TY - JOUR
T1 - Five-coordinate [PtII(bipyridine)2(phosphine)] n+ complexes
T2 - Long-lived intermediates in ligand substitution reactions of [Pt(bipyridine)2]2+ with phosphine ligands
AU - Lo, Warrick K.C.
AU - Cavigliasso, Germán
AU - Stranger, Robert
AU - Crowley, James D.
AU - Blackman, Allan G.
PY - 2014/4/7
Y1 - 2014/4/7
N2 - The reaction of [Pt(N-N)2]2+ [N-N = 2,2′-bipyridine (bpy) or 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me2bpy)] with phosphine ligands [PPh3 or PPh(PhSO3)22-] in aqueous or methanolic solutions was studied by multinuclear (1H, 13C, 31P, and 195Pt) NMR spectroscopy, X-ray crystallography, UV-visible spectroscopy, and high-resolution mass spectrometry. NMR spectra of solutions containing equimolar amounts of [Pt(N-N)2]2+ and phosphine ligand give evidence for rapid formation of long-lived, 5-coordinate [PtII(N-N)2(phosphine)]n+ complexes. In the presence of excess phosphine ligand, these intermediates undergo much slower entry of a second phosphine ligand and loss of a bpy ligand to give [Pt II(N-N)(phosphine)2]n+ as the final product. The coordination of a phosphine ligand to the Pt(II) ion in the intermediate [Pt(N-N)2(phosphine)]n+ complexes is supported by the observation of 31P-195Pt coupling in the 31P NMR spectra. The 5-coordinate nature of [Pt(bpy)2{PPh(PhSO 3)2}] is confirmed by X-ray crystallography. X-ray crystal structural analysis shows that the Pt(II) ion in [Pt(bpy) 2{PPh(PhSO3)2}]·5.5H2O displays a distorted square pyramidal geometry, with one bpy ligand bound asymmetrically. These results provide strong support for the widely accepted associative ligand substitution mechanism for square planar Pt(II) complexes. X-ray structural characterization of the distorted square planar complex [Pt(bpy)(PPh3)2](ClO4)2 confirms this as the final product of the reaction of [Pt(bpy)2]2+ with PPh3 in CD3OD. The results of density functional calculations on [Pt(bpy)2]2+, [Pt(bpy) 2(phosphine)]n+, and [Pt(bpy)(phosphine)2] n+ indicate that the bonding energy follows the trend of [Pt(bpy)(phosphine)2]n+ > [Pt(bpy) 2(phosphine)]n+ > [Pt(bpy)2]2+ for stability and that the formation reactions of [Pt(bpy) 2(phosphine)]n+ from [Pt(bpy)2]2+ and [Pt(bpy)(phosphine)2]n+ from [Pt(bpy) 2(phosphine)]n+ are energetically favorable. These calculations suggest that the driving force for the formation of [Pt(bpy)(phosphine)2]n+ from [Pt(bpy)2] 2+ is the formation of a more energetically favorable product.
AB - The reaction of [Pt(N-N)2]2+ [N-N = 2,2′-bipyridine (bpy) or 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me2bpy)] with phosphine ligands [PPh3 or PPh(PhSO3)22-] in aqueous or methanolic solutions was studied by multinuclear (1H, 13C, 31P, and 195Pt) NMR spectroscopy, X-ray crystallography, UV-visible spectroscopy, and high-resolution mass spectrometry. NMR spectra of solutions containing equimolar amounts of [Pt(N-N)2]2+ and phosphine ligand give evidence for rapid formation of long-lived, 5-coordinate [PtII(N-N)2(phosphine)]n+ complexes. In the presence of excess phosphine ligand, these intermediates undergo much slower entry of a second phosphine ligand and loss of a bpy ligand to give [Pt II(N-N)(phosphine)2]n+ as the final product. The coordination of a phosphine ligand to the Pt(II) ion in the intermediate [Pt(N-N)2(phosphine)]n+ complexes is supported by the observation of 31P-195Pt coupling in the 31P NMR spectra. The 5-coordinate nature of [Pt(bpy)2{PPh(PhSO 3)2}] is confirmed by X-ray crystallography. X-ray crystal structural analysis shows that the Pt(II) ion in [Pt(bpy) 2{PPh(PhSO3)2}]·5.5H2O displays a distorted square pyramidal geometry, with one bpy ligand bound asymmetrically. These results provide strong support for the widely accepted associative ligand substitution mechanism for square planar Pt(II) complexes. X-ray structural characterization of the distorted square planar complex [Pt(bpy)(PPh3)2](ClO4)2 confirms this as the final product of the reaction of [Pt(bpy)2]2+ with PPh3 in CD3OD. The results of density functional calculations on [Pt(bpy)2]2+, [Pt(bpy) 2(phosphine)]n+, and [Pt(bpy)(phosphine)2] n+ indicate that the bonding energy follows the trend of [Pt(bpy)(phosphine)2]n+ > [Pt(bpy) 2(phosphine)]n+ > [Pt(bpy)2]2+ for stability and that the formation reactions of [Pt(bpy) 2(phosphine)]n+ from [Pt(bpy)2]2+ and [Pt(bpy)(phosphine)2]n+ from [Pt(bpy) 2(phosphine)]n+ are energetically favorable. These calculations suggest that the driving force for the formation of [Pt(bpy)(phosphine)2]n+ from [Pt(bpy)2] 2+ is the formation of a more energetically favorable product.
UR - http://www.scopus.com/inward/record.url?scp=84897994553&partnerID=8YFLogxK
U2 - 10.1021/ic403089j
DO - 10.1021/ic403089j
M3 - Article
SN - 0020-1669
VL - 53
SP - 3595
EP - 3605
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 7
ER -