Studies on phosphatidylserine by tandem quadrupole and multiple stage quadrupole ion-trap mass spectrometry with electrospray ionization: Structural characterization and the fragmentation processes

Low-energy CAD product-ion spectra of various molecular species of phosphatidylserine (PS) in the forms of [M−H]⁻ and [M−2H+Alk]⁻ in the negative-ion mode, as well as in the forms of [M+H]⁺, [M+Alk]⁺, [M−H+2Alk]⁺, and [M−2H+3Alk]⁺ (where Alk=Li, Na) in the positive-ion mode contain rich fragment ions that are applicable for structural determination. Following CAD, the [M−H]⁻ ion of PS undergoes dissociation to eliminate the serine moiety (loss of C₃H₅NO₂) to give a [M−H−87]⁻ ion, which equals to the [M−H]⁻ ion of a phoshatidic acid (PA) and give rise to a MS³-spectrum that is identical to the MS²-spectrum of PA. The major fragmentation process for the [M−2H+Alk]⁻ ion of PS arises from primary loss of 87 to give rise to a [M−2H+Alk−87]⁻ ion, followed by loss of fatty acid substituents as acids (R_xCO₂H, x=1,2) or as alkali salts (e. g., R_xCO₂Li, x=1,2). These fragmentations result in a greater abundance of [M−2H+Alk−87−R₂CO₂H]⁻ than [M−2H+Alk−87−R₁CO₂H]⁻ and a greater abundance of [M−2H+Alk−87−R₂CO₂Li]⁻ than [M−2H+Alk−87−R₁CO₂Li]⁻; while further dissociation of the [M−2H+Alk−87−R_{2(or 1)}CO₂Li]⁻ ions gives a preferential formation of the carboxylate anion at sn-1 (R₁CO₂⁻) over that at sn-2 (R₂CO₂⁻). Other major fragmentation process arises from differential loss of the fatty acid substituents as ketenes (loss of R_x′CH=CO, x=1,2). This results in a more prominent [M−2H+Alk−R₂′CH=CO]⁻ ion than [M−2H+Alk−R₁′CH=CO]⁻ ion. Ions informative for structural characterization of PS are of low abundance in the MS²-spectra of both the [M+H]⁺ and the [M+Alk]⁺ ions, but are abundant in the MS³-spectra. The MS²-spectrum of the [M+Alk]⁺ ion contains a unique ion corresponding to internal loss of a phosphate group probably via the fragmentation processes involving rearrangement steps. The [M−H+2Alk]⁺ ion of PS yields a major [M−H+2Alk−87]⁺ ion, which is equivalent to an alkali adduct ion of a monoalkali salt of PA and gives rise to a greater abundance of [M−H+2Alk−87−R₁CO₂H]⁺ than [M−H+2Alk−87−R₂CO₂H]⁺. Similarly, the [M−2H+3Alk]⁺ ion of PS also yields a prominent [M−2H+3Alk−87]⁺ ion, which undergoes consecutive dissociation processes that involve differential losses of the two fatty acyl substituents. Because all of the above tandem mass spectra contain several sets of ion pairs involving differential losses of the fatty acid substituents as ketenes or as free fatty acids, the identities of the fatty acyl substituents and their positions on the glycerol backbone can be easily assigned by the drastic differences in the abundances of the ions in each pair.     

Synthesis and structure of the platinum complexes [Bu4N]+[PtBr5(DMSO)]?, [Ph4P]+[PtBr5(DMSO)]?, and [Ph3(n-Am)P]+[PtBr5(DMSO)]?

The complexes [Bu₄N]₂⁺[PtBr₆]²⁻ (I), [Ph₄P]₂⁺[PtBr₆]²⁻ (II), and [Ph₃(n-Am)P]₂⁺ (III) are synthesized by the reactions of tetrabutylammonium bromide, tetraphenylphosphonium bromide, and triphenyl(n-amyl)-tetraphenylphosphonium bromide, respectively, with potassium hexabromoplatinate (mole ratio 2: 1). After recrystallization from dimethyl sulfoxide, complexes I, II, and III transform into [Bu₄N]⁺[PtBr₅(DMSO)]⁻ (IV), [Ph₄P]⁺[PtBr₅(DMSO)]⁻ (V), and [Ph₃(n-Am)P]⁺[PtBr₅(DMSO)]⁻ (VI). According to the X-ray diffraction data, the cations of complexes IV–VI have a slightly distorted tetrahedral structure. The N-C and P-C bond lengths are 1.492(7)–1.533(6) and 1.782(10)–1.805(10) ?, respectively. The platinum atoms in the mononuclear anions are hexacoordinated. The dimethyl sulfoxide ligands are coordinated with the Pt atom through the sulfur atom (Pt-S 2.3280(18)–2.3389(11) ?). The Pt-Br bond lengths are 2.4330(6)–2.4724(6) ?.     

