RAMAIYER VENKATRAMAN et al. 1243 Refinement Refinement on F 2 R[F 2 > 2or(F2)] = 0.042 wR(F2) = 0.101 S = 0.744 6942 reflections 524 parameters H atoms treated by a mixture of independent and constrained refinement w = 1/[cr2(Fo 2) + (0.0543P) 2] where P = (F3 + 2F~2)/3 (m/O')max = 0.001 Apmax = 0.54 e .~-3 Apmin = -0.61 e ,~-3 Extinction correction: SHELXL97 Extinction coefficient: 0.0060 (5) Scattering factors from International Tables for Crystallography (Vol. C) Absolute structure: Flack (1983) Flack parameter = -0.023 (13) Table 1. Selected geometric parameters (it, o) Cul--OI 1.918(3) Cu2---O3 1.941 (3) CuI--N3 2.004 (4) Cu2--N5 1.992 (4) Cu I--N2 2.020 (4) Cu2--N6 1.997 (4) CuI--NI 2.033 (4) Cu2--N4 2.031 (4) Cul---OI W 2.234 (4) Cu2---O2W 2.382 (3) CI6---N3----CI3---C14 8.5 (7) C33--N6--C30---C31 38.0 (5) N3---CI 3---C14----C 15 -29.2 (8) N6---C30--C31---C32 -40.2 (5) C13--C14----C15---C16 38.3 (9) C30--C31---C32---C33 27.0 (5) C13--N3---C16---C15 15.3 (5) C30---N6---C33---C32 -20.6 (5) CI4---C15---C16---N3 -32.8 (7) C31---C32--C33--N6 -4.2 (5) The absolute structure was determined from the known absolute configuration of one of the ligands (L-proline) in the complex. The Flack (1983) parameter was refined without Friedel data. In the development of the molecular model from X-ray data, H atoms were located in difference Fourier maps and included in the model at calculated positions and allowed to refine using a riding model, except for the water H atoms (on O4W), which could not be found. U~so values for H atoms were assigned values 120% of the Ueq values of the attached non-H atoms or 150% in the case of water H atoms. Data collection: P3 Software (Siemens, 1989). Cell refine- ment: P3 Software. Data reduction: XDISK in P3 Software. Program(s) used to solve structure: SHELXS93 (Sheldrick, 1993). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997). Molecular graphics: XP in P3 Soft- ware. Software used to prepare material for publication: SHELXL97. We thank the Office of Naval Research for support of instrumentation (EJV and JDZ) and the National Science Foundation (DUE-9250769). Supplementary data for this paper are available from the IUCr electronic archives (Reference: FR1195). Services for accessing these data arc describcd at the back of the journal. References Antolini, L., Battaglia, L. P., Corradi, A. B., Marcotrigiano, G., Menabue, L., Pellacani, G. C., Saladini, M. & Sola, M. (1986). lnorg. Chem. 25, 2901-2904. Antolini, L., Marcotrigiano, G., Menabue, L. & Pellacani, G. C. (1983). lnorg. Chem. 22, 141-145. Antolini, L., Marcotrigiano, G., Menabue, L., Pellacani, G. C., Saladini, M. & Sola, M. (1985). Inorg. Chem. 24, 3621-3626. Balasubramanian, R., Lakshminarayanan, A. V., Sebesan, M. N., Tegoni, G., Venkatesan, K. & Ramachandran, G. N. (1971). Int. J. Protein Res. 3, 25-33. Baran, E. J. (1995). In Quimica Bioinorganica. Madrid: McGraw- Hill/Interamericana de Espana. Fischer, B. E. & Sigel, H. (1980). J. Am. Chem. Soc. 102, 2998-3008. Flack, H. D. (1983). Acta Cryst. A39, 876-881. Garcia-Raso, A., Fiol, J. J., Adrover, B., Moreno, V., Molins, E. & Mata, I. (1998). J. Chem. Soc. Dalton Trans. pp. 1031-1036. Griesser, R. & Sigel, H. (1970). lnorg. Chem. 9, 1238-1243. IUPAC-IUB Commission on Biochemical Nomenclature (1970). J. Mol. Biol. 52, 1-17. Kwik, W. L., Ang, K. P. & Chen, G. (1980). J. Inorg. Nucl. Chem. 42, 303-313. Sabat, M. (1996). Metal Ions in Biological Systems, Vol. 32, edited by A. Sigel & H. Sigel. New York and Basel: Marcel Dekker. Sheldrick, G. M. (1993). SHELXS93. Program for the Solution of Crystal Structures. University of Grttingen, Germany. Sheldrick, G. M. (1997). SHELXL97. Program for the Refinement of Crystal Structures. University of G6ningen, Germany. Siemens (1989). P3 Software. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. Szalda, D. J. & Kistenmacher, T. J. (1977). Acta Cryst. B33, 865-869. Acta Cryst. (1999). C55, 1243-1246 [Cu2{1,4-bis[(3-methyl-2-pyridyl)amino]- phthalazine-H}(N3)3] at 40 K ANDRES E. GOETA, a LAURENCE K. THOMPSON, b CHRISTOPHER L. SHEPPARD, b SANTOKH S. TANDON, b CHRISTIAN W . LEHMANN,a~" JOHN COSIER, c CRAIG WEBSTER c AND JUDITH A. K. HOWARDa aDepartment of Chemistry, Durham University, Durham DH1 3LE, England, bDepartment of Chemistry, Memorial University of Newfoundland, St Johns, Newfoundland, Canada AIB 3X7, and COxford Cryosystems, 3 Blenheim Office Park, Lower Road, Long Hanborough, Oxford OX8 8LN, England. E-mail: a.e.goeta@durham.ac.uk (Received 21 December 1998; accepted 21 April 1999) Abstract The structure of the title compound, #-azido-l:2tc2Nl-[~ - 4-(3-methyl-2-pyridyl-2JcN-amino)- 1-(3-methyl-2-pyridyl- 1 tcN-imino)- 1,2-dihydrophthalazin- 2-yl- 1 : 2e;2N2 :N 3 ]- bis[(azido-~N l)copper(II)], [Cu2(C20HI7N6)(N3)3], (I), determined from data recorded at 40(1)K using a new open-flow He gas cryostat, is presented here as part of an extended study program on dicopper(II) azide-bridged compounds. Each pair of Cu II centres in (I) is equatorially bridged by a #2-1,1-azide, with a bridge angle of 107.2 (1) °. The dinuclear centres form tetranuclear clusters through two #2-1,3-azide bridges, which in turn form chains along the a axis. Two C-- t Current Address: Max-Planck-lnstitut fiir Kohlenforschung, Kaiser- Wilhelm-Platz 1, 45470-Mtilheim an der Ruhr, Germany. © 1999 International Union of Crystallography Printed in Great Britain - all rights reserved Acta Crystallographica Section C ISSN 0108-2701 © 1999