X-ray diffraction structure of the phosphido-bridged mixed-metal cluster Fe2(CO)6(μ3-PPh)2Pt(dppe)

Treatment of Fe₂(CO)₆(₂-PPhH)₂ with BuLi (2 equiv.), followed by the addition of PtCl₂ (dppe), affords the phosphido-bridged cluster Fe₂(CO)₆(₃-PPh)₂Pt(dppe). The Fe₂Pt cluster was isolated and characterized in solution by IR and ³¹P NMR spectroscopy, and the molecular structure of Fe₂(CO)₆(₃-PPh)₂Pt(dppe) determined by X-ray diffraction analysis. Fe₂(CO)₆(₃-PPh)₂Pt(dppe) crystallizes in the orthorhombic space group P_bca, a = 17.539(3) Å, b = 21.490(2) Å, c = 22.959(3) Å, V = 8653.5(18) ų, Z = 8, d_calc = 1.670 g cm^–3; R = 0.0644, R_w = 0.0389 for 5040 observed reflections with I > 3(I).     

X-ray structure and redox chemistry of the heptacobalt cluster Co3(CO)9[μ3-CCO2CH2CCH{Co4(CO)10}]

The tetrahedrane cluster reacts with Co₄(CO)₁₂ to furnish the heptacobalt compound Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₄(CO)₁₀}] in high yield. Substitution of the pendant alkyne group by the Co₄(CO)₁₀ moiety was ascertained by IR and ¹H NMR spectroscopies, and the solid-state structure of Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₄(CO)₁₀}] was unequivocally determined by X-ray crystallography. Co₃(CO)₉[₃-CCO₃CH₃CCH{Co₄(CO)₁₀}] crystallizes in the monoclinic space group P2 ₁/n, a = 12.895(13) Å, b = 18.803(18) Å, c = 13.748(13) Å, = 97.27(2)°, V = 3307(6) ų, Z = 4, d _calc = 2.087 mg/m³; R = 0.0493, R _w = 0.0989 for 4310 observed reflections with I > 2(I). The X-ray structure confirms the presence of an intact tetrahedral Co₃ moiety and an alkyne-tethered Co₄ butterfly cluster moiety. The cyclic voltammetric properties of Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₄(CO)₁₀}] were examined and three reduction waves were found. The first two reduction waves correspond to the regionally localized 0/1^– redox couples on the tetra- and tricobalt moieties, respectively, while the third redox process is assigned to the 1^–/2^– reduction associated with the tetracobalt residue. Both 0/1^– redox couples are reversible, while the 1^–/2^– reduction exhibits only quasi-reversible behavior. No evidence for electronic communication between the Co₃ and Co₄ portions of the complex was observed. Extended Hückel MO calculations support the site of the first reduction occurring solely on the tetracobalt moiety of this Co₇ cluster.     

X-ray diffraction structure of Co2(CO)4(μ-PhC≡CH)[(Z)-Ph2PCH=CHPPh2[: proof for diphosphine ligand chelation

Treatment of the dicobalt compound Co₂(CO)₆(-PhCCH) (1) with the unsaturated diphosphine ligand (Z)-Ph₂PCH=CHPPh₂ gives the chelating diphosphine compound Co₂(CO)₄(-PhCCH)[(Z)-Ph₂PCH=CHPPh₂] (2) when the reaction is carried in refluxing 1,2-dichloroethane or in the presence of Me₃NO. 2 was characterized in solution by IR and ³¹P NMR spectroscopy, and the molecular structure of Co₂(CO)₄(-PhCCH)[(Z)-Ph₂PCH=CHPPh₂] was established by X-ray diffraction analysis, which confirmed the chelation of the P-ligand to a single cobalt center. Co₂(CO)₄(-PhCCH)[(Z)-Ph₂PCH=CHPPh₂] crystallizes in the monoclinic space group P2₁/c, a = 10.151(1), b = 32.694(5), c = 11.051(5) Å, = 111.14(1)°, V = 3420.7(9) ų, Z = 4, and d _calc = 1.414. The two distinct ³¹P resonances found in the ³¹P NMR spectrum of 2 are discussed relative to the X-ray structure and other structurally similar cobalt–alkyne complexes. Thermolysis of Co₂(CO)₄(-PhCCH)[(Z)-Ph₂PCH=CHPPh₂] led only to the slow decomposition of Co₂(CO)₄(-PhCCH)[(Z)-Ph₂PCH=CHPPh₂] and not to the formation of the isomeric bridged-diphosphine complex.     

