Wednesday, February 22, 2006

JACS: Kroeker and Leznoff; 15N, 207Pb, etc.

J. Am. Chem. Soc., ASAP Article 10.1021/ja0566634 S0002-7863(05)06663-1
Web Release Date: February 22, 2006

Structure and Multinuclear Solid-State NMR of a Highly Birefringent Lead-Gold Cyanide Coordination Polymer

Michael J. Katz, Pedro M. Aguiar, Raymond J. Batchelor, Alexei A. Bokov, Zuo-Guang Ye,* Scott Kroeker,* and Daniel B. Leznoff*


The coordination polymer Pb(H2O)[Au(CN)2]2 (1) was synthesized by the reaction of KAu(CN)2 and Pb(NO3)2. The structure contains 1-D chains of lead(II)-OH2 linked via Au(CN)2- moieties, generating a 2-D slab; weak aurophilic interactions of 3.506(2) and 3.4885(5) Å occur within and between slabs. The geometry about each lead(II) is bicapped trigonal prismatic, having six N-bound cyanides at the prism vertices and waters at two of the faces. Dehydration at 175 C yields microcrystalline Pb[Au(CN)2]2 (2), which, along with 1, was examined by 13C, 15N, 1H, and 207Pb solid-state NMR methods. Two 15N resonances are assigned to the 2-bridging and hydrogen-bonding cyanides in 1. Upon dehydration, the 207Pb NMR spectrum becomes axially symmetric and yields a reduced shielding span, indicating higher site symmetry, while the 13C and 15N spectra reveal a single cyanide. Although no single-crystal X-ray structure of 2 could be obtained, a structure is proposed on the basis of the NMR and X-ray powder data, consisting of a lead(II) center in a distorted square-prismatic environment, with cyanides present at each corner. The birefringence of single crystals of 1 is found to be 7.0 × 10-2 at room temperature. This value is large compared to that of most optical materials and can be attributed to the anisotropy of the 2-D slabs of 1, with all CN bonds aligned in the same direction by the polarizable lead(II) center.

Inorg Chem: Wasylishen, 13C tensors in diphenylacetylene, Pt complex

Acetylenic Carbon-13 Chemical Shift Tensors for Diphenylacetylene and (2-Diphenylacetylene)Pt(PPh3)2: A Solid-State NMR and Theoretical Study

Kristopher J. Harris, Guy M. Bernard, Chris McDonald, Robert McDonald, Michael J. Ferguson, and Roderick E. Wasylishen*


The structure of (2-diphenylacetylene)Pt(PPh3) 2, as well as those of its dichloromethane and benzene solvates, is determined via X-ray crystallography. An investigation of the chemical shift (CS) tensors of the 13C-labeled carbons in Ph13C13CPh and (2-Ph13C13CPh)Pt(PPh3)2·(C6H6) is carried out via analysis of 13C NMR spectra from stationary solid samples. The principal components of the CS tensors as well as their orientations with respect to the 13C,13C internuclear vector are determined. DFT calculations of these CS tensors are in close agreement with the experimental values. For diphenylacetylene (tolane), the orientations and principal-component magnitudes of the alkynyl carbon CS tensors are comparable to those for other alkynyl carbons, although the CS tensor is not axially symmetric in this case. Coordination to platinum causes a change in the CS tensor orientation and a net increase in the isotropic chemical shift, resulting from a significant increase in two principal components (11 and 33) while the third (22) decreases only slightly. The measured carbon CS tensors in the platinum complex bear a striking similarity to those of the alkenyl carbons in trans-Ph(H)C=C(H)Ph, and a short theoretical discussion of these observations is presented.

Tuesday, February 21, 2006

Chem. Mater - Kennedy - 2 papers on new mesoporous AlPO; 31P, 27Al

Chem. Mater., ASAP Article 10.1021/cm052174r S0897-4756(05)02174-5
Web Release Date: February 18, 2006

Synthesis and Characterization of a New Microporous Material. 1.
Structure of Aluminophosphate EMM-3

Mobae Afeworki, Douglas L. Dorset, Gordon J. Kennedy, and Karl G.
ExxonMobil Research & Engineering Company, 1545 Rt. 22 East, Annandale,
New Jersey 08801


Molecular sieves are extensively used in the chemical and petrochemical
industry as catalysts, absorbents, and ion exchangers. New molecular
sieve structures have the potential to improve the performance of these
materials. We have discovered a new microporous material, EMM-3,
prepared in both aluminophosphate and silicoaluminophosphate
compositions by use of N,N,N,N',N',N'-hexamethyl-1,6-hexanediammonium as
a template at 160 C in 20 h. The structure of EMM-3 has been solved and
refined from powder data by use of synchrotron X-ray radiation. The unit
cell for the calcined AlPO form of EMM-3 has monoclinic space group
symmetry, I2/m11, with cell dimensions a = 10.3132(2), b = 12.6975(3),
and c = 21.8660(4) and = 89.656(1). The microporous structure contains
12-ring, sinusoidal, unidimensional channels with pore openings of 6.1 ×
6.5 Å. This new framework contains two new building chains, not observed
in other known framework structures. The 31P and 27Al NMR spectra of the
calcined/dehydrated form are in agreement with a fully connected
tetrahedral structure containing five unique phosphorus and five unique
aluminum atoms. The material is stable upon calcination and absorbs 9-10
wt % hydrocarbons.


