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Phosphine and Phosphonite Complexes of a Ruthenium(II) Porphyrin. 1. Synthesis, Structure, and Solution State Studies

Phosphine and Phosphonite Complexes of a Ruthenium(II) Porphyrin. 1. Synthesis, Structure, and Solution State Studies
Phosphine and Phosphonite Complexes of a Ruthenium(II) Porphyrin. 1. Synthesis, Structure, and Solution State Studies
We have investigated the effect of complexation of different phosphorus ligands on the stability, solid state structure,and spectroscopic properties (NMR, IR, UV-vis) of a 5,15-diphenyl-substituted ruthenium porphyrin, (MeOH)RuII-(CO)(DPP) 2 [DPP ) 5,15-bis(3',5'-di-tert-butyl)phenyl-2,8,12,18-tetraethyl-3,7,13,17-tetramethylporphyrin]. The ligands used are PPh3, diphenyl(phenylacetenyl)phosphine (DPAP), bis(diphenylphosphino)acetylene (DPPA), tris-(phenylacetenyl)phosphine [(PA)3P], and diethyl (phenylacetenyl)phosphonite [PAP(OEt)2]. The mono-phosphine complexes (PR3)RuII(CO)(DPP) are readily formed in solution in quantitative yields. The complexes display association constants ranging from 1.2 × 104 M-1 for PPh3 to 4.8 × 106 M-1 for PAP(OEt)2. The weak association of PPh3 does not correlate with its pKa, δ(31P), or cone angle value and is attributed to steric effects. Due to their kinetic lability, which is shown by 2D NMR spectroscopy, and the weakening of the carbonyl ligand via a trans effect, themono-phosphine complexes could not be isolated. IR spectroscopy gives the relative order of π-acceptor strength as PPh3 < DPAP, DPPA < (PA)3P < PAP(OEt)2, whereas the relative order of the σ-donor strength is PPh3 <(PA)3P < DPAP, DPPA < PAP(OEt)2, based on the calculated pKa values and on the 31P{1H} NMR chemical shifts of the ligands. The chemical shift differences in the 31P{1H} NMR spectra upon ligand binding display a linear correlation with the calculated pKa values of the protonated ligands HPR3+; we propose that the pKa, and probably other electronic properties, of a specific phosphorus ligand can be estimated on the basis of the chemical shift difference Δδ(31P) upon complexation to a metalloporphyrin. The bis-phosphine complexes can be isolated in pureform by crystallization from CHCl3-MeOH solutions using excess ligand. Association of the second ligand is in the same order of magnitude as the first binding for the phosphines, but the second phosphonite binding is decreased by a factor of about 100. The solid state structures show only marginal differences in the geometrical parameters. The calculated and the crystallographic cone angles of the ligands generally do not match, apart from the values obtained for PAP(OEt)2.
0020-1669
5255-5268
Stulz, Eugen
9a6c04cf-32ca-442b-9281-bbf3d23c622d
Maue, Michael
13d5359d-0b30-4815-a1cd-8170e02e7a96
Feeder, Neil
f72b9f0c-f7a0-4d4a-9aa0-4654bd85c386
Teat, Simon J.
fd6e6d90-b0c2-4463-91d2-5c72e212d414
Ng, Yiu-Fai
e09b2546-48dc-4e23-af7d-62f109b46ba8
Bond, Andrew D.
94b1c5ea-ac6f-4062-9673-13064c82aeee
Darling, Scott L.
fbef4b54-4f6b-4528-adcd-987af79826e1
Sanders, Jeremy K.M.
a676d635-3196-437a-b894-a2bc5f857ae2
Stulz, Eugen
9a6c04cf-32ca-442b-9281-bbf3d23c622d
Maue, Michael
13d5359d-0b30-4815-a1cd-8170e02e7a96
Feeder, Neil
f72b9f0c-f7a0-4d4a-9aa0-4654bd85c386
Teat, Simon J.
fd6e6d90-b0c2-4463-91d2-5c72e212d414
Ng, Yiu-Fai
e09b2546-48dc-4e23-af7d-62f109b46ba8
Bond, Andrew D.
94b1c5ea-ac6f-4062-9673-13064c82aeee
Darling, Scott L.
fbef4b54-4f6b-4528-adcd-987af79826e1
Sanders, Jeremy K.M.
a676d635-3196-437a-b894-a2bc5f857ae2

