Tetraacetatodirhodium(II) complexes with tris(methoxyphenyl)phosphines, their reactivity, structure, and antitumor activity

Abstract

Reactions of [Rh2(µ-OAc)4(H2O)2] ([1·(H2O)2]) with tris(3-methoxyphenyl)phosphine at 1:1 and 1:2 molar ratios yield, first, the appropriate adducts: [1·(H2O){P(C6H4-3-OMe)3}] and [1·{P(C6H4-3-OMe)3}2], and then [Rh2(µ-OAc)3{µ-(C6H3-3-OMe)P(C6H4-3-OMe)2}(HOAc)2] ([2·(HOAc)2]), and [Rh2(µ-OAc)2{µ-(C6H3-3-OMe)P(C6H4-3-OMe)2}2(HOAc)2] ([3·(HOAc)2]) complexes, respectively. They have been characterized by spectroscopic methods. The molecular structure of [3·(HOAc)(H2O)] has been determined crystallographically. The complexes [3·(HOAc)2], [Rh2(µ-OAc)3{µ-(C6H3-4-OMe)P(C6H4-4-OMe)2}(HOAc)2] ([4·(HOAc)2]), and [Rh2(µ-OAc)2{µ-(C6H3-4-OMe)P(C6H4-4-OMe)2}2(HOAc)2] ([5·(HOAc)2]) reversibly react with CO giving mono- and biadducts. Antitumor activity of binuclear rhodium(II) compounds [3·(HOAc)2], [Rh2(µ-OAc)3{µ-(C6H3-2-O)P(C6H3-2-OMe)2}(HOAc)] ([6·(HOAc)]), and [Rh2(µ-OAc)3{µ-(C6H3-6-OMe-2-O)P[(C6H3-2,6-(OMe)2]2}(HOAc)] ([7·(HOAc)]) have been investigated in vitro. The most active agent for investigated tumor lines is complex [6·(HOAc)]. It shows higher activity than cisplatin (cis-[PtCl2(NH3)2]). Antitumor activity decreases in the series: [6·(HOAc)] > [7·(HOAc)] > [3·(HOAc)2]. Activity of all investigated rhodium(II) complexes is higher than that of [1·(H2O)2].Key words: dirhodium(II) complexes, functionalized phosphines, aryl phosphines, ferrocenylmethylphosphines, adducts with CO, antitumor activity, orthometallation reactions.