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¡ä-dimethyl substituted porphyrinogen Sm(II) complex with a series of t-butyl substituted heteroalkynes affords a diverse range of reactivity. The phosphaalkyne t-BuCP gives a dinuclear Sm(III) P¨CP reductively coupled complex of (t-BuCPPC-t-Bu)2− featuring a new ¦Ì-¦Ç2(1,2-C,P) binding mode. In contrast, the nitrile aza analogue t-BuCN forms Sm(II) adducts that undergo reductive C¨CC bond cleavage at elevated temperatures to afford a trimeric Sm(III) cyanide (¦Ì-CN−) complex. The isomeric isonitrile t-BuNC undergoes the related reductive C¨CN bond cleavage reactivity at milder temperatures, allowing the trapping of the tert-butyl fragment as a Sm(III) ¦Ç2-iminoacyl (t-BuCN-t-Bu)− complex.