Stulz, Eugen, Maue, Michael, Feeder, Neil, Teat, Simon J., Ng, Yiu-Fai, Bond, Andrew D., Darling, Scott L. and Sanders, Jeremy K.M. (2002) Phosphine and Phosphonite Complexes of a Ruthenium(II) Porphyrin. 1. Synthesis, Structure, and Solution State Studies. Inorganic Chemistry, 41 (20), 5255-5268. (doi:10.1021/ic025727y).

Record type: Article

Abstract

We have investigated the effect of complexation of different phosphorus ligands on the stability, solid state structure,and spectroscopic properties (NMR, IR, UV-vis) of a 5,15-diphenyl-substituted ruthenium porphyrin, (MeOH)RuII-(CO)(DPP) 2 [DPP ) 5,15-bis(3',5'-di-tert-butyl)phenyl-2,8,12,18-tetraethyl-3,7,13,17-tetramethylporphyrin]. The ligands used are PPh3, diphenyl(phenylacetenyl)phosphine (DPAP), bis(diphenylphosphino)acetylene (DPPA), tris-(phenylacetenyl)phosphine [(PA)3P], and diethyl (phenylacetenyl)phosphonite [PAP(OEt)2]. The mono-phosphine complexes (PR3)RuII(CO)(DPP) are readily formed in solution in quantitative yields. The complexes display association constants ranging from 1.2 × 104 M-1 for PPh3 to 4.8 × 106 M-1 for PAP(OEt)2. The weak association of PPh3 does not correlate with its pKa, δ(31P), or cone angle value and is attributed to steric effects. Due to their kinetic lability, which is shown by 2D NMR spectroscopy, and the weakening of the carbonyl ligand via a trans effect, themono-phosphine complexes could not be isolated. IR spectroscopy gives the relative order of π-acceptor strength as PPh3 < DPAP, DPPA < (PA)3P < PAP(OEt)2, whereas the relative order of the σ-donor strength is PPh3 <(PA)3P < DPAP, DPPA < PAP(OEt)2, based on the calculated pKa values and on the 31P{1H} NMR chemical shifts of the ligands. The chemical shift differences in the 31P{1H} NMR spectra upon ligand binding display a linear correlation with the calculated pKa values of the protonated ligands HPR3+; we propose that the pKa, and probably other electronic properties, of a specific phosphorus ligand can be estimated on the basis of the chemical shift difference Δδ(31P) upon complexation to a metalloporphyrin. The bis-phosphine complexes can be isolated in pureform by crystallization from CHCl3-MeOH solutions using excess ligand. Association of the second ligand is in the same order of magnitude as the first binding for the phosphines, but the second phosphonite binding is decreased by a factor of about 100. The solid state structures show only marginal differences in the geometrical parameters. The calculated and the crystallographic cone angles of the ligands generally do not match, apart from the values obtained for PAP(OEt)2.

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Published date: 2002

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Local EPrints ID: 41343
URI: http://eprints.soton.ac.uk/id/eprint/41343
ISSN: 0020-1669
PURE UUID: 0fe17223-d870-46ae-adc8-c541627e8f8e
ORCID for Eugen Stulz: ORCID iD orcid.org/0000-0002-5302-2276

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Date deposited: 23 Aug 2006
Last modified: 27 Jul 2022 01:41

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Author: Eugen Stulz ORCID iD
Author: Michael Maue
Author: Neil Feeder
Author: Simon J. Teat
Author: Yiu-Fai Ng
Author: Andrew D. Bond
Author: Scott L. Darling
Author: Jeremy K.M. Sanders

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