ic991415s_si_001.cif (129.77 kB)

Vanadium(IV) and -(V) Complexes with O,N-Chelating Aminophenolate and Pyridylalkoxide Ligands

Download (129.77 kB)
dataset
posted on 11.08.2000 by Henk Hagen, Chris Bezemer, Jaap Boersma, Huub Kooijman, Martin Lutz, Anthony L. Spek, Gerard van Koten
Two different monoanionic O,N-chelating ligand systems, i.e., [OC6H2(CH2NMe2)-2-Me2-4,6]- (1) and [OCMe2([2]-Py)]- (2), have been applied in the synthesis of vanadium(V) complexes. The tertiary amine functionality in 1 caused reduction of the vanadium nucleus to the 4+ oxidation state with either [VOCl3], [V(NR)Cl3], or [V(NR)(NEt2)3] (R = Ph, (3a, 5a), R = p-Tol (3b, 5b)), and applying 1 as a reducing agent resulted in the synthesis of the vanadium(IV) complexes [VO(OC6H2(CH2NMe2)-2-Me2-4,6)2] (4) and [V(NPh)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (6). In the case of [V(N-p-Tol)(NEt2)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (7b), the reduction was sufficiently slow to allow its characterization by 1H NMR and variable-temperature studies showed it to be a five-coordinate species in solution. Although the reaction of 1 with [V(N-p-Tol)(O-i-Pr)3] (9b) did not result in reduction of the vanadium nucleus, vanadium(V) compounds could not be isolated. Mixtures of the vanadium(V) (mono)phenolate, [V(N-p-Tol)(O-i-Pr)2(OC6H2(CH2NMe2)-2-Me2-4,6)] (10), and the vanadium(V) (bis)phenolate, [V(N-p-Tol)(O-i-Pr)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (11), were obtained. With the pyridylalkoxide 2, no reduction was observed and the vanadium(V) compounds [VOCl2(OCMe2([2]-Py))] (12) and [V(N-p-Tol)Cl2(OCMe2([2]-Py)] (13) were obtained. 51V NMR showed 7b and 12 to be five-coordinate in solution, whereas for 10, 11, and 13 a coordination number of 6 was found. Compounds 12 and 13 showed decreased activity compared to their nonchelated vanadium(V) analogues when applied as catalysts in ethene polymerization. Two polymorphic forms with a difference in the V−N−C angle of 12.5° have been found for 6. Crystal data:  6·Et2O, triclinic, P1̄, a = 11.1557(6) Å, b = 12.5744(12) Å, c = 13.1051(14) Å, α = 64.244(8)°, β = 70.472(7)°, γ = 87.950(6)°, V = 1547(3) Å3, Z = 2; 6·C6H6, triclinic, P1̄, a = 8.6034(3) Å, b = 13.3614(4) Å, c = 15.1044(5) Å, α = 98.182(3)°, β = 105.618(2)°, γ = 107.130(2)°, V = 1551.00(10) Å3, Z = 2; 12, orthorhombic, Pbca, a = 11.8576(12) Å, b = 12.6710(13) Å, c = 14.722(2) Å, V = 2211.9(4) Å3, Z = 8.

History

Exports