Chem. Mater., ASAP Article 10.1021/cm052175j S0897-4756(05)02175-7
Web Release Date: February 18, 2006

Synthesis and Characterization of a New Microporous Material. 2. AlPO
and SAPO Forms of EMM-3
Mobae Afeworki, Gordon J. Kennedy, Douglas L. Dorset, and Karl G.

ExxonMobil Research & Engineering Company, 1545 Rt. 22 East, Annandale,
New Jersey 08801


A new aluminophosphate (AlPO) material, EMM-3, was recently synthesized
at ExxonMobil. EMM-3, ExxonMobil material no. 3, was synthesized in both
the AlPO- and SAPO-forms. The structure of the AlPO-form of EMM-3 has
been solved using FOCUS Fourier recycling method with the help of a
series of characterization techniques. Multinuclear, multifield
solid-state NMR, SEM, and powder XRD measurements were performed in
order to help understand the molecular arrangement and structure of the
material. Carbon-13 CPMAS NMR of the as-synthesized material shows that
the structure-directing agent remains intact with no strong chemical
shift anisotropy indicating considerable mobility of the
structure-directing agent in the internal voids of EMM-3. The
multitechnique characterization of EMM-3 shows that only one type of
crystal morphology is present, indicating the high purity of the sample.
The XRD pattern of calcined-dry EMM-3 is consistent with orthorhombic
symmetry. Distinct changes in local symmetry of the P and Al atoms occur
upon calcination and subsequent hydration, and these changes are
observed by solid-state NMR. Whereas the 31P MAS NMR of calcined-dry
EMM-3 shows three peaks in a ratio of 1:2:3, upon rehydration, the 31P
MAS NMR of EMM-3 shows that there are at least five distinct
environments for the P atoms in a ratio of 1:2:1:1:1. The
calcined-rehydrated sample shows a strong octahedral 27Al signal, due to
framework hydration. SAPO-forms of EMM-3 were successfully synthesized
and show acid activities. The Brnsted acidity was measured
quantitatively by 1H MAS NMR.

Monday, February 13, 2006

PCCP: VT 2H NMR; inclusion compounds

Physical Chemistry Chemical Physics, 2006, (Advance Article)

Molecular dynamics and ordering of pyridine in its cyclophosphazene
inclusion compound as evaluated by solid state 2H NMR spectroscopy

Jorge A. Villanueva-Garibay and Klaus Müller

Variable temperature 2H NMR experiments (line shape analysis, relaxation
studies) were carried out on the
pyridine-d5–tris-(1,2-dioxyphenyl)-cyclotriphosphazene inclusion
compound in the temperature range between 110–300 K. It is found that
the pyridine guests are highly mobile throughout the whole temperature
range covered here. The observation of three superimposed 2H NMR signals
can be understood in terms of a particular (motionally averaged)
orientation of the pyridine molecules, which is a consequence of the
molecular symmetry of the pyridine guests and the imposed channel
restrictions. The experimental data are consistent with a combined
rotation on cone–small angle fluctuation model, which assumes a fast
molecular reorientation between two superimposed cones with an opening
angle for the inner cone between 59–73° (angle of fluctuation between
1–3°). On the basis of this model assumption it is possible to reproduce
both the experimental 2H NMR line shapes and the spin–lattice relaxation
data in a quantitative way. The analysis of the partially relaxed
spectra (inversion recovery experiments) yields the correlation times
for this overall motional process. They follow an Arrhenius behavior
from which an activation energy of 8.7 ± 0.4 kJ mol–1 is derived. The
results are discussed in the framework of the published data for related

Friday, February 03, 2006

JACS: CMAR sequence - Griffin

J. Am. Chem. Soc., ASAP Article 10.1021/ja0550430 S0002-7863(05)05043-2

Broadband Homonuclear Correlation Spectroscopy at High Magnetic Fields and MAS Frequencies

Gaël De Paëpe, Marvin J. Bayro, Józef Lewandowski, and Robert G. Griffin*

Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139


We present a new homonuclear recoupling sequence, CMAR, that allows observation of 2D 13C-13C correlation spectra at high magnetic fields and MAS frequencies (10-30 kHz). The main advantages of the sequence are that it provides efficient, broadband dipolar recoupling and concurrently decouples the 1H spins from the 13C's. Thus, no additional 1H decoupling is required during the mixing period, thereby significantly reducing the radio frequency power requirements for the experiment. Thus, CMAR significantly extends the range of applicability of the usual homonuclear recoupling techniques and should be of major interest for structure determinations of biomolecules at high magnetic fields.