Phosphonium salts [Ph3AlkP] 2+ [Hg2I6]2? and [Ph3AlkP] 2+ [Hg4I10]2?: Synthesis and structure

Mercury complexes [Ph₃AlkP]₂⁺[Hg₂I₆]²⁻ and [Ph₃AlkP]₂⁺[Hg₄I₁₀]²⁻ (R = Me, Et, Pr, iso-Pr, Bu, iso-Bu) are synthesized by the reactions of triphenylalkylphosphonium Ph₃AlkPI with mercury iodide in acetone with the mole ratio 1: 1 and 1: 2, respectively. According to X-ray diffraction data, the phosphorus atom in the cations of the [Ph₃(iso-Pr)P]₂⁺[Hg₂I₆]²⁻, [Ph₃BuP]₂⁺[Hg₂I₆]²⁻, and [Ph₃(iso-Pr)P]₂⁺[Hg₄I₁₀]²⁻ complexes has a distorted tetrahedral coordination. The CPC bond angles and P-C bond lengths vary within 107.3(4)°-112.0(4)° and 1.774(8)-1.827(7) ?. In the [Hg₂I₆]²⁻ centrosymmetric binuclear anions, the mercury atoms of tetrahedral coordination lie in two near-perpendicular Hg₂I₆planes. Hg₄I₄ eight-membered cycles of the [Hg₄I₁₀]²⁻ tetranuclear anion are joined into polymeric chains through Hg … I coordination bonds (3.334, 3.681 &OA) due to which Hg atoms have a trigonal bipyramidal coordination. Original Russian Text ? V.V. Sharutin, V.S. Senchurin, N.N. Klepikov, O.K. Sharutina, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 267–273.     

Complexes of (ω-diphenylphosphinoalkyl)diphenylphosphine sulfides with silver nitrate in pyridine

The behavior of the phosphine-phosphine sulfide complexes of silver, [Ph₂P(S)(CH₂) _n PPh₂] _m ·AgNO₃ (n=2 or 4;m=1 or 2), in pyridine was studied. Dissolution of the 1:1 complexes in pyridine leads to destruction of their dimeric structures Ag₂[Ph₂P(S)(CH₂) _n PPh₂]₂(NO₃)₂ (A) to form the complexes Agp_y ⁺−P(Ph₂)(CH₂) _n Ph₂P=S and Agp_y ⁺−S=PPh₂(CH₂) _n PPh₂. The solid complexes isolated from pyridine restore dimeric structure A. According to the data of X-ray diffraction analysis, the 1:2 complex isolated from pyridine has the structure [S=P(Ph₂)(CH₂)₂(Ph₂)P−(NO₃)Ag(Py)−P(Ph₂) (CH₂)₂(Ph₂)P=S]Py. According to the data of IR spectroscopy, dissolution of this complex in chloroform leads to the formation of the dimeric structure Ag₂Ph₂P(S)(CH₂)₂PPh₂]₄(NO₃)₂. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1751–1758, September, 1998.     

