Year 2 Computational Chemistry Lab

Introduction

Modern chemists employ calculations side by side with wet chemistry. Calculations provide insight that is unobtainable experimentally. For example, stability comparisons for transition states and intermediates, animations of vibrational modes (observable and non-observable), electronic structure and geometric parameters. Because calculations are complex and many approximations are made, experiments are crucial in providing reference points for comparison.

  • What is in the lab:
    • In this lab you investigate four coordinate phosphine complexes of nickel(II).
    • for Ni(II) complexes there is a fine balance between forming cis-square planar, trans-square planar and tetrahedral geometries.
    • factors effecting the stability of each conformer are electronic structure, ligand type, ligand donating and accepting ability, ligand size and ligand chelating ability.
    • This lab partners with a first year synthetic lab where you synthesised and obtained UV-vis spectra from of a set of Ni(II) complexes.
    • You will now be carrying out and interpreting calculations on the models of these complexes NiCl2(PPh3)2 and NiCl2(dppe) (dppe=1,2-bis(diphenyl phosphino)ethane).
NiCl2dppe_makingNiCl2dppe_sample
  • Before the lab:
    • Revise your first year synthetic lab. Revise your first year computational lab. It is assumed you are familiar with this material.
    • context is extremely important in computational chemistry. Some core references are provided below.
    • R.G. Hayter and F.S. Humiec, Square-Planar-Tetrahedral Isomerism of Nickel Halide Complexes of Diphenylalkylphosphines, Inorg. Chem., 1965, 4 (12), pp1701-1706, DOI: 10.1021/ic50034a006
    • Joao A.S. Bomfim, Fabio P. de Souza, Carlos A.L. Filgueiras, Alexsandro G. de Sousa, Maria Teresa P. Gambardella, "Diphosphine complexes of nickel: analogies in molecular structures and variety in crystalline arrangement", Polyhedron, Volume 22, Issue 12, 15 June 2003, Pages 1567-1573. DOI:10.1016/S0277-5387(03)00263-8
    • N.N. Greenwood & A. Earnshaw, Nickel, Palladium and Platinum in Chemistry of the Elements, Butterworth Heinemann, Oxford, UK, 1998 pp 1144-1172
  • This lab is set-up such that:
    • in the first section you are shown how to run the calculations and interpret the results on tetrahedral and square planar complexes of [NiCl4]2-.
    • you must work through the first section carefully and in sequence, reading the explanations, otherwise you will get lost.important
    • in the second section the instructions are minimal and you need to apply the methods and knowledge learned from the first section to NiCl2(PPh3)2
    • and NiCl2(dppe).
    • the lab is assessed by a blackboard based quiz and by "samples" (unique codes called DOI's that link to your calculations). You can have a maximum of 4 attempts at the quiz (no exceptions). You need to submit your DOI's and and complete the quiz by 6pm on the Friday of your lab
  • Links and connections:
    • this lab links directly with your first and second year lectures on crystal field theory, molecular vibrations, UV-Vis spectroscopy, molecular orbital theory and coordination chemistry.
    • this area of chemistry is still active and of interest today! Consider for example the following recent publications
    • Homogeneous Hydrogenation and Isomerization of 1-Octene Catalyzed by Nickel(II) Complexes with Bidentate Diarylphosphane Ligands, Inorg. Chem., 2013, Vol 52 (14), pp 8190-8201, DOI:10.1021/ic400973t
    • Hybrid Network Formation via Halogen Bonding of the Neutral Bromo-Substituted Organic Molecules with Anionic Metal-Bromide Complexes, Cryst. Growth Des., 2012, Vol 12 (8), pp 4149-4156 DOI:10.1021/cg300654e