Synthesis of a mixed cluster/binuclear compound. Electrochemical properties and X-ray diffraction structure of Co3(CO)9[μ3-CCO2CH2CCH{Co2(CO)6}]

The tetrahedrane cluster Co₃(Co)₉(₃-CCO₂CH₂CCH) reacts with Co₂(CO)₆ to furnish the pentacobalt compound Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}] in high yield. Functionalization of the pendant alkyne group by Co₂(CO)₆ was ascertained by IR and NMR spectroscopies (¹H and ¹³C), and the solid-state structure of Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}] was unequivocally established by X-ray diffraction analysis. Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}] crystallizes in the triclinic space group , a = 7.9674(5), b = 13.208(1), c = 13.3094(9) Å, = 76.257(6), = 79.123(6), = 86.403(6)°, V = 1335.8(2) ų, Z = 2, and d _calc = 2.016 g/cm³. The electrochemical properties of Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}] were examined by cyclic voltammetry and the first reduction wave was found to be a reversible, one-electron reduction associated with the tricobalt moiety. No evidence for electronic communication between the Co₃ and Co₂ portions of the complex was observed. The results of extended Hückel MO calculations on Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}] establish the nature of the LUMO in Co₃(CO)₉[₃-CCO₂CH₂CCH{Co₂(CO)₆}].     

Diphosphine ligand substitution in H4Ru4(CO)12: X-ray diffraction structures and reactivity studies of the cluster compounds H4Ru4(CO)10(P–P) [where P–P–(Z)–Ph2PCH–CHPPh2, bpcd]

The tetraruthenium cluster H₄Ru₄(CO)₁₂ (1) has been studied for its reactivity with the unsaturated diphosphine ligands (Z)–Ph₂PCH–CHPPh₂ and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) under thermal, near-UV photolysis, and Me₃NO-assisted activation. All three cluster activation methods promote loss of CO and furnish the anticipated substitution products H₄Ru₄(CO)₁₀[(Z)–Ph₂PCH–CHPPh₂] (2) and H₄Ru₄(CO)₁₀(bpcd) (3) that possess a chelating diphosphine ligand. Clusters 2 and 3 have been characterized in solution by IR and NMR spectroscopies, and these data are discussed with respect to the crystallographically determined structure for both new cluster compounds. The ³¹P NMR spectral data and the solid-state structures confirm the presence of a chelating diphosphine ligand in clusters 2 and 3. Cluster 2 crystallizes in the monoclinic space P2₁/c, a=11.768(6) ?, b=18.521(9) ?, c=20.48(1) ?, β=102.291(8)°, V=4361(4) A³, Z=4, and d _calc=1.726 Mg/m³; R=0.0225, R _w=0.0491 for 6798 reflections with I > 2σ(I). The four bridging hydrides were located in H₄Ru₄(CO)₁₀[(Z)–Ph₂PCH–CHPPh₂] and their adopted positions are discussed relative to the solution ¹H NMR spectrum. H₄Ru₄(CO)₁₀(bpcd) crystallizes in the orthorhombic space Pbca, a=19.072(3) ?, b=20.169(3) ?, c=22.774(3) ?, V=8760(2) A³, Z=8, and d _calc=1.870 Mg/m³; R=0.0428, R _w=0.0896 for 10296 reflections with I > 2σ(I). Sealed NMR tubes containing clusters 2 and 3 were found to be exceeding stable towards near-UV light and temperatures up to ca. 125 °C. The surprisingly robust behavior of 2 and 3 is contrasted with the related cluster Ru₃(CO)₁₀(bpcd) that undergoes fragmentation to the donor-acceptor compound Ru₂(CO)₆(bpcd) and the phosphido-bridged compound Ru₂(CO)₆(μ–PPh₂)[μ–C–C(PPh₂)C(O)CH₂C(O)] under mild conditions. The electrochemical properties of each substituted cluster have been investigated by cyclic voltammetry, and our findings are discussed with respect to the reported electrochemical data on the parent cluster H₄Ru₄(CO)₁₂.