Synthesis and properties of bis(biphenyl)chromium(<Emphasis Type="SmallCaps">i</Emphasis>) 1,4-di(2-cyanoisopropyl)-1,4-dihydrofulleride and 1-(2-cyanoisopropyl)-1,2-dihydrofullerene

Radical-ion salts bis(biphenyl)chromium(i) 1,4-di(2-cyanoisopropyl)-1,4-dihydrofulleride [(Ph₂)₂Cr]^+·[1,4-(CMe₂CN)₂C₆₀]^−· and bis(biphenyl)chromium(i) 1-(2-cyanoisopropyl)-1,2-dihydrofulleride [(Ph₂)₂Cr]^+·[1,2-(CMe₂CN)(H)C₆₀]^−·, the salt bis(biphenyl)chromium(i) (2-cyanoisopropyl)fulleride [(Ph₂)₂Cr]^+·[(CMe₂CN)C₆₀]⁻, and neutral 1-(2-cyanoisopropyl)-1,2-dihydrofullerene 1,2-(CMe₂CN)(H)C₆₀ have been synthesized for the first time. The compounds [(Ph₂)₂Cr]^+·[1,4-(CMe₂CN)₂C₆₀]^−· and [(Ph₂)₂Cr]^+·[1,2-(CMe₂CN)(H)C₆₀]^−· decompose in THF to form [(Ph₂)₂Cr]^+·[(CMe₂CN)C₆₀]⁻, whose protonation affords 1,2-(CMe₂CN)(H)C₆₀. 1,4-Di(2-cyanoisopropyl)-1,4-dihydrofullerene 1,4-(CMe₂CN)₂C₆₀ and 1,2-(CMe₂CN)(H)C₆₀ are stable in vacuo up to 513 K. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1935–1939, September, 2008.     

Synthesis and Structure of Phosphorus-Containing Complexes [Ph4P]

Complexes [Ph₄P] ₂ ⁺ [Hg₄I₁₀]²⁻ (I) and [[Ph₄P] ₂ ⁺ [BiI₅(Me₂S=O)]²⁻ (II) are synthesized by the reactions of tetraphenylphosphonium Ph₄PI with mercury diiodide in acetone and with bismuth triiodide in dimethyl sulfoxide, respectively. According to X-ray diffraction analysis, structural units of these complexes are tetraphenylphosphonium cations and tetra- and mononuclear anions, respectively. The phosphorus atoms in the tetraphenylphosphonium cations have a distorted tetrahedral coordination. In the central fragment of the centrosymmetric anion [Hg₄I₁₀]²⁻, the distances between the terminal mercury atoms and iodine atoms are 3.503(2) Å. The mercury atoms in the central and terminal fragments of compound I have distorted tetrahedral and trigonal coordinations, respectively. The bismuth atom in the mononuclear octahedral anion of complex II contains a dimethyl sulfoxide molecule along with five iodine atoms in the coordination sphere. __________ Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 10, 2005, pp. 791–795. Original Russian Text Copyright ? 2005 by Sharutin, Egorova, Sharutina, Dorofeeva, Molokov, Fukin.     

Synthesis and structure of cobalt complexes [Ph3(n-Pr)P 2+ [CoI4]2? and [Ph3(n-Am)P 2+ [CoI4]2?

Complexes Ph₃(n-Pr)P₂⁺[CoI₄]²⁻ (I) and [Ph₃(n-Am)P]₂⁺ [CoI₄]²⁻ (II) were synthesized by reactions of triphenyl(alkyl)phosphonium iodide with cobalt(II) iodide in acetone. According to the X-ray diffraction data, complexes I and II consist of tetrahedral triphenyl(alkyl)phosphonium cations (for I, P-C is 1.787(4)–1.804(4) ? and CPC is 106.73(18)°–111.4(18)°; for II P-C is 1.786(6)–1.802(6) ? and CPC is 107.6(3)°–111.7(3)°) and [CoI₄]²⁻ anions (Co-I 2.5923(6)–2.6189(6) ?, ICoI 101.86(2)°–113.25(2)° for I; Co-I 2.5899(9)–2.6171(9) 107.01(3)°–110.47(3)° for II).     

Pivalates with the M<Superscript>II</Superscript><Subscript>4</Subscript>O<Subscript>4</Subscript> cubane core (M = Co,Ni): synthesis,structure, magnetic properties,and solid-state thermolysis

Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {M^II ₄(μ₃−OR)₄} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal decomposition of the known pivalate clusters [M^II ₄(μ₃−OMe)₄−(μ₂−OOCBu^t)₂(η²−OOCBu^t)₂(MeOH)₄] and the new clusters [M₄^II(μ₃)−OH₄(η¹−OOCBu^t)₃−(μ−(NH₂)₂C₆H₂Me₂)₃(η¹−(NH₂)₂C₆H₂Me₂)₃]⁺(OOCBu^t)− (M = Co or Ni) was studied by differential scanning calorimetry and thermogravimetry. The thermolysis of cubane-like CoII and NiII pivalates is a destructive process. The phase composition of the decomposition products is determined by the nature of coordinated ligands and the structural features of the metal core.     

