Features of Phosphabutadienes Structure: Nmr Spectroscopy and X-Ray Investigation

Abstract

Conjugation effects in various phosphabutadienes are considered.     

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

Complexes of phosphorus pentachloride with 4‐dimethylaminopyridine and N‐methylimidazole were synthesized. The molecular structure of the phosphorus pentachloride complex with N‐methylimidazole was determined by single‐crystal X‐ray diffraction. In the cationic part of the complex, the phosphorus atom possesses four P Cl bonds within the range 2.109–2.148 Å and two cis‐P–N bonds (1.811 and 1.832 Å) with N‐methylimidazole and exhibits slightly distorted octahedral coordination with angles at phosphorus atom in the range 87.57°–91.50°. The relative stability of the cis and trans conformations of the complex was studied by DFT calculations. The chemical properties and reactivity of the compounds obtained are determined; their utility as condensing agents in the synthesis of amides from acids and amines was shown. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:171–177, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20392     

Laser-induced synthesis of metal–carbon materials for implementing surface-enhanced Raman scattering

Metal–carbon materials exhibiting surface-enhanced Raman scattering have been synthesized by laser irradiation of colloidal systems consisting of carbon and noble metal nanoparticles. The dependence of the Raman scattering intensity on the material composition and laser irradiation conditions has been investigated. The possibility of recording the Raman spectrum of organic dye rhodamine 6G, deposited in amount of 10^–6 M on the substrate obtained from a colloidal solution is demonstrated.     

Conjugation in Phosphabutadienes: Ab initio Investigation and NMR Spectral Manifestation: II. Magnetic Shielding in Iminophosphines and Heterobutadienes Derived from Them

The conjugation effects in iminophosphines H₃C-N = P-R (R = H, Hlg, OH, NH₂, PH₂, SiH₃, SH) and heterobutadienes H₃C-N = P-X = CY₂ (X = N, P; Y = NH₂, H) and their manifestations in NMR spectra are analyzed by RHF and MP2 calculations using the 6-31+G and 6-311+G basis sets with different numbers of polarization functions. The contribution of -mesomeric interactions to the electronic structure of these compounds is estimated from the theoretical and experimental structural parameters, calculated natural atomic charges and bond indices, surfaces of rotational coordinates of the potential energy, and energy balances of isodesmic reactions, and also from the experimental and theoretically calculated (GIAO) ¹⁵N and ³¹P NMR chemical shifts. The configuration of model heterobutadienes relative to the P = N double bond and the trans conformation of the N = P-X = C fragment, suggested by the calculation results, are consistent with the structural data for the compounds Mes*-N = P-X = C(NR₂)₂ (X = N, P; R = Alk). The character of -meso-meric interactions in the examined series of iminophosphines and butadienes derived from them is discussed. The conjugation effects influence the stability of phosphabutadienes insignificantly.     

Role of the support in the formation of the active phase of catalysts for the hydrogenation of carbon monoxide

A series of supports, i.e., substitutional solid solutions of metal oxides in an Al₂O₃ matrix, which can be used to prepare Co and Ni-containing catalysts for the hydrogenation of carbon monoxide, has been obtained. It has been shown that the activity of the catalysts correlates closely with the donor-acceptor properties of the supports and that the character of the laws discovered in largely determined by the extent of reduction of the active phase of the catalysts.A. V. Bogatskii Institute of Physical Chemistry, Ukrainian Academy of Sciences, Odessa. Translated from Teoretichekaya i Éksperimental'naya Khimiya, Vol. 27, No. 5, pp. 560–567, September–October, 1991. Original article submitted July 22, 1991.     

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

The crystal and molecular structure of P-(2,4,6-tri-tert-buthylphenyl)-phenylmethylene (phenylsulfonylimino)-³⁵-phosphorane, 2,4,6-Bu^t ₃-C₆H₂-P(=CHPh)(=N--SO₂Ph), has been determined. Crystal data: triclinic, , a = 9.472(5), b = 11.427(5), c = 13.684(5) Å, = 90.61(3), = 101.21(4), = 97.02(4)°, V = 1441.1 ų, Z = 2, D _c = 1.20 g cm^–3. The observed in 1 noticeable elongation of the P=N bond 1.563(3) Å and shortening of the P=C bond 1.617(3)Å have been discussed in terms of the electron withdrawing ability of substituents on the basis of ab initio (HF/6–31+G**) calculations of the model systems.     

Molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3λ3-phosphabutadiene-1,3

The crystal and molecular structure of 1-phenyl-1-dimethylamino-4,4-bis(trimethylsilyl)-2-aza-3³-phosphabutadiene-1,3, Me₂N(Ph)C=N—P=C(SiMe₃)₂ (1), has been determined. Crystal data: triclinic, P1¯, a = 8.975(4), b = 10.001(5), c = 12.440(6) Å, = 79.04(4), = 77.98(4), = 73.07(4)°, V = 1034.7 ų, Z = 2, and D _c = 1.08 g cm^–3. The main geometrical parameters of 1 as well as ab initio (HF/6-31+G**) calculations of the model systems show no clear evidence of high efficiency of the (C=N)— (P=C) conjugation.