2. Low-Dimensional Architectures in Isomeric cis-PtCl2{Ph2PCH2N(Ar)CH2PPh2} Complexes Using Regioselective-N(Aryl)-Group Manipulation
Peter De'Ath, Mark R J Elsegood, Noelia M Sanchez-Ballester, Martin B Smith Molecules. 2021 Nov 11;26(22):6809. doi: 10.3390/molecules26226809.
The solid-state behaviour of two series of isomeric, phenol-substituted, aminomethylphosphines, as the free ligands and bound to PtII, have been extensively studied using single crystal X-ray crystallography. In the first library, isomeric diphosphines of the type Ph2PCH2N(Ar)CH2PPh2 [1a-e; Ar = C6H3(Me)(OH)] and, in the second library, amide-functionalised, isomeric ligands Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2a-e; Ar = C6H3(Me)(OH)], were synthesised by reaction of Ph2PCH2OH and the appropriate amine in CH3OH, and isolated as colourless solids or oils in good yield. The non-methyl, substituted diphosphines Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2f, Ar = 3-C6H4(OH); 2g, Ar = 4-C6H4(OH)] and Ph2PCH2N(Ar)CH2PPh2 [3, Ar = 3-C6H4(OH)] were also prepared for comparative purposes. Reactions of 1a-e, 2a-g, or 3 with PtCl2(η4-cod) afforded the corresponding square-planar complexes 4a-e, 5a-g, and 6 in good to high isolated yields. All new compounds were characterised using a range of spectroscopic (1H, 31P{1H}, FT-IR) and analytical techniques. Single crystal X-ray structures have been determined for 1a, 1b∙CH3OH, 2f∙CH3OH, 2g, 3, 4b∙(CH3)2SO, 4c∙CHCl3, 4d∙½Et2O, 4e∙½CHCl3∙½CH3OH, 5a∙½Et2O, 5b, 5c∙¼H2O, 5d∙Et2O, and 6∙(CH3)2SO. The free phenolic group in 1b∙CH3OH, 2f∙CH3OH,2g, 4b∙(CH3)2SO, 5a∙½Et2O, 5c∙¼H2O, and 6∙(CH3)2SO exhibits various intra- or intermolecular O-H∙∙∙X (X = O, N, P, Cl) hydrogen contacts leading to different packing arrangements.
3. Mechanism of O2 activation and methanol production by (di(2-pyridyl)methanesulfonate)Pt(II)Me(OH(n))((2-n)-) complex from theory with validation from experiment
Wei-Guang Liu, Anna V Sberegaeva, Robert J Nielsen, William A Goddard 3rd, Andrei N Vedernikov J Am Chem Soc. 2014 Feb 12;136(6):2335-41. doi: 10.1021/ja409036c. Epub 2014 Feb 3.
The mechanism of the (dpms)Pt(II)Me(OH(n))((2-n)-) oxidation in water to form (dpms)Pt(IV)Me(OH)2 and (dpms)Pt(IV)Me2(OH) complexes was analyzed using DFT calculations. At pH < 10, (dpms)Pt(II)Me(OH(n))((2-n)-) reacts with O2 to form a methyl Pt(IV)-OOH species with the methyl group trans to the pyridine nitrogen, which then reacts with (dpms)Pt(II)Me(OH(n))((2-n)-) to form 2 equiv of (dpms)Pt(IV)Me(OH)2, the major oxidation product. Both the O2 activation and the O-O bond cleavage are pH dependent. At higher pH, O-O cleavage is inhibited whereas the Pt-to-Pt methyl transfer is not slowed down, so making the latter reaction predominant at pH > 12. The pH-independent Pt-to-Pt methyl transfer involves the isomeric methyl Pt(IV)-OOH species with the methyl group trans to the sulfonate. This methyl Pt(IV)-OOH complex is more stable and more reactive in the Pt-to-Pt methyl-transfer reaction as compared to its isomer with the methyl group trans to the pyridine nitrogen. A similar structure-reactivity relationship is also observed for the S(N)2 functionalization to form methanol by two isomeric (dpms)Pt(IV)Me(OH)2 complexes, one featuring the methyl ligand trans to the sulfonate group and another with the methyl trans to the pyridine nitrogen. The barrier to functionalize the former isomer with the CH3 group trans to the sulfonate group is 2-9 kcal/mol lower. The possibility of the involvement of Pt(III) species in the reactions studied was found to correspond to high-barrier reactions and is hence not viable. It is concluded that the dpms ligand facilitates Pt(II) oxidation both enthalpically and entropically.
