Synthesis and structural characterisation of alkali metal complexes of heteroatom-stabilised 1,4- and 1,6-dicarbanions
作者:Keith Izod、Lyndsey J. Bowman、Corinne Wills、William Clegg、Ross W. Harrington
DOI:10.1039/b822054a
日期:——
A straightforward Peterson olefination reaction between either [(Me2PhSi)3C}Li(THF)] or in situ-generated [(Me3Si)2Ph2P(BH3)}CLi(THF)n] and paraformaldehyde gives the alkenes (Me2PhSi)2CCH2 (1) and (Me3Si)Ph2P(BH3)}CCH2 (2), respectively, in good yield. Ultrasonic treatment of 1 with lithium in THF yields the lithium complex [(Me2PhSi)2C(CH2)}Li(THF)n]2 (3), which reacts in situ with one equivalent of KOBut in diethyl ether to give the potassium salt [(Me2PhSi)2C(CH2)}K(THF)]2 (4). Similarly, ultrasonic treatment of 2 with lithium in THF yields the lithium complex [[Ph2P(BH3)}(Me3Si)C(CH2)]Li(THF)3]2.2THF (5). The bis(phosphine-borane) [(Me3Si)Me2(H3B)P}CH(Me2Si)(CH2)]2 (6) may be prepared by the reaction of [Me2P(BH3)CH(SiMe3)]Li with half an equivalent of ClSiMe2CH2CH2SiMe2Cl in refluxing THF. Metalation of 6 with two equivalents of MeLi in refluxing THF yields the lithium complex [[Me2P(BH3)}(Me3Si)C(SiMe2)(CH2)}]Li(THF)3]2 (9), whereas metalation with two equivalents of MeK in cold diethyl ether yields the potassium complex [[Me2P(BH3)}(Me3Si)C(SiMe2)(CH2)}]2K2(THF)4]∞ (10) after recrystallisation. X-Ray crystallography shows that, whereas the lithium complex 5 crystallises as a discrete molecular species, the potassium complexes 4 and 10 crystallise as sheet and chain polymers, respectively.