NOVEL LANTHANIDE PYRAZOLYL BORATE COMPLEXES WITH FAST DATA ACQUISITION AT LOW TEMPERATURE. Mark R.J. Elsegood,^a Andrea Sella,^b Graham H. Maunder^b and Sung-Ying Liu^b, ^aDept. of Chemistry, Bedson Building, The University of Newcastle-upon-Tyne, Newcastle-upon-Tyne, NE1 7RU, UK., ^bDept. of Chemistry, University College London, 20 Gordon St., London, WC1H OAJ, UK.

We present the structures of several lanthanide complexes containing sterically demanding polypyrazolylborate ligands. Such compounds show considerable potential in organic synthesis. Structural data are therefore vital in the understanding of structure-reactivity relationships.

Data were collected either on a state-of-the-art Siemens SMART area detector diffractometer, or on a Stoe-Siemens 4-circle instrument. Data sets are typically collected overnight on the SMART, aided by the excellent sensitivity of the CCD detector, rapid data read-out times, and high data redundancy.

Since many of the compounds are air and moisture sensitive, and frequently crystallise with solvent molecules included in their lattices, data are routinely collected at low temperature using a Siemens LT2 low temperature device (SMART), or a Cryostream Cooler (Stoe-Siemens). Previous attempts at collecting data at ambient temperatures were unsuccessful.

We present our latest results, including complexes of La, Sm, and Yb. The structure of [Sm(bis-pyrazolylborate)-O-C-Mo(CO)₂(MeCp).1.5 C₇H₈, for example, illustrates the great benefits of rapid data collection at low temperature.