Sm(II) reduction chemistry of heteroalkynes: stable adducts, reductive coupling, reductive C-C/C-N bond cleavage and trapping of the tert-butyl fragment with bulky nitriles, phosphaalkynes and isonitriles

Reactions of a dimetallated N,N'-dimethyl substituted porphyrinogen Sm(II) complex with a series of t-butyl substituted heteroalkynes affords a diverse range of reactivity. The phosphaalkyne t-BuC P gives a dinuclear Sm(III) P-P reductively coupled complex of (t-BuC=PP=C-t-Bu)(2-) featuring a new mu-eta(2)(1,2-C,P) binding mode. In contrast, the nitrile aza analogue t-BuC N forms Sm(II) adducts that undergo reductive C-C bond cleavage at elevated temperatures to afford a trimeric Sm( III) cyanide (mu-C N(-)) complex. The isomeric isonitrile t-BuN C undergoes the related reductive C-N bond cleavage reactivity at milder temperatures, allowing the trapping of the tert-butyl fragment as a Sm(III) eta(2)-iminoacyl (t-BuC=N-t-Bu)(-) complex.