Reactivity of Mo3PdS4+ 4 Cluster: Evidence for New Ligands PhP(OH)2 and Ph2P(OH) and Structural Characterization of [Mo3(Pd(PPh3))S4(H2O)5Cl4]⋅0.5CH3OH⋅3H2O

Cuboidal cluster aqua complex [Mo₃(PdCl)S₄(H₂O)₉]³⁺ in 4M HCl causes isomerization of (HO)₂P(O)(H), (HO)P(O)(H)₂, PhP(O)(OH)(H), and Ph₂P(O)(H) into hydroxo tautomers P(OH)₃, HP(OH)₂, PhP(OH)₂, and Ph₂P(OH) which are stabilized by P coordination to the Pd atom in the cluster. The reactions were followed by ³¹P NMR and UV/Vis spectroscopy. Hypophosphorous acid H₂P(O)(OH) in the presence of the cluster is rapidly oxidized into phosphorous acid; the reaction can be made catalytic. Coordination of PPh₃ also takes place, giving [Mo₃(Pd(PPh₃))S₄(H₂O)₅Cl₄]0.5CH₃OH3H₂O, whose crystal structure was determined.     

Geometries and vibrational frequencies for silanone,silanoic acid and silicic acid

The geometries of silanone, H₂SiO, silanoic acid, (HO)HSiO, and silicic acid, (HO)₂SiO, have been calculated using gradient techniques with 3-21G and DZ + P basis sets. The SiO bond length is found not to be strongly dependent on the substitution of OH for H. Vibrational frequencies have been calculated by numerical differentiation of the gradient at the 3–21G level. Good agreement with experiment is found after uniform scaling. For the three compounds considered, the frequency for the SiO stretch is found to increase as OH is substituted for H, confirming the experimental result.     

Metal complexes of a phenol-tailed porphyrin with different hydrogen bonds

Hydrogen bonds are very common and important interactions in biological systems, they are used to control the microenvironment around metal centers. It is a challenge to develop appropriate models for studying hydrogen bonds. We have synthesized two metal complexes of the phenol-tailed porphyrin, [Zn(HL)] and [Fe(HL)(C₆H₄(OH)(O))]. X-ray crystallography reveals that the porphyrin functions as a dianion HL^2? and the phenol OH is involved in hydrogen bonds in both structures. In [Zn(HL)], an intramolecular hydrogen bond is formed between the carbonyl oxygen and OH. In [Fe(HL)(C₆H₄(OH)(O))], the unligated O(5) of the ligand is involved in two hydrogen bonds, as a hydrogen bond donor and a hydrogen bond acceptor. The overall electronic effect on the ligand could be very small, with negligible impact on the structure and the spin state of iron(III). The structural differences caused by the hydrogen bonds are also discussed.     

Exploring of catalytic oxygen reduction reaction activity of lattice carbons of vanadium and niobium doped nitrogen codoped carbon nanotubes by density functional theory

The oxygen electroreduction mechanism on the V- and Nb-doped nitrogen-codoped (6,6)armchair carbon nanotube with incorporated MN₄ fragment has been studied using the ωB97XD and PBE density functional theory approaches. The metal center in MN₄ fragment and the adjacent NCCN double bond (C₂ site) of the support have been revealed as active centers. The metal active centers turned out to be irreversibly oxidized at the first step of ORR affording stable O*, 2O*, or O*HO* adsorbates depending on the applied electrode potential U, that makes them no longer active in ORR. Therefore, the C₂ site comes at the forefront in ORR catalysis. Among the metal oxidized forms M(O)N₄ , M(O)(O)N₄ , and M(O)(OH)N₄ CNT, the C₂ site of the latter turned out to be most active for 4e dissociative ORR. For both metals the last protonation/electron transfer step, HO* + H* → H₂O, is the rate-limiting step. The alternative hydrogen peroxide formation is not only thermodynamically less favorable but also kinetically slower than the 4e dissociative ORR route on the C₂ site of model M(O)(OH)N₄ CNT catalyst.     