JACS: NMR Chemical Shift Powder Pattern Recoupling at High Spinning Speed and Theoretical Tensor Evaluation Applied to Silk Fibroin

J. Am. Chem. Soc., ASAP Article 10.1021/ja051730f S0002-7863(05)01730-0

NMR Chemical Shift Powder Pattern Recoupling at High Spinning Speed and Theoretical Tensor Evaluation Applied to Silk Fibroin

Raiker Witter,* Ulrich Sternberg, and Anne S. Ulrich

Contribution from the Forschungszentrum Karlsruhe, IBG, POB 3640, 76021 Karlsruhe, Germany, and University of Karlsruhe, IOC, Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany


The NMR pulse sequence RAI (recoupling of anisotropy information) has been improved to obtain powder patterns at high MAS spinning speeds. The 2D iso-aniso experiment displays the static chemical shift spectra on the indirect dimension and the MAS spectra on the direct dimension; hence overlapping chemical shift tensor patterns can be well resolved. This efficient technique is applicable to compounds containing 13C sp3 (C, C) and sp2 (C=O) sites with higher chemical shift (CS) anisotropy (CSA), and the reliability of the method was tested here on the 13C chemical shift tensors of polycrystalline glycine, alanine, and serine. Subsequently, the same experiment was applied to the native silk protein fibroin from Bombyx mori, which consists mainly of these three amino acids. Molecular dynamics (MD) simulations of the silk II crystal structure of Takahashi et al. (Takahashi et al. Int. J. Biol. Macromol. 1999, 24, 127-138) were carried out to study the influence of motions on the chemical shift tensors. The 13C chemical shift tensors were calculated using the bond polarization theory BPT on 200 structures created by an MD simulation. Very good agreement of the theoretical chemical shift anisotropy values with the experimental NMR results was obtained. The tensor orientations in the protein structure could thus be reliably derived.

JACS: Four-Membered Group 13 Metal(I) N-Heterocyclic Carbene Analogues: Synthesis, Characterization, and Theoretical Studies

Joel, of interest, given Ga and Cu work

J. Am. Chem. Soc., ASAP Article 10.1021/ja057967t S0002-7863(05)07967-9

Copyright © 2006 American Chemical Society
Four-Membered Group 13 Metal(I) N-Heterocyclic Carbene Analogues: Synthesis, Characterization, and Theoretical Studies

Cameron Jones,* Peter C. Junk, Jamie A. Platts, and Andreas Stasch

School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT United Kingdom, and School of Chemistry, Monash University, PO Box 23, Victoria 3800, Australia


The synthesis, spectroscopic and structural characterization of the monomeric, four-membered group 13 metal(I) heterocycles ([:M{2-N,N'-(Ar)NC(NCy2)N(Ar)}], M = Ga or In, Ar = C6H3Pri2-2,6) and an isomeric thallium complex are reported. Theoretical studies on these complexes, which are analogues of four-membered N-heterocyclic carbenes, suggest they should act as good -donor ligands.

Inorg Chem: Double-Stranded, Dicopper(I) Helicate Containing Achiral Bis(bidentate) Schiff Bases

Joel, possibly of interest? Perhaps analogs?

Inorg. Chem., ASAP Article 10.1021/ic051478c S0020-1669(05)01478-3
Web Release Date: January 27, 2006

Asymmetric Transformation of a Double-Stranded, Dicopper(I) Helicate Containing Achiral Bis(bidentate) Schiff Bases

Nicolle C. Habermehl, Patricia M. Angus, Nathan L. Kilah, Lasse Norén, A. David Rae, Anthony C. Willis, and S. Bruce Wild*

Research School of Chemistry, Institute of Advanced Studies, Australian National University, Canberra, ACT 0200, Australia, and Department of Chemistry, Faculty of Science, Australian National University, Canberra, ACT 0200, Australia


