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This article describes a rare case of cluster core isomerism in a large molecular organometallic nanocluster. In particular, two isomers of the [HCo 15 Pd 9 C 3 (CO) 38 ] 2- nanocluster, referred as TP-Pd 9 and Oh-Pd 9 , have been structurally characterized by single-crystal X-ray crystallography as their [NMe 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·CH 2 Cl 2 (ca. 1:1 TP-Pd 9 and Oh-Pd 9 mixture), [NMe 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·2CH 2 Cl 2 (mainly TP-Pd 9 ), [NEt 3 (CH 2 Ph)] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·CH 2 Cl 2 (mainly TP-Pd 9 ), [MePPh 3 ] 2 [HCo 15 Pd 9 C 3 (CO) 38 ]·2.5CH 2 Cl 2 (mainly TP-Pd 9 ), and [MePPh 3 ] 2 [HCo 15 Pd 9 C 3 (CO) 38 ] (Oh-Pd 9 ) salts. The cluster core of TP-Pd 9 is a tricapped trigonal prism, whereas this is a tricapped octahedron in Oh-Pd 9 . The presence in the solid state of the Oh-Pd 9 or TP-Pd 9 isomers depends on the cation employed and/or the number and type of co-crystallized solvent molecules. Often, mixtures of the two isomers, within the same single crystal or as mixtures of different crystals within the same crystallization batch, are obtained. Structural isomerism in organometallic nanoclusters is discussed and compared to that in Au-thiolate nanoclusters., Competing Interests: The authors declare no competing financial interest.

The reactions of [Pt 6 (CO) 12 ] 2- with CH(PPh 2 ) 2 (dppm), CH 2 ═C(PPh 2 ) 2 (P^P), and Fe(C 5 H 4 PPh 2 ) 2 (dppf) proceed via nonredox substitution and result in the heteroleptic Chini-type clusters [Pt 6 (CO) 10 (dppm)] 2- , [Pt 6 (CO) 10 (P^P)] 2- , and [Pt 6 (CO) 10 (dppf)] 2- , respectively. Conversely, the reactions of [Pt 6 (CO) 12 ] 2- with Ph 2 P(CH 2 ) 4 PPh 2 (dppb) and Ph 2 PC≡CPPh 2 (dppa) can be described as redox fragmentation that afford the neutral complexes Pt(dppb) 2 , Pt 2 (CO) 2 (dppa) 3 , and Pt 8 (CO) 6 (PPh 2 ) 2 (C≡CPPh 2 ) 2 (dppa) 2 . The oxidation of [Pt 6 (CO) 10 (dppm)] 2- results in its oligomerization to yield the larger heteroleptic Chini-type clusters [Pt 12 (CO) 20 (dppm) 2 ] 2- , [Pt 18 (CO) 30 (dppm) 3 ] 2- , and [Pt 24 (CO) 40 (dppm) 4 ] 2- (for the latter there is only IR spectroscopic evidence). All the clusters were characterized by means of IR and 31 P NMR spectroscopies and electrospray ionization mass spectrometry. Moreover, the crystal structures of [NEt 4 ] 2 [Pt 6 (CO) 10 (dppm)]·CH 3 CN, [NEt 4 ] 2 [Pt 12 (CO) 20 (dppm) 2 ]·2CH 3 CN·2dmf, [NEt 4 ] 2 [Pt 12 (CO) 20 (dppm) 2 ]·4dmf, [NEt 4 ] 2 [Pt 6 (CO) 10 (dppf)]·2CH 3 CN, Pt 2 (CO) 2 (dppa) 3 ·0.5CH 3 CN, Pt 8 (CO) 6 (PPh 2 ) 2 (C≡CPPh 2 ) 2 (dppa) 2 ·2thf, and Pt(dppb) 2 were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).

