A dimeric titanium-containing polyoxometalate. Synthesis, characterization, and catalysis of H2O2-based thioether oxidation

The previously unknown titanium(IV)-containing mu-hydroxo dimeric heteropolytungstate (Bu4N)7[(PTiW11O39)2-OH] (TBA salt of H1) has been synthesized, starting from H5PTiW11O40, and characterized by elemental analysis, multinuclear (31P, 17O, 183W) NMR, IR, FAB-MS, cyclic voltammetry, and potentiometric titration. 31P NMR reveals that H1 (delta -12.76) readily forms in MeCN from the Keggin monomer (POM), PTiW11O40(5-) (2, delta -13.34), upon the addition of 1.5 equiv of H+, via the protonated species, P(TiOH)W11O39(4-) (H2, delta -13.44). The ratio of H1, 2, and H2, which are present in equilibrium in MeCN solution at 25 degrees C, depends on the concentration of both H+ and H2O. The Ti-O-Ti linkage readily reacts with nucleophilic reagents, such as H2O and ROH, to yield monomeric Keggin derivatives. mu-Hydroxo dimer H1 shows higher catalytic activity than 2 for thioether oxidation by hydrogen peroxide in acetonitrile. The reaction proceeds readily at room temperature and affords the corresponding sulfoxide and sulfone in ca. quantitative yield. The addition of H2O2 to H1 or H2 results in the formation of a peroxo complex, most likely the hydroperoxo complex P(TiOOH)W11O39(4-) (I), which has 31P NMR resonance at -12.43 ppm. The rate of the formation of I is higher from H2 than from H1. When H1 is used as a catalyst precursor, the rates of the thioether oxidation and peroxo complex formation increase with increasing H2O concentration, which favors the cleavage of H1 to H2. H2O2 in MeCN slowly converts 2 to another peroxotitanium complex, P(TiO2)W11O39(5-) (II), which has 31P NMR resonance at -12.98 ppm. Peroxo complexes I and II differ in their protonation state and interconvert fast on the 31P NMR time scale. Addition of 1 equiv of H+ completely converts II to I, while 1 equiv of OH- completely converts I to II. 31P NMR confirms that I is stable under turnover conditions (thioether, H2O2, MeCN). Contrary to two-phase systems such as dichloroethane/aqueous H2O2, no products resulting from the destruction of the Keggin POM were detected in MeCN in the presence of H2O2 (a 500-fold molar excess). The reactivity of I, generated in situ from II by adding 1 equiv of H+, toward organic sulfides under stoichiometric conditions was confirmed using both 31P NMR and UV-vis spectroscopy. This is a rare demonstration of the direct stoichiometric oxidation of an organic substrate by a titanium peroxo complex.     

First isolated active titanium peroxo complex: characterization and theoretical study

The protonated titanium peroxo complex [Bu(4)N](4)[HPTi(O(2))W(11)O(39)] (1) has been first prepared via interaction of the micro-oxo dimeric heteropolytungstate [Bu(4)N](8)[(PTiW(11)O(39))(2)O] (3) with an excess of 30% aqueous H(2)O(2) in MeCN. Peroxo complex 1 has been characterized by using elemental analysis, UV-vis, IR, resonance Raman (RR), (31)P and (183)W NMR spectroscopy, cyclic voltammetry, and potentiometric titration. The electronic and vibrational spectra of 1 are very similar to those of the well-known unprotonated titanium peroxo complex [Bu(4)N](5)[PTi(O(2))W(11)O(39)] (2), while (31)P and (183)W NMR spectra differ significantly. A compilation of the physicochemical techniques supports a monomeric Keggin type structure of 1 bearing one peroxo ligand attached to Ti(IV) in a eta(2)-coordination mode. The protonation of the titanium peroxo complex results in an increase of the redox potential of the peroxo group, E(1/2) = 1.25 and 0.88 V relative to Ag/AgCl reference electrode for 1 and 2, respectively. In contrast to 2, 1 readily reacts with 2,3,6-trimethylphenol (TMP) at 40 degrees C in MeCN to give 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol (BP) and 2,3,5-trimethyl-p-benzoquinone (TMBQ). The proportion between BP and TMBQ in the reaction products depends on the TMP/1 ratio. When a 2-fold excess of TMP is used, the main reaction product is BP (90%), while using a 2-fold excess of 1 leads to TMBQ (95%). On the basis of the product study, a homolytic oxidation mechanism that implicates the formation of phenoxyl radicals is suggested. The RR deuterium labeling experiments show that the activating proton is most likely localized at a Ti-O-W bridging oxygen rather than at the peroxo group. Theoretical calculations carried out at the DFT level on the protonated and unprotonated titanium peroxo derivatives also propose that the most stable complex is formed preferentially after protonation of the Ti-O-W site; however, both Ti-OH-W and TiOO-H protonated anions could coexist in solution.     

