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A novel complex comprising an ion pair of arginine–arginine carbamate is reported herein, which is isolated from an aqueous l-arginine solution after reacting with CO2. Its structure was unambiguou...

While limited choice of emissive organic linkers with systematic emission tunability presents a great challenge to investigate energy transfer (ET) over the whole visible light range with designable directions, luminescent metal-organic frameworks (LMOFs) may serve as an ideal platform for such study due to their readily tunable structure and composition. Herein, five Zr 6 cluster-based LMOFs, HIAM-400X (X = 0, 1, 2, 3, 4) are prepared using 2,1,3-benzothiadiazole and its derivative-based tetratopic carboxylic acids as organic linkers. Their emission energies range from ~470 to 645 nm. The accessible unsaturated metal sites confer HIAM-400X as a pristine scaffold for postsynthetic modification via linker installation. Six 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids (L) with their emission energies covering the entire visible spectrum were successfully installed into HIAM-400X matrix to form thirty HIAM-400X-L LMOFs, in which the energy transfer can be facilely tuned by controlling its direction, either from the inserted linkers to pristine MOFs or from the pristine MOFs to inserted linkers, and over the whole range of visible light. The combination of the pristine MOFs and the second linkers via linker installation creates a powerful two-dimensional space in tuning the emission via energy transfer in LMOFs. This work sheds light on a new strategy in designing target-specific materials for light-harvesting, energy transfer and related applications.

The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B₂cat₂ has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non- ortho -substituted (hetero)aryl carboxylic acids, and tolerates diverse functional groups including some of the groups active to Ni(0) catalysts. The key to achieve this decarbonylative borylation reaction is the choice of B₂cat₂ as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates aryl carboxylic acids towards oxidative addition of their C(acyl)-O bond to Ni(0) catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted decarbonylation and reductive elimination step that generates the aryl boronic ester product. This mode of boron-promoted carboxylic acid activation is also applicable to other types of reactions .

This density functional theory (DFT) study reveals a detailed plausible mechanism for the Sc-catalyzed C-H cycloaddition of imidazoles to 1,1-disubstituted alkenes to form all-carbon quaternary stereocenters. The Sc complex binds the imidazole substrate to enable deprotonative C2-H bond activation by the Sc-bound α-carbon to afford the active species. This complex undergoes intramolecular cyclization (C═C into Sc-imidazolyl insertion) with exo-selectivity, generating a β-all-carbon-substituted quaternary center in the polycyclic imidazole derivative. The Sc-bound α-carbon deprotonates the imidazole C2-H bond to deliver the product and regenerate the active catalyst, which is the rate-determining step. Calculations illuminate the electronic effect of the ancillary Cp ligand on the catalyst activity and reveal the steric bias caused by using a chiral catalyst that induce the enantioselectivity. The insights can have implications for advancing rare-earth metal-catalyzed C-H functionalization of imidazoles.

We present a detailed DFT mechanistic study on the first Ni-catalyzed direct carbonyl-Heck coupling of aryl triflates and aldehydes to afford ketones. The precatalyst Ni(COD)2 is activated with the phosphine (phos) ligand, followed by coordination of the substrate PhOTf, to form [Ni(phos)(PhOTf)] for intramolecular PhOTf to Ni(0) oxidative addition. The ensuing phenyl-Ni(ii) triflate complex substitutes benzaldehyde for triflate by an interchange mechanism, leaving the triflate anion in the second coordination sphere held by Coulomb attraction. The Ni(ii) complex cation undergoes benzaldehyde C[double bond, length as m-dash]O insertion into the Ni-Ph bond, followed by β-hydride elimination, to produce Ni(ii)-bound benzophenone, which is released by interchange with triflate. The resulting neutral Ni(ii) hydride complex leads to regeneration of the active catalyst following base-mediated deprotonation/reduction. The benzaldehyde C[double bond, length as m-dash]O insertion is the rate-determining step. The triflate anion, while remaining in the second sphere, engages in electrostatic interactions with the first sphere, thereby stabilizing the intermediate/transition state and enabling the desired reactivity. This is the first time that such second-sphere interaction and its impact on cross-coupling reactivity has been elucidated. The new insights gained from this study can help better understand and improve Heck-type reactions.

The hydroformylation reaction is used on a large industrial scale to convert olefins and synthesis gas (CO + H2) into aldehydes. Researchers have recently discovered that a class of cationic Co(II)...

