Structure and bonding of novel paddle-wheel diiridium polynitrogen compounds: A stronger iridium–iridium bonding by density functional theory

• The title complexes have a very short metal- metal distances (～2.4 Å).
• The Ir2(N5)4 has a paddlewheel-type structures.
• The Ir2(N5)4 may be used as HEDMS.
• The Ir can help to stabilize the (N5–) ligand.
• The Ir2(N5)4 might be a viable desirable.

The equilibrium geometries, thermochemistry, and bonding of diiridium polynitrogen compounds Ir2(N5)4 were predicted using density functional theory. For Ir2(N5)4 the preferred structure was a novel paddle wheel structure. Natural bonding orbital (NBO) analysis indicated that the bonding between the metal atom and the five-membered ring was predominantly ionic for Ir2(N5)4 species. In addition, Nucleus independent chemical shift (NICS) values confirmed that the planar N5− exhibited aromaticity in Ir2(N5)4. The dissociation energies into mononuclear fragments for Ir2(N5)4 were predicted to be 155.1 (149.7) kcal/mol, but Ir2(N5)4 is thermodynamically unstable with respect to dissociation into Ir2(N5)3 + N5. Our most remarkable structural finding is the extremely short Iridium–Iridium distance (2.394 Å, MPW1PW91) predicted for the paddle wheel structure of Ir2(N5)4. The new class of potential compounds was predicted stable enough for practical applications as high-energy density materials (HEDMs).

A unique Paddlewheel-type structures of Ir2(N5)4 was predicted using density functional theory. The interaction of the N5− with Ir and nucleus independent chemical shift and thermochemistry were reported.Figure optionsDownload as PowerPoint slide