Synthesis and complexing properties of four imidazolyl acetamido p-tert-butylcalix[4]arenes

Four imidazolyl acetamido p-tert-butylcalix[4]arenes 5–8 have been prepared by reacting the corresponding methyl esters derivatives 1–4 with histamine in 1:1 mixture of methanol:toluene. The yields ranged from 56 to 68%. 5–8 have been shown to be in cone conformation. The complexation behaviour of 5–8 towards monovalent metal picrates M⁺Pic⁻ with M⁺ = Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ and divalent metal picrates M²⁺(Pic⁻)₂ with M²⁺ = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Zn²⁺ and Co²⁺ are given. Tentative localisation of the metal cations in the receptors is given. The binding properties towards these cations have been determined along with stoichiometries of the complexes.     

Heteroorganic betaines

The [Ph₃P⁺−CMe₂−SiMe₂−SEt]Br⁻ salt was prepared by the reaction of betaine Ph₃P⁺−CMe₂SiMeR−S⁻ (1a: R=Me) with EtBr. Acetylation of betaine1a or Et₃P⁺−CHMeSiMe₂−S⁻ (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-ene-4-thione      

Electrochemical Investigations Give Some Insights into the Coordination Chemistry of New Stable Iridium(+1), Iridium(0), and Iridium(−1) Complexes

The redox chemistry of the stable tetracoordinated 16 valence electron d⁸‐[Ir^+I(tropp^Ph)₂]⁺(PF₆)^? and pentacoordinated 18 valence d⁸‐[Ir^+I(tropp^Ph)₂Cl] complexes was investigated by cyclic voltammetry (tropp^Ph=dibenzotropylidenyl phosphine). The experiments were performed using a platinum microelectrode varying scan rates (100 mV/s–10 V/s) and temperatures (? 40 to 20 °C) in tetrahydrofuran, THF, or acetonitrile, ACN, as solvents. In THF, the overall two‐electron reduction of the 16 valence electron d⁸‐[Ir^+I(tropp^Ph)₂]⁺(PF₆)^? proceeds in two well separated slow heterogeneous electron transfer steps according to: d⁸‐[Ir^+I (tropp^Ph)₂]⁺+e^?→d⁹‐[Ir⁰(tropp^Ph)₂]+e^?→d¹⁰‐[Ir^?I(tropp^Ph)₂]^?, [k^s₁=2.2×10^?3 cm/s for d⁸‐Ir^+I/d⁹‐Ir⁰ and k^s₂=2.0×10^?3 cm/s for d⁹‐Ir⁰/d¹⁰‐Ir^?I]. In ACN, the two redox waves merge into one “two‐electron” wave [k^s_1,2=7.76×10^?4 cm/s for d⁸‐Ir^+I/d⁹‐Ir⁰ and d⁹‐Ir⁰/d¹⁰‐Ir^?I] most likely because the neutral [Ir⁰(tropp^Ph)₂] complex is destabilized. At low temperatures (ca. ? 40 °C) and at high scan rates (ca. 10 V/s), the two‐electon redox process is kinetically resolved. In equilibrium with the tetracoordianted complex [Ir^+I(tropp^Ph)₂]⁺ are the pentacoordinated 18 valence [Ir^+I(tropp^Ph)₂L]⁺ complexes (L=THF, ACN, Cl^?) and their electrochemical behavior was also investigated. They are irreversibly reduced at rather high negative potentials (? 1.8 to ? 2.4 V) according to an ECE mechanism 1) [Ir^+I(tropp^Ph)₂(L)]+e^?→[Ir⁰(tropp^Ph)₂(L)]; 2) [Ir⁰(tropp^Ph)₂(L)]→[Ir(tropp^Ph)₂]+L, iii) [Ir⁰(tropp^Ph)₂]+e^?→[Ir^?I(tropp^Ph)₂]^?. Since all electroactive species were isolated and structurally characterized, our measurements allow for the first time a detailed insight into some fundamental aspects of the coordination chemistry of iridium complexes in unusually low formal oxidation states.     

