Re-investigating the structures of [Cu(NO3)2(en)2] and [Cu(NO3)2(pn)2]: tales of twinning and a reversible phase chang

C.L. Carpenter-Warren (7162505)

Mark Elsegood (1249893)

Muhammet Kose (558529)

English

Loughborough University Institutional Repository

M.R.J. Elsegood, C.L. Carpenter-Warren, M. Kose. Re-investigating the structures of [Cu(NO3)2(en)2] and [Cu(NO3)2(pn)2]; Tales of twinning and a reversible phase change. The structure of trans-bis(1,2-diaminoethane)-dinitrato-copper(II), [Cu(NO3)2(en)2], has been reported twice previously,1 including once as a private deposition to the CSD. On both occasions the data were collected at room temperature with a 4-circle serial diffractometer and the R factors at ca. 4% suggest there is little more to understand. Our recent re-determination at low temperature on a CCD area detector system revealed a twinned diffraction pattern. We will describe the handling of the twinning and hence a halving of the R factor. The structure of trans-bis(1,2-diaminopropane)-dinitrato-copper(II), [Cu(NO3)2(pn)2], has also been reported twice previously.2,3 As above, both determinations were at room temperature on serial diffractometers. The first determination did not include H atoms and had a R factor of 12.2%. The second however, did include H atoms and refined to R1 = 3.3%. A close inspection of the published ORTEP plot however, with hindsight, now provides clues to our new findings. A reduction in temperature leads to a loss of molecular symmetry and, primarily, a significant movement of the nitrate ligands. On re-warming the crystal the original structure is obtained, albeit with a little de-lamination of the crystal. We will describe our experiments and describe the structural changes observed. References 1. V. Manríquez, M. Campos-Vallette, N. Lara, N. González-Tejeda, O. Wittke, Guillermo Díaz, S. Diez, René Muñoz, and Lukas Kriskovic, J. Chem. Cryst., (1996), 26, 15. 2. A. Pajunen, Suom. Kemistil. B., (1969), 42, 15. 3. M.R. Sundberg, Inorg. Chim. Acta, (1994), 218, 151.  

Re-investigating the structures of [Cu(NO3)2(en)2] and [Cu(NO3)2(pn)2]: tales of twinning and a reversible phase change

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Re-investigating the structures of [Cu(NO3)2(en)2] and [Cu(NO3)2(pn)2]: tales of twinning and a reversible phase change

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