Observation of Na(+)-bound oligomers of quercetin in the gas phase

While developing a liquid chromatography/tandem mass spectrometry method for the analysis of the flavonoid quercitin, it was observed that quercetin (3,3',4',5,7-pentahydroxyflavone) exhibited clustering in both the positive and negative ion mode. Two series of positive ion clusters were observed; the first series corresponds to singly charged [2M + Na](+) at m/z 627.2 to [13M + Na](+) at m/z 3947.5, while the second series corresponds to doubly charged [7M + 2Na](2+) at m/z 1080.4 to [25M + 2Na](2+) at m/z 3798.5. In the negative ion mode, the behavior of quercetin parallels that of apigenin (4',5,7-trihydroxyflavone) in that [M + NO(3)](-), [2M + NO(3)](-), and [3M + NO(3)](-) were observed at m/z 364.1, 666.0, and 968.9, respectively; in addition, quercitin clusters with chloride ions ([2M + Cl](-) at m/z 638.9 and [3M + Cl](-) at m/z 940. 9) were observed. The results of tandem mass spectrometric examination of several cluster ions are reported.     

New and versatile routes to zirconium imido dichloride compounds

Reactions of zirconium dialkyl- or bis(amido)-dichloride complexes "[Zr(CH2SiMe3)2Cl2(Et2O)2]" or [Zr(NMe2)2Cl2(THF)2] with primary alkyl and aryl amines are described. Reaction of "[Zr(CH2SiMe3)2Cl2(Et2O)2]" with RNH2 in THF afforded dimeric [Zr2(mu-NR)2Cl4(THF)4](R=2,6-C6H3iPr2 (1), 2,6-C6H3Me2 (2) or Ph (3)), [Zr2(mu-NR)2Cl4(THF)3](R=tBu (5), iPr (6), CH2Ph (7)), or the "ate" complex [Zr2(mu-NC6F5)2Cl6(THF)2{Li(THF)3}2](4, the LiCl coming from the in situ prepared "[Zr(CH2SiMe3)2Cl2(Et2O)2]"). With [Zr(NMe2)2Cl2(THF)2] the compounds [Zr2(mu-NR)2Cl4(L)x(L')y](R=2,6-C6H3iPr2 (8), 2,6-C6H3Me2 (9), Ph (10) or C6F5 (11); (L)x(L')y=(NHMe2)3(THF), (NHMe2)2(THF)2 or undefined), [Zr2(mu-NtBu)2Cl4(NHMe2)3] (12) and insoluble [Zr(NR)Cl2(NHMe2)]x(R=iPr (13) or CH2Ph (14)) were obtained. Attempts to form monomeric terminal imido compounds by reaction of or with an excess of pyridine led, respectively, to the corresponding dimeric adducts [Zr2(mu-2,6-C6H3Me2)2Cl4(py)4] (15) and [Zr2(mu-NtBu)2Cl4(py)3] (16). The X-ray structures of 1, 2, 4, 8, 12 and 15 have been determined.     

Synthesis and structural characterization of functionalized dimeric aluminophosphonates and a monomeric gallophosphonate anion

Reaction of t-BuP(O)(OSiMe(3))(OH) with Me(3)Al leads to the formation of [Me(2)Al(mu-O)(2)P(OSiMe(3))(t-Bu)](2) (1) whereas Me(2)AlCl reacts with Ph(2)P(O)(OH) to yield [(Cl)(Me)Al(mu-O)(2)PPh(2)](2) (2). These compounds represent the first examples of functionalized dimeric four-ring type aluminophosphonate systems. The double four-ring type gallophosphonate, namely, [t-BuPO(3)GaMe](4), reacts with n-Bu(4)NHF(2) under ambient conditions, resulting in the formation of a monomeric gallophosphonate [n-Bu(4)N][MeGa[t-BuPO(2)(OH)](3)] (3). These derivatives have been adequately characterized using various spectroscopic techniques and X-ray diffraction studies.     

