SYNTHESIS AND CHARACTERIZATION OF A TETRAMETHYLUREA ADDUCT OF A BISCYCLOPENTADIENYL YTTERBIUM(II) COMPLEX - X-RAY CRYSTAL-STRUCTURE OF YBCP(2)CENTER-DOT-2TMU

The complex YbCp(2) . 3TMU (TMU=1,1,3,3-tetramethylurea) has been synt hesized by addition of (CH3)(2)NCON(CH3)2 to YbCp(2) . THF, obtained b y reduction of YbCp(2)Cl . THF with sodium naphthalenide. The characte rization was done by metal analysis and IR and H-1 nuclear magnetic re sonance spectroscopies. Orange-reddish crystals of YbCp(2) . 2TMU, wer e obtained by slow evaporation of a benzene solution of YbCp(2) . 3TMU . The compound crystallizes in the monoclinic space group C2/c with fo ur molecules in a unit cell of dimensions a = 14.892(4) Angstrom, b = 12.792(2) Angstrom, c = 12.484(4) Angstrom, beta = 99.37(1)degrees and V = 2346(1)Angstrom(3) (R = 0.033, R(w) = 0.037 for 125 parameters an d 2127 reflections with F-o>3 sigma(F-o)).