Synthesis and characterization of mixed-substituent N-silylphosphoranimines

The preparation of a large series of new N-silyl-P-alkylphosphoranimines and their (silylamino)phosphine precursors is reported. Oxidative bromination of the P-functional (silylamino)phosphines, (Me(3)Si)(2)NP(R)X [R = n-Pr, n-Bu, i-Pr, t-Bu; X = Br, OR' (R' = CH(2)CF(3), Ph)], occurred smoothly at 0 degrees C and afforded the desired P-bromophosphoranimines, Me(3)SiN=P(R)(X)Br. Nucleophilic substitution reactions of the P-dibromo members of this series with LiOR' gave the corresponding P-trifluoroethoxy- and P-phenoxyphosphoranimines, Me(3)SiN=P(R)(OR')(2) (R' = CH(2)CF(3), Ph). All of these N-silylphosphoranimines, which are potential precursors to new cyclic and/or polymeric phosphazenes, were obtained as thermally stable, distillable liquids and were characterized by NMR ((1)H, (13)C, and (31)P) spectroscopy and elemental analysis.     

Direct addition of alcohols to organonitriles activated by ligation to a platinum(IV) center

Treatment of trans-[PtCl(4)(RCN)(2)] (R = Me, Et) with R'OH (R' = Me, Et, n-Pr, i-Pr, n-Bu) at 45 degrees C in all cases allowed the isolation of the trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] imino ester complexes, while the reaction between cis-[PtCl(4)(RCN)(2)] and the least sterically hindered alcohols (methanol and ethanol) results in the formation of cis-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R/R' = Me/Me) or trans-[PtCl(4)[(E)-NH=C(Et)OR'](2)] (R' = Me, Et), the latter being formed via thermal isomerization (ROH, reflux, 3 h) of the initially formed corresponding cis isomers. The reaction between alcohols R'OH and cis-[PtCl(4)(RCN)(2)] (R = Me, R' = Et, n-Pr, i-Pr, n-Bu; R = Et; R' = n-Pr, i-Pr, n-Bu), exhibiting greater R/R' steric congestion, allowed the isolation of cis-[PtCl(4)[(E)-NH=C(R)OR'][(Z)-NH=C(R)OR']] as the major products. The alcoholysis reactions of poorly soluble [PtCl(4)(RCN)(2)] (R = CH(2)Ph, Ph) performed under heterogeneous conditions, directly in the appropriate alcohol and for a prolonged time and, for R = Ph, with heating led to trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R = CH(2)Ph, R' = Me, Et, n-Pr, i-Pr; R = Ph, R' = Me) isolated in moderate yields. In all of the cases, in contrast to platinum(II) systems, addition of R'OH to the organonitrile platinum(IV) complexes occurs under mild conditions and does not require a base as a catalyst. The formed isomerically pure (imino ester)Pt(IV) complexes can be reduced selectively, by Ph(3)P=CHCO(2)Me, to the corresponding isomers of (imino ester)Pt(II) species, exhibiting antitumor activity, without change in configuration of the imino ester ligands. Furthemore, the imino esters NH=C(R)OR' can be liberated from both platinum(IV) and platinum(II) complexes [PtCl(n)[H=C(R)OR'](2)] (n = 2, 4) by reaction with 1,2-bis(diphenylphosphino)ethane and pyridine, respectively. All of the prepared compounds were characterized by elemental analyses (C, H, N), FAB mass spectrometry, IR, and (1)H, (13)C[(1)H], and (195)Pt (metal complexes) NMR spectroscopies; the E and Z configurations of the imino ester ligands in solution were determined by observation of the nuclear Overhauser effect. X-ray structure determinations were performed for trans-[PtCl(4)[(E)-NH=C(Me)OEt](2)] (2), trans-[PtCl(4)[(E)-NH=C(Et)OEt](2)] (10), trans-[PtCl(4)[(E)-NH=C(Et)OPr-i](2)] (11), trans-[PtCl(4)[(E)-NH=C(Et)OPr-n](2)] (12), and cis-[PtCl(4)[(E)-NH=C(Et)OMe](2)] (14). Ab initio calculations have shown that the EE isomers are the most stable ones for both platinum(II) and platinum(IV) complexes, whereas the most stable configurations for the ZZ isomers are less stable than the respective EZ isomers, indicating an increase of the stability on moving from the ZZ to the EE configurations which is more pronounced for the Pt(IV) complexes than for the Pt(II) species.     

