M. I. Povolotskii

Ab initio calculation of NMR shielding in phosphaalkenes X—PCY2

31P and 13C chemical shielding values, σiso, were calculated for a series of phosphaalkenes X—PCY2 with a variety of substituents such as XH, CH3, F, Cl, Br, OH, NH2, PH2, SiH3, CN and YH, CH3, NH2, SiH3, using the GIAO procedure at the RHF/6–311 + G(d,p) and RHF/6–311 + G(2d,2p) levels. The trends governing the variation of the geometric parameters and the natural charges and Wiberg indices are discussed. The contributions of the various molecular orbitals in 31P and 13C chemical shielding in the phosphaalkene H—PCH2 and ethylene, respectively, were compared. The 31P chemical shielding variation was determined by mixing of the ground and excited states. Good correlations were found between the experimentally measured δ C and δ P values in the series X′—PC(SiMe3)2 and those calculated for the series X—PC(SiH3)2, but on average the calculated 31P chemical shifts seem to be overestimated. A comparison with the calculated data (at the same level) for X—PC(SiMe3)2 indicates only a partial improvement. The 13C chemical shifts in phophaalkenes correlate within the subseries X—PCH2, X—PC(CH3)2 and X—PC(SiH3)2 with the charge variation at the corresponding carbon atom, reflecting the X—(PC) π‐mesomeric interactions. The absence of the corresponding correlation with all phophaalkenes investigated manifestates limited validity of this generally used approach. Copyright

Synthesis of Hexaisopropyltriamidephosphite: Myth or Reality?

Results of our work allowed us to assert that the methods for synthesis of triamide (i-Pr2N)3P 1 described are wrong.1–4 It was shown that diamidohalogenphosphites (i-Pr2N)2PHlg (Hlg = Cl,Br,I) do not react with di(isopropyl)amine even under harsh conditions such as heating up to 240◦C in various solvents. At the same time, less sterically hindered phosphenium cation 2 easily react with di(isopropyl)amine, affording diphosphine 5 instead of the expected triamide 1. The diphosphine 5 is also formed in the reaction of the phosphenium cation 2 with ketimine i-PrN = CMe2, with the reaction running via formation of monophosphine 3.

13C, 15N and 31P NMR Investigation of P-Substituted N-2,4,6-Tris(tert-butyl)- phenyliminophosphines

A large series of (E)‐ and (Z)‐iminophosphines, Mes*νNξPνX [X = NR2, OR, Alk, Ar, SR, PR2, Hal; Mes* = 2,4,6‐tris(tert‐butyl)phenyl], was investigated by 13C, 15N and 31P NMR spectroscopy. The 13C NMR chemical shifts of methyl groups of the o‐tert‐butyl substituents, and also the carbon–phosphorus coupling of the meta‐ and para‐carbons in the aromatic moiety, were shown to be possible criteria for the assignment of the E‐ or Z‐configuration of the iminophosphine. Basic rules are enumerated for the determination of configuration in the series considered. The variation of aromatic 13C nuclei shielding is considered to be electrostatic (π‐inductive) in nature.

Molecular and electronic structure of 1,3,2-diazaphosphinine derivatives

GRAPHICAL ABSTRACT ABSTRACT Structure of 1,3,2-diazaphosphinine heterocyclic system was studied using quantum chemical calculations and X-ray diffraction method for one derivative. It was found that two P–N single bonds were different in their nature: one of them turned out to be significantly shorter and stronger, whereas the other one is longer and more diffused. The found effect is strengthened by π-donor substituents. The effect was interpreted by equilibrium of Lewis structures and analyzing the charge distribution by the NBO approach. The observed effect can be considered as the special form of π-conjugation in the heterocycles with the phosphorus (V) atom included.

Exocyclic P--Hlg Bond Ionization in 1,3,2-Oxazaphospholines

The x-ray and spectral data allow us to suppose the existence of equilibrium between 1,3,2-oxazaphospholines with highly polarized P Hlg bonds and their ionization products in solvents with high dielectric constant. In CDCl3 solution compounds I a–d virtually don’t display ionization signs, but iodide I d dissociates in (Me2N)3PO solution up to 80–90%. The addition of Lewis acids to the solutions of halogenides I a,b in CDCl3 leads to the shift of equilibrium toward the ionized form. Salts II a,b were isolated as pure crystals after evaporation of reaction solutions.

P-Metalated Phosphaalkenes

Structure and reactivity of metalated species resulted from insertion to reactive element-halogen bond is of great interest since their reliability to Grignard reagents, one of the most powerful tools in the arsenal of synthetic chemistry.1 Here we present the study of reactivity of group 14 carbenoids (germaneand stananediyls) toward P Cl bond in iminophosphines and methylenephosphines. Treatment of Mes*N PCl with M(NR2)2 gives just common substitution products2 of the type Mes*N P-NR2. But when (Me3Si)2C PCl is used, either substitution proceeds or metal insertion products are isolated in high yields depending on nucleophilic properties of amide substituent:

Molecular structure of P-(2,4,6-tri-tert-buthylphenyl)-phenylmethylene(phenylsulfonylimino)-σ3λ5-phosphorane

AbstractThe crystal and molecular structure of P-(2,4,6-tri-tert-buthylphenyl)-phenylmethylene (phenylsulfonylimino)-σ3λ5-phosphorane, 2,4,6-But3-C6H2-P(=CHPh)(=N--SO2Ph), has been determined. Crystal data: triclinic,

Synthesis and structure of complexes of phosphorus pentachloride with 4-dimethylaminopyridine and n-methylimidazole

P\bar 1