Synthesis and Chemical and Electrochemical Characterization of Fe-S Carbonyl Clusters. X-ray Crystal Structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)

A reinvestigation of the redox behavior of the [Fe(3)(&mgr;(3)-S)(CO)(9)](2)(-) dianion led to the isolation and characterization of the new [Fe(5)S(2)(CO)(14)](2)(-), as well as the known [Fe(6)S(6)(CO)(12)](2)(-) dianion. As a corollary, new syntheses of the [Fe(3)S(CO)(9)](2)(-) dianion are also reported. The [Fe(5)S(2)(CO)(14)](2)(-) dianion has been obtained by oxidative condensation of [Fe(3)S(CO)(9)](2)(-) induced by tropylium and Ag(I) salts or SCl(2), or more straightforwardly through the reaction of [Fe(4)(CO)(13)](2)(-) with SCl(2). The [Fe(6)S(6)(CO)(12)](2)(-) dianion has been isolated as a byproduct of the synthesis of [Fe(3)S(CO)(9)](2)(-) and [Fe(5)S(2)(CO)(14)](2)(-) or by reaction of [Fe(4)(CO)(13)](2)(-) with elemental sulfur. The structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)] were determined by single-crystal X-ray diffraction analyses. Crystal data: for [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)], monoclinic, space group P2(1)/c (No. 14), a = 24.060(5), b = 14.355(6), c = 23.898(13) ?, beta = 90.42(3) degrees, Z = 4; for [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)], monoclinic, space group C2/c (No. 15), a = 34.424(4), b = 14.081(2), c = 19.674(2) ?, beta = 115.72(1) degrees, Z = 4. The new [Fe(5)S(2)(CO)(14)](2)(-) dianion shows a "bow tie" arrangement of the five metal atoms. The two Fe(3) triangles sharing the central Fe atom are not coplanar and show a dihedral angle of 55.08(3) degrees. Each Fe(3) moiety is capped by a triply bridging sulfide ligand. The 14 carbonyl groups are all terminal; two are bonded to the unique central atom and three to each peripheral iron atom. Protonation of the [Fe(5)S(2)(CO)(14)](2)(-) dianion gives reversibly rise to the corresponding [HFe(5)S(2)(CO)(14)](-) monohydride derivative, which shows an (1)H-NMR signal at delta -21.7 ppm. Its further protonation results in decomposition to mixtures of Fe(2)S(2)(CO)(6) and Fe(3)S(2)(CO)(9), rather than formation of the expected H(2)Fe(5)S(2)(CO)(14) dihydride. Exhaustive reduction of [Fe(5)S(2)(CO)(14)](2)(-) with sodium diphenyl ketyl progressively leads to fragmentation into [Fe(3)S(CO)(9)](2)(-) and [Fe(CO)(4)](2)(-), whereas electrochemical, as well as chemical oxidation with silver or tropylium tetrafluoroborate, in dichloromethane, generates the corresponding [Fe(5)S(2)(CO)(14)](-) radical anion which exhibits an ESR signal at g = 2.067 at 200 K. The electrochemical studies also indicated the existence of a subsequent one-electron anodic oxidation which possesses features of chemical reversibility in dichloromethane but not in acetonitrile solution. A reexamination of the electrochemical behavior of the [Fe(3)S(CO)(9)](2)(-) dianion coupled with ESR monitoring enabled the spectroscopic characterization of the [Fe(3)S(CO)(9)](-) radical monoanion and demonstrated its direct involvement in the generation of the [Fe(5)S(2)(CO)(14)](n)()(-) (n = 0, 1, 2) system.     

Acceptor (CF3)PCPH pincer reactivity with (PPh3)3Ir(CO)H

The syntheses of Ir(I) and Ir(III) complexes incorporating the electron-withdrawing pincer ligand (1,3-C(6)H(4)(CH(2)P(CF(3))(2))(2)) ((CF(3))PCPH) with (PPh(3))(3)Ir(CO)H and subsequent chemistry are reported. Under ambient conditions, reaction of 1 equiv. (CF(3))PCPH with (PPh(3))(3)Ir(CO)H gave the mono-bridged complex [Ir(CO)(PPh(3))(2)(H)](2)(μ-(CF(3))PCPH) (1). Reaction of (PPh(3))(3)Ir(CO)H with excess (CF(3))PCPH and MeI gave the doubly-bridged complex [Ir(CO)(PPh(3))(H)](2)(μ-(CF(3))PCPH)(2) (2), whereas the tetrameric oligomer [Ir(CO)(PPh(3))(H)](4)(μ-(CF(3))PCPH)(4) (2-sq) was obtained from a 1:1 ligand:metal mixture in benzene in the presence of excess MeI. At higher temperatures (165 °C) the reaction of (CF(3))PCPH with (PPh(3))(3)Ir(CO)H afforded the 5-coordinate Ir(I) complex ((CF(3))PCP)Ir(CO)(PPh(3)) (3). Complex 3 shows mild catalytic activity for the decarbonylation of 2-naphthaldehyde in refluxing diglyme (162 °C).     

