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183 W NMR study of alkenylcarbyne– and alkenylvinylidene–tungsten complexes
Author(s) -
Carbajo Rodrigo J.,
Zhang Lei,
LópezOrtiz Fernando
Publication year - 1998
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/(sici)1097-458x(1998110)36:11<807::aid-omr368>3.0.co;2-z
Subject(s) - chemistry , crystallography , substituent , chemical shift , halogen , acceptor , nmr spectra database , denticity , metal , proton nmr , stereochemistry , spectral line , crystal structure , organic chemistry , alkyl , physics , astronomy , condensed matter physics
183 W NMR data are reported for a series ofalkenylvinylidene– and alkenylcarbyne–tungsten complexesof the type [(dppe)(CO) 3 WCCHR],[(dppe)(CO) 3 WC−CHCR 2 ] + BF 4 ‐ and [(dppe)(CO) 2 LWC−CHCR 2 ][dppe=1,2‐bis(diphenylphosphino)ethane]. Spectra were recorded usinginverse 2D 1 H, 183 W‐ and 31 P, 183 W{ 1 H}‐HMQC NMRspectroscopy without 183 W decoupling. In some examples ofthe alkenylcarbyne series minor amounts of the propenylcarbyne isomerwere present and the corresponding 183 W chemical shiftscould also be characterized. For a given complex and measuring timethe proton‐detected correlation spectra based on the existinglong‐range coupling to the metal affords a higher signal‐to‐noiseratio than the phosphorus‐detected correlation via 1 J ( 183 W, 31 P). Additionally,the tilt of cross peaks in the 1 H, 183 W HMQCspectra reveals the relative sign of the coupling of these nuclei withphosphorus. 183 W chemical shift variations for compounds[(dppe)(CO) 2 LWC−CHCR 2 ](L=CO, PMe 3 , CH 3 CN or halogen) are rationalizedin terms of the π‐acceptor ability of the ligand. Halogenderivatives show shielding decreases in the order F