Synthesis and thermochemical study of ligand substitution reactions of aminobis(phosphines), Ph 2 P(R)NPPh 2 , with [Me 2 Pt(COD)] Maravanji S. Balakrishna a, * , Srinivasan Priya a , William Sommer b , Steven P. Nolan b, * a Department of Chemistry, Indian Institute of Technology, Bombay, Mumbai 400 076, India b Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148, USA Abstract The reactions of aminobis(phosphines), Ph 2 PN(R)PPh 2 (R = H, Me, Et, n Pr, n Bu, Ph), with Me 2 Pt(COD) led to the formation of four-membered metallacycles in good yield. The enthalpies of the ligand substitution reactions are measured by the anaerobic solu- tion calorimetry in THF at 30 °C. Keywords: Aminobis(phosphines); Thermochemistry; Enthalpy; Platinum complexes 1. Introduction The utility of chelating bis(phosphine) ligands in orga- nometallic chemistry and in homogeneous catalysis [1] is well documented. The platinum complexes of bis(phos- phines) are of continuing interest owing to their potential use in processes such as coupling reactions [2], olefin reduction [3], and hydroformylation reactions [4,5]. In a homogeneous catalytic process, the reactivity at the metal center can be better understood by knowing the entropy of the system along with the metal–ligand bond disrup- tion energy. The bond disruption energy value is a net ef- fect of the stabilizing metal–ligand bond and the destabilizing strain energy caused by the formation of chelate ring. The thermochemical measurements can as- sess the metal–ligand interactions in organometallic sys- tems effectively [6,7]. Nolan and coworkers [8–13] and others [14,15] have extensively studied the steric and elec- tronic influences in the transition metal complexes con- taining tertiary phosphines and arsines using solution calorimetry. As a part of our interest in organometallic chemistry of phosphorus based ligands [16–21], we de- scribe in this paper the synthesis and the solution calori- metric studies of platinum (II) complexes of RN(PPh 2 ) 2 (R = H, Me, Et, n Pr, n Bu, Ph) (see Scheme 1). 2. Experimental 2.1. General considerations All experimental manipulations were performed un- der an inert atmosphere of dry nitrogen or argon, using standard Schlenk techniques. All the solvents were puri- fied by conventional procedures and distilled prior to Abbreviations: dpype, bis(dipyridylphosphino)ethane; dppf, bis (diphenyl-phosphino)ferrocene; diop, (2,2-dimethyl-1,3-dioxolan-4,5- diyl)bis(methylene) bis(diphenylphosphine); dmpe, bis(dimethyl- phosphino)ethane; depe, bis(diethylphosphino)ethane; dcpe, bis (dicyclohexylphosphino)ethane *