Construction of a hexanuclear cluster composed of spatially separated Co3 and Ru3 units: X-ray diffraction structure of Co3(CO)9[μ3-CCO2CH2CC{HRu3(CO)9}]

Treatment of the tricobalt cluster with the activated triruthenium cluster Ru₃(CO)₁₀(MeCN)₂ affords the acetylide-bridged hexanuclear cluster Co₃(CO)₉[₃–CCO₂CH₂CC{HRu₃(CO)₉}] in moderate yield. The new cluster was characterized in solution by IR spectroscopy and molecular structure was established by X-ray diffraction analysis. Co₃(CO)₉[₃–CCO₂CH₂CC{HRu₃(CO)₉}] crystallizes in the triclinic space group P(–1), a = 8.728(1) Å, b = 12.916(2) Å, c = 14.663(2) Å, = 82.950(2)°, = 82.465(2)°, = 86.199(2)°, V = 1624.2(4) ų, Z = 2, d _calc = 2.207 mg/m³; R = 0.0263, R _w = 0.0623 for 3596 observed reflections with I > 2(I). The coordination of the triruthenium cluster to the acetylene ligand of Co₃(CO)₉(₃–CCO₂CH₂CCH) is confirmed, and the structural details associated with the acetylide-bridged triruthenium frame are contrasted with other structurally characterized Ru₃ clusters bound by a 5e-acetylide ligand.     

X-ray structure of [Os3(CO)10(μ-Ph2PCH2PPh2)]

Decacarbonyl--bis(diphenylphosphino)methane triosmium crystallizes in the monoclinic space group P2₁/c with a = 24.422(5), b = 12.381(2), c = 24.788(5) Å, = 103.69(3)°, V = 7282 (2) ų, and Z = 8. The molecule consists of a triangular arrangement of osmium atoms with the organic ligand bridging two adjacent osmium atoms at equatorial sites. The Os—Os distances lie in the close range 2.8563(9)–2.8895(11) Å with an average value of 2.87(1) Å.     

Crystal structure of trans-W2(CO)6(PPh2H)2(μ2-PPh2)2

The molecular structure of trans-W²(CO)₆(PPh²H)²(₂-PPh²)² was determined by X-ray diffraction analysis. The two tungsten centers, bridged by two diphenylphosphido ligands, are separated by 3.0667(6) Å with W–P–W angles of 77.10(5) and 77.08(5). Average tungsten–phosphorus bond distances are 2.461(17) and 2.4576(21) Å for bridging and terminal phosphorus groups, respectively, with a range of 0.037 Å for the former and 0.001 Å for the latter. The complex crystallizes in the monoclinic space group P2₁/c with a = 19.282(4) Å, b = 12.158(2) Å, c = 21.294(9) Å, = 92.821(4), and Z = 4.     

Reaction of the dicobalt alkyne compound Co2(CO)6(μ-dmad) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Spectroscopic properties, X-ray diffraction data, and thermal reactivity of the chelating isomer of Co2(CO)4(bpcd)(μ-dmad)

Treatment of Co₂(CO)₆(-dmad) (where dmad = dimethyl acetylenedicarboxylate) with the bidentate ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in the presence of added Me₃NO affords the new alkyne compound Co₂(CO)₄(bpcd)(-dmad) in good yield. Both IR and ³¹P NMR spectroscopies indicate that the bpcd ligand is coordinated to a single cobalt center in a chelating fashion in solution. The solid-state structure of Co₂(CO)₄(bpcd)(-dmad) is identical to the solution structure Co₂(CO)₄(bpcd)(-dmad), as determined by X-ray diffraction analysis. Co₂(CO)₄(bpcd)(-dmad) crystallizes in the triclinic space group P-1, a = 10.7460(8) Å, b = 11.628(2) Å, c = 15.077(1) Å, = 95.831(9)°, = 91.205(7)°, = 101.526(9)°, V = 1834.7(3) ų, Z = 2, and d _calc = 1.514 g/cm³; R = 0.0489, R _w = 0.0528 for 2854 reflections with I > 3(I). The thermal reactivity of Co₂(CO)₄(bpcd)(-dmad) has been briefly explored by spectroscopic methods, and evidence is presented for the attack of one of the PPh₂ groups on an alkyne carbon atom in Co₂(CO)₄(bpcd)(-dmad) to from the zwitterionic hydrocarbyl compound Co₂(CO)₄(-²:²:¹:¹-(MeO₂C)=C(CO₂Me)PPh₂C=C(PPh₂)C(O)CH₂C(O)] upon thermolysis. The redox chemistry of both Co₂(CO)₄(bpcd)(-dmad) and Co₂(CO)₄[-²:²:¹:¹-(MeO₂C) C=C(CO₂Me)PPh₂C=C(PPh₂)C(O)CH₂C(O)] has been explored by cyclic voltammetery.     