1H‐NMR Analysis of Intra‐ and Intermolecular H‐Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides,Inositols, and Ginkgolides

The interpretation of ¹H‐NMR chemical shifts, coupling constants, and coefficients of temperature dependence (δ(OH), J(H,OH), and Δδ(OH)/ΔT values) evidences that, in (D₆)DMSO solution, the signal of an OH group involved as donor in an intramolecular H‐bond to a hydroxy or alkoxy group is shifted upfield, whereas the signal of an OH group acting as acceptor of an intramolecular H‐bond and as donor in an intermolecular H‐bond to (D₆)DMSO is shifted downfield. The relative strength of the intramolecular H‐bond depends on co‐operativity and on the acidity of OH groups. The acidity of OH groups is enhanced when they are in an antiparallel orientation to a C−O bond. A comparison of the ¹H‐NMR spectra of alcohols in CDCl₃ and (D₆)DMSO allows discrimination between weak and strong intramolecular H‐bonds. Consideration of IR spectra (CHCl₃ or CH₂Cl₂) shows that the rule according to which the downfield shift of δ(OH) for H‐bonded alcohols in CDCl₃ parallels the strength of the H‐bond is valid only for alcohols forming strong intramolecular H‐bonds. The combined analysis of J(H,OH) and δ(OH) values is illustrated by the interpretation of the spectra of the epoxyalcohols 14 and 15 (Fig. 3). H‐Bonding of hexopyranoses, hexulopyranoses, alkyl hexopyranosides, alkyl 4,6‐O‐benzylidenehexopyranosides, levoglucosans, and inositols in (D₆)DMSO was investigated. Fully solvated non‐anomeric equatorial OH groups lacking a vicinal axial OR group (R=H or alkyl, or (alkoxy)alkyl) show characteristic J(H,OH) values of 4.5 – 5.5 Hz and fully solvated non‐anomeric axial OH groups lacking an axial OR group in β‐position are characterized by J(H,OH) values of 4.2 – 4.4 Hz (Figs. 4 – 6). Non‐anomeric equatorial OH groups vicinal to an axial OR group are involved in a partial intramolecular H‐bond (J(H,OH)=5.4 – 7.4 Hz), whereas non‐anomeric equatorial OH groups vicinal to two axial OR form partial bifurcated H‐bonds (J(H,OH)=5.8 – 9.5 Hz). Non‐anomeric axial OH groups form partial intramolecular H‐bonds to a cis‐1.3‐diaxial alkoxy group (as in 29 and 41 : J(H,OH)=4.8 – 5.0 Hz). The persistence of such a H‐bond is enhanced when there is an additional H‐bond acceptor, such as the ring O‐atom ( 43 – 47 : J(H,OH)=5.6 – 7.6 Hz; 32 and 33 : 10.5 – 11.3 Hz). The (partial) intramolecular H‐bonds lead to an upfield shift (relative to the signal of a fully solvated OH in a similar surrounding) for the signal of the H‐donor. The shift may also be related to the signal of the fully solvated, equatorial HO−C(2), HO−C(3), and HO−C(4) of β‐D ‐glucopyranose ( 16 : 4.81 ppm) by using the following increments: −0.3 ppm for an axial OH group, 0.2 – 0.25 ppm for replacing a vicinal OH by an OR group, ca. 0.1 ppm for replacing another OH by an OR group, 0.2 ppm for an antiperiplanar C−O bond, −0.3 ppm if a vicinal OH group is (partially) H‐bonded to another OR group, and −0.4 to −0.6 for both OH groups of a vicinal diol moiety involved in (partial) divergent H‐bonds. Flip‐flop H‐bonds are observed between the diaxial HO−C(2) and HO−C(4) of the inositol 40 (J(H,OH)=6.4 Hz, δ(OH)=5.45 ppm) and levoglucosan ( 42 ; J(H,OH)=6.7 – 7.1 Hz, δ(OH)=4.76 – 4.83 ppm; bifurcated H‐bond); the former is completely persistent and the latter to ca. 40%. A persistent, unidirectional H‐bond C(1)−OH⋅⋅⋅O−C(10) is present in ginkgolide B and C, as evidenced by strongly different δ(OH) and Δδ(OH)/ΔT values for HO−C(1) and HO−C(10) (Fig. 9). In the absence of this H‐bond, HO−C(1) of 52 resonates 1.1 – 1.2 ppm downfield, while HO−C(10) of ginkgolide A and of 48 – 50 resonates 0.5 – 0.9 ppm upfield.     

