Reactivity of Calix-Tetrapyrrole SmII and SmIII Complexes with Acetylene: Isolation of an “N-Confused” Calix-Tetrapyrrole Ring

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Abstract
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(μ-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)SmIII{Li[Li(thf)]2(μ3-OCH=CH2)}}2(μ,η2,η′2-HC=C=C=CH)]. Reaction of the trivalent hydride [(Et8-calix-tetrapyrrole)(thf)SmIII{(μ-H)[Li(thf)}]2 or of the terminally bonded methyl derivative [(Et8-calix-tetrapyrrole)(CH3)SmIII{[Li(thf)]2[Li(thf)2](μ3-Cl)}] with acetylene resulted in a mixture of the carbide [{(Et8-calix-tetrapyrrole)SmIII}2(μ-C2Li4)]⋅Et2O with the dimerization product [{(Et8-calix-tetrapyrrole)SmIII{Li[Li(thf)]2(μ3-OCH=CH2)}}2(μ,η2,η′2-HC=C=C=CH)]. The same reaction also yielded a third product, a trivalent complex [{(Et8-calix-tetrapyrrole*)SmIII[Li(thf)2]}2], in which the macrocycle was isomerized by shifting the ring attachment of one of the four pyrrole rings.

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