Synthesis,characterization, and structure of [[PtMe(3)(9-MeA)](3)] (9-MeAH = 9-Methyladenine): a cyclic trimeric platinum(IV) complex with a nucleobase

Reaction of [[PtMe(3)I](4)] with AgOAc in acetone results in formation of trimethylplatinum(IV) acetate (1) that reacts with 9-methyladenine (9-MeAH) in ratio 1:1 with its deprotonation yielding a trimethyl(9-methyladeninato)platinum(IV) complex (2) that was obtained from acetone/diethyl ether as [[PtMe(3)(9-MeA)](3)] x Me(2)CO (2a) and from chloroform/diethyl ether as [[PtMe(3)(9-MeA)](3)] x 1.5Et(2)O x 2H(2)O (2b). Single-crystal X-ray investigations revealed that 2a and 2b in the solid state form cyclic trimeric molecules in which three PtMe(3) moieties are bridged by deprotonated 9-methyladenine ligands in mu-kappa N(1):kappa(2)N(6),N(7) coordination mode. The methyladeninato ligands include angles with the plane defined by the Pt(3) unit between 55.9(3) degrees and 66.6(3) degrees. Thus, the structures of the cyclic trimers resemble hollow truncated cones. Crystals of the acetone solvate 2a consist of stacks of unidirectional trimeric molecules; the solvate acetone molecules lie between the trimers. In the crystals of complex 2b, the trimeric molecules are arranged head-to-head, and the cavity between is filled with four water molecules. Complex 2 was also fully characterized by (1)H, (13)C, and (195)Pt NMR spectroscopies. The existence of the cyclic trimeric structure of complex 2 in acetone solution was confirmed by ESI mass spectrometry exhibiting the protonated trimeric complex [[tMe(3)(9-MeA)]3)H](+) [2 + H](+) (m/z 1165) as base peak. CID experiments of that parent ion showed as main fragmentation processes loss of two methyl ligands (probably as ethane) and cleavage of a methyladenine ligand.     

Gold-thallium supramolecular arrays with 4,4'-bipyridine. Solvent induction of luminescent networks

The reaction of [AuTl(C(6)Cl(5))(2)](n) with bipy at different molar ratios, solvents or crystallisation conditions affords a series of two- and three-dimensional luminescent complexes, [AuTl(C(6)Cl(5))(2)(bipy)(0.5)](n), [AuTl(C(6)Cl(5))(2)(bipy)](n), [[Tl(bipy)][Tl(bipy)(0.5)(THF)][Au(C(6)Cl(5))(2)](2)](n), [[Tl(bipy)][Tl(bipy)(0.5)(THF)][Au(C(6)Cl(5))(2)](2)xTHF](n) and [[AuTl(C(6)Cl(5))(2)(bipy)]x0.5toluene](n)(bipy = 4,4'-bipyridine; THF = tetrahydrofuran) all of them containing polymeric chains formed via unsupported Au...Tl interactions and bridging bipyridine ligands.     

Methyltriskaidecazirconates, molecular forms of zirconia

Repeated methanolysis of [Zr(3)O](OPr(n)(10) followed by extraction and crystallization from toluene yields material that is X-ray crystallographically indistinguishable from the compound previously formulated as [Zr(13)O(8)](OMe)(36). Elemental analysis and (1)H solution NMR spectroscopy strongly suggest that this material is a mixture of methyltriskaidecazirconates (MTZ) [Zr(13)O(8)](OMe)(x)(OH)(36)(-)(x), x(av) approximately 20, that readily cocrystallize from hydrocarbon solution. These species have the metal-oxygen framework structure reported for [Zr(13)O(8)](OMe)(36), where the 13 zirconium and 32 bridging oxygen atoms comprise a fragment of the fluorite structure adopted by ZrO(2) at elevated temperatures. Ethanolysis of [Zr(3)O](OPr(n)(10) yields its ethyl analogue, [Zr(3)O](OEt)(10). Both trizirconates display temperature-dependent (1)H solution NMR spectra that are interpreted mechanistically in terms of rearrangement mechanisms involving trigonal twists at the octahedral zirconium centers.     

Electrospray ionisation mass spectral studies on hydrolysed products of sulfur mustards

