Synthesis and structures of the heavier alkali metal alkyls; the X-ray structures of [Na(µ-R)] ∞ and [Rb(µ-R)(pmdeta)] 2 [R = CH(SiMe 3 ) 2 , pmdeta =(Me 2 NCH 2 CH 2 ) 2 NMe]

The crystalline, hexane-soluble metal alkyls [Na(µ-R)∞1, [KR(pmedta)]m, and [Rb(µ-R)(pmdeta)]22[R = CH(SiMe3)2, pmdeta =(Me2NCH2CH2)2NMe] have been prepared from LiR with equimolar portions of NaOBut, KOBut+ pmdeta, and Rb(OC6H2But2-2,6-Me-4)+ pmdeta, respectively; 1has chains of alternating cations and planar R– anions which are approximately orthogonal to the chains, (Na–C)av 2.555(10)Å, (Na–C–H)av 76(3) and (Na–C–Na)av 152(1)°, whereas 2 consists of discrete dimers, (Rb–C)av 3.412(9)Å, Rb–C–Rb 75.3(2) and C–Rb–C 104.7(2)°.