Reactions of Mesityl Azide with Ferrocene-Based N-Heterocyclic Germylenes, Stannylenes and Plumbylenes, Including PPh2 -Functionalised Congeners

Mechanistic Insights into the Reactivity and Activation Barrier Origins for CO2 Capture by Heavy Group-14 Imine Analogues

Using M06-2X-D3/def2-TZVP, the [2 + 2] cycloaddition reactions of carbon dioxide with the heavy imine analogues G14=N-Rea (G14 = Group 14 element) were investigated. The theoretical evidence reveals that the nature of the doubly bonded G14=N moiety in heavy imine analogues, G14=N-Rea (L1L2G14=N-L3), is characterized by the electron-sharing interaction between triplet L1L2G14 and triplet N-L3 fragments. Based on our theoretical studies, except for the carbon-based imine, all four heavy imine analogues with Si=N, Ge=N, Sn=N, and Pb=N groups can easily engage in [2 + 2] cycloaddition reactions with CO2. Energy decomposition analysis-natural orbitals for chemical valence analyses and the FMO theory strongly suggest that in the CO2 capture reaction by heavy imine analogues G14=N-Rea, the primary bonding interaction is the occupied p-π orbital (G14=N-Rea) → vacant p-π* orbital (CO2) interaction, instead of the empty p-π* orbital (G14=N-Rea) ← filled p-π orbital (CO2) interaction. The activation barrier of the CO2 capture reactions by G14=N-Rea molecules is primarily determined by the deformation energy of CO2. Shaik's valence bond state correlation diagram model, used to rationalize the computed results, indicates that the singlet-triplet energy splitting of G14=N-Rea is a key factor in determining the reaction barrier for the current CO2 capture reactions.

An isolable stannaimine and its cycloaddition/metathesis reactions with carbon dioxide

An N-heterocyclic stannylene :Sn(NONAd) (NONAd = [O(SiMe2NAd)2]2-, Ad = 1-adamantyl), reacts rapidly with 2,4,6-tricyclohexylphenyl azide (TCHP)N3, affording a stannaimine, (NONAd)SnN(TCHP). Solutions of (NONAd)SnN(TCHP) react immediately with carbon dioxide (CO2) to give a [2+2]-cycloaddition product, which, upon heating, subsequently engages in a metathesis process to give [Sn(NONAd)(μ-O)]2 and the bulky isocyanate, (TCHP)NCO.

Synthesis and Reactivity of N-Heterocyclic Carbene Coordinated Formal Germanimidoyl-Phosphinidenes

Treatment of N-heterocyclic carbene (NHC) ligated germylidenylphosphinidene MsFluidtBu-GeP(NHCiPr) (where MsFluidtBu is a bulky hydrindacene substituent, and NHCiPr is 1,3-diisopropyl-4,5-dimethyl-imidazolin-2-ylidene) with mesityl azide and 4-tertbutylphenyl azide afforded NHC coordinated formal germanimidoyl-phosphinidenes, which represent the first compounds bearing both Ge═N double bond and phosphinidene functionalities. Studies of the chemical properties revealed that the reactions preferred to occur at the Ge═N double bond, which underwent [2 + 2] cycloadditions with CO2 and ethyl isocyanate, and coordinated with coinage metals through the nitrogen atom.

A complete series of N-heterocyclic tetrylenes (Si-Pb) with a 1,1'-ferrocenediyl backbone enabled by 1,3,2-diazaborolyl N-substituents

The use of bulky 1,3,2-diazaborolyl N-substituents has allowed the synthesis of the complete series of ferrocene-based N-heterocyclic tetrylenes fc[(N{B})2E] (fc = 1,1'-ferrocenediyl, {B} = (HCNC6H3-2,6-iPr2)2B, E = Si-Pb). The silylene fc[(N{B})2Si] is inert towards NH3, CO2 or N2O under ambient conditions and thus significantly less reactive than the N-aryl homologue fc[(NC6H3-2,6-iPr2)2Si]. In accord with its higher reactivity, computational results indicate a more pronounced ambiphilicity of fc[(NC6H3-2,6-iPr2)2Si]. Our computational investigation of the model compound fc[(NBMe2)2Si] suggests that silylenes of this type may be superior to fc[(NC6H3-2,6-iPr2)2Si] in terms of ambiphilicity.