The reaction of [NEt 4 ] 2 [Ni 6 (CO) 12 ] in thf with 0.5 equiv of PCl 3 affords the monophosphide [Ni 11 P(CO) 18 ] 3- that in turn further reacts with PCl 3 resulting in the tetra-phosphide carbonyl cluster [HNi 31 P 4 (CO) 39 ] 5- . Alternatively, the latter can be obtained from the reaction of [NEt 4 ] 2 [Ni 6 (CO) 12 ] in thf with 0.8-0.9 equiv of PCl 3 . The [HNi 31 P 4 (CO) 39 ] 5- penta-anion is reversibly protonated by strong acids leading to the [H 2 Ni 31 P 4 (CO) 39 ] 4- tetra-anion, whereas deprotonation affords the [Ni 31 P 4 (CO) 39 ] 6- hexa-anion. The latter is reduced with Na/naphthalene yielding the [Ni 31 P 4 (CO) 39 ] 7- hepta-anion. In order to shed light on the polyhydride nature and redox behavior of these clusters, electrochemical and spectroelectrochemical studies were carried out on [Ni 11 P(CO) 18 ] 3- , [HNi 31 P 4 (CO) 39 ] 5- , and [H 2 Ni 31 P 4 (CO) 39 ] 4- . The reversible formation of the stable [Ni 11 P(CO) 18 ] 4- tetra-anion is demonstrated through the spectroelectrochemical investigation of [Ni 11 P(CO) 18 ] 3- . The redox changes of [HNi 31 P 4 (CO) 39 ] 5- show features of chemical reversibility and the vibrational spectra in the ν CO region of the nine redox states of the cluster [HNi 31 P 4 (CO) 39 ] n- (n = 3-11) are reported. The spectroelectrochemical investigation of [H 2 Ni 31 P 4 (CO) 39 ] 4- revealed the presence of three chemically reversible reduction processes, and the IR spectra of [H 2 Ni 31 P 4 (CO) 39 ] n- (n = 4-7) have been recorded. The different spectroelectrochemical behavior of [HNi 31 P 4 (CO) 39 ] 5- and [H 2 Ni 31 P 4 (CO) 39 ] 4- support their formulations as polyhydrides. Unfortunately, all the attempts to directly confirm their poly hydrido nature by 1 H NMR spectroscopy failed, as previously found for related large metal carbonyl clusters. Thus, the presence and number of hydride ligands have been based on the observed protonation/deprotonation reactions and the spectroelectrochemical experiments. The molecular structures of the new clusters have been determined by single-crystal X-ray analysis. These represent the first examples of structurally characterized molecular nickel carbonyl nanoclusters containing interstitial phosphide atoms.

The reaction of [Rh 7 (CO) 16 ] 3- with BiCl 3 under N 2 and at room temperature results in the formation of the new heterometallic [Bi@Rh 12 (CO) 27 ] 3- cluster in high yields. Further controlled addition of BiCl 3 leads first to the formation of the dimeric [(Bi@Rh 12 (CO) 26 ) 2 Bi] 5- and the closo-[Bi@Rh 14 (CO) 27 Bi 2 ] 3- species in low yields, and finally, to the [Bi@Rh 17 (CO) 33 Bi 2 ] 4- cluster. All clusters were spectroscopically characterized by IR and electrospray ionization mass spectrometry, and their molecular structures were fully determined by X-ray diffraction studies. Notably, they represent the first examples of Bi atoms interstitially lodged in metallic cages that, in this specific case, are all based on an icosahedral geometry. Moreover, [Bi@Rh 14 (CO) 27 Bi 2 ] 3- forms an exceptional network of infinite zigzag chains in the solid state, thanks to intermolecular Bi-Bi distances.