Non-innocent behaviour of imido ligands in the reactions of silanes with half-sandwich imido complexes of Nb and V: a silane/imido coupling route to compounds with nonclassical Si--H interactions

Reactions of imido complexes [M(Cp)(=NR')(PR'3)2] (M=V, Nb) with silanes afford a plethora of products, depending on the nature of the metal, substitution at silicon and nitrogen and the steric properties of the phosphine. The main products are [M(Cp)(=NR')(PR3)(H)(SiRnCl3-n)] (M=V, Nb; R'=2,6-diisopropylphenyl (Ar), 2,6-dimethylphenyl (Ar')), [Nb(Cp)(=NR')(PR'3)(H)(SiPhR2)] (R2=MeH, H2), [Nb(Cp)(==NR')(PR'3)(Cl)(SiHRnCl2-n)] and [Nb(Cp)(eta 3-N(R)SiR2--H...)(PR'3)(Cl)]. Complexes with the smaller Ar' substituent at nitrogen react faster, as do more acidic silanes. Bulkier groups at silicon and phosphorus slow down the reaction substantially. Kinetic NMR experiments supported by DFT calculations reveal an associative mechanism going via an intermediate N-silane adduct [Nb(Cp){=N(-->SiHClR2)R'}(PR'3)2] bearing a penta-coordinate silicon centre, which then rearranges into the final products through a Si--H or Si--Cl bond activation process. DFT calculations show that this imido-silane adduct is additionally stabilized by a Si--HM agostic interaction. Si--H activation is kinetically preferred even when Si--Cl activation affords thermodynamically more stable products. The niobium complexes [NbCp(=NAr)(PMe3)(H)(SiR2Cl)] (R=Ph, Cl) are classical according to X-ray studies, but DFT calculations suggest the presence of interligand hypervalent interactions (IHI) in the model complex [Nb(Cp) (==NMe)(PMe3)(H)(SiMe2Cl)]. The extent of Si--H activation in the beta-Si--HM agostic complexes [Cp{eta 3-N(R')SiR2--H}M(PR'3)(Cl)] (R'=PMe3, PMe2Ph) primarily depends on the identity of the ligand trans to the Si--H bond. A trans phosphine leads to a stronger Si--H bond, manifested by a larger J(Si--H) coupling constant. The Si--H activation diminishes slightly when a less basic phosphine is employed, consistent with decreased back-donation from the metal.     

Base induced P-C bond cleavage in a coordinated bis(dimethylphosphino)methane ligand

Treatment of fac-[Mn(CNR)(CO)3{(PMe2)2CH2}]ClO4 (1a R = Ph, R = tBu) with KOH produced the cleavage of one of the P-C bonds of the coordinated dmpm ligand, resulting in the formation of phosphine-phosphinite complexes fac-[Mn(PMe2O)(CNR)(CO)3(PMe3)] (2a,b). Alkoxides such as NaOMe and NaOEt promoted similar processes in 1a,b, yielding fac-[Mn(CNR)(CO)3(PMe3)(PMe2OR')]ClO4 (3a R = tBu, R' = Me; 3b R = Ph, R' = Me; 4a R = tBu, R' = Et; 4b R = Ph, R' = Et) derivatives. The phosphinite ligand in 2a, b can be sequentially protonated by addition of 0.5 and 1 equivalent of HBF4 leading to fac-[{Mn(CNR)(CO)3(PMe3)(PMe2O)}2H]BF4 (6a,b) and fac-[Mn(CNR)(CO)3(PMe3)(PMe2OH)]BF4 (5a,b), respectively.     

Carbon [bond] hydrogen bond activation by titanium imido complexes. Computational evidence for the role of alkane adducts in selective C [bond] H activation

