RESUMEN
The hydrostannylation of white phosphorus (P4) allows this crucial industrial precursor to be easily transformed into useful P1 products via direct, 'one pot' (or even catalytic) procedures. However, a thorough mechanistic understanding of this transformation has remained elusive, hindering attempts to use this rare example of successful, direct P4 functionalization as a model for further reaction development. Here, we provide a deep and generalizable mechanistic picture for P4 hydrostannylation by combining DFT calculations with in situ31P NMR reaction monitoring and kinetic trapping of previously unobservable reaction intermediates using bulky tin hydrides. The results offer important insights into both how this reaction proceeds and why it is successful and provide implicit guidelines for future research in the field of P4 activation.
RESUMEN
Nitrenes are a highly reactive, yet fundamental compound class. They possess a mono-valent nitrogen atom and usually a short life span, typically in the nanosecond range. Here, we report on the synthesis of a stable nitrene by photolysis of the arylazide MSFluindN3 (1), which gave rise to the quantitative formation of the arylnitrene MSFluindN (2) (MSFluind = dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9''-fluorene]), that remains unchanged for at least 3 days when stored under argon atmosphere at room temperature. The extraordinary life span permitted the full characterization of 2 by single crystal x-ray crystallography, EPR spectroscopy and SQUID magnetometry, which supported a triplet ground state. Theoretical simulations suggest in addition to the kinetic stabilization conferred by the bulky MSFluind aryl substituent, that electron delocalization across the central aromatic ring contributes to the electron stabilization of 2.
RESUMEN
The kinetically stabilized group 14 cations [RindEMe2][B(C6F5)4] (E = Si, Sn, Pb) were prepared and fully characterized (Rind = dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9''-fluorene). The deshielded heteronuclear NMR chemical shifts (δ(29Si) = 160.4, δ(119Sn) = 619.9, δ(207Pb) = 1549.5) are indicative of the low coordination numbers.
Asunto(s)
Fluorenos , Plomo , Espectroscopía de Resonancia Magnética , CationesRESUMEN
The newly prepared and fully characterized stibenium and bismuthenium ions [Rind MesE]+ (E=Sb, Bi; Rind =dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9''-fluorene) were rigorously compared to the previously communicated phosphenium and arsenium ions (E=P, As) as well as the bis(m-terphenyl) pnictogenium ions [(2,6-Mes2 C6 H3 )2 E]+ (E=Sb, Bi). It is demonstrated that the choice of the aryl substituents dramatically effects the molecular structures (e. g. the primary E-C bond lengths) and the electronic structures (e. g. the energy of the LUMOs).
RESUMEN
The synthesis and reactivity of the heavier group 13 phosphaketene complexes (2,6-Mes2C6H3)2EPCO (1, E = Ga; 2, E = In) were reported. The reaction of 1 and 2 with 1,2,3,4-tetramethylimidazolin-2-ylidene, IMe4, gave rise to the formation of (2,6-Mes2C6H3)2EP(O)C(IMe4) (3, E = Ga; 4 E = In; Mes = mesityl). Subsequent addition of elemental tellurium proceeded via insertion into the E-P bond and provided (2,6-Mes2C6H3)2ETeP(O)C(IMe4) (5, E = Ga; 6, E = In) comprising five-membered ETePCO-heterocycles. Compounds 1-6 were fully characterized by X-ray crystallography and heteronuclear NMR spectroscopy. The electronic structures of 1-6 were studied by DFT calculations and analyses of a complementary set of real-space bonding indicators (AIM, ELI-D, NCI) derived from the electron and pair densities, with focus on the bond characteristics of the PCO fragment.