Abstract
Mononuclear and dinuclear Ru(II) complexes cis-[Ru(κ2-dppm)(bpy)Cl2] (1), cis-[Ru(κ2-dppe)(bpy)Cl2] (2) and [Ru2(bpy)2(μ-dpam)2(μ-Cl)2](Cl)2 ([3](Cl)2) were prepared from the reactions between cis(Cl), cis(S)-[Ru(bpy)(dmso-S)2Cl2] and diphosphine/diarsine ligands (bpy = 2,2′-bipyridine; dppm = 1,1-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino)ethane; dpam = 1,1-bis(diphenylarsino)methane). While methoxy-substituted ruthenafuran [Ru(bpy)(κ2-dppe)(C^O)]+ ([7]+; C^O = anionic bidentate [C(OMe)CHC(Ph)O]− chelate) was obtained as the only product in the reaction between 2 and phenyl ynone HC≡C(C=O)Ph in MeOH, replacing 2 with 1 led to the formation of both methoxy-substituted ruthenafuran [Ru(bpy)(κ2-dppm)(C^O)]+ ([4]+) and phosphonium-ring-fused bicyclic ruthenafuran [Ru(bpy)(P^C^O)Cl]+ ([5]+; P^C^O = neutral tridentate [(Ph)2PCH2P(Ph)2CCHC(Ph)O] chelate). All of these aforementioned metallafuran complexes were derived from Ru(II)–vinylidene intermediates. The potential applications of these metallafuran complexes as anticancer agents were evaluated by in vitro cytotoxicity studies against cervical carcinoma (HeLa) cancer cell line. All the ruthenafuran complexes were found to be one order of magnitude more cytotoxic than cisplatin, which is one of the metal-based anticancer agents being widely used currently.
Highlights
In 2015, we reported the synthesis of metallafuran complexes in the form of [M(bpy)2 (CO)]+ from the reactions between cis-[M(bpy)2 Cl2 ] (M = Ru, Os; bpy = 2,20 -bipyridine) and ynone HC≡C(C=O)Ph in MeOH (Scheme 1a; CO represents an anionic bidentate [C(OMe)CHC(Ph)O]− chelate, coordinating atoms in italics) [38]
The reaction between 2 and HC≡C(C=O)Ph in MeOH only led to the formation of methoxy-substituted ruthenafuran [Ru(bpy)(κ2 -dppe)(CO)]+ ([7]+ ), but reacting 1 with HC≡C(C=O)Ph under identical reaction conditions gave a mixture of methoxy-substituted ruthenafuran [Ru(bpy)(κ2 -dppm)(CO)]+ ([4]+ ) and phosphoniumring-fused bicyclic ruthenafuran [Ru(bpy)(PCO)Cl]+ ([5]+ )
They were found to be one order of magnitude more cytotoxic than the classic metal-based anticancer agent cisplatin
Summary
Activation of alkynes by transition-metal complexes has recently gained increasing research interest in the field of organometallic chemistry [1–30]. The formation of metal–vinylidene species via alkyne–vinylidene rearrangement has been regarded as a key step in Ru(II)-induced alkyne transformations, a number of our synthetic studies revealed that Ru(II) can activate alkynes via “non-vinylidene” pathways [31,32]. With the aim to gain control on the modes of alkyne activation, we initiated research activities on probing and isolating intermediates and products from the reactions between functionalized alkynes and a variety of Fe(II), Ru(II) and Os(II) complexes [31–47]. In 2015, we reported the synthesis of metallafuran complexes in the form of [M(bpy) (CO)]+ from the reactions between cis-[M(bpy) Cl2 ] (M = Ru, Os; bpy = 2,20 -bipyridine) and ynone HC≡C(C=O)Ph in MeOH (Scheme 1a; CO represents an anionic bidentate [C(OMe)CHC(Ph)O]− chelate, coordinating atoms in italics) [38].
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