| dc.description |
[{Li(L)(CH2PMeR)}2][L = tetramethylethylenediamine (tmen), R = Me (1) or Ph (2); L =(â )-sparteine (sp), R = Ph (3)], prepared by treating the appropriate phosphine with LiBu<sup>n</sup>(L) in hexane or diethyl ether, are dimeric in the solid. The phosphinomethyl ligands bridge the two lithium atoms as part of six-atom heterocycles; Liâ C, P 2.145, 2.604; 2.14, 2.64; 2.20, 2.72à , respectively; (2) and (3) are homochiral and thus have a meso configuration. In benzene (1), (2), and [Li(tmen)(CH2PPh2)](5), are monomeric (cryoscopy), and <sup>7</sup>Liâ <sup>31</sup>P coupling only below ca. â 70 °C for (1)â (3) and (5) in toluene (1 : 1 doublet, <sup>7</sup>Li; 1 : 1 : 1 : 1 quartet, <sup>31</sup>P, J Lip 44.0â 53.4 Hz) is consistent with the presence of symmetrical dimers of the type found in the solid for (1)â (3). [[graphic omitted]Ph2-o}], (4), similarly prepared, has the lithium as part of a chelate ring in the solid, binding through the ipso carbon and P<sup> III </sup> centre; Liâ C,P 2.25(1), 2.65(1)à . Trilithio species based on P(C6H4CHR<sup>â </sup>)3(R = H or SiMe3) are generated via metallation using LiBu<sup>n</sup>(tmen). Treating the monolithio species derived from P(O)Me2Ph and LiBu<sup>n</sup>(sp) with Etl yields P(O)MePhPr<sup>n</sup> of 14% estimated optical purity. |