This paper reports calculations that probe the role of R (hydrocarbon) and R' (ligand substituent) effects on the reaction coordinate for C [bond] H activation: Ti(OR')(2)(=NR') + RH --> adduct --> transition state --> (OR')(2)Ti(N(H)R')(R). Compounds with R = H, Me, Et, Vy, cPr, Ph, Cy, Bz, and cubyl are studied using quantum (R' = H, SiH(3), SiMe(3)) and classical (R' = Si(t)Bu(3)) techniques. Calculated geometries are in excellent agreement with data for experimental models. There is little variability in the calculated molecular structure of the reactants, products, and most interestingly, transition states as R and R' are changed. Structural flexibility is greatest in the adducts Ti(OR')(2)(=NR')...HR. Despite the small structural changes observed for Ti(OR')(2)(double bond] NR') with different R', significant changes are manifested in calculated electronic properties (the Mulliken charge on Ti becomes more positive and the Ti [double bond] N bond order decreases with larger R'), changes that should facilitate C [bond] H activation. Substantial steric modification of the alkane complex is expected from R [bond] R' interactions, given the magnitude of Delta G(add) and the conformational flexibility of the adduct. Molecular mechanics simulations of Ti(OSi(t)Bu(3))(2)([double bond] NSi(t)Bu(3))...isopentane adducts yield an energy ordering as a function of the rank of the C [bond] H bond coordinated to Ti that is consistent with experimental selectivity patterns. Calculated elimination barriers compare very favorably with experiment; larger SiH(3) and TMS ligand substituents generally yield better agreement with experiment, evidence that the modeling of the major contributions to the elimination barrier (N [bond] H and C [bond] H bond making) is ostensibly correct. Calculations indicate that weakening the C [bond] H bond of the hydrocarbon yields a more strongly bound adduct. Combining the different conclusions, the present computational research points to the adduct, specifically the structure and energetics of the substrate/Ti-imido interaction, as the main factor in determining the selectivity of hydrocarbon (R) C [bond] H activation.     

螺[1-溴-4-(1R,2S,5R)-l-孟氧基-5-氧杂-6-氧代双环[3.1.0]己烷-2,2'-(3'-α-膦酸二乙酯基-(S)-苯甲氧基-4'-l-(1R,2S,5R)-孟氧基丁内酯)]的晶体结构

报道了标题化合物合成和晶体结构。X-射线结构分析表明,该化合物的分子式为C39H58BrO10P,Mr = 797.74,晶体属于单斜晶系,空间群为P21,晶胞参数a = 12.858(3), b = 25.130(5), c = 14.125(3) ? = 105.15(3), V = 4405(2) ?, Z = 4, Dc = 1.203 g/cm3, ?= 1.019 mm-1, F(000) = 1688,R = 0.0726, wR = 0.1201,共收集到9691个独立衍射点,其中可观测点5638个(I≥2s(I))。每个分子中有6个环,13个手性中心,2个五员环呈信封式构象,并分别与三员环组合成[2.4]螺环和[3.1.0]桥环化合物,4个新生成的手性中心的绝对构型为C(6)(S), C(7)(S), C(3)(R), C(2)(R),新引入的磷酸酯官能团C(9)为S构型。     

Synthesis and structures of aluminum alkanethiolate complexes

The homoleptic aluminum thiolate complex [Al(mu-S-t-Bu)(S-t-Bu)(2)](2) was prepared by reacting AlBr(3) with NaS-t-Bu while the analogous 2-propanethiolate complex [Al(mu-S-i-Pr)(S-i-Pr)(2)](2) was synthesized by reacting AlH(3)(OEt(2)) with i-PrSH. In the solid state, the dimers have tetrahedral Al atoms and anti-Al(mu-SR)(2)Al four-member rings. The attempted synthesis of [Al(mu-S-t-Bu)(S-t-Bu)(2)](2) by reacting Al(N-i-Pr(2))(3) with t-BuSH in THF solvent yielded the thermally stable THF adduct Al(S-t-Bu)(3)(THF). The same reaction in diethyl ether solvent produced a mixture of [Al(mu-mgr;-S-t-Bu)(S-t-Bu)(2)](2) and the salt [i-Pr(2)NH(2)][Al(S-t-Bu)(4)]. In the solid-state structure of the salt, the anion [Al(S-t-Bu)(4)](-) has a distorted tetrahedral geometry. Reactions of [Al(NMe(2))(3)](2) and AlH(3)(NMe(2)Et) with the alkanethiols yielded stable amine adducts Al(SR)(3)(R'NMe(2)) (R = i-Pr or t-Bu; R' = H or Et). The ligand adducts Al(S-i-Pr)(3)(HNMe(2)) and Al(S-t-Bu)(3)(THF) have distorted trigonal pyramidal geometries in the solid state. Three of the new compounds, [Al(mu-S-i-Pr)(S-i-Pr)(2)](2) and Al(SR)(3)(HNMe(2)) (R = i-Pr or t-Bu), are viable precursor candidates for the chemical vapor deposition of aluminum sulfide films because they are thermally stable, volatile liquids at moderate temperatures.     