Preparation and characterization of the argentates: [Ag[P(CF(3))(2)](2)](-), [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-) (M = Cr, W), and [Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)](-): X-ray crystal structure of [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)

The first example of a mononuclear diphosphanidoargentate, bis[bis(trifluoromethyl)phosphanido]argentate, [Ag[P(CF(3))(2)](2)](-), is obtained via the reaction of HP(CF(3))(2) with [Ag(CN)(2)](-) and isolated as its [K(18-crown-6)] salt. When the cyclic phosphane (PCF(3))(4) is reacted with a slight excess of [K(18-crown-6)][Ag[P(CF(3))(2)](2)], selective insertion of one PCF(3) unit into each silver phosphorus bond is observed, which on the basis of NMR spectroscopic evidence suggests the [Ag[P(CF(3))P(CF(3))(2)](2)](-) ion. On treatment of the phosphane complexes [M(CO)(5)PH(CF(3))(2)] (M = Cr, W) with [K(18-crown-6)][Ag(CN)(2)], the analogous trinuclear argentates, [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-), are formed. The chromium compound [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)] crystallizes in a noncentrosymmetric space group Fdd2 (No. 43), a = 2970.2(6) pm, b = 1584.5(3) pm, c = 1787.0(4), V = 8.410(3) nm(3), Z = 8. The C(2) symmetric anion, [Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)](-), shows a nearly linear arrangement of the P-Ag-P unit. Although the bis(pentafluorophenyl)phosphanido compound [Ag[P(C(6)F(5))(2)](2)](-) has not been obtained so far, the synthesis of its trinuclear counterpart, [K(18-crown-6)][Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)], was successful.     

Synthesis, Characterization, and Comparative Properties of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)

The reaction of [PPN](2)[Re(6)C(CO)(19)] with Mo(CO)(6) and Ru(3)(CO)(12) under sunlamp irradiation provided the new mixed-metal clusters [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)], which were isolated in yields of 85% and 61%, respectively. The compound [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] crystallizes in the monoclinic space group P2(1)/c with a = 20.190 (7) ?, b = 16.489 (7) ?, c = 27.778 (7) ?, beta = 101.48 (2) degrees, and Z = 4 (at T = -75 degrees C). The cluster anion is composed of a Re(6)C octahedral core with a face capped by a Mo(CO)(4) fragment. There are three terminal carbonyl ligands coordinated to each rhenium atom. The four carbonyl ligands on the molybdenum center are essentially terminal, with one pair of carbonyl ligands (C72-O72 and C74-O74) subtending a relatively large angle at molybdenum (C72-Mo-C74 = 147.2(9) degrees ), whereas the remaining pair of carbonyl ligands (C71-O71 and C73-O73) subtend a much smaller angle (C71-Mo-C73 = 100.5(9) degrees ). The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows signals for four sets of carbonyl ligands at -40 degrees C, consistent with the solid state structure, but the carbonyl ligands undergo complete scrambling at ambient temperature. The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] at 20 degrees C is consistent with the expected structure of an octahedral Re(6)C(CO)(18) core capped by a Ru(CO)(3) fragment. The visible spectrum of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows a broad, strong band at 670 nm (epsilon = 8100), whereas all of the absorptions of [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] are at higher energy. An irreversible oxidation wave with E(p) at 0.34 V is observed for [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)], whereas two quasi-reversible oxidation waves with E(1/2) values of 0.21 and 0.61 V (vs Ag/AgCl) are observed for [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)]. The molybdenum cap in [Re(6)C(CO)(18)Mo(CO(4))](2-) is cleaved by heating in donor solvents, and by treatment with H(2), to give largely [H(2)Re(6)C(CO)(18)](2-). In contrast, [Re(6)C(CO)(18)Ru(CO)(3)](2-) shows no tendency to react under similar conditions.     

A kinetic and thermodynamic study of the unexpected comproportionation reaction between cis-[Os(VIII)O4(OH)2](2-) and trans-[Os(VI)O2(OH)4](2-) to form a postulated [Os(VII)O3(OH)3](2-) complex anion

