Monodentate phosphine substitution in [Pd(κ3-dppf)(PR3)][BF4]2 (dppf = 1,1'-bis(diphenylphosphino)ferrocene) compounds.

The ligand 1,1'-bis(diphenylphosphino)ferrocene (dppf) is commonly employed in a variety of catalytic systems. There are a variety of coordination modes known for dppf, the least studied being the κ3 coordination mode, in which both phosphorus atoms and the iron atom of dppf interact with another metal center. One such compound is the previously reported [Pd(κ3-dppf)(PPh3)]2+. A series of related compounds, [Pd(κ3-dppf)(P(p-C6H4R)3)]2+ (R = OCH3, CH3, F and CF3), has been synthesized and characterized. The X-ray crystal structure of [Pd(dppf)(P(p-C6H4F)3)][BF4]2 was determined. Electrochemical and computational studies indicate that the electron donor ability of the P(p-C6H4R)3 ligands influences the properties of these compounds. Substitution reactions of the P(p-C6H4R)3 ligands have been examined, and, in general, the more electron donating P(p-C6H4R)3 ligands completely replace the less electron donating ones. The kinetics of the reaction of [Pd(κ3-dppf)(P(p-C6H4F)3)]2+ with P(p-C6H4OCH3)3 indicate that the reaction proceeds through a dissociative mechanism, contrary to the associative substitutions prevalent in square planar palladium(ii) chemistry.

Coordination chemistry of a chelating amidoximato ligand.

A potentially general strategy for accessing the rarely encountered coordination of amidoximates through both oximato O and amido N atoms was developed. The new amidoxime (Z)-R(1)C(=NOH)NR(2)H (R(1) = mesityl, R(2) = 2-[[dimethylamino]methyl]phenyl), H(2)L, was prepared by reaction of equimolar amounts of the appropriate nitrile oxide and primary amine. Treatment of H(2)L with 1 equiv of AlMe(3) produced the dimeric species (MeAlL)(2) (1) possessing the formally dianionic ligand L(2)(-) bound to the aluminum via the oximato oxygen and the amido and amino nitrogens. The oximato oxygen atoms serve to link the two monomeric organoaluminum units together. Reaction of (ON)Cr(N(i)Pr(2))(3) with H(2)L provided the diamagnetic complex (ON)Cr(N(i)Pr(2))(eta(3)-L) (2). Interaction of 2 with excess methanol led, in particular, to the oxidative loss of NO and yielded the paramagnetic dimer [Cr(LH)(OMe)(mu-OMe)](2) (3) containing the eta(3)-bound amidoximato ligand protonated at its oximato nitrogen. In addition to spectroscopic characterizations of the new substances, single-crystal X-ray structures of H(2)L, 1.(4)/(3)C(6)H(6), and 3.MeOH were obtained.

Functionalized Derivatives of Benzo-Crown Ethers. Part 4. Antifungal Macrocyclic Supramolecular Complexes of Transition Metal Ions Acting as Lanosterol-14-alpha-Demethylase Ihibitors.

Poly- and mononuclear metal complexes of 2,3,11,12-bis[4-(10-aminodecylcarbonyl)]benzo-18- crown-6 (L) and Cu(II); Ni(II); Co(II) and Cr(III) have been synthesized and characterized by standard physico-chemical procedures. In the newly prepared complexes the crown moiety oxygen atoms of the macrocyclic host did not generally interact with metal ions, whereas the two amino groups of the ligand always did. Several of the newly synthesized compounds act as effective antifungal agents against Aspergillus and Candida spp., some of them showing activities comparable to ketoconazole, with minimum inhibitory concentrations in the range of 0.3-0.5 mug/mL. The mechanism of antifungal action of these coordination compounds is probably connected to an inhibition of lanosterol-14-alpha-demethylase, a metallo-enzyme playing a key role in sterol biosynthesis in fungi, bacteria and eukariotes.

Synthesis and antifungal activity of metal complexes containing dichloro-tetramorpholino-cyclophosphazatriene.

Metal complexes of dichloro-tetramorpholino-cyclophosphazatriene containing divalent cations such as Ni(II), Co(II), and Mn(II) have been prepared and characterised by standard physico-chemical procedures (elemental chemical analysis, IR and UV-VIS spectra, conductimetric measurement). The newly synthesised compounds possessed antifungal activity against Aspergillus and Candida spp., some of them showing effects comparable to ketoconazole (with minimum inhibitory concentrations in the range of 2- 30 mug/mL) but being generally less active as compared to the azole. Best activity was detected against C. albicans, and worst activity against A. niger. The mechanism of action of these compounds probably involves inhibition of ergosterol biosynthesis, and interaction with lanosterol-14-alpha-demethylase (CYP51A1), since reduced amounts of ergosterol were evidenced by means of HPLC in cultures of the sensitive strain A. niger treated with some of these inhibitors.