Bulky Amido Ligands in Rare Earth Chemistry — Syntheses,Structures, and Catalysis

The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe₃)₂}₃], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article.     

Synthesis,Structures, and Properties of a Series of New Coordination Polymers Built from 2‐Ethyl‐1H‐imidazole‐4,5‐dicarboxylate Ligand

A series of new coordination polymers, namely, [Sr(H₂EIDC)₂(H₂O)₂]_n ( 1 ),{[Pb(H₂EIDC)₂(H₂O)](H₂O)₃}_n ( 2 ), [Ag(H₂EIDC)]_n ( 3 ), and [Ba(H₂EIDC)₂(H₂O)]_n ( 4 ) (H₂EIDC = 2‐ethyl‐1H‐imidazole‐4,5‐dicarboxylate), were synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, X‐ray diffraction and thermogravimetric analyses. Complex 1 is a 2D infinite gridlike (4,4)topological layer structure. Complex 2 is a 2D corrugated layer constructed by Pb^II atoms and H₂EIDC^– anions. Complex 3 is a 2D corrugated sheet consisting of 1D chains linked by short Ag ··· Ag interactions, and the three complexes are extended into 3D supramolecular structures by weak intermolecular forces such as hydrogen bonds and π–π stacking interactions. Complex 4 exhibits a 3D framework with 1D channels. Furthermore, the luminescent properties of complexes 1 , 2 , and 3 are also investigated.     

Syntheses,Structures, and Properties of Two Coordination Compounds of Pb(II) and Cd(II) with Quinoline‐8‐oxy‐acetate Acid

Quinoline‐8‐oxy‐acetate acid (8‐qoacH) reacts with M(II) (M=Pb and Cd) to give rise to two coordination complexes [Pb(8‐qoac)₂] ( 1 ) and [Cd(8‐qoac)(bdc)_0.5(H₂O)₂] ( 2 ) under hydrothermal conditions. They are characterized by single‐crystal X‐ray diffraction, IR, elemental, thermal analyses and luminescent analysis. The Pb metal centers connect the 8‐qoac anions to form a 1D linear chain in 1 . In 2 , two symmetrical [Cd(8‐qoac)(H₂O)₂] are bridged by a 1,4‐bdc^2? to generate a coordination unit [Cd(8‐qoac)(bdc)_0.5(H₂O)₂], and all the units are further connected to a 2D supramolecular layer‐like structure via hydrogen bonds. TG analyses indicate that 1 exhibits higher thermostability than 2 . Fluorescence spectrum of compound 2 in solid state shows strong fluorescence property.     

One‐dimensional Salen‐type Chain‐like Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Fluorescence Properties

Four salen‐type lanthanide(III) coordination polymers [LnH₂L(NO₃)₃(MeOH)_x]_n [Ln = La ( 1 ), Ce ( 2 ), Sm ( 3 ), Gd ( 4 )] were prepared by reaction of Ln(NO₃)₃ · 6H₂O with H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine]. Single‐crystal X‐ray diffraction analysis revealed that H₂L effectively functions as a bridging ligand forming a series of 1D chain‐like polymers. The solid‐state fluorescence spectra of polymers 1 and 2 emit single ligand‐centered green fluorescence, whereas 3 exhibits typical red fluorescence of Sm^III ions. The lowest triplet level of ligand H₂L was calculated on the basis of the phosphorescence spectrum of Gd^III complex 4 . The energy transfer mechanisms in the lanthanide polymers were described and discussed.     

Solvent‐Free Syntheses of Hierarchically Porous Aluminophosphate‐Based Zeolites with AEL and AFI Structures

Development of sustainable routes for synthesizing aluminophosphate‐based zeolites are very important because of their wide applications. As a typical sustainable route, solvent‐free synthesis of zeolites not only decreases polluted wastes but also increases product yields. Systematic solvent‐free syntheses of hierarchically porous aluminophosphate‐based zeolites with AEL and AFI structures is presented. XRD patterns and SEM images show that these samples have high crystallinity. N₂ sorption isotherm tests show that these samples are hierarchically porous, and their surface areas are comparable with those of corresponding zeolites from hydrothermal route. Chosen as an example, catalytic oxidation of ethylbenzene with O₂ shows that cobalt substituted APO‐11 from the solvent‐free route (S‐CoAPO‐11) is more active than conventional CoAPO‐11 from hydrothermal route owing to the sample hierarchical porosity.     