Catalytic enantioselective hydroxylation of prochiral dihydrosilanes with water is expected to be a highly efficient way to access Si-chiral silanols, yet has remained unknown up to date. Herein, we describe a strategy for realizing this reaction: using an alkyl bromide as a single-electron transfer (SET) oxidant for invoking Cu

We report the first computational study on a nickel hydride HAT-initiated catalytic reaction, a novel hydrodefluorination of CF3-substituted aryl alkenes to afford gem-difluoroalkenes. This study provides detailed mechanistic insights into the reaction, including HAT from NiH to C[double bond, length as m-dash]C, a carbon radical rebound to nickel to facilitate chemoselective defluorination, and a two-state reactivity of Ni(ii) enabling σ-bond metathesis with PhSiH3 to regenerate the catalyst. The findings can have implications for developing new metal hydride HAT-initiated reactions.

Ultrashort metal-metal distances (USMMDs, dM-M < 1.900 A) have been realized computationally between the main group metal beryllium. However, due to their ionic charge state and the insufficient stability of their electronic structures and/or thermodynamic stabilities, the known species with ultrashort Be-Be distances are unsuitable for synthesis in the condensed phase, which deters the applications of these interesting structures from being explored. In the present study, using our previously reported global minima species [XH3-Be2H3-XH3]+ (X = N and P) with ultrashort Be-Be distances and well-defined electronic structures as their parent molecules, we designed a series of neutral polygons retaining ultrashort Be-Be distances. These polygons also possess well-defined electronic structures and good thermodynamic stabilities, which are demonstrated by their large HOMO-LUMO gaps of 6.20-7.68 eV, very high vertical detachment energies (VDEs) of 8.96-11.29 eV, rather low vertical electron affinities (VEAs) of -1.21 to +1.78 eV, and unexpectedly high formation energies relative to the building blocks of E- and Be2H3+ (-105.2 to -153.2 kcal mol-1 for the formation of an E-Be bond). The good stability with regard to their electronic structures and thermochemistry reveal their high feasibility to be synthesized in the condensed phase. Thus, we anticipate experimental studies on these interesting nano-polygons to realize structures with USMMDs between main group metals and explore their possible application.

This work illustrates the reductive coupling of electron-rich aryl halides with tertiary alkyl halides under Ni-catalyzed cross-electrophile coupling conditions, which offers an efficient protocol for the construction of all carbon quaternary stereogenic centers. The mild and easy-to-operate reaction tolerates a wide range of functional groups. The utility of this method is manifested by the preparation of cyclotryptamine derivatives, wherein successful incorporation of 7-indolyl moieties is of particular interest as numerous naturally occurring products are composed of these key scaffolds. DFT calculations have been carried out to investigate the proposed radical chain and double oxidative addition pathways, which provide useful mechanistic insights into the part of the reaction that takes place in solution.

The diagonal relationship between beryllium and aluminum and the isoelectronic relationship between BeH unit and Al atom were utilized to design nine new planar and quasi-planar pentacoordinate carbon (ppC) species CAlnBemHxq (n + m = 5, q = 0, ±1, x = q + m − 1) (1a–9a) by attaching H atoms onto the Be atoms in CAl4Be, CAl3Be2−, CAl2Be32−, and CAlBe43−. These ppC species are σ and π double aromatic. In comparison with their parents, these H-attached molecules are more stable electronically, as can be reflected by the more favourable alternative negative–positive–negative charge-arranging pattern and the less dispersed peripheral orbitals. Remarkably, seven of these nine molecules are global energy minima, in which four of them are kinetically stable, including CAl3Be2H (2a), CAl2Be3H− (4a), CAl2Be3H2 (5a), and CAlBe4H4+ (9a). They are the promising target for the experimental realization of species with a ppC.

The subject of metal-metal bonding interactions in molecular systems continues to attract research interest. Chromium heretofore has been the only element known to afford metal-metal distances shorter than 1.700 Å in the form of Cr-Cr multiple bonds. In this computational study, the effect of a triple bond on reducing interatomic distances is simulated through forming three non-classical bonding orbitals between two beryllium atoms, thereby realizing the remarkably short Be-Be distances (1.692-1.735 Å) in kinetically stable global minimum species [L → Be2H3 ← L]+ (L = NH3, PH3, and noble gases Ne-Xe). Such diberyllium complexes make promising candidates for experimental realization. In particular, the Be-Be distance of 1.692 Å in [Ne → Be2H3 ← Ne]+ represents the first example of global minimum having a main group metal-metal distance under 1.700 Å. [TEA → Be2H3 ← TEA]+, which contains the bulky triethylamine (TEA) ligands, is designed as a more promising target for synthesis and isolation in condensed states.

