Palladium(II) and Platinum(II) Complexes of Novel Water-Soluble Phosphane CAP: Structure, Interligand Hydrogen-Hydrogen Bonding and in Vitro Cytotoxicity

Abstract

Palladium(II) and platinum(II) chloro complexes of novel water‐soluble cage‐like phosphane CAP (1,4,7‐triaza‐9‐phosphatricyclo[5.3.2.14,9]tridecane) have been synthesized and characterized in comparison with their counterparts bearing well known PTA (1,3,5‐triaza‐7‐phosphaadamantane) ligand. A peculiar structural feature of studied cis‐[MCl2L2] complexes is the occurrence of interligand C−Hσ+⋅⋅⋅σ+H−C interactions (hydrogen‐hydrogen bonds) between the phosphane cages: the first case encountered so far among metal‐phosphane complexes. Due to substantial stabilizing contribution to the net molecular energy of the complexes (∼ 20 kcal mol−1), hydrogen‐hydrogen bonding is sufficient to maintain sterically overcrowded cis conformations of the complexes. The interplay between protonation stage of the ligands and their conformations can be a reason of significant differences in in‐vitro cytotoxicity between CAP complexes and their PTA‐bearing counterparts.

Synthesis of New Ruthenium‐CAP Complexes and Use as Catalysts for Benzonitrile Hydration to Benzamide

“…Recently, Britvin and coworkers reported the synthesis of the new cage-like water soluble phosphine 1,4,7-triaza-9phosphatricyclo[5.3.2.1]tridecane, to which they gave the acronym of CAP (Figure 1). [26] Although examples of CAP complexes of Au, [26a] Pt and Pd, [27,28] Tc and Re, [29] and Rh [30] were reported, its coordination chemistry with Ru is still underdeveloped. We recently reported the synthesis of the Ru-arene CAP complexes [RuCl 2 (η 6 -p-cymene)(CAP)] (RACAPÀ C) and [RuCl (η 6 -p-cymene)(L)(CAP)]PF 6 (L = CAP or MeCN), that showed to be active in vitro anticancer agents.…”

Water-soluble carbonyl complexes of 99Tc(I) and Re(I) with adamantane-cage aminophosphines PTA and CAP

“…Coordination chemistry of the small adamantane-cage aminophosphines, 1,3,5-triaza-7phosphaadamantane (PTA) and its recently synthesized analog 1,4,7-triaza-9phosphatricyclo[5.3.2 14,9 ]tridecane (CAP), is extensively developed [1][2][3][4][5][6].These ligands combine two kinds of donor atoms, P and N, which is of interest itself from the viewpoint of hard/soft acid-base coordination preferences. In the case of P-coordination, the uncoordinated N atoms remain available for acid-base interactions in aqueous solution (protonation), making the complexes hydrophilic.…”

“…The pH-dependent hydrophilicity of the complexes opens interesting prospects for the development of new pharmaceuticals, because the degree of protonation at the nitrogen atoms can influence the biodistribution of the complexes. In particular, it is known that the pH of cancer cells is lower than that of normal cells; therefore, the uptake of the complexes in normal and cancer cells may be different due to different degrees of protonation and hence different charges of the complexes [4][5][6][7][8]. Technetium-99m is the most widely used radionuclide for diagnostic purposes in nuclear medicine.…”