Aminocyclopentadienyl ruthenium complexes as racemization catalysts for dynamic kinetic resolution of secondary alcohols at ambient temperature

Aminocyclopentadienyl ruthenium complexes, which can be used as room-temperature racemization catalysts with lipases in the dynamic kinetic resolution (DKR) of secondary alcohols, were synthesized from cyclopenta-2,4-dienimines, Ru(3)(CO)(12), and CHCl(3): [2,3,4,5-Ph(4)(eta(5)-C(4)CNHR)]Ru(CO)(2)Cl (4: R = i-Pr; 5: R = n-Pr; 6: R = t-Bu), [2,5-Me(2)-3,4-Ph(2)(eta(5)-C(4)CNHR)]Ru(CO)(2)Cl (7: R = i-Pr; 8: R = Ph), and [2,3,4,5-Ph(4)(eta(5)-C(4)CNHAr)]Ru(CO)(2)Cl (9: Ar = p-NO(2)C(6)H(4); 10: Ar = p-ClC(6)H(4); 11: Ar = Ph; 12: Ar = p-OMeC(6)H(4); 13: Ar = p-NMe(2)C(6)H(4)). The tests in the racemization of (S)-4-phenyl-2-butanol showed that 7 is the most active catalyst, although the difference decreased in the DKR. Complex 4 was used in the DKR of various alcohols; at room temperature, not only simple alcohols but also functionalized ones such as allylic alcohols, alkynyl alcohols, diols, hydroxyl esters, and chlorohydrins were successfully transformed to chiral acetates. In mechanistic studies for the catalytic racemization, ruthenium hydride 14 appeared to be a key species. It was the major organometallic species in the racemization of (S)-1-phenylethanol with 4 and potassium tert-butoxide. In a separate experiment, (S)-1-phenylethanol was racemized catalytically by 14 in the presence of acetophenone.     

Spontaneous resolution of chiral polyoxometalate-based compounds consisting of 3D chiral inorganic skeletons assembled from different helical units

Four enantiomerically pure 3D chiral POM-based compounds, [Ni(2)(bbi)(2)(H(2)O)(4)V(4)O(12)]2 H(2)O (1 a and 1 b) and [Co(bbi)(H(2)O)V(2)O(6)] (2 a and 2 b) (bbi=1,1'-(1,4-butanediyl)bisimidazole) based on the achiral ligand, different vanadate chains, and different metal centers have been synthesized by hydrothermal methods. Single-crystal X-ray diffraction analyses revealed that 1 a and 1 b, and 2 a and 2 b, respectively, are enantiomers. In 1 a and 1 b two kinds of vanadate chains with different screw axes link Ni cations to generate 3D chiral inorganic skeletons, which are connected by the achiral bbi ligands to form complicated 3D 3,4-connected chiral self-penetrating frameworks with (7(2)8)(7(2)8(2)9(2))(7(3)8(2)10) topology. They represent the first examples of chiral self-penetrating frameworks known for polyoxometalate (POM) systems. Contrary to 1 a and 1 b, in 2 a and 2 b the vanadate chains link Co(II) cations to generate 3D chiral inorganic skeletons, which are assembled from two kinds of heterometallic helical units of opposite chirality along the c axes. The chiral inorganic skeletons are connected by bbi to form 3D 3,4-connected chiral POM-based frameworks with (6(2)8)(2)(6(2)8(2)10(2)) topology. It is believed that the asymmetrical coordination modes of the metal cations in 1 a-2 b generate the initial chiral centers, and that the formation of the various helical units and the hydrogen bond interactions are responsible for preservation of the chirality and spontaneous resolution when the chirality is extended into the homochiral 3D-networks. This is the first known report of chiral POM-based compounds consisting of 3D chiral inorganic skeletons being obtained by spontaneous resolution upon crystallization in the absence of any chiral source, which may provide a rational strategy for synthesis of chiral POM-based compounds by using achiral ligands and POM helical units.     

Unusual reactivity of methylphosphaalkyne (PCMe) toward digermenes and distannenes: stepwise formations of bridged 2,3,5,6-tetraphospha-1,4-dimethylidenecyclohexanes

Reactions of methylphosphaalkyne, PCMe, with a digermene, R' 2GeGeR' 2 (R' = -CH(SiMe 3) 2), and two distannenes, R' 2SnSnR' 2 and Ar' 2SnSnAr' 2 (Ar' = C 6H 2Pr (i) 3-2,4,6), have given moderate to high yields of the first bridged 2,3,5,6-tetraphospha-1,4-dimethylidenecyclohexanes, [R 2E{C(Me)(H)PC(CH 2)P}] 2 (R = R' or Ar', E = Sn or Ge), all of which have been structurally characterized. Their mechanisms of formation are thought to involve successive [2 + 1] and [2 + 2] phosphaalkyne cycloaddition, heterocycle rearrangement, phosphaalkene/vinylphosphine tautomerization, and intermolecular hydrophosphination reactions. In one reaction, two intermediates have been spectroscopically observed and one trapped by coordination to one or two W(CO) 5 fragments, yielding the first diphosphagermole complexes, {[W(CO) 5} 1or2{R' 2Ge[C(Me)PC(Me)P]}], which have been structurally characterized. Differences between the reactivities of PCMe and PCBu (t) are highlighted.     

