Synthesis and characterisation of bulky guanidines and phosphaguanidines: precursors for low oxidation state metallacycles

Reactions of alkali metal amides or phosphides with the bulky carbodiimide, ArN=C=NAr (Ar = C6H3Pr2i-2,6), followed by aqueous work-ups, have yielded several guanidines, ArNC(NR2) N(H) Ar (R = cyclohexyl (GisoH) or Pr-i(PrisoH); NR2 = cis-NC5H8Me2-2,6 (PipisoH)), a bifunctional guanidine, {ArNCN(H)Ar}(2){mu-N(C2H4)(2)N} (Pip(GisoH)(2)), and two phosphaguanidines, ArNC(PR2)N(H)Ar (R = cyclohexyl (CyP-GisoH) or Ph (PhP-GisoH)). A very bulky guanidine, ArNC{N(Ar)SiMe3} N(H) Ar (ArSi-Giso), and an aryl coupled bifunctional guanidine, {ArN(H)C(NPr2i)NC6H2Pr2i-2,6-}(2) (PrisoH)(2), have been prepared by other routes. All compounds have been crystallographically characterised and shown to exist in a number of isomeric forms in the solid state. These appear to be largely retained in solution. The deprotonation of GisoH with (BuLi)-Li-n in either hexane or THF led to crystallographically characterised dimeric and monomeric complexes respectively, viz. [Li{Li(kappa(2)-N,N'-Giso)(2)}] and [Li(THF)(eta(1)-N,eta(3)-Ar-Giso)]. Deprotonation of PrisoH and Pip(GisoH)(2) with K[ N(SiMe3)(2)] gave the unsolvated polymer, [{K(eta(1)-N,eta(6)-Ar-Priso)}(infinity)], and the solvated complex, [{K(THF)(2)}{Pip(Giso)(2)}{K(THF)(3)}], respectively.