in solution, accounting for the four distinct signals of the isopropyl −CH 3 groups observed in the 1 H NMR spectrum.…”

An Isolable Azide Adduct of Titanium(II) Follows Bifurcated Deazotation Pathways to an Imide

“…The formation of a transition metal imide complex via extrusion of dinitrogen from an organic azide is a classic reaction that continues to garner interest in the coordination chemistry community − but also underpins organic transformations such as nitrene homocoupling to azoarenes, , isocyanide–nitrene coupling to carbodiimides, , alkene–nitrene coupling to aziridines, − [2 + 2 + 1] alkyne–nitrene coupling to pyrroles, − and C–H bond amination. − The oxo-wall, introduced by Gray and Ballhausen, − delimits the electronic structure of stable oxo and imide complexes: In tetragonal geometries, valence electron counts beyond d 2 lead to the occupation of M–N π* orbitals, which destabilizes the MN triple bonds, whereas valence electron counts up to d 4 are stable in low-coordinate geometries. A reverse situation exists for organoazide adducts, which gain stability when valence electron counts exceed d 4 / d 6 ; these complexes prevail among late transition metals. ,,,− The conversion of an organoazide into an imide complex, although a seemingly simple metal-promoted deazotation reaction, has only been studied mechanistically by few groups. In 1995, Bergman and Proulx , and Cummins et al isolated γ-organoazide adducts of the early transition metal fragments Ta III and V III (we label organoazides starting from the organic substituent: RN α N β N γ ).…”