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1.
The syntheses and structures of two mixed‐ligand complexes of platinum(II) with deprotonated oxopurine bases and tri­phenyl­phosphine are reported, namely the theophyllinate complex cis‐bis(1,2,3,6‐tetra­hydro‐1,3‐di­methyl­purine‐2,6‐dionato‐κN7)­bis(tri­phenyl­phosphine‐κP)­platinum(II), [Pt(C7H7N4O2)2(C18H15P)2], (I), and the theobrominate complex cis‐chloro(1,2,3,6‐tetrahydro‐3,7‐dimethylpurine‐2,6‐dionato‐κN1)­bis(tri­phenyl­phosphine‐κP)­platinum(II) ethanol hemisolvate, [PtCl(C7H7N4O2)(C18H15P)2]·0.5C2H5OH, (II). In (I), the coordination geometry of Pt is square planar, formed by the two coordinating N atoms of the theophyl­linate anions in a cis arrangement and two P atoms from the tri­phenyl­phosphine groups. In (II), there are two crystallographically independent mol­ecules. They both exhibit a square‐planar coordination geometry around Pt involving one Cl atom, the coordinating N atom of the theobrominate anion and two P atoms from the tri­phenyl­phosphine groups. The two tri­phenyl­phosphine groups are arranged in a cis configuration in both structures. The heterocyclic rings are rotated with respect to the coordination plane of the metal by 82.99 (8) and 88.09 (8)° in complex (I), and by 85.91 (16) and 88.14 (18)° in complex (II). Both structures are stabilized by intramolecular stacking interactions involving the purine rings and the phenyl rings of adjacent tri­phenyl­phosphine moieties.  相似文献   

2.
Substituted decarbonylation reaction of ruthenium 1,2‐naphthoquinone‐1‐oxime (1‐nqo) complex, cis‐, cis‐[Ru| ζ2‐N(O)C10‐H6O|2(CO)2] (1), with acetonitrile gave cis, cis‐[Ru | ζ2‐ N(O)C10H6O|2(CO)(NCMe)] (2). Complex 2 was fully characterized by 1H NMR, FAB MS, IR spectra and single crystal X‐ray analysis. Complex 2 maintains the coordination structure of 1 with the two naphthoquinonic oxygen atoms, as well as the two oximato nitrogen atoms located cis to each other, showing that there is no ligand rearrangement of the 1‐nqo ligands during the substitution reaction. The carbonyl group originally trans to the naphthoquinonic oxygen in one 1‐nqo ligand is left in its original position [O(5)‐Ru‐C(1), 174.0(6)°], while the other one originally trans to the oximato group of the other 1‐nqo ligand is substituted by NCMe [N(1)‐Ru‐N(3), 170.6(6)°]. This shows that the carbonyl trans to oximato group is more labile than the one trans to naphthoquinonic O atom towards substitution. This is probably due to the comparatively stronger ± back bonding from ruthenium metal to the carbonyl group trans to naphthoquinonic O atom, than the one trans to oximato group, resulting in the comparatively weaker Ru–‐CO bond for the latter and consequently easier replacement of this carbonyl. Selected coupling of phenylacetylene mediated by 2 gave a single trans‐dimerization product 3, while 2 mediated coupling reaction of methyl propiolate produced three products: one trans‐dimerization product 4 and two cyclotrimeric products 5 and 6.  相似文献   

3.
The reaction of the di‐lithiated oxamide of 1 with two equivalents of SnCl2 provided the tin trans‐oxamide 3 . In solution, spectroscopic analysis suggests exclusively the formation of a trans‐oxamide (trans‐ 3 ). However, the solid state shows an atypical cis‐oxamide (cis‐ 3 ), where the oxamide fragment acts as an anti‐Janus head ligand. An 119Sn‐NMR variable temperature experiment ([D8]THF) of the trans‐oxamide (trans‐ 3 ) was performed however, at lower temperature no additional signal was observed, which confirmed the absence of a dynamic equilibrium. Dispersion‐corrected density functional calculations revealed that the cis conformation of this tin(II) oxamide complex is more stable than the trans isomer by 1.4 kcal · mol–1.  相似文献   