Alkyne insertion and coupling reactions of methyl propiolate with the heterometallic dimers CoRu(CO)7(μ-PPh2) and CoRu(CO)5[(Z)-Ph2PCH = CHPPh2](μ-PPh2): X-ray diffraction structures of CoRu(CO)4(μ-CO)[μ-PPh2C(O)CH(CCO2Me)C(O)CHC (CO2Me)] and CoRu(CO)3(μ-CO)[(Z)-Ph2PCH = CHPPh2][μ-PPh2C(O)C(CO2Me)CH]

The reaction of the terminal alkyne methyl propiolate with the heterometallic dimers CoRu(CO)₇(μ-PPh₂) (1) and CoRu(CO)₅[(Z)-Ph₂PCH=CHPPh₂](μ-PPh₂) (2) has been investigated at 65^°C in toluene. In the reaction of 1, chromatographic purification afforded a minor band, from which the two species RuCo(CO)₄(μ-CO)[μ-PPh₂C(O)CHC(CO₂Me)] and RuCo(CO)₄(μ-CO)[μ-PPh₂CHC(CO₂Me)] were observed by ¹H NMR spectroscopy, and one major band, whose ¹H NMR spectrum revealed the presence of multiple species. The identity of one of the compounds in the major component has been established as that of CoRu(CO)₄(μ-CO)[μ-PPh₂C(O)CH(CCO₂Me)C(O)CHC(CO₂Me)] (3) by X-ray diffraction analysis. The solid-state structure of 3 confirms the double insertion of CO and head-to-head coupling of the methyl propiolate that accompanies the formation of this product. Compound 3 crystallizes in the triclinic space group P-1, a = 8.4035(4), b = 9.6721(5), c = 17.678(1) Å, α = 94.135(2), β = 103.318(2), γ = 101.336(2)^°, V = 1360.5(1) ų, Z = 2, D _calc = 1.732 Mg/m³; R = 0.0300, R _w = 0.0760 for 8630 reflections with I > 2σ(I). The ruthenium-bound diphosphine ligand in 2 exerts a controlling influence on the reaction with added alkyne insomuch as only the mono-insertion product CoRu(CO)₃(μ-CO)[(Z)-Ph₂PCH=CHPPh₂][μ-PPh₂C(O)C(CO₂Me)CH] (4) is formed as a single regioisomer. The molecular structure of 4 was established by X-ray diffraction analysis and 4 was found to crystallize in the monoclinic space group P2₁/c, a = 19.483(7), b = 11.905(4), c = 20.131(7) Å, β = 110.455(6)^°, V = 4375(3) ų, Z = 4, D _calc = 1.466 Mg/m³; R = 0.0961, R _w = 0.1683 for 6262 reflections with I > 2σ(I). The reactivity of methyl propiolate with 1 and 2 is compared with the known reactivity that has been reported for other alkynes.     

