Generation of AuPd22/Au2Pd21analogues of the high-nuclearity Pd23(CO)20(PEt3)10cluster containing 19-atom centered hexacapped-cuboctahedral (ν2-octahedral) metal fragment: structural-to-synthesis approach concerning formation of Au2Pd21(CO)20(PEt3)10

Heterometallic rhodium clusters as electron reservoirs: Chemical, electrochemical, and theoretical studies of the centered-icosahedral [Rh12E(CO)27]n- atomically precise carbonyl compounds

In this paper, we present a comparative study of the redox properties of the icosahedral [Rh₁₂E(CO)₂₇]^n- (n = 4 when E = Ge or Sn and n = 3 when E = Sb or Bi) family of clusters through in situ infrared spectroelectrochemistry experiments and density functional theory computational studies. These clusters show shared characteristics in terms of molecular structure, being all E-centered icosahedral species, and electron counting, possessing 170 valence electrons as predicted by the electron-counting rules, based on the cluster-borane analogy, for compounds with such metal geometry. However, in some cases, clusters of similar nuclearity, and beyond, may show multivalence behavior and may be stable with a different electron counting, at least on the time scale of the electrochemical analyses. The experimental results, confirmed by theoretical calculations, showed a remarkable electron-sponge behavior for [Rh₁₂Ge(CO)₂₇]^4- (1), [Rh₁₂Sb(CO)₂₇]^3- (3), and [Rh₁₂Bi(CO)₂₇]^3- (4), with a cluster charge going from -2 to -6 for 1 and 3 and from -2 to -7 for cluster 4, making them examples of molecular electron reservoirs. The [Rh₁₂Sn(CO)₂₇]^4- (2) derivative, conversely, presents a limited ability to exist in separable reduced cluster species, at least within the experimental conditions, while in the gas phase it appears to be stable both as a penta- and hexa-anion, therefore showing a similar redox activity as its congeners. As a fallout of those studies, during the preparation of [Rh₁₂Sb(CO)₂₇]^3-, we were able to isolate a new species, namely, [Rh₁₁Sb(CO)₂₆]^2-, which presents a Sb-centered nido-icosahedral metal structure possessing 158 cluster valence electrons, in perfect agreement with the polyhedral skeletal electron pair theory.

Ion exchange of protons by coinage metals to give gold and silver encapsulation within a pseudo-D2d distorted face-capped Pd14 cubic kernel: [(μ14-M)Pd22(CO)20(PEt3)8]+ (M = Au, Ag)

Heart of gold (or silver): The pseudo-D2d distorted MPd14 cubic kernel of [(μ14-M)Pd22(CO)20(PEt3)8](+) cations, with M = Au (1), Ag (2), has an encapsulated M atom (see picture; yellow) coordinated to eight cubic corner (black) and six face-capping Pd atoms (gray). Compounds 1 and 2 were obtained (28-60 % yields) from two-step/one-pot reactions of a Pd10 precursor with CF3CO2 H followed by coinage-metal ion exchange of protons.

PPh3-derivatives of [Pt3n(CO)6n]2- (n = 2-6) Chini's clusters: syntheses, structures, and 31P NMR studies

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.

Syntheses, structures and properties of primarily nanosized homo/heterometallic palladium CO/PR3-ligated clusters

Syntheses, properties and structures of nanosized palladium CO/PR(3)-ligated homo- and heterometallic clusters containing up to 165 metal atoms are the focus of this review. The work discussed is primarily that of the authors and their coworkers. We propose that the unparalleled variety of structural types and the distinctive reactivities of neutral Pd(n)(CO)(x)(PR(3))(y) clusters composed of zerovalent Pd atoms are a consequence of relatively weak Pd-L(ligand) and Pd(0)-Pd(0) interactions that result from the stable 5s(0)4d(10) closed-shell electron configuration of atomic Pd in its ground state.

Nanosized (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) Containing Pt-Centered Four-Shell 165-Atom Pd−Pt Core with Unprecedented Intershell Bridging Carbonyl Ligands: Comparative Analysis of Icosahedral Shell-Growth Patterns with Geometrically Related Pd145(CO)x(PEt3)30 (x ≈ 60) Containing Capped Three-Shell Pd145 Core

Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, (mu(12)-Pt)Pd(164-x)Pt(x)(CO)(72)(PPh(3))(20) (x approximately 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd(145) cluster, Pd(145)(CO)(x)(PEt(3))(30) (x approximately 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochemical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (<10%) from the reaction of Pd(10)(CO)(12)(PPh(3))(6) with Pt(CO)(2)(PPh(3))(2). Its 165-atom metal-core geometry and 20 PPh(3) and 72 CO ligands were established from a low-temperature (100 K) CCD X-ray diffraction study. The well-determined crystal structure is attributed largely to 1 possessing cubic T(h) (2/m3) site symmetry, which is the highest crystallographic subgroup of the noncrystallographic pseudo-icosahedral I(h) (2/m35) symmetry. The "full" four-shell Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered (mu(12)-Pt) atom encapsulated by the 12-atom icosahedral Pt(x)Pd(12-x) cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt(x)Pd(42-x) cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral Pt(x)Pd(60-x) cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd(50) cage. The total number of crystallographically estimated Pt atoms, 8 +/- 3, which was obtained from least-squares (Pt(x)/Pd(1-x))-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement with that of 7.6(7) found from an X-ray Pt/Pd microanalysis (WDS spectrometer) on three crystals of 1. Our utilization of this site-occupancy (Pt(x)Pd(1-x))-analysis for shells 1-3 originated from the microanalytical results; otherwise, the presumed metal-core composition would have been (mu(12)-Pt)Pd(164). [Alternatively, the (mu(12)-Pt)M(164) core-geometry of 1 may be viewed as a pseudo-Ih Pt-centered six-shell successive nu(1) polyhedral system, each with radially equivalent vertex atoms: Pt@M(12)(icosahedron)@M(30)(icosidodecahedron)@M(12)(icosahedron)@M(60)(rhombicosidodecahedron)@M(30)(icosidodecahedron)@M(20)(pentagonal dodecahedron)]. Completely surprising structural dissimilarities between 1 and 2 are: (1) to date 1 is only reproducibly isolated as a heterometallic Pd-Pt cluster with a central Pt instead of Pd atom; (2) the 50 atoms comprising the outer fourth nu(2) pentagonal dodecahedral shell in 1 are less than the 60 atoms of the inner third shell in 1, in contradistinction to shell-by-shell growth processes in all other known shell-based structures; (3) the 10 fewer PR3 ligands in 1 necessitate larger bulky PPh(3) ligands to protect the Pd-Pt core-geometry; (4) the 72 CO ligands consist of six bridging COs within each of the 12 pentagons in shell 4 that are coordinated to intershell metal atoms. SQUID magnetometry measurements showed a single-crystal sample of 1 to be diamagnetic over the entire temperature range of 10-300 K.

