Structure of {2,3,5,6-tetrakis[(dimethylamino)methyl]phenyl-C,N,N'}lithium dimer

Abstract

C36H66Li2Ns, Li2(CIsH33N4)2, Mr= 624.85, orthorhombic, Ccca, a = 14.432 (3), b = 19.697 (2), c = 1 4 . 7 3 9 ( 1 ) A , V = 4 1 9 0 ( 1 ) A 3, Z 4 , D x= 0 .990gcm -3, MoKa, 2 = 0 . 7 1 0 7 3 A , g = 0 . 6 c m -~, F(000) = 1376, T = 294 K, R = 0.0550 for 1256 observed reflections with I > 2ix(I). The crystal structure consists of four dimeric molecules in the orthorhombic unit cell with no significant short intermolecular contact; the molecules have crystallographic 222 site symmetry. The Li atom is pseudo-tetrahedrally coordinated by two N(1) atoms [2.109 (3)A] and by two C(1) atoms [2.209 (3) A]. Experimental. Colourless rod-shaped crystal 1.0 × 0.33 × 0 .33mm mounted under nitrogen in a Lindemann-glass capillary. Unit-cell parameters and their e.s.d.'s derived from a least-squares treatment of 12 reflections (9.3 2o(1) (McCandlish, Stout & Andrews, 1975). Space group Ccca derived from the systematic absences: hkl: h + k = 2 n + l; Okl: k, l=2n+ l; hOl: h, l = 2n + 1; hk0: h, k = 2n + 1. Structure solved by direct methods (SHELXS86; Sheldrick, 1986), the solution with the best figure of merit revealed all non-H atoms with the exception of Li. The position of the Li atom was determined from a subsequent difference Fourier synthesis. All non-H atoms refined with anisotropic thermal parameters by full-matrix least* Author to whom correspondence should be addressed. 0108-2701/87/071429-02501.50 squares techniques, minimizing ~wAF 2, using the SHELX76 package (Sheldrick, 1976). All H atoms except H(4) were introduced on calculated positions ( C H = 0.98 A) and refined riding on their corresponding C atoms, with one overall isotropic thermal parameter. H(4) was located from a difference Fourier synthesis and refined according to its special position with the same isotropic thermal parameter. At the final stage of the refinement, weights were introduced resulting in R = 0.0550, wR =0.0405, S = 2.64, w =l/tr2(F). Max. A/o=O.17. A final difference Fourier map revealed residual densities between 0.18 and 0 . 1 6 e A -3. The crystal exhibited some secondary extinction for which the F c values were corrected by refinement of an empirical isotropic extinction parameter X[= 3.0 (6) x 10-8]: F c' =Fc[ 1--(XF2/sin0)]. Scattering factors were taken from Cromer & Mann (1968). All calculations were carried out in the CDC Cyber-855 of the University of Utrecht Computer Center with the programs mentioned above and with the EUCLID package (Spek, 1982; molecular geometry and illustrations).