We report the enantioselective synthesis of tetracyclic indolines using cooperative silver(I) and chiral phosphoric acid catalysis. A variety of alkyne-tethered indoles are suitable for this process. Mechanistic studies suggest that the in situ-generated silver(I) chiral phosphate activates both the alkyne and the indole nucleophile in the initial cyclization step through an intermolecular hydrogen bond and the phosphate anion promotes proton transfer. In addition, further modifications of the cyclization products enabled stereochemistry-function studies of a series of bioactive indolines.

The first catalytic hydrohalogenation of alkynes was recently achieved using a copper(I) N-heterocyclic carbene (NHC) complex, and the reaction was found to be syn and anti-Markovnikov selective. The present work is a density functional theory (DFT) computational study (B3LYP and M06) on the detailed mechanism of this remarkable catalytic reaction. The reaction begins with a phenoxide additive turning over the precatalyst (NHC)CuCl into (NHC)Cu(OAr), which subsequently transmetalates with the hydride source Ph2SiH2 to deliver the copper(I) hydride complex (NHC)CuH. (NHC)CuH undertakes hydrocupration of the substrate RC≡CH via alkyne coordination and subsequent migratory insertion into the Cu–H bond, forming (E)-(NHC)Cu(CH═CHR). The migratory insertion step determines the syn selectivity because it occurs by a concerted pathway, and it also determines the anti-Markovnikov regioselectivity that arises from the charge distributions across the Cu–H and C≡C bonds. The brominating agent (BrCl2C)2 uses the bromo...

DFT B3LYP/6-31G(d) calculations were performed to examine the feasibility of graphene-like C42H18 and starbenzene C6(BeH)6 (SBz) polymers as ligands of 3D-extensible sandwich compounds (3D-ESCs) with uninterrupted sandwich arrays. The results revealed that sandwich compounds with three or more C42H18 ligands were not feasible. The possible reason may be the localization of π electrons on certain C6 hexagons due to π-metal interactions, which makes the whole ligand lose its electronic structure basis (higher degree of π electron delocalization) to maintain the planar structure. For comparison, with the aid of benzene (Bz) molecules, the SBz polymers can be feasible ligands for designing 3D-ESCs because the C-Be interactions in individual SBz are largely ionic, which will deter the π electrons on one C6 ring from connecting to those on neighbouring C6 rings. This means that high degree of π electron delocalization is not necessary for maintaining the planarity of SBz polymers. Such a locally delocalized π electron structure is desirable for the ligands of 3D-ESCs. Remarkably, the formation of a sandwich compound with SBz is thermodynamically more favourable than that found for bis(Bz)chromium. The assembly of 3D-ESCs is largely exothermic, which will facilitate future experimental synthesis. The different variation trends on the HOMO-LUMO gaps in different directions (relative to the sandwich axes) suggest that they can be developed to form directional conductors or semiconductors, which may be useful in the production of electronic devices.

Density functional theory calculations (B3LYP and B2PLYP-D2) have been utilized to design and characterize novel homoatomic lithium(0) organometallic complexes of the NHC → Li–Li ← NHC type (NHC = N-heterocyclic carbenes). The computed Li–Li bond length and energy are consistent with those experimentally observed for Li 2 (g). These and other structural and energetic data suggest that such organolithium compounds should be viable targets for synthesis. These compounds would represent a new class of molecular “allotropes” and could have novel reactivities.