Gold(I) and Silver(I) Mixed-Metal Trinuclear Complexes: Dimeric Products from the Reaction of Gold(I) Carbeniates or Benzylimidazolates with Silver(I) 3,5-Diphenylpyrazolate

Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees .

Mixed-Metal Triangular Trinuclear Complexes: Dimers of Gold−Silver Mixed-Metal Complexes from Gold(I) Carbeniates and Silver(I) 3,5-Diphenylpyrazolates

Dimers of trinuclear mixed gold-silver compounds are obtained by the reaction of a gold(I) carbeniate, [Au(mu-C(OEt)=NC6H4-p-CH3)]3, with a silver(I) pyrazolate, [Ag(mu-3,5-Ph2pz)]3. The crystalline products are the mixed-metal species Au(carb)Ag2(mu-3,5-Ph2pz)2 and Au2(carb)2Ag(mu-3,5-Ph2pz)CCH2Cl2.

Nanosized Au2Pd41(CO)27(PEt3)15containing two geometrically unprecedented 13-coordinated Au-centered (μ13-Au)Pd13polyhedra connected by triangular face-sharing and three interpenetrating 12-coordinated Pd-centered (μ12-Pd)Au2Pd10icosahedra: geometrical change in centered polyhedra induced by Au/Pd electronegativity-mismatch

The synthesis, isolation, and stereochemical characterization of Au(2)Pd(41)(CO)(27)(PEt(3))(15)(1) are described. This nanosized Au(2)Pd(41) cluster (maximum metal-core diameter, 1.04 nm) was originally obtained with Au(2)Pd(21)(CO)(20)(PEt(3))(10) as low-yield by-products together with Pd(145)(CO)(x)(PEt(3))(30)(x approximately 60) from the reaction of Pd(PEt(3))(2)Cl(2) and Au(PPh(3))Cl in DMF with NaOH under CO atmosphere. The subsequent preparation of Au(2)Pd(21)(CO)(20)(PEt(3))(10) in greatly improved yields (preceding article) thereby provided the starting material that led to the isolation of 1 in reasonable yields (54%) from an overnight refluxing of the preformed Au(2)Pd(21) cluster in THF under N(2). Both the composition (subsequently ascertained from elemental analysis) and molecular geometry of 1 were unequivocally established from a low-temperature CCD X-ray diffraction study, which revealed a cubic unit cell of P2(1)3 symmetry with four molecules of 1 and four co-crystallized triphenylphosphine oxide molecules each lying on a crystallographic three-fold axis. The entire Au(2)Pd(41) core of pseudo-C(3h) symmetry may be viewed as a central Au(2)Pd(29) fragment of pseudo-D(3h) symmetry composed of two heretofore geometrically unknown 13-coordinated Au-centered (mu(13)-Au)Pd(13) polyhedra that share a common internal Pd(i)(3) triangular face perpendicular to the C(3) principal axis and of three three-fold-related interpenetrating 12-coordinated Pd-centered (mu(12)-Pd)Au(2)Pd(10) icosahedra. A comparative analysis of this central Au(2)Pd(29) fragment in with an internal Au(i)(2)Pd(i)(3) trigonal bipyramid vs. the corresponding central Pd(29) fragment in the known homopalladium Pd(35)(CO)(23)(PMe(3))(15) (2) with an internal Pd(i)(5) trigonal bipyramid resulting from five interpenetrating 12-coordinated Pd-centered [(mu(12)-Pd)Pd(12)] icosahedra is particularly illuminating; it provides a striking illustration of the remarkable observed difference between Pd- vs. Au-centered polyhedra which is attributed to a large electronegativity-mismatch in radial bonding interactions that occurs upon replacement of the Pd-centered atom with a highly electronegative Au-centered atom. The entire Au(2)Pd(41) core-geometry is obtained by additional face-condensations of 12 tetracapping Pd(cap) atoms. This cluster is stabilized by 15 PEt(3) ligands and 27 doubly- and triply-bridging CO ligands. A close geometrical resemblance between the three three-fold-related Au(2)Pd(14) moities within the Au(2)Pd(41) core in 1 and the entire Au(2)Pd(14) core in the known [Au(2)Pd(14)(CO)(9)(PMe(3))(11)](2+) dication (3) is observed; resulting stereochemical implications are given.