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The alkyls EuR2 (R = C(SiMe3)3) and YbR2 (R = [C(SiMe3)2(SiMe2X)], X = Me, CHCH2, or CH2CH2OEt) have been obtained from reactions between KR and MI2, and the ytterbium analogues of Grignard reagents, Yb[C(SiMe3)2(SiMe2X)]I·OEt2 (X = Me, CH=CH2, Ph or OMe) from reactions between RI and Yb metal. The compounds YbR2 and EuR2 crystallize as solvent-free monomers with C−M−C = 136−137°. The alkylytterbium iodides crystallize from diethyl ether as solvated iodide-bridged dimers in which the coordination at Yb is four when 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 = R2Yb + YbI2 is not observed when X = Me, but takes place readily when X = Ph, CHCH2, or OMe and provides a route to the dialkyls MR2 when the alkylpotassium KR cannot be obtained, e.g., when X = OMe. The dialkyl Yb[C(SiMe3)2(SiMe2X)]2 with X = Me reacts with ethers R‘OEt (R‘ = Et, Bu, But) to give ethene and alkoxides RYbOR‘. The corresponding reaction does not take place when X = OMe and is very slow when X = CHCH2.

Crystals of (RMe2Si)&K (R = Me, 1; R = Ph, 2), obtained from MeK and (RMezSi)&H, contain linear chains of alternate potassium cations and planar [(RMe&)&]-anions, with weak interactions between chains; in 1 the central carbon atoms of the anions are midway between the potassium cations, but in 2 cationanion pairs are linked by q6 coordination of phenyl groups.Methylpotassium has been carefully studied by X-ray powder methods and neutron diffraction,lJ but as far as we are aware there has hitherto been nosinglecrystal X-ray investigation of 4 donor-free organopotassium compound. We report the preparation and structures of compounds 1 and 2, which contain bulky organosilyl groups. (Me,Si),CK (PhMe,Si),CK 1 2 compound 1 can be obtained by either of the routeslf The colorless, exceedingly air-and moisture-sensitive +MeLi +KOBut -MeH -LiOBut (Me,Si),CH -(Me,Si),CLi -1 (a) +MeLi +(Messi)sCH -LiOBut -MeH

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