849192-02-5Relevant articles and documents
Special effects of ortho-isopropylphenyl groups. Diastereoisomerism in platinum(II) and palladium(II) complexes of helically chiral PAr3 ligands
Baber, R. Angharad,Orpen, A. Guy,Pringle, Paul G.,Wilkinson, Matthew J.,Wingad, Richard L.
, p. 659 - 667 (2007/10/03)
The coordination chemistry of the four phosphines, P{C6H 3(o-CH3)(p-Z)}3 where Z = H (1a) or OMe (1b) and P{C6H3(o-CHMe2)(p-Z)}3 Z = H (1c) or OMe (1d) with platinum(II) and palladium(II) is reported. Mononuclear complexes trans-[PdCl2L2] (L = 1a,b) and trans-[PtCl 2L2] (L = 1a-c) have been prepared and the crystal structures of trans-[PdCl2(1b)2] and trans-[PtCl 2(1c)2] as their dichloromethane solvates have been determined. The structures show that in these complexes, the ligands adopt g+g+a conformations. Examination of the Cambridge Structural Database confirms this to be one of only two conformer types that tri-o-tolylphosphines adopt and the only viable conformer in 4 and 6 coordinate complexes. The binuclear complexes trans-[Pd2Cl4L 2] (L = 1c,d) are formed even when an excess of the bulky 1c,d is used in the synthesis and the crystal structure of trans-[Pd2Cl 4(1c)2] as its chloroform solvate is reported. Reaction of [PtCl2(NCBu1)2] with 1b-d in refluxing toluene gave the cycloplatinated species [Pt2Cl2(L - H) 2] where L - H is phosphine 1b-d deprotonated at one of the ortho-methyl carbon atoms. Variable temperature 31P and 1H NMR spectroscopy reveals that all the complexes reported are fluxional. The processes are analysed in terms of restricted P-C and P-M rotations that give rise to diastereoisomeric rotamers because of the helically chiral orientations of the aryl substituants. For the complexes of the bulky ligands 1c,d, rotation about the P-C bond is slow on the NMR timescale even up to 75°C. The crystal structure of the cyclometallated complex [Pt2Cl2(1d - H)2] has been determined. The Royal Society of Chemistry 2005.