Zr(IV)-monosubstituted Keggin-type dimeric polyoxometalates: synthesis, characterization, catalysis of H2O2-based oxidations, and theoretical study

The previously unknown Zr(IV)-monosubstituted Keggin-type polyoxometalates (Zr-POMs), (n-Bu4N)7H[{PW11O39Zr(mu-OH)}2] (1), (n-Bu4N)8[{PW11O39Zr(mu-OH)}2] (2), and (n-Bu4N)9[{PW11O39Zr}2(mu-OH)(mu-O)] (3) differing in their protonation state, have been prepared starting from heteropolyacid H5PW11ZrO40.14H2O. The compounds were characterized by elemental analysis, potentiometric titration, X-ray single-crystal structure, and IR, Raman, and 31P and 183W NMR spectroscopy. The single-crystal X-ray analysis of 2 reveals that two Keggin structural units [PW11O39Zr]3- are linked through two hydroxo bridges Zr-(OH)-Zr with Zr(IV) in 7-fold coordination. The IR spectra of 1 and 2 show a characteristic band at 772 cm(-1), which moves to 767 cm(-1) for 3, reflecting deprotonation of the Zr-(OH)-Zr bond. Potentiometric titration with methanolic Bu4NOH indicates that 1-3 contain 2, 1, and 0 acid protons, respectively. (83W NMR reveals Cs symmetry of 2 and 3 in dry MeCN, while for 1, it discovers nonequivalence of its two subunits and their distortion resulting from localization of the acidic proton on one of the Zr-O-W bridging O atoms. The (31)P NMR spectra of 2 and 3 differ insignificantly in dry MeCN, showing only signals at delta -12.46 and -12.44 ppm, respectively, while the spectrum of 1 displays two resonances at delta -12.3 (narrow) and -13.2 (broad) ppm, indicating slow proton exchange on the (31)P NMR time scale. The theoretical calculations carried out at the density functional theory level on the dimeric species 1-3 propose that protonation at the Zr-O-Zr bridging site is more favorable than protonation at Zr-O-W sites. Calculations also revealed that the doubly bridged hydroxo structure is thermodynamically more stable than the singly bridged oxo structure, in marked contrast with analogous Ti- and Nb-monosubstituted polyoxometalates. The interaction of 1-3 with H(2)O and H(2)O(2) in MeCN has been studied by both (31)P and (183)W NMR. The stability of the [PW(11)O(39)ZrOH](4-) structural unit toward at least 100-fold excess of H2O2 in MeCN was confirmed by both NMR and Raman spectroscopy. The interaction of 1 and 2 with H2O in MeCN produces most likely monomeric species (n-Bu4N)3+n[PW11O39Zr(OH)(n(H2O)(3-n)] (n = 0 and 1) showing a broad 31P NMR signal at delta -13.2 ppm, while interaction with H2O2 leads to the formation of an unstable peroxo species (delta -12.3 ppm), which reacts rapidly with cyclohexene, producing 2-cyclohexen-1-one and trans-cyclohexane-1,2-diol. Both 1 and 2 show a pronounced catalytic activity in H2O2 decomposition and H2O2-based oxidation of organic substrates, including cyclohexene, alpha-pinene, and 2,3,6-trimethylphenol. The oxidation products are consistent with those of a homolytic oxidation mechanism. On the contrary, 3 containing no acid protons reacts with neither H2O nor H2O2 and shows negligible catalytic activity. The Zr-monosubstituted polyoxometalates can be used as tractable homogeneous probes of Zr single-site heterogeneous catalysts in studying mechanisms of H2O2-based oxidations.     

Investigation of the reactivity of arylamines, organo-hydrazines and tolylisocyanate towards [PW12-xMxO40]n- Keggin anions

Reaction of K7[A,alpha-PW9Mo2O39] with Na2MoO4.2H2O in a mixture of water/dioxane/hydrochloric acid and further precipitation with (Bu4N)Br provided (Bu4N)3[A,alpha-PW9Mo3O40](3). Analogous reaction with K7-xNax[alpha-PW11O39] is an alternative to the synthesis of (Bu4N)3[alpha-PW11O39{MoVIO}]2. Multinuclear NMR and ESI mass spectrometry have been used to interpret the reaction of (Bu4N)x[alpha-PW11O39{ReO}](x=3 1; x=4 1I), (Bu4N)x[alpha-PW11O39{MoO}](x=3 2; x=4 2I) and (Bu4N)3[A,alpha-PW9Mo3O40]3 by organohydrazines, arylamines, tolylisocyanate and tetraphenylphosphine imide.     

