Natalie Fey CombeDay, 8 January 2004 University of Southampton

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Natalie FeyCombeDay, 8 January 2004 _at_ University
of Southampton

• Development of a Ligand Knowledge Base for
  Phosphorus Ligands

2
Overview

• Introduction
• Computational Approach
• Statistical Analysis
• Results
• Challenges
• Outlook

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Introduction

• Ligand Knowledge Base
• mine CSD and other databases
• geometry of metal complexes (bond lengths,
  angles, conformations)
• supramolecular interactions
• experimental data
• supplement by calculated data
• geometry, conformational freedom
• electronic structure
• transition states
• complexes not structurally characterised

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Introduction

• Phosphorus Ligands, PX3 (X R, Hal, Ar, OR, OAr,
  NR2, mixed)
• widespread use as ligands in transition metal
  complexes
• tune steric and electronic properties
• importance in homogeneous catalysis
• established measures of steric and electronic
  properties
• steric Tolmans cone angle, solid angle, Browns
  steric parameter, Orpens S4 parameter
• electronic Tolmans electronic parameter (?CO),
  pKa, PA, IE, EB, CB, ?CO
• Tolman, Brown, QALE (Prock, Giering)

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Computational Approach

• Problems with TM Complexes
• treatment of large numbers of electrons, electron
  correlation
• geometrical effects of partially filled
  d-orbitals (spin states, Jahn-Teller effects)
• variable coordination numbers and modes
• suitable data for verification
• Density Functional Theory
• Jaguar, BP86/6-31G on ligands, LACV3P on metal

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Computational Approach

• Phosphorus Ligands
• alkyl phosphines, PR3 (R H, Me, Et, Pr, iPr,
  Bu, tBu, Cy, CF3, asymmetric 1, 2, 3)
• aryl phosphines, PAr3 (Ar Ph, o-tolyl, p-tolyl,
  p-F-Ph, p-(MeO)-Ph, p-Cl-Ph, p-(CF3)-Ph,
  p-(Me2N)-Ph, C6F5 , 3,5-(CF3)2-Ph), model CHCH2
• phosphine halides, PHal3 (Hal F, Cl)
• phosphites, POR3 (R Me, Et, Ph, 4)
• amino phosphines, PNR2 (R H, Me cyclic NC4H4,
  NC4H8, NC5H10)
• mixed halides (PH2Hal, PHHal2, PMe2Hal, PMeHal2,
  Hal F, Cl, CF3 (Me only))

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Computational Approach

• Complexes
• free ligand (PX3)
• phosphorus ligand cation (HPX3)
• H3B(PX3)
• OPX3
• (PH3)5Mo(PX3)
• Cl3Pd(PX3)-
• (PH3)3Pt(PX3)

• Variables
• energetic EHOMO, ELUMO, PA, BDE, He(steric)
• NBO charges of MLn fragments coordinated to PX3
• geometrical ?(P-X), ?(X-P-X), d(P-M), geometry
  of M-L fragment (cis, trans effects, L-M-L)

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Statistical Analysis

• Bivariate Correlations
• linear, non-linear
• Hierarchical Clustering
• identify groups by measuring distance in
  multi-dimensional space
• Principal Component Analysis
• reduce number of variables by formulation of
  principal components (linear combinations of
  variables which account for maximum of variation
  in original variables)
• chemical interpretation of PCs? (steric,
  electronic (?, ?))

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Results

• Pearson Correlations
• identify linearly correlated variables
• use to reduce number of variables
• fewer complexes to optimise
• simplify interpretation of PCs
• e.g. Cl3Pd(PX3)- and (PH3)3Pt(PX3)

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Results

• Hierarchical Cluster
• (Pearson Correlation, STD1, B Pt data)

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Principal Component Analysis (excl. mixed
Halides)
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Principal Component Analysis (excl. mixed
Halides)
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Principal Component Analysis
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Principal Component Analysis
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Principal Component Analysis (excl. mixed
Halides)
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Principal Component Analysis
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Challenges

• selection of complexes and variables
• treatment of bidentate phosphorus ligands
• expansion to other ligand sets
• chemical interpretation of principal components
• steric and electronic effects contribute to
  variables
• reliability of established measures (cone angles)
• robustness of analysis
• variation in ligand set and variables (high
  correlation)
• exploration of conformational space
• treatment of multiple minima
• automation of calculations, data analysis,
  statistical analysis
• eliminate data transfer mistakes
• reliable error behaviour

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Outlook

• started expansion of ligand sets
• explore model building
• predict experimental and calculated data from
  subset of variables
• linear, non-linear
• explore measures of quantum similarity (Fukui
  function, HSAB)

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Acknowledgements

• Guy Orpen, Jeremy Harvey
• Athanassios Tsipis, Stephanie Harris
• Funding