LANTHANIDE(II) ALKYLS, AMIDES, ALKOXIDES AND ARYLOXIDES .4. SYNTHESISAND CHARACTERIZATION OF YTTERBIUM(II) ALKYLS

The following complexes were obtained and characterised: [Yb(CHR(2))(2 )(OEt(2))(2)] 1 from Ybl(2) and 2 NaCHR(2); [Yb(CHR(2))(3)Na] from Ybl (2) and 3 Na(CHR(2)); 1 and [Yb(CHR(2))(OR')(OEt(2))(2)] from [Yb(OR') (2)(OEt(2))(2)] and 2 K(CHR(2)); [Yb(CHR(2))(OR') (thf)(3)] from [Yb(O R')(2)(thf)(3)] and 1 K(CHR(2)); [Yb(CHR(2))(2)(tmen)] from [Yb(eta-C( 5)Me(5))(2)(OEt(2))], 2 Li(CHR(2)) and tmen; [Yb(CHR(2))(2)(dmpe)] fro m 1 and dmpe; [{Yb(CHR(2))(OEt(2))}2C6H4(NR)(2)-1,4] from 2 1 and C6H4 (NHR)(2)-1,4; [{Yb(CR(3))-(mu-O Et)(OEt(2))}(2)] from Ybl(2) and 1 or 2 K(CR(3)); [Yb(NR(2))(2){NC5H4(CH(2)R)-2}(2)] from [{Yb(NR(2))- (mu-N R(2))}(2)] I and 4 NC5H4(CH(2)R)-2; [Yb(NR(2))(2)(NC5H4(CHR(2))-2}] fr om I and 4 NC5H4(CHR(2))-2; [Yb{NC5H4(CHR)-2}(2)(dme)] from Ybl(2) and 2 [K{NC5H4(CHR)-2}(dme) (OEt(2))] and [K{Yb[NC5H4(CHR)-2](3)}(dme)(2) ] from Ybl(2) and 3 [K{NC5H4(CHR)-2}(dme)(OEt(2))] (R = SiMe(3), R' = C(6)H(2)Bu(2)(t)-2,6-Me-4, thf = tetrahydrofuran, tmen = Me(2)NCH(2)CH (2)NMe(2), dmpe = Me(2)PCH(2)CH(2)PMe(2) and dme = 1,2-dimethoxyethane ). A single-crystal X-ray diffraction study established [{Yb(CR(3))-(m u-OEt)(OEt(2))}(2)] to be a centrosymmetric dimer with each Yb atom in a distorted-tetrahedral environment and a central planar Yb2O2 ring. Variable-temperature H-1 NMR spectral data for [K{Yb[NC5H4(CHR)-2](3)} (dme)(2)] showed that the Me(3)Si protons become inequivalent at low t emperature, T-c = 238 K, due to a terminal-bridging NC5H4(CHR)-2 site- exchange process.