Turk J Chem 29 (2005) , 571 – 578. c  T ¨ UB ˙ ITAK Crystal Structure of Nitrato(2,2 ′ ,2 ′′ -terpyridyl)platinum(II) Hydrogen Dinitrate, [Pt(terpy)ONO 2 ][H(ONO 2 ) 2 ] Abdurrahman S ¸ENG ¨ UL Department of Chemistry, Faculty of Arts and Sciences, Karaelmas University 67100 Zonguldak-TURKEY e-mail: sengul@karaelmas.edu.tr Received 24.03.2005 The title compound, C15H12N6O9 Pt, consists of [Pt(terpy)ONO2] + cation and [H(ONO2)2] − anion, in which 2 nitrate groups are linked by a strong hydrogen bond [O···O 2449(1) ˚ A]. In the cation, the terpyridine is coordinated to Pt as a tridentate ligand and the fourth position is occupied by the nitrate ion’s oxygen. The coordination around Pt is square-planar. The coordinated nitrate moiety adopts a distorted trigonal-planar configuration. It belongs to the space group P ¯ 1 with a = 8.605(2), b = 10.220(3) ˚ A, c = 10.517(2) ˚ A and α = 89.51(1), β = 82.78(2), γ = 76.90(2) ◦ . Key Words: X-ray structure, terpyridine, hydrogen, nitrate, platinum, complex. Introduction Hydrogen-bonded species of the type (XHX) − are fairly common and new examples occur frequently 1 . Although there have been several studies on the salts that contain hydrogen dinitrate (HDN), the number of compounds studied using X-ray and neutron data is rather limited, and those known from diffraction works containing HDN anions are listed in Table 1. Two distinct conformations are known for the anions (I and II) as follows: O N O O H O N O O (I) N O O O H O N O O (II) A preliminary infrared and Raman investigation of CsHDN has been published together with the X-ray structure determination 2 . A quasi-tetrahedral coordination of the proton was postulated in this 571