Off-site detection of the hydrolysed products of sulfur mustards in aqueous samples is an important task in the verification of Chemical Weapons Convention (CWC)-related chemicals. The hydrolysed products of sulfur mustards are studied under positive and negative electrospray ionisation (ESI) conditions using an additive with a view to detecting them at trace levels. In the presence of cations (Li(+), Na(+), K(+) and NH(4) (+)), the positive ion ESI mass spectra of all the compounds include the corresponding cationised species; however, only the [M+NH(4)](+) ions form [M+H](+) ions upon decomposition. The tandem mass (MS/MS) spectra of [M+H](+) ions from all the hydrolysed products of the sulfur mustard homologues were distinct and allowed these compounds to be characterised unambiguously. Similarly, the negative ion ESI mass spectra of all the compounds show prominent adducts with added anions (F(-), Cl(-), Br(-), and I(-)), but the [M-H](-) ion can only be generated by decomposition of an [M+F](-) ion. The MS/MS spectra of the [M-H](-) ions from all the compounds result in a common product ion at m/z 77. A precursor ion scan of m/z 77 is shown to be useful in the rapid screening of these compounds in aqueous samples at trace levels, even in the presence of complex masking agents, without the use of time-consuming sample preparation and chromatography steps. An MS/MS method developed to measure the detection limits of the hydrolysed products of sulfur mustards found these to be in the range of 10-500 ppb.     

Dicationic ion-pairing of phosphoric acid diesters post-liquid chromatography and subsequent determination by electrospray positive ionization-tandem mass spectrometry

Several organophosphate triesters are widely used as flame retardants and can be metabolized to dibutyl (DBP), diphenyl (DPhP), di(2-ethylhexyl) (DEHP) and di(1,3-dichloro-2-propyl) (or bis(1,3-dichloro-2-propyl); DDCPP) phosphoric acid, respectively. A highly sensitive liquid chromatography-electrospray ionization(+)-triple quadrupole mass spectrometry (LC-ESI(+)-QQQ-MS/MS) based analysis method was presently developed. In this method the target compounds were separated with a C(18)-based reversed phase LC column, and decamethonium hydroxide (dicatonic reagent) was introduced post-LC to form ion-pairs, which were subsequently detected by ESI(+). For the phosphate acid diester ion-pairs, the mass spectra showed the most abundant ion to be [(CH(3))(2)N(CH(2))(10)N(CH(3))(3)](+), with lesser abundances of [[M-H](-)[(CH(3))(3)N(CH(2))(9)CH(2)](2+)](+) and [CH(2)CH(CH(2))(8)N(CH(3))(3)](+). For DDCPP, the fragment ions of [[Cl](-)[(CH(3))(3)N(CH(2))(10)N(CH(3))(3)](2+)](+) and [[Cl](-)[(CH(3))(3)N(CH(2))(9)CH(2)](2+)](+) could also be observed. The limits of quantitation (LOQs) by LC-ESI(+)-MS/MS (based on multiple reaction monitoring) were 0.14, 0.03, 0.14 and 0.02 ng/mL for DPhP, DBP, DDCPP and DEHP, respectively. The response was highly linearly correlated (r>0.995) with concentration over the range of the LOD to 1000 ng/mL. The matrix effect on ESI+ was negligible for the samples in experiment of in vitro metabolism using rat liver microsomes.     

Electrospray and chemical ionization mass spectrometry of di-n-butyl sulfate. Unimolecular chemistry of its protonated form and quantification method by liquid chromatography/electrospray ionization tandem mass spectrometry

Di-n-butyl sulfate (DNBS) has been studied by electrospray (ESI) and chemical (CI) ionization mass spectrometry. The use of methanol as solvent in electrospray ionization allows observation of relatively abundant [DNBS + CH(3)OH + H](+) ions (m/z 243) which upon collision dissociate to [DNBS + H](+) ions (m/z 211). In both ESI and CI experiments, it is found that [DNBS + H](+) ions lead to m/z 113 daughter ions. The composition of this m/z 113 fragment ion and its mechanism of formation have been established by high resolution measurements and CID-MIKE experiments. An 'internal substitution' reaction involving an ion-neutral intermediate is proposed to explain the formation of a [C(8)H(17)](+) ion (m/z 113) by loss of a H(2)SO(4) molecule. Finally, a LC/ESI-MS/MS quantification method is proposed in which a detection limit of di-n-butyl sulfate in the ppm range is obtained. It is suggested that the quantification method might be extended to higher dialkyl sulfates. Copyright 2000 John Wiley & Sons, Ltd.     

