NDLI: Solvent and metal dependent $^{1}H$ NMR hyperfine shifts in paramagnetic pentaamminemetal cyanide-bridged mixed-valence complexes

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Thompson, Amber L. Laidlaw, William Michael Denning, Robert Gordon
Description	Author Affiliation: Laidlaw WM ( Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK. michael.laidlaw@chem.ac.uk)
Abstract	$^{1}$ H NMR resonances, in several aprotic solvents, are reported for axial and equatorial ammonias coordinated to a single spin paramagnetic centre in the Robin-Day Class II cyanide-bridged mixed-valence cations $[(OC)_{5}Cr(μ-CN)M(NH_{3})_{5}]^{2+}$ (M = Ru, Os) as well as in the complex $[(OC)_{5}Re(μ-CN)Ru(NH_{3})_{5}]^{3+},$ whose synthesis and properties are reported herein. Using the appropriate isotropic hexaammine complex as a reference, the chemical shift difference between the ammonia protons, $δ_{ax}$ − $δ_{eq},$ is found to be very sensitive to the paramagnetic metal (M), the remote diamagnetic metal (Cr or Re) and also to the donor properties of the solvent (as well as the counter-ion) as a result of hydrogen bonding interactions. The difference varies linearly with the MMCT energy, and in $[(OC)_{5}Re(μ-CN)Ru(NH_{3})_{5}]^{3+}$ can be tuned from positive $(δ_{ax}$ > $δ_{eq})$ to negative $(δ_{ax}$ < $δ_{eq})$ through zero $(δ_{ax}$ = $δ_{eq})$ by the choice of solvent. This reflects the sign and magnitude of the axial ligand field parameter which is in turn a result of changes in the π-donor–acceptor interactions between the donor-cyanide bridging group and the pentaammine metal unit.
ISSN	14779226
Issue Number	13
Journal	Dalton Trans.
Volume Number	42
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2013-04-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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