Structure and H(2)-Loss Energies of OsHX(H(2))(CO)L(2) Complexes (L = P(t-Bu)(2)Me, P(i-Pr)(3); X = Cl, I, H): Attempted Correlation of (1)J(H-D), T(1min), and DeltaG()

1J(H-D), T(1min) and k(1) for H(2) dissociation from OsHX(H(2))(CO)L(2) have been measured for X = Cl, I, H (L = P(t-Bu)(2)Me or P(i-Pr)(3)), as well as for OsCl(2)(H(2))(CO)(P(i-Pr)(3))(2). For comparison, new data (including previously unobserved coupling constants) have been reported for W(HD)(CO)(3)(P(i-Pr)(3))(2). A comprehensive consideration of T(1min) data for over 20 dihydrogen complexes containing only 1-2 phosphines cis to H(2), together with a consideration of the shortest "conceivable" H-H distance for H(2) bound to a d(4) or d(6) metal, is used to argue that the "fast spinning" model is not appropriate for determining r(H-H) in such complexes. Regarding OsHX(H(2))(CO)L(2), the stronger electron-donor (lighter) halide, when cis to H(2), facilitates loss of H(2). The complete absence of pi-donor ability when X = H renders H(2) loss most difficult. However, a pi-donor trans to H(2) also makes H(2) loss unobservable. Within the series of isoelectronic, structurally analogous Os complexes, a longer H-H bond shows a larger DeltaG() for H(2) loss. However, this correlation does not continue to W(H(2))(CO)(3)(P(i-Pr)(3))(2), which has r(H-H) comparable to that of OsH(halide)(H(2))(CO)(P(i-Pr)(3))(2), but a significantly higher DeltaG(). This may originate from lack of a pi-donor ligand to compensate as H(2) leaves W.     

Neutral (bis-beta-diketonato) iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) metallocycles: structural, electrochemical and solvent extraction studies

Neutral dimeric metallocyclic complexes of type [M(2)(L(1))(2)B(n)] (where M = cobalt(II), nickel(II) and zinc(II), L(1) is the doubly deprotonated form of a 1,3-aryl linked bis-beta-diketone ligand of type 1,3-bis(RC(O)CH(2)C(O))C(6)H(4) (R=Me, n-Pr, t-Bu) and B is pyridine (Py) or 4-ethylpyridine (EtPy)) have been synthesised, adding to similar complexes already reported for copper(II). New lipophilic ligand derivatives with R = octyl or nonyl were also prepared for use in solvent extraction experiments. Structural, electrochemical and solvent extraction investigations of selected metal complex systems from the above series are reported, with the X-ray structures of [Co(2)(L(1))(2)(Py)(4)] x 2.25CHCl(3) x 0.5H(2)O (R=Pr), [Co(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Ni(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Zn(2)(L(1))(2)(EtPy)(2)] (R=Me) and [Zn(2)(L(1))(2)(EtPy)(4)] (R=t-Bu) being presented. The electrochemistry of H(2)L(1) (R=t-Bu) and of [Fe(2)(L(1))(3)], [Co(2)(L(1))(2)(Py)(4)], [Ni(2)(L(1))(2)(Py)(4)], [Cu(2)(L(1))(2)] and [Zn(2)(L(1))(2)(Py)(2)] has been examined. Oxidative processes for the complexes are dominantly irreversible, but several examples of quasireversible behaviour were observed and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as a metal-centred oxidation. The reduction processes for the respective metal complexes are not simple, and irreversible in most cases. Solvent extraction studies (water/chloroform) involving variable concentrations of metal, bis-beta-diketone and heterocyclic base have been performed for cobalt(II) and zinc(II) using a radiotracer technique to probe the stoichiometries of the extracted species in each case. Synergism was observed when 4-ethylpyridine was added to the bis-beta-diketone ligand in the chloroform phase. Competitive extraction studies show a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).     