The reactions of anionic platinum carbonyl Chini clusters [Pt 3n (CO) 6n ] 2- [n = 2 (1), 3 (2), 4 (3)] with Ag(IPr)Cl [IPr = C 3 N 2 H 2 (C 6 H 3 i Pr 2 ) 2 ] afford the neutral acid-base Lewis adducts [Pt 9 (CO) 18 (AgIPr) 2 ] (4) and [Pt 6 (CO) 12 (AgIPr) 2 ] (5). These are thermally transformed into the homometallic heteroleptic neutral cluster [Pt 3 (CO) 4 (IPr) 2 ] (6). Alternatively, 6 can be obtained from the reactions of 1-3 with an excess of the free IPr carbene ligand. The formation of 6 is sometimes accompanied by trace amounts of [Pt 4 (CO) 4 (IPr) 3 ] (7). The reaction of 6 with free IPr affords the closely related [Pt 3 (CO) 3 (IPr) 3 ] (8) heteroleptic cluster by substitution of the unique terminal CO ligand with a third IPr ligand. The reactions of 1-3 with Ag(IMes)Cl [IMes = C 3 N 2 H 2 (C 6 H 2 Me 3 ) 2 ] proceed differently from those involving Ag(IPr)Cl. Indeed, the only product isolated after workup is the bimetallic tetranuclear cluster [Pt 3 (CO) 3 (IMes) 3 (AgCl)] (9). 9 slowly reacts under a CO atmosphere, resulting in the pentanuclear [Pt 5 (CO) 7 (IMes) 3 ] (10) complex. All of the new clusters 4-10 have been spectroscopically characterized and their molecular structures determined by X-ray crystallography. 4 and 5 retain the original trigonal-prismatic structures of the parent anionic Chini clusters, which are capped by two [Ag(IPr)] + moieties. Conversely, 6-9 are based on a Pt 3 triangular core decorated by CO and N-heterocyclic carbene ligands as well as Pt(CO) (in the case of 7) and AgCl (9) moieties. 10 displays an edge-bridged tetrahedral geometry.

The reactions of [Pt 3n (CO) 6n ] 2- (n = 2-4) homoleptic Chini-type clusters with stoichiometric amounts of Ph 2 PCH 2 CH 2 PPh 2 (dppe) result in the heteroleptic Chini-type clusters [Pt 6 (CO) 10 (dppe)] 2- , [Pt 9 (CO) 16 (dppe)] 2- , and [Pt 12 (CO) 20 (dppe) 2 ] 2- . Their formation is accompanied by slight amounts of neutral species such as Pt 4 (CO) 4 (dppe) 2 , Pt 6 (CO) 6 (dppe) 3 , and Pt(dppe) 2 . A similar behavior was observed with the chiral ligand R-Ph 2 PCH(Me)CH 2 PPh 2 (R-dppp), and two isomers of [Pt 9 (CO) 16 (R-dppp)] 2- were identified. All the new species were spectroscopically characterized by means of IR and 31 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 3 , as well as more rigid bidentate ligands, that is, CH 2 ═C(PPh 2 ) 2 (P^P), CH 2 (PPh 2 ) 2 (dppm), and o-C 6 H 4 (PPh 2 ) 2 (dppb). From a structural point of view, functionalization of anionic platinum Chini clusters preserves their triangular Pt 3 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 9 (CO) 16 (dppe)] 2- , [Pt 9 (CO) 16 (R-dppp)] 2- , [Pt 12 (CO) 22 (PPh 3 ) 2 ] 2- , and [Pt 9 (CO) 16 (PPh 3 ) 2 ] 2- ; an inversion of the cage from trigonal prismatic to octahedral, as observed in [Pt 6 (CO) 10 (dppe)] 2- and [Pt 6 (CO) 10 (PPh 3 ) 2 ] 2- ; the reciprocal rotation of two trigonal prismatic units with the loss of a Pt-Pt contact as found in [Pt 12 (CO) 20 (dppe) 2 ] 2- .

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.

The Co6C(CO)12(AuPPh3)4 carbide carbonyl cluster was obtained from the reaction of [Co6C(CO)15](2-) with Au(PPh3)Cl. This new species was investigated by variable-temperature (31)P NMR spectroscopy, X-ray crystallography, and density functional theory methods. Three different solvates were characterized in the solid state, namely, Co6C(CO)12(AuPPh3)4 (I), Co6C(CO)12(AuPPh3)4·THF (II), and Co6C(CO)12(AuPPh3)4·4THF (III), where THF = tetrahydrofuran. These are not merely different solvates of the same neutral cluster, but they contain three different isomers of Co6C(CO)12(AuPPh3)4. The three isomers I-III possess the same octahedral [Co6C(CO)12](4-) carbido-carbonyl core differently decorated by four [AuPPh3](+) fragments and showing a different Au(I)···Au(I) connectivity. Theoretical investigations suggest that the formation in the solid state of the three isomers during crystallization is governed by packing and van der Waals forces, as well as aurophilic and weak π-π and π-H interactions. In addition, the closely related cluster Co6C(CO)12(PPh3)(AuPPh3)2 was obtained from the reaction of [Co8C(CO)18](2-) with Au(PPh3)Cl, and two of its solvates were crystallographically characterized, namely, Co6C(CO)12(PPh3)(AuPPh3)2·toluene (IV) and Co6C(CO)12(PPh3)(AuPPh3)2·0.5toluene (V). A significant, even if minor, effect of the cocrystallized solvent molecules on the structure of the cluster was observed also in this case.