Synthesis, redox chemistry, and X-ray structure of the mixed-metal cluster Fe2(CO)6(μ3-S)2Ni(dppf)

The reaction between the dianion [Fe₂(CO)₆(₂-S)₂]^2– and NiCl₂(dppf) occurs readily at room temperature to give the mixed-metal cluster Fe₂(CO)₆(₃-S)₂Ni(dppf) in moderate yield. Fe₂(CO)₆(₃-S)₂Ni(dppf) was isolated by preparative chromatography and its solid-state structure established by X-ray diffraction analysis. Fe₂(CO)₆(₃-S)₂Ni(dppf) crystallizes in the monoclinic space group C2/c, a = 20.320(6), b = 13.114(2), c = 15.622(2) Å, = 110.25(2)°, V = 3905.4(11) ų, Z = 4, and d _calc = 1.630 g/cm.³ The X-ray structure of Fe₂(CO)₆(₃-S)₂Ni(dppf) exhibits an Fe₂S₂Ni arachno polyhedral core, with the pendant dppf ligand attached to an essentially square planar Ni center. The redox chemistry of Fe₂(CO)₆(₃-S)₂Ni(dppf) was investigated by cyclic voltammetry which showed a reversible, one-electron oxidation localized on the Fe₂S₂ core along with an irreversible, one-electron reduction that is antibonding with respect to the Fe—Fe and Fe—S bonds. The electrochemical assignments were confirmed by carrying out extended Hückel MO calculations on the model cluster Fe₂(CO)₆(₃-S)₂Ni(H₄-dppf).     

Chelation of a diphosphine ligand at FeCo2(CO)9(μ3-S): Spectroscopic and X-ray diffraction data for FeCo2(CO)7(bpcd)(μ3-S)

The tetrahedrane cluster, FeCo₂(CO)₉(₃-S), reacts with the redox-active ligand, 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd), to give the disubstituted cluster, FeCo₂(CO)₇(bpcd)(₃-S), as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. Both IR and ³¹P NMR spectroscopies have been employed in the solution characterization of FeCo₂(CO)₇(bpcd)(₃-S), and the solid-state structure has been unequivocally established by X-ray diffraction analysis. FeCo₂(CO)₇(bpcd)(₃-S) crystallizes in the monoclinic space group C2/c, a = 34.494(3) Å, b = 11.4194(9) Å, c = 18.634(2) Å, = 98.103(7)°, V = 7266.7(9) ų, Z = 8, and d_calc = 1.584 g/cm³. Cyclic voltammetric studies on FeCo₂(CO)₇(bpcd)(₃-S) reveal the presence of two quasireversible redox responses assigned to the 0/1^– and 1^–/2^– redox couples. The orbital composition of these redox couples has been examined by carrying out extended Hückel MO calculations on the model complex FeCo₂(CO)₇(H₄-bpcd)(₃-S), with the results being compared to related cluster compounds.     

Site-selective ligand substitution in CoRu(CO)7(μ-PPh2) using (Z)-Ph2PCH=CHPPh2 and reactivity of DMAD with CoRu(CO)5[(Z)-Ph2PCH=CHPPh2](μ-PPh2). X-ray structures of CoRu(CO)5[(Z)-Ph2PCH=CHPPh2](μ-PPh2) and CoRu(CO)3(μ-CO)[(Z)-Ph2PCH=CHPPh2] [μ, η3-Ph2PC(CO2Me)C(CO2Me)]

The heterometallic complex CoRu(CO)₇(μ-PPh₂) (1) reacts with the diphosphine ligand (Z)-Ph₂PCH=CHPPh₂ under both thermolysis and Me₃NO activation to furnish CoRu(CO)₅[(Z)-Ph₂PCH=CHPPh₂](μ-PPh₂) (2) in good yield. Treatment of 2 with dimethyl acetylenedicarboxylate (DMAD) at elevated temperature leads to the formal insertion of the DMAD ligand into the Co–phosphido bond and formation of the metallocyclic compound CoRu(CO)₃(μ-CO)[(Z)-Ph₂PCH=CHPPh₂][μ,η³-Ph₂PC(CO₂Me)C(CO₂Me)] (3) that contains a 5e^? alkenylphosphine moiety. These new CoRu compounds have been isolated by chromatography and fully characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies, and the solid-state structures of both 2 and 3 have been determined by X-ray diffraction analysis. CoRu(CO)₅[(Z)-Ph₂PCH=CHPPh₂](μ-PPh₂) crystallizes in the monoclinic space group P2 ₁/n, a = 11.493(8), b = 20.24(1), c = 17.04(1) Å, β = 91.03(1)°, V = 3964(5) ų, Z = 4, D _calc = 1.477 Mg/m³; R = 0.0475, R _w = 0.1054 for 5120 observed reflections with I > 2σ (I). CoRu(CO)₃(μ-CO)(Z)-Ph₂PCH=CHPPh₂][μ,η³-Ph₂PC(CO₂Me)C(CO₂Me)], as the CH₂Cl₂ solvate, crystallizes in monoclinic space group P2 ₁/c, a = 17.0307(9) Å, b = 11.2124(6) Å, c = 24.083(1) Å, β = 97.755(1)°, V = 4556.8(4) ų, Z = 4, D _calc = 1.579 Mg/m³; R = 0.0379, R _w = 0.0609 for 10774 observed reflections with I > 2σ(I). The regioselective coordination of the (Z)-Ph₂PCH=CHPPh₂ ligand to the two equatorial sites of the ruthenium center in 2 and the presence of the metallocyclic alkenylphosphine ligand in 3 are confirmed by the structural studies. The regiochemistry found in the coordination of (Z)-Ph₂PCH=CHPPh₂ to 1 is contrasted with the related diphosphine ligands bma and bpcd, while the DMAD insertion reactivity with 2 is discussed relative to alkyne reactions reported for the parent compound CoRu(CO)₇(μ-PPh₂).     

