Radical addition of secondary phosphine chalcogenides to allylamine: Atom-economic synthesis of aminopropylphosphine chalcogenides

Secondary phosphine sulfides and phosphine selenides react with allylamine under the conditions of radical initiation (UV or AIBN) to form the anti-Markovnikov adducts in up to 93 % yield.     

Structure and reactivity studies of the first tungsten cyanoalkylidene complex

Alkylidene complex W(CHCMe2Ph)(NAr)[OCMe(CF3)2]2 (Ar = 2, 6 diisopropylphenyl) (4) reacts with one equivalent of acrylonitrile in methylene chloride to afford the tetrameric, cyanoalkylidene complex [W(CHCN)(NAr)[OCMe(CF3)2]2]4 (5) which reacts with excess acetonitrile to give the tetrameric complex [W(N(H)C(CH3)C(CN)C(CH3)N)(NAr)[OCMe(CF3)2]2]4 (6).     

A quantum chemical study of the effect of phosphine ligand on the structure of the Mn and Fe vinylidene binuclear complex

Structures and relative energies of binuclear iron-manganese complexes with the phosphine ligand L, which exist in vinylidene Cp(CO)(L)MnFe(μ-C=CHPh)(CO)₄ (2) and benzylidene ketene η⁴-{C[Mn(CO)(L)Cp]? ?(CO)CHPh}Fe(CO)₃ (3) forms are calculated by the B3LYP density functional method. Four isomers with different positions of ligand L relative to the phenyl ring (conformers a and b) and the substituent Ph relative to the С=С bond (conformers E and Z) are considered for each form and their relative stability is determined. It is shown that all isomers of 2 have approximately the same energy (within 4 kcal/mol) whereas the energies of isomers of 3 differ within 21 kcal/mol. Isomer 3Ea in which the PPh₃ ligand contacts with the phenyl substituent of the vinylidene group is most energetically favorable. It is found that with an increase in the L ligand size in the order PH₃ < PH₂Ph < PHPh₂ < PPh₃ the Mn–P bond length increases to 2.37 Å in the most stable isomer of form 3 and to 2.43 Å in the isomers of 2 and three conformers of 3. A more substantial increase in the Mn–P bond length in complexes 2 and 3 correlates with their lower stability as compared to isomer Ea of 3, which is consistent with experimental data on the presence of only one conformer 3Ea in solution.     

Decomposition of electron-excited molecules of molybdenum and tungsten phosphine hydride and phosphine nitrogen complexes

The kinetics and mechanism of photodehydrogenation of the phosphine hydride complexes MH₄L₄ (M = Mo, W; L are phosphine ligands) and the formation of coordinatively unsaturated species M_L4 were studied by the absorbance of long-wavelength bands with λ_max at 450–460 nm appeared in the absorption spectra of the photoproducts. The rate constants of the reactions of the coordinatively unsaturated M(DPPE)₂ species (M = Mo, W; DPPE = Ph₂PCH₂CH₂PPh₂) with molecular nitrogen in benzene were determined (k _W = 200 s⁻¹, k _Mo = 8700 s⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 282–284, February, 2008.     

Michael addition of amine derivatives to conjugate phosphinyl and phosphonyl nitrosoalkenes. Preparation of alpha-amino phosphine oxide and phosphonate derivatives

The synthesis of nitrosoalkenes derived from phosphine oxides and phosphonates generated through base-mediated dehydrohalogenations of readily available alpha-halooximes is reported. These highly reactive intermediates act as Michael acceptors toward nucleophilic reagents such as ammonia, amines, and optically active amino esters, furnishing alpha-amino phosphine oxides and phosphonates in a highly regioselective fashion.     

标准加入火焰原子吸收法测定钨及钨化合物中的钾、钠

在以钨为基体的溶液中，利用柠檬酸为掩蔽剂，氯化铯为消电离剂，应用火焰原子吸收法进行钨及钨化合物中钾、钠的测定，5次测定结果的极差值在0．0002％-0．0004％之间，K、Na的加标准回收率分别为98．0％-104．0％及96．4％-102．6％。本方法已应用于钨及钨化合物中钾、钠的测定。     

Cationic gold carbonyl complex on a phosphine support

A cationic gold carbonyl complex has been synthesized and characterized using several techniques including X-ray crystallography. [(Mes(3)P)Au(CO)][SbF(6)] (Mes = 2,4,6-Me(3)C(6)H(2)) has a linear, two-coordinate gold atom. This compound displays the CO stretching frequency at 2185 cm(-1). The (13)C NMR signal of the gold-bound (13)CO appears as a doublet centered at δ 182.6 ((2)J(C,P) = 115 Hz). A computational study shows that the Au-CO bond consists of electrostatic attraction, Au ← CO donation, and significant Au → CO π-back-bonding components. Polarization of the CO bond caused by the electrostatic effect of the cationic gold center is mainly responsible for the large blue shift in the CO stretching frequency.     

The role of attractive van der Waals forces in the catalysis of Michael addition by a phenyl decorated uranyl-salophen complex

The Et(3)N-assisted addition of beta-ketoester 3 to MVK in chloroform is catalyzed with high turnover efficiency by the phenyl-substituted uranyl-salophen compound 2b but not by the parent compound 1b. A plausible mechanism is suggested, involving concomitant nucleophilic attack at the beta-carbon and hydrogen bonding between the Et(3)NH(+) countercation and the carbonyl oxygen of the s-cis conformation of the enone reactant. The role of the van der Waals interactions with the aromatic side arm of 2b as a crucial driving force for catalysis is discussed.     

Catalyst-free addition of secondary phosphine chalcogenides to pyrazolecarbaldehydes

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Synthesis and structure of a tungsten dichlorosilyl dihydride complex

The reaction of the donor-stabilized silylene complex cis-Cp¹(CO)₂(H)WSiHPh · THF (3, Cp¹ = η⁵-C₅Me₅) with LiAlH₄ followed by the protonation of the resulting Li[Cp¹(CO)₂W(H)(SiH₂Ph)] (4) with excess CF₃COOH afforded the trihydride complex Cp¹(CO)₂WH₃ (6). The structure of 6 was characterized using variable-temperature NMR studies and X-ray crystal analysis. Deprotonation of 6 with KH gave the anionic dihydride complex K[Cp¹(CO)₂WH₂] (7), which was converted into the dichlorosilyl dihydride complex Cp¹(CO)₂W(H)₂(SiHCl₂) (8) on treatment with trichlorosilane. The X-ray crystal analysis of 8 revealed that it adopts a distorted pseudo-octahedral structure with a short W–Si bond, long Si–Cl bonds, and short contacts between the hydrides and silicon atom. Along with these structural features, the conformation of the silyl ligand around the W–Si bond may suggest the presence of a double interligand hypervalent interaction between the dichlorosilyl and hydrides ligands.     

Mindo/3 study of the addition of hydrogen to vinylidene

The addition of hydrogen to vinylidene is studied using the MINDO/3 method. The results obtained are then compared with those for the addition of hydrogen to methylene applying ab initio and other semi-empirical methods. As expected, the pathways of these two reactions are qualitatively similar. The insertion is a non-least-motion process in which two phases can be easily distinguished: (i) an electrophilic step in which the empty orbital of the carbene interacts with the bonding orbital of H₂, forming a three-center bond in the process, (ii) a nucleophilic step in which the lone pair orbital of the carbene interacts with the antibonding orbital of H₂. The quantitative differences between the two reactions are also discussed.