Bonding modes of stanna-closo-dodecaborate: eta1(Sn) to eta3(BH) rearrangement reactions in zwitterionic stanna-closo-dodecaborate ruthenium complexes

Reaction of the stanna-closo-dodecaborate salt [Bu3MeN]2[SnB11H11] with the dimeric ruthenium complex [Ru2(mu-Cl)3(triphos)2]Cl (triphos = {MeC(CH2PPh2)3}) in refluxing acetonitrile yields the zwitterionic compound [Ru(SnB11H11)(MeCN)2(triphos)] (4) which has been characterized by single-crystal X-ray diffraction analysis and solid-state NMR spectroscopy. Refluxing the zwitterion in acetone leads to an eta1(Sn) to eta3(BH) rearrangement with formation of [Ru(SnB1)H11)(triphos)] (5) whose structure has been confirmed by X-ray diffraction and multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, two isomeric zwitterions fac- and mer-[Ru(SnB11H11)(dppb)(MeCN)3] (6a, 6b) and their rearrangement reactions as well as their NMR properties are described.     

Investigations on the interaction of dichloroaluminum carboxylates with Lewis bases and water: an efficient road toward oxo- and hydroxoaluminum carboxylate complexes

A series of dichloroaluminum carboxylates [Cl(2)Al(O(2)CR)](2) (were R = Ph (1a), (t)Bu (1b), CHCH(2) (1c) and C(11)H(23) (1d)) were prepared and extended investigations on their structure and reactivity toward various Lewis bases and H(2)O performed. Compounds [Cl(2)Al(O(2)CR)](2) and their adducts with Lewis bases show a large structural variety, featuring both molecular and ionic forms with different coordination numbers of the metal center and various coordination modes of the carboxylate ligand. Upon addition of a Lewis base of moderate strength the molecular form [Cl(2)Al(O(2)CR)](2) equilibrates with new ionic forms. In the presences of 4-methylpyridine the six-coordinate Lewis acid-base adducts [Cl(2)Al(λ(2)-O(2)CR)(py-Me)(2)] [R = Ph (3a), (t)Bu (3b)] with a chelating carboxylate ligand were formed. The reactions of 1a, 1b, and 1d with 0.33 equiv of H(2)O in THF-toluene solution lead to oxo carboxylates [(Al(3)O)(O(2)CR)(6)(THF)(3)] [AlCl(4)] [where R = Ph (4a(THF)), (t)Bu (4b(THF)), and C(11)H(23) (4d(THF))] in high yield. The similar reaction of 1c in tetrahydrofuran (THF) afforded the chloro(hydroxo)aluminum acrylate [(ClAl)(2)(OH)(O(2)CC(2)H(3))(2) (THF)(4)][AlCl(4)] (5), while the hydrolysis of 1b in MeCN lead to the hydroxoaluminum carboxylate [Al(2)(OH)(O(2)C(t)Bu)(2)(MeCN)(6)][AlCl(4))(3)] (6). All compounds were characterized by elemental analysis, (1)H, (27)Al NMR, and IR spectroscopy, and the molecular structure of 1a, 3a, 3b, 4a(THF), 4b(THF), 4b(py-Me'), 5, and 6 were determined by single-crystal X-ray diffraction. The study provides a platform for testing transformations of secondary building units in Al-Metal-Organic Frameworks toward H(2)O and neutral donor ligands.     

Hexafluoroantimony(V) salts of the cationic Ti(IV) fluoride non metallocene complexes [TiF3(MeCN)3]+ and [TiF2L]2+ (L = 15-Crown-5 and 18-Crown-6). Preparation, characterization and thermodynamic stability

