Reactions of dirhodium(II) monometallated compounds with phosphines. Factors affecting the reactivity and the structure of the doubly-metallated compounds. Molecular structure of Rh2(O2CCH3)2[(C6H4)P(C6H5)2][(p-ClC6H3)P(p-ClC6H4)2] · (HO2CCH3)2·(C6H6), a compound with two different metallated phosphines

Sensitive and selective chromogenic sensing of carbon monoxide via reversible axial CO coordination in binuclear rhodium complexes

The study of probes for CO sensing of a family of binuclear rhodium(II) compounds of general formula [Rh(2){(XC(6)H(3))P(XC(6)H(4))}(n)(O(2)CR)(4-n)]·L(2) containing one or two metalated phosphines (in a head-to-tail arrangement) and different axial ligands has been conducted. Chloroform solutions of these complexes underwent rapid color change, from purple to yellow, when air samples containing CO were bubbled through them. The binuclear rhodium complexes were also adsorbed on silica and used as colorimetric probes for "naked eye" CO detection in the gas phase. When the gray-purple colored silica solids containing the rhodium probes were exposed to air containing increasing concentrations of CO, two colors were observed, in agreement with the formation of two different products. The results are consistent with an axial coordination of the CO molecule in one axial position (pink-orange) or in both (yellow). The crystal structure of 3·(CO) ([Rh(2){(C(6)H(4))P(C(6)H(5))(2)}(2)(O(2)CCF(3))(2)]·CO) was solved by single X-ray diffraction techniques. In all cases, the binuclear rhodium complexes studied showed a high selective response to CO with a remarkable low detection limit. For instance, compound 5·(CH(3)CO(2)H)(2) ([Rh(2){(m-CH(3)C(6)H(3))P(m-CH(3)C(6)H(4))(2)}(2)(O(2)CCH(3))(2)]·(CH(3)CO(2)H)(2)) is capable of detection of CO to the "naked eye" at concentrations as low as 0.2 ppm in air. Furthermore, the binding of CO in these rhodium complexes was found to be fully reversible, and release studies of carbon monoxide via thermogravimetric measurements have also been carried out. The importance of the silica support for the maintenance of the CO-displaced L ligands in the vicinity of the probes in a noninnocent manner has been also proved.

Chiral Supramolecules: Organometallic Molecular Loops Made from Enantiopure R-[cis-Rh2(C6H4PPh2)2(CH3CN)6](BF4)2

Two enantiopure molecular loops, RR-[cis-Rh2(C6H4PPh2)2(py)2O2C(CF2)(n)CO2]2 (1, n = 2 and 2, n = 3) have been made from the reaction in CH2Cl2 and CH3OH of the inherently chiral dirhodium compound, R-[cis-Rh2(C6H4PPh2)2(CH3CN)6](BF4)2, and HO2C(CF2)(n)CO2H in the presence of an excess of pyridine. Single-crystal structure analyses reveal that each of these compounds is composed of two R-cis-Rh2(C6H4PPh2)2(ax-py)2(2+) units, and two equatorial perfluorodicarboxylate linkers, which form a loop oligomer. The 1H, 19F, and 31P[1H] NMR spectra in CDCl3 and C5D5N indicate that only one type of highly symmetric species exists in each solution, which is consistent with the solid-state structures.

Chiral Organometallic Triangles with Rh−Rh Bonds. 1. Compounds Prepared from Racemic cis-Rh2(C6H4PPh2)2(OAc)2

Reaction of racemic cis-Rh(2)(C(6)H(4)PPh(2))(2)(OAc)(2)(HOAc)(2) with excess Me(3)OBF(4) in CH(3)CN results in the formation of racemic cis-[Rh(2)(C(6)H(4)PPh(2))(2)(CH(3)CN)(6)](BF(4))(2).0.5H(2)O (1.0.5H(2)O), an ionic dirhodium complex which has two cisoid nonlabile orthometalated phosphine bridging anions and six labile CH(3)CN ligands in equatorial and axial positions. Reactions of 1 with tetraethylammonium salts of the linear dicarboxylates, oxalate, terephthalate, and 4,4'-biphenyl-dicarboxylate, in organic solvents, produced racemic crystals of the triangular compounds [Rh(2)(C(6)H(4)PPh(2))(2)](3)(C(2)O(4))(3)(py)(6).6MeOH.H(2)O (2.6MeOH.H(2)O), [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)CO(2))(3)(DMF)(6).6.5DMF.0.5H(2)O (3.6.5DMF.0.5H(2)O), and [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)C(6)H(4)CO(2))(3)(py)(6).4.5CH(3)OH.0.75H(2)O (4.4.5CH(3)OH.0.75H(2)O), respectively. All compounds are electrochemically active. The relative chiralities of the dirhodium units in each triangle have been established using a combination of data from X-ray crystallography and (31)P NMR spectroscopy.

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

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.