Bis(2‐amino‐1,1‐dimethylethanethiolato‐N,S)zinc

Zn[SC(CHa)2CH2NH2]2, orthorhombic, C2221, a = 5.5755 (7), b = 10.585 (1), c = 21.741 (3) A, Z = 4, D o = 1.41 (1), D c = 1.417 g c m -3. The structure consists of discrete Zn[SC(CH3)ECHENHz] z molecules with point symmetry 2. Each Zn atom is ligated by two N and two S atoms which yield a distorted tetrahedral coordination geometry. The Z n S and Zn--N bond lengths are 2.297 (4) and 2.06 (1) A, respectively, while L-Zn-L ' angles within the coordination polyhedron range from 91-5 (3) to 137.1 (2) °. Introduction. Colorless, slightly elongated six-sided plates of the title complex were prepared as described previously (Mastropaolo, Thich, Potenza & Schugar, 1977). A single crystal of dimensions 0.68 x 0.39 x 0.075 mm, mounted on a glass fiber, was used. Weissenberg photographs showed systematic absences for hkl, h + k = 2n + 1 and 00l, l = 2n + 1 along with mmm reciprocal-lattice symmetry, fixing the space group as C222 r Assuming four molecules per unit cell, the observed (flotation) and calculated densities agreed well. Data were collected at 20 + 2°C with a CAD-3 automated diffractometer ( 0 2 0 scan) using graphitemonochromated Mo Ka radiation (2 = 0.71069 A). Of the 934 intensities recorded (4 < 20 < 50°), 562 with F 2 > 30(F 2) were considered observed, corrected for Lp and absorption effects (/~ = 22.3 cm -1 for Mo Ka radiation), and used in the refinement. Inspection of the data showed that the title complex and the recently characterized Co n analog (Mastropaolo, Thich, Potenza & Schugar, 1977)were isostructural. Refinement of the non-hydrogen atoms was initiated using atomic coordinates from the Co ~I complex. Neutral atom scattering factors and anomalous dispersion corrections for Zn and S were obtained from International Tables for X-ray Crystallography (1974). At a later stage, H atoms were included in the refinement with fixed isotropic temperature factors equal to those of the heavy atoms to which they are bonded; trial coordinates for the CH 2 and NH 2 protons were calculated, while those for the methyl groups were obtained from the Co n complex. Refinement was based on F and a weighting scheme [w = 1/a2(F)] was chosen by an analysis of variance (Ricci, Eggers & Bernal, 1972) to make IAFI/a independent of I Fol. This led to the following assignments: a(Fo) = 3.52 0.0311Fol, IFol < 43.7; a(Fo) = 1-07 + 0.0251Fol, IFol > 43.7. Full-matrix leastsquares refinement of all non-hydrogen atomic coordinates and anisotropic thermal parameters gave final values of R F ----~ IIFol IFcll/~ IFol = 0.063 and Rwv Table 1. Final atomic coordinates Estimated standard deviations, obtained from the least-squares refinement, are given in parentheses.