Binuclear manganese(II)-thiolate complexes: Synthesis, characterization and nitrite induced structural changes

Abstract

The hitherto unexplored reactivity of Mn(II) towards thiolates has been investigated. The reaction of a hydrated Mn(II) salt with HN-Et-HPTB (N,N,N´,N´-tetrakis(2-(1-ethylbenzimidazolyl))-2-hydroxy-1,3 diaminopropane) and Et3N yielded, [Mn2(N-Et-HPTB)(DMF)4]3+ (1), while the use of MnCl2 yielded [Mn2(N-Et-HPTB)(Cl)(DMF)2]2+ (2). Further treatment of 2 with Et4NCl, produced [Mn2(N-Et-HPTB)(Cl)2]1+ (3). Treatment of either 1 or 3 with NaSPh produces [Mn2(N-Et-HPTB)(SPh)2]1+ (4). The reaction of a hydrated Mn(II) salt with HN-Et-HPTB and Et3N in the presence of R1COSH(R1 = Me, Ph), R2COOH (R2 = p-SH-C6H4, HS-CH2CH2) and PhCOONa, under similar conditions yielded [Mn2(N-Et-HPTB)(SCOR1)]2+ (R1 = Me, 5a; Ph, 5b), [Mn2(N-Et-HPTB)(µ-OOCR2)]2+ (R2 = p-SH-C6H4, 6a; HS-CH2CH2, 6b) and [Mn2(N-Et-HPTB)(PhCOO)]2+ (6c), while the use of 2-mercapto pyridine (o-SH-Py) or 4-mercapto pyridine (p-SH-Py) yielded [Mn2(N-Et-HPTB)(o-S-Py)]2+ (7) and [Mn2(N-Et-HPTB)(p-S-Py)]2+ (8). Further reaction of 1, 6c, 5b and 7, with NO2⁻ yielded [Mn2(N-Et-HPTB)(κO2-NO2)2]1+ (9), [Mn2(N-Et-HPTB)(κO2-O2CPh)(κO2-NO2)]1+ (10), [Mn2(N-Et-HPTB)(κOS-SCOPh)(κO2-NO2))]1+ (11) and [Mn2(N-Et-HPTB)(κOS-o-S-Py)(κO2-NO2))]1+ (12), respectively. Complexes 10–12 revealed interesting structural changes involving coordination mode shift of the carboxylate/thiocaboxylate bridges. Interestingly, further reaction of 9 with 4 equiv of PhSH (to remove the coordinated NO2⁻ as HNO2) yielded 4 and diphenyldisulfide via formation of PhSNO upon reaction of HNO2 and PhSH.