Bis(isothiocyanato)bis(phosphine) complexes of group 10 metals: reactivity toward organic isocyanides

Treatment of Ni(NCS)2(PMe2Ph)2 with organic isocyanides CN-R gave five-coordinate isocyanide Ni(II) complexes, Ni(CN-R)(NCS)2(PMe2Ph)2 (R = C6H3-2,6-Me2 (1), t-Bu (2)). Interestingly, the corresponding reaction of Ni(NCS)2(P(n-Pr)3)2 with 2 equiv. of CN-t-Bu gave an unusual compound, which exists as an ion pair of the trigonal bipyramidal cation [Ni(P(n-Pr)3)2(CN-t-Bu)3]2+ (3) and the dinuclear NCS-bridged anion [Ni(1,3-micro-NCS)(NCS)3]2(2-) (4). In contrast, Pd(NCS)2(P(n-Pr)3)2 underwent substitution with 2 equiv. of CN-t-Bu to give the four-coordinate mono(isocyanide) Pd(II) complex Pd(NCS)(SCN)(CN-t-Bu)(P(n-Pr)3) (5) via phosphine dissociation. Reactions of M(NCS)2L2 (M = Pd, Pt; L = PMe3, PEt3, PMePh2, P(n-Pr)3) with two equiv. of CN-R (R = t-Bu, i-Pr, C6H3-2,6-Me2) gave the corresponding bis(isocyanide) complexes [M(CN-R)2(PR3)2](SCN)2 (7-13), except for Pd(NCS)2(PEt3)2 that reacted with CN-R' (R' = i-Pr, C6H3-2,6-Me2) and produced the mono(isocyanide) Pd(II) complexes [Pd(CN-R')(SCN)(PEt3)2](SCN) (14 and 15). Finally, treatment of M(NCS)2(PMe3)2 (M = Ni, Pd, Pt) with sterically bulky isocyanide CN-C6H3-2,6-i-Pr2 gave various products, (16-18) depending on the identity of the metal.     

Bis-phosphites and bis-phosphinites based on distally-functionalised calix[4]arenes: coordination chemistry and use in rhodium-catalysed, low-pressure olefin hydroformylation

Six calix[4]arenes each bearing two non-cyclic PR2 units attached at distal phenolic oxygen atoms, p-Bu t-calix[4]arene-25,27-(OPR2)2-26,28-(OR')2(R = OPh; R'= Prn, L1; R = OPh; R'= CH2CO2Et, L2; R= OPh; R'= CO2 cholesteryl, L3; R = Ph; R'= Prn, 4; R = Ph; R'= CH2CO2Et, L5; R = Ph; R'= CO2cholesteryl, L6) have been synthesized and their coordinative properties investigated. The diphosphites L1-L3, where the P centres are separated by 12 bonds, readily form chelate complexes provided the complexation reaction is achieved either by using a starting complex that possesses good leaving groups or by operating under high dilution in order to avoid oligomer formation. Thus, the cationic complexes [Rh(COD)L1]BF4 and [Rh(COD)L3]BF4 were both formed in high yield by reacting the appropriate diphosphite with either [Rh(COD)(THF)2]BF4 or [Rh(COD)2]BF4. At high dilution, reaction of L3 with the neutral complex [PdCl2(COD)] afforded the chelate complex [PdCl2L3] in 90% yield. The reaction of one equiv. of L1 with [Rh(acac)(CO)2] resulted in the formation of [Rh(acac)L1] without requiring high dilution conditions. When the latter reaction was carried out with 0.5 equiv. of L1, the bimetallic complex [{Rh(acac)(CO)}2(eta]1-P,eta1-P'-L1)] was formed instead. Reaction at high dilution of with the cyclometallated complex [Pd(o-C6H4CH2NMe2)(THF)2]BF4 gave the expected chelate complex [Pd(o-C6H4CH2NMe2)]BF4. The latter slowly converts in solution to an oligomer in which the ligand behaves as a (eta1-P,eta1-P') bridging ligand, thus leading to a less strained structure. All six ligands, when mixed with [Rh(acac)CO2], effectively catalyse the hydroformylation of octene and styrene. In the hydroformylation of octene, the linear aldehyde selectivities observed with L2 and L3 are significantly higher (linear : branched =ca. 10) than those obtained with the other 4 ligands of this study and also with respect to PPh3. Molecular modelling shows that the lower rim substituents of and form tighter pockets about the metal centre than do the other ligands and so sterically favour the formation of Rh(n-alkyl) intermediates over that of Rh(i-alkyl) ones. In styrene hydroformylation, all ligands result in the formation of unusually high amounts of the linear aldehyde, the b : l ratios being all close to 65 : 35. The highest activities were found when using an L/Rh ratio of 1/1.     

