N-phthaloylglycinato complexes of cobalt, nickel, copper and zinc Nilotpal Barooah a,b , Rupam J. Sarma a , Andrei S. Batsanov b , Jubaraj B. Baruah a, * a Department of Chemistry, Indian Institute of Technology, North Guwahati, Assam 781 039, India b Department of Chemistry, University of Durham, Durham DH1 3LE, United Kingdom Received 7 June 2005; accepted 14 June 2005 Available online 26 September 2005 Abstract The cobalt(II), nickel(II), copper(II) and zinc(II) complexes of N-phthaloylglycinato (Nphgly) ligands have been synthesised and characterised. The cobalt and zinc complexes have the composition [M(Nphgly) 2 (H 2 O) 4 ]2H 2 O with an octahedral geometry around the metal ion. In these two complexes, the phthaloylglycinato groups are monodentate and have four coordinated water molecules and two molecules of lattice water. The lattice water molecules are held through hydrogen bonding with one carbonyl group of the phthalimide part and the carbonyl group of glycinato part. Such water molecules are further held by hydrogen bonding to two coor- dinated water molecules. There are also two other coordinated water molecules having a different hydrogen-bonding environment. These two water molecules attached to the metal are stabilised by hydrogen bonding through two carbonyl groups from the glyci- nato part and the phthalimide part. Distinctions of these two sets of water environment are reflected in thermogravimetry and DSC of the complexes. In the thermogram of these two complexes there is loss of four water molecules at a relatively lower temperature than the other two water molecules. The copper complex containing N-phthaloylglycinato and pyridine ligands, having the compo- sition [Cu(Nphgly) 2 (py) 3 ], is prepared. This complex has a square pyramidal structure with one pyridine molecule at the axial posi- tion. The complex on thermal degradation leads to the formation of CuO at 380 °C. The similar nickel complex has the composition [Ni(Nphgly) 2 (py) 3 1.3H 2 O], having a trimeric H-bonded structure with a distorted octahedral environment around nickel(II). Ó 2005 Elsevier Ltd. All rights reserved. Keywords: N-phthaloylglycine; First row transition metal complexes; Thermochemistry; Hydrogen bonding 1. Introduction Amino acid complexes are important in biology [1,2]. The N-protected amino acids are used for the synthesis of peptide bonds in solid phase syntheses [3–5]. The phthalimide group acts as a protecting group for amines and amino acids [6–10]. The N-phthaloylamino acids undergo photochemical reactions to give rearranged products [11]. Several such phthalimide derivatives have importance in medicinal chemistry [12] and are used as antimicrobial reagents [13]. The silver(I) complex of N-phthaloylglycinato has an interesting three-dimen- sional network [14]. Several other studies on the transi- tion metal complexes of N-phthaloylglycine are reported but these studies lack structural details [15–17]. N-hydroxyphthalimide along with the cobalt(II) com- plexes in the presence of oxygen acts as a catalyst for selective oxidation of primary alcohols to the corre- sponding aldehydes [18,19]. Palladium complexes are known to catalyses amido-carbonylation of N-phthali- mide derivatives [20]. We have earlier discussed that in adducts of N-substituted phthalimide with polyhydroxy aromatics supramolecular features play an important role in the structure [21]. Thus, the structural features of these molecules are important and we report here characteristic features of N-phthaloylglycinato com- plexes of cobalt (II), zinc(II), copper(II) and nickel (II). 0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2005.06.057 * Corresponding author. Tel.: +91 361 2582301; fax: +91 361 2690762. E-mail address: juba@iitg.ernet.in (J.B. Baruah). www.elsevier.com/locate/poly Polyhedron 25 (2006) 17–24