~ Pergamon PII: S0277-5387(97)00233-7 Polyhedron Vol. 16, No. 24, pp. 4247-4252, 1997 © 1997Elsevier Science Ltd All rightsreserved.Printedin Great Britain 0277-5387/97 $17.00+0.00 Manganese(ll) complexes of 3,6,9- trioxaundecanedioic acid (3,6,9-tddaH2) : X-ray crystal structures of [Mn(3,6,9- tdda)(H20)2] • 2H20 and {[Mn(3,6,9- tdda) (phen)2" 3H20]" EtOH}. Sebastian McCann, a Malachy McCann, a* Rev. Michael T. Casey, a Michael Devereux, b Vickie McKee, c Peter McMichael c and Jasper G. McCrea c a Chemistry Department, St. Patrick's College, Maynooth, Co. Kildare, Ireland b Dublin Institute of Technology, Cathal Brugha Street, Dublin, Ireland c School of Chemistry, Queen's University Belfast, N. Ireland BT9 5AG (Received 21 March 1997; accepted 28 May 1997) Ahstract--3,6,9-trioxaundecanedioic acid (3,6,9-tddaH2) reacts with Mn(CH3CO2)2"4H20 in ethanol to give [Mn(3,6,9-tdda)]'H20 (1). Recrystallization of 1 from methanol gives crystals of [Mn(3,6,9-tdda) (H20)2]'2H20 (2). Complex 1 reacts with an ethanolic solution of 1,10-phenanthroline (phen) to give {[Mn(3,6,9-tdda)(phen)2]" 3H20" EtOH}° (3). All of the complexes are extremely water soluble. Complexes 2 and 3 were structurally characterised. The manganese(II) ion in 2 is seven coordinate, with an approximately pentagonal bipyramidal 07 coordination sphere. The axial donors are water molecules and the pentagonal plane is occupied by the diacid, acting as a pentadentate ligand through the three ethereal oxygens and one oxygen atom from each of the carboxylate functions. In complex 3 the manganese(II) ion is six-coordinate, being bound to two bidentate phenanthroline ligands and to the carboxylate oxygen atoms from two symmetry related diacids which are coordinated in a eis fashion. The structure consists of polymeric chains, with diacid ligands bridging the manganese ions. There is n-n stacking of pairs of phenanthroline ligands on adjacent chains, running along both the z and y directions. © 1997 Elsevier Science Ltd Keywords: 3,6,9-trioxaundecanedioic acid; manganese; phenanthroline; X-ray dicarboxylic acid; zt-Tt stacking. We have previously described the synthesis, X-ray crystal structures and catalase-type activity of a num- ber of manganese(II) complexes containing aliphatic ~,~-dicarboxylic acid ligands [1-3]. In an effort to improve complex solubility, particularly in water, we have investigated the coordination of 3,6,9-trioxaun- decanedioic acid HO2CCHzOCH2CH2OCH2CH2 OCH2CO2H (3,6,9-tddaH2) to manganese(II). This diacid ligand contains three ethereal oxygen atoms in its backbone and this should enhance the solubility of the resulting complexes in protic solvents. To our knowledge the only previous report of the coor- dination chemistry of 3,6,9-tddaH: was the measure- * Author to whom correspondence should be addressed. ment of the stability constants of the 1 : 1 complexes formed with alkaline earth metals [4]. The large stab- ility constants found for complexes containing ~,o~- dicarboxylic acids containing ether linkages, com- pared to those containing the corresponding saturated ~,co-dicarboxylic acids (equivalent chain length but without ether oxygens), indicated coordination of the ethereal oxygen atoms to the metal centres. Herein we outline the synthesis, X-ray crystal structures and physical properties of two manganese(II) complexes of 3,6,9-tddaH2. RESULTS AND DISCUSSION 3,6,9-tddaH2 reacted with manganese(II) acetate tetrahydrate in ethanol to give a high yield of colour- 4247