| Abstract
| - A new methodology for the preparation of two series of cationic organoplatinum(II)complexes with hydrogen-bonding functionality is described. The mononuclear complexesof the type trans-[Pt(σ-aryl)L(PPh3)2]OTf (L = nicotinic acid, aryl = C3-benzoic acid (9) orC4-benzoic acid (10); L = isonicotinic acid, aryl = C3-benzoic acid (11) or C4-benzoic acid(12); OTf = trifluoromethanesulfonate (triflate)) constitute the first series, and the dinuclearcomplexes of the type trans-[Pt(σ-aryl)(PPh3)2(μ-L)Pt(σ-aryl)(PPh3)2](OTf)2 (L = 1,1-bis(4-pyridyl)ethene, aryl = C3-benzoic acid (19) or C4-benzoic acid (20); L = 4,7-phenanthroline,aryl = C3-benzoic acid (21) or C4-benzoic acid (22); L = 4,4‘-bipyridine, aryl = C3-benzoicacid (23) or C4-benzoic acid (24)) constitute the second series. The methodology describedhere involves the protection of the carboxylic acid group of a 3- or 4-iodobenzoic acid precursoras the tert-butyldiphenylsilyl ester, followed by an oxidative addition reaction of the C−Ibond with the Pt(0) species Pt(PPh3)4 to yield the key (σ-aryl)iodoplatinum(II) intermediates3 and 4, the structures of which were determined by X-ray crystallography. Subsequenttreatment of these products with AgOTf, followed by the addition of a suitable monodentateor bridging bidentate N-donor ligand and, finally, facile removal of the silyl protecting group(s) with HOTf affords the target complexes with hydrogen-bonding functionality in highyield. Variable-temperature 1H NMR experiments with the silyl-protected complexes trans-[Pt(σ-aryl)L(PPh3)2]OTf (aryl = C3-tert-butyldiphenylsilyl benzoate, L = nicotinic acid (5) orisonicotinic acid (7)) confirm that a dynamic intramolecular process involving the pyridylligand is occurring. The rotational barrier of a pyridyl ligand in an organoplatinum(II)complex is reported for the first time, where ΔG⧧ = 48.3 ± 0.9 and 45.7 ± 0.9 kJ mol-1 forcomplexes 5 and 7, respectively.
- A high-yielding methodology for the preparation of cationic, mono- and dinuclear organoplatinum(II) complexes with hydrogen-bonding functionality is described. The key steps involve the protection of the carboxylic acid group of an aryl iodide with the robust tert-butyldiphenylsilyl group prior to reaction with a platinum(0) precursor, followed by metathesis of the iodo ligand in the resulting (σ-aryl)iodoplatinum(II) species with a suitable monodentate or bridging bidentate N-donor ligand and, finally, removal of the silyl protecting group(s) using HOTf.
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