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14 páginas, 12 figuras, 8 tablas, 5 esquemas., The reaction of [NBu4]2[(C6F5)2Pt(μ-PPh2)2Pd(μ-PPh2)2Pt(C6F5)2] (1a) with [AgPPh3]+ results in the oxidation of two bridging diphenylphosphanides to give the 46e species [(PPh3)(C6F5)2Pt2(μ-P2Ph2)Pd(μ-PPh2)(μ-Ph2P4−P3Ph2)Pt1(C6F5)2] (3). Complex 3 displays two tetracoordinated terminal platinum centers and a central Pd atom that is bonded to three P atoms and that completes its coordination sphere by a rather long (3.237 Å) dative Pt2 → Pd bond. Complex 3 is also obtained when [(RF)2Pt(μ-PPh2)Pd(μ-PPh2)(μ-Ph2P-PPh2)Pt(RF)2] (2) is reacted with PPh3. Analogously, the addition of PPh2Et, CO or pyridine to 2 affords the 46e complexes of general formula [(L)(C6F5)2Pt2(μ-P2Ph2)Pd(μ-PPh2)(μ-Ph2P4−P3Ph2)Pt1(C6F5)2] (L = PPh2Et, 4; L = CO, 6; L = pyridine, 7). The geometry around Pt2 is determined by the bulkiness of L bonded to Pt. Thus, in complexes 3 (L = PPh3) and 4 (L = PPh2Et), the ligand L occupies the trans position with respect to μ-P2, and in 6 (L = CO), the ligand L occupies the cis position with respect to μ-P2. Interestingly, for 7 (L = py), both isomers 7-trans and 7-cis, could be isolated. Although 4 did not react with an excess of PPh2Et, the reaction with the less sterically demanding CH3CN ligand resulted in the opening of the Pt2−P2−Pd cycle with formation of the saturated 48e species [(PPh2Et)(C6F5)2Pt(μ-PPh2)Pd(MeCN)(μ-PPh2)(μ-Ph2P-PPh2)Pt(C6F5)2] (8). The saturated 48e complex [(CO)(C6F5)2Pt(μ-PPh2)Pd(MeCN)(μ-PPh2)(μ-Ph2P-PPh2)Pt(C6F5)2] (9) was obtained by acetonitrile addition to 6. Beside the hindered rotation of the pentafluorophenyl groups and a flip-flop motion of the Pd−P−Pt1−P−P ring observed at low T, a rotation about the Pt2−P2 bond and a P−C oxidative addition/reductive elimination process occur for 3 and 4 at room temperature. A “through-space” 19F−31P spin−spin coupling between an ortho-F and the P4 is observed for complexes 3 and 4, having the C6F5 groups bonded to Pt2 in mutually trans position. The XRD structures of complexes 3, 6, 7-trans, 7-cis, 8, and 9 are described., This work was supported by the Spanish MICINN (DGI)/FEDER (Project CTQ2008-06669-C02-01/ BQU and the Gobierno de Arag on (Grupo de Excelencia: Química Inorg anica y de los Compuestos Organomet alicos). S. I. gratefully acknowledges the grant provided by the Ministerio de Educaci on y Ciencia. Italian MIUR (PRIN project n. 2007 2RLL2) and COST PhoSciNet (project CM082) are also gratefully acknowledged.

