First Row Transition Metal(II) Thiocyanate Complexes, and Formation of 1‑, 2‑, and 3‑Dimensional Extended Network Structures of M(NCS)2(Solvent)2 (M = Cr, Mn, Co) Composition

The reaction of first row transition MII ions with KSCN in various solvents form tetrahedral (NMe4)2[MII(NCS)4] (M = Fe, Co), octahedral trans-MII(NCS)2(Sol)4 (M = Fe, V, Ni; Sol = MeCN, THF), and K4[MII(NCS)6] (M = V, Ni). The reaction of M­(NCS)2(OCMe2)2 (M = Cr, Mn) in MeCN and [Co­(NCMe)6]­(BF4)2 and KSCN in acetone and after diffusion of diethyl ether form M­(NCS)2(Sol)2 that structurally differ as they form one-dimensional (1-D) (M = Co; Sol = THF), two-dimensional (2-D) (M = Mn; Sol = MeCN), and three-dimensional (3-D) (M = Cr; Sol = MeCN) extended structures. 1-D Co­(NCS)2(THF)2 has trans-THFs, while the acetonitriles have a cis geometry for 2- and 3-D M­(NCS)2(NCMe)2 (M = Cr, Mn). 2-D Mn­(NCS)2(NCMe)2 is best described as MnII(μN,N-NCS)­(μN,S-NCS)­(NCMe)2 [= Mn2(μN,N-NCS)2(μN,S-NCS)2(NCMe)4] with the latter μN,S-NCS providing the 2-D connectivity. In addition, the reaction of Fe­(NCS)2(OCMe2)2 and 7,7,8,8-tetracyanoquino-p-dimethane (TCNQ) forms 2-D structured FeII(NCS)2TCNQ. The magnetic behavior of 1-D Co­(NCS)2(THF)2 can be modeled by a 1-D Fisher expression (H = −2JSi·Sj) with g = 2.4 and J/kB = 0.68 K (0.47 cm–1) and exhibit weak ferromagnetic coupling. Cr­(NCS)2(NCMe)2 and FeII(NCS)2TCNQ magnetically order as antiferromagnets with Tc’s of 37 and 29 K, respectively, while Mn­(NCS)2(NCMe)2 exhibits strong antiferromagnetic coupling. M­(NCS)2(THF)4 and K4[M­(NCS)6] (M = V, Ni) are paramagnets with weak coupling between the octahedral metal centers.