Reactivity of aqua coordinated monoporphyrinate lanthanide complexes: synthetic, structural and photoluminescent studies of lanthanide porphyrinate dimers

Dimerization of monoporphyrinate lanthanide complexes [Yb(Por)(H(2)O)(3)]Cl, (Por = TTP(2-), TMPP(2-) and TPP(2-)) in the presence of sterically hindered tripodal ligand, zinc Schiff-base, dilute HCl, K(2)CO(3) solution, 4,4'-bipyridine (bipy), and basic 8-hydroxyquinaldine (HQ) solution was observed in CH(2)Cl(2) at room temperature. Six neutral dimeric lanthanide porphyrinate complexes, [Yb(TTP)(mu-OH)](2)(mu-THF) (1), [Yb(TMPP)(mu-OH)(H(2)O)](2) (2), [Yb(TPP)(mu-OH)(mu-H(2)O)](2) (4), [Yb(TMPP)(mu-Cl)(H(2)O)](2) (5), [Yb(TMPP)(mu-OH)](2)(THF) (6) and [Yb(TPP)](2)(mu-OH)(mu-Q) (7), were obtained. X-Ray diffraction studies showed that for the dimers, the two lanthanide ions were bridged by OH(-), Cl(-) or H(2)O. Photoluminescent studies showed that the porphyrinate dianion acted as an antenna, transferred its absorbed visible energy to the lanthanide ion and enabled the latter emitting in the near-infrared (NIR) region. In general, the NIR emission is more intense for the dimers than for the monomers, and the NIR emission intensity decreases as the number of O-H oscillators present in the molecule increases.     

Protonation reactions of dinuclear pyrazolato iridium(I) complexes

The complex [[Ir(mu-Pz)(CNBu(t))(2)](2)] (1) undergoes double protonation reactions with HCl and with HO(2)CCF(3) to give the neutral dihydride complexes [[Ir(mu-Pz)(H)(X)(CNBu(t))(2)](2)] (X = Cl, eta(1)-O(2)CCF(3)), in which the hydride ligands were located trans to the X groups and in the boat of the complexes, both in the solid state and in solution. The complex [[Ir(mu-Pz)(H)(Cl)(CNBu(t))(2)](2)] evolves in solution to the cationic complex [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl(3) under exposure to the direct sunlight to give the complex [[Ir(mu-Pz)(Cl)(CNBu(t))(2)](2)(mu-Cl)]OTf. Protonation of both metal centers in [[Ir(mu-Pz)(CO)(2)](2)] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)(2)] is isolated. The related complex [[Ir(mu-Pz)(CO)(P[OPh](3))](2)] reacts with HCl and with HO(2)CCF(3) to give the neutral Ir(III)/Ir(III) complexes [[Ir(mu-Pz)(H)(X)(CO)(P[OPh](3))](2)], respectively. Both reactions were found to take place stepwise, allowing the isolation of the intermediate monohydrides. They are of different natures, i.e., the metal-metal-bonded Ir(II)/Ir(II) compound [(P[OPh](3))(CO)(Cl)Ir(mu-Pz)(2)Ir(H)(CO)(P[OPh](3))] and the mixed-valence Ir(I)/Ir(III) complex [(P[OPh](3))(CO)Ir(mu-Pz)(2)Ir(H)(eta(1)-O(2)CCF(3))(CO)(P[OPh](3))].     

Time-resolved electron spin resonance of gallium and germanium porphyrins in the excited triplet state

Gallium and germanium porphyrin complexes in the lowest excited triplet (T1) state have been studied by time-resolved electron spin resonance (TRESR). It is found that for Ge(TPP)(OH)2 (TPP = dianion of tetraphenylporphyrin) intersystem crossing (ISC) from the lowest excited singlet (S1) state to the T1x and T1y sublevels is faster than that to the T1z sublevel (T1x, T1y, and T1z are sublevels of the T1 state), while the ISC of ZnTPP and Ga(TPP)(OH) is selective to the T1z sublevel. This is interpreted by a weak interaction between the dpi orbital of germanium and LUMO (eg) of the porphyrin ligand, resulting in small spin-orbit coupling (SOC). The interpretation is supported by molecular orbital calculations. The ISC of Ge(OEP)(OH)2 (OEP = dianion of octaethylporphyrin) and Ge(Pc)(OH)2 (Pc = dianion of tetra-tert-butylphthalocyanine) is found to be selective to the T1z sublevel in contrast to Ge(TPP)(OH)2. This dependence on the porphyrin ligand is reasonably explained by a difference between the 3(a(1u)eg) (the OEP and Pc complexes) and 3(a(2u)eg) (the TPP complex) configurations. This is the first observation of a difference in selective ISC between the 3(a(1u)eg) and 3(a(2u)eg) configurations. The TRESR spectrum of Ge(TPP)Br2 is different from those of Ge(TPP)Cl2 and Ge(TPP)(OH)2, and is interpreted by SOC between the T1 and T2 states. From ESR parameters the square of the coefficient of the eg orbital on bromine is evaluated as 0.018 in the T1 state.     

