FULL PAPER Organotin (IV) Complexes as Catalyst for Biodiesel Formation: Synthesis, Structural Elucidation and Computational Studies Muhammad Zubair 1 | Muhammad Sirajuddin 2 | Ali Haider 1 | Ishtiaq Hussain 3 | Muhammad Nawaz Tahir 4 | Saqib Ali 1 1 Department of Chemistry, Quaid‐i‐Azam University, Islamabad 45320, Pakistan 2 Department of Chemistry, University of Science and Technology Bannu, Bannu 28100, Pakistan 3 Department of Pharmaceutical Science, Abbottabad University of Science and Technology, Havelian Abbottabad, Pakistan 4 Department of Physics, University of Sargodha, Pakistan Correspondence A. Haider and S. Ali, Department of Chemistry, Quaid‐i‐Azam University, Islamabad, 45320, Pakistan. Email: ahaider@qau.edu.pk; drsa54@hotmail.com Funding information Higher Education Commission, Pakistan, Grant/Award Number: 6796/KPK/NRPU/ R&D/HEC/2016; Quaid‐i‐Azam Univer- sity, Grant/Award Number: URF 2018‐19; Higher Education Commission Pakistan, Grant/Award Number: 6796/KPK/NRPU/ R&D/HEC/2016 Here we have presented the synthesis of three novel triorganotin (IV) complexes: trimethylstannyl 4‐(3‐chloro‐2‐methylphenylamino)‐4‐oxobut‐2‐enoate (1); tributylstannyl 4‐(3‐chloro‐2‐methylphenylamino)‐4‐oxobut‐2‐enoate (2) and triphenylstannyl 4‐(3‐chloro‐2‐methylphenylamino)‐4‐oxobut‐2‐enoate (3). The ligand and its three complexes were spectroscopically characterized by NMR ( 1 H and 13 C) in solution and by FT‐IR in solid state. Complexes 1 and 2 were fur- ther characterized by single crystal X‐ray diffraction analysis. The X‐ray crystal- lographic data reveal that complexes 1 and 2 both are structurally trialkytin(IV) analogs with distorted trigonal bipyramidal geometry. The geometry around tin atom is constituted by three alkyl groups (methyl in complex 1 and butyl in com- plex 2) occupying the equatorial positions and two oxygen atoms of 4‐(3‐chloro‐ 2‐methylphenylamino)‐4‐oxobut‐2‐enoic acid ligand occupying the axial posi- tions. The computational study was performed applying LANL2DZ (Los Alamos National Laboratory 2 Double‐Zeta) functional with B3LYP (Lee, Yang and Parr) level of theory to obtain the optimized geometry, spectroscopic analysis, frontier molecular orbitals as well as global and local reactivity. A good correlation was found between the experimental and computational results. The homogeneous catalytic performance of synthesized compounds was evaluated for the transesterification of corn oil with methanol into biodiesel. The obtained corn oil biodiesel (COB) was confirmed by FT‐IR, 1 H NMR and GC–MS. The catalytic results revealed that the complexes were active at optimized conditions and therefore can be potential candidates for the development of new catalytic sys- tem for biodiesel production. KEYWORDS biodiesel formation, computational study, organotin (IV) complex, single crystal structure, spectroscopic characterization 1 | INTRODUCTION The increase consumption of fossil fuels has been causing environmental as well as economic problems. In order to condense the dependency on fossil fuels, the advancement in the renewable energy source (fuel) in particular biodie- sel is indeed very significant. [1] The biodiesel fuel has many advantages like high biodegradability, renewability and Received: 25 June 2019 Revised: 21 August 2019 Accepted: 18 September 2019 DOI: 10.1002/aoc.5305 Appl Organometal Chem. 2019;e5305. https://doi.org/10.1002/aoc.5305 © 2019 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/aoc 1 of 16