SYNTHESIS AND STRUCTURES OF THE HEAVIER ALKALI-METAL ALKYLS - THE X-RAY STRUCTURES OF [NA(MU-R)]INFINITY AND [RB(MU-R)(PMDETA)]2[R=CH(SIME3)2, PMDETA = (ME2NCH2CH2)2NME]

The crystalline, hexane-soluble metal alkyls [Na(mu-R)]infinity 1, [KR (pmedta)]m, and [Rb(mu-R)(pmdeta)]2 2 [R = CH(SiMe3)2, pmdeta = (Me2NC H2CH2)2NMe] have been prepared from LiR with equimolar portions of NaO Bu(t), KOBu(t) + pmdeta, and Rb(OC6H2But2-2,6-Me-4) + pmdeta, respecti vely; 1 has chains of alternating cations and planar R- anions which a re approximately orthogonal to the chains, (Na-C)av 2.555(10) angstrom (Na-C-H)av 76(3) and (Na-C-Na)av 152(1)-degrees, whereas 2 consists o f discrete dimers, (Rb-C)av 3.412(9) angstrom, Rb-C-Rb 75.3(2) and C-R b-C 104.7(2)-degrees.