The cationic titanium fluoride containing complexes [fac-TiF3(MeCN)3][SbF6].MeCN (1), [trans-TiF2(15-Crown-5)][SbF6]2(2) and [trans-TiF2(18-Crown-6)][SbF6]2(2), were prepared by the reaction of TiF4, the molecular ligand and SbF5 in MeCN. Complexes 1-3 were characterized by X-ray single crystal analysis, elemental analysis, IR, NMR and mass spectroscopy. Titanium tetrafluoride reacts with the SbF5 in SO2 with the formation of fac-[TiF3(SO2)3]+, detected by 19F NMR. Application of the volume-based approach to thermodynamics (VBT) offers a means, for the first time, of exploring the energetics surrounding these materials and in the thermodynamic section a discussion of this new approach is provided. It emerges that the basis of the thermodynamic driving force of formation of [TiF3L3][SbF6](s) salts, that enforces the unfavourable [DeltaH degrees =+ 237 (+/-20) kJ mol(-1)] fluoride ion transfer from the Lewis acid TiF4(s) to SbF5(l) to give the hypothetical [TiF3]+[SbF6]-(s), is the higher Ti-L (L = ligand) bond energy in the cationic complexes [TiF3L3]+ as compared to that in the molecular adducts TiF4L2(s) and SbF5L(s) so giving rise to larger enthalpies of complexation of [TiF3]+(g) by 3L(g) compared to those for complexation of TiF4(g) by 2L(g) and SbF5(g) by 1L(g). Formation of the trans-[TiF2(15-Crown-5)]2+ and trans-[TiF2(18-Crown-6)]2+ is accounted for the stabilization of [TiF2]2+ cation by the five donor acceptor Ti-O contacts and the accompanying positive charge delocalization. Cationic titanium(IV) complexes fac-[TiF3MeCN)3-nLn]+(n= 0-3) and cis-[TiF318-Crown-6)]+, trans-[TiF2(Crown)]2+(Crown = 15-Crown-5 and 18-Crown-6) were obtained in MeCN solution by the reaction of fac-[TiF3(MeCN)3]+ and L = Et2, THF, H2 or crown ethers. Complexes fac-[TiF3(MeCN)3-nLn][SbF6] L = Et2, THF, H2O, crown ethers are unstable in MeCN solution and slowly decompose giving molecular complexes cis-TiF4L2, cis-TiF4(Crown), SbF5L, titanium oxofluoride and alkoxide complexes. The structure of the fac-[TiF3(MeCN)3]+ is similar to the fac-[TiCl3(MeCN)3]+ and the complexes trans-[TiF2L]2+ L = 15-Crown-5, 18-Crown-6 have very similar geometries to that of trans-[TiCl2(15-Crown-5)]+ showing that the essential features of coordination are the same for the cationic titanium chloride and fluoride complexes with MeCN and 15-Crown-5, 18-Crown-6.     

New reactivity and structural insights of alkali-metal-mediated alumination in directed ortho-alumination of a tertiary aromatic amide

The first reported sodium alkyl(TMP)aluminate reagent to be synthesised and crystallographically characterised, [TMEDA.Na(mu-TMP)(mu-(I)Bu)Al((I)Bu)2], reacts as an amido base towards phenylacetylene to form crystalline [(TMEDA)2.Na(mu-CCPh)(mu-(I)Bu)Al((I)Bu)2]; whereas the congeneric TMEDA-stabilised lithium (TMP)aluminate exhibits dual alkyl/amido basicity in its reaction with N,N-diisopropylbenzamide to form a novel heterobimetallic-heterotrianionic crystalline complex [{PhC(=O)N(iPr)2}.Li{2-[1-C(=O)N(iPr)2]C6H4}{Me2NCH2CH2N(Me)CH2}Al(iBu)2], which, in addition to having an ortho-deprotonated benzamide ligand, also contains a methyl-deprotonated TMEDA ligand and a neutral benzamide molecule ligated to lithium.     

Synthesis,Properties, Structure and Reactivity of Sodium 2,3,4,5-Tetra- tert -butylcyclopentaphosphanide

The reaction between Na, t BuPCl 2 , and PCl 3 in thf gives Na[ cyclo -( t Bu 4 P 5 )] ( 1 ). 1 reacts with PCl 3 to yield ( cyclo - t Bu 3 P 4 ) t BuPCl ( 2 ), and with a proton source, such as HCl, NH 4 Cl, or t BuCl, to give cyclo - t Bu 4 P 5 H ( 3 ). The reaction of 1 with [MCl 2 (PRR' 2 ) 2 ] (M = Ni; R = R' = Et; M = Pd, Pt, R = Ph, R' = Me) gives [Ni{ cyclo -( t Bu 3 P 5 )}(PEt 3 ) 2 ] ( 4 ), [Pd{ cyclo -( t Bu 4 P 5 )} 2 ] ( 5 ), and [PtCl{ cyclo -( t Bu 3 P 4 ) t BuP}(PPhMe 2 )] ( 6 ). 1-6 were characterized by 31 P{ 1 H} NMR spectroscopy, and 1 and 4-6 were also characterized by X-ray crystallography.     

