Influence of composition on the thermal behaviour of chemically deposited nickel-phosphorus alloys

The thermal behaviour of a series of Ni-P alloys obtained by electroless plating from chloride-glycollate solutions at different pH values was studied by means of DSC analysis and X-ray diffraction.Alloys of composition up to Ni₇₈P₂₂ are microcrystalline or partially amorphous, depending on the P content; on heating up to 773 K, the amorphous phase is transformed into an equilibrium mixture of Ni and Ni₃P crystals.Most of the alloys crystallize in two exothermic stages, these occurring ever closer to each other as the P concentration approaches the eutectic value; the alloys with near-eutectic compositions are the only ones crystallizing in one stage.The first thermal effect in hypo-eutectic alloys is due to the separation of Ni crystallites from the primary amorphous phase and/or to the growth of pre-existing solid-solution crystals; the second one is due to the crystallization of intermediate amorphous phase into Ni₃P plus Ni. The first stage of crystallization in hyper-eutectic alloys corresponds to the formation of randomly-oriented Ni₃P crystals, while in the second one the residual amorphous phase yields the eutectic mixture.

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Zusammenfassung Das thermische Verhalten einer Reihe von durch stromlose Platierung mit Chlorid-Clykollat-Lösungen bei verschiedenen pH-Werten erhaltenen Ni-P-Legierungen wurde mittels DSC und Röntgendiffraktion untersucht. Legierungen mit einer Zusammensetzung bis Ni₇₈P₂₂ sind abhängig vom P-Gehalt, kristallin oder teilweise amorph. Beim Erhitzen auf 773 K wird die amorphe Phase in ein Gleichgewichtsgemisch von Ni- und Ni₃P-Kristallen überführt. Die meisten Legierungen kristallisieren in zwei exothermen Schritten, die sich einander umso mehr nähern, je mehr sich die P-Konzentration dem eutektischen Wert nähert. Als einzige kristallisieren die in der Zusammensetzung dem Eutektikum nahekommenden Legierungen in einem Schritt. Bei hypoeutektischen Legierungen ist der erste thermische Effekt der Ausscheidung von Ni-Kristallen aus der primären amorphen Phase und/oder dem Wachstum von bereits in der festen Lösung vorliegenden Kristallen, der zweite der Kristallization von Ni₃P und Ni aus der intermediären amorphen Phase zuzuschreiben. Bei hypereutektischen Legierungen entspricht der erste Schritt der Kristallisation der Bildung von random-orientierten Ni₃P-Kristallen, während des zweiten wird dagegen die verbleibende amorphe Phase in das eutektische Gemisch überführt.

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Ni-P , - pH. Ni₇₈P₂₂ , , . 773 Ni Ni₃P . , . . - . Ni₃P . - Ni₃P, .

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The authors wish to thank Professor P. Lanza and Mr. A. Garulli for their valuable assistance in the analytical studies.     

Development of a simplified method for the simultaneous determination of retinol, α-tocopherol,and β-carotene in serum by liquid chromatography–tandem mass spectrometry with atmospheric pressure chemical ionization

A new and simple method for the determination of fat-soluble vitamins (retinol, alpha-tocopherol, and beta-carotene) in human serum was developed and validated by using liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization (LC-APCI-MS-MS). Different solvent mixtures were tested to obtain deproteinization and extraction of the analytes from the matrix. As a result, a volume of 240 microL of a 1:1 (v/v) ethanol/ethyl acetate mixture added to 60 microL of serum was found to be suitable for both protein precipitation and antioxidants solubilization, giving the best recovery for all three analytes. Deproteinized samples (20 microL) were injected after dilution, without the need for concentration or evaporation to dryness and reconstruction of the sample. Vitamins were separated on a C-8 column using a 95:5 (v/v) methanol/dichloromethane mixture and ionized in the positive-ion mode; detection was performed in the selected-reaction monitoring mode. Linearity of the LC-APCI-MS-MS method was established over 5 orders of magnitude for retinol and alpha-tocopherol, whereas in the case of beta-carotene it was limited to 4 orders. Lower limits of quantitation were 1.7, 2.3, and 4.1 nM for retinol, alpha-tocopherol, and beta-carotene, respectively. Serum concentrations of retinol, alpha-tocopherol, and alpha+beta-carotene determined in a group of healthy volunteers were 2.48, 38.07, and 0.50 microM, respectively, in samples collected in winter ( n=122) and 2.69, 45.88, and 0.90 microM during summer ( n=66).     

