Octahedral Metal Clusters as Building Blocks of Trimetallic Superexpanded Prussian Blue Analogues

The self-assembly of octahedral metal clusters (diamagnetic [Nb₆Cl₁₂(CN)₆]^4– or paramagnetic [Ta₆Cl₁₂(CN)₆]^3–), [Mn­(salen)]⁺ [salen = N,N′-ethylenebis­(salicylidene)­iminate] and mononuclear {M′(CN)_x} polycyanometallates ([Fe­(CN)₆]^4–, [Cr­(CN)₆]^3–, [Fe­(CN)₅(NO)]^2–, or [Ni­(CN)₄]^2–) building blocks results in the formation of a series of six cluster-containing 3D heterotrimetallic frameworks: [H₃O]₂[Nb₆Cl₁₂(CN)₆[Mn­(salen)]₆Fe­(CN)₆]·3H₂O (1), [H₃O]­[Nb₆Cl₁₂(CN)₆[Mn­(salen)]₆Cr­(CN)₆]·4H₂O (2), [Nb₆Cl₁₂(CN)₆[Mn­(salen)]₆Fe­(CN)₅(NO)]·5H₂O (3), [Nb₆Cl₁₂(CN)₆[Mn­(salen)]₆Ni­(CN)₄]·7H₂O (4), [H₃O]­[Ta₆Cl₁₂(CN)₆[Mn­(salen)]₆Fe­(CN)₆]·4H₂O (5), and [Ta₆Cl₁₂(CN)₆[Mn­(salen)]₆Cr­(CN)₆]·7H₂O (6). Single-crystal X-ray diffraction analyses show that compounds 1, 2, 5, and 6 have distorted face-centered-cubic frameworks that can be considered as superexpanded Prussian blue analogues built of two different hexacyanometallate nodes and expanded by insertion of the [Mn­(salen)]⁺ complex, while 4 features a quasi-superexpanded Prussian blue framework because the structure is based on the hexacyano metal cluster and disordered tetracyano [Ni­(CN)₄]^2– nodes. The powder X-ray diffraction of 3 indicates that it possesses a quasi-superexpanded Prussian blue framework based on the hexacyano cluster and disordered pentacyano [Fe­(CN)₅(NO)]^2– nodes. Compound 6 is the first compound containing three 3d–3d′–M₆ cluster (4d) spin centers. Magnetic measurements reveal that the overall magnetic nature can be systematically controlled by the choice of the octahedral metal cluster and polycyanometallate nodes. H₂/N₂ adsorption and thermal stability of the compounds were investigated.