Paramagnetic Bis(1,4-di-tert-butyl-1,4-diazabutadiene) Adducts of Lithium, Magnesium, and Zinc

Michael G. Gardiner, Graeme R. Hanson, Mark J. Henderson, Fu Chin Lee, Colin L. Raston

Research output: Contribution to journalArticlepeer-review

130 Citations (Scopus)

Abstract

Treatments of activated magnesium and zinc, M*, in THF and of sonified bulk lithium in hexane with 1,4-ditert-butyl-1,4-diazabutadiene (But2DAB) afford [M(But2DAB)2] as triplet, ligand-centered biradicals in the solid state and at low temperature in solution (M = Mg (1) (previously studied using EPR), Zn (2)) or a ligand-centered radical (M= Li (3) (gav = 2.0034 in hexane, a(14N×2) = 4.66 × 10-4cm-1, a(1H×2) = 4.90 × 10-4 cm-1, a(7Li) = 1.36 × 10-4cm-1)). Reaction of M*/MH2 with But2DAB in THF also gives 1 and 2, as do the reactions of MgCl2 and ZnCl2 with 3, and the reaction of 1 with ZnCl2 affords 2. The room-temperature EPR spectrum of 2 displays two signals attributed to cation/anion ligand-centered radicals, [M(But2DAB)2]+[M(But2DAB)2]- (gav (1) = 2.0068,(14N×2) = 4.66 ×10-4 cm-1, a(1H×2) = 6.23 × 10-4 cm-1,gav(2) = 2.0077, a(14N×2) = 4.66 × 10-4 cm-1, a(1H×2) = 6.23 X 10-4 cm-1). At low temperature a dipole-dipole-coupled spectrum is observed, affording a distance of 4.75 Å between the electrons each centered on a But2DAB ligand. In the solid state 1 and 2 have mm crystallographic symmetry, with mainly angular distortions from regular tetrahedral geometry at the metal centers, M-N = 2.070(7), 2.067(7) Å, (1), 1.999(4), 2.013(4) Å, (2), N-M-N = 82.1(3), 82.4(3)° (1), 84.8(2), 84.7(2)° (2), whereas 3 has angular and bond distance tetrahedral distortions, in accordance with the metal center being bound by a radical anion bidentate ligand, Li-N(mean) = 1.995 Å (N-Li-N = 88.3(3)°), and a neutral bidentate ligand, Li-N(mean) = 2.141 Å (N-Li-N = 79.5(2)°). Crystal data (Mo Kα, λ= 0.710 69 Å): 1, orthorhombic, space group Ibmm, a = 12.063(1) Å, b = 14.266(2) Å, c = 14.252(3) Å, V = 2452.8(7) Å3, Z = 4, R = 0.051; 2, orthorhombic, space group Ccmm, a = 12.388(3) Å, b = 14.225(3) Å, c = 13.705(1) Å, V = 2415.2(8) Å3, Z = 4, R = 0.036; 3, monoclinic, space group P21/c, a = 11.671(7) Å, b = 10.598(1) Å, c = 20.026(1) Å, β = 104.60(3)°, V = 2397(2) Å3, Z = 4, R = 0.056.

Original languageEnglish
Pages (from-to)2456-2461
Number of pages6
JournalInorganic Chemistry
Volume33
Issue number11
DOIs
Publication statusPublished - 1 May 1994
Externally publishedYes

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