Gas-phase synthesis and reactivity of binuclear gold hydride cations, (R3PAu)2H+ (R = Me and Ph)

Electrospray ionization of a mixture of the two gold phosphine chlorides, R3PAuCl (R = Ph and Me), silver nitrate and the amino acid N,N-dimethylglycine (DMG) yields a range of gold containing cluster ions including: (R3P)Au(PR'3)+; (R3PAu)(R'3PAu)Cl+ and (R3PAu)(R'3PAu)(DMG-H)+ (where R = R' = Ph; R = R' = Me; R = Me and R' = Ph). Collision induced dissociation (CID) of the (R3PAu)(R'3PAu)(DMG-H)+ precursor ions yielded the hitherto unknown gold hydride dimers (R3PAu)(R'3PAu)H+. The gas-phase chemistry of these dimers was studied using ion-molecule reactions, collision induced dissociation, electronic excitation dissociation (EED) and DFT calculations on the (H3PAu)2H+ model system. A novel phosphine ligand migration was found to occur prior to fragmentation under CID conditions and this was supported by DFT calculations, which revealed a transition state with a bridging phosphine ligand.     

Synthesis of zirconium, hafnium, and tantalum complexes with sterically demanding hydrazide ligands

The bulky hydrazine t-BuN(H)NMe2 was synthesized via hydrazone and t-BuN(H)N(H)Me intermediates as the major component in a 90:5:5 mixture consisting of t-BuN(H)NMe2, t-BuN(Me)N(H)Me, and t-BuN(Me)NMe2. Reacting the mixture with n-BuLi followed by distillation and fractional crystallization led to the isolation of the ligand precursor LiN(t-Bu)NMe2. Lithium hydrazides, LiN(R)NMe2, were reacted with metal chlorides to afford the hydrazide complexes M(N(Et)NMe2)4 (M = Zr or Hf), MCl(N(R)NMe2)3 (M = Zr, R = i-Pr or t-Bu; M = Hf, R = t-Bu), and TaCl3(N(i-Pr)NMe2)2. The X-ray crystal structures of [LiN(i-Pr)NMe2]4, [LiN(t-Bu)NMe2.THF]2, ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu), and TaCl3(N(i-Pr)NMe2)2 were determined. The structural analyses revealed that the hydrazide ligands in ZrCl(N(R)NMe2)3 (R = i-Pr or t-Bu) and TaCl3(N(i-Pr)NMe2)2 are eta2 coordinated.     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Effect of trimethylsilyl substitution on the chemical properties of triarylphosphines and their corresponding metal-complexes: solubilising effect in supercritical carbon dioxide

The donor strengths of the following triarylphosphine ligands P(Ar)(2)(Ar')(Ar = Ar'= 4-Me(3)SiC(6)H(4), 1b; 4-Me(3)CC(6)H(4), 1d; 4-F(3)CC(6)H(4), 1e; Ar = C(6)H(5), Ar'= 4-Me(3)SiC(6)H(4), 1c) have been evaluated experimentally and theoretically. The measurements of the J(P-Se) coupling constants of the corresponding synthesised selenides Se=P(Ar)(2)(Ar'), 2b,c and the DFT calculation of the energies of the phosphine lone-pair (HOMO) reveal insignificant influence on the electronic properties of the substituted phosphines when the trimethylsilyl group is attached to the aryl ring, in marked contrast to the strong electronic effect of the trifluoromethyl group. These triarylphosphine ligands P(Ar)(2)(Ar') reacted with (eta5-C(5)H(5))Co(CO)(2), (eta5-C(5)H(5))Co(CO)I(2) or PdCl(2) to yield the new compounds (eta5-C(5)H(5))Co(CO)[P(Ar)(2)(Ar')], 3b,d; (eta5-C(5)H(5))CoI(2)[P(Ar)(2)(Ar')], 4b-e; and PdCl(2)[P(Ar)(2)(Ar')](2), 5b,c respectively. These complexes have been characterized and their spectroscopic properties compared with those reported for the known triphenylphosphine complexes. Again, the contrast of the (31)P NMR and (13)C NMR chemical shifts or C-O or M-Cl stretching frequencies, when applied, does not show an important electronic effect on the metal complex of the trimethylsilyl substituted phosphines with respect to P(C(6)H(5))(3) derivatives. Solubility measurements of complexes 3a and 3b in scCO(2) were performed. We conclude that Me(3)Si groups on the triarylphosphine improve the solubility of the corresponding metal complex in scCO(2).     