Liquid Densities and Excess Molar Volumes for Binary Systems (Ionic Liquids + Methanol or Water) at 298.15, 303.15 and 313.15 K,and at Atmospheric Pressure

Binary excess molar volumes, V _m ^E, have been evaluated from density measurements, using a vibrating tube densimeter over the entire composition range for binary liquid mixtures of ionic liquids 1-ethyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-butyl-3-methyl-imidazolium diethyleneglycol monomethylethersulphate [BMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻ or 1-methyl-3-octyl-imidazolium diethyleneglycol monomethylethersulphate [MOIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+methanol and [EMIM]⁺[CH₃(OCH₂CH₂)₂OSO₃]⁻+water at 298.15, 303.15 and 313.15 K. The V _m ^E values were found to be negative for all systems studied. The V _m ^E results are explained in terms of intermolecular interactions and packing effects. The experimental data were fitted by the Redlich-Kister polynomial.     

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> by APCI-MS

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH₂Cl₂). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n−Bu)₄N⁺X⁻ (X⁻ = Cl⁻, NO₃⁻, Br⁻, I⁻). Solutions of receptors and anions in CH₂Cl₂ were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M+X]⁻, (M=1–3, X⁻=Cl⁻, NO₃⁻, Br⁻, I⁻) were observed in negative mode APCI-MS along with the deprotonated receptors [M−H]⁻. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.     

Transformations of phosphazane ligands in the coordination sphere of transition metals. Reactions of phosphinotriazene Ph<Subscript>2</Subscript>P-N(Ph)-N=NPh with Ni<Superscript>0</Superscript> and Ni<Superscript>I</Superscript> complexes

3-(Diphenylphosphino)-1,3-diphenyltriazene Ph₂P-NPh-N=NPh was synthesized. The reactions of this compound with bis(cycloocta-1,5-diene)nickel, (cod)₂Ni, and nickel(I) bis(triphenylphosphino)bis(trimethylsilyl)amide, (Ph₃P)₂Ni-N(SiMe₃)₂, afforded the anionic nickel complex [Ph₄P]⁺[Ni(PhNNNPh)₃]⁻ in 15 and 78% yields, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1585–1589, July, 2005.     

Isomeric discrimination and quantification of thyroid hormones, T3 and rT3, by the single ratio kinetic method using electrospray ionization mass spectrometry

The single ratio kinetic method is applied to the discrimination and quantification of the thyroid hormone isomers, 3,5,3′-triiodothyronine and 3,3′,5′-triiodothyronine, in the gas phase, based on the kinetics of the competitive unimolecular dissociations of singly charged transition-metal ion-bound trimeric complexes [M^II(A)(ref*)₂-H]⁺ (M^II = divalent transition-metal ion; A=T₃ or rT₃; ref* = reference ligand). The trimeric complex ions are generated using electrospray ionization mass spectrometry and the ions undergo collisional activation to realize isomeric discrimination from the branching ratio of the two fragment pathways that form the dimeric complexes [M^II(A)(ref*)-H]⁺ and [M^II(ref*)₂-H]⁺. The ratio of the individual branching ratios for the two isomers R_iso is found strongly dependent on the references and the metal ions. Various sets are tried by choosing the reference from amino acids, substituted amino acids, and dipeptides in combination with the central metal ion chosen from five transition-metal ions (Co^II, Cu^II, Mn^II, Ni^II, and Zn^II) for the complexes in this experiment. The results are compared in terms of the isomeric discrimination for the T₃/rT₃ pair. Calibration curves are constructed by relating the ratio of the branching ratios against the isomeric composition of their mixture to allow rapid quantitative isomer analysis of the sample pair. Furthermore, the instrument-dependence of this method is investigated by comparing the two sets of results, one obtained from a quadrupole ion trap mass spectrometer and the other from a quadrupole time-of-flight mass spectrometer.     

