Synthesis, Structure and Magnetic Properties of a Cyclic Heterotetranuclear Co 3 Fe Complex of 2‐Mercaptophenol (H 2 mp) with tri‐ n ‐Butylphosphine Participation

Neutral heterotetranuclear complex Co 3 Fe(mp) 4 (Hmp)(PBu n 3 ) 3 2 (PBu n 3 = tri‐ n ‐butylphosphine) of 2‐mercaptophenol (H 2 mp) was synthesized in a molar ratio of CoCl 2 :FeCl 3 :H 2 mp:NaOMe:PBu n 3 = 0.75:0.25:1:2:1 under anaerobic conditions. It represents partially Fe III ‐substituted form of the asymmetric mixed‐valence tetracobalt complex Co 4 (mp) 4 (Hmp)(PBu n 3 ) 3 (1). 2 crystallizes in the triclinic space group Pl̄, with a = 12.373(2) Å, b = 15.677(3) Å, c = 20.571(4) Å, α = 93.59(3)° β = 93.45(3)° γ = 112.30(3)°, V = 3669 Å 3 , and Z = 2. The molecule exhibits a cyclic skeleton of Co 3 FeS 4 O 3 with two doubly μ 2 ‐S bridges, one doubly μ 2 ‐O bridge, and one singly μ 2 ‐O bridge. The four mp 2− ligands display two different modes, O b S b ‐T and O t S b , while the monoanion Hmp − is only terminally chelated to Fe 3+ ion in HO t S t fashion (b stands for bridge, t for terminal, and T for trinuclear). The three Co centers are located in approximately square‐based pyramidal environments, and the Fe atom in distorted trigonal bipyramidal geometry. Three types of main fragment ions were observed in the FAB mass spectrum of 2. The dissociation of the fragments follows the order: PBu n 3 first, then Hmp and mp ligands. Moreover, the dissociation of Fe(Hmp) is first, followed by Co(mp) and Co(mp) 2 , according with the fact that Fe(Hmp) is only loosely bonded. Variable‐temperature magnetic susceptibility measurements showed that 2 exhibits weak magnetic exchange interactions.