N,N′‐Bis(Salicylidene)‐1,2‐Cyclohexanediamine Lanthanide(III) Coordination Polymers: Syntheses,Crystal Structures,and Luminescence Properties

The salen‐type ligand H₂L [H₂L = N,N′‐bis(salicylidene)‐1,2‐cyclohexanediamine] was utilized for the synthesis of two lanthanide(III) coordination polymers [LnH₂L(NO₃)₃MeOH]_n [Ln = Eu ( 1 ) and Ln = Lu ( 2 )]. The single‐crystal X‐ray diffraction analyses of 1 and 2 revealed that they are isomorphous and exhibit one‐dimension neutral structure, in which H₂L effectively functions as a bridging ligand and give rise to a chain‐like polymer. The luminescent properties of polymers in solid state and in solution were investigated and 1 exhibits typical red luminescence of Eu^III ions in solid state and dichloromethane solution and 2 emits the ligand‐centered blue luminescence. The energy transfer mechanisms in these luminescent lanthanide polymers were described through calculation of the lowest triplet level of ligand H₂L.     

Supramolecular Structures with the 2‐Propyl‐4,5‐dicarboxy‐1H‐imidazole Ligand: Hydrothermal Synthesis,Structures, and Photoluminescence

Self‐assembly of the rigid organic ligand 2‐propyl‐4,5‐dicarboxy‐1H‐imidazole ( L ) with different metal ions (Zn²⁺, Ni²⁺, Cu²⁺, Cd²⁺) led to four new complexes, namely, [M( L )(phen)] [M = Zn ( 1 ); Ni ( 2 ); Cd ( 3 )] and [Cu( L )( 4 )] (phen = 1,10‐phenanthroline). Their structures were determined by single‐crystal X‐ray diffraction analyses, and they were further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Whereas compounds 1 , 2 , and 3 are discrete units, hydrogen‐bonding interactions play a vital role in these complexes. Compounds 1 and 2 form one‐dimensional (1D) and two‐dimensional (2D) structures through hydrogen‐bondinginteractions with helical character. In 1 , the hydrogen bonds (O–H ··· O) alternately bridge the M^II cations of the discrete units to form a one‐dimensional (1D) infinite helical chain. Complex 2 forms a 2D helical layer through parallel hydrogen bonds (N/O–H ··· O/N) between two adjacent helical chains. In 3 , the hydrogen bonds (N–H ··· O) connect adjacent discrete units into a ten‐membered ring with extension into a one‐dimensional double‐chain supramolecular structure. Complex 4 is a two‐dimensional gridlike (4,4) topological layer which is extended to a 3D network by hydrogen bonding. The solid‐state fluorescence spectrum of complex 3 was determined.     

A Zwitterionic Phosphonio‐1, 2, 4‐Diazaphospholide and Neutral 1, 2, 4‐Diazaphosphole — A Comparative Study of Molecular Structures and Co‐ordination Properties

The bis‐phosphonio‐1, 2, 4‐diazaphospholide salt ( 1 [Cl]) reacts with complex boron hydrides under selective extrusion of one PPh₃ moiety to give borane adducts of a novel zwitterionic phosphonio‐1, 2, 4‐diazaphospholide. Both the Et₃B adduct 2b and the free zwitterionic heterocycle 3 , which was liberated by further reaction of 2b with NEt₃, were characterized by spectroscopic data and 2b , as well, by a single crystal X‐ray diffraction study. The comparison of the structural data with those of a neutral 1, 2, 4‐diazaphosphole and a lithium‐1, 2, 4‐diazaphospholide which was formed by deprotonation of the parent 1, 2, 4‐diazaphosphole 4a discloses trends in endocyclic bonding distances which can be rationalized in terms of a charge dependent shift in the π‐electron distribution. First studies of the co‐ordination properties reveal for both 2b and 4a a marked preference to bind two M(CO)₅‐fragments (M = Cr, W) via the lone‐pairs of the phosphorus and one nitrogen atom; mononuclear complexes with P‐co‐ordinated heterocycles are formed as intermediates. A single crystal X‐ray diffraction study of the dinuclear complex [Cr₂(CO)₁₀(μ₂‐C₂H₃N₂P‐κP, κN)] ( 10a ) together with spectroscopic studies (including ¹⁸³W NMR studies of tungsten complexes) suggests that M→L back donation is more efficient for P‐ than for N‐bound metal fragments. No evidence for π‐co‐ordination of the 1, 2, 4‐diazaphosphole ring to a Cr(CO)₃ fragment was obtained.     

