cis- and trans-Dichloro chelate complexes of niobium(IV): synthesis and structure of trans-dichloro[NN′-ethylenebis(acetylacetonylideneiminato)-(2–)]niobium(IV) and cis-dichloro{7,16-dihydro-6,8,15,17-tetramethyldibenzo-[b,i][1,4,8,11]tetra-azacyclotetradecinato(2–)}niobium(IV)–acetonitrile (1/2)
- 1 January 1988
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 5,p. 1361-1365
- https://doi.org/10.1039/dt9880001361
Abstract
The reaction of the sodium or potassium salts of H2acen [H2acen =NN-ethylenebis(acetylacetonylideneimine)] with NbCl4·2thf (thf = tetrahydrofuran) led to trans-[Nb(acen)Cl2](1), while reaction with the lithium salt of H2L (H2L = 7,16-dihydro-6,8,15,17-tetramethydibenzo-[b,i][1,4,8,11]tetra-azacyclotetradecine) gave cis-[Nb(L)Cl2](2). Both compounds are paramagnetic [µeff˙= 1.80 at 292 K (1), 1.94 B.M. at 293 K (2)] and contain a single unpaired electron. The structures of (1) and (2) have been established by X-ray diffraction methods. In complex (1), the acen ligand displays the usual square-planar geometry and the two chlorine atoms are trans[Cl–Nb–Cl, 178.5(1) and 178.6(1)° for the two independent molecules in the structure]. In complex (2) the macrocycle L has the usual saddle-shaped conformation with the two chlorines cis[Cl–Nb–Cl, 81.8(1)°]. Regardless of the isomeric arrangement the Nb–Cl distances are very close in the two complexes [Nb–Cl(av.), 2.434(4)(1); 2.452(2)(2)Å].Keywords
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