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Characterising Lone‐Pair Activity of Lead(II) by 207 Pb Solid‐State NMR Spectroscopy: Coordination Polymers of [N(CN) 2 ] − and [Au(CN) 2 ] − with Terpyridine Ancillary Ligands
Author(s) -
Greer Brandon J.,
Michaelis Vladimir K.,
Katz Michael J.,
Leznoff Daniel B.,
Schreckenbach Georg,
Kroeker Scott
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002913
Subject(s) - chemistry , terpyridine , crystallography , lone pair , chemical shift , nuclear magnetic resonance spectroscopy , nmr spectra database , coordination complex , ligand (biochemistry) , coordination sphere , coordination number , spectroscopy , molecule , stereochemistry , spectral line , metal , crystal structure , ion , organic chemistry , biochemistry , physics , receptor , astronomy , quantum mechanics
A series of lead(II) coordination polymers containing [N(CN) 2 ] − (DCA) or [Au(CN) 2 ] − bridging ligands and substituted terpyridine (terpy) ancillary ligands ([Pb(DCA) 2 ] ( 1 ), [Pb(terpy)(DCA) 2 ] ( 2 ), [Pb(terpy){Au(CN) 2 } 2 ] ( 3 ), [Pb(4′‐chloro‐terpy){Au(CN) 2 } 2 ] ( 4 ) and [Pb(4′‐bromo‐terpy)(μ‐OH 2 ) 0.5 {Au(CN) 2 } 2 ] ( 5 )) was spectroscopically examined by solid‐state 207 Pb MAS NMR spectroscopy in order to characterise the structural and electronic changes associated with lead(II) lone‐pair activity. Two new compounds, 2 and [Pb(4′‐hydroxy‐terpy){Au(CN) 2 } 2 ] ( 6 ), were prepared and structurally characterised. The series displays contrasting coordination environments, bridging ligands with differing basicities and structural and electronic effects that occur with various substitutions on the terpyridine ligand (for the [Au(CN) 2 ] − polymers). 207 Pb NMR spectra show an increase in both isotropic chemical shift and span ( Ω ) with increasing ligand basicity (from δ iso =−3090 ppm and Ω =389 ppm for 1 (the least basic) to δ iso =−1553 ppm and Ω =2238 ppm for 3 (the most basic)). The trends observed in 207 Pb NMR data correlate with the coordination sphere anisotropy through comparison and quantification of the PbN bond lengths about the lead centre. Density functional theory calculations confirm that the more basic ligands result in greater p‐orbital character and show a strong correlation to the 207 Pb NMR chemical shift parameters. Preliminary trends suggest that 207 Pb NMR chemical shift anisotropy relates to the measured birefringence, given the established correlations with structure and lone‐pair activity.