A kinetic study of [OsO(4)] reduction by aliphatic alcohols (MeOH and EtOH) was performed in a 2.0 M NaOH matrix at 298.1 K. The rate model that best fitted the UV-VIS data supports a one-step, two electron reduction of Os(VIII) (present as both the [Os(VIII)O(4)(OH)](-) and cis-[Os(VIII)O(4)(OH)(2)](2-) species in a ratio of 0.34:0.66) to form the trans-[Os(VI)O(2)(OH)(4)](2-) species. The formed trans-[Os(VI)O(2)(OH)(4)](2-) species subsequently reacts relatively rapidly with the cis-[Os(VIII)O(4)(OH)(2)](2-) complex anion to form a postulated [Os(VII)O(3)(OH)(3)](2-) species according to: cis-[Os(VIII)O(4)(OH)(2)](2-) + trans-[Os(VI)O(2)(OH)(4)](2-) (k+2) (k-2) 2[Os(VII)O(3)(OH)(3)](2-). The calculated forward, k(+2), and reverse, k(-2), reaction rate constants of this comproportionation reaction are 620.9 ± 14.6 M(-1) s(-1) and 65.7 ± 1.2 M(-1) s(-1) respectively. Interestingly, it was found that the postulated [Os(VII)O(3)(OH)(3)](2-) complex anion does not oxidize MeOH or EtOH. Furthermore, the reduction of Os(VIII) with MeOH or EtOH is first order with respect to the aliphatic alcohol concentration. In order to corroborate the formation of the [Os(VII)O(3)(OH)(3)](2-) species predicted with the rate model simulations, several Os(VIII)/Os(VI) mole fraction and mole ratio titrations were conducted in a 2.0 M NaOH matrix at 298.1 K under equilibrium conditions. These titrations confirmed that the cis-[Os(VIII)O(4)(OH)(2)](2-) and trans-[Os(VI)O(2)(OH)(4)](2-) species react in a 1:1 ratio with a calculated equilibrium constant, K(COM), of 9.3 ± 0.4. The ratio of rate constants k(+2) and k(-2) agrees quantitatively with K(COM), satisfying the principle of detailed balance. In addition, for the first time, the molar extinction coefficient spectrum of the postulated [Os(VII)O(3)(OH)(3)](2-) complex anion is reported.     

Homoleptic, sigma-bonded octahedral superelectrophilic metal carbonyl cations of iron(II), ruthenium(II), and osmium(II). Part 2: Syntheses and characterizations of [M(CO)(6)][BF(4)](2) (M = Fe, Ru, Os)

As the first examples of homoleptic, sigma-bonded superelectrophilic metal carbonyl cations with tetrafluoroborate [BF(4)](-) as the counter anions three thermally stable salts of the composition [M(CO)(6)][BF(4)](2) (M = Fe, Ru, Os) have been synthesized and extensively characterized by thermochemical, structural, and spectroscopic methods. A common synthetic route, the oxidative carbonylation of either Fe(CO)(5) (XeF(2) as the oxidizer) or M(3)(CO)(12) (M = Ru, Os) (F(2) as the oxidizer) in the conjugate Bronsted-Lewis superacid HF/BF(3), was employed. The thermal behavior of the three salts, studied by differential scanning calorimetry (DSC) and gas-phase IR spectroscopy of the decomposition products, has been compared to that of the corresponding [SbF(6)](-) salts. The molecular structures of [M(CO)(6)][BF(4)](2) (M = Fe, Os) were obtained by single-crystal X-ray diffraction at 100 K. X-ray powder diffraction data for [M(CO)(6)][BF(4)](2) (M = Ru, Os) were obtained between 100 and 300 K in intervals of 50 K. All three salts are isostructural and crystallized in the tetragonal space group I4/m (No. 87). As for the corresponding [M(CO)(6)][SbF(6)](2) salts (M = Fe, Ru, Os), similar unit cell parameters and vibrational fundamentals were also found for the three [BF(4)](-) compounds. For the structurally characterized salts [M(CO)(6)][BF(4)](2) (M = Fe, Os), very similar bond parameters for both cations and anions were found. Hence, the invariance of structural and spectroscopic properties of [M(CO)(6)](2+) cations (M = Fe, Ru, Os) extended from the fluoroantimonates [Sb(2)F(11)](-) and [SbF(6)](-) as counteranions also to [BF(4)](-).     

Intramolecularly coordinated heteroleptic organostannylene tungsten pentacarbonyl complexes 4-tBu-2,6-[P(O)(OiPr)2]2C6H2Sn(X)W(CO)5 (X = Cl, F, PPh2, PPh2[W(CO)5]). Syntheses and reactivity

The synthesis of the intramolecularly coordinated heteroleptic organostannylene tungsten pentacarbonyl complexes 4-tBu-2,6-[P(O)(OiPr)(2)](2)C(6)H(2)Sn(X)W(CO)(5) (1, X = Cl; 2, X = F; 3, X = PPh(2)) and of 4-tBu-2,6-[P(O)(OiPr)(2)](2)C(6)H(2)Sn[W(CO)(5)]PPh(2)[W(CO)(5)], 4, are reported. UV-irradiation of compound 4 in tetrahydrofurane serendipitously gave the bis(organostannylene) tungsten tetracarbonyl complex cyclo-O(2)W[OSn(R)](2)W(CO)(4) (R = 4-tBu-2,6-[P(O)(OiPr)(2)](2)C(6)H(2)), 5, that contains an unprecedented W(0)-Sn-O-W(vi) bond sequence. The compounds 1-5 were characterized by means of single crystal X-ray diffraction analysis, (1)H, (13)C, (19)F, (31)P, (119)Sn NMR, and IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and elemental analysis. Compound 4 features a hindered rotation about the Sn-P bond.     

