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

The reactions of cis-[PtCl₂L₂] [L = PPh₃, PMe₂Ph or L₂ = Ph₂P(CH₂)₂PPh₂ (dppe)] with endo-8-camphanylphosphonic acid (CamPO₃H₂) and Ag₂O in refluxing dichloromethane gave platinum(II) phosphonate complexes [Pt(O₃PCam)L₂]. The X-ray crystal structure of [Pt(O₃PCam)(PPh₃)₂]•₂CHCl₃ 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 PPh₃ ligands. This allows the O₃P–CH₂ group to have a preferred staggered conformation. The complexes were studied in detail by NMR spectroscopy, which demonstrates non-fluxional behaviour for the sterically bulky PPh₃ and dppe derivatives, which contain inequivalent phosphine ligands in their ³¹P NMR spectra. These findings are backed up by theoretical calculations on the PPh₃ and PPhMe₂ derivatives, which show, respectively, high and low energy barriers to rotation of the camphanyl group in the PPh₃ and PPhMe₂ complexes. The X-ray crystal structure of CamPO₃H₂ 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

Reactivity of the metalloligand [Pt2(µ-S)2(PPh3)4] toward tellurium(II) thiourea complexes: synthesis and structural characterization of the ditellurium(I) derivative [{Pt2(µ-S)2(PPh3)4}2Te2]2+

Reaction of the platinum(II) sulfide metalloligand [Pt2(µ-S)2(PPh3)4] with the tellurium(II) source TeCl2(tu)2 (tu = thiourea) is dependent on reaction conditions employed. In the presence of added acid, the dominant species observed in the electrospray ionization (ESI) mass spectrum is the tetraplatinum species [{Pt2(µ-S)2(PPh3)4}2Te2]2+. This contains the Te22+ moiety and is related to the previously reported tellurium(I) dithiophosphinate analog [(Ph2PS2)2Te2]. However, in the absence of acid, considerable degradation of the {Pt2S2} metalloligand occurs as evidenced by the formation of the mononuclear complex [Pt{SC(NH2)NH}(PPh3)2]+ containing a deprotonated thiourea ligand, together with other thiourea-containing ions, identified by ESI MS. Likewise, attempted use of a fully substituted thiourea, viz. Me2NC(S)NMe2 (tmtu) in TeCl2(tmtu)2, also resulted in degradation of the {Pt2S2} core and detection of the known complex [(Ph3P)2PtCl{SC(NMe2)2}]+. The [{Pt2(µ-S)2(PPh3)4}2Te2]2+ cation was isolated with several anions, and unequivocal confirmation of the structure of the complex was obtained by an X-ray structure determination on the BF4- salt, which shows the presence of the Te22+ unit, with the Te–Te bond bridged by two {Pt2S2} metalloligands. Density functional theory was used to further probe the Te22+ bonding interactions in [{Pt2(μ-S)2(PPh3)4}2Te2]2+ and the previously reported [(Ph2PS2)2Te2