SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF PD(II) AND PT(II) COMPLEXES WITH P-BONDED 1'-(DIPHENYLPHOSPHINO)FERROCENECARBOXYLIC ACID

The title hybrid phosphine ligand (Hdpf) coordinates to Pt(II) and Pd( II) as a monodentate phosphine. In the absence of deprotonating agents , its carboxyl group remains uncoordinated to metal, but takes part in various types of hydrogen bonding. Using K2MCl4 as the metal ion sour ce, trans-square planar complexes of the M(Hdpf-P)(2)X-2 type (M=Pd, X =Cl, Br, M=Pt, X=Cl) were obtained. While Pd(Hdpf-P)(2)Cl-2 is formed also from Pd(cycloocta-1,5-diene)Cl-2, the analogous Pt(II)-cod comple x provides cis-square planar Pt(Hdpf-P)(2)Cl-2. The trans-chlorides be have inconsistently on recrystallization from carboxylic acids. While acetic acid gives single crystals of the solvates M(Hdpf-P)(2)Cl-2 . 2 AcOH, propionic or formic acid does not form solvates with Pt(Hdpf-P) (2)Cl-2 at comparable conditions. Single crystal X-ray structure deter mination of the last four complexes revealed remarkable differences in the conformation of the ferrocenyl moiety and in inter-and intramolec ular hydrogen bonding. The two isostructural solvates have molecular a rrangement with solvent molecules hydrogen-bonded to the carboxyl grou ps of the ligand, thus saturating their hydrogen-bond capability. As c an be expected, the structure of the unsolvated trans-Pt(Hdpf-P)(2)Cl- 2 is that of a one-dimensional polymer linked by intermolecular hydrog en bonds. Finally, the cis-complex is dimeric in the crystal, being jo ined by pairs of the peripheral carboxyls; there is a further bonding pi-pi interaction between the phenyl groups of the cis-phosphines. (C) 1998 Elsevier Science S.A.