Oxidative addition of silanes R3SiH to the unsaturated cluster [Os3(micro-H)[micro3-Ph2PCH2PPh(C6H4)](CO)8]: evidence for reversible silane formation in the dynamic behaviour of [Os3(micro-H)(SiR3)(CO)9(micro-dppm)

Oxidative addition of the silanes R(3)SiH (R(3)= Ph(3), Et(3), EtMe(2)) to the unsaturated cluster [Os(3)(micro-H)[micro(3)-Ph(2)PCH(2)PPh(C(6)H(4))](CO)(8)] leads to the saturated clusters [Os(3)(micro-H)(SiR(3))(CO)(9)(micro-dppm)](SiR(3)= SiPh(3) 1, SiEt(3) 2 and SiEtMe(2)3) and the unsaturated clusters [Os(3)(micro -H)(2)(SiR(3))[micro(3)-Ph(2)PCH(2)PPh(C(6)H(4))](CO)(7)](SiR(3)= SiPh(3) 4, SiEt(3) 5 and SiEtMe(2)6). Structures are based on spectroscopic evidence and a XRD structure of [Os(3)(micro-H)(SiPh(3))(CO)(9)(micro-dppm)] 1 in which all non-CO ligands are coordinated equatorially and the hydride and the silyl groups are mutually cis. From variable-temperature (1)H NMR spectra of the SiEt(3) compound 2, exchange of the P nuclei is clearly apparent. Simultaneous migrations of the SiEt(3) group and of the hydride from one Os-Os edge to another generate a time-averaged mirror plane in the molecule. VT (1)H NMR spectra of the somewhat less bulky compound [Os(3)(micro-H)(SiMe(2)Et)(CO)(9)(micro-dppm)] 3 have been analysed. Two isomers 3a and 3b are observed with the hydride ligand located on different Os-Os edges. Synchronous migration of the hydride and SiMe(2)Et groups is faster than the observed interconversion of isomers which occurs by hydride migration alone. The synchronous motion of H and SiR(3)only occurs when these ligands are mutually cis as in the major isomer 3a and we propose that this process requires the formation of a transient silane complex of the type [Os(3)(eta(2)-HSiR(3))(CO)(9)(micro-dppm)]. Turnstile rotation within an Os(CO)(3)(eta(2)-HSiR(3)) group leads to the observed exchange within the major isomer 3a without exchange with the minor isomer. This process is not observed for the minor isomer 3b because the hydride and the silyl group are mutually trans. Protonation to give [Os(3)(micro-H)(2)(SiR(3))(CO)(9)(micro-dppm)](+) totally suppresses the dynamic behaviour because there are no edge vacancies.     

Synthesis, molecular structure and properties of the [H6-nNi30C4(CO)34(CdCl)2]n- (n=3-6) bimetallic carbide carbonyl cluster: a model for the growth of noncompact interstitial metal carbides

Reaction of the [Ni(9)C(CO)(17)](2-) dianion with CdCl(2)2.5 H(2)O in THF affords the novel bimetallic Ni--Cd carbide carbonyl clusters [H(6-n)Ni(30)C(4)(CO)(34)(micro(5)-CdCl)(2)](n-) (n=3-6), which undergo several protonation-deprotonation equilibria in solution depending on the basicity of the solvent or upon addition of acids or bases. Although the occurrence in solution of these equilibria complicates the pertinent electrochemical studies on their electron-transfer activity, they clearly indicate that the clusters [H(6-n)Ni(30)C(4)(CO)(34)(micro(5)-CdCl)(2)](n-) (n=3-6), as well as the structurally related [H(6-n)Ni(34)C(4)(CO)(38)](n-) (n=4-6), undergo reversible or partially reversible redox processes and provide circumstantial and unambiguous evidence for the presence of hydrides for n=3, 4 and 5. Three of the [H(6-n)Ni(30)C(4)(CO)(34)(micro(5)-CdCl)(2)](n-) anions (n=4-6) have been structurally characterized in their [NMe(3)(CH(2)Ph)](4)[H(2)Ni(30)C(4)(CO)(34)(CdCl)(2)]2 COMe(2), [NEt(4)](5)[HNi(30)C(4)(CO)(34)(CdCl)(2)]2 MeCN and [NMe(4)](6)[Ni(30)C(4)(CO)(34)(CdCl)(2)]6 MeCN salts, respectively. All three anions display almost identical geometries and bonding parameters, probably because charge effects are minimized by delocalization over such a large metal carbonyl anion. Moreover, the Ni(30)C(4) core in these Ni-Cd carbide clusters is identical within experimental error to those present in the [HNi(34)C(4)(CO)(38)](5-) and [Ni(35)C(4)(CO)(39)](6-) species, suggesting that the stepwise assembly of their nickel carbide cores may represent a general pathway of growth of nickel polycarbide clusters. The fact that the [H(6-n)Ni(30)C(4)(CO)(34)(micro(5)-CdCl)(2)](n-)(n=4-6) anions display two valence electrons more than the structurally related [H(6-n)Ni(34)C(4)(CO)(38)](n-) (n=4-6) species has been rationalized by extended Hückel molecular orbital (EHMO) analysis.     