Reactions of the bis(bidentate) Schiff-bases N,N'-bis(6-alkyl-2-pyridylmethylene)ethane-1,2-diamine (where alkyl = H, Me, iPr) (L) with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluorophosphate afforded, respectively, the double-stranded, dinuclear metal helicates [T-4-(R*,R*)]-(±)-[M2L2](PF6)2 (M = Cu, Ag). The helicates were characterized by 1H and 13C NMR spectroscopy, conductivity, microanalysis, and single-crystal X-ray structure determinations on selected compounds. Intermolecular ligand exchange and intramolecular inversion rates for the complexes were investigated by 1H NMR spectroscopy. Reversible intermolecular ligand exchange between two differently substituted helicates followed first-order kinetics. The rate constants (k) and corresponding half-lives (t1/2) for ligand exchange for the dicopper(I) helicates were k = (1.6-1.8) × 10-6 s-1 (t1/2 = 110-120 h) in acetone-d6, k = 4.9 × 10-6 s-1 (t1/2 = 40 h) in dichloromethane-d2, and k > 2 × 10-3 s-1 (t1/2 < 5 min) in acetonitrile-d3. Ligand exchange for the disilver(I) helicates occurred with k > 2 × 10-3 s-1 (t1/2 < 5 min). Racemization of the dicopper(I) helicate by an intramolecular mechanism was investigated by determination of the coalescence temperature for the diastereotopic isopropyl-Me groups in the appropriate complex, and G 76 kJ mol-1 was calculated for the process in acetone-d6, nitromethane-d3, and dichloromethane-d2 with G = 75 kJ mol-1 in acetonitrile-d3. Complete anion exchange of the hexafluorophosphate salt of a dicopper(I) helicate with the enantiomerically pure -(-)-tris(catecholato)arsenate(V) ([As(cat)3]-) in the presence of Dabco gave the two diastereomers (R,R)-[Cu2L2]{-(-)-[As(cat)3]}2 and (S,S)-[Cu2L2]{-(-)-[As(cat)3]}2 in up to 54% diastereomeric excess, as determined by 1H NMR spectroscopy. The diastereomerically and enantiomerically pure salt (R,R)-[Cu2L2]{-(-)-[As(cat)3]}2 crystallized from the solution in a typical second-order asymmetric transformation. The asymmetric transformation of the dicopper(I) helicate is the first synthesis of a diastereomerically and enantiomerically pure dicopper(I) helicate containing achiral ligands.

Inorg Chem: Silver(I) Coordination Networks Bearing Flexible Thioethers

Hiyam, please check:

Inorg. Chem., ASAP Article 10.1021/ic051357c S0020-1669(05)01357-1
Web Release Date: January 27, 2006

Synthesis and Characterization of Silver(I) Coordination Networks Bearing Flexible Thioethers: Anion versus Ligand Dominated Structures

Mohamed Osman Awaleh, Antonella Badia, François Brisse,* and Xian-He Bu

Département de Chimie, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal Québec, Canada H3C 3J7, and Department of Chemistry, Nankai University, Tianjin 300071, P. R. China


This report describes the synthesis and X-ray characterization of a series of LnAgX complexes wherein Ln = PhS(CH2)nSPh (n = 2, 4, 6, 10) and X = CF3SO3-, CF3COO-, CF3CF2COO-, CF3CF2CF2COO-, NO3-, and ClO4-. This study was undertaken in order to rationalize the structure of the coordination networks formed as a function of the anion coordinating strength and the ligand structure. The following complexes were examined: with L2, CF3SO3- (1), CF3COO- (2), ClO4- (3); L4, CF3SO3- (4), CF3COO- (5), CF3CF2COO- (6), CF3CF2CF2COO- (7); L6, CF3COO-·H2O (8), CF3CF2COO- (9), CF3CF2CF2COO- (10); and L10, NO3- (11). The anions selected are classified in three groups of increasing coordinating strength: perchlorates, fluorosulfonates, and perfluorocarboxylates. Except in two cases, all complexes form 2D-coordination networks. The 2D-network in 1 (L2, CF3SO3-) is made up of Ag(I) and L2, while the anion is only a terminal co-ligand that completes the trigonal coordination around Ag(I). In 4 (L4, CF3SO3-), a 1D-coordination polymer, [Ag-L4-], is observed where the anions are coordinated to Ag(I) in a trigonal fashion. The perfluorocarboxylates form tetrameric units in a zigzag shape, but only with the L4 ligand. In these (6 and 7), the silver-silver distances are very short, especially those of the central bond, indicating the presence of weak Ag-Ag interactions. Dimers, with short silver-silver distances, are observed with ligands L2 and L6 and perfluorocarboxylates. In 8 (L6, CF3COO-·H2O), a 3D channel-like structure is built through water molecules that connect adjacent layers. An unusual stoichiometry is noted in 3 (L2, ClO4-, acetone); Ag:L is 4:2.5. In 11 (L10 and NO3-), the nitrate acts as a bidentate ligand and an [Ag-NO3-] chain is formed. Adjacent chains are linked by the L10 ligands into a 2D-coordination network.