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 Ni6C(CO)9(AuPPh3)4 bimetallic carbide carbonyl cluster was obtained from the reaction of [Ni9C(CO)17](2-) with Au(PPh3)Cl. It contains a rare carbon-centered (distorted) Ni6C octahedral core decorated by four Au(PPh3) fragments. These are μ3-bonded to four contiguous Ni3-triangular faces and display weak intramolecular Au···Au d(10)-d(10) interactions. The cluster has been characterized in the solid state on two different solvato crystals, i.e., Ni6C(CO)9(AuPPh3)4·THF and Ni6C(CO)9(AuPPh3)4·THF·0.5C6H14. The two solvates show some interesting differences concerning the weak Au···Au contacts. Density functional theory calculations have demonstrated that the presence of the two isomers is related to solid-state packing effects and not to the existence of two double minima in the potential energy surface. This, in turn, confirms that Au···Au d(10)-d(10) interactions are rather soft and thus influenced also by weak van der Waals forces because of the interaction of the cluster with the cocrystallized solvent molecules.

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.

A detailed study of the reaction between [Ni(6)(CO)(12)](2-) and [AuCl(4)](-) afforded the isolation of the new Ni-Au cluster [Ni(12)Au(CO)(24)](3-) as well as identifying an improved synthesis for the previously reported [Ni(32)Au(6)(CO)(44)](6-). The new [Ni(12)Au(CO)(24)](3-) cluster is composed by two [Ni(6)(CO)(12)](2-) moieties coordinated to a central Au(I) ion, as determined by X-ray diffraction. It is noteworthy that the two [Ni(6)(CO)(12)](2-) fragments display different geometries, i.e., trigonal antiprismatic (distorted octahedral) and distorted trigonal prismatic (monocapped square pyramidal). The chemical reactivity of these clusters and their electrochemical behavior have been studied. [Ni(12)Au(CO)(24)](3-) is irreversibly transformed, upon electrochemical reduction, into Au(0) and [Ni(6)(CO)(12)](2-), followed by the reversible reduction of the latter homometallic cluster. Conversely, [Ni(32)Au(6)(CO)(44)](6-) displays five reductions, with apparent features of reversibility, confirming the ability of larger metal carbonyl clusters to reversibly accept and release electrons.

The comparison of five real-time polymerase chain reaction (PCR) methods targeted at maize ( Zea mays ) endogenous sequences is reported. PCR targets were the alcohol dehydrogenase (adh) gene for three methods and high-mobility group (hmg) gene for the other two. The five real-time PCR methods have been checked under repeatability conditions at several dilution levels on both pooled DNA template from several genetically modified (GM) maize certified reference materials (CRMs) and single CRM DNA extracts. Slopes and R(2) coefficients of all of the curves obtained from the adopted regression model were compared within the same method and among all of the five methods, and the limit of detection and limit of quantitation were analyzed for each PCR system. Furthermore, method equivalency was evaluated on the basis of the ability to estimate the target haploid genome copy number at each concentration level. Results indicated that, among the five methods tested, one of the hmg-targeted PCR systems can be considered equivalent to the others but shows the best regression parameters and a higher repeteability along the dilution range. Thereby, it is proposed as a valid module to be coupled to different event-specific real-time PCR for maize genetically modified organism (GMO) quantitation. The resulting practicability improvement on the analytical control of GMOs is discussed.