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Multinuclear magnetic resonance study of some imidovanadium complexes
Author(s) -
Gudat Dietrich,
Fischbeck Uwe,
Tabellion Frank,
Billen Martin,
Preuss Fritz
Publication year - 2002
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.978
Subject(s) - chemistry , phosphine , vanadium , chemical shift , substituent , ligand (biochemistry) , amine gas treating , nuclear magnetic resonance spectroscopy , stereochemistry , denticity , crystallography , crystal structure , inorganic chemistry , organic chemistry , receptor , biochemistry , catalysis
14 N NMR studies were carried out for a series of mononuclear and dinuclear vanadium complexes with different types of nitrogen ligands (terminal and µ‐imido, amido, nitrido, amine). Some complexes containing ancillary phosphine moieties were also characterized by 31 P NMR spectroscopy. The observed shieldings for terminal and bridging imido ligands are intermediate between those of nitrido and amido moieties, and the latter appear less shielded than coordinated tertiary amines. The ranges for individual ligand types are sufficiently resolved to allow the use of nitrogen chemical shifts as a structure assignment tool. The 14 N NMR signals of terminal and bridging imido nitrogens displayed marked differences in their lineshapes which could be used as an additional criterion for signal assignment. Examination of substituent influences revealed the absence of a general parallelism between δ 14 N and δ 51 V, but gave evidence for parallel relationships between both quantities for complexes with formal 12VE and 16VE electron counts. Determination of 1 J ( 51 V, 14 N) and 1 J ( 51 V, 31 P) coupling constants in mononuclear complexes was feasible from simulation of 14 N and 31 P lineshapes and suggested that imido ligands exhibit generally greater couplings to vanadium than amido ligands. Analysis of the 31 P { 1 H, 14 N} NMR spectrum allowed us to determine 2 J ( 51 V, 31 P) for the vanadacycle cyclo( t BuN—PC( t Bu)—VCl 3 —). It was shown that both couplings can be employed for the acquisition of two‐dimensional 31 P, 51 V shift correlations. Copyright © 2001 John Wiley & Sons, Ltd.