Synthesis of heterocyclic ligands by diheterocyclization at the rhenium(I) allenylidene [(triphos)(CO)2Re{C=C=CPh2}](OSO2CF3).: 1.: Reactivity with dipolar N,N-heterocycles

1,2,3-Diheterocyclizations at the allenylidene ligand in the complex [(triphos)(CO)(2)Re{C=C=Ph-2}]OTf (1; triphos = MeC(CH2PPh2)(3), OTf = OSO2CF3) readily occur upon reacting 1 with NN-heterocycles such as 1H-benzotriazole, 2-aminopyridine, and 2-aminothiazole. The reaction of 1 with 1H-benzotriazole leads to [(triphoS)(CO)(2)Re{C=C(H)C(Ph)}]N(C6H4)N=NI}OTf (4). Deprotonation of 4 with sodium methoxide in tetrahydrofuran at room temperature yields the alkynyl derivative [(triphos)(CO)(2)Re{C equivalent to CC(Ph)(2)(NC6H4N=N)}] (5) via ring opening of the triazaindenyl moiety in 4. Reaction of 1 with 2-aminopyridine or 2-aminothiazole in CH2Cl2 leads to the heterobicyclic compounds [(triphos)(CO)(2)Re{C=C(H)C(Ph)(2)N(H)C(CH)(4)N=N){N}]OTf (6) and [(triphos)(CO)(2)Re{C=C(H)C(Ph)(2)N(H)CS(CH)(4)N}OTf (8), respectively. Both complexes undergo regioselective deprotonation at the N-H heterocycle group by treatment with sodium methoxide in THF, giving the neutral species [(triphoS)(C0)2RejC=QH)CF__ (Ph)(2)NC(CH)(4)N}] (7) and [(triphos)(CO)(2)Re{C=C(H)C(Ph)(2)NCS(CH)(2)N}] (9), respectively. The X-ray structures of the new organorhenium species 4 and 7-9 have been determined, which have confirmed that the addition of the NH bond of the NN-heterocycle occurs always across the C-beta-C-gamma double bond of the allenylidene chain.