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The molecular [Pt33(CO)38](2-) nanocluster was obtained from the thermal decomposition of Na2[Pt15(CO)30] in methanol. The reaction of [Pt19(CO)22](4-) with acids (1-2 equiv) affords the unstable [Pt19(CO)22](3-) trianion, which evolves with time leading eventually to the [Pt40(CO)40](6-) hexa-anion. The total structures of both nanoclusters were determined via single-crystal X-ray diffraction. [Pt33(CO)38](2-) displays a defective ccp Pt33 core and shows that localized deformations occur in correspondence of atomic defects to "repair" them. In contrast, [Pt40(CO)40](6-) shows a bcc Pt40 core and represents the largest Pt cluster with a body-centered structure. The rich electrochemistry of the two high-nuclearity platinum carbonyl clusters was studied by cyclic voltammetry and electrochemical in situ Fourier transform infrared spectroscopy. The redox changes of [Pt33(CO)38](2-) show features of chemical reversibility and electrochemical quasi-reversibility, and the vibrational spectra in the CO stretching region of the nine redox forms of the cluster [Pt33(CO)38](n) (n = 0 to -4, -6 to -9) are reported. Almost all the redox processes exhibited by [Pt40(CO)40](6-) are chemically and electrochemically reversible, and the eight oxidation states of [Pt40(CO)40] from -4 to -11 were spectroscopically characterized. The effect of the more regular bcc Pt-carbonyl cluster structure of [Pt40(CO)40](6-) with respect to that of the defective ccp Pt33 core on the redox behavior is discussed.

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The reaction of the [Pt3n(CO)6n](2-) (n = 2-6) Chini's clusters with increasing amounts of PPh3 has been investigated in detail by combined FT-IR, (31)P{(1)H} NMR, and electrospray ionization-mass spectrometry (ESI-MS) studies, showing that up to three CO ligands are gradually substituted by PPh3, resulting in isonuclear phosphine-substituted anionic clusters of general formula [Pt3n(CO)(6n-x)(PPh3)(x)](2-) (n = 2-6; x = 1-3). Further addition of PPh3 results in the elimination of the neutral Pt3(CO)3(PPh3)3 species and formation of lower nuclearity anionic clusters. [Pt12(CO)22(PPh3)2](2-) and [Pt9(CO)16(PPh3)2](2-) have been structurally characterized, and they maintain the trigonal prismatic structures of the parent homoleptic clusters, with the two PPh3 ligands bonded to different external Pt3-triangles in relative cis-position. Conversely, the crystal structure of [Pt6(CO)10(PPh3)2](2-) shows that its metal cage is transformed from trigonal prismatic to trigonal antiprismatic after CO/PPh3 exchange.

The oxidation and reduction reactions of [Co6C(CO)15](2-) have been studied in detail, leading to the isolation of several new Co-carbide carbonyl clusters. Thus, [Co6C(CO)15](2-) reacts in tetrahydrofuran (THF) with oxidants such as HBF4·Et2O and [Cp2Fe][PF6], resulting first in the formation of the previously reported [Co6C(CO)14](-); then, in CH2Cl2, the new dicarbide [Co11C2(CO)23](2-) is formed. The latter may be further oxidized, yielding the isostructural monoanion [Co11C2(CO)23](-), whereas its reduction with (cyclopentadienyl)2Co affords the unstable trianion [Co11C2(CO)23](3-), which decomposes during workup. Oxidation of [Co6C(CO)15](2-) in CH3CN with [C7H7][BF4] affords the same major products, and besides, the new monoacetylide [Co10(C2)(CO)21](2-) was obtained as side-product. Conversely, the reduction of [Co6C(CO)15](2-) in THF with increasing amounts of Na/naphthalene results in the following species: [Co6C(CO)13](2-), [Co11(C2)(CO)22](3-), [Co7C(CO)15](3-), [Co8C(CO)17](4-), [Co6C(CO)12](3-), and [Co(CO)4](-). The new [Co11C2(CO)23](-), [Co11C2(CO)23](2-), [Co10(C2)(CO)21](2-), [Co8C(CO)17](4-), [Co6C(CO)12](3-), and [Co7C(CO)15](3-) clusters were structurally characterized. Moreover, the paramagnetic species [Co11C2(CO)23](2-) and [Co6C(CO)12](3-) were investigated by means of electron paramagnetic resonance spectroscopy. Finally, electrochemical studies were performed on [Co11C2(CO)23](n-) (n = 1-3).

The reactions of [Pt(CO)] (n = 2-4) homoleptic Chini-type clusters with stoichiometric amounts of PhPCHCHPPh (dppe) result in the heteroleptic Chini-type clusters [Pt(CO)(dppe)], [Pt(CO)(dppe)], and [Pt(CO)(dppe)]. Their formation is accompanied by slight amounts of neutral species such as Pt(CO)(dppe), Pt(CO)(dppe), and Pt(dppe). A similar behavior was observed with the chiral ligand R-PhPCH(Me)CHPPh (R-dppp), and two isomers of [Pt(CO)(R-dppp)] were identified. All the new species were spectroscopically characterized by means of IR and P NMR, and their structures were determined by single-crystal X-ray diffraction. The results obtained are compared to those previously reported for monodentate phosphines, that is, PPh, as well as more rigid bidentate ligands, that is, CH═C(PPh) (P^P), CH(PPh) (dppm), and o-CH(PPh) (dppb). From a structural point of view, functionalization of anionic platinum Chini clusters preserves their triangular Pt units, whereas the overall trigonal prismatic structures present in the homoleptic clusters are readily deformed and transformed upon functionalization. Such transformations may be just local deformations, as found in [Pt(CO)(dppe)], [Pt(CO)(R-dppp)], [Pt(CO)(PPh)], and [Pt(CO)(PPh)]; an inversion of the cage from trigonal prismatic to octahedral, as observed in [Pt(CO)(dppe)] and [Pt(CO)(PPh)]; the reciprocal rotation of two trigonal prismatic units with the loss of a Pt-Pt contact as found in [Pt(CO)(dppe)].

Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt(13)(CO)(12){Cd(5)(μ-Br)(5)Br(2)(dmf)(3)}(2)](2-) (1), [Pt(19)(CO)(17){Cd(5)(μ-Br)(5)Br(3)(Me(2)CO)(2)}{Cd(5)(μ-Br)(5)Br(Me(2)CO)(4)}](2-) (2), [H(2)Pt(26)(CO)(20)(CdBr)(12)](8-) (3) and [H(4)Pt(26)(CO)(20)(CdBr)(12)(PtBr)(x)](6-) (4) (x = 0-2), have been obtained from the reactions between [Pt(3n)(CO)(6n)](2-) (n = 2-6) and CdBr(2)·H(2)O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt(26)Cd(12) metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.