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Reaction of RuCl2(PPh3)3 with LiNN′ (NN′ = 2-[(2,6-diisopropylphenyl)imino]pyrrolide) affords a single product, with the empirical formula RuCl[(2,6-iPr2C6H3)N=CHC4H3N](PPh3)2. We identify this species as a σ-pyrrolato complex, [Ru(NN′)(PPh3)2]2(μ-Cl)2 (3b), rather than mononuclear RuCl(NN′)(PPh3)2 (3a), on the basis of detailed 1D and 2D NMR characterization in solution and in the solid state. Retention of the chelating, σ-bound iminopyrrolato unit within 3b, despite the presence of labile (dative) chloride and PPh3 donors, indicates that the chelate effect is sufficient to inhibit σ → π isomerization of 3b to a piano-stool, π-pyrrolato structure. 2D COSY, SECSY, and J-resolved solid-state 31p NMR experiments confirm that the PPh3 ligands on each metal center are magnetically and crystallographically inequivalent, and 31p CP/MAS NMR experiments reveal the largest 99Ru-31P spin-spin coupling constant (¹J(99Ru,31P) = 244 ± 20 Hz) yet measured. Finally, 31P dipolar-chemical shift spectroscopy is applied to determine benchmark phosphorus chemical shift tensors for phosphine ligands in hexacoordinate ruthenium complexes. [ABSTRACT FROM AUTHOR]

Solid-state [sup 17]O NMR spectroscopy is employed to characterize powdered samples of known monoclinic and orthorhombic modifications of [sup 17]O-enriched triphenylphosphine oxide, Ph[sub 3]PO. Precise data on the orientationdependent [sup 17]O electric field gradient (EFG) and chemical shift (CS) tensors are obtained for both polymorphs. While the [sup 17]O nuclear quadrupolar coupling constants (C[sub Q]) are essentially identical for the two polymorphs (C[sub Q] = -4.59 ± 0.01 MHz (orthorhombic); C[sub Q] = -4.57 ± 0.01 MHz (monoclinic)), the spans (Ω) of the CS tensors are distinctly different (Ω = 135 ± 3 ppm (orthorhombic); Ω = 155 ± 5 ppm (monoclinic)). The oxygen CS tensor is discussed in terms of Ramsey's theory and the electronic structure of the phosphorus-oxygen bond. The NMR results favor the hemipolar σ-bonded R[sub 3]P[sup +]-O[sup -] end of the resonance structure continuum over the multiple bond representation. Indirect nuclear spin-spin (J) coupling between [sup 31]P and [sup 17]O is observed directly in [sup 17]O magicangle-spinning (MAS) NMR spectra as well as in [sup 31]P MAS NMR spectra. Ab initio and density-functional theory calculations of the [sup 17]O EFG, CS, and ¹J([sup 31]P,[sup 17]O) tensors have been performed with a variety of basis sets to complement the experimental data. This work describes an interesting spin system for which the CS, quadrupolar, J, and direct dipolar interactions all contribute significantly to the observed [sup 17]O NMR spectra and demonstrates the wealth of information which is available from NMR studies of solid materials. [ABSTRACT FROM AUTHOR]

Examines the structure of silver cyanide by solid-state multinuclear magnetic resonance spectroscopy. Linearity of polymeric chains; Domination of two-site model by indirect nuclear spin-spin coupling between [sup 109/107]Ag and [sup 12]C nuclei; Application of the zeroth-order regular approximation density functional theory calculation.

Examines the nuclear spin-spin coupling tensors for polyatomic xenon fluorides and group 17 fluorides. Reduction of coupling constants for halogen-noble gas spin pairs; Use of zeroth-order regular approximation density-functional theory method in interpreting spin-spin coupling of polyatomic systems; Mechanisms of chlorine-fluorine isotropic coupling constants.

Borinium cations (R2B+) are of particular fundamental and applied interest in part due to their pronounced Lewis acidity which enables unique chemical transformations. Solid-state NMR spectroscopy of magic-angle spinning and stationary powdered samples of the dicoordinate boron cation in the recently reported dimesitylborinium tetrakis(pentafluorophenyl)borate compound (Shoji et al. Nature Chem. 2014, 6, 498) is applied to characterize the 11B electric field gradient (EFG) and chemical shift (CS) tensors. The experimental data are consistent with linear C--B+--C geometry. The 11B quadrupolar coupling constant, 5.44 ± 0.08 MHz, and the span of the CS tensor, 130 ± 1 ppm, are both particularly large relative to literature data for a variety of boron functional groups, and represent the first such data for the linear C--B+--C borinium moiety. The NMR data are similar to those for the neutral tricoordinate analogue, trimesitylborane, but contrast with those of the Cp*2B+ cation. Quantum chemical calculations are applied to provide additional insights into the relationship between the NMR observables and the molecular and electronic structure of the dimesitylborinium cation. [ABSTRACT FROM AUTHOR]

A series of calcium and strontium complexes featuring aryl carboxylate ligands has been prepared and characterized by alkaline-earth (43Ca and 87Sr) solid-state NMR experiments in a magnetic field of 21.1 T. In the 11 compounds studied as part of this work, a range of coordination motifs are observed including nitrogen atom binding to Ca2+ and Sr2+, a binding mode which has not been investigated previously by 43Ca or 87Sr solid-state NMR. 43Ca isotopic enrichment has enabled the full characterization of the 43Ca electric field gradient (EFG) and chemical shift tensors of the two calcium sites in calcium p-aminosalicylate (Ca(pams)), where both NMR interactions are affected by the presence of a nitrogen atom in the first coordination sphere of one of the metal sites. The 43Ca isotropic chemical shift is sensitive to the Ca-N distance as exemplified by the NMR parameters of a second form of Ca(pams) and density functional theory (DFT) calculations. Studies of the strontium analogue, Sr(pams), confirm a similar sensitivity of the 87Sr EFG tensor to the presence or absence of nitrogen in the first coordination sphere. To our knowledge, this is the first systematic 87Sr NMR study of strontium complexes featuring organic ligands. The |CQ(87Sr)| values are found to be sensitive to the coordination number about Sr2+. In general, this work has also established a larger data set of reliable experimental |CQ(43Ca)| values which correlate well with those obtained using gauge-including projector-augmented-wave (GIPAW) DFT calculations. It is found that the use of a recently recommended quadrupole moment for 43Ca, -44.4 mbarn, improves the agreement with experimental values. This contribution lays the groundwork for the interpretation of 43Ca and 87Sr NMR spectra of more challenging systems, particularly where nitrogen-alkaline earth metal bonding is occurring. [ABSTRACT FROM AUTHOR]