Metal Containing New Inorganic Ring Systems Based on Siloxane and Phosphazane Frameworks

High-field ³¹P NMR spectroscopy and single crystal X-ray diffraction studies have been used to study the ring opening and nucleophilic substitution reactions of the λ³-cyclotriphosphazane [EtNPCl]₃. The synthesis of the ring opened silicophosphonate [RSi(OH){OP(O)(H)(OH)}]₂O (R = (2,6-iPr₂C₆H₃)NSiMe₃) (1) represents the first ever molecular silicophosphonate to be isolated bearing free reactive hydroxyl groups. The structure and conformation of the bulky aryloxide substituted λ³-cyclotriphosphazane derivative [EtNP(OAr)]₃ (Ar = 2,6-iPr₂C₆H₃) (2) has also been investigated. Interaction of 2 with transition metal precursor complexes leads to the isolation of phosphazane metal complexes with different mode of co-ordination of 2. Further, the reaction of Cp Ti(OAr)Cl₂ (Ar = 2,6-(CH₃)₂C₆H₃OH) with O{SiPh₂(OH)}₂ gave the eight-membered trititanosiloxane [Cp Ti(Cl) (O(SiPh₂O)₂SiPh₂O) (3). Siloxane chain expansion effects, presumed to be a consequence of ring strain, have been observed in the product. The presence of reactive Ti-Cl bond in 3 offers opportunities for its reaction chemistry to be explored.     

Stabilization of tautomeric forms P(OH)3 and HP(OH)2 and their derivatives by coordination to palladium and nickel atoms in heterometallic clusters with the Mo3MQ44+ core (M = Ni, Pd; Q = S, Se)

The cluster aqua complexes [Mo₃(MCl)Q₄(H₂O)₉]³⁺ (M = Pd or Ni) in hydrochloric acid solutions induce isomerization of the hydrophosphoryl compounds (HO)₂P(O)H, (HO)P(O)H₂, PhP(O)(OH)H, and Ph₂P(O)H into the hydroxo tautomers P(OH)₃, HP(OH)₂, PhP(OH)₂, and Ph₂P(OH), which are stabilized by coordination of the phosphorus atom to the Pd or Ni atoms. The reactions were studied by ³¹P NMR and UV-Vis spectroscopy. The kinetics of the reactions of phosphorous acid with [Mo₃(PdCl)Q₄(H₂O)₉]³⁺ was investigated by spectrophotometry. The [Mo₃(Pd(PhP(OH)₂))S₄(H₂O)₂Cl₇]³⁻ complex was isolated as a supramolecular adduct with cucurbit [8]uril, and the [Mo₃(Ni(P(OH)₃))S₄(H₂O)₈Cl]³⁺ complex was isolated as an adduct with cucurbit [6]uril. The structures of both compounds were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 606–613, March, 2005.     

Organische Phosphorverbindungen 40. Methoden zur Herstellung von Pentamethylen-1,5-bis-(dihydroxyphosphonylmethyl-phosphinsäure) [1]

Alkyl-pentamethylene-1,5-bis-(dialkyloxyphosphonylmethyl-phosphinates) (VII) are formed in high yield by heating alkyl pentamethylene-1,5-diphosphonites, (RO)₂P(CH₂)₅P(OR)₂, with alkyl chloromethylphosphonates, ClCH₂P(O)(OR)₂, at 170° for several hours until evolution of alkyl halides ceases. Hydrolysis to the corresponding acid (VIII) is effected by refluxing with conc. HCl for 40 h. The synthesis and properties of some other 1,5-diphosphorus-substituted pentanes, i.e., H₂P(CH₂)₅PH₂, Cl₂P(CH₂)₅PCl₂, (Et₂N)₂P(CH₂)₅P(NEt₂)₂, (EtO) (HO)P(CH₂)₅P(OH)(OEt), and (HO)₂P(CH₂)₅P(OH)₂, are also reported.     

