Correlated ab initio calculations of one-bond 31 P77 Se and 31 P125 Te spin-spin coupling constants in a series of PSe and PTe systems accounting for relativistic effects (part 2)

On the Edge of the Known: Extremely Electron-Rich (Di)Carboranyl Phosphines

The syntheses of the first B9-connected carboranylphosphines (B9-Phos) featuring two carboranyl moieties as well as access to B9-Phos ligands with bulky electron-donating substituents, previously deemed unattainable, is reported. The electrochemical properties of the B9-Phos ligands were investigated, revealing the ability of the mesityl derivatives to form stabilized phosphoniumyl radical cations. The B9-Phos ligands display an extremely electron-releasing character surpassing that of alkyl phosphines and commonly used N-heterocyclic carbenes. This is demonstrated by their very small Tolman electronic parameters (TEPs) as well as extremely low P-Se coupling constants. Cone angles and buried volumes attest to the high steric demand exerted by the (di)carboranyl phosphines. The dicarboranyl phosphine Au^I complexes show superior catalytic performance in the hydroamination of alkynes compared to the monocarboranyl phosphine analogs.

New pecJ-n (n = 1, 2) Basis Sets for High-Quality Calculations of Indirect Nuclear Spin–Spin Coupling Constants Involving 31P and 29Si: The Advanced PEC Method

In this paper, we presented new J-oriented basis sets, pecJ-n (n = 1, 2), for phosphorus and silicon, purposed for the high-quality correlated calculations of the NMR spin–spin coupling constants involving these nuclei. The pecJ-n basis sets were generated using the modified version of the property-energy consistent (PEC) method, which was introduced in our earlier paper. The modifications applied to the original PEC procedure increased the overall accuracy and robustness of the generated basis sets in relation to the diversity of electronic systems. Our new basis sets were successfully tested on a great number of spin–spin coupling constants, involving phosphorus or/and silicon, calculated within the SOPPA(CCSD) method. In general, it was found that our new pecJ-1 and pecJ-2 basis sets are very efficient, providing the overall accuracy that can be characterized by MAEs of about 3.80 and 1.98 Hz, respectively, against the benchmark data obtained with a large dyall.aae4z⁺ basis set of quadruple-ζ quality.

The aug-cc-pVTZ-J basis set for the p-block fourth-row elements Ga, Ge, As, Se, and Br

The aug-cc-pVTZ-J basis set family is extended to include the fourth-row p-block elements Ga, Ge, As, Se, and Br. We use the established approach outlined by Sauer and coworkers (J. Chem. Phys. 115, 1324 [2001], J. Chem. Phys. 133, 054308 [2010], J. Chem. Theory Comput. 7, 4070 [2011], and J. Chem. Theory Comput. 7, 4077 [2011]) where the completely uncontracted aug-cc-pVTZ basis set is saturated with tight s-, p-, d-, and f-functions to form the aug-cc-pVTZ-Juc basis set for the tested elements. The saturation is carried out on the simplest hydrides possible for the tested elements GaH, GeH₄ , AsH₃ , H₂ Se, and HBr until an improvement is less than 0.01% for all s-, p-, and d-functions added. f-Functions are added to an improvement less than or equal to 1.0% due to the computational expense these functions add. The saturated aug-cc-pVTZ-Juc (26s16p12d5f) is then recontracted using the molecular orbital coefficients from self-consistent field calculations on the simple hydrides to improve computational efficiency. During contraction of the basis set, we observe that the linear hydrogen bromide molecule has a slower convergence than the other tested molecules which sets a limit on the accuracy obtained. All calculations with the contracted aug-cc-pVTZ-J [17s10p7d5f] gives results that are within 1.0% of the uncontracted results at considerable computational savings.

Making Aromatic Phosphorus Heterocycles More Basic and Nucleophilic: Synthesis, Characterization and Reactivity of the First Phosphinine Selenide

The synthesis and isolation of a phosphinine selenide was achieved for the first time by reacting red selenium with 2,6-bis(trimethylsilyl)phosphinine. The rather large coupling constant of ¹ J_P,Se =883 Hz is in line with a P-Se bond of high s-character. The σ-electron donating Me₃ Si-substituents significantly increase the energy of the phosphorus lone pair and hence its basicity, making the heterocycle considerably more basic and nucleophilic than the unsubstituted phosphinine C₅ H₅ P, as confirmed by the calculated gas phase basicities. NBO calculations further reveal that the lone pairs of the selenium atom are stabilized through donor-acceptor interactions with antibonding orbitals of the aromatic ring. The novel phosphinine selenide shows a distinct reactivity towards hexafluoro-2-butyne, Au(I)Cl as well as ⁱ PrOH. Our results pave the way for new perspectives in the chemistry of phosphorus in low coordination.