Synthesis and properties of gold alkene complexes. Crystal structure of [Au(bipy(oXyl))(eta(2)-CH(2)=CHPh)](PF(6)) and DFT calculations on the model cation [Au(bipy)(eta(2)-CH(2)=CH(2))](+)

Unprecedented 16-electron gold(i) olefin complexes of general formula [Au(bipy(R,R'))(eta(2)-olefin)](PF(6)) and [Au(2)(bipy(R,R'))(2)(mu-eta(2):eta(2)-diolefin)](PF(6))(2) (bipy(R,R') = 6-substituted-2,2'-bipyridine) have been prepared by reaction of dinuclear gold(III) oxo complexes [Au(2)(bipy(R,R'))(2)(mu-O)(2)](PF(6))(2) with the appropriate olefin. The X-ray crystal structures of two mononuclear complexes (olefin = styrene) show in-plane coordination of the olefin and a C[double bond, length as m-dash]C bond distance considerably lengthened with respect to the free olefin. The spectroscopic properties of the complexes are discussed and compared with those of analogous d(10) metal derivatives. Both structural and spectroscopic information indicate a substantial contribution of pi-back-donation to the Au-olefin bond in the three-coordinate species. Theoretical calculations carried out at the hybrid-DFT level on the model compound [Au(bipy)(eta(2)-CH(2)[double bond, length as m-dash]CH(2))](+) show excellent agreement with the experimental findings giving in addition an estimate of a pi-back-bonding contribution higher than that of the sigma-bonding.     

Activation and functionalization of white phosphorus at rhodium: experimental and computational analysis of the [(triphos)Rh (eta1:eta2-P4RR')]Y complexes (triphos=MeC(CH2PPh2)3; R=H, Alkyl, Aryl; R'=2 electrons, H, Me)

Thermal reaction of white phosphorus with [(triphos)RhH(3)] (1) in THF affords [(triphos)Rh(eta(1):eta(2)-P(4)H)] (2), triphos=MeC(CH(2)PPh(2))(3). Similar complexes [(triphos)Rh(eta(1):eta(2)-P(4)R)] (R=Me (7), Et (8), Ph (9)) also form at lower temperature by the reaction of P(4) and [(triphos)Rh(R)(eta(2)-C(2)H(4))] with elimination of ethene. In contrast, a double-insertion process follows the reaction of [(triphos)Rh(H)(eta(2)-C(2)H(4))] and P(4) to generate tetraphosphido ethyl complex 8. Compounds 2, 7, 8 and 9 are thermally unstable and eventually decompose into the cyclotriphosphorus complex [(triphos)Rh(eta(3)-P(3))] (3) plus other unidentified phosphorus-containing species. Otherwise, PH(3) or PH(2)R is generated in the presence of H(2). The formation of PH(3) and 3 is quantitative starting from the precursor 2. The electrophilic attack of MeOTf or HBF(4) on the P(4)R ligand in the complexes 2, 7-9 is regioselective, and yields a cationic product of formula [(triphos)Rh(eta(1):eta(2)-P(4)RR')](+). The direct attack on the substituted p-R phosphorus atom is demonstrated by crossing experiments. Complexes of the latter type have been isolated in the solid state for the combinations R=H and R'=Me (11) or R=Ph and R'=Me (12). The latter species, [(triphos)Rh(eta(1):eta(2)-P(4)PhMe')]OTf.2 CH(2)Cl(2) (OTf=triflate), has been characterised by X-ray methods. The geometry at the metal is better described as a trigonal bipyramidal than pseudo-octahedral. In fact, the P(4)RR' unit acts as a bidentate ligand with its exocyclic PR(2) donor group and the endocyclic, dihapto-coordinated Pdbond;P linkage. The latter group lies in the equatorial plane, in a similar way to a classic olefin ligand that is coordinated to a butterfly-shaped L(4)M fragment (M=d(8)). DFT calculations on a model of 2 and all possible protonated isomers confirm that double substitution at the exocyclic P-donor positions of the open P(4) unit is energetically favoured. A multinuclear and multidimensional NMR analysis confirms that this structure is maintained in solution for both the parent and the protonated compounds.