X-ray diffraction analysis on the structure of the glasses in the system PbOSiO2

The structures of PbO·SiO₂ and 2PbO·SiO₂ glasses have been analyzed by use of X-ray diffraction data and pair function method. For PbO·SiO₂ glass, a model consisting of chains of PbO₃ pyramids and silicate chains showed good agreement with the observed RDF. For 2PbO·SiO₂ glass, the present authors reported previously a model in which chains of PbO₃ pyramids are connected with SiO₄ tetrahedra, while the chromatographic analyses of silicate anions by Götz et al. and Smart et al. showed that silicate anions are distributed from monomer to polymer in the glass. We reexamined the structure of this glass referring to these results. Three representative models containing isolated SiO₄, Si₄O₁₂ rings and (SiO₃)_n chains respectively as well as PbO₃ chains were constructed and the RDFs were calculated with changing structure parameters. These three models showed satisfactory agreement with the observed data, showing that silicate anions are distributed from monomer to polymer in 2PbO·SiO₂ glass and an increase of SiO₂ content leads to polymerization of silicate anions to longer chains up to PbO·SiO₂ composition, while the chains of PbO₃ pyramids remain unchanged.     

Reaction of ethyl diazoacetate with Co3(CO)9(μ3-CCl): Isolation and X-ray structures of Co3(CO)9(μ3-CCO2Et), Co3(CO)9(μ3-CCH2CO2Et), and [Co3(CO)9(μ3-CCHCO2Et)]2

The reaction between the tricobalt cluster Co₃(CO)₉(₃-CCl) (1) and AlCl₃, followed by treatment with ethyl diazoacetate, N₂CHCO₂Et, affords a complex mixture of products in low yields. Column chromatography has allowed the isolation of the four cluster compounds Co₃(CO)₉(₃-CH) (2), Co₃(CO)₉(₃-CCO₂Et) (3), Co₃(CO)₉(₃-CCH₂CO₂Et) (4), and [Co₃(CO)₉(₃-CCHCO₂Et)]₂ (5). Clusters 4 and 5 are new and have been fully characterized in solution by IR and ¹H NMR spectroscopy. The molecular structures of clusters 3–5 have also been determined by single-crystal X-ray diffraction analysis. Co₃(CO)₉(₃-CCO₂Et) crystallizes in the triclinic space group P , a = 8.8393(5), b = 14.727(1), c = 15.272(1) Å, = 93.361(6), = 105.509(5)°, = 100.336(6)°, V = 1872.6(2) ų, Z = 4, and d _calc = 1.823 g/cm³. Co₃(CO)₉(₃-CCH₂CO₂Et) crystallizes in the monoclinic space group P2₁/n, a = 9.3806(7), b = 9.2617(8), c = 22.455(2) Å, = 94.483(7)°, V = 1944.9(3) ų, Z = 4, and d _calc = 1.803 g/cm³. [Co₃(CO)₉(₃-CCHCO₂Et)]₂ crystallizes in the monoclinic space group C2/c, a = 21.585(2), b = 8.7977(7), c = 20.784(1) Å, = 104.807(6)°, V = 3815.8(5) ų, Z = 4, and d _calc = 1.835 g/cm³. Plausible pathways leading to the formation of clusters 2, 4, and 5 are discussed.     

