Matthews, Karen D.,; Kahwa, Ishenkumba, A.; Johnson, Marie P.; Mague, Joel T.; McPherson, Gary L.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Lanthanide tetramethoxyborate complexes isolated from reductive amination of 2,6-diformyl-p-cresol
Date of Publication
Treatment of a hot methanolic solution of 2,6-diformyl-p-cresol (1 mmol), 3,6-dioxa-1, 8-octanediamine (2 mmol), and a lanthanide (III) nitrate (1 mmol) with sodium cyanotrihydroborate (1.5 mmol) unexpectedly yields a mixture of isostructural but totally different compounds. [Ln(B(OCH3)4)(NO3)2(CH3OH)2], and an asymmetric Schiff base complex, Ln25(NO3)4·1.2CH3OH. The lanthanum complex of the B(OCH3)4-anion crystallizes in the monoclinic system, C2/c, with a = 16.50(6) Å, b = 6.5(2) Å, c = 15.84 (6) Å, b = 106.8(1)°, V = 1621 (2) Å3, and Z = 4. With 1566 unique and 1374 observed (I>3s(I) data and 101 variables, R=0.017 and Rw =0.025. The structure features an assembly of [La(B(OCH3)4)(NO3)2(CH3OH)2]n chains in which La3+ ions are bridged by bidentate B(OCH3)4-anions which are distorted noticeably from Td symmetry. The shortest La-O distances in the C2v 10-fold 4A,6B-extended dodecahedral coordination polyhedron (two bidentate NO3-, two methanol molecules, and two bidentate B(OCH3)4-) involve the two B(OCH3)4-anions. The B(OCH3)4-anions form strong bonds with Ln3+ cations and can achieve the geometrical distortions required for constituting the irregular Ln3+ coordination polyhedra. As good competitors for Ln3+ cations, B(OCH3)4- anions can be expected to have destabilizing effects on Schiff base chelates which depend on coordination to Ln3+ cations to achieve stability. The structure of the Pr25(NO3)4·1.2CH3OH complex is reported elsewhere....