Reactions of the tetrahedral clusters [MCo(3)(CO)(12)](-) (M = Ru, Fe) with functional mono- and diynes

The tetrahedral cluster [RuCo(3)(CO)(12)](-) reacts with various alkynes, including the new PhCtbd1;CC(O)NHCH(2)Ctbd1;CH (L(1)()), to afford the butterfly clusters [RuCo(3)(CO)(10)(micro(4)-eta(2)-RC(2)R')](-) (1, R = R' = C(O)OMe; 2, R = H, R' = Ph; 3, R = H, R' = MeC=CH(2); 4, R = H, R' = CH(2)OCH(2)Ctbd1;CH; 5, R = H, R' = CH(2)NHC(O)Ctbd1;CPh), in which the ruthenium atom occupies a hinge position and the alkyne is coordinated in a micro(4)-eta(2) fashion. Reaction of the anions 1-3 with [Cu(NCMe)(4)]BF(4) led to selective loss of the 12e fragment Co(CO)(-) to form [RuCo(2)(CO)(9)(micro(3)-eta(2)-RC(2)R')] (6, R = R' = C(O)OMe; 7, R = H, R' = Ph; 8, R = H, R' = MeC=CH(2)). To prepare functionalized RuCo(3) or FeCo(3) clusters that could be subsequently condensed with a silica matrix via the sol-gel method, we reacted [MCo(3)(CO)(12)](-) (M = Ru, Fe) with the alkyne PhCtbd1;CC(O)NH(CH(2))(3)Si(OMe)(3)(L(2)()) and obtained the butterfly clusters [MCo(3)(CO)(10)(micro(4)-eta(2)-PhC(2)C(O)NH(CH(2))(3)Si(OMe)(3))](-) 9 and 10, respectively. Air-stable [RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))](-) (11) was obtained from 1,4-bis(trimethylsilyl)butadiyne and reacted with [Cu(NCMe)(4)]BF(4) to give [RuCo(2)(CO)(9)(micro(3)-eta(2)-HC(2)Ctbd1;CSiMe(3))] (12), owing to partial ligand proto-desilylation, and not the expected [RuCo(2)(CO)(9)(micro(3)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))]. Reaction of 11 with [NO]BF(4) afforded, in addition to 12, [RuCo(3)(CO)(9)(NO)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))] (13) owing to selective CO substitution on a wing-tip cobalt atom with NO. The thermal reaction of 11 with [AuCl(PPh(3))] led to replacement of a CO on Ru by the PPh(3) originating from [AuCl(PPh(3))] and afforded [RuCo(3)(CO)(9)(PPh(3))(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))](-) (14), also obtained directly by reaction of 11 with one equivalent of PPh(3). Proto-desilylation of 11 using TBAF/THF-H(2)O afforded [RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CH)](-) (15) which, by Sonogashira coupling with 1,4-diiodobenzene, yielded the dicluster complex [[RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;C)]](2)C(6)H(4)](2)(-) (16). The crystal structures of NEt(4).3a, NEt(4).4a, 6, NEt(4).11b, NEt(4).14, and [N(n-Bu)(4)].15a have been determined by X-ray diffraction. Preliminary results indicate the potential of silica-tethered alkyne mixed-metal clusters, obtained by the sol-gel method, as precursors to bimetallic particles.     

Preparation and characterization of [Hg[P(C6F5)2]2], [Hg[(mu-P(C6F5)2)W(CO)5]2], and [Hg[(mu-P(CF3)2)W(CO)5]2] and the X-ray crystal structure of [Hg[(mu-P(C6F5)2)W(CO)5]2].2DMF

The thermally unstable compound [Hg[P(C(6)F(5))(2)](2)] was obtained from the reaction of mercury cyanide and bis(pentafluorophenyl)phosphane in DMF solution and characterized by multinuclear NMR spectroscopy. The thermally stable trinuclear compounds [Hg[(mu-P(CF(3))(2))W(CO)(5)](2)] and [Hg[(mu-P(C(6)F(5))(2))W(CO)(5)](2)] are isolated and completely characterized. The higher order NMR spectra exhibiting multinuclear satellite systems have been sufficiently analyzed. [Hg[(mu-P(CF(3))(2))W(CO)(5)](2)].2DMF crystallizes in the monoclinic space group C2/c with a = 2366.2(3) pm, b = 1046.9(1) pm, c = 104.0(1) pm, and beta = 104.01(1) degrees. Structural, NMR spectroscopic, and vibrational data prove a weak coordination of the two DMF molecules. Structural, vibrational, and NMR spectroscopic evidence is given for a successive weakening of the pi back-bonding effect of the W-P bond in the order [W(CO)(5)PH(R(f))(2)], [Hg[(mu-P(R(f))(2))W(CO)(5)](2)], and [W[P(R(f))(2)](CO)(5)](-) with R(f) = C(6)F(5) and CF(3). The pi back-bonding effect of the W-C bonds increases vice versa.     

