ALKYL DERIVATIVES OF EUROPIUM(-STRUCTURES OF EU[C(SIME(3))(3)](2), B[C(SIME(3))(2)(SIME(2)CH=CH2)]I-CENTER-DOT-OET(2) AND B[C(SIME(3))(2)(SIME(2)OME)]I-CENTER-DOT-OET(2)(2) AND YTTERBIUM(+2). CRYSTAL)

The alkyls EuR(2) (R = C(SiMe(3))(3)) and YbR(2) (R = [C(SiMe(3))(2)(S iMe(2)X)], X = Me, CH=CH2, or CH(2)CH(2)OEt) have been obtained from r eactions between KR and MI(2), and the ytterbium analogues of Grignard reagents, Yb[C(SiMe(3))(2)(SiMe(2)X)][. OEt(2) (X = Me, CH=CH2, Ph or OMe) from reactions between RI and Yb metal. The compounds YbR(2) and EuR(2) crystallize as solvent-free monomers with C-M-C = 136-137 degr ees. The alkylytterbium iodides crystallize from diethyl ether as solv ated iodide-bridged dimers in which the coordination at Yb is four whe n X = Me but is increased to five by chelation from the group X when X = OMe. When X = CH=CH2, the Yb...X interaction is weak. The reaction 2RYbI = R(2)Yb + YbI2 is not observed when X = Me, but takes place rea dily when X = Ph, CH=CH2, or OMe and provides a route to the dialkyls MR(2) when the alkylpotassium KR cannot be obtained, e.g., when X = OM e. The dialkyl Yb[C(SiMe(3))(2)(SiMe(2)X)](2) with X = Me reacts with ethers R'OEt (R' = Et, Bu, Bu(t)) to give ethene and alkoxides RYbOR'. The corresponding reaction does not take place when X = OMe and is ve ry slow when X = CH=CH2.