Multinuclear solid-state magnetic resonance study of oxo-bridged diniobium and quadruply-bonded dimolybdenum carboxylate clusters

作者：Kobera Libor; Southern Scott A; Frost Jamie M; Bryce David L^*

来源：Solid State Nuclear Magnetic Resonance, 2017, 84: 20-27.

DOI：10.1016/j.ssnmr.2016.12.001

• Niobium
• Molybdenum
• Paddlewheel
• Quadruple bond
• Nb-93
• Mo-95
• Solid-state NMR

Carboxylate paddlewheels and their oxo-bridged analogues constitute ideal building blocks for the assembly of two- and three-dimensional framework materials. Here, we present a multinuclear (H-1, C-15, Nb-93, Mo-95) magnetic resonance study of solid samples of Nb2OCl6(O-2 PH)(2) (1), Mo-2(O2CMe)(4) (2), and Mo-2(O2CCHF2)(4) (3). High-resolution proton and C-13 CP/MAS NMR spectra provide valuable information on structure and crystal symmetry and on cocrystallized solvent. Nb-93 solid-state NMR spectra of 1 provide quadrupolar coupling constants and chemical shift tensors which are characteristic of the axially asymmetric Nb-O-Nb bridging environment. Mo-95 solid-state NMR spectra of 2 and 3 provide quadrupolar coupling constants and chemical shift tensors which are directly characteristic of the molybdenum-molybdenum quadruple bonds in these compounds. The quadruple bonds are characterized by particularly large Mo-95 chemical shift tensor spans on the order of 5500 ppm. Density functional theoretical computations provide good agreement with the Nb-93 and Mo-95 experimental data, with some exceptions noted. This work demonstrates possible NMR approaches to characterize more complex framework materials and provides key insight into the Mo-Mo quadruple bond.

• 出版日期2017-8