Carboranes as ligands for the preparation of organometallic Tc and Re Radiopharmaceuticals. Synthesis of [M(CO)(3)(eta-2,3-C(2)B(9)H(11))](-) and rac-[M(CO)(3)(eta-2-R-2,3-C(2)B(9)H(10))](-) (M = Re, (99)Tc; R = CH(2)CH(2)CO(2)H) from [M(CO)(3)Br(3)](2-)

A new and high yielding method for the synthesis of [M(CO)(3)(eta(5)-2,3-C(2)B(9)H(11))](-) and the bifunctional metal complexes, rac-[M(CO)(3)(eta(5)-2-R-2,3-C(2)B(9)H(10))](-) (R = CH(2)CH(2)CO(2)H), from [M(CO)(3)Br(3)](2)(-) (M = Re, (99)Tc) was developed. The general approach entailed the addition of nido-[(C(2)B(9)H(12))(-)], or the acid substituted analogue, to [M(CO)(3)Br(3)](2)(-) (M = Re, (99)Tc) in the presence of TlOEt in THF. It was also possible to prepare the reported products in water using sodium carbonate in place of TlOEt. The reported approach led to the preparation, and X-ray crystallographic structure determination, of the first Tc-carborane complex reported to date (a = 13.606(17) A, b = 10.685(13) A, c = 15.534(16) A, alpha = gamma = 90 degrees, beta = 111.84(2) degrees). Because of the stabilities of the metal complexes, and the fact that the compounds can be prepared in water, the bifunctional derivatives can be considered as novel synthons for the preparation of organometallic (99m)Tc and (186/188)Re radiopharmaceuticals.     

The inter-conversions of platinum carbonyl dianionic clusters, [Pt3(CO)6](n)2- (n = 2-5), in THF and acetonitrile. A combined in situ FTIR spectroscopic and BTEM study leading to the characterization of the new [H(4-x)Pt15(CO)19]x- (x = 2-4) clusters

The inter-conversions of platinum carbonyl dianionic clusters, ([Pt(3)(CO)(6)](n)(2-), n = 2-5), have been studied in THF and acetonitrile using in situ FTIR spectroscopy. These inter-conversions were facilitated by the addition (or removal) of molecular hydrogen. The individual reactions, namely reductions and oxidations of [Pt(3)(CO)(6)](n)(2-) were fast and reversible. BTEM analysis of the data provided the pure component spectra of the individual species without the need for physical separation. It is shown, for the first time, that the species [Pt(3)(CO)(6)](n)(2-) (n = 2) can be formed from the reduction of [Pt(3)(CO)(6)](n)(2-) (n = 3-5) by hydrogen alone in acetonitrile. Also, detection of dissolved CO(2) in solution suggests that a room-temperature water gas shift reaction occurs. This has been shown to arise from nucleophilic attack of water on a coordinated CO of [Pt(3)(CO)(6)](n)(2-) which leads to the formation of [HPt(15)(CO)(19)](3-) and [H(2)Pt(15)(CO)(19)](2-). The parent tetraanion, [Pt(15)(CO)(19)](4-), has been isolated in high yields by reaction of [Pt(3)(CO)(6)](n)(2-) (n = 2, 3) with NaOH at 60 °C and has been structurally characterized by X-ray analysis.     

Superelectrophilic tetrakis(carbonyl)palladium(II)- and -platinum(II) undecafluorodiantimonate(V), [Pd(CO)4][Sb(2)F(11)]2 and [Pt(CO)4][Sb(2)F(11)]2: syntheses, physical and spectroscopic properties, their crystal, molecular, and extended structures, and density functional calculations: an experimental, computational, and comparative study .

The salts [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, are prepared by reductive carbonylation of Pd[Pd(SO(3)F)(6)], Pt(SO(3)F)(4) or PtF(6) in liquid SbF(5), or HF-SbF(5). The resulting moisture-sensitive, colorless solids are thermally stable up to 140 degrees C (M = Pd) or 200 degrees C (M = Pt). Their thermal decompositions are studied by differential scanning calorimetry (DSC). Single crystals of both salts are suitable for an X-ray diffraction study at 180 K. Both isostructural salts crystallize in the monoclinic space group P2(1)/c (No. 14). The unit cell volume of [Pt(CO)(4)][Sb(2)F(11)](2) is smaller than that of [Pd(CO)(4)][Sb(2)F(11)](2) by about 0.4%. The cations [M(CO)(4)](2+), M = Pd, Pt, are square planar with only very slight angular and out-of-plane deviations from D(4)(h)() symmetry. The interatomic distances and bond angles for both cations are essentially identical. The [Sb(2)F(11)](-) anions in [M(CO)(4)][Sb(2)F(11)](2,) M = Pd, Pt, are not symmetry-related, and both pairs differ in their Sb-F-Sb bridge angles and their dihedral angles. There are in each salt four to five secondary interionic C- -F contacts per CO group. Of these, two contacts per CO group are significantly shorter than the sum of the van der Waals radii by 0.58 - 0.37 A. In addition, structural, and spectroscopic details of recently synthesized [Rh(CO)(4)][Al(2)Cl(7)] are reported. The cations [Rh(CO)(4)](+) and [M(CO)(4)](2+), M = Pd, Pt, are characterized by IR and Raman spectroscopy. Of the 16 vibrational modes (13 observable, 3 inactive) 10 (Pd, Pt) or 9 (Rh), respectively, are found experimentally. The vibrational assignments are supported by DFT calculations, which provide in addition to band positions also intensities of IR bands and Raman signals as well as internal force constants for the cations. (13)C NMR measurements complete the characterization of the square planar metal carbonyl cations. The extensive characterization of [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, reported here, allows a comparison to linear and octahedral [M(CO)(n)()][Sb(2)F(11)](2) salts [M = Hg (n = 2); Fe, Ru, Os (n = 6)] and their derivatives, which permit a deeper understanding of M-CO bonding in the solid state for superelectrophilic cations with [Sb(2)F(11)](-) or [SbF(6)](-) as anions.     