The two-electron oxidation reactions of the [NBu4]2[(C6F5)2M(μ-PPh2)2M‘(C6F5)2] (M = M‘ = Pt, 1a; M = M‘ = Pd, 1b; M = Pt, M‘ = Pd, 1c) complexes using I2 as oxidant have been investigated by experimental and electronic structure calculation methods. The geometric and energetic reaction profiles in a vacuum have been investigated at the B3LYP/LANL2DZ level. The first step of the oxidation processes involves the oxidative addition of I2 to one of the four-coordinate M(II) metal centers yielding a five-coordinate intermediate with square pyramidal stereochemistry. The oxidized [(I)L2M(μ-PH2)2M‘L2]- (L = CN) complex converts to a more stable intermediate involving a planar dimetallacycle five-membered ring, which through a reactant-like transition state surmounting a relatively low barrier of 18.5, 8.7, and 8.9 kcal/mol for Pt2, PtPd, and Pd2 compounds, respectively, yields the final product. At this stage an unusual intramolecular reductive coupling of one of the ancillary ligands with a bridging phosphido ligand takes place, affording the “M(II)(μ-PH2)(μ-I)M‘(II)” framework. This process is exoergic by 11.4, 18.2, and 18.8 kcal/mol for Pt2, PtPd, and Pd2 compounds, respectively. For the Pt2 and PtPd complexes removal of the iodide ligand from the oxidized iodo complexes yields the very unusual [L2MIII(μ-PH2)2M‘IIIL2] (L = CN or C6F5) complexes. In contrast, [L2PdIII(μ-PH2)2PdIIIL2] does not exist as local minima in the PES, but the [L2PdII(μ-PH2)PdII(PH2L)L] species was identified, resulting from the intramolecular reductive coupling promoted by the iodide ligand abstraction. This species could be considered as an intermediate for the reverse intramolecular oxidative addition of the PH2L ligand promoted by iodide abstraction with Ag+ ions. Finally, the molecular structure of the [(C6F5)2Pt(μ-PPh2)(μ-I)Pd(C6F5){PPh2(C6F5)}] complex has been established by X-ray crystallography., We thank the Ministerio de Ciencia y Tecnología y Fondos FEDER for its financial support (Project BQU2002-03997-CO2-02) and the Agencia Española de Cooperación Internacional (Ministerio de Asuntos Exteriores) for a grant to N.Ch.

The reaction between [(C6F5)2Pt(μ-PPh2)2Pt(PPh2R)2] and [Pt(C7H10)3] in toluene yields the triangulo complexes [Pt3(μ-PPh2)2(μ-C6F5)(C6F5)(PPh2R)2] (R = Ph 4, Me 5, Et 6), which contain two phosphido and one pentafluophenyl bridging ligands and two phosphines and one pentafluophenyl terminal ones. The triangulo metal core displays three Pt−Pt bonds, as expected for a 42 valence electron count cluster. The basicity of these metal cores is demonstrated through the reaction of one of the complexes (R = Ph) with AgClO4 or [Ag(OClO3)(PPh3)], which gives the corresponding adduct [Pt3(AgOClO3)(μ-PPh2)2(μ-C6F5)(C6F5)(PPh3)2] (7) or [Pt3Ag(μ-PPh2)2(μ-C6F5)(C6F5)(PPh3)3][ClO4] (8). The X-ray structures of 4 and 7 have been determined.

The synthesis of the trinuclear phosphido complexes [NBu4]2[(C6F5)2M(μ-PPh2)2M‘(μ-PPh2)2M‘ ‘(C6F5)2] (M, M‘, M‘ ‘ = Pd(II), Pt(II), 1−5) is described. A study of the electrochemical behavior of these complexes is reported. The chemical oxidation of the homonuclear platinum derivative involving two electrons yields the complex [(C6F5)2Pt(μ-PPh2)2Pt(μ-PPh2)2Pt(C6F5)2] (6), which contains Pt in average formal oxidation state 2.67. The structure of the complexes has been established by spectroscopic means, and X-ray diffraction studies have been carried out on 1 and 6. Quantum chemical calculations at the B3LYP level of theory, using the LANL2DZ basis set, provide a satisfactory description of the structural, bonding, energetic, and electronic properties of these phosphido-bridged trinuclear M3(II) compounds modeled as [(CF3)2M(μ-PH2)2M‘(μ-PH2)2M‘ ‘(CF3)2]2- (M, M‘, M‘ ‘ = Pd(II), Pt(II), 1M−5M) and the oxidation product [Pt3(μ-PH2)4(CF3)4] (6M).