Reactivity and Structure of Difluorophosphine Compounds and Their Platinum Complexes

Abstract

Various novel organodifluorophosphines involving aromatic and aliphatic substituents were prepared and used as ligands in reactions with (COD)PtCl₂ or K₂PtCl₄; complexes of the type cis-dichlorobis(organodifluorophos-phine)platinum(II) or tetrakis (organodifluorophosphine)platinum(O) were formed. The ³¹P-n.m.r. data of these compounds were correlated with Pt-P bond lengths found from X-ray diffraction studies. The hydrolysis of RPF₂ and Pt(RPF₂)₄ with water leads to the formation of RP(F)(O)(H) or [RP(F)(OH)]₂[RP((F)]₂Pt. Both products were characterized by n.m.r. spectra and by X-ray structure determinations.     

Hydrogen Bonding of Fluorinated Saccharides in Solution: F Acting as H‐Bond Acceptor in a Bifurcated H‐Bond of 4‐Fluorinated Levoglucosans

4‐Fluorinated levoglucosans were synthesised to test if OH???F H‐bonds are feasible even when the O???F distance is increased. The fluorinated 1,6‐anhydro‐β‐D ‐glucopyranoses were synthesised from 1,6 : 3,4‐dianhydro‐β‐D ‐galactopyranose ( 8 ). Treatment of 8 with KHF₂ and KF gave 43% of 4‐deoxy‐4‐fluorolevoglucosan ( 9 ), which was transformed into the 3‐O‐protected derivatives 13 by silylation and 15 by silylation, acetylation, and desilylation. 4‐Deoxy‐4‐methyllevoglucosan ( 19 ) and 4‐deoxylevoglucosan ( 21 ) were prepared as reference compounds that can only form a bivalent H‐bond from HO? C(2) to O? C(5). They were synthesised from the ⁱPr₃Si‐protected derivative of 8 . Intramolecular bifurcated H‐bonds from HO? C(2) to F? C(4) and O? C(5) of the 4‐fluorinated levoglucosans in CDCl₃ solution are evidenced by the ¹H‐NMR scalar couplings ^h1J(F,OH) and ³J(H,OH). The OH???F H‐bond over an O???F distance of ca. 3.0 Å is thus formed in apolar solvents, at least when favoured by the simultaneous formation of an OH???O H‐bond.     

Syntheses,crystal structures,and luminescent properties of two cadmium(II) complexes based on bis(imidazole) and dicarboxylate

Two complexes, [Cd(ip–OH)(H₂biim)(H₂O)][Cd(ip–OH)(H₂biim)(H₂O)₃]·8(H₂O) (1) and [Cd(Himdc)(H₂biim)] _n (2) (H₂ip–OH?=?5-hydroxylisophthalic acid, H₂biim?=?2,2’-biimidazolate, H₃imdc?=?4,5-imidazoledicarboxylic acid), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. 1 is a 3-D supramolecular network constructed by 0-D and 1-D motifs through hydrogen bonds and π?π interactions. Complex 2 is a 1-D zigzag polymeric coordination chain and the chains are connected to form a 3-D supramolecular network by hydrogen bonds. The complexes were characterized by elemental and thermogravimetric analyses. Fluorescence was also investigated.     

Three multinuclear Co(II), Zn(II) and Cd(II) complexes based on a single-armed salamo-type bisoxime: syntheses,structural characterizations and fluorescent properties

Three multinuclear complexes, [Co(L)(OAc)Co(CH₃CH₂OH)₂]·H₂O, [Zn(L)(OAc)Zn(CH₃OH)], and [{Cd(L)(OAc)Cd(CH₃OH)}₂], containing a single-armed salamo-type bisoxime H₃L have been synthesized and characterized structurally. The Co(II) complex forms a dimeric unit by intermolecular hydrogen bond interactions of neighboring dimeric molecules. The Zn(II) complex also forms a dimeric unit by intermolecular hydrogen bond interactions. Interesting features of the crystal structure include O?O short contacts. Meanwhile, self-assembling infinite 1-D, 2-D, and 3-D supramolecular structures are formed by intermolecular hydrogen bond and C–H?π interactions. The Cd(II) complex forms an infinite 2-D supramolecular structure by intermolecular hydrogen bond interactions. The photophysical properties of the Co(II), Zn(II), and Cd(II) complexes have also been discussed.     

