From Heptacoordinated CrIII Complexes with Cyanide or Isothiocyanate Apical Groups to 1D Heterometallic Assemblages with All‐Pentagonal‐Bipyramid Coordination Geometries

Abstract

A series of heptacoordinated CrIII complexes with either cyano or thiocyanato ligands in the apical positions are described and their ability to act as metallo‐ligands is illustrated. These compounds contain a pentadentate ligand, H2LN3O2R [H2LN3O2R = 2,6‐diacetylpyridinebis(benzoylhydrazone) for R = Ph, 2,6‐diacetylpyridinebis(4‐biphenylylcarbonylhydrazone) for R = biPh], chelated in the equatorial positions of the Cr metal center, thus imposing a bipyramidal‐pentagonal geometry on the complexes. The two axial water molecules of the precursor complexes [Cr(HLN3O2Ph)(H2O)2](NO3)2 (1) and [Cr(HLN3O2biPh)(H2O)2](NO3)2 (2) were easily exchanged with coordinating substituents such as CN– or NCS– to yield K[Cr(LN3O2Ph)(CN)2] (3), K[Cr(LN3O2biPh)(CN)2] (4), and [Cr(HLN3O2Ph)(NCS)2] (5). The reaction of 3 with MnII complexes [Mn(LN5)(H2O)2]Cl2 and [Mn(LN5R,R)Cl2] (LN5 and LN5RR represent macrocyclic pentadentate ligands: LN5 = 2,13‐dimethyl‐3,6,9,12,18‐pentaazabicyclo[12.3.1]octadeca‐1(18),2,12,14,16‐pentaene, and LN5RR = 2,21‐dimethyl‐(4R,9R,14R,‐19R)‐3,10,13,20,26‐pentaazatetracyclo[20.3.1.04,9.014,19]hexacosa‐1(26),22(23),24‐triene) yielded the 1D coordination polymers [Cr(LN3O2Ph)(CN)2Mn(LN5)](PF6) (6a,b) and the chiral chain [Cr(LN3O2Ph)(CN)2Mn(LN5R,R)](PF6)0.75Cl0.25 (7), which are constructed of only heptacoordinated metal centers. The assembly of 4 with [Mn(LN5)(H2O)2]Cl2 gave the neutral trinuclear complex [{Cr(LN3O2biPh)(CN)2}2Mn(LN5)] (8), whereas the association of 3 with the NiII Schiff‐base complex [Ni(valpn)] [H2(valpn) = 1,3‐propanediylbis(2‐iminomethylene‐6‐methoxyphenol] led to the discrete compound K[Ni(valpn)Cr(LN3O2Ph)(CN)2] (9). The crystal structures and magnetic properties of all the compounds are reported.