4.
Both trans and cis isomers of azobenzene‐linked bis‐terpyridine ligand L1 were incorporated in rigid macrocycles linked by FeII(tpy)2 (tpy: terpyridine) units. The complex of the longer trans‐ L1 is dinuclear [(trans‐ L1 )2 ? FeII2], whereas the complex of the shorter cis‐ L1 is mononuclear [cis‐ L1? FeII]. The complex cis‐ L1? FeII was not only thermally stable but also photochemically inactive. These results indicate a perfectly locked state of cis‐azobenzene. The stable macrocyclic structure of cis‐ L1? FeII causes locking of the isomerization. To the best of our knowledge, this is first example of dual locking of photo‐ and thermal isomerization of cis‐azobenzene.  相似文献   

5.
Derivatives of the Hoveyda–Grubbs complex bearing S‐, Br‐, I‐, and N‐coordinating naphthalene ligands were synthesized and characterized with NMR and X‐ray studies. Depending on the arrangement of the coordinating sites on the naphthalene core, the isomeric catalysts differ in activity in model metathesis reactions. In particular, complexes with the Ru?CH bond adjacent to the second aromatic ring of the ligand suffer from difficulties experienced on their preparation and initiation. The behavior most probably derives from steric hindrance around the double bond and repulsive intraligand interactions, which result in abnormal chemical shifts of benzylidene protons observed with 1H NMR. Furthermore EXSY studies revealed that the halogen‐chelated ruthenium complexes display an equilibrium, in which major cis‐Cl2 structures are accompanied with small amounts of isomeric forms. In general, contents of the minor forms, measured at 80 °C, correlate with the observed activity trends of the catalysts, although some exceptions complicate the mechanistic picture. We assume that for the family of halogen‐chelated metathesis catalysts the initiation mechanism starts with the cis‐Cl2?trans‐Cl2 isomerization, although further steps may become rate‐limiting for selected systems.  相似文献   

6.
In the cation of the title complex, cis,cis,cis‐[Ru(η2‐O2CMe)(dppe)2]PF6·2MeOH [dppe is 1,2‐bis­(di­phenyl­phosphino)­ethane, C26H24P2], the Ru atom is in a pseudo‐octahedral coordination environment with two chelating dppe ligands and one chelating acetate ligand. Intra‐phosphine and intra‐acetate bond lengths and angles are unexceptional. Deviations from idealized octahedral coordination angles at ruthenium [O—Ru—O 59.43 (8)° and P—Ru—P 103.19 (2)°] presumably derive from constraints imposed by the chelate rings. The Ru—P distances for the mutually trans P‐donor atoms [2.3785 (6) Å] are significantly longer than those for the Ru—P linkages trans to the acetate ligand [2.3074 (6) Å]. The Ru1, C1 and C2 atoms lie on a twofold axis, and atom P3 of the anion lies on an inversion centre.  相似文献   

7.
The reactivity difference between the hydrogenation of CO2 catalyzed by various ruthenium bidentate phosphine complexes was explored by DFT. In addition to the ligand dmpe (Me2PCH2CH2PMe2), which was studied experimentally previously, a more bulky diphosphine ligand, dmpp (Me2PCH2CH2CH2PMe2), together with a more electron‐withdrawing diphosphine ligand, PNMeP (Me2PCH2NMeCH2PMe2), have been studied theoretically to analyze the steric and electronic effects on these catalyzed reactions. Results show that all of the most favorable pathways for the hydrogenation of CO2 catalyzed by bidentate phosphine ruthenium dihydride complexes undergo three major steps: cistrans isomerization of ruthenium dihydride complex, CO2 insertion into the Ru?H bond, and H2 insertion into the ruthenium formate ion. Of these steps, CO2 insertion into the Ru?H bond has the lowest barrier compared with the other two steps in each preferred pathway. For the hydrogenation of CO2 catalyzed by ruthenium complexes of dmpe and dmpp, cistrans isomerization of ruthenium dihydride complex has a similar barrier to that of H2 insertion into the ruthenium formate ion. However, in the reaction catalyzed by the PNMePRu complex, cistrans isomerization of the ruthenium dihydride complex has a lower barrier than H2 insertion into the ruthenium formate ion. These results suggest that the steric effect caused by the change of the outer sphere of the diphosphine ligand on the reaction is not clear, although the electronic effect is significant to cistrans isomerization and H2 insertion. This finding refreshes understanding of the mechanism and provides necessary insights for ligand design in transition‐metal‐catalyzed CO2 transformation.  相似文献   