2-Hydroxyphenylphosphinic Acid: P-Analogue of Salicylic Acid?

Abstract

Substitution of the carboxyl group -C(O)OH by -P(O)(OH)₂ and -P(O)R(OH) leads to compounds of interest to agriculture, technics and pharmacology. Under these aspects the P-analogon 1 of salicylic acid was prepared, because the monobasic -P(O)H(OH) group resembles more the carboxyl function than the dibasic moiety -P(O)(OH)₂.     

One Pot Synthesis of Bisphosphonate Esters: A Way to Synthesize Tetraphosphonate Esters

Abstract

Several methods for the preparation of symmetrical bisphosphonates of general type (RO)₂P(O)(R′OH)P(O)(OR)₂, have been developed, and investigated for their pharmacological. Pharmacological screening of these bisphosphonates have shown that these compounds have potent cardiovascular activity and are. potentialy useful in the treatment of hypertension. In this work we described of new method “one pot” for the synthesis of hydroxy bis and tetra phosphonates (I, II, III and IV).     

ORGANISCHE PHOSPHORVERBINDUNGEN 86.1 HERSTELLUNG UND EIGENSCHAFTEN VON ω-PHOSPHINYL-α-AMINOALKYL-CARBONSÄUREN

Abstract

The synthesis, chemical and spectral properties of ω-methylphosphinyl-α-aminoalkylcarbonic acids, CH₃ (HO)P(O)(CH₂)_n CH(NH₂)CO₂H, n=3, 4, 5 or 6, are described. In contrast to the corresponding phosphonic acid derivatives these compounds exhibit no anticonvulsive and NMDA-antagonistic properties.     

Syntheses,crystal structures,and magnetic properties of five new coordination compounds bearing ferrocenedicarboxylate ligands

Five new coordination compounds, {[Mn(L)(CH₃OH)₂] · CH₃OH · H₂O} _n (1), {[Cd(L)(DMF)₂(H₂O)] · H₂O} _n (2), {[Co(L)(CH₃OH)₄] · CH₃OH}₂ (3), {[Cd(L)(phen)(CH₃OH)] · CH₃OH} _n (4), and {[Mn(L)(phen)(H₂O)] · CH₃OH} _n (5) (L = 5-ferrocene-1,3-benzenedicarboxylic acid, phen = 1,10-phenanthroline) were obtained from different metal salts and L with or without 1,10-phen under mild conditions. Complex 1 is a 1-D ladder-like chain composed of 8-membered rings A and 16-membered rings B, which arrange alternately. Complex 2 is an infinite linear chain, further bridged to form a parallel double chain through different hydrogen-bond interactions. Complex 3 is a discrete dinuclear structure, while 4 is a neutral 1-D infinite zigzag coordination chain. Complex 5 is a 1-D linear chain with phen and ferrocene groups of L as pendants hanging on the different sides of the main chain. Variable temperature magnetic susceptibilities of 1 were measured and weak antiferromagnetic exchange interactions between the neighboring Mn(II) ions were found with J = ?0.95 cm^?1.     

Synthesis,spectroscopic properties,and antimicrobial activity of some new 5-phenylazo-6-aminouracil-vanadyl complexes

Six complexes, [VO(L¹-H)₂]?·?5H₂O (1), [VO(OH)(L^2,3?H)(H₂O)]?·?H₂O (2,3), [VO(OH)(L^4,5?H)(H₂O)]?·?H₂O (4,5), [VO(OH)(L⁶?H)(H₂O)]?·?H₂O (6), were prepared by reacting different derivatives of 5-phenylazo-6-aminouracil ligands with VOSO₄?·?5H₂O. The infrared and ¹H NMR spectra of the complexes have been assigned. Thermogravimetric analyses (TG, DTG) were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding divanadium pentoxide. The ligands and their vanadyl complexes were screened for antimicrobial activities by the agar-well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values for 1–4 and 6 were calculated at 30°C for 24–48?h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.     

