Platinum(iv)-mediated hydrolysis of nitriles giving metal-bound iminols

The complexes K 2 [PtCl n ] (n = 4 or 6) react with pyrazoles 3,5 MeRpzH (R = H or Me) in 0.1 M HCl at 20-25 °C to form the isomerically pure cis [PtCl n (3,5 MeRpzH) 2 ] complexes (n = 2 or 4) (1a,b and 3a,b), whereas a decrease in the acidity of the medium leads to a substantial decrease in selectivity of the reaction. Thermal isomerization of complexes 1a,b and 3a,b both in solution (MeNO 2 ) and in the solid state affords the trans [PtCl n (3,5 MeRpzH) 2 ] complexes (n = 2 or 4) (2a,b and 4a,b). Platinum(II) complexes 1a,b and 2a,b were also prepared by selective reduction of genetically related Pt IV compounds (3a,b and 4a,b) with the phosphorus ylide Ph 3 P=CHCO 2 Me in chloroform. Platinum(IV) complexes (3a,b and 4a,b) were synthesized by oxidation of the corresponding Pt II complexes (1a,b and 2a,b) with mo lecular chlorine. X ray diffraction study demonstrated that coordination of 3(5) MepzH to Pt IV in complex 4a stabilizes the sterically least hindered tautomer in the solid state.Preparative coordination chemistry of pyrazoles is rather versatile due to the presence of two nucleophilic centers in these compounds and the possibility of easily changing the electronic and steric properties of the rings by introducing various substituents. The ability of pyrazoles to act as neutral and anionic monodentate and exo or endo bidentate ligands opens a route to numerous mono or polynuclear complexes. 1-4 Many such compounds have ferromagnetic properties, serve as luminophores, and ex hibit catalytic, antibacterial, antifungal, antiproliferative, antiviral, and antitumor activities (see the reviews 1-4 and references herein). These complexes are studied and used as light emitting diodes, pH sensors, anionic receptors, synthons in supramolecular and coordination chemistry, models of the active sites of metalloenzymes and metallo proteins, and models for studying homogeneous catalysis (see the reviews 1-4 and references herein). In particular, pyrazole containing platinum(II) complexes are exten sively studied and/or used as luminescence sensors, 5,6 reagents in preparative coordination chemistry, 7-10 and antitumor agents. 11-13In platinum chemistry, the geometric configuration of complexes is of particular importance for the prediction of their properties and, correspondingly, for the determi nation of the field of their application. This is associated with the difference in the reactivity and biological activity of cis and trans isomers. 14-17 Generally, platinum(II) com plexes with N donor ligands in the cis configuration ex hibit much higher antitumor activity than their trans ana logs. 18 At the same time, the molecular design and syn thesis of some polynuclear complexes require the use of precursors in the trans form. 7 For pyrazole containing complexes, this is true for the platinum(II) compound cis [PtCl 2 (pzH) 2 ] (pzH is pyrazole), which displays con siderable antitumor activity. 11 The trans isomer of this compound is a convenient synthon for the preparation of polynuclear complexes. 7In spite of the f...

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“…29 We synthesized the isomerically pure compounds Both reactions gave the products in nearly 100% yields.…”

Section: Resultsmentioning

confidence: 99%

Directed synthesis of isomerically pure platinum pyrazole complexes

2006

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“…37 Elemental analysis was car ried out on a Carlo Erba Instruments TCM 480 instrument. The IR spectra (KBr pellets) were measured on a Nicolet Impact 400 instrument in the 4000-400 cm -1 region.…”

Section: Methodsmentioning

confidence: 99%

Hetarylamidines derived from PtIV-mediated coupling of nitriles with aminoheterocycles

et al. 2006

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The trans [PtCl 4 (EtCN) 2 ] complex is involved in coupling reactions (CH 2 Cl 2 , 30-35 °C, 10-15 min) with 2 amino derivatives of heterocyclic compounds (2 NH 2 Het, where Het is pyridyl, 4 methylpyridyl, 5 methylpyridyl, 6 methylpyridyl, or thiazolyl) to form the trans [PtCl 4 {N(H)=C(Et)NHHet} 2 ] complexes (1-5) with κ 1 (N ) coordinated hetarylamidine ligands. The reaction with the use of 2 aminopyrimidine (2 NH 2 Pym) produces the [PtCl 4 (2 NH 2 Pym) 2 ] complex (6) as a result of complete replacement of the nitrile ligands in the [PtCl 4 (EtCN) 2 ] complex. The compositions and structures of compounds 1-6 were con firmed by elemental analysis (C, H, N), IR spectroscopy, 1 H, 13 C{ 1 H}, and 195 Pt{ 1 H} NMR spectroscopy, and FAB mass spectrometry. Complex 1 was additionally characterized by X ray diffraction.

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“…The starting material, trans-[PtCl 4 (EtCN) 2 ], was obtained by the known procedure [5], and nitronate 1 (Scheme 1) was synthesized from b-nitro-4-methoxystyrene and isobutylene by the literature method [6]. Reaction between trans-[PtCl 4 (EtCN) 2 ] and 1 proceeds at room temperature for 12 h and gives N-acylimine complex 2 as the major product, when the synthesis was carried out in freshly distilled CH 2 Cl 2 [7].…”

Section: Introductionmentioning

confidence: 99%

“…2; IUPAC [4] name: 4-(4-methoxy-phenyl)-6,6-dimethyl-5,6-dihidro-4H-[1,2] oxazin-2-oxide) with EtCN in trans-[PtCl 4 (EtCN) 2 ] insofar as it was previously demonstrated that the ligation of nitriles to a Pt IV center ought to provide even a higher activation effect upon cycloaddition in comparison with the introduction of such powerful electron-acceptor group R as CF 3 to RCN [3]. To our knowledge, this report covers the first example of any reaction between a nitronate and a nitrile and it makes known that the interaction becomes possible in a metal-mediated reaction.The starting material, trans-[PtCl 4 (EtCN) 2 ], was obtained by the known procedure [5], and nitronate 1 (Scheme 1) was synthesized from b-nitro-4-methoxystyrene and isobutylene by the literature method [6]. Reaction between trans-[PtCl 4 (EtCN) 2 ] and 1 proceeds at room temperature for 12 h and gives N-acylimine complex 2 as the major product, when the synthesis was carried out in freshly distilled CH 2 Cl 2 [7].…”

mentioning

confidence: 99%