meso‐Free Corroles: Syntheses,Structures, Properties,and Chemical Reactivities

5,10‐Bis(pentafluorophenyl)corrole ( 5 ) and 5,15‐bis(pentafluorophenyl)corrole ( 9 ) have been synthesized as meso‐free corroles by rational synthetic routes. Both the structures of these corroles have been unambiguously revealed by X‐ray diffraction analysis and their optical and electrochemical properties have been studied. Chlorination and oxidative dimerization of 5 and 9 have been explored, which revealed a marked different reactivity of the free meso‐positions in 5 and 9 . 10‐Chlorinated corrole 11 was effectively prepared by the reaction of 9 with Palau‘chlor in the presence of 1 % pyridine whereas 5‐chlorinated corrole 12 was obtained in a trace amount from similar chlorination of 5 . 5,5′‐Linked corrole dimer 13 was produced by reaction of 5 with AgNO₂ in a good yield, whereas 10,10′‐linked corrole dimer 14 was formed in a moderate yield by the reaction of 9 with [bis(trifluoroacetoxy)iodo]benzene. Observed large electronic interaction between the two corroles in 13 as compared with that in 14 has been ascribed mainly to conformational flexibility of the former, which allows more coplanar conformation.     

Synthesis,Structures, and Reactivities of Pincer‐Type Ruthenium Complexes Bearing Two Proton‐Responsive Pyrazole Arms

A new metal–ligand bifunctional, pincer‐type ruthenium complex [RuCl( L1‐H2 )(PPh₃)₂]Cl ( 1 ; L1‐H2 =2,6‐bis(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)pyridine) featuring two proton‐delivering pyrazole arms has been synthesized. Complex 1 , derived from [RuCl₂(PPh₃)₃] with L1‐H2 , underwent reversible deprotonation with potassium carbonate to afford the pyrazolato–pyrazole complex [RuCl(L1‐H)(PPh₃)₂] ( 2 ). Further deprotonation of 1 and 2 with potassium hexamethyldisilazide in methanol resulted in the formation of the bis(pyrazolato) complex [Ru(L1)(MeOH)(PPh₃)₂] ( 3 ). Complex 3 smoothly reacted with dioxygen and dinitrogen to give the side‐on peroxo complex [Ru(L1)(O₂)(PPh₃)₂] ( 4 ) and end‐on dinitrogen complex [Ru(L1)(N₂)(PPh₃)₂] ( 5 ), respectively. On the other hand, the reaction of [RuCl₂(PPh₃)₃] with less hindered 2,6‐di(1H‐pyrazol‐3‐yl)pyridine ( L3‐H2 ) led to the formation of the dinuclear complex [{RuCl₂(PPh₃)₂}₂(μ₂‐ L3‐H2 )₂] ( 6 ), in which the pyrazole‐based ligand adopted a tautomeric form different from L1‐H2 in 1 and the central pyridine remained uncoordinated. The detailed structures of 1 , 2 , 3 , 3.MeOH , 4 , 5 , 6 were determined by X‐ray crystallography.     

Screening of N,N‐bidentate and N,N,N‐tridentate pyridine‐based ligands in the catalytic allylic oxidation of cyclic olefins

A variety of chiral N,N‐bidentate and N,N,N‐tridentate ligands based on the pyridine framework, namely C2‐symmetric dipyridylmethane and terpyridine, N‐(p‐toluensulfinyl)iminopyridines and two kinds of iminopyridines, has been assessed in the asymmetric copper(I)‐catalysed allylic oxidation of cyclic olefins. Catalytic activity and enantioselectivity were found to be highly dependent upon the framework of the ligands, which afforded cycloalkenyl benzoates in low to moderate yields and enantioselectivities. The best yields (up to 70%) and enantioselectivities (up to 53% enantiomeric excess) were obtained with an iminopyridine based on camphane and quinoline skeletons. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,Structures, and Fluorescent Properties of Three Cobalt‐Based Coordination Polymers with a Rigid Tripodal Carboxylate Ligand

Three cobalt(II) coordination polymers, [Co₂(tatb)₂(2,2′‐bipy)₂ (H₂O)₂ · DMA · 2H₂O] ( 1 ), [Co₂(tatb)₂(1,10‐phen)₂(H₂O)₂ · 2H₂O] ( 2 ) and [Co(tatb)(1,3‐dpp) · H₂O] ( 3 ) (H₃tatb = 4,4′,4′′‐(1,3,5‐triazine‐2,4,6‐triyl)tribenzoic acid; 2,2′‐bipy = 2,2′‐bipyridyl; 1,10‐phen = 1,10‐phenanthroline; 1,3‐dpp = 1,3‐bis(pyridin‐4‐yl)propane), were synthesized solvothermally and characterized by single‐crystal and powder X‐ray diffraction (PXRD), as well as IR spectroscopy. Complexes 1 and 2 exhibit 1D double‐chain structures, which further connect into interesting 3D networks by hydrogen bond and strong π–π interactions. Complex 3 possesses 2D 4⁴‐sql topology, which is packed parallel in an AA fashion. Moreover, thermal stability properties and photoluminescence properties of 1 , 2 and 3 were also investigated.     

