Crystal structure of hemikis(tetrakis(m2-2-butenoato)-bis(2-butenoato)-tetra-aqua-di-samarium) hemikis(bis(m2-butenoato)-tetrakis(2-butenoato) tetra aqua-di-samarium) trihydrate

The structure of the title compound [Sm2(crot)6(H2O)4]2·3(H2O) (I), (crot= crotonate = butenoate = O2CCHCHCH3)] consists of two independent, centrosymmetric dimeric units, of similar composition but diverse coordination, viz., one of them doubly bridged (2×[h2:h1:m2]) and the remaining one quadruply bridged (2×[h1:h1:m2], 2×[h2:h1:m2]). The asymmetric unit is completed by three solvato water molecules, one of them depleted (occupation: 0.735 (14) ). The difference in bridging strengths is readily evidenced in the two quite dissimilar Sm···Sm distances observed: 4.1402 (8)Å,(doubly bridged), 3.9439 (8)Å (quadruply bridged). SmO9 polyhedra suyvey similar coordination distances which span the range 2.388 (3)-2.611 (3)Å for one of the Sm cations and 2.357 (3)-2.588 (3)Å for the other. All water hydrogens are involved in H-bonding, leading to the formation of a strongly linked 2D structure parallel to (010). These planar arrays are in turn transversally linked by one single bridging water molecule. There are in addition C═ C···C═C p interactions providing both to intra as well as intra planar cohesion. The compound is isomorphous to its Gd isologue 1 , but the present description unveils a number of molecular and supramolecular details not discussed therein