RELATIVE CATION VERSUS ANION STABILITIES OF LOW-COORDINATED P(III)PI-BONDED PHOSPHORUS-COMPOUNDS

Schoeller W, TUBBESING U. RELATIVE CATION VERSUS ANION STABILITIES OF LOW-COORDINATED P(III)PI-BONDED PHOSPHORUS-COMPOUNDS. THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE. 1995;343:49-55.Relative cation and anion stabilities of a selected variety of low-coordinated pi-bonded phosphorus compounds are evaluated for the gas phase by means of group transfer reactions at an ab initio RHF/SCF level with inclusion of electron correlation treatment (MP4SDTQ(fc)/6-31+g(d)). The cation stabilities reveal large variations; the largest cation stabilities are possessed by the diaminophosphenium cation and the phosphanetriylammonium cation. Interestingly the diphosphinophosphenium structure is capable of strong stabilization of the corresponding cation as well as the anion. An analysis of the frontier orbitals indicates that the cationic species can be divided into classes of structures, isolobal with a carbene or a cyanide, isocyanide, rsp

The electronic structure of the tris(diaminophosphanyl)carbenium ion. A quantum chemical investigation

Schoeller W, Tubbesing U. The electronic structure of the tris(diaminophosphanyl)carbenium ion. A quantum chemical investigation. INORGANIC CHEMISTRY. 1998;37(13):3183-3185.contrast to the triaminomethyl carbenium ion which adopts a planar structure, a diaminophosphanyl substituent attached at the electron-deficient carbenium center introduces anionic character. As a consequence the tris(diaminophosphanyl)carbenium ion possesses an unusual equilibrium structure with three different PC bond lengths. The bonding situation is rationalized in the framework of contributing donor-acceptor structures to the overall bonding. A similar bonding situation is obtained for the phosphanyl substituent attached to an electron-deficient center

Interaction of donors with electron deficient low-coordinated phosphorus compounds

Schoeller W, Schneider R, Tubbesing U. Interaction of donors with electron deficient low-coordinated phosphorus compounds. PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS. 1999;146:781-784.Mono-and bis-donor-acceptor formation (donor=AH(3), Y = N, P, As, Sb, Bi and AH(2), O, S, Se, Te) is discussed on the basis of quantum chemical (ab initio) calculations for pi-bonded low-coordinated phosphorus cations, evaluating new types of bis-donor adducts

ELECTRONIC-STRUCTURE OF THE 1,3-DIPHOSPHETANE

Schoeller W, GOETTE B, TUBBESING U. ELECTRONIC-STRUCTURE OF THE 1,3-DIPHOSPHETANE. JOURNAL OF PHYSICAL ORGANIC CHEMISTRY. 1995;8(11):742-746.The equilibrium structures of cis- and trans-1,3-diphosphetane were evaluated at the RHF/6-31 g** level of optimization, with MP2 electron correlation correction. Both structures are puckered, the trans isomer being slightly lower in energy than the cis isomer. The inversion barrier in 1,3-diphosphetane is lower in energy than in phosphetane

1,2-diphosphetes with unusual structures - A quantum chemical investigation of bonding properties

Schoeller W, Tubbesing U, Rozhenko AB. 1,2-diphosphetes with unusual structures - A quantum chemical investigation of bonding properties. EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. 1998;(7):951-955.According to quantum chemical calculations at an ab initio level parent 1,2-diphosphete is slightly more stable than its corresponding 1,4-diphosphabutadiene structural isomer. The quantum chemical calculations indicate that substituents at phosphorus and to a much less extent at carbon exert strong influences on the equilibrium geometries of 1,2-diphosphete structures: pi donors at phosphorus strongly elongate the P-P bond while electronegative substituents at phosphorus increase the interflap angle of the four-membered ring systems, bringing an envelope conformation to the fore. The lengthening of the P-P bond gives rise to a Mobius-type delocalization within the ring moiety

HALOGEN SUBSTITUTION AT PHOSPHORUS IN PHOSPHAALKENES AND PHOSPHASILENES VERSUS BIS(METHYLENE)PHOSPHORANES - A QUANTUM-CHEMICAL EVALUATION OF BONDING PROPERTIES

Schoeller W, STRUTWOLF J, TUBBESING U, BEGEMANN C. HALOGEN SUBSTITUTION AT PHOSPHORUS IN PHOSPHAALKENES AND PHOSPHASILENES VERSUS BIS(METHYLENE)PHOSPHORANES - A QUANTUM-CHEMICAL EVALUATION OF BONDING PROPERTIES. JOURNAL OF PHYSICAL CHEMISTRY. 1995;99(8):2329-2334.The bonding properties of/at phosphorus-halogen substituted (F, Cl, Br, I) phosphaalkenes and -silenes were explored with ab initio calculations with effective core potential (ECP(d)) optimizing the geometries at the RHF and CISD levels. Compared with the parent compounds HP=CH2 the PC bond is slightly shrunk, indicating the formation of an ion pair X(-)PCH(2)(+). This is substantiated by an analysis of the natural atomic orbital populations. They evidence a strong shift of electron density from phosphorus toward the electronegative halogen atom in the a-space, with negligible pi-mesomeric interaction of the lone pair at the halogen with the PC sc-bond. A similar but slightly less affirmed situation results for the P-halogen substituted phosphasilenes as well as for the bis(methylene)phosphoranes. Furthermore, for the latter the halogen substitution enforces a Jahn-Teller distortion, causing symmetry reduction from C-2v to C-2 symmetry. d-orbital participation at phosphorus does not play any role in bonding

Anatrichosoma sp. in the footpads of a cat: Diagnosis and pathology of Namibian case

Anatrichosoma species are an unusual group of zoonotic trichuroid nematodes. Due to limited knowledge of their life cycle and diagnostic challenges, anatrichosomiasis has been reported only 3 times in domestic animals. A short-haired cat from central Windhoek, Namibia, presented with ulceration, swelling, and sepsis on all four paws, a severe generalized lymphadenopathy and considerable invasive eosinophilia. Histological analysis revealed epidermal hyperplasia, with severe serocellular crusting on the skin surface. One specimen revealed a series of thick-walled eggs within nematode segments with a few sections containing eggs with bioperculate appearance which is compatible with the Aphasmid group of nematodes, more specifically, the genus Anatrichosoma. Ivermectin treatment completely cleared the condition. This is the first report of Anatrichosoma sp. in the Republic of Namibia, identified from a unique location in the capital, Windhoek.Peer reviewedEntomology and Plant Patholog