Platinum(II) phosphonate complexes derived from endo-8-camphanylphosphonic acid

Abstract

The reactions of cis-[PtCl 2 L 2 ] [L = PPh 3 , PMe 2 Ph or L 2 = Ph 2 P(CH 2) 2 PPh 2 (dppe)] with endo-8-camphanylphosphonic acid (CamPO 3 H 2) and Ag 2 O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O 3 PCam)L 2 ]. The X-ray crystal structure of [Pt(O 3 PCam)(PPh 3) 2 ]•2CHCl 3 shows that the bulky camphanyl group, rather than being directed away from the platinum, is instead directed into a pocket formed by the Pt and the two PPh 3 ligands. This allows the O 3 P-CH 2 group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates nonfluxional behaviour for the sterically bulky PPh 3 and dppe derivatives, which contain inequivalent phosphine ligands in their 31 P NMR spectra. These findings are backed up by theoretical calculations on the PPh 3 and PPhMe 2 derivatives, which show respectively high and low energy barriers to rotation of the camphanyl group in the PPh 3 and PPhMe 2 complexes. The X-ray crystal structure of CamPO 3 H 2 is also reported, and consists of hydrogen-bonded hexameric aggregates, which assemble to form a columnar structure containing hydrophilic phosphonic acid channels surrounded by a sheath of bulky, hydrophobic camphanyl groups.

Molecular Metal Phosphonates

“…In the 1.110 coordination binding mode the phosphonate ligands bind in a chelating manner as exemplified in a Pt II complex (Figure ). Note that in this case one of the P–O distances, P(1)–O(1), 1.489(2) Å, is much shorter than the other two . This is reminiscent of the anisobidentate coordination behavior of the carboxylate ligand.…”

“…Note that in this case one of the P−O distances, P(1)−O(1), 1.489(2) Å, is much shorter than the other two. 277 This is reminiscent of the anisobidentate coordination behavior of the carboxylate ligand.…”

“…Information on all molecular Pt II phosphonates is listed in Table . − Ferrocenemonophosphonic and diphosphonic acids have been utilized to prepare mono- and dinuclear platinum phosphonate complexes . The reaction of ferrocenephosphonic acid and cis -[PtCl 2 (PPh 3 ) 2 ] in the presence of excess Ag 2 O afforded [FcCH 2 PO 3 Pt­(PPh 3 ) 2 ].…”

“…1.110 coordination binding mode. P–O bond distances: P(1)–O(1), 1.489(2) Å; P(1)–O(2), 1.575(2) Å; P(1)–O(3), 1.579(2) Å . Adapted from ref .…”

“…P–O bond distances: P(1)–O(1), 1.489(2) Å; P(1)–O(2), 1.575(2) Å; P(1)–O(3), 1.579(2) Å . Adapted from ref . Copyright 2011 Elsevier Masson SAS.…”