Axial Ligand and Spin‐State Influence on the Formation and Reactivity of Hydroperoxo–Iron(III) Porphyrin Complexes

The present study focuses on the formation and reactivity of hydroperoxo–iron(III) porphyrin complexes formed in the [Fe^III(tpfpp)X]/H₂O₂/HOO^? system (TPFPP=5,10,15,20‐tetrakis(pentafluorophenyl)‐21H,23H‐porphyrin; X=Cl^? or CF₃SO₃^?) in acetonitrile under basic conditions at ?15 °C. Depending on the selected reaction conditions and the active form of the catalyst, the formation of high‐spin [Fe^III(tpfpp)(OOH)] and low‐spin [Fe^III(tpfpp)(OH)(OOH)] could be observed with the application of a low‐temperature rapid‐scan UV/Vis spectroscopic technique. Axial ligation and the spin state of the iron(III) center control the mode of O? O bond cleavage in the corresponding hydroperoxo porphyrin species. A mechanistic changeover from homo‐ to heterolytic O? O bond cleavage is observed for high‐ [Fe^III(tpfpp)(OOH)] and low‐spin [Fe^III(tpfpp)(OH)(OOH)] complexes, respectively. In contrast to other iron(III) hydroperoxo complexes with electron‐rich porphyrin ligands, electron‐deficient [Fe^III(tpfpp)(OH)(OOH)] was stable under relatively mild conditions and could therefore be investigated directly in the oxygenation reactions of selected organic substrates. The very low reactivity of [Fe^III(tpfpp)(OH)(OOH)] towards organic substrates implied that the ferric hydroperoxo intermediate must be a very sluggish oxidant compared with the iron(IV)–oxo porphyrin π‐cation radical intermediate in the catalytic oxygenation reactions of cytochrome P450.     

Organische Phosphorverbindungen XXXVI. Darstellung und Eigenschaften von Bis-(dialkoxyphosphonyl-methyl)-, Bis-(alkoxyphosphinyl-methyl)-und Bis-(oxophosphoranyl-methyl)-phosphinsäureestern sowie der entsprechenden Säuren [1]

High yields of bis-(dialkoxyphosphonyl-methyl)- phosphinic esters, (RO)₂ (O)-PCH₂P(O)OR, bis-(aloxyphosphinyl-methyl)-phosphinic esters, [R(RO)(O)PCH_2]2P(O)OR, are obtained by heating bis-chloromethyl-phosphinic esters, (CICH₂₎₂P(O)OR, with alkylphoshites, phosphonites and phosphinites, repectively, at 170 to 180°C for several hours. Hydrolysis of these esters in achieved by refluxing with conc. HCl for extended periods. Bis-(dihydroxyphosphonyl-methyl)-phosphinic acid, HO(O)P[CH₂P(O) (OH)₂]₂, obtained by hydrolysis of the all-ethyl ester, titrates in aqueous solution as a tetrabasic acid with breaks at pH = 5,2 (three equivalents) and at pH = 8,8 (one equivalent). The fifth proton can be titrated only after addition of NaCl. This acid is an excellent chelating agent for metal ions. The ¹H- and ³¹P-NMR. spectra of all the compounds prepared are discussed.     

Facile one-pot synthesis of functionalized organophosphonate esters via ketone insertion into bulky arylphosphites

The reaction of phosphorus trichloride with 2,6-diisopropyl phenol in the presence of LiCl under reflux conditions for 24 h produces a mixture of (ArO)PCl₂ and (ArO)₂PCl (Ar = 2,6-iPr₂C₆H₃). The hydrolysis of the aryloxy compounds in acetone/H₂O results in the formation of two novel phosphonate ester derivatives [(ArO)P(O)(OH)(CMe₂OH)] (1) and [(ArO)₂P(O)(CMe₂OH)] (2), respectively in a moderate yield. The title compounds have presumably formed via acetone insertion to the P-H bonds of (ArO)P(O)(H)(OH) and (ArO)₂P(O)(H), respectively, in the presence of HCl produced during the hydrolysis. Compounds 1 and 2 have been characterized by elemental analysis, and ESI-mass, Infrared and NMR spectroscopic techniques. Further, solid state structures of 1 and 2 have been established by single crystals X-ray diffraction studies.