• ab initio calculations;
  • cobalt;
  • hydride ligands;
  • iridium;
  • silyl ligands


A series of bis(silyl)bis(hydride) cobalt complexes [Cp*Co(H)2(SiR3)2] (Cp*=pentamethylcyclopentadienyl; SiR3=SiPh2H, SiMe3, SiH3, SiF3, SiCl3, SiBr3, Si(CF3)3; Co1Co7) as well as the analogous iridium complexes [Cp*Ir(H)2(SiR3)2] (SiR3=SiEt3, SiMe3, SiH3, SiF3, SiCl3, SiBr3, Si(CF3)3; Ir1Ir7) were studied to detect possible residual Si⋅⋅⋅H interactions. Tests of several density functionals by comparison with coupled-cluster results indicate that the TPSSh functional performs better than B3LYP, BP86, M06, M06L, and PBEPBE. Based on molecular structures, as well as Wiberg bond indices and J(Si,H) spin–spin coupling constants as indicators of a possible Si⋅⋅⋅H interaction, at least two residual Si⋅⋅⋅H interactions in Co2, Co5, and all four possible Si⋅⋅⋅H interactions in Co3 and Co4 have been detected. Co6 and Co7 exhibit stronger Si⋅⋅⋅H bonding than the other complexes studied. On the contrary, the iridium complexes Ir1Ir3 and Ir5Ir7 are classical iridium(V) bis(silyl)bis(hydride) complexes with only rudimentary Si⋅⋅⋅H interactions, if any.