Two Fe3(μ3-S)2(CO)8 clusters with terminal N-heterocyclic carbenes

The title compounds with terminal N-heterocyclic carbenes, namely octacarbonyl(imidazolidinylidene-κC(2))di-μ3-sulfido-triiron(II)(2 Fe-Fe), [Fe3(C3H6N2)(μ3-S)2(CO)8], (I), and octacarbonyl(1-methylimidazo[1,5-a]pyridin-3-ylidene-κC(3))di-μ3-sulfido-triiron(II)(2 Fe-Fe), [Fe3(C8H8N2)(μ3-S)2(CO)8], (II), have been synthesized. Each compound contains two Fe-Fe bonds and two S atoms above and below a triiron triangle. One of the eight carbonyl ligands deviates significantly from linearity. In (I), dimers generated by an N-H···S hydrogen bond are linked into [001] double chains by a second N-H···S hydrogen bond. These chains are packed by a C-H···O hydrogen bond to yield [101] sheets. In (II), dimers generated by an N-H···S hydrogen bond are linked by C-H···O hydrogen bonds to form [111] double chains.