8.
Uranium(IV)–carbene–imido complexes [U(BIPMTMS)(NCPh3)(κ2N,N′‐BIPY)] ( 2 ; BIPMTMS=C(PPh2NSiMe3)2; BIPY=2,2‐bipyridine) and [U(BIPMTMS)(NCPh3)(DMAP)2] ( 3 ; DMAP=4‐dimethylamino‐pyridine) that contain unprecedented, discrete R2C=U=NR′ units are reported. These complexes complete the family of E=U=E (E=CR2, NR, O) metalla‐allenes with feasible first‐row hetero‐element combinations. Intriguingly, 2 and 3 contain cis‐ and trans‐C=U=N units, respectively, representing rare examples of controllable cis/trans isomerisation in f‐block chemistry. This work reveals a clear‐cut example of the trans influence in a mid‐valent uranium system, and thus a strong preference for the cis isomer, which is computed in a co‐ligand‐free truncated model—to isolate the electronic trans influence from steric contributions—to be more stable than the trans isomer by approximately 12 kJ mol?1 with an isomerisation barrier of approximately 14 kJ mol?1.  相似文献   

9.
The title compound, [Mn(NCS)2(C18H12N6)2(CH4O)2], con­tains a centrosymmetric octahedral MnII centre and three pairs of trans‐coordinating ligands. It is the first example of a mononuclear metal complex with the 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine (tpt) ligand. Intermolecular π–π stacking of the planar tpt ligands, as well as hydrogen bonds between pyridyl N and methanol H atoms, results in the formation of a three‐dimensional network.  相似文献   

10.
The title compound, [Cu(C9H8BrClNO2)2], is a square‐planar complex. The potentially tridentate dibasic 2‐bromo‐4‐chloro‐6‐{[(2‐hydroxyethyl)imino]methyl}phenolate ligand coordinates in a trans‐bis fashion to the CuII centre via the imine N and phenolate O atoms. The CuII atom lies on the centre of inversion of the molecule. The potentially coordinating hydroxyethyl group remains protonated and uncoordinated, taking part in intermolecular hydrogen bonds with vicinal groups, leading to the formation of a two‐dimensional hydrogen‐bond network with sheets parallel to the (10) plane. Substituent effects on the crystal packing and coordination modes of the ligand are discussed.  相似文献   

11.
A series of new N‐aryl‐α,β‐disubstituted amides (gem or E1; trans or E2) were synthesized in good yields by carbonylative addition of aniline derivatives 1a–f to aromatic alkynes 2a,b catalyzed by Pd(OAc)2 and 1,3‐bis(diphenylphosphino)propane. The catalytic synthesis of tertiary α,β‐unsaturated amides was also successfully achieved. Traces of products were observed in the absence of p‐toluenesulfonic acid used as an additive. The reaction is sensitive to the type of phosphine ligand and solvent. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

12.
The platina‐β‐diketone [Pt2{(COMe)2H}2(µ‐Cl)2] ( 1 ) was found to react with monodentate phosphines to yield acetyl(chloro)platinum(II) complexes trans‐[Pt(COMe)Cl(PR3)2] (PR3 = PPh3, 2a ; P(4‐FC6H4)3, 2b ; PMePh2, 2c ; PMe2Ph, 2d ; P(n‐Bu)3, 2e ; P(o‐tol)3, 2f ; P(m‐tol)3, 2g ; P(p‐tol)3, 2h ). In the reaction with P(o‐tol)3 the methyl(carbonyl)platinum(II) complex [Pt(Me)Cl(CO){P(o‐tol)3}] ( 3a ) was found to be an intermediate. On the other hand, treating 1 with P(C6F5)3 led to the formation of [Pt(Me)Cl(CO){P(C6F5)3}] ( 3b ), even in excess of the phosphine. Phosphine ligands with a lower donor capability in complexes 2 and the arsine ligand in trans‐[Pt(COMe)Cl(AsPh3)2] ( 2i ) proved to be subject to substitution by stronger donating phosphine ligands, thus forming complexes trans‐[Pt(COMe)Cl(L)L′] (L/L′ = AsPh3/PPh3, 4a ; PPh3/P(n‐Bu)3, 4b ) and cis‐[Pt(COMe)Cl(dppe)] ( 4c ). Furthermore, in boiling benzene, complexes 2a – 2c and 2i underwent decarbonylation yielding quantitatively methyl(chloro)platinum(II) complexes trans‐[Pt(Me)Cl(L)2] (L = PPh3, 5a ; P(4‐FC6H4)3, 5b ; PMePh2, 5c ; AsPh3, 5d ). The identities of all complexes were confirmed by 1H, 13C and 31P NMR spectroscopy. Single‐crystal X‐ray diffraction analyses of 2a ·2CHCl3, 2f and 5b showed that the platinum atom is square‐planar coordinated by two phosphine ligands (PPh3, 2a ; P(o‐tol)3, 2f ; P(4F‐C6H4)3, 5b ) in mutual trans position as well as by an acetyl ligand ( 2a, 2f ) and a methyl ligand ( 5b ), respectively, trans to a chloro ligand. Single‐crystal X‐ray diffraction analysis of 3b exhibited a square‐planar platinum complex with the two π‐acceptor ligands CO and P(C6F5)3 in mutual cis position (configuration index: SP‐4‐3). Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