Syntheses and Structures of Organotin(IV) Thioesters of N‐Phthaloylamino Acids

Five organotin(IV) thioesters of N‐phthaloyl amino acids with the general formulae R₃SnL (R = Me, Ph) and nBu₂SnL₂ were synthesized with L = N‐phthaloyl‐thioalanine and N‐phthaloyl‐thioleucine. The structures of trimethyltin(IV) N‐phthaloyl‐thioleucinate ( 1 ), trimethyltin(IV) N‐phthaloyl‐thioalaninate ( 2 ), triphenyltin(IV) N‐phthaloyl‐thioleucinate ( 3 ), triphenyltin(IV) N‐phthaloyl‐thioalaninate ( 4 ), and di‐n‐butyltin(IV) di‐N‐phthaloyl‐thioalaninate ( 5 ) were characterized by means of X‐ray diffractometry. Quantumchemical investigations served to clarify several structural peculiarities of the isolated compounds.     

从Baylis-Hillman溴化物方便的合成N-取代的咪唑和苯并三氮唑

在室温下, 通过Baylis-Hillman溴化物与咪唑或苯并三氮唑反应, 方便的合成了N-取代的咪唑和苯并三氮唑衍生物. 该方法的优点为操作简单, 反应条件温和, 产率高, 好的区域和立体选择性.     

Syntheses,Structures, and Magnetism of Trinuclear Zn2Ln Complexes with 2,6‐Dipicolinoylbis(N,N‐diethylthiourea)

The bifunctional ligand 2,6‐dipicolinoylbis(N,N‐diethylthiourea) (H₂L) readily reacts with mixtures of Zn(CH₃COO)₂ and LnCl₃ in MeOH at ambient temperature with formation of trinuclear heterobimetallic complexes [Zn₂Ln(L)₂(OAc)₃] ( 1a – 1f ) (Ln = Ce, Nd, Sm, Gd, Dy, Er). The X‐ray single‐crystal diffraction and structural studies of the complexes revealed their isostructural nature, in which two doubly‐charged ligands {L^2–} bind two Zn²⁺ ions with the terminal acylthiourea sites and one Ln³⁺ ion with the central 2,6‐pyridinedicarboxamide site. In the complexes, the coordination numbers of Ln^III and Zn^II ions are 9 and 5, respectively. Magnetic properties of the complexes were studied by temperature‐dependent dc magnetic measurements. The observed μ_eff values at room temperature are all closed to the calculated values. Fitting χ_M and M data of [Zn₂Gd(L)₂(OAc)₃] ( 1d ) shows a g_iso value of 1.94.     

Synthesis,Structures, and Properties of Four Novel Coordination Compounds based on a Flexible Tetrakis(imidazol‐1‐ylmethyl)methane Ligand

Four coordination polymers, namely, [Zn₂(TIYM)(2,6‐PYDC)₂]_n · n(CH₃OH) · 3n(H₂O) ( 1 ), [Cu(TIYM)(2,6‐PYDC)]_n · 3n(H₂O) ( 2 ), [Co(TIYM)(2,6‐PYDC)]_n · n(CH₃OH) · 3n(H₂O) ( 3 ), and [Cd₂(TIYM)(2,6‐PYDC)₂(H₂O)]_n · n(H₂O) ( 4 ) with the flexible N‐containing ligand [tetrakis(imidazol‐1‐ylmethyl)methane (TIYM)] and the N‐containing dicarboxylic acid [2,6‐pyridinedicarboxylic acid (2,6‐PYDC)] were prepared. Compounds 1 – 4 show various structures because of different N–C_center–N angles (θ) of TIYM ligands and changing coordination modes of 2,6‐PYDC. Compounds 1 , 2 , and 3 display a similar 1D ladder‐like chain, whereas 4 gives a 1D quad‐core lifting platform shaped belt. The structural diversities in 1 – 4 suggest that the multiple coordination modes or the different freely twist angles of ligands and the presence of different metal atoms play important roles in the resulting structures of the coordination polymers. Furthermore, the solid‐state luminescence properties of 1 and 4 , and the magnetic properties of 3 were investigated.     

1‐Alkenylcalcium Iodide: Synthesis and Stability

To enhance the scope of heavy calcium‐based Grignard reagents, 1,2‐dihydro‐4‐iodonaphthalene ( 1 ) was reduced with calcium in THF giving tetrakis(thf) (1,2‐dihydronaphth‐4‐yl)calcium iodide ( 2 ). This derivative represents a 1‐alkenylcalcium complex based on X‐ray structure determination and NMR data. The stability of this compound is significantly reduced compared with the aromatic naphthylcalcium iodide.