Search

The reaction of the [Rh7(CO)16]3- cluster anion with Ge2+ salts, in different stoichiometric ratios and under different atmospheres, leads to the formation of new heterometallic Rh-Ge clusters, representing the first known examples of Rh carbonyl compounds containing interstitial germanium atoms. More specifically, under N2 the reaction progressively affords the new [Rh13Ge(CO)25]3- and [Rh14Ge2(CO)30]2- clusters in good yields, with the Ge atoms located in cubic and square-anti-prismatic cavities, respectively. However, under a CO atmosphere, the [Rh13Ge(CO)25]3- derivative undergoes a significant structural and chemical rearrangement giving the new compound, [Rh12Ge(CO)27]4-, where Ge is hosted in an icosahedral metal cage. All species have been characterized by IR spectroscopy and ESI mass spectrometry, and their structures have been elucidated by single-crystal X-ray diffraction. Additionally, preliminary biological tests on the [Rh13Ge(CO)25]3- and [Rh14Ge2(CO)30]2- clusters show that they are cytotoxic to various cell lines.

The reactions of [Pt3n(CO)6n]2- (n = 2-5) homoleptic Chini-type clusters with increasing amounts of 1,3,5-triaza-7-phosphaadamantane (PTA) result in the stepwise substitution of one terminal CO ligand per Pt3 triangular unit up to the formation of [Pt3n(CO)5n(PTA)n]2- (n = 2-5). Competition between the nonredox substitution with retention of the nuclearity and the redox fragmentation to afford lower nuclearity heteroleptic Chini-type clusters is observed as a function of the amount of PTA and the nuclearity of the starting cluster. Because of this, [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- are more conveniently obtained via the oxidation of [Pt9(CO)15(PTA)3]2-. All the new species were spectroscopically characterized, and the structures of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- were determined by single-crystal X-ray diffraction. These clusters may be viewed as heteroleptic Chini-type clusters composed of stacks of four and five Pt3(μ-CO)3(CO)2(PTA) units, respectively. The solubility in water of [Pt12(CO)20(PTA)4]2- and [Pt15(CO)25(PTA)5]2- has been determined and their cytotoxicity towards human ovarian (A2780) cancer cells and their cisplatin-resistant strain (A2780cisR) has been evaluated.

The reaction of [Rh

The previously ill-characterized [H(x)Rh(22)(CO)(35)](4-/5-) carbonyl cluster has been obtained as a byproduct of the synthesis of [H(3)Rh(13)(CO)(24)](2-) and effectively separated by metathesis of their sodium salts with [NEt(4)]Cl. Although the yields are modest and never exceed 10-15% (based on Rh), this procedure affords spectroscopically pure [H(3)Rh(22)(CO)(35)](5-) anion. Formation of the latter in mixture with other Rh clusters was also observed by electrospray ionization-mass spectrometry (ESI-MS) in the oxidation of [H(2)Rh(13)(CO)(24)](3-) with Cu(2+) salts. The recovery of further amounts of [H(3)Rh(22)(CO)(35)](5-) was hampered by too similar solubility of the salts composing the mixture. Conversely, the reaction in CH(3)CN of [H(2)Rh(13)(CO)(24)](3-) with [Cu(MeCN)(4)](+)[BF(4)](-) leads to the [H(2)Rh(13)(CO)(24){Cu(MeCN)}(2)](-) bimetallic cluster. The X-ray crystal structures of [H(4)Rh(22)(CO)(35)](4-), [H(3)Rh(22)(CO)(35)](5-), and [H(2)Rh(13)(CO)(24){Cu(MeCN)}(2)](-) are reported. From a formal point of view, the metal frame of the former two species can be derived by interpenetration along two orthogonal axes of two moieties displaying the structure of the latter. The availability of [H(8-n)Rh(22)(CO)(35)](n-) salts prompted their detailed chemical, spectroscopic, and electrochemical characterization. The presence of hydride atoms has been directly proved both by ESI-MS and (1)H NMR. Moreover, both [H(4)Rh(22)(CO)(35)](4-) and [H(3)Rh(22)(CO)(35)](5-) undergo distinctive electrochemically reversible redox changes. This allows to assess electrochemical studies as indisputable though circumstantial evidence of the presence of (1)H NMR-silent hydride atoms in isostructural anions of different charge.

The reaction of Collman's reagent Na2[Fe(CO)4]·2thf with one equivalent of Au(NHC)Cl (NHC = IMes, IPr; IMes = C3N2H2(C6H2Me3)2; IPr = C3N2H2(C6H3iPr2)2) in dmso resulted in the [Fe(CO)4(AuNHC)]– (NHC = IMes, 1; IPr, 2) mono-anions. 1–2 further reacted with Au(NHC)Cl or Au(PPh3)Cl affording the neutral complexes Fe(CO)4(AuNHC)2 (NHC = IMes, 3; IPr, 4), Fe(CO)4(AuIMes)(AuIPr) (5) and Fe(CO)4(AuNHC)(AuPPh3) (NHC = IMes, 6; IPr, 7). 1–7 have been spectroscopically characterized by IR, 1H, 13C1H and 31P1H NMR techniques. Moreover, the molecular structures of 1, 2, 4, 6 and 7 have been determined through single-crystal X-ray diffraction as their [NMe4][Fe(CO)4(AuIMes)], [NEt4][Fe(CO)4(AuIMes)], [NEt4][Fe(CO)4(AuIPr)], Fe(CO)4(AuIPr)2·1.5toluene, Fe(CO)4(AuIPr)(AuPPh3), Fe(CO)4(AuIMes)(AuPPh3)·0.5CH2Cl2 salts and solvates. The nature of the bonds in 1 and 2 was elucidated on the basis of atoms-in molecules (AIM) analyses on the DFT-optimized structures and compared with the corresponding compounds 3 and 4. 1–7 contained strong Fe-CO, Fe-Au, Au-P and Au–NHC bonds as well as weak Au···Au interactions. The different stability and reactivity of IMes-derivatives vs. IPr-ones was rationalized on the basis of steric effects.

The reactions of [Pt6(CO)6(SnX2)2(SnX3)4]4– (X = Cl, 1; Br, 2) with an excess of HBF4·Et2O afforded the new [Pt12(CO)10(SnCl)2(SnCl2)4{Cl2Sn(μ-OH)SnCl2}2]2– (3) and [Pt7(CO)6(SnBr2)4{Br2Sn(μ-OH)SnBr2}{Br2Sn(μ-Br)SnBr2}]2– (4) heterometallic clusters. The molecular structures of 3 and 4 were determined by means of single crystal X-ray diffraction. The bonding within these bimetallic Pt–Sn clusters were investigated computationally by means of DFT methods and Atoms-In-Molecules analyses. 3 and 4 displayed a low valent Pt core stabilised by the interaction with CO and Sn(II) based ligands. The solid state structures of these clusters revealed the presence on H-bonds involving the OH-groups of the {X2Sn(μ-OH)SnX2}– ligands.