8 pages, 3 tables, 4 schemes, 3 figures.-- Supporting Information Available: http://pubs.acs.org., The reaction of [NBu4]2[{(C6F5)2Pt(μ-PPh2)2Pt(μ-Cl)}2] with AgClO4 in CH2Cl2 (1:2 mol ratio) gives the neutral tetranuclear compound [Pt4(μ-PPh2)3{μ3-PPh(1,2-η2-Ph)-κ3P)}(C6F5)4] (5), a 58-electron cluster that displays three Pt−Pt bonds and a 1,2-η2-Ph (of the PPh2 ligand) Pt interaction. This complex reacts with bipy or phen (L−L), giving the tetranuclear clusters [Pt4(μ-PPh2)4(C6F5)4(L−L)] (L−L = bipy 6, phen 7), while its reaction with CO in CH2Cl2 renders [{Pt2(μ-PPh2)2(C6F5)2(CO)}2] (8). The molecular structures of complexes 5 and 6 have been established by X-ray crystallography, and the structure of 8 is inferred by 31P NMR spectroscopy., We thank the Dirección General de Enseñanza Superior (Spain) for financial support (Project PB98-1595-C02-01). E.A. and A.M. acknowledge the Diputación General de Aragón or DGES (Spain) respectively for their grants.

The reaction of [NBu4]2[{(C6F5)2Pt(μ-PPh2)2Pt(μ-Cl)}2], A, with CO in CH2Cl2 gives the expected dinuclear compound [NBu4][(C6F5)2Pt(μ-PPh2)2PtCl(CO)], 1, which reacts with AgClO4 (1:1 molar ratio) in CH2Cl2 to produce the tetranuclear cluster [Pt4(μ-PPh2)4(C6F5)4(CO)2], 2. The analogous complex [NBu4]2[{(C6F5)2Pt(μ-PPh2)2Pd(μ-Cl)}2], B, does not react with CO under similar conditions, but treatment of B with AgClO4 (1:2 molar ratio, CH2Cl2) renders the tetranuclear compound [Pt2Pd2(μ-PPh2)3(C6F5)3(PPh2C6F5)], 3, in which the PPh2C6F5 ligand is produced through an unusual M−PPh2/M−C6F5 reductive coupling. Complex 3 reacts with CO in CH2Cl2 producing the tetranuclear complex [Pt2Pd2(μ-PPh2)2(μ3-PPh(1,2-η2-Ph)-κ3P)(C6F5)3(CO)(PPh2C6F5)], 4. The molecular structures of complexes 2 and 4 have been established by X-ray crystallography., We thank the Dirección General de Enseñanza Superior (Spain) for financial support (Project Nos. PB95-0003-CO2-01 and PB95-0792).

Anionic tetranuclear complexes with the molecular formula [NBu4]2[Pd4(μ-PPh2)2(μ-X)4(C6F5)4] [X = Cl (1), Br (2)] were obtained by reaction of [NBu4]2[Pd2(μ-PPh2)2(C6F5)4] and PdCl2 (or K2[PdCl4]) in acetone, followed by reaction with KBr for 2. The reactions of 1 with neutral monodentate (L) or bidentate (L-L) ligands afford the dinuclear derivatives [Pd2(μ-PPh2)(μ-Cl)(C6F5)2L2] [L = PPh3 (3), py (4)] or [Pd2(μ-PPh2)(C6F5)2(L-L)2]n [n = 1−, L-L = acac (6); n = 1+, L-L = bipy (7) or phen (8)]. The structures of complexes 1 and 7 were determined by single-crystal X-ray diffraction studies. The bis(acetone) solvate of complex 1, [NBu4]2[Pd4(μ-PPh2)2(μ-Cl)4(C6F5)4]·2C3H6O, crystallizes in the monoclinic system, space group P21/c, with a = 11.679(5) Å, b = 16.552(7) Å, c = 23.868(8) Å, β = 101.10(3)°, V = 4527.6(15) Å3, and Z = 2. The central core of the anion has the shape of a rectangle with the four Pd atoms in the corners. The hexane solvate of complex 7, [Pd2(μ-PPh2)(C6F5)2(bipy)2][ClO4]·C6H14, crystallizes in the monoclinic system, space group P21/n, with a = 16.214(3) Å, b = 10.311(2) Å, c = 28.380(6) Å, β = 100.82(3)°, V = 4660(2) Å3, and Z = 4. In both complexes, the long Pd···Pd distances (>3.1 Å) clearly point to the absence of any Pd−Pd interaction.