X-ray structure of [(μ-H)Os3(CO)10(μ-1,8-η2-C9H6N)]

Decacarbonyl--hydrido--1,8-²-quinoline-triosmium crystallizes in the triclinic space group P with a = 7.8551(6), b = 9.1283(8), c = 16.7915(8) Å, = 74.788(2), = 88.086(2), = 66.392(3)°, V = 1062.22(13)° ų, T = 150 K, and Z = 2. The molecule consists of an Os₃ triangle with the hydride and the heterocyclic ligand bridging the same Os—Os edge. The heterocyclic ligand is coordinated through the C(8) carbon and nitrogen atoms in a new -1,8-²-bonding mode. The Os—Os distances lie in the close range 2.8837(4)–2.9034(4) Å with an average value of 2.892(7) Å.     

Bridging and chelating diphosphine ligands in Ru3(μ-H)(μ-N=CPh2)(CO)8(P—P). X-ray diffraction structures of Ru3(μ-H)(μ-N=CPh2)(CO)8(dmpe) and Ru3(μ-H)(μ-N=CPh2)(CO)8(bpcd)

Treatment of the azavinylidene-bridged cluster Ru₃(-H)(-N=CPh₂)(CO)₁₀ (1) with the diphosphine ligand bis(dimethylphosphino)ethane (dmpe) gives Ru₃( -H)(-N=CPh₂)(CO)₈(dmpe) (2) in moderate yield, while the ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) reacts with Ru₃( -H)(-N=CPh₂)(CO)₁₀ in the presence of Me₃NO to furnish Ru₃( -H)(-N=CPh₂)(CO)₈(bpcd) (3) in low yield. Each new cluster has been isolated and characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies, and the coordination mode exhibited by the ancillary diphosphine ligand in 2 and 3 has been established by X-ray crystallography. Ru₃( -H)(-N=CPh₂)(CO)₈(dmpe) crystallizes in the monoclinic space group P2(1)/c, a = 10.791(1) Å, b = 16.377(1) Å, c = 18.148(1) Å, = 96.675(2)°, V = 3185.3(4) ų, Z = 4, D _cacl = 1.791 Mg/m³; R = 0.0360, R _w = 0.0866 for 7522 observed reflections with I > 2(I). Ru₃(-H)(-N=CPh₂)(CO)₈(bpcd) crystallizes, as the CH₂Cl₂ solvate, in the triclinic space group , a = 11.956(1) Å, b = 14.228(1) Å, c = 31.409(3) Å, = 89.377(2)°, = 79.344(2)°, = 77.235(2)°, V = 5118.4(8) ų, Z = 2, D _calc = 1.670 Mg/m³; R = 0.0557, R _w = 0.1069 for 10977 observed reflections with I > 2(I). The structural details of clusters 2 and 3 are contrasted with Ru₃(-H)(-N=CPh₂)(CO)₇(-dppm)(-dppm), which is the only known structurally characterized phosphine-substituted cluster of this genre.     

X-ray diffraction structure of Re2(CO)8[(Z)-Ph2PCH=CHPPh2]. Proof for diphosphine ligation across the Re–Re bond

Treatment of either Re₂(CO)₈(μ-H)(μ-η ¹,η ²-CH=CHBu) or Re₂(CO)₈(MeCN)₂ with the unsaturated diphosphine ligand (Z)-Ph₂PCH=CHPPh₂ gives the known bridging phosphine compound Re₂(CO)₈[(Z)-Ph₂PCH=CHPPh₂]. The solid-state structure of Re₂(CO)₈[(Z)-Ph₂PCH=CHPPh₂] was established by X-ray diffraction analysis, which confirmed the attachment of the diphosphine ligand to each rhenium center. Re₂(CO)₈[(Z)-Ph₂PCH=CHPPh₂] crystallizes in the tetragonal space group P4 ₂ bc, a = 18.054(2) Å, c = 22.289(4) Å, V = 7265(2) ų, Z = 8, and d _calc = 1.900. The two Re(CO)₄ units that are tethered by the diphosphine ligand exhibit a staggered rotational geometry.     