New cyanometalate building units: synthesis and characterization of [Re(CN)(7)]3- and [Re(CN)(8)]3-

Two new cyanorhenate complexes of potential utility in constructing magnetic and photomagnetic materials are reported. Reaction of (Bu4N)CN with [ReCl6]2- in acetonitrile affords yellow (Bu4N)3[Re(CN)7] (1), featuring the pentagonal bipyramidal complex [Re(CN)7]3-. The spectral and magnetic properties of 1 indicate that the complex has an S = 1/2 ground state with considerable anisotropy in the g tensor. In aqueous solution, 1 reacts with Mn2+ ions to generate the three-dimensional cyano-bridged solid [fac-Mn(H2O)3][cis-Mn(H2O)2][Re(CN)7].3H2O (2) containing diamagnetic [Re(CN)7]4-. Addition of KIO4 to the reaction solution, originally intended to prevent reduction of the rhenium during solid formation, instead yields white (Bu4N)3[Re(CN)8] (3). As crystallized in K3[Re(CN)8].2MeCN (4.2MeCN), the diamagnetic [Re(CN)8]3- complex adopts a nearly perfect square antiprismatic coordination geometry. In solution, this species behaves analogously to the isoelectronic [M(CN)8]4- (M = Mo, W) complexes, apparently converting to a dodecahedral geometry and photooxidizing under UV radiation to give paramagnetic [Re(CN)8]2-.     

An unprecedented, reversible coordination mode rearrangement: eta3(B-H) vs.eta1(Sn) stanna-closo-dodecaborate coordination

The synthesis of the ruthenium stanna-closo-dodecaborate complex [Bu(3)MeN](2)[Ru(dppb)(MeCN)(2)(SnB(11)H(11))(2)] by an unprecedented, reversible eta(3)(B-H) to eta(1)(Sn) rearrangement of [Bu(3)MeN](2)[Ru(dppb)(SnB(11)H(11))(2)] is described and the product is characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction.     

磷酸三甲(丁)酯质子化的^3^1P和1HNMR研究

测量了与水无限混溶的磷酸三甲酯(TMP)质子化过程的^3^1P化学位移的变化,解析后得到H2O.TMP(H.M)和H2O.2TMP(H.2M)两配合物的平衡常数,用^1H NMR研究混合物中水的化学位移,找出了自由水^1H化学位移值与浓度的关系,并在TBP体系中进行验证.     

Ruthenium complexes with the stanna-closo-dodecaborate ligand: coexistence of eta1(Sn) and eta3(B-H) coordination

Four stanna-closo-dodecaborate complexes of ruthenium have been prepared and characterized by multinuclear NMR studies in solution and in the solid state. The solid-state structures of the dimeric zwitterions [[Ru(dppb)(SnB11H11)]2] (2) (dppb = bis(diphenylphosphino)butane), [[Ru(PPh3)2(SnB11H11)]2] (3), and the dianionic ruthenium complex [Bu3MeN]2[Ru(dppb)[2,7,8-(mu-H)3-exo-SnB11H11](SnB11H11)] (4) were determined by X-ray crystal structure analysis; they establish an unprecedented structural motif in the chemistry of heteroboranes and transition-metal fragments with the stanna-closo-dodecaborate moiety as a two-faced ligand that exhibits eta1(Sn) as well as eta3(B-H) coordination. The eta3-coordinated stannaborate in 4 and in the isostructural compound [Bu3MeN]2[Ru(PPh3)2[2,7,8-(mu-H)3-exo-SnB11H11](SnB11H11)] (5) shows fluxional behavior, which was studied in detail by using 31P[1H] EXSY and DNMR experiments. The activation parameters for the dynamic process of 5 are given.     

Functionalization of polyoxometalates: from Lindqvist to Keggin derivatives. 1. synthesis, solution studies, and spectroscopic and ESI mass spectrometry characterization of the rhenium phenylimido tungstophosphate [PW11O39(ReNC6H5)]4-

Reaction of [Bu(4)N](4)[H(3)PW(11)O(39)] with [Re(NPh)Cl(3)(PPh(3))(2)], in acetonitrile and in the presence of NEt(3), provided the first Keggin-type organoimido derivative [Bu(4)N](4)[PW(11)O(39)(ReNPh)] (Ph = C(6)H(5)) (1). The functionalization was clearly demonstrated by various techniques including (1)H and (14)N NMR, electrochemistry, and ESI mass spectrometry. Conditions for the formation of 1 are also discussed.     

Bulky 4-phosphacyclohexanones: diastereoselective complexations, orthometallations and unprecedented [3.1.1]metallabicycles