The diagonal relationship between beryllium and aluminum and the isoelectronic relationship between BeH unit and Al atom were utilized to design a new series ppC- or quasi-ppC-containing species C5v CBe5H5(+), Cs CBe5H4, C2v CBe5H3(-), and C2v CBe5H2(2-) by replacing the Al atoms in previously reported global minima planar pentacoordinate carbon (ppC) species D5h CAl5(+), C2v CAl4Be, C2v CAl3Be2(-), and C2v CAl2Be3(2-) with BeH units. The three-center two-electron (3c-2e) bonds formed between Be and bridging H atoms were crucial for the stabilization of these ppC species. The natural bond orbital (NBO) and adaptive natural density partitioning (AdNDP) analyses revealed that the central ppCs or quasi-ppCs possess the stable eight electron-shell structures. The AdNDP analyses also disclosed that these species are all 6σ+2π double-aromatic in nature. The aromaticity was proved by the calculated negative nucleus-independent chemical shifts (NICS) values. DFT and high-level CCSD(T) calculations revealed that these ppC- or quasi-ppC species are the global minimum or competitive low-lying local minimum (Cs CBe5H4) on their potential energy surfaces. The Born-Oppenheimer molecular dynamic (BOMD) simulations revealed that the H atoms in C2v CBe5H3(-) and C2v CBe5H2(2-) can easily rotate around the CBe5 cores and the structure of quasi-planar C5v CBe5H5(+) will become the planar structure at room temperature; however, these interesting dynamic behaviors did not indicate the kinetic instability as the basic ppC structures were maintained during the simulations. Therefore, it would be potentially possible to realize these interesting ppC- or quasi-ppc-species in future experiments.

Density functional theory computations (B3LYP) have been used to explore the chemistry of titanium-aromatic carbon "edge complexes" with 1,3-metal-carbon (1,3-MC) bonding between Ti and planar tetracoordinate Cβ . The titanium-coordinated, end-capping chlorides are replaced with OH or SH groups to afford two series of difunctional monomers that can undergo condensation to form oxide- and sulfide-bridged oligomers. The sulfide-linked oligomers have less molecular strain and are more exergonic than the corresponding oxide-linked oligomers. The HOMO-LUMO gap of the oligomers varies with their composition and decreases with growing oligomer chain. This theoretical study is intended to enrich 1,3-MC bonding and planar tetracoordinate carbon chemistry and provide interesting ideas to experimentalists. Organometallic complexes with the TiE2 (E = OH and SH) decoration on the edge of aromatic hydrocarbons have been computationally designed, which feature 1,3-metal-carbon (1,3-MC) bonding between titanium and planar tetracoordinate β-carbon. Condensation of these difunctional monomers by eliminating small molecules (H2O and H2S) produce chain-like oligomers. The HOMO-LUMO gaps of the oligomers decreases with growing oligomer chain, a trend that suggests possible semiconductor properties for oligomers with longer chains.

DFT computations reveal different reaction mechanisms for the oxidative addition of C(sp

Density functional theory (DFT) calculations (B3LYP and M06) have been utilized to study a newly reported Heck-type reaction that uses an allylic or alkenyl alcohol as substrate and palladium as catalyst in the form of a chelate with a chiral pyridine oxazoline (PyrOx) ligand. The reaction not only controls the regio- and enantioselectivities of arylation of the C═C bond, but also forms the carbonyl functionality up to four bonds away from the aryl substituent via tandem C═C bond migration and enol-to-keto conversion. Computations performed on representative reaction systems allow us to propose a detailed mechanism with several key steps. Initial oxidation of palladium(0) by aryldiazonium generates active arylpalladium(II) species that bind the C═C bond of an allylic or alkenyl alcohol. The activated C═C bond inserts into the palladium-aryl moiety to attain aryl substitution and a chiral carbon center, and the resulting complex undergoes β-hydride elimination to give a new C═C bond that can repeat the insertion/elimination process to move down the carbon chain to form an enol that tautomerizes to a highly stable carbonyl final product. The calculations reveal that the C═C bond migratory insertion step determines both the regioselectivity and the enantioselectivity of arylation, with the former arising mainly from the electronic effect of the hydroxyl group on the charge distribution over the C═C bond and the latter originating from a combination of steric repulsion, trans influence, and C-H/π dispersion interactions.

Hydrothermal reactions of alkaline earth metal nitrates with two ditopic carboxylic acids, trans-1,4-cyclohexanedicarboxylic acid (H2CDC) and 1,4-phenylenedipropionic acid (H2PDP), generate two 3-D metal–organic frameworks (MOFs) with empirical formulas [Ca(CDC)(H2O)2]·H2O (1) and [Sr(PDP)(H2O)] (2), respectively. Compound 1 consists of Ca–COO–H2O chains cross-linked through the –C6H10– spacers of the CDC anions, showing slightly open 1-D channels along the crystallographic c axis that accommodate the guest water molecules. Compound 2 exhibits a MOF consisting of wavy 2-D Sr–COO–H2O nets linked by –CH2CH2C6H4CH2CH2– tethers, and the condensed structure appears to arise from conformational flexibility of the ligand spacer.

