Preparation, characterization, and magnetic behavior of the ln derivatives (ln = nd, la) of a 2,6-diiminepyridine ligand and corresponding dianion

An unprecedented Nd[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N)]NdI(2)(THF) (1) complex was prepared by oxidizing metallic Nd with I(2) in THF and in the presence of 2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N). The magnetic behavior at variable T clearly indicated that the complex should be regarded as a trivalent Nd atom antiferromagnetically coupled to a radical anion. By using the doubly deprotonated form of the diimino pyridine ligand [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)](2-) (2) the corresponding trivalent complexes [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)]Ln (THF)](mu-Cl)(2)[Li(THF)(2)].0.5 (hexane) [Ln = Nd (3), La (4)] were obtained and characterized. Reduction of these species afforded electron transfer to the ligand system which gave ligand dimerization via C-C bond formation through one of the two ene-amido functions of each molecule. The resulting dinuclear [[([2,6-(i-Pr)(2)C(6)H(5)]N-C=(CH(2)))(C(5)H(3)N)([2,6-(i-Pr)(2)C(6)H(5)]N=CCH(2))]Ln(THF)(2)(mu-Cl)[Li(THF)(3)])(2).2(THF) [Ln = Nd (5), La (6)] were isolated and characterized.     

Cationic P-S-X cages (X=Br, I)

The first condensed-phase preparation of ternary P-Ch-X cations (Ch=O-Te, X=F-I) is reported: [P5S3X2]+, [P5S2X2]+, and [P4S4X]+ (X=Br, I). [P5S3X2]+ is formed from the reaction of the Ag+/PX3 reagent with P4S3. The [P5S3X2]+ ions have a structure that is related to P4S5 by replacing P=S by P+--X and S in the four-membered ring by P(X). We provide evidence that the active ingredient of the Ag+/PX3 reagent is the (H2CCl2)Ag-X-PX2+ cation. The latter likely reacts with the HOMO of P4S3 in a concerted HOMO-LUMO addition to give the P5S3X2+ ion as the first species visible in situ in the low-temperature 31P NMR spectrum. The [P5S3X2]+ ions are metastable at -78 degrees C and disproportionate at slightly higher temperatures to give [P5S2X2]+ and [P4S4X]+, probably with the extrusion of 1/n (PX)n (X=Br, I). All six new cage compounds have been characterized by multinuclear NMR spectroscopy and, in part, by IR or Raman spectroscopy. The [P5S2X2]+ salts have a nortricyclane skeleton and were also characterized by X-ray crystallography. The structure of the [P4S4X]+ ion is related to that of P4S5 in that the exo-cage P=S bond is replaced by an isoelectronic P+--X moiety.     

Stability and magnetic properties of transition metal atoms endohedral BnNn (n=12-28) cages

First-principles calculations have been conducted to systemically investigate the stability and magnetic properties of 3d and 4d transitional-metal (TM) atoms doped in the BnNn (n=12,16,20,24,28) cages. Among those cages, the B24N24 is the optimal one for encapsulating 3d and 4d TM atoms according to the computed heat of formation. Inside B24N24 cage, 3d and 4d TM dopants belonging to the same group in the Periodic Table exhibit similar magnetic behaviors. Most of the 3d and 4d TM atoms remain magnetic after doped in the B24N24 cage except for Ni, Zr, and Pd. The magnitudes of the remaining moments for 3d (except for Sc, Ti, and V) and 4d dopants are reduced from those of free atoms. The energy gaps are localized at the doped transition metal atoms. Encapsulations of two TM atoms inside the B24N24 cage were also considered.     

Synthesis, structure, and properties of the new mixed-valent dodecahalogenotrimetallate in(4)ti(3)br(12) and its relation to compounds a(3)ti(2)x(9) (a = k, in; x = cl, br)

Black single crystals of the new dodecahalogenotrimetallate In(4)Ti(3)Br(12) were obtained by reacting InBr(3) with Ti-wire at 450 °C in a silica tube sealed under vacuum. In(4)Ti(3)Br(12) (Pearson symbol hR57, space group R3?m, Z = 3, a = 7.3992(8) ?, c = 36.673(6) ?, 643 refl., 25 param., R(1)(F) = 0.025; wR(2)(F(2)) = 0.046) is a defect variant of a 12 L-perovskite. In(+) cations are 12-fold coordinated in two different ways: In1 as an anticuboctahedron and In2 as a cuboctahedron. In both cases the 5s(2) configuration results in 3 short, 6 medium, and 3 long In-Br distances which might be explained as lone pair effect or second order Jahn-Teller instability. Furthermore there are isolated linear trimers [Ti(3)Br(12)](4-) consisting of facesharing octahedra similar to [Ru(3)Cl(12)](4-). The [Ti(3)Br(12)](4-)-unit has to be described as a mixed-valent d(1)-d(2)-d(1) system. According to magnetic measurements, the Ti-atoms in In(4)Ti(3)Br(12) show strong antiferromagnetic interactions (Θ = -1216(6) K) which might be addressed as weak Ti(3+)-Ti(2+)-Ti(3+) bonds. For comparison, single crystals of K(3)Ti(2)X(9) (X = Cl, Br) were synthesized and their structures refined. The rotation of the Ti(2)X(9)(3-) dimers reduced the symmetry of the well-known Cs(3)Cr(2)Cl(9) type from P6(3)/mmc to P6(3)/m and resulted in the formation of merohedral twins. According to the unit cell volumes In(+) is smaller than K(+) in all cases.     

