Chelate-stabilised primary, secondary, and tertiary alcohol and alkoxo platinum(II) complexes. X-Ray crystal structure of [Pt(Ph2PCH2CH2O)2]·H2O

Abstract

The co-ordination chemistry of the phosphino alcohols Ph₂PCH₂CHROH, R = Me (1b) or H (1c), with platinum(II) is reported. Ligands (1b), (1c) form the neutral complexes cis-[PtCl₂(Ph₂PCH₂CHROH)₂], R = Me (4b) or H (4c), which remain unchanged in CDCl₃. However, in CD₃OD the fluxional chelate [[graphic omitted]H)(Ph₂PCH₂CHMeOH)]Cl (2b) is formed. The bis(alcohol) complex [[graphic omitted]H)₂][ClO₄]₂(5b) is made by treatment of (4b) with AgClO₄. Deprotonation of (4b) with NEt₃ or (4c) with NaOH gives the bis(alkoxo) species [[graphic omitted])₂], R = Me (3b) or H (3c), quantitatively. Treatment of (4c) with NEt₃ gives a complex which in solution has the fluxional, binuclear, unsymmetrically alkoxo-bridged structure [[graphic omitted])₂(Ph₂PCH₂CH₂OH)₂]Cl₂(6) and in the solid state probably has the mononuclear structure [[graphic omitted])(Ph₂PCH₂CH₂OH)](8). The effect of the methyl substituents in the ligand backbone is discussed. Phosphorus-31 n.m.r. evidence shows that the order of trans influence of alkoxo ligands is 3° > 2° > 1° but the differences are small. The X-ray structure determination of (3c)(R= 0.038 for 1 885 observed diffractometer-measured reflections) shows square planar co-ordination about Pt, with normal Pt–P [2.228(2)Å] and Pt–O [2.039(5)Å] distances. It is concluded that the stability of the chelate alkoxo complexes is due to the conformation of the chelate ring making β-hydrogen elimination unfavourable.