13.
Experimental studies of Hoveyda–Grubbs metathesis catalysts reveal important consequences of substitution at the 6‐position of the chelating benzylidene ligand. The structural modification varies conformational preferences of the ligand that affects its exchange due to the interaction of the coordinating site with the ruthenium center. As a consequence, when typical S‐chelated systems are formed as kinetic trans‐Cl2 products, for 6‐substituted benzylidenes the preference is altered toward direct formation of thermodynamic cis‐Cl2 isomers. Activity data and reactions with tricyclohexylphosphine (PCy3) support also a similar scenario for O‐chelated complexes, which display fast trans‐Cl2?cis‐Cl2 equilibrium observed by NMR EXSY studies. The presented conformational model reveals that catalysts, which cannot adopt the optimal nonchelating conformation of benzylidene ligand, initiate through a high‐energy associative mechanism.  相似文献   

14.
The synthesis and crystal structure (at 100 K) of the title compound, Cs[Fe(C11H13N3O2S2)2]·CH3OH, is reported. The asymmetric unit consists of an octahedral [FeIII(L)2] fragment, where L2− is 3‐ethoxysalicylaldehyde 4‐methylthiosemicarbazonate(2−) {systematic name: [2‐(3‐ethoxy‐2‐oxidobenzylidene)hydrazin‐1‐ylidene](methylamino)methanethiolate}, a caesium cation and a methanol solvent molecule. Each L2− ligand binds through the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an FeIIIS2N2O2 chromophore. The O,N,S‐coordinating ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions and the N atoms in trans positions. The FeIII cation is in the low‐spin state at 100 K.  相似文献   

15.
The cationic gold phosphine complex [{PCy2(o‐biphenyl)}Au(NCMe)]+SbF6? (Cy=cyclohexyl) catalyzes the intermolecular, anti‐Markovnikov hydroamination reaction of monosubstituted and cis‐ and trans‐disubstituted alkylidenecyclopropanes (ACPs) with imidazolidin‐2‐ones and other nucleophiles. This reaction forms 1‐cyclopropyl alkylamine derivatives in high yield and with high regio‐ and diastereoselectivity. NMR spectroscopic analysis of gold π‐ACP complexes and control experiments point to the sp hybridization of the ACP internal alkene carbon atom as controlling the regiochemistry of the ACP hydroamination reaction.  相似文献   

16.
The ability of the tetraaza‐dithiophenolate ligand H2L2 (H2L2 = N,N′‐Bis‐[2‐thio‐3‐aminomethyl‐5‐tert‐butyl‐benzyl]propane‐1,3‐diamine) to form dinuclear chromium(III) complexes has been examined. Reaction of CrIICl2 with H2L2 in methanol in the presence of base followed by air‐oxidation afforded cis,cis‐[(L2)CrIII2(μ‐OH)(Cl)2]+ ( 1a ) and trans,trans‐[(L2)CrIII2(μ‐OH)(Cl)2]+ ( 1b ). Both compounds contain a confacial bioctahedral N2ClCrIII(μ‐SR)2(μ‐OH)CrIIIClN2 core. The isomers differ in the mutual orientation of the coligands and the conformation of the supporting ligand. In 1a both Cl? ligands are cis to the bridging OH function. In 1b they are in trans‐positions. Reaction of the hydroxo‐bridged complexes with HCl yielded the chloro‐bridged cations cis,cis‐[(L2)CrIII2(μ‐Cl)(Cl)2]+ ( 2a ) and trans,trans‐[(L2)CrIII2(μ‐Cl)(Cl)2]Cl ( 2b ), respectively. These bridge substitutions proceed with retention of the structures of the parent complexes 1a and 1b .  相似文献   

