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Synthesis and Reactivity of Ene‐Diamido and Ene‐Diolato [(Trimethylsilyl)cyclopentadienyl]niobium(V) Complexes and a Comparative DFT Study of the Bonding Capabilities of Diazabutadiene and Butadiene Ligands
Author(s) -
Galindo Agustín,
Gómez Manuel,
Río Diego del,
Sánchez Fernando
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200206)2002:6<1326::aid-ejic1326>3.0.co;2-t
Subject(s) - chemistry , cyclopentadienyl complex , trimethylsilyl , ene reaction , ligand (biochemistry) , moiety , medicinal chemistry , triple bond , stereochemistry , nuclear magnetic resonance spectroscopy , double bond , organic chemistry , catalysis , biochemistry , receptor
The reactions of [NbCp′Cl 2 (Me 3 SiCCSiMe 3 )] (Cp′ = η 5 ‐C 5 H 4 SiMe 3 ) with 2,3‐dimethyl‐1,4‐diphenyl‐1,4‐diazabuta‐1,3‐diene (Me,Ph‐DAD) and diketones R−CO−CO−R (R = Me, Ph) gave ene‐diamido complexes [NbCp′Cl 2 (Me,Ph‐DAD)] ( 1 ) and ene‐diolato complexes [NbCp′Cl 2 {O(R)CC(R)O}] (R = Me, 2 ; Ph, 3 ), respectively, with simultaneous elimination of bis(trimethylsilyl)acetylene. The NMR spectroscopic data of these compounds are in agreement with a supine conformation, with respect to the Cp′ ring, of the ene‐diamido and ene‐diolato ligands. In order to gain further information concerning the bonding capabilities of the ene‐diamido ligand, a DFT study of the model complex [NbCpCl 2 (HNCHCHNH)] ( I ) was performed. For comparison, a DFT analysis of the model compound [NbCpCl 2 (η 4 ‐CH 2 CHCHCH 2 )] ( II ) was also carried out. Differences in the bonding description of the diazabutadiene and butadiene ligands bonded to a common [NbCpCl 2 ] moiety are discussed. A detailed analysis of the fragment orbital interactions in I provides no evidence for any positive overlap between the Nb centre and the inner carbon atoms of the DAD ligand. Dialkylation of the dichloro complex 1 gave dialkyl derivatives [NbCp′R 2 (Me,Ph‐DAD)] (R = Me, 4 ; CH 2 SiMe 3 , 5 ; CH 2 C 6 H 5 , 6 ), for which the NMR spectroscopic data suggests a prone conformation of the DAD ligand. Treatment of the dimethyl derivative 4 with carbon monoxide and 2,6‐dimethylphenyl isocyanide led to the formation of the oxa‐ and azaniobacyclopropane complexes [NbCp′{η 2 ‐(E)CMe 2 }(Me,Ph‐DAD)] [E = O, 7 ; N(2,6‐Me 2 C 6 H 3 ), 8 ], respectively. Subsequent insertion of isocyanide into the Nb−C bond of 7 proceeds with formation of derivatives [NbCp′{η 2 ‐(O)CMe 2 ‐(CNAr) x }(Me,Ph‐DAD)], (Ar = 2,6‐Me 2 C 6 H 3 ; x = 1, 9 ; 2, 10 ). All the complexes isolated were characterized by IR and NMR ( 1 H, 13 C{ 1 H}) spectroscopy. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)