Synthesis, structure, and spectroscopic characterization of [H(8-n)Rh22(CO)35](n-) (n = 4, 5) and [H2Rh13(CO)24{Cu(MeCN)}2](-) clusters: assessment of CV and DPV as techniques to circumstantiate the presence of elusive hydride atoms

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.     

Hydroxoundecahydro-closo-dodecaborate(2-) as a Nucleophile. Preparation and Structural Characterization of O-Alkyl and O-Acyl Derivatives of Hydroxoundecahydro-closo-dodecaborate(2-)

The syntheses, solid state structures, and spectral properties of O-alkyl and O-acyl derivatives of hydroxoundecahydro-closo-dodecaborate(2-), 1, are described. Alkylation of 1 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as a base, leading to [N(n-C(4)H(9))(4)](2)[CH(3)CH(2)O-B(12)H(11)(2-)], 2, bis(tetrabutylammonium) ethoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1192.4(9) pm, b = 1253.9(4) pm, c = 3049.1(10) pm, beta = 92.69(4) degrees, Z = 4, R1 = 0.0693, wR(2) = 0.1517]. Alkylation with 1,5-dibromopentane afforded the cyclic oxonium salt [PPN][C(5)H(10)O-B(12)H(11)(1-)], 3, (&mgr;-nitrido)bis(triphenylphosphorus)(1+) tetrahydropyrane-undecahydro-closo-dodecaborate(1-) [monoclinic P2(1)/c, a = 1938.1(2) pm, b = 1329.7(10) pm, c = 1944.0(2) pm, beta = 108.82(10) degrees, Z = 4, R1 = 0.0484, wR(2) = 0.0833]. Acylation of 1 in acetonitrile with acyl chlorides in the presence of pyridine yielded [N(n-C(4)H(9))(4)](2)[C(6)H(5)CO(2)-B(12)H(11)(2-)], 4, bis(tetrabutylammonium) undecahydrobenzoyl-closo-dodecaborate(2-) [monoclinic P2(1)/c, a = 1812.0(4) pm, b = 1711.9(3) pm, c = 1685.0(3) pm, beta = 114.03(3) degrees, Z = 4, R1 = 0.0915, wR(2) = 0.2093], and [N(n-C(4)H(9))(4)](2)[CH(3)CO(2)-B(12)H(11)(2-)], 5, bis(tetrabutylammonium) acetoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1190.5(2) pm, b = 1243.0(10) pm, c = 3078.4(4) pm, beta = 92.76(10) degrees, Z = 4, R1 = 0.0642, wR(2) = 0.1462]. All crystal structures showed distortion of the pseudoicosahedral geometry of the boron cluster. The boron-oxygen distances varied from 144.2(5) pm for 2, 148.5(3) pm for 5, 149.4(12) pm for 4, to 152.8(4) pm for 3. The 3-fold coordinated oxygen of oxonium salt 3 is nearly planar.     

Isolation of (CO)1- and (CO2)1- radical complexes of rare earths via Ln(NR2)3/K reduction and [K2(18-crown-6)2]2+ oligomerization

Deep-blue solutions of Y(2+) formed from Y(NR(2))(3) (R = SiMe(3)) and excess potassium in the presence of 18-crown-6 at -45 °C under vacuum in diethyl ether react with CO at -78 °C to form colorless crystals of the (CO)(1-) radical complex, {[(R(2)N)(3)Y(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 1. The polymeric structure contains trigonal bipyramidal [(R(2)N)(3)Y(μ-CO)(2)](2-) units with axial (CO)(1-) ligands linked by [K(2)(18-crown-6)(2)](2+) dications. Byproducts such as the ynediolate, [(R(2)N)(3)Y](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 2, in which two (CO)(1-) anions are coupled to form (OC≡CO)(2-), and the insertion/rearrangement product, {(R(2)N)(2)Y[OC(═CH(2))Si(Me(2))NSiMe(3)]}[K(18-crown-6)], 3, are common in these reactions that give variable results depending on the specific reaction conditions. The CO reduction in the presence of THF forms a solvated variant of 2, the ynediolate [(R(2)N)(3)Y](2)(μ-OC≡CO)[K(18-crown-6)(THF)(2)](2), 2a. CO(2) reacts analogously with Y(2+) to form the (CO(2))(1-) radical complex, {[(R(2)N)(3)Y(μ-CO(2))(2)][K(2)(18-crown-6)(2)]}(n), 4, that has a structure similar to that of 1. Analogous (CO)(1-) and (OC≡CO)(2-) complexes of lutetium were isolated using Lu(NR(2))(3)/K/18-crown-6: {[(R(2)N)(3)Lu(μ-CO)(2)][K(2)(18-crown-6)(2)]}(n), 5, [(R(2)N)(3)Lu](2)(μ-OC≡CO){[K(18-crown-6)](2)(18-crown-6)}, 6, and [(R(2)N)(3)Lu](2)(μ-OC≡CO)[K(18-crown-6)(Et(2)O)(2)](2), 6a.     