Molecular nitrides containing group 4 and 5 metals: single and double azatitanocubanes

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.     

Structure and magnetism of heptanuclear complexes formed on encapsulation of hexacyanoferrate(II) with the Mn(II) and Ni(II) complexes of 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane

The reaction of [Mn(dmptacn)OH(2)](2+) and [Ni(dmptacn)OH(2)](2+) (dmptacn = 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane) with each cyano ligand on ferricyanide results in the assembly of heteropolynuclear cations around the cyanometalate core and reduction of Fe(III) to Fe(II). In [[Mn(dmptacn)CN](6)Fe][ClO(4)](8) x 5H(2)O (1) and [[Ni(dmptacn)CN](6)Fe][ClO(4)](8) x 7H(2)O (2), ferrocyanide is encapsulated by either six Mn(II) or Ni(II) dmptacn moieties. These same products are obtained when ferrocyanide salts are used in the synthesis instead of ferricyanide. A binuclear complex, [[Mn(dmptacn)](2)CN][ClO(4)](3) (3), has also been formed from KCN and [Mn(dmptacn)OH(2)](2+). For both Mn(II) and Ni(II), the use of the pentadentate dmptacn ligand facilitates the formation of discrete cations in preference to networks or polymeric structures. 1 crystallizes in the trigonal space group R3 macro (No. 148) with a = 30.073(3) A, c = 13.303(4) A, and Z = 3 and is composed of heptanuclear [[Mn(dmptacn)CN](6)Fe](8+) cations whose charge is balanced by perchlorate counteranions. Weak H-bonding interactions between neighboring heptanuclear cations and some perchlorate counterions generate an infinite 1D chain of alternating [[Mn(dmptacn)CN](6)Fe](8+) and ClO(4)(-) ions running along the c-axis. Complex 3 crystallizes in the orthorhombic space group Pbcn (No. 60) with a = 16.225(3) A, b = 16.320(2) A, c = 18.052(3) A, and Z = 8 and is composed of binuclear [[Mn(dmptacn)](2)CN](3+) cations in which the cyano-bridged Mn(II) centers are in a distorted trigonal prismatic geometry. Variable temperature magnetic susceptibility measurements have revealed the presence of a weak ferromagnetic interaction between the paramagnetic Mn(II) centers in 1, mediated either by the -NC-Fe-CN- bridging units or by Mn-NH...ClO(4-)...NH-Mn intercluster pathways.     

Synthesis and characterisation of cyanodithioimidocarbonate [C2N2S2]2- complexes

[PPh4]2[M(C2N2S2)2](M = Pt, Pd) and [Pt(C2N2S2)(PR3)2](PR3= PMe2Ph, PPh3) and [Pt(C2N2S2)(PP)](PP = dppe, dppm, dppf) were all obtained by the reaction of the appropriate metal halide containing complex with potassium cyanodithioimidocarbonate. The dimeric cyanodithioimidocarbonate complexes [[Pt(C2N2S2)(PR3)]2](PR3 = PMe2Ph), [M[(C2N2S2)(eta5-C5Me5)]2](M = Rh, Ir)and [[Ru(C2N2S2)(eta6-p-MeC6H4iPr)]2] have been synthesised from the appropriate transition metal dimer starting material. The cyanodithioimidocarbonate ligand is S,S and bidentate in the monomeric complexes with the terminal CN group being approximately coplanar with the CS2 group and trigonal at nitrogen thus reducing the planar symmetry of the ligand. In the dimeric compound one of the sulfur atoms bridges two metal atoms with the core exhibiting a cubane-like geometry.     

