The Platinum Center is a Stronger Nucleophile than the Free Nitrogen Donors in a Dimethylplatinum Complex with a Dipyridylpyridazine Ligand

Abstract

The ligand 1,4-di-2-pyridyl-5,6,7,8,9,10-hexahydrocycloocta­[d]­pyridazine (6-dppd) contains two potential chelate groups, but it coordinates to only one dimethylplatinum group in forming the complex [PtMe2(6-dppd)], 1. Complex 1 contains a free pyridyl and a free pyridazine nitrogen donor, but it fails to coordinate to ZnCl2 or to CuCl to give a bimetallic complex. Complex 1 reacted with mercury­(II) salts HgX2 (X = Cl, Br, OAc), not by coordination but by oxidative addition to the dimethylplatinum­(II) center to give the platinum­(IV) complexes [PtX­(HgX)­Me2(6-dppd)]. Complex 1 reacted with bromine or iodine by trans oxidative addition to give [PtX2Me2(6-dppd)], X = Br or I, but, when X = I, a more complex sequence of reactions also gave rise to products of cis oxidative addition and to the products [PtIMe3(6-dppd)] and [PtI3Me­(6-dppd)], which arise through a methyl group transfer reaction. Complex 1 reacted with alkyl halides RX by trans oxidative addition to give [PtXRMe2(6-dppd)], R = Me, X = I; R = CH2Ph, X = Br; R = CH2-4-C6H4-CH2Br, X = Br. The cleavage of methyl groups from complex 1 by DCl gave a mixture of all isotopomers of methane, CH4–n D n , indicating ready equilibration between hydrido­(methyl)­platinum­(IV) and methaneplatinum­(II) complex intermediates.

Reactivity comparison of five-and six-membered cyclometalated platinum(ii) complexes in oxidative addition reactions

“…[6][7][8][9][10][11] One candidate for obtaining a six-membered cyclometalated complex It has been well established that cyclometalated platinum(II) complexes that possess nitrogen and phosphorus donor ligands are highly reactive toward oxidative addition reactions. [22][23][24] This article describes the synthesis of a new, six-membered, cyclometalated platinum(II) complex [PtMe(bzpy)(PPh 3 )], in which bzpy = 2benzylpyridinate, and the study of the reactivity of this complex toward methyl iodide, which is a typical electrophile in oxidative addition reactions. In this regard, it is possible to incorporate many functional groups into the alkyl group for preparation of supra molecular materials and photoactive complexes.…”

Supramolecular Organoplatinum(IV) Chemistry: Dimers and Polymers Formed by Intermolecular Hydrogen Bonding

“…The 1 H NMR spectrum of complex 6 contained a single methylplatinum resonance at δ = 1.44 with 2 J PtH = 80 Hz, in the range expected for a platinum(II) complex. 7 A minor product, formed in about 10% yield, was characterized by methylplatinum resonances at δ = 2.03 and 2.29, with 2 J (PtH) = 70 and 71 Hz respectively, similar to values for complex 2a , suggesting that this complex could be 5 . However, it could not be purified and the spectrum was not fully resolved, so the structural assignment is tentative.…”

“…The structure of complex 6 was determined and is shown in Figure 1, confirming that the complex is formed selectively with the methyl group trans to pyridine. 7…”

“…Complex 1 was prepared as previously reported. 7 NMR spectra were recorded using Varian Mercury 400 or Varian Inova 400 or 600 spectrometers. Complete assignment of each compound was aided by the use of 1 H– 1 H NOESY, 1 H– 13 C{ 1 H}-HSQC, and 1 H– 1 H gCOSY experiments as required.…”

“…7 It was not possible to add a second platinum(II) unit to complex 1 , and the platinum center was shown to be a stronger nucleophile than either of the free nitrogen donors, as illustrated by the oxidative addition of benzyl bromide (Scheme 3). 7 A similar oxidative addition of alkyl bromides with hydrogen bonding donors as substituents then should allow self-assembly through OH···O (compare Scheme 1), OH···Br (compare Scheme 2), or OH···N hydrogen bonding. This article presents the results of such a study, including examples of each type of the hydrogen bond.…”