The 4-phosphacyclohexanones, 2,2,6,6-tetramethyl-1-phenyl-4-phosphorinanone (La), 1,2,6-triphenyl-4-phosphorinanone ((Ph)Lb), 1-cyclohexyl-2,6-diphenyl-4-phosphorinanone ((Cy)Lb) and 1-tert-butyl-2,6-diphenyl-4-phosphorinanone ((Bu)Lb) have been made by modifications of literature methods. Phosphines (R)Lb are each formed as mixtures of meso- and rac-diastereoisomers. Isomerically pure rac-(Ph)Lb, rac-(Cy)Lb and meso-(Bu)Lb can be isolated by recrystallisation from MeCN. Heating mixtures of isomers of (R)Lb with TsOH leads to isomerisations to give predominantly the meso-(R)Lb. The complex trans-[PdCl2(La)2] (1) is readily made from [PdCl2(NCPh)2] but the analogous platinum complex 2 has not been detected and instead, cyclometallation at the 3-position (alpha to the ketone) in the phosphacycle occurs to give trans-[PtCl(La)(La-3H)] (3) (where La-3H = La deprotonated at the 3-position) featuring a [3.1.1]metallabicycle as confirmed by X-ray crystallography. The analogous palladabicycle 4 has been detected upon treatment of 1 with Et3N in refluxing toluene. The type of complex formed by (R)Lb depends on which diastereoisomer (meso or rac) is involved. rac-(Ph)Lb (a mixture of R,R- and S,S-enantiomers, labelled alpha and beta) forms trans-[MCl2(rac-(Ph)Lb)2], M = Pd (5) or Pt (6), as mixtures of diastereoisomers (alphaalpha/betabeta and alphabeta forms). The structure of alphaalpha-6 has been determined by X-ray crystallography. Ligand competition experiments monitored by 31P NMR showed that Pd(II) and Pt(II) have a significant preference to bind rac-(Ph)Lb over meso-(Ph)Lb. meso-(Bu)Lb reacts with [PtCl2(NCBu(t))2] under ambient conditions to give the binuclear complex [Pt2Cl2(meso-(Bu)Lb-2'H)2] (7) where orthometallation has occurred on one of the exocyclic phenyl substituents as confirmed by X-ray crystallography. rac-(Bu)Lb reacts with [PtCl2(NCBu(t))2] to give a mononuclear cyclometallated species assigned the structure trans-[PtCl(rac-(Bu)Lb-2'H)((Bu)Lb)] (8) on the basis of its 31P NMR spectrum. rac-(Cy)Lb reacts with [PtCl2(NCBu(t))2] in refluxing toluene to give trans-[PtCl2(rac-(Cy)Lb)2] (9) and the crystal structure of alphabeta-9 has been determined.     

Synthesis and characterization of a family of penta- and tetra-manganese(III) complexes derived from an assembly system containing tert-butylphosphonic acid

A family of manganese complexes, [Mn 5O 3( t-BuPO 3) 2(MeCOO) 5(H 2O)(phen) 2] ( 1), [Mn 5O 3( t-BuPO 3) 2(PhCOO) 5(phen) 2] ( 2), [Mn 4O 2( t-BuPO 3) 2(RCOO) 4(bpy) 2] (R = Me, ( 3); R = Ph, ( 4)), NBu (n) 4[Mn 4O 2(EtCOO) 3(MeCOO) 4(pic) 2] ( 5), NR' 4[Mn 4O 2( i-PrCOO) 7(pic) 2] (R' = Bu (n) , ( 6); R' = Et, ( 7)), were synthesized and characterized. The seven manganese clusters were all prepared from a reaction system containing tert-butylphosphonic acid, Mn(O 2CR) 2 (R = Me, Ph) and NR' 4MnO 4 (R' = Bu (n) , Et) with similar procedures except for using different N-containing ligands (1,10-phenanthroline (phen), 2,2'-bipyridine (bpy) and picolinic acid (picH)) as coligands. The structures of these complexes vary with the N-containing donors. Both the cores of complexes 1 and 2 feature three mu 3-O and two capping t-BuPO 3 (2-) groups bridging five Mn (III) atoms to form a basket-like cage structure. Complexes 3 and 4 both have one [Mn 4(mu 3-O) 2] (8+) core with four coplanar Mn (III) atoms disposed in an extended "butterfly-like" arrangement and two capping mu 3- t-BuPO 3 (2-) binding to three manganese centers above and below the Mn 4 plane. Complexes 5, 6, and 7 all possess one [Mn 4(mu 3-O) 2] (8+) core just as complexes 3 and 4, but they display a folded "butterfly-like" conformation with the four Mn (III) atoms nonplanar. Thus, the seven compounds are classified into three types, and three representative compounds 1.2H 2O.MeOH.MeCN , 3.6H 2O.2MeCOOH , and 5.0.5H 2O have been characterized by IR spectroscopy, ESI-MS spectroscopy, magnetic measurements and in situ UV-vis-NIR spectroelectrochemical analysis. Magnetic susceptibility measurements reveal the existence of both ferromagnetic and antiferromagnetic interactions between the adjacent Mn (III) ions in compound 1.2H 2O.MeOH.MeCN , and antiferromagnetic interactions in 3.6H 2O.2MeCOOH and 5.0.5H 2O. Fitting the experimental data led to the following parameters: J 1 = -2.18 cm (-1), J 2 = 6.93 cm (-1), J 3 = -13.94 cm (-1), J 4 = -9.62 cm (-1), J 5 = -11.17 cm (-1), g = 2.00 ( 1.2H 2O.MeOH.MeCN ), J 1 = -5.41 cm (-1), J 2 = -35.44 cm (-1), g = 2.13, zJ' = -1.55 cm (-1) ( 3.6H 2O.2MeCOOH ) and J 1 = -2.29 cm (-1), J 2 = -35.21 cm (-1), g = 2.02, zJ' = -0.86 cm (-1) ( 5.0.5H 2O ).     