The osmylation of flexible 3-substituted cyclopentenes

The osmylation of several 3-substituted cyclopentenes has been studied. A preference for OsO₄ addition syn to an allylic CHR₂ substituent is observed. By contrast, bulkier substituents of type CMeR₂ give rise to a striking reversal of selectivity. These results are interpreted in terms of the stereodivergent nature of the two differently reactive envelope conformations.     

Anionic Halomolybdate(III) Chemistry. Tetrahydrofuran Loss from [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I), Preparation and Properties of [Mo(3)X(12)](3)(-) (X = Br, I), and Crystal Structure of the Edge-Sharing Trioctahedral [PPh(4)](3)[Mo(3)I(12)

By interaction of MoX(3)(THF)(3) with [Cat]X in THF, the salts [Cat][MoX(4)(THF)(2)] have been synthesized [X = I, Cat = PPh(4), NBu(4), NPr(4), (Ph(3)P)(2)N; X = Br, Cat = NBu(4), PPh(4) (Ph(3)P)(2)N]. Mixed-halide species [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I) have also been generated in solution and investigated by (1)H-NMR. When the tetraiodo, tetrabromo, and mixed bromoiodo salts are dissolved in CH(2)Cl(2), clean loss of all coordinated THF is observed by (1)H-NMR. On the other hand, [MoCl(4)(THF)(2)](-) loses only 1.5 THF/Mo. The salts [Cat](3)[Mo(3)X(12)] (X = Br, I) have been isolated from [Cat][MoX(4)(THF)(2)] or by running the reaction between MoX(3)(THF)(3) and [Cat]X directly in CH(2)Cl(2). The crystal structure of [PPh(4)](3)[Mo(3)I(12)] exhibits a linear face-sharing trioctahedron for the trianion: triclinic, space group P&onemacr;; a = 11.385(2), b = 12.697(3), c = 16.849(2) ?; alpha = 76.65(2), beta = 71.967(12), gamma = 84.56(2) degrees; Z = 1; 431 parameters and 3957 data with I > 2sigma(I). The metal-metal distance is 3.258(2) ?. Structural and magnetic data are consistent with the presence of a metal-metal sigma bond order of (1)/(2) and with the remaining 7 electrons being located in 7 substantially nonbonding orbitals. The ground state of the molecule is predicted to be subject to a Jahn-Teller distortion, which is experimentally apparent from the nature of the thermal ellipsoid of the central Mo atom. The [Mo(3)X(12)](3)(-) ions reacts with phosphines (PMe(3), dppe) to form products of lower nuclearity by rupture of the bridging Mo-X bonds.     

Asymmetric Induction at C(β) and C(α) of N-Enoylsultams by Organomagnesium 1,4-Addition/Enolate Trapping

The 1,4-addition of alkylmagnesium chlorides to conjugated N-enoylsultams and subsequent ‘enolate trapping’ with aq. NH₄Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π-face defferentiation as demonstrated by the conversions 1 → 2 , 1 → 4 , and 8 → 9 . This holds also for the regioselective 1,4-addition of EtMgC1 to a dienoylsultam ( 15 → 16 ). Reactive conformations 1 ^≠, 8 ^≠, 13 , and 14 are postulated in agreement with X-ray evidence which also served for the structure determination of the product 9j .     

Asymetric dihydroxylations via chiral oxazolidines

The title compounds, new chirally masked α,β unsaturated aldehydes, undergo diastereoselective dihydroxylation reactions with 45–60% diastereisomeric excesses; chromatographic purification of the major diols, di-O-protection and auxiliary removal afford optically pure α,β dialkoxy aldehydes.     