Frontier orbitals of trivalent cages: (3,6) cages and (4,6) cages

A qualitative molecular-orbital treatment and group-theoretical analysis reveals the nature of the frontier orbitals of (3,6) and (4,6) polyhedral cages, consisting of a hexagonal network with triangular and square defects, respectively. Leapfrog (3,6) cages have two nonbonding filled orbitals. Leapfrog (4,6) cages have a high HOMO-LUMO gap, while nonleapfrog (4,6) cages with octahedral symmetry have a very small HOMO-LUMO gap. The symmetry of the frontier orbitals is determined.     

Ln(14)Na(3)Ru(6)O(36) (ln = pr, nd): two new complex lanthanide-containing oxides of ruthenium

The lanthanide-containing ruthenium oxides Ln14Na3Ru6O36 (Ln = Pr, Nd) were prepared as single crystals from molten sodium hydroxide. The two compounds crystallize in the rhombohedral space group Rc with cell constants of a = 9.7380(2) and 9.6781(2) Angstrom and c = 55.5716(18) and 55.4156(18) Angstrom for Ln14Na3Ru6O36 (Ln = Pr, Nd), respectively. The structure of the two compounds is composed of two types of slabs that alternate in an AB fashion. Each slab consists of three layers and are arranged to yield a unit cell with a 12-layer structure. Both compounds exhibit magnetic behavior consistent with canted antiferromagnetism.     

C28X4（X=H,Cl）,CX4（X=H,Cl）的结构和电子光谱的理论研究

用ＩＮＤＯ法对Ｃ２８Ｘ４（Ｘ＝Ｈ，Ｃｌ）和ＣＸ４（Ｘ＝Ｈ，Ｃｌ）进行几何构型优化，得到Ｔｄ对称性的构型Ｃ２８Ｘ４有４种键、４种不等同原子，基态为稳定的闭壳层分子，以此构型为基础计算了上述分子的电子光谱，并预测Ｃ２８Ｘ４的电子光谱。     

Formation and characterization of the uranium methylidene complexes CH2 = UHX (X = F, Cl, and Br)

The reactions between uranium atoms and CH3X (X = F, Cl, and Br) molecules are investigated in a solid argon matrix. The major products formed on ultraviolet irradiation are the CH2=UHX methylidene complexes. DFT calculations predict these triplet ground-state structures to be stable and to have significant agostic interactions. Parallels between the uranium and analogous thorium methylidene complexes are discussed.     

Formation of high nuclearity mixed-valent polyoxovanadates in the presence of copper amine complexes

Two new Müller-type clusters, a one-dimensional solid [Cu(en)]_{2 4}[Cl ⊂V₁₅O₃₆]−12H₂O1, and a three-dimensional solid [Cu(pn)]_{2 4}[Cl ⊂V₁₈O₄₂]·12H₂O2, have been synthesised by employing identical hydrothermal conditions e_xcept varying the nature of organic diamine.1 crystallised in a chiral space groupP2₁2₁2₁ witha = 12.757(1),b = 18.927(2) andc = 28.590(3) ?, andZ =4.2 crystallised in a tetragonal system with space groupP4/nnc,a = 15.113(1) andc = 18.542(3) ?, andZ = 2. Mixed-valent vanadium ions in structures1 and2 have been established both by magnetisation and bond-length bond-valence measurements. Chemistry of formation of high nuclearity polyoxovanadate clusters is discussed. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

M4 @Si28 (M=Al,Ga): metal-encapsulated tetrahedral silicon fullerene

It is known that silicon fullerenes cannot maintain perfect cage structures like carbon fullerenes. Previous density-functional theory calculations have shown that even with encapsulated species, nearly all endohedral silicon fullerenes exhibit highly puckered cage structures in comparison with their carbon counterparts. In this work, we present theoretical evidences that the tetrahedral fullerene cage Si(28) can be fully stabilized by encapsulating a tetrahedral metallic cluster (Al(4) or Ga(4)). To our knowledge, this is the first predicted endohedral silicon fullerene that can retain perfectly the same cage structure (without puckering) as the carbon fullerene counterpart (T(d)-C(28) fullerene). Density-functional theory calculations also suggest that the two endohedral metallosilicon fullerenes T(d)-M(4)@Si(28) (M=Al and Ga) can be chemically stable because both clusters have a large highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap ( approximately 0.9 eV), strong spherical aromaticity (nucleus-independent chemical shift value of -36 and -44), and large binding and embedding energies.     