Reactivity of Cyclic (Alkyl)(amino)germylene towards Copper(I) and Gold(I) Complexes

The reactions of cyclic (alkyl)(amino)germylenes (CAAGe) with copper(I) and gold(I) complexes were investigated. CAAGe (1) reacts with CuBr(SMe2 ) leading to a tetrameric germylene complex [CAAGeCuBr]4 (2), whereas CAAGe (3) undergoes Au-Cl bond insertion with LAuCl (L=phosphine or N-heterocyclic carbene) to afford germanium gold(I) complexes (5 and 6). Chlorine abstraction of 6 gives the cationic germylene gold(I) complex 7.

Reactions of main group compounds with azides forming organic nitrogen-containing species

Since the seminal discovery of phenyl azide by Grieß in 1864, a variety of organic azides (R-N3) have been developed and extensively studied. The amenability of azides to a number of reactions has expanded their utility as building blocks not only in organic synthesis but also in bioorthogonal chemistry and materials science. Over the decades, it has been demonstrated that the reactions of main group compounds with azides lead to diverse N-containing main group molecules. In view of the pronounced progress in this area, this review summarizes the reactions of main group compounds with azides, emphatically introducing their reaction patterns and mechanisms. The reactions of forming inorganic nitrogen species are not included in this review.

Germanium Complexes with ONO Tridentate Ligands: O-H Bond Activation Control According to DFT Calculations

Polydentate ligands are used for thermodynamic stabilization of tetrylenes-low-valent derivatives of Group 14 elements (E = Si, Ge, Sn, Pb). This work shows by DFT calculations how the structure (the presence or absence of substituents) and type (alcoholic, Alk, or phenolic, Ar) of tridentate ligands 2,6-pyridinobis(1,2-ethanols) [^AlkONO^R]H₂ and 2,6-pyridinobis(1,2-phenols) [^ArONO^R]H₂ (R = H, Me) may affect the reactivity or stabilization of tetrylene, indicating the unprecedented behavior of Main Group elements. This enables the unique control of the type of the occurring reaction. We found that unhindered [ONO^H]H₂ ligands predominantly led to hypercoordinated bis-liganded {[ONO^H]}₂Ge complexes, where an E(+2) intermediate was inserted into the ArO-H bond with subsequent H₂ evolution. In contrast, substituted [ONO^Me]H₂ ligands gave [ONO^Me]Ge: germylenes, which may be regarded as kinetic stabilized products; their transformation into E(+4) species is also thermodynamically favorable. The latter reaction is more probable for phenolic [^ArONO]H₂ ligands than for alcoholic [^AlkONO]H₂. The thermodynamics and possible intermediates of the reactions were also investigated.

A germanimidoyl chloride: synthesis, characterization and reactivity

The first germanimidoyl chloride M^sFluind^tBu-Ge(Cl)NMes (2, where M^sFluind^tBu is a bulky hydrindacene skeleton) was synthesized through the reaction of M^sFluind^tBu-GeCl (1) and mesityl azide (MesN₃). In contrast, treatment of 1 with a less bulky azide ArN₃ (Ar = 4-^tBuC₆H₄) produced a germatetrazole chloride M^sFluind^tBu-Ge(Cl)N₄Ar₂ (3), and a salt [M^sFluind^tBu-GeN₄Ar₂]⁺[BAr^F₄]^- (4; Ar^F = 3,5-(CF₃)₂C₆H₃) followed by chloride abstraction with NaBAr^F₄, both bearing a five-membered GeN₄ ring. Functionalization of 2 with Ar'Li (Ar' = 3,5-^tBu₂C₆H₃) or MeLi furnished a germanimine M^sFluind^tBu-Ge(Ar')NMes (5) or an amide lithium salt M^sFluind^tBu-Ge(Me)₂-N(Mes)Li(thf) (6).