Atmospheric pressure chemical ionization and fragmentation of aminomonosaccharides in H2O and D2O

Aminomonosaccharides (glucosamine, galactosamine, and mannosamine) in H₂O and D₂O were ionized by atmospheric pressure chemical ionization (APCI) and their fragmentation patterns were investigated to identify them. All the aminomonosaccharides showed the same fragment ions but their relative ion intensities were different. Major product ions generated in H₂O were [M + H]⁺, [M + H – H₂O]⁺, and [2M + H – 3H₂O]⁺, while in D₂O were [M_D6 + D]⁺, [M_D6 + D – D₂O]⁺, and [2M_D6 + D – D₂O – 2HDO]⁺. At a high fragmentor voltage above 120 V, the relative ion intensities of the major product ions showed different trends according to the aminomonosaccharides. For the use of H₂O as solvent and eluent, the order of the ion intensity ratio of [M + H – H₂O]⁺/[2M + H – 3H₂O]⁺ was galactosamine > mannosamine > glucosamine. When using D₂O as solvent and eluent, the order of the ion intensity ratios of [M_D6 + D – D₂O]⁺/[M_D6 + D]⁺ and [2M_D6 + D – D₂O – 2HDO]⁺/[M_D6 + D]⁺ was mannosamine > galactosamine > glucosamine. It was found that glucosamine, galactosamine, and mannosamine could be distinguished by the specific trends of the major product ion ratios in H₂O and D₂O. Copyright © 2009 John Wiley & Sons, Ltd.     

Tuning the sulfur-heterometal interaction in organolead(IV) complexes of [Pt2(μ-S)2(PPh3)4]

Reactions of [Pt₂(μ-S)₂(PPh₃)₄] with Ph₃PbCl, Ph₂PbI₂, Ph₂PbBr₂ and Me₃PbOAc result in the formation of bright yellow to orange solutions containing the cations [Pt₂(μ-S)₂(PPh₃)₄PbR₃]⁺ (R₃ = Ph₃, Ph₂I, Ph₂Br, Me₃) isolated as PF₆⁻ or BPh₄⁻ salts. In the case of the Me₃Pb and Et₃Pb systems, a prolonged reaction time results in formation of the alkylated species [Pt₂(μ-S)(μ-SR)(PPh₃)₄]⁺ (R = Me, Et). X-ray structure determinations on [Pt₂(μ-S)₂(PPh₃)₄PbMe₃]PF₆ and [Pt₂(μ-S)₂(PPh₃)₄PbPh₂I]PF₆ have been carried out, revealing different coordination modes. In the Me₃Pb complex, the (four-coordinate) lead atom binds to a single sulfur atom, while in the Ph₂PbI adduct coordination of both sulfurs results in a five-coordinate lead centre. These differences are related to the electron density on the lead centre, and indicate that the interaction of the heterometal centre with the {Pt₂S₂} metalloligand core can be tuned by variation of the heteroatom substituents. The species [Pt₂(μ-S)₂(PPh₃)₄PbR₃]⁺ display differing fragmentation pathways in their ESI mass spectra, following initial loss of PPh₃ in all cases; for R = Ph, loss of PbPh₂ occurs, yielding [Pt₂(μ-S)₂(PPh₃)₃Ph]⁺, while for R = Me, reductive elimination of ethane gives [Pt₂(μ-S)₂(PPh₃)₃PbMe]⁺, which is followed by loss of CH₄.     

Cyclopropanation of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate

Reactions of 5-(allyloxymethyl)- and 5-(methallyloxymethyl)-5-ethyl-1,3-dioxanes with methyl diazoacetate catalyzed by Rh₂(OAc)₄ or Cu(OTf)₂ in the presence of [bmim]⁺Cl⁻, [bmim]⁺BF₄ ⁻, and [bmim]⁺PF₆ ⁻ proceed regioselectively at the C=C bond and lead to the formation of the corresponding cyclopropane-containing 1,3-dioxanes in yields up to 62%.     

Synthese und Eigenschaften einigerp-tolyl-phenylsubstituierter Di- und Trisilane und von 1,1,1,3,3,3-Hexaphenyltrisilan

The synthesis and properties of [Ph ₂ p-TolSi]₂, [Ph ₂ p-TolSi]₂SiPh ₂, [Ph ₃ Si]₂Si(p-Tol)₂, [Ph ₂ p-TolSi]₂Si(p-Tol)₂ and (SiPh ₃)₂SiH₂ are described. The silanes are identified using IR,Ra- and²⁹Si-NMR-spectroscopy.