Cage and tube structures of medium-sized zinc oxide clusters (ZnO)n (n=24, 28, 36, and 48)

Following our recent work which revealed that the lowest-energy structures of (ZnO)n (n=9-18) follow cage and tube structural growth patterns with stacks of small subunits of (ZnO)2 and (ZnO)3 [Wang et al., J. Phys. Chem. C 111, 4956 (2007)], we have extended the search for the most stable structures to some larger clusters, i.e., (ZnO)n (n=24, 28, 36, and 48) by using gradient-corrected density-functional theory (DFT). A number of starting configurations belonging to different structural motifs were generated from handmade constructions with chemical intuition and then optimized via DFT calculations. Within the size range studied, cage and tube structures were found to be the most preferred structural motifs for the (ZnO)n clusters.     

Oxo-, hydroxo-, and peroxo-bridged Fe(III) phosphonate cages

A series of five Fe(III) phosphonate clusters with four different topologies is reported. The choice of coligand carboxylate plays an important role in directing the structure of the molecule. [Fe9(O)4(O2CCMe3)13(C10P)3] (1) and [Fe9(O)2(OH)(CO2Ph)10(C10P)6(H2O)2](CH3CN)7 (2; camphyl phosphonic acid, C10H17PO3H2 = C10PH2) represent two unprecedented nonanuclear Fe(III) cages having Fe9O4 and Fe9(O)2(OH) core structures, respectively. Whereas [Fe6O2(O)2(O2CCMe3)8(C10P)2 (H2O)2](CH3CN)4 (3) is a peroxo-bridged hexameric compound with an Fe6(O)2(O2) core. [Fe4(O)(O2CCMe3)4(C10P)3(Py)4](CH3CN)3 (4) and [Fe4(O)(O2CPh)4(C10P)3(Py)4](Py)3(CH3CN)2 (5; Py = pyridine) represents two tetranuclear clusters with the same Fe4O core structure.     

Geometric and electronic structures of (BeO)(N) (N = 2-12, 16, 20, and 24): rings, double rings, and cages

The structure of (BeO)(N) clusters (N = 2-12, 16, 20, and 24) are investigated using the method combining the genetic algorithm with density function theory. Benchmark calculation indicates that THSSh functional is reliable to predict the structures of (BeO)(N) cluster. The global minimum structures of (BeO)(N) clusters are rings up to N = 5, double rings at N = 6 and 7 and cages at N ≥ 8. Besides, almost all of the structures of (BeO)(N) cluster are aromatic according to the NICS criterion. Adaptive natural density partitioning analysis reveals that C(6), (BN)(3), and (BeO)(3) rings (C(24) and (BeO)(12) fullerenes) are similar in bonding patterns. The building-up principle of (BeO)(N) is different from that of covalent (BN) and ionic (LiF and MgO) clusters.     

Probing the electronic structure of early transition-metal oxide clusters: polyhedral cages of (V2O5)n(-) (n = 2-4) and (M2O5(2)(-) (M = Nb, Ta)

Vanadium oxide clusters, (V2O5)n, have been predicted to possess interesting polyhedral cage structures, which may serve as ideal molecular models for oxide surfaces and catalysts. Here we examine the electronic properties of these oxide clusters via anion photoelectron spectroscopy for (V2O5)n(-) (n = 2-4), as well as for the 4d/5d species, Nb4O10(-) and Ta4O10(-). Well-resolved photoelectron spectra have been obtained at 193 and 157 nm and used to compare with density functional calculations. Very high electron affinities and large HOMO-LUMO gaps are observed for all the (V2O5)n clusters. The HOMO-LUMO gaps of (V2O5)n, all exceeding that of the band gap of the bulk oxide, are found to increase with cluster size from n = 2-4. For the M4O10 clusters, we find that the Nb/Ta species yield similar spectra, both possessing lower electron affinities and larger HOMO-LUMO gaps relative to V4O10. The structures of the anionic and neutral clusters are optimized; the calculated electron binding energies and excitation spectra for the global minimum cage structures are in good agreement with the experiment. Evidence is also observed for the predicted trend of electron delocalization versus localization in the (V2O5)n(-) clusters. Further insights are provided pertaining to the potential chemical reactivities of the oxide clusters and properties of the bulk oxides.     