Mono- and dinuclear ruthenium carbonyl complexes with redox-active dioxolene ligands: electrochemical and spectroscopic studies and the properties of the mixed-valence complexes

The mononuclear complex [Ru(PPh(3))(2)(CO)(2)(L(1))] (1; H(2)L(1) = 7,8-dihydroxy-6-methoxycoumarin) and the dinuclear complexes [[Ru(PPh(3))(2)(CO)(2)](2)(L(2))][PF(6)] [[2][PF(6)]; H(3)L(2) = 9-phenyl-2,3,7-trihydroxy-6-fluorone] and [[Ru(PBu(3))(2)(CO)(2)](2)(L(3))] (3; H(4)L(3) = 1,2,3,5,6,7-hexahydroxyanthracene-9,10-dione) have been prepared; all complexes contain one or two trans,cis-[Ru(PR(3))(2)(CO)(2)] units, each connected to a chelating dioxolene-type ligand. In all cases the dioxolene ligands exhibit reversible redox activity, and accordingly the complexes were studied by electrochemistry and UV/vis/NIR, IR, and EPR spectroscopy in their accessible oxidation states. Oxidation of 1 to [1](+) generates a ligand-centered semiquinone radical with some metal character as shown by the IR and EPR spectra. Dinuclear complexes [2](+) and 3 show two reversible ligand-centered couples (one associated with each dioxolene terminus) which are separated by 690 and 440 mV, respectively. This indicates that the mixed-valence species [2](2+) has greater degree of electronic delocalization between the ligand termini than does [3](+), an observation which was supported by IR, EPR, and UV/vis/NIR spectroelectrochemistry. Both [2](2+) and [3](+) have a solution EPR spectrum consistent with full delocalization of the unpaired electron between the ligand termini on the EPR time scale (a quintet arising from equal coupling to all four (31)P nuclei); [3](+) is localized on the faster IR time scale (four CO vibrations rather than two, indicative of inequivalent [Ru(CO)(2)] units) whereas [2](2+) is fully delocalized (two CO vibrations). UV/vis/NIR spectroelectrochemistry revealed the presence of a narrow, low-energy (2695 nm) transition for [3](+) associated with the catecholate --> semiquinone intervalence transition. The narrowness and solvent-independence of this transition (characteristic of class III mixed-valence character) coupled with evidence for inequivalent [Ru(CO)(2)] termini in the mixed-valence state (characteristic of class II character) place this complex at the class II-III borderline, in contrast to [2](2+) which is clearly class III.     

Mass spectral studies of meso-dialkyl, alkyl aryl and cycloalkyl calix(4)pyrroles under positive and negative ion electrospray ionization conditions

A series of meso-dialkyl, alkyl aryl and cycloalkyl calix(4)pyrroles (1-15) are studied under positive and negative ion electrospray ionization (ESI) conditions. The positive ion spectra show abundant [M + H](+) and [M + Na](+) ions and the negative ion spectra show the [M + Cl](-) (the Cl(-) ions from the solvent) and [M - H](-) ions. The collision induced dissociation (CID) spectra of [M + H](+), [M + Na](+), [M + Cl](-) and [M - H](-) ions are studied to understand their dissociation pathway and compared to that reported for M(+) under electron ionization (EI) conditions. The beta-cleavage process that was diagnostic to M(+) is absent in all the CID spectra of the ions studied under ESI. Dissociation of all the studied ions resulted in the fragment ions formed by sequential elimination of pyrrole (A) and/or dialkyl/alkyl aryl/cycloalkyl (B) groups involving hydrogen migration to pyrrole ring at each cleavage of A--B bond, which clearly reveals the arrangement of A and B groups in the calix(4)pyrroles. The source of hydrogen that migrates to pyrrole ring during A--B bond cleavage is investigated by the experiments on deuterated compounds and [M + D](+) ions; and confirmed that the hydrogen attached to pyrrole nitrogen, hydrogen on alpha-carbon of alkyl group and the H(+)/Na(+) ion that added during ESI process to generate [M + H](+)/[M + Na](+) ions involve in the migration. The yields of [M + Na](+) ions are found to be different for the isomeric meso-cycloalkyl compounds (cycloheptyl, and 2-, 3- and 4-methyl cyclohexyl) and for normal and N-confused calix(4)pyrroles. The isomeric methyl and 3-hydroxy/4-hydroxy phenyl calix(4)pyrroles show specific fragmentation pattern during the dissociation of their [M - H](-) ions.     

