Toward Permetalated Alkyne/Azide 3 + 2 or “Click” Cycloadducts
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The Cu(I)-catalyzed reaction of the platinum butadiynyl complex trans-(C 6F 5)(p-tol 3P) 2Pt(C≡C) 2H and rhenium cyclopentadienylazide complex (η 5- C 5H 4N 3)Re(CO) 3 yields the 1,2,3-triazole trans-(C 6F 5)(p-tol 3P) 2PtC≡CC=CHN((η 5-C 5H 4)Re(CO) 3)N=N (54%), which upon treatment with Re(CO) 5OTf or Re(CO) 5Br affords Re(CO) 5+TfO - or cis-Re(CO) 4Br adducts derived from attack at N(3) (84-98%). The crystal structures of solvates of these three complexes are compared, but attempts to metalate the =CH groups were unsuccessful. However, the reaction of monometallic trans-(C 6F 5)(p-tol 3P) 2PtC≡CC=CHN(CH 2C 6H 5)N=N and MeI gives an N(3)-methyl triazolium salt (81%), which upon addition of Ag 2O and [RhCl(cod)] 2 yields the N-heterocyclic carbene complex trans-(C 6F 5)(p-tol 3P) 2PtC≡CC ...C(RhCl(cod)) ...N(CH 2C 6H 5) ...N ...N(Me). Further experiments and analyses suggest that =CH derivatization is possible only when the 1H NMR chemical shift is downfield of ca. δ 7.9 ppm. Electropositive metal fragments generally effect upfield shifts, meaning that insulating spacers, electronegative ligands, and/or new chemical methodologies will be required to construct tetrametallic arrays via click chemistry. © 2012 American Chemical Society.
author list (cited authors)
Clough, M. C., Zeits, P. D., Bhuvanesh, N., & Gladysz, J. A.