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(SiMe3)2, pmdeta =(Me2NCH2CH2)2NMe]

Abstract

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 NaOBu^t, KOBu^t+ pmdeta, and Rb(OC₆H₂Bu^t₂-2,6-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)°.