Molecular and Electronic Structures of lron(II)/(III) Complexes Containing N,S-Coordinated,Closed-Shell o-Aminothiophenolato(1-) and o-lminothiophenolato(2-) Ligands

摘要

The coordination chemistry of the ligands o-aminothiophenol,H(abt),4,6-di-tert-butyl-2-aminothiophenol,H[L~(AP)],and 1,2-ethanediamine-N,N'-bis(2-benzenethiol),H_4('N_2S_2'),with FeCI_2 under strictly anaerobic and increasingly aerobic conditions has been systematically investigated.Using strictly anaerobic conditions,the neutral,air-sensitive,yellow complexes (mu-S.S)(Fe~(II)abt)_2]_2 (1),(mu-S,S)[Fe~(II)(L~(AP))_2]_2-8CH_3OH (2),and (mu-S,S)[Fe~(II)('H_2N_2S_2')]_2-CH_3CN (3) containing high spin ferrous ions have been isolated where (abt)~(1-),(L~(AP))~(1-),and ('H_2N_2S_2')~(2-) represent the respective N.S-coordinated,aromatic o-aminothiophenolate derivative of these ligands.When the described reaction was carried out in the presence of trace amounts of 0_2 and [PPh_4]Br,light-green crystals of [PPh_4][Fe~(II)(abt)_2(itbs)] centre dot [PPh_4]Br (4) were isolated.The anion [Fe~(II)(abt)_2(itbs)]~- contains a high spin ferrous ion,two N.S-coordinated oaminophenolate(1-) ligands,and an S-bound,monoanionic o-iminothionebenzosemiquinonate(1-).T radical,(itbs)~-.Complex 4 possesses an S_1 = 3/2 ground state.In the absence of [PPh_4]Br and presence of a base NEt_3 and a little 0_2,the ferric dimer (mu-NH,NH)[Fe~(III)(L~(AP))(L~(IP))]_2 (5a) and its isomer (mu-S,S)[Fe~(III)(L~(AP))(L~(IP))]_2 (5b) formed.(L~(IP)~(2-) represents the aromatic o-iminothiophenolate(2-) dianion of H[L~(AP)].The structures of compounds 2,4,and 5a have been determined by X-ray crystallography at 100(2) K.Zero-field Mossbauer spectroscopy of 1,2,3,and 4 unambiguously shows the presence of high spin ferrous ions:The isomer shift at 80 K is in the narrow range 0.85-0.92 mm s~(-1),and a large quadrupole splitting,|DELTAE_Q|,in the range 3.24-4.10 mm s~(-1),is observed.In contrast,5a and 5b comprise both intermediate spin ferric ions (S_(Fe) = 3/2) which couple antiferromagnetically in the dinuclear molecules yielding an S_t = 0 ground state.