Donor-acceptor hydrogen (H)-bonding contributes to good temperature resistance for energetic compounds. Now we report a strategy which maximizes donor-acceptor H-bonding sites in the construction of new energetic compounds. The straightforward...

Three-dimensional molecular architectures self-assembled with tripodal and tetratopic donors are valuable because of their encapsulation properties. Here, we present Co(I)-Fe(II)-Pd(II) heterotrimetallic trifacial barrel 1, which was self-assembled using a newly synthesized tetratopic donor [CpCo(CbR)] [L; Cp = cyclopentadienyl, Cb = cyclobudiene, and R = 4-(4-pyridylphenyl)] and a 90° acceptor [ cis-(dppf)Pd(OTf)] (A1; dppf = (diphenylphosphino)ferrocene and OTf = CFSO). The heterotrimetallic barrel 1 exhibited selective 1:1 interaction with a N, N'-dimethyl-1,4,5,8-naphthalenetetracarboxylic diimide guest, as revealed by H NMR analysis. The self-assembly of donor L with two other Ru(II)-based 180° acceptors [( p-cymene)Ru(OO∩OO)(OTf)] [OO∩OO = 6,11-dioxido-5,12-naphthacenedione (A2) and oxalate (A3)] resulted in tetragonal-prismatic cages. Self-assembly using the longer acceptor A2 provided rare isomers of a tetragonal-prismatic cage by varying the orientation of the cyclopentadienyl moiety out-out (2) or out-in (2) of the cavity, whereas self-assembly using the shorter acceptor A3 selectively resulted in the tetragonal-prismatic cage 3. The three-dimensional molecular architectures 1-3 were characterized by combined spectroscopic and elemental analyses. The structures of molecular barrel 1 and prismatic cage 3 were elucidated by single-crystal X-ray analysis.

Reactions of {η 5 -C 5 H 4 [C(O)Cl]}Co(η 4 -C 4 Ph 4 ) and {η 5 -C 5 H 4 [C(O)Cl]}Fe(η 5 -Cp) with 8-aminoquinoline resulted in cobalt and iron sandwich derived carboxamides.The reaction of these carboxamides with Pd(OAc) 2 in acetonitrile resulted in αC−H activation of the Cp rings of the sandwich compounds and formation of novel palladacycles 3 and 4, having both N−H and one α-C−H hydrogen atom of the Cp ring displaced and palladium forming a square planar complex with acetonitrile as the fourth ligand. These air-stable palladacycles reacted with MeI and EtI in acetic acid, resulting in monoand 2,5-di-α-alkylated sandwich carboxamides, thereby providing a new method to realize Cp-multisubstituted sandwich compounds. Selectivity in α-substitution was observed in the presence of NaHCO 3 . The cobalt sandwich carboxamide 1, the new palladacycles 3 and 4, and the 2,5-dimethylated cobalt sandwich carboxamide 5 have also been structurally characterized using single-crystal X-ray structural studies.

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Polynitro compounds exhibit high density and good oxygen balance, which are desirable for energetic material applications, but their syntheses are often very challenging. Now, the design and syntheses of a new three-dimensional (3D) energetic metal–organic framework (EMOF) and high-energy-density materials (HEDMs) with good thermal stabilities and detonation properties based on a polynitro pyrazole are reported. Dipotassium 3,5-bis­(dinitromethyl)-4-nitro-1H-pyrazole (5) exhibits a 3D EMOF structure with good thermal stability (202 °C), a high density of 2.15 g cm–3 at 100 K (2.10 g cm–3 at 298 K) in combination with superior detonation performance (D v = 7965 m s–1, P = 29.3 GPa). Dihydrazinium 3,5-bis­(dinitromethyl)-4-nitro-1H-pyrazole (7) exhibits a good density of 1.88 g cm–3 at 100 K (1.83 g cm–3 at 298 K) and superior thermal stability (218 °C), owing to the presence of 3D hydrogen-bonding networks. Its detonation velocity (8931 m s–1) and detonation pressure (35.9 GPa) are considerably superior to those of 1,3,5-trinitro-1,3,5-triazine (RDX). The results highlight the syntheses of a 3D EMOF (5) and HEDM (7) with five nitro groups as potential energetic materials.