Generation of cationic [Zr-[tert-butyl enolate]] reactive species: methyl abstraction versus hydride abstraction

Treatment of the neutral methyl-Zr-enolate [Cp(2)Zr(Me)[O(tBuO)C=CMe(2)]] (1) with one equivalent of B(C(6)F(5))(3) or [HNMe(2)Ph][B(C(6)F(5))(4)] as a methyl abstractor in THF at 0 degrees C leads to the selective formation of the free ion pair complex [Cp(2)Zr(THF)[O(tBuO)C=CMe(2)]](+) [anion](-) (2) (anion=MeB(C(6)F(5))(3) (-), B(C(6)F(5))(4) (-)), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20 degrees C in THF with release of one equivalent of isobutene to form the cationic Zr-carboxylate species [Cp(2)Zr(THF)(O(2)CiPr)](+) (3), through a proposed intramolecular proton transfer process from the tert-butoxy group to the enolate. The reaction of 1 with one equivalent of B(C(6)F(5))(3) or [HNMe(2)Ph][B(C(6)F(5))(4)] in CH(2)Cl(2) leads to the direct, rapid formation of the dimeric micro-isobutyrato-Zr dicationic species [[Cp(2)Zr[micro-(O(2)CiPr)]](2)](2+) (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph(3)C][B(C(6)F(5))(4)] is used to generate the cationic Zr-enolate species from 1 in CD(2)Cl(2), a 15:85 mixture of dicationic complexes 4 and [[Cp(2)Zr[micro-(O(2)C-C(Me)=CH(2))]](2)](2+)[B(C(6)F(5))(4)]]2-(5-[B(C(6)F(5))(4)](2)) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph(3)C(+), as supported by the parallel production of Ph(3)CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2-5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies.     

New complexes of zirconium(IV) and hafnium(IV) with heteroscorpionate ligands and the hydrolysis of such complexes to give a zirconium cluster

A series of zirconium and hafnium heteroscorpionate complexes have been prepared by the reaction of MCl4 (M = Zr, Hf) with the compounds [[Li(bdmpza)(H2O)](4)] [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate], [[Li(bdmpzdta)(H2O)](4)] [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], and (Hbdmpze) [bdmpze = 2,2-bis(3,5-dimethylpyrazol-1-yl)ethoxide] (the latter with the prior addition of Bu(n)Li). Under the appropriate experimental conditions, mononuclear complexes, namely, [MCl3(kappa3-bdmpzx)] [x = a, M = Zr (1), Hf (2); x = dta, M = Zr (3), Hf (4); x = e, M = Zr (5), Hf (6)], and dinuclear complexes, namely, [[MCl2(mu-OH)(kappa3-bdmpzx)]2] [x = a, M = Zr (7), Hf (8); x = dta, M = Zr (9); x = e, M = Zr (10)], were isolated. A family of alkoxide-containing complexes of the general formula [ZrCl2(kappa3-bdmpzx)(OR)] [x = a, R = Me (11), Et (12), iPr (13), tBu (14); x = dta, R = Me (15), Et (16), iPr (17), tBu (18); x = e, R = Me (19), Et (20), (i)Pr (21), (t)Bu (22)] was also prepared. Complexes 11-14 underwent an interesting hydrolysis process to give the cluster complex [Zr6(mu3-OH)8(OH)8(kappa2-bdmpza)8] (23). The structures of these complexes have been determined by spectroscopic methods, and the X-ray crystal structures of 7, 8, and 23 were also established.     

Water-soluble ruthenium(II) catalysts [RuCl2(eta6-arene)[P(CH2OH)3]] for isomerization of allylic alcohols and alkyne hydration

The novel water-soluble ruthenium(II) complexes [RuCl(2)(eta(6)-arene)[P(CH(2)OH)(3)]]2a-c and [RuCl(eta(6)-arene)[P(CH(2)OH)(3)](2)][Cl]3a-c have been prepared in high yields by reaction of dimers [[Ru(eta(6)-arene)(micro-Cl)Cl](2)](arene = C(6)H(6)1a, p-cymene 1b, C(6)Me(6)1c) with two or four equivalents of P(CH(2)OH)(3), respectively. Complexes 2/3a-c are active catalysts in the redox isomerization of several allylic alcohols into the corresponding saturated carbonyl compounds under water/n-heptane biphasic conditions. Among them, the neutral derivatives [RuCl(2)(eta(6)-C(6)H(6))[P(CH(2)OH)(3)]]2a and [RuCl(2)(eta(6)-p-cymene)[P(CH(2)OH)(3)]]2b show the highest activities (TOF values up to 600 h(-1); TON values up to 782). Complexes 2/3a-c also catalyze the hydration of terminal alkynes.