Synthetic and structural investigations of some lithium thiolates and thiocarboxylates

Abstract

A series of closely related lithium aryl thiolates with pyridine as a donor ligand have been prepared. X-ray structure determination (Dr. W. Clegg) has shown that [PKSLi.(NC(_5)H(_5))] crystallises as an infinite chain polymer. Insertion of a methylene group between the phenyl ring and sulphur as in (PhCH(_2)SLi .NC(_5)H(_5). ] (_oo) produced an infinitely folded ladder polymer with Li-S rungs, while introduction of an 0-methyl group produces the monomeric complex [o-MeC(_6)H(_4)SLi .(NC(_5)H(_5))(_3)].The unusual symmetrical complex [Li(_14) (SCH(_2)Ph)(_12) S(TMEDA.)(_6)] has been prepared, in which a central sulphur atom is surrounded by a distorted cube of lithium atoms, each edge of which is bridged by a benzyl thiolate group such that the twelve S atoms form a cubo- octahedron: a further six Li atoms form a larger outer octahedron. When TMEDA is present in excess it appears that both PhSLi and PhCH(_2)SLi form dimeric compounds with a central Li(_2)S(_2) ring but structure determination of these complexes is incomplete.[PhOOSLi.TMEDA](_2)has been prepared and crystallises as a centrosymmetric dimer containing a chair shaped central eight membered (OOSLi)(_2) ring with the Li atoms out of the (COS)(-2), molecular plane. Lithiation of the related acids PhOOOH and PhCSSH has been carried out in the presence of TMEDA but crystal growth has so far been unsuccessful. Ab initio m.o. calculations on related model compounds are included. A preliminary study has been carried out on the lithiation of the thio-oxime (Ph(_2) C-NSH). Results were encouraging but detailed investigation is needed. The reaction of S(_4) N(_4) with BI(_3) produces, not the expected adduct, S(_4)N(_4) .BI(_3) , but an intractable polymer, empirical formula, S(_3)N(_3)BI. Other adducts of S(_4).N(_4) and (PhCN_2) S(_2))(_2), were prepared but were unsuitable for further reactions. The reaction of lithium borohydride and sulphur in THF to produce sulphurated lithium borohydride has been modified to give a controllable reaction. Further reaction with TMEDA gives clear orange crystals of a complex the composition of which is still unknown.