Reaction of 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) with fac-BrRe(CO)3(THF)2: X-ray diffraction structure of the dimeric complex [BrRe(CO)3]2(bpcbd) ⋅ CH2Cl2

Treatment of the diphosphine ligand 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) with the THF adduct fac-BrRe(CO)₃(THF)₂ at room temperature furnishes the new dirhenium compound [BrRe(CO)₃]₂(bpcbd) instead of the expected mononuclear compound fac-BrRe(CO)₃(bpcbd). [BrRe(CO)₃]₂(bpcbd) was characterized in solution by IR spectroscopy, and the solid-state structure was solved by X-ray crystallography. [BrRe(CO)₃]₂(bpcbd), as the CH₂Cl₂ solvate, crystallizes in the space group P , a = 11.173(1), b = 13.362(1), c = 15.250(1) Å, = 108.973(7)°, = 99.477(8)°, = 110.466(7)°, V = 1915.0(3) ų, Z = 2, and d _calc = 2.143 g-cm^–3. The structure of [BrRe(CO)₃]₂(bpcbd) consists of two rhenium centers that are six-coordinate and possess nearly ideal octahedral geometry. The two Re(CO)₃ units are linked together by the bridging diphosphine ligand and two bridging bromide groups.     

Regiospecific ligand addition to the donor–acceptor compound Ru2(CO)6(bpcd): syntheses and X-ray diffraction structures of Ru2(CO)5L(bpcd) and Ru2(CO)5L[μ-C=C(PPh2)C(O)CH2C}(O)](μ2-PPh2) (where L = PMe3 and tBuNC)

Thermal and Me₃NO-assisted activation of the donor–acceptor complex Ru₂(CO)₆(bpcd) (1) [where bpcd = 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione] with PMe₃ or ^tBuNC affords the mono-substituted complexes Ru₂(CO)₅L(bpcd), as a result of regiospecific ligand attack at the diphosphine-substituted ruthenium center. Solution NMR measurements (¹H and ³¹P) reveal that the PMe₃ derivative exists as a noninterconverting mixture of axial (3a) and equatorial (3e) isomers, with the only the equatorial isomer being observed for Ru₂(CO)₅(^tBuNC)(bpcd) (5). Near-UV irradiation of 1 in the presence of added ligand yields Ru₂(CO)₅L(bpcd), in addition to the known ₂-phosphido complex Ru²(CO)⁶ [-C=C(PPh₂)C(O)CH₂C(O)](₂-PPh₂) (2) and the corresponding phosphido-substituted complexes Ru²(CO)_5L[-{C =C(PPh₂)C(O)CH₂C}(O)]₂-PPh₂)[4 (L = PMe₃); 6 (L = ^tBuNC)]. As with compounds 3a, 3e, and 5, both 4 and 6 exhibit ligand attachment at the diphosphine-substituted ruthenium center. The molecular structures of 3e, 4, 5, and 6 were determined by X-ray crystallography. 3e, as the 1/2 C₆H₆ solvate, crystallizes in the monoclinic space group C2/c: a = 40.573(3) Å, b = 10.2663(9) Å, c = 18.347(1) Å, = 95.371(6)°, V = 7609(1) ų and Z = 8; 4, crystallizes in the monoclinic space group P2₁/n: a = 10.8241(8) Å, b = 18.074(1) Å, c = 19.194(1) Å, = 96.968(6)°, V = 3727.3(5) ų, and Z = 4; 5, as the 1/2CH₂Cl₂ solvate, crystallizes in the monoclinic space group C2/c: a = 40.955(3) Å, b = 9.7230(6) Å, c = 20.542(1) Å, = 106.596(5)°, V = 7839.2(9) ų, and Z = 8; 6, as the 1/2C₅H₁₂ solvate, crystallizes in the monoclinic space group P2₁/c: a = 21.773(2) Å, b = 10.907(3) Å, c = 18.744(4) Å, = 114.68(1)°, V = 4045(1) ų, and Z = 4. The site occupied by the PMe₃ and ^tBuNC ligands in these compounds is discussed relative to the steric size/electronic properties of the ancillary ligand and its interaction with the bpcd ligand.