In the new class of N-heterocyclic carbene (NHC) chelated ruthenium catalysts for Z-selective olefin metathesis, the nitrato-supported complex 3cat appears distinct from all the other carboxylato-supported analogues. We have performed DFT calculations (B3LYP and M06) to elucidate the mechanism of 3cat-catalyzed metathesis homodimerization of 3-phenyl-1-propene. The six-coordinate 3cat transforms via initial dissociation and isomerization into a trigonal-bipyramidal intermediate (5), from which two consecutive metathesis reactions via the side-bound mechanism lead to (Z)-PhCH2CH═CHCH2Ph (major) and (E)-PhCH2CH═CHCH2Ph (minor). In the overall mechanism, 3cat functions similarly to the pivalate-supported analogue 1cat. The substitution of a smaller nitrato group does not change the side-bound olefin attack mechanism for either the initiation or homocoupling metathesis. The chelation of the NHC ligand causes this class of Ru catalysts to favor the side-bound over the bottom-bound mechanism. The calculated ene...

Density functional theory (DFT) calculations (B3LYP, M06, and M06-L) have been performed to investigate the mechanism and origins of Z selectivity of the metathesis homodimerization of terminal olefins catalyzed by chelated ruthenium complexes. The chosen system is, without any simplification, the experimentally performed homocoupling reaction of 3-phenyl-1-propene with 1cat, a pivalate and N-heterocyclic carbene (NHC) chelated Ru precatalyst. The six-coordinate 1cat converts to a trigonal-bipyramidal intermediate (3) through initial dissociation and isomerization. The metathesis reaction of complex 3 with 3-phenyl-1-propene occurs in a side-bound mechanism and generates the trigonal-bipyramidal Ru–benzylidene complex 6. Complex 6 is the active catalyst for the subsequent side-bound metathesis with 3-phenyl-1-propene, which forms metallacyclobutanes that lead to the (Z)- and (E)-olefin homodimers. The transition states of cycloreversion leading to the (Z)- and (E)-olefins differ in energy by 2.2 kcal/mol,...

We have used density functional theory computations to investigate the mechanism of the reaction of an amine with a primary alcohol catalyzed by the ruthenium(II)-PNP pincer complex [PNP = 2,6-bis(di-tert-butylphosphanylmethyl)pyridine]; the reaction produces an imine as the major product. The catalytic cycle includes four stages: (stage I) alcohol dehydrogenation to aldehyde, (stage II) coupling of aldehyde with amine to form hemiaminal, (stage III) hemiaminal dehydration to give imine, and (stage IV) catalyst regeneration by means of H2 elimination of the trans ruthenium dihydride complex produced in stage I. The mechanism is similar to that for amide formation from amine and alcohol that was catalyzed by the RuII-PNN pincer complex [PNN = 2-(di-tert-butylphosphanylmethyl)-6-(diethylaminomethyl)pyridine], the only difference being in stage III. Alcohol dehydrogenation (stage I) occurs by a bifunctional double hydrogen transfer mechanism and alcohol can facilitate stages II and III. The selectivity of imine over ester is governed by stage II: the formation of hemiaminal by means of aldehydeamine coupling is kinetically much more favorable than the alternative aldehydealcohol coupling reaction that yields hemiacetal. Furthermore, the hemiaminal dehydration to give an imine is also kinetically more favorable than the hemiacetal dehydrogenation to give an ester. The selectivity of imine over amide is determined by stage III: the hemiaminal dehydration to give an imine is kinetically much more favorable than the hemiaminal dehydrogenation to give an amide. The essential difference between the RuII-PNP-catalyzed imine synthesis and the RuII-PNN-catalyzed amide formation is that the former prefers hemiaminal dehydration whereas the latter prefers hemiaminal dehydrogenation. In addition, water produced during hemiaminal dehydration can catalyze stages II and III more effectively than alcohol can. By contrast, the water-catalyzed hemiaminal formation does not happen in the RuII-PNN-catalyzed synthesis of an amide because no water is produced in any stage of the reaction.

