Detailed study on identification and thermal decomposition of solid title compounds I and 2 crystallized from the used aqueous ammonia solutions of Pd(NH3)(2)(NO2)(2) and Pt(NH3)(2)(NO2)(2). has been carried out. Beyond the composition of complexes 1 and 2, their trans square planar configuration have already been recognized by reference IR spectra and powder XRD patterns, nevertheless their exact molecular and crystal structure as of trans-Pd(NH3)(2)(NO2)(2) (1, Pd-NN) and trans-Pt(NH3)(2)(NO2)(2) (2, Pt-NN) has been determined by single crystal X-ray diffraction (R=0.0515 and 0.0341), respectively. Despite their compositional and configuration analogy, they crystallize in different crystal systems and space groups. The crystals of I (Pd-NN) are triclinic (space group No. 2, P-1, a = 5.003(1)angstrom, b = 5.419(1)angstrom, c = 6.317(1)angstrom, alpha = 91.34(2)degrees, beta = 111.890(10)degrees, gamma = 100.380(10)degrees), while those of 2 (Pt-NN) are monoclinic (space group No. 5, C2, a = 7.4235(16)angstrom, b = 9.130(2)angstrom, c = 4.4847(10)angstrom, beta = 99.405(7)degrees). The pyrolytic processes of I and 2 (which might be sensitive to shock and heat) have been followed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), while the evolved gaseous species have been traced in situ by online coupled TG/DTA-ECA-MS and TG-EGA-FTIR instruments in He and air. Pd and Pt powders, forming as final solid products in single step, are captured and checked by TG and XRD. Whilst the unified evolved gas analyses report evolution of N-2, H2O, NH3, N2O, NO, and NO2 gases as gaseous product components in the exothermic decomposition of both trans-Pd(NH3)(2)(NO2)(2) (1) and trans-Pt(NH3)(2)(NO2)(2) (2) starting from ca. 230 and 220 degrees C, in sealed crucibles with a pinhole on the top, respectively. (C) 2009 Elsevier B.V. All rights reserved.