Synthesis of chelate stabilised alcohol– and alkoxo–platinum(II) complexes. X-Ray crystal structure of [Pt(PPh2CH2CMe2O)2]·3.5H2O

Abstract

Reaction of the new phosphine PPh₂CH₂CMe₂OH with platinum(II) chloro complexes gives complexes of formula [PtCl₂(PPh₂CH₂CMe₂OH)₂]. The cis isomer in CDCl₃ or CD₃OD solution is in the ionic, chelate form cis-[[graphic omitted]H)(PPh₂CH₂CMe₂OH)]Cl. At +25 °C, rapid intramolecular –OH exchange takes place. Addition of AgClO₄ gives the bis-chelate cis-[[graphic omitted]H)₂][ClO₄]₂. Both of these cis species can be readily deprotonated to give the very stable bis(alkoxo) complex [[graphic omitted])₂]. The X-ray structure of this bis(alkoxo) complex as its 3.5H₂O solvate has been determined {R= 0.029 for 3 914 observed [I/σ(I) 3.0] diffractometer-collected reflections}. The Pt atom has square-planar co-ordination, with Pt–O bonds of normal length [average 2.024(3)Å]. Thus the general instability of alkoxoplatinum complexes is attributed to facile β-hydride elimination and not to abnormally long and weak Pt–O bonds. The trans isomer forms the fluxional chelate complex trans-[[graphic omitted]H)(PPh₂CH₂CMe₂OH)]Cl in CD₃OD, but in CDCl₃ it gives a neutral non-chelated species. It is also deprotonated by NEt₃ but only to the non-fluxional mono-alkoxo complex [[graphic omitted])(PPh₂CH₂CMe₂OH)]. The ³¹P-{¹H} and ¹H n.m.r. data for the complexes are discussed.