Synthesis and reactivity towards amines of benzisothiazolinate-bridged paddlewheel dimers [M2(μ-bit)4·2H2O] (M = Mn, Co, Ni, Cu)

Abstract Addition of sodium benzisothiazolinate, Na(bit), to metal salts MX 2 .nH 2 O (M = Mn, Co, Ni, Cu) affords a simple high yielding route to benzisothiazolinate-bridged paddlewheel dimers [M 2 (μ -bit) 4 .2H 2 O]. Upon reaction with amines these serve as useful synthons to access benzisothiazolinate chemistry. Addition of 4-aminopyridine (4-ampy) in ethanol leads to cleavage of dimers and formation of all trans- [M(4-ampy) 2 (κ 1 -bit) 2 (EtOH) 2 ] (M = Co, Ni), the bit ligand binding in a monodentate fashion through the amide-nitrogen. With a slight excess of ethylenediamine (en) a similar cleavage occurs to afford trans -[M(κ 1 -bit) 2 (κ 2 -en) 2 ] (M = Co, Ni, Cu). For nickel and copper, the intermediate five-coordinate mono-diamine derivatives cis- [M(κ 1 -bit) 2 (κ 2 -en)(H 2 O)] (M = Ni, Cu) have also been isolated. It is not necessary to isolate the dimers to access this chemistry; direct reactions of MX 2 .nH 2 O with either 1,4-bipyridine (bipy) or 1,10-phenanthroline (phen) and Na(bit) lead to cis- [M(κ 1 -bit) 2 (κ 2 -bipy)(H 2 O) 2 ] (M = Co, Cu) and cis- [M(κ 1 -bit) 2 (κ 2 -phen)(H 2 O)L] (M = Mn, Co, L = H 2 O; M = Cu, L = EtOH) respectively. Molecular structures of [Cu 2 (μ -bit) 4 .2dmf].2dmf, trans- [Co(4-ampy) 2 (κ 1 -bit) 2 (EtOH) 2 ] and [Cu(κ 1 -bit) 2 (en)(H 2 O)].H 2 O have been determined. This work highlights the easy accessibility of under exploited transition metal benzisothiazolinate chemistry and shows that this flexible ligand can adopt monodentate and bridging bidentate coordination modes.