Direct Lanthanide-Transition Metal Interactions: Synthesis of (NH(3))(2)YbFe(CO)(4) and Crystal Structures of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity)

The heterometallic complex (NH(3))(2)YbFe(CO)(4) was prepared from the reduction of Fe(3)(CO)(12) by Yb in liquid ammonia. Ammonia was displaced from (NH(3))(2)YbFe(CO)(4) by acetonitrile in acetonitrile solution, and the crystalline compounds {[(CH(3)CN)(3)YbFe(CO)(4))](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity) were obtained. An earlier X-ray study of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH(3)CN)(3)YbFe(CO)(4)](infinity) is a sheetlike array with direct Yb-Fe bonds. Crystal data for {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity): monoclinic space group P2(1)/c, a = 21.515(8) ?, b = 7.838(2) ?, c = 19.866(6) ?, beta = 105.47(2) degrees, Z = 4. Crystal data for [(CH(3)CN)(3)YbFe(CO)(4)](infinity): monoclinic space group P2(1)/n, a = 8.364(3) ?, b = 9.605(5) ?, c = 17.240(6) ?, beta = 92.22(3) degrees, Z = 4. Electrical conductivity measurements in acetonitrile show that these acetonitrile complexes are partially dissociated into ionic species. IR and NMR spectra of the solutions reveal the presence of [HFe(CO)(4)](-). However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO)(4)](-) on the basis of their IR spectra. The solid state MAS (2)H NMR spectra of deuterated acetonitrile complexes give no evidence for [(2)HFe(CO)(4)](-). It appears that rupture of the Yb-Fe bond could occur in solution to generate the ion pair [L(n)Yb](2+)[Fe(CO)(4)](2-), but then the highly basic [Fe(CO)(4)](2-) anion could abstract a proton from a coordinated acetonitrile ligand to form [HFe(CO)(4)](-). However, upon crystallization, the proton could be transferred back to the ligand, which results in the neutral polymeric species.     

Synthesis, Structure, and Reactivities of [eta(2)-P(7)M(CO)(4)](3)(-), [eta(2)-HP(7)M(CO)(4)](2)(-), and [eta(2)-RP(7)M(CO)(4)](2)(-) Zintl Ion Complexes Where M = Mo, W

Ethylenediamine (en) solutions of [eta(4)-P(7)M(CO)(3)](3)(-) ions [M = W (1a), Mo (1b)] react under one atmosphere of CO to form microcrystalline yellow powders of [eta(2)-P(7)M(CO)(4)](3)(-) complexes [M = W (4a), Mo (4b)]. Compounds 4 are unstable, losing CO to re-form 1, but are highly nucleophilic and basic. They are protonated with methanol in en solvent giving [eta(2)-HP(7)M(CO)(4)](2)(-) ions (5) and are alkylated with R(4)N(+) salts in en solutions to give [eta(2)-RP(7)M(CO)(4)](2)(-) complexes (6) in good yields (R = alkyl). Compounds 5 and 6 can also be prepared by carbonylations of the [eta(4)-HP(7)M(CO)(3)](2)(-) (3) and [eta(4)-RP(7)M(CO)(3)](2)(-) (2) precursors, respectively. The carbonylations of 1-3 to form 4-6 require a change from eta(4)- to eta(2)-coordination of the P(7) cages in order to maintain 18-electron configurations at the metal centers. Comparative protonation/deprotonation studies show 4 to be more basic than 1. The compounds were characterized by IR and (1)H, (13)C, and (31)P NMR spectroscopic studies and microanalysis where appropriate. The [K(2,2,2-crypt)](+) salts of 5 were characterized by single crystal X-ray diffraction. For 5, the M-P bonds are very long (2.71(1) ?, average). The P(7)(3)(-) cages of 5 are not displaced by dppe. The P(7) cages in 4-6 have nortricyclane-like structures in contrast to the norbornadiene-type geometries observed for 1-3. (31)P NMR spectroscopic studies for 5-6 show C(1) symmetry in solution (seven inequivalent phosphorus nuclei), consistent with the structural studies for 5, and C(s)() symmetry for 4 (five phosphorus nuclei in a 2:2:1:1:1 ratio). Crystallographic data for [K(2,2,2-crypt)](2)[eta(2)-HP(7)W(CO)(4)].en: monoclinic, space group C2/c, a = 23.067(20) ?, b = 12.6931(13) ?, c = 21.433(2) ?, beta = 90.758(7) degrees, V = 6274.9(10) ?(3), Z = 4, R(F) = 0.0573, R(w)(F(2)) = 0.1409. For [K(2,2,2-crypt)](2)[eta(2)-HP(7)Mo(CO)(4)].en: monoclinic, space group C2/c, a = 22.848(2) ?, b = 12.528(2) ?, c = 21.460(2) ?, beta = 91.412(12) degrees, V = 6140.9(12) ?(3), Z = 4, R(F) = 0.0681, R(w)(F(2)) = 0.1399.