Anion-controlled nuclearity in nickel complexes with potentially dinucleating, poly(oxime) amine ligands

Two new ligands consisting of bis(oxime) amine units tethered by a bridge have been synthesized. Their nickel chloride and nickel nitrate complexes have also been synthesized and characterized by X-ray crystallography, FTIR, mass spectrometry, and elemental analysis. One of these ligands, L1 (N,N,N',N'-tetra(1-propan-2-onyl oxime)-diamino-m-xylene), is always dinucleating, while the other ligand, L2 (N,N,N',N'-tetra(1-propan-2-onyl-oxime)-1,3-diaminopropane), shows an unusual anion dependence on the nuclearity. When nickel chloride is used, the ligand acts in a dinucleating manner and coordinates two nickels; however, when nickel nitrate is used, the ligand acts in a monodentate fashion and coordinates only one nickel. Once the mononuclear complex is formed, it is not possible to add a second nickel if Ni(NO(3))(2) is used as the nickel source; it is possible, however, to add a second nickel if NiCl(2) is used as the nickel source. The dinuclear complex can be converted to the mononuclear one by either using silver nitrate to exchange the chloride anions for nitrates or by dissolving the complex in water. Ni(2)(L1)Cl(4)(DMF)(2).DMF: orthorhombic, P2(1)2(1)2(1), a = 12.2524(11) A, b = 16.6145(15) A, c = 20.1234(19) A, V = 4096.5(6) A(3), Z = 4. [Ni(2)(L2)Cl(4)(DMF)](2).2DMF: triclinic, P-1, a = 12.5347(5) A, b = 12.5403(5) A, c = 14.3504(6) A, alpha = 67.348(1) degrees , beta = 69.705(1) degrees , gamma = 81.549(1) degrees , V = 1952.25(14) A(3), Z = 1. Ni(L2).(NO(3))(2): monoclinic, P2(1)/n, a = 9.6738(3) A, b = 30.2229(9) A, c = 15.8238(5) A, beta = 97.995(1) degrees , V = 4581.4(2) A(3), Z = 8.     

Structure and relative stability of drum-like C4nN2n n = 3-8) cages and their hydrogenated products C4nH4nN2n (n = 3-8) cages

The drum-like C4nNn (n = 3-8) cages and corresponding hydrogenated products C4n H4nN2n (n = 3-8) are studied at the DFT B3LYP/6-31G** level. Their structures, energies, and vibrational frequencies have been investigated. Comparison of heat of formation reveals that C32N16 with D8h symmetry in the C4nN2n (n = 3-8) series is a promising candidate as high energy density matter. The calculation of the DeltaG and DeltaH for the hydrogenation of C4nN2n (n = 3-8) shows that it is an exothermic reaction at 298 K and the C4nH4nN2n (n = 3-8) species are more stable than C4nN2n (n = 3-8) species. The analysis of molecular orbital and selected bond lengths of N-N and C-C provides another insight about their stability. Combined with the nucleus-independent chemical shifts (NICS) calculation, it is indicated that molecular stability for cage-shaped molecules depends on not only aromatic character but also the cage effect.     

Mimicking zeolite to its core: porous sodalite cages as hangers for pendant trimeric M3(OH) clusters (M = Mg, Mn, Co, Ni, Cd)

A new class of zeolite-type porous materials in which 3D frameworks are covalently functionalized with crystallographically ordered pendant metal clusters have been synthesized. This work demonstrates a new paradigm for and the feasibility of functionalizing zeolite-type frameworks through the conversion of extraframework sites in mineral zeolites into part of the framework for occupation by dangling metal clusters in metal-organic frameworks.     

Synthesis of S-(28a-homobetulin-28a-yl) thiophosphate,thiophosphonate, and thiophosphinate

A concise synthesis of thiophosphate, phenylthiophosphonate, and diphenylthiophosphinate esters bearing a 28a-homolupane residue is reported. The new triterpenes were obtained from the readily available 3-O-acetylichopanol by a nucleophilic substitution of the corresponding mesylate with thiocyanate ion followed by a Michaelis–Arbuzov reaction. These results open the way to new lupane-type derivatives having a thiophosphorus moiety at the lupane core as potential anticancer compounds. Additionally, the cytotoxic activities of the new homolupane compounds were evaluated in vitro.     

Heterobimetallic lithium alkyltriimido aluminate cages containing the [R'Al(NR)3]4- tetraanion (R' = Bu(n), Et; R = 2-OMeC6H4)

Attempted metallation of a triamidoaluminane gives a complex containing the [R'Al(NR)3]4- anion whose formal tetranegative charge is the highest charge observed crystallographically for a simple mononuclear imido main group anion system.