Resorcinol based acyclic dimeric and cyclic di- and tetrameric cyclodiphosphazanes: synthesis, structural studies, and transition metal complexes

The condensation reaction of resorcinol with cis-[ClP(μ-N(t)Bu)(2)PN(H)(t)Bu] produced a difunctional derivative 1,3-C(6)H(4)[OP(μ-N(t)Bu)(2)PN(H)(t)Bu](2) (1), whereas the similar reaction with [ClP(μ-N(t)Bu)](2) resulted in the formation of a 1:1 mixture of dimeric and tetrameric species, [{P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (2a) and [{P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](4) (2b), which were separated by repeated fractional crystallization and column chromatography. The reaction of dimer 2a with H(2)O(2) and selenium produces tetrachalcogenides [{(O)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (3) and [{(Se)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (4), respectively. The reaction between the dimer (2a) and [Pd(μ-Cl)(η(3)-C(3)H(5))](2) or AuCl(SMe(2)) yielded the corresponding tetranuclear complexes, [{((Cl)(η(3)-C(3)H(5))Pd)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (5) and [{(ClAu)P(μ-N(t)Bu)}(2){1,3-(O)(2)-C(6)H(4)}](2) (6) in good yield. The complexes 5 and 6 are the rare examples of phosphorus macrocycles containing two or more exocyclic transition metal fragments. Treatment of 1 with copper halides in 1:1 molar ratio resulted in the formation of one-dimensional (1D) coordination polymers, [(CuX){1,3-C(6)H(4){OP(μ-N(t)Bu)(2)PN(H)(t)Bu}}(2)](n) (7, X = Cl; 8, X = Br; 9, X = I), which showed the helical structure in solid state because of intramolecular hydrogen bonding, whereas similar reactions of 1 with 4 equiv of copper halides also produced 1D-coordination polymers, [(Cu(2)X(2))(2){1,3-C(6)H(4){OP(μ-N(t)Bu)(2)PN(H)(t)Bu}(2)}](n) (10, X = Cl; 11, X = Br; 12, X = I), but containing Cu(2)X(2) rhomboids instead of CuX linkers. The crystal structures of 1, 2a, 2b, 4, 7-9, and 12 were established by X-ray diffraction studies.     

Oxo- and imidovanadium complexes incorporating methylene- and dimethyleneoxa-bridged calix[3]- and -[4]arenes: synthesis, structures and ethylene polymerisation catalysis