17.
The synthesis and molecular structure of trans‐{bis[(acetato‐κO)‐(2‐(1‐aziridinyl)ethanol‐κ2N,O)]}cobalt(II) ( 4 ) and cis‐{bis[chlorido‐(2‐(1‐aziridinyl)ethanol‐κ2N,O)]}cobalt(II) ( 5 ) is reported. Both neutral chelate complexes are prepared from the corresponding CoII salt [CoX2; X = OAc ( 1 ), Cl ( 2 )] and 2‐(1‐aziridinyl)ethanol (azolH, 3 ) in dry dichloromethane. A third, ionic complex, cis‐{bis[aqua‐(2‐(1‐aziridinyl)ethanol‐κ2N,O)]}cobalt(II) diacetate ( 6 ) is formed from 4 in the presence of water and could be crystallized from aqueous dichloromethane. In all cases, 2‐(1‐aziridinyl)ethanol is coordinating as bidentate chelate ligand by the nitrogen and oxygen atom of the aziridinyl and hydroxy moiety. After purification, the compounds have been fully characterized using IR spectroscopy and FAB+‐MS. The single‐crystal X‐ray structure analysis revealed a distorted octahedral geometry for all complexes with either trans ( 4 ) or cis ( 5 , 6 ) configuration.  相似文献   

18.
In the title complex, [RuCl2(C7H7NO)(C2H6OS)2], the metal ion is at the centre of a distorted octahedral NOCl2S2 coordination sphere. The neutral 2‐acetyl­pyridine ligand binds to the metal ion through the pyridine N and carbonyl O atoms, forming a five‐membered chelate ring. The monodentate S‐coordinating di­methyl sulfoxide mol­ecules are mutually cis, and the two remaining positions in the coordination sphere are occupied by two mutually trans Cl? ions.  相似文献   

19.
The crystal structures are reported of trans‐dioxocyclam dihydrate, C10H20N4O2·2H2O, a structural isomer of the well known cis‐dioxocyclam, and of its novel Ni complex, (1,4,8,11‐tetra­aza­cyclo­tetra­decane‐2,9‐dionato‐κ4N)­nickel(II) dihydrate, [Ni(C10H18N4O2)]·2H2O, the first example of a trans­ition metal complex of this ligand. Both mol­ecules lie on crystallographic centres of inversion. The free ligand has two of its N atoms turned outwards from the ring and hydrogen bonded to water mol­ecules. A major conformational change takes place in the complex in which the ligand binds in a trans tetradentate fashion, as suggested by the electronic spectrum. The nickel(II) ion is low spin, although the electronic spectrum of the complex in water indicates an equilibrium mixture of low‐spin and high‐spin species. The irreversible electrochemical oxidation of [NiL1] (L1 is deprotonated trans‐dioxocyclam, C10H18N4O2) in water occurs at a potential of 0.964 V [versus SHE (standard hydrogen electrode)], which is very similar to that for the Ni–cis‐dioxocyclam complex.  相似文献   

20.
The reaction of 4,4′‐bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl (btmb) with silver(I) salts of BF4, NO3 and N3 led to the formation of four new silver(I) coordination polymers {[Ag(btmb)]BF4}n ( 1 ), {[Ag2(btmb)3](NO3)2(H2O)5}n ( 2 ), [Ag2(btmb)(N3)2]n ( 3 ), and [Ag(btmb)(N3)]n ( 4 ). Their coordination number varies from 2 (in 1 ) to 3 (in 2 ), 4 (in 3 ), and 5 (in 4 ). Different from the single chain structure of 1 , complex 2 displays a 1D ladder‐like double chain framework, whereas complex 3 exhibits a 2D layered architecture. Complex 4 has the same anion as complex 3 but shows a different metal‐to‐ligand ratio and a 1D double‐zigzag chain structure. Both 3 and 4 have Ag ··· Ag argentophilic interactions. The ligand btmb adopts both cis or trans configuration in the studied complexes. A trans‐ or cis‐btmb ligand link silver ions with Ag ··· Ag distances of ≈?18 and 13 Å, respectively. BF4 and NO3 are non‐coordinating anions in 1 and 2 . N3 is the bridging anion in 3 (1,3‐bridging fashion) and 4 (1,1‐bridging fashion). These findings suggest that the coordination numbers around the AgI ion correlate to the coordination abilities of anions and the btmb to silver ratio. In addition, the influence of anions on thermal stability were also investigated. This work is a good example that nicely supports the less explored field of anion‐dependent structures of complexes with non‐pyridyl ligands.  相似文献   

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