Rh(I) coordination chemistry of chiral alpha-aminophosphine(eta6-arene)chromium tricarbonyl ligands

The diastereoselective addition of Ph(2)PH to the chiral ortho-substituted eta(6)-benzaldimine complexes (eta(6)-o-X-C(6)H(4)CH=NAr)Cr(CO)(3) (1, X = MeO, Ar = p-C(6)H(4)OMe; 2, X = Cl, Ar = Ph) leads to the formation of the corresponding chiral aminophosphines (alpha-P,N) Ph(2)P-CH(Ar(1))-NHAr(2) (3, Ar(1) = o-C(6)H(4)(OCH(3))[Cr(CO)(3)], Ar(2) = p-C(6)H(4)OCH(3); 4, Ar(1) = o-C(6)H(4)Cl[Cr(CO)(3)], Ar(2) = Ph) in equilibrium with the starting materials. The uncomplexed benzaldimine (o-ClC(6)H(4)CH=NPh), 2', analogously produces an equilibrium amount of the corresponding aminophosphine Ph(2)P-CH(Ar(1))-NHAr(2) (4', Ar(1) = o-C(6)H(4)Cl, Ar(2) = Ph). Depending on the equilibrium constant, the subsequent addition of (1)/(2) equiv of [RhCl(COD)](2) (COD = 1,5-cyclooctadiene) leads to either Ph(2)PH oxidative addition in the case of 3 or to the corresponding [RhCl(COD)(alpha-P,N)] complexes [RhCl(COD)(Ph(2)P-CH[o-C(6)H(4)Cl[Cr(CO)(3)]]-NHPh)] (5) and [RhCl(COD)(Ph(2)P-CH(o-C(6)H(4)Cl)-NHPh)] (5') in the cases of the aminophosphines 4 and 4'. The addition of the latter ligands, as racemic mixtures, to (1)/(4) equiv of [Rh(CO)(2)Cl](2) leads to the [RhCl(CO)(alpha-P,N)(2)] complexes [RhCO(Ph(2)P-CH[o-C(6)H(4)Cl[Cr(CO)(3)]]-NHPh)(2)Cl] (7) or [RhCO(Ph(2)P-CH(o-C(6)H(4)Cl)-NHPh)(2)Cl] (7') as mixtures of (R(C),S(C))/(S(C),R(C)) and (R(C),R(C))/(S(C),S(C)) diastereomers. The rhodium complexes 5 and 7' have been fully characterized by IR and (31)P NMR spectroscopies and X-ray crystallography. These compounds exhibit intramolecular Rh-Cl.H-N interactions in the solid state and in solution. The stability of the new rhodium complexes has been studied under different CO pressures. Under 1 atm of CO, 5 is converted to an unstable complex [RhCl(CO)(2)(alpha-P,N)], 6, which undergoes ligand redistribution leading to 7 plus an unidentified complex. This reaction is inhibited under higher CO or syngas pressure, as confirmed by the observation of the same catalytic activity in hydroformylation when styrene was added to a catalytic mixture that was either freshly prepared or left standing for 20 h under high CO pressure.     

Influence of heat treatment temperature of carbon fiber felt substrate on polyaniline electrosynthesis and its properties

Journal of Solid State Electrochemistry - Polyaniline was electrosynthesized using three voltammetric cycles on carbon fiber felts annealed at 1400, 1600, 2000, and 2300 K. Felts and...     

Combining planar and central chirality in ferrocene thiophosphine-sulfoxides

Novel chiral ferrocenylthiophosphine–sulfoxide and phosphine–sulfoxide derivatives possessing planar chirality for the ferrocene moiety and central chirality at the sulfur atom have been synthesized. These ligands can be obtained as pure diastereoisomers in both racemic and enantiomerically pure forms. Complete characterization by XRD analysis has allowed the assignment of the absolute configuration in each case. Preliminary coordination studies of the phosphine–sulfoxide ligands on platinum are also reported. These show chelating complexation by the phosphorous and sulfur atoms.