LOW TEMPERATURE NEUTRON AND X-RAY DIFFRACTION STUDIES OF Mn(cth)Cu(oxpn)(CF₃S0₃)₂(cth)=(+/-)-5,7,7,12,1414-hexamethyl-1,4,8,11-tetraazacyclotetradecane;(oxpn)=N,N'-Bis(3-aminopropyl)oxamide. V. Baron^a, H. Rundlöf^b, R. Tellgren^b, B. Gillon^c, O. Kahn^d, ^aNFL Studsvik, S-611 82 Nyköping, Sweden, ^bInst. of Chem., Uppsala Univ., Box 531, S-751 21 Uppsala, Sweden, ^cLLB, CEA- CNRS, CEN Saclay, 91191 Gif-sur-yvette cedex, France, ^dICMCB, Chateau de Brivazac, 33600 Pessac, France

The present investigation illustrates the complementarily of neutron and x-ray diffraction for studies of disordered and hydrogen-bonded heterodinuclear compounds. This has been performed to provide nuclear structure factors and to form the basis for a spin distribution study of Mn(cth)cu(oxpn)(CF₃SO₃)₂(1,2).

A neutron diffraction study at 40 K was first attempted; however, it was not possible to refine all parameters. The number of atoms was 100 atoms/unit cell including 48 hydrogen atoms and the triflate anions were found to be disordered. We therefore believes that a combination of x-ray and neutron diffraction data was the best way to solve this problem.

The unconventional space group P2₁/a was used to be consistent with the room temperature study (3). The lattice parameters at low temperature are a= 17.525(3), b= 17.955(4), c= 12.804(2) Å, and ß= 104.97(2)deg. with Z= 4. The structure consists of an oxamido- bridged Mn^IICu^II part and two uncoordinated triflate anions. The Mn(II) ion is in an elongated octahedral surrounding, and the Cu(II) ion in a squareplanar surrounding. The intramolecular Mn--Cu separation is 5.440(1) Å whereas the shortest intermolecular metal-metal (Mn--Cu) is equal to 7.825(1)Å.

(1) O.Kahn, B.Gillon, R.Tellgren, H. Rundlöf, V. Baron, (In press).

(2) V.Baron these de l'universite de Paris XI -Orsay (19 Decembre 1994).

(3) C.Mathoniere, O. Kahn, J.-C. Daran, H. Hilbig, F.H. Köhler, Inorg.Chem., 32, 4057, 1993.