Reaction of [V(X)(OR)3] (X=O, Np-tolyl; R=Et, nPr or tBu) with p-tert-butylhexahomotrioxacalix[3]areneH3, LH3, affords the air-stable complexes [{V(X)L}n] (X=O, n=1 (1); X=Np-tolyl, n=2 (2)). Alternatively, 1 is readily available either from interaction of [V(mes)3THF] with LH3, and subsequent oxidation with O2 or upon reaction of LLi3 with [VOCl3]. Reaction of [V(Np-tolyl)(OtBu)3] with 1,3-dimethylether-p-tert-butylcalix[4]areneH2, Cax(OMe)2(OH)2, afforded [{VO(OtBu)}2(mu-O)Cax(OMe)2(O)2].2 MeCN (42 MeCN), in which two vanadium atoms are bound to just one calix[4]arene ligand; the n-propoxide analogue of 4, namely [{VO(OnPr)}2(mu-O)Cax(OMe)2(O)2].1.5 MeCN (51.5 MeCN), has also been isolated from a similar reaction using [V(O)(OnPr)3]. Reaction of [VOCl3], LiOtBu, (Me3Si)2O and Cax(OMe)2(OH)2 gave [{VO(OtBu)Cax(OMe)2(O)2}2Li4O2].8 MeCN (68 MeCN), in which an Li4O4 cube (two of the oxygen atoms are derived from the calixarene ligands) is sandwiched between two Cax(OMe)2(O)2. The reaction between [V(Np-tolyl)(OtBu)3] and Cax(OMe)2(OH)2, afforded [V(Np-tolyl)(OtBu)2Cax(OMe)2(O)(OH)]5 MeCN (75 MeCN), in which two tert-butoxide groups remain bound to the tetrahedral vanadium atom, which itself is bound to the calix[4]arene through only one phenolic oxygen atom. Reaction of p-tert-butylcalix[4]areneH4, Cax(OH)4 and [V(Np-tolyl)(OnPr)3] led to loss of the imido group and formation of the dimeric complex [{VCax(O)4(NCMe)}2].6 MeCN (86 MeCN). Monomeric vanadyl oxo- and imidocalix[4]arene complexes [V(X)Cax(O)3(OMe)(NCMe)] (X=O (11), Np-tolyl (12)) were obtained by the reaction of the methylether-p-tert-butylcalix[4]areneH3, Cax(OMe)(OH)3, and [V(X)(OR)3] (R=Et or nPr). Vanadyl calix[4]arene fragments can be linked by the reaction of 2,6-bis(bromomethyl)pyridine with Cax(OH)4 and subsequent treatment with [VOCl3] to afford the complex [{VOCax(O)4}2(mu-2,6-(CH2)2C5H3N)].4 MeCN (134 MeCN). The compounds 1-13 have been structurally characterised by single-crystal X-ray diffraction. Upon activation with methylaluminoxane, these complexes displayed poor activities, however, the use of dimethylaluminium chloride and the reactivator ethyltrichloroacetate generates highly active, thermally stable catalysts for the conversion of ethylene to, at 25 degrees C, ultra-high-molecular-weight (>5, 500,000), linear polyethylene, whilst at higher temperature (80 degrees C), the molecular weight of the polyethylene drops to about 450,000. Using 1 and 2 at 25 degrees C for ethylene/propylene co-polymerisation (50:50 feed) leads to ultra-high-molecular-weight (>2,900,000) polymer with about 14.5 mol% propylene incorporation. The catalytic systems employing the methyleneoxa-bridged complexes 1 and 2 are an order of magnitude more active than the bimetallic complexes 5 and 13, which, in turn, are an order of magnitude more active than pro-catalysts 8, 11 and 12. These differences in activity are discussed in terms of the structures of each class of complex.     

Metal-free and dicopper(II) complexes of Schiff base [2 + 2] macrocycles derived from 2,2'-iminobisbenzaldehyde: syntheses, structures, and electrochemistry

Three new bis-terdentate Schiff base [2 + 2] macrocycles (H(2)L(Et), H(2)L(Pr), and H(2)L(Bu)) have been prepared in high yields by 1:1 condensation of 2,2'-iminobisbenzaldehyde with 1,2-diaminoethane, 1,3-diaminopropane, and 1,4-diaminobutane, respectively. Metalation of these macrocycles yields the corresponding dicopper(II) acetate (1, 2, and 3) and tetrafluoroborate (4, 5, and 6) complexes. The structures of H(2)L(Et), H(2)L(Pr), H(2)L(Bu), [Cu(II)(2)L(i)(OAc)(2)]·solvents (where i is Et, Pr or Bu) and [Cu(II)(2)L(Pr)(DMF)(4)] (BF(4))(2)·0.5H(2)O are reported. Intramolecular hydrogen bonding is a feature of the metal-free macrocycles. The copper(II) centers in [Cu(II)(2)L(i)(OAc)(2)]·solvents are four coordinate, and the macrocycles have U-shaped (Et, Bu) or stepped (Pr) conformations. Complex 5 crystallizes with two dimethylformamide (DMF) molecules bound per five coordinate copper(II) center. Electrochemical studies revealed ligand based oxidations for all of the macrocycles and complexes. Complexes 1 and 2 undergo two quasi-reversible oxidations in DCM which are associated with the deposition of a visible film on the electrode after multiple scans in this oxidative region, suggestive of electropolymerization. Complexes 4-6, studied in MeCN, have Cu(II) → Cu(I) redox potentials at more positive potentials than for 1-3.     

Preparation and substitution chemistry of [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6]. A useful precursor for pseudohalide, acetate, and organometallic complexes containing the [W6Cl8](4+) core

The tosylate (p-toluenesulfonate) cluster [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6] (1) has been prepared and characterized by IR and NMR spectroscopy, elemental analysis, and an X-ray crystal structure. This cluster complex is shown to be a useful starting material for the preparation of pseudohalide clusters, [Bu4N]2[W6Cl8(NCQ)6] (Q = O (2), S (3), and Se (4)), in high yields. Cluster 1 also serves as a precursor to the new cluster compounds: [Bu4N]2[W6Cl8(O2CCH3)6] (5), [Bu4N]2[W6Cl8((mu-NC)Mn(CO)2(C5H5))6] (6), [W6Cl8((mu-NC)Ru(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (7), and [W6Cl8((mu-NC)Os(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (8). X-ray crystal structures are reported for 1, 4, and 5.