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Theoretical investigations of NMR chemical shifts and reactivities of oxovanadium(v) compounds
Author(s) -
Bühl Michael,
Hamprecht Fred A.
Publication year - 1998
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(19980130)19:2<113::aid-jcc3>3.0.co;2-x
Subject(s) - chemistry , chemical shift , density functional theory , vanadium , alkyl , adduct , olefin fiber , aryl , transition metal , catalysis , transition state , coordination number , computational chemistry , crystallography , medicinal chemistry , organic chemistry , ion
Employing gradient‐corrected levels of density‐functional theory (DFT), medium‐sized basis sets, and optimized geometries, chemical shifts are calculated for [VOCl n F 3− n ] ( n =0–3), VF 5 , [VO(OCH 2 CH 2 ) 3 N], [V(CO) 6 ] − , [V(CO) 5 (N 2 )] − , as well as for the model compounds [VO(OMe) n Me 3− n ] ( n =0–3) and their AlH 3 adducts. Experimental trends in δ( 51 V) are well reproduced with DFT‐based methods; for example, the slopes of the δ( 51 V) calc vs. δ( 51 V) expt linear regression lines are 0.92 and 1.03 at the GIAO‐BP86 and GIAO‐B3LYP levels, respectively. Ethylene polymerization observed with [V(O⋅⋅⋅AlX 3 )(OR) n R′ 3− n ] ( X , R , R ′=bulky alkyl, aryl, or silyl groups) is shown for model systems ( X =H, R = R ′=Me) to proceed by insertion of the olefin into a V—C bond via a transition state with approximate square‐pyramidal coordination about vanadium. For the tri‐ and dialkyl derivatives ( n =0, 1), similar activation barriers of ca. 19 kcal/mol are computed (BP86 level including zero‐point energies), whereas that of the monoalkyl species ( n =2) is predicted to be much higher, ca. 30 kcal/mol. The relevance of these results for the apparent relationship between δ( 51 V) and catalytic activities is discussed. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 113–122, 1998