Reactivity of calix-tetrapyrrole SmII and SmIII complexes with acetylene: isolation of an "N-confused" calix-tetrapyrrole ring

The nature of the substituents present on the calix-tetrapyrrole tetra-anion ligand R2C(C4H2N)]4]4- (R = -(CH2)5-]0.5, Et) determines the type of reactivity of the corresponding SmII compounds with acetylene. With R = -(CH2)5-]0.5, dehydrogenation occurred to yield the nearly colorless dinuclear diacetylide complex -(CH2)5-]4-calix-tetrapyrrole]SmIII]2(mu-C2Li4)].THF as the only detectable reaction product. Conversely, with R = Et, acetylene coupling in addition to dehydrogenation resulted in the formation of a dimeric butatrienediyl enolate derivative (Et8-calix-tetrapyrrole)SmIIILiLi(thf)]2(mu-OCH=CH2)]]2(mu,eta2,eta'2-HC=C=C=CH)]. Reaction of the trivalent hydride (Et8-calix-tetrapyrrole)(thf)SmIII(mu-H)Li(thf)]]2 or of the terminally bonded methyl derivative (Et8-calix-tetrapyrrole)(CH3)SmIIILi(thf)]2Li(thf)2](mu3-Cl)]] with acetylene resulted in a mixture of the carbide (Et8-calix-tetrapyrrole)SmIII]2(mu-C2Li4)].Et2O with the dimerization product (Et8-calix-tetrapyrrole)SmIIILiLi(thf)]2(mu3-OCH=CH2)]]2-mu,eta2,eta'2-HC=C=C=CH)]. The same reaction also yielded a third product, a trivalent complex (Et8-calix-tetrapyrrole)SmIIILi(thf)2]]2], in which the macrocycle was isomerized by shifting the ring attachment of one of the four pyrrole rings.