Triple-decker complexes comprising heterocyclic middle-deck with coinage metals.

• Syntheses and structural characterization of group 9 triple decker sandwich complexes comprising a planar 5-membered middle-deck with coinage metal. • Density functional theory calculations provided a well-defined picture about the bonding of these heterometallic triple decker complexes. • The experimental results have been accompanied and rationalized using DFT studies. Earlier accounts of triple-decker complexes comprising main group elements and transition metals in the middle-deck, motivated us to synthesize triple-decker complexes containing coinage metals in the middle-deck. As a result, we have explored the reactivity of open-cage nido ‑ [(Cp*M) 2 { μ -B 2 H 2 E 2 }], 1 – 3 (Cp* = η 5-C 5 Me 5 , 1 : M = Co, E = S ; 2 : M = Co, E = Se; 3 : M = Rh, E = Se) with [CuBr(SMe 2)]. All the reactions yielded triple-decker complexes, [(Cp*M) 2 { μ -B 2 H 2 E 2 CuBr}], 4 – 6 (4 : M = Co, E = S ; 5 : M = Co, E = Se; 6 : M = Rh, E = Se) having [CuBr] in the middle-deck. The removal of the SMe 2 ligand resulted in the formation of complexes 4 – 6 as a single product. These complexes are examples of triple-decker species having a planar 5-membered [B 2 E 2 Cu] (E = S or Se) middle deck, in which the Cu exists as Cu(I) with an elongated M-Cu bonding interaction. Synthesized complexes have been established by ESI-MS, multinuclear nuclear magnetic resonance (NMR), and IR spectroscopy. The solid-state structures of 5 and 6 were confirmed by single-crystal X-ray diffraction analyses. Density functional theory (DFT) analyses of these complexes have presented a high electron donation from the [B 2 E 2 ] (E = S or Se) fragment of the middle ring to the axial metals and a weak bonding interaction between group 9 metals and Cu. [Display omitted] [ABSTRACT FROM AUTHOR]