Platinum(II) complexes with aryl tellurols and diaryl ditellurides: Syntheses and spectral investigations

Abstract

Arytellurol complexes [PtCl(TeAr)(PPh 3) 2] ( I) and [Pt(TeAr) 2(PPh 3) 2] ( II) are readily obtained from cis-[PtCl 2(PPh) 3) 2] and NaTeAr (Ar = C 6H 5, 4-CH 3OC 6H 4 and 4-CH 3CH 2OC 6H 4) in ethanolbenzene at room temperature. 31P NMR spectra of ( I) and ( II) indicate their trans configuration in solution. Metathetical reactions between I (Ar = 4-CH 3OC 6H 4) and NaX (X = I, Br, SCN) occur in methanol to give [Pt(X)(TeC 6H 4OCH 3-4)(PPh 3) 2]. 1H NMR shows that equimolar proportions of NaTeC 6H 5, NaTeC 6H 4OCH 2CH 3-4 and cis-[PtCl 2(PPh 3) 2] give a mixture of three complexes: II, Ar = C 6H 5; II, Ar = 4-CH 3CH 2OC 6H 4; and [Pt(TeC 6H 5)(TeC 6H 4OCH 2CH 3-4)(PPh 3) 2]. Polymeric complexes [PtCl(TeAr)] n ( III) and [Pt(TeAr) 2] n ( IV) result from reaction between K 2[PtCl 4] and NaTeAr in aqueaous ethanol. They react with excess of PPh 3 in CDCl 3 to yield monomeric complexes I and II respectively which were characterized in situ by 1H and 31P NMR of the reaction mixtures. IR spectra indicate the presence of bridging chloride ligands in III. An alternating chloride and tellurol bridged chain structure for III and a tellurol bridged for IV have been proposed. Reaction between equimolar amounts of III and PPh 3 in dichloromethane yielded a tellurol bridged dimeric complex [PtCl(μ-TeAr)(PPh 3)] 2 ( V) with terminal chloride ligand as suggested by IR study. Ethanolic solutions of diarylditellurides also react readily with an aqueous solution of K 2[PtCl 4] at 10 °C to give complexes for which the structure trans-[PtCl 2(ArTeTeAr) 2] ( VI) is suggested from their elemental analyses, IR, Raman (in one case only), 1H, 125Te (in one case only), and 195Pt NMR spectra and reactions with triphenylphosphine which liberated free ditellurides. At 40 °C or above the same ditellurides form polymeric complexes III with K 2[PtCl 4] in aquaeous ethanol.