Density functional theory calculations have been performed to investigate the mechanism of the reactions of amines with primary alcohols to produce amides, catalyzed by the pincer complex Ru(II)-PNN (PNN = 2-(di-tert-butylphosphinomethyl)-6-diethylaminomethyl)pyridine). The results lead us to propose a catalytic cycle that includes four stages: (stage I) alcohol dehydrogenation to aldehyde, (stage II) coupling of aldehyde with amine to form hemiaminal, (stage III) hemiaminal dehydrogenation to amide, and (stage IV) catalyst regeneration via H2 elimination of the trans Ru dihydride complex produced in the two dehydrogenation stages. Both of the dehydrogenation reactions proceed via the bifunctional double hydrogen transfer mechanism rather than the β-H elimination mechanism. The selectivity of amide over ester is determined by the coupling stage in which the aldehyde∧amine coupling to give hemiaminal is more favorable than aldehyde∧alcohol coupling to give hemiacetal. The competition between dehydrogenatio...

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal–organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni2(PDA)2(BPP)(H2O)]·2.5H2O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal–organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.

The open-framework coordination polymer [Er(C9H9O6)(H2O)2]·2.5H2O (C9H9O6 = cis,cis-1,3,5-cyclohexanetricarboxylate) has been synthesized under hydrothermal conditions. Each Er ion is coordinated to nine oxygen atoms belonging to two water molecules and five carboxylate ligands. Its 3-D polymeric structure possesses channels containing the guest water molecules that can be removed to afford a porous material [Er(C9H9O6)(H2O)2]. The metal−organic framework in [Er(C9H9O6)(H2O)2] can withstand the removal of 1 equiv of coordinated water.

Treatment of the well-defined complexes (TTP)Ti(η2-EtC⋮CEt) or trans-(TTP)Ti(THF)2 with vicinal dichloroalkanes or dichloroalkenes results in the production of alkenes or alkynes and 2 equiv of (TTP)TiCl. This net two-electron redox reaction arises from two formal one-electron reduction processes mediated by chlorine atom transfer. Oxygen atom transfer occurs when the Ti(II) porphyrins are treated with several different sulfoxides or epoxides, resulting in two-electron redox products, (TTP)TiO, the sulfide or alkene, and EtC⋮CEt or THF. The electronic properties of the substituents on the sulfoxides or epoxides correlate with the yield and rate of the deoxygenation reactions.

Facile syntheses of the meso-tetra-p-tolylporphyrin (TTP) complexes trans-(TTP)Ti(THF)(2) (1), (TTP)Sn (2), and trans-(TTP)V(THF)(2) (3) are achieved through homogeneous reduction of high-valent precursors using NaBEt(3)H. The composition of the new compound trans-(TTP)Ti(THF)(2) was determined by spectroscopic and chemical characterization. Ligand displacement reactions of trans-(TTP)Ti(THF)(2) with t-BuNC produced a new Ti(II) complex, trans-(TTP)Ti(t-BuNC)(2). The ligand-binding preference of (TTP)Ti(II)L(n)() (n = 1, 2) is picoline approximately pyridine > t-BuNC > PhCtCPh > EtCtCEt > THF.

The reaction of Co(II) with 5,15-dipyridyl-10,20-diphenylporphyrin (H(2)DPyP) produces the first metal-organic coordination polymer supported by a trans meso-bifunctional porphyrin ligand. Formulated empirically as [Co(3)(DPyP)(3)] x 4DMF, this compound exhibits a ribbonlike coordination network consisting of tetranuclear metalloporphyrin cages. The DMF guest molecules fill the intra-ribbon cages as well as the inter-ribbon space. Evacuation of [Co(3)(DPyP)(3)] x 4DMF at 130 degrees C generates [Co(3)(DPyP)(3)] that retains crystallinity, as shown by its powder X-ray diffraction pattern, which is consistent with that of [Co(3)(DPyP)(3)] x 4DMF.

Reaction of Co(NO3)2 or Cd(NO3)2 with 1,3-bis(4-pyridyl)propane (or bpp) in a mixture of benzene and methanol generates one-dimensional (1-D) coordination polymers [Co(bpp)2(NO3)2]·2C6H6 (1) and [Cd(bpp)2(NO3)2]·2C6H6 (2). The isostructural 1 and 2 crystallize in monoclinic space group P 1 . The polymeric framework in 1 or 2 is neutral in which the metal ions have an octahedral geometry and are bridged by two bpp ligands. The six-coordination of Co(II) or Cd(II) is satisfied by its binding two nitrate ions in addition to the four pyridyl nitrogen atoms from four different bpp ligands.