Appreciably bent sp carbon chains: Synthesis, structure, and protonation of organometallic 1,3,5-triynes and 1,3,5,7-tetraynes of the formula (η5-C5Me5)Re(NO)(PPh 3)((C≡C)n-p-C6H4Me) Academic Article uri icon

abstract

  • The diyne (η5-C5Me5)Re(NO)(PPh 3)(C≡CC=CSiMe3) is elaborated to (η5-C5Me5)Re(NO)(PPh 3)(C≡CC≡CC≡CSiR3) (R = Me, 3a; Et, 3b) by sequences involving n-Bu4N+F- in aqueous THF to give (η5-C5Me5)Re(NO)(PPh 3)(C≡CC≡CH) (91%), n-BuLi/ CuI or t-BuOCu to give (η5-C5Me5)Re(NO)(PPh 3)(C≡CC≡CCu) (4), and coupling with IC=CSiMe3 (48%) or BrC≡CSiEt3 (84-65%). Complex 3b is similarly converted to (η5-C5Me5)Re(NO)(PPh 3)(C≡CC≡CC≡CH) (88%) and (η5-C5Me5)Re(NO)(PPh 3)(C≡CC≡CC≡CCu) (6). Reactions of 4 and 6 with BrC≡C-p-C6H4Me give the title compounds (η5-C5Me5)Re(NO)(PPh 3)((C≡C)n-p-C6H4Me) (n = 3, 7; 4, 8; 77-66%). Optimized one flask conversions of 1a and 3b to 7 (81%) and 8 (71%) are described. The crystal structures of 7 (monoclinic, P21c, a/b/c = 17.951(8)/8.377(5)/22.160(9) Å, β = 103.63(5)°, Z = 4), and 8 (monoclinic, P21/n, a/b/c = 8.426(3)/16.400(6)/25.400(9) Å, β = 97.51(3)°, Z = 4) show markedly curved sp carbon chains - much more than hexatriynes or octatetraynes reported to date. The bond angles associated with the Re(C≡C)nC moieties (min/max/avg) are 169.1(10)°/178.8(13)°/174.7° (7) and 170.0(9)°/178.8(10)°/175.7° (8). Other structural features are normal, and bending is provisionally ascribed to packing forces. Reaction of 7 and HBF4·OEt2 gives the cationic vinylidene complex [(η5-C5Me5)Re(NO)(PPh 3)(C=C(H)C≡CC≡C-p-C6H4Me)] + BF-4, the structure of which is established by extensive NMR analyses. © 1999 Elsevier Science S.A. All rights reserved.

author list (cited authors)

  • Dembinski, R., Lis, T., Szafert, S., Mayne, C. L., Bartik, T., & Gladysz, J. A.

citation count

  • 77

publication date

  • April 1999