TY - JOUR

T1 - PdII-mediated integration of isocyanides and azide ions might proceed via formal 1,3-dipolar cycloaddition between RNC ligands and uncomplexed azide

AU - Kinzhalov, Mikhail A.

AU - Novikov, Alexander S.

AU - Luzyanin, Konstantin V.

AU - Haukka, Matti

AU - Pombeiro, Armando J.L.

AU - Kukushkin, Vadim Yu

N1 - Publisher Copyright: © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2016. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2016/1/1

Y1 - 2016/1/1

N2 - Reaction between equimolar amounts of trans-[PdCl(PPh3)2(CNR)][BF4] (R = t-Bu 1, Xyl 2) and diisopropylammonium azide 3 gives the tetrazolate trans-[PdCl(PPh3)2(CN4t-Bu)] (67%, 4) or trans-[PdCl(PPh3)2(CN4Xyl)] (72%, 5) complexes. 4 and 5 were characterized by elemental analyses (C, H, N), HRESI+-MS, 1H and 13C{1H} NMR spectroscopies. In addition, the structure of 4 was elucidated by a single-crystal X-ray diffraction. DFT calculations showed that the mechanism for the formal cycloaddition (CA) of N3- to trans-[PdCl(PH3)2(CNMe)]+ is stepwise. The process is both kinetically and thermodynamically favorable and occurs via the formation of an acyclic NNNCN-intermediate. The second step of the formal CA, i.e. cyclization, is rate limiting. Despite the fact that the substitution of CNMe by the N3- ligand is slightly thermodynamically favorable, we were unable to find paths on the potential energy surface for hypothetical CA between uncomplexed isocyanide and palladium-bound azide. Thus, we believe that the experimentally observed palladium tetrazolate complexes are, in fact, generated from the negatively charged uncomplexed azide and the positively charged metal-bound isocyanide species, and this reaction path is favorable from the viewpoint of Coulomb attraction.

AB - Reaction between equimolar amounts of trans-[PdCl(PPh3)2(CNR)][BF4] (R = t-Bu 1, Xyl 2) and diisopropylammonium azide 3 gives the tetrazolate trans-[PdCl(PPh3)2(CN4t-Bu)] (67%, 4) or trans-[PdCl(PPh3)2(CN4Xyl)] (72%, 5) complexes. 4 and 5 were characterized by elemental analyses (C, H, N), HRESI+-MS, 1H and 13C{1H} NMR spectroscopies. In addition, the structure of 4 was elucidated by a single-crystal X-ray diffraction. DFT calculations showed that the mechanism for the formal cycloaddition (CA) of N3- to trans-[PdCl(PH3)2(CNMe)]+ is stepwise. The process is both kinetically and thermodynamically favorable and occurs via the formation of an acyclic NNNCN-intermediate. The second step of the formal CA, i.e. cyclization, is rate limiting. Despite the fact that the substitution of CNMe by the N3- ligand is slightly thermodynamically favorable, we were unable to find paths on the potential energy surface for hypothetical CA between uncomplexed isocyanide and palladium-bound azide. Thus, we believe that the experimentally observed palladium tetrazolate complexes are, in fact, generated from the negatively charged uncomplexed azide and the positively charged metal-bound isocyanide species, and this reaction path is favorable from the viewpoint of Coulomb attraction.

UR - http://www.scopus.com/inward/record.url?scp=84953218837&partnerID=8YFLogxK

U2 - 10.1039/c5nj02564h

DO - 10.1039/c5nj02564h

M3 - Article

VL - 40

SP - 521

EP - 527

JO - New Journal of Chemistry

JF - New Journal of Chemistry

SN - 1144-0546

IS - 1

ER -