X-ray diffraction structure of the 1,1′-bis(diphenylphosphino)ferrocene (dppf)-bridged complex [(dppf)AgCl]2: An unexpected product from the reaction betweencis-(bpy)2RuCl2 and dppf in the presence of AgBF4

The reaction betweencis-Ru(bpy)₂Cl₂ (where bpy=bipyridine) and the diphosphine ligand 1,1-bis(diphenylphosphino)ferrocene (dppf) in the presence of AgBF₄ has led to the isolation of the title compound [Ag(dppf)Cl]₂. [Ag(dppf)Cl]₂ has been structurally characterized by X-ray diffraction analysis, which confirms the bridging mode adopted by the ancillary dppf ligand and the centrosymmetric nature of this molecule. Dimeric [Ag(dppf)Cl]₂ crystallizes in the triclinic space group ,a=11.426(1) Å,b=11.509(1) Å,c=12.786(1) Å, =68.96(2)°, =70.66(2)°, =71.24(2)°,V=1441(1) ų,Z=1,d _calc=1.608 g·cm^–3;R=0.0445,R _w=0.0566 for 4486 observed reflections withl>3(l)     

Crystal and molecular structure of complex compound [Fe3O(CH3COO)6(H2O)3]2[ZnCl4] ⋅ 2H2O

The X-ray crystal structure of trinuclear iron acetate [Fe₃O(CH₃COO)₆(H₂O)₃]₂ [ZnCl₄] ? 2H₂O was determined. The crystal has a ionic structure. It is monoclinic, a = 25.363(7), b = 14.533(4), c = 15.692(4) Å, β = 103.11(2)°, space group _C2/c, and R = 0.0685. The structure of the cationic complex [Fe₃O(CH₃COO)₆(H₂O)₃]⁺ is typical of trinuclear iron(III) compounds containing a μ₃-O bridge: the iron atoms are situated at the vertices of an almost equilateral triangle with the O atom at the center. Each Fe atom is coordinated by four O atoms of bridging carboxy groups, the μ₃-bridging O atom, and the water molecule in the trans position to the latter O atom. Mössbauer spectroscopy evidence indicates the high-spin state (_S = 5/2) of the iron(III) ions.     

Molecular structure of [trans-FeCl2(imidazole)4]Cl·THF·H2O

The structure of [trans-FeCl₂(imidazole)₄]Cl has been determined as the THF/H₂O solvate. The Fe-Cl and Fe-N distances in the cation are shorter than analogous trans-FeCl₂(L)₄ compounds, concomitant with the decreased ionic radius of Fe³⁺ versus Fe²⁺. Crystal data: orthorhombic, Pnma, a = 8.456(2), b = 20.991(4), c = 13.288(3) Å, V = 2358.6(8), andZ = 4.     

Reactions of [Mn2(μ-pyS)2(CO)6] with bidentate phosphines: X-ray structure of [Mn(η2-pyS) (η2-dppp)(CO)2] [dppp = Ph2P(CH2)3PPh2, pySH = pyridine-2-thiol]

The dimeric complex [Mn₂(-pyS)₂(CO)₆] (1) reacted with 2 molar equivalents of Ph₂P(CH₂)₃PPh₂ (dppp) and Ph₂P(CH₂)₂PPh₂ (dppe) to give the respective monomeric chelate complexes [Mn(²-pyS)(²-dppp)(CO)₂] (2) and [Mn(²-pyS)(²-dppe)(CO)₂] (3). In contrast, with 2 molar equivalents of Ph₂P(CH₂)₅PPh₂ (dpppe), 1 gave the highly insoluble polymeric complex [Mn(²-pyS)(-dpppe)(CO)₂]n (4). An X-ray structure determination shows that 2 crystallizes in the monoclinic space group P2₁/n with a = 10.721(2) Å, b = 19.712(5) Å, c = 14.846(4) Å, = 109.06(2)°, V = 2965.5(14) ų, and Z = 4. The complex has a distorted octahedral geometry with the dppp ligand, one CO group and the N atom of the chelating pyS ligand occupying equatorial sites, and one CO group and the S atom of the pyS ligand lying in the axial positions.     

Diphosphine ring expansion and π-bond reduction in the reaction between 1,2-bis(diphenylphosphino) cyclobutenedione (bpcbd) and Ru3(CO)10(MeCN)2: X-ray diffraction structures of Ru3(CO)10[2,3- bis(diphenylphosphino)succinic anhydride] and Ru2(CO)6(bma)

Replacement of the acetonitrile ligands in Ru₃(CO)₁₀(MeCN)₂ by the diphosphine ligand 1,2-bis(diphenylphosphino)cyclobutenedione (bpcbd) initially gives the unstable bpcbd-bridged cluster Ru₃(CO)₁₀(bpcbd) (1), followed by its subsequent transformation to the triruthenium cluster Ru₃(CO)₁₀(bma) (2). The decomposition of cluster 2 serves to produce the ruthenium compounds Ru₃(CO)₁₀[2,3-bis(diphenylphosphino)succinic anhydride] (3) and Ru₂(CO)₆(bma) (4). Compounds 2–4 provide the experimental evidence for the ring expansion of the cyclobutenedione ring via the formal insertion of an oxygen atom into the four-membered ring and hydrogen addition to the bond upon exposure to the atmosphere and/or moisture. Both 3 and 4 have been isolated and characterized in solution by IR and ³1P NMR spectroscopies, and the molecular structure of each product has been verified by X-ray crystallography. Ru₃(CO)₁₀[2,3-bis(diphenylphosphino)succinic anhydride] crystallizes, as the CH₂Cl₂ solvate, in the monoclinic space group P2₁/c, a = 12.178(2)Å, b = 15.988(2)Å, c = 22.472(3)Å, = 95.115(2)°, V = 4358(1)ų, Z = 4, and d_calc = 1.732 Mg/m³; R = 0.0344, R_w = 0.0931 for 5683 reflections with I > 2(I). The dinuclear compound Ru₂(CO)₆(bma) crystallizes in the triclinic space group P-1, a = 9.298(3)Å, b = 12.020(3)Å, c = 30.858(8)Å, = 81.774(5)°, = 89.276(5)°, = 83.545(4)°, V = 3391(1)ų, Z = 4, and d_calc = 1.730 Mg/m³; R = 0.0670, R_w = 0.1444 for 8766 reflections with I > 2a(I).     

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).     

Synthesis and crystal structure of [WI(CO)(cis-dppen) η2-MeC2Me)2]I·CH2Cl2 {cis-dppen = bis(diphenylphosphino)ethene}

The complex [WI(CO)(cis-dppen)(²-MeC₂Me)₂]I·CH₂Cl₂(1) is prepared as a by-product from the reaction of equimolar quantities of [WI₂(CO)(NCMe)(²-MeC₂Me)₂] and cisdppen {dppen = bis(diphenylphosphino)ethene}. Complex 1, [WI(CO)(cis-dppen)(²-MeC₂Me)₂]I·CH₂Cl₂ crystallizes in the triclinic space group with a = 11.189(13), b = 12.331(14), c = 15.395(17) Å, = 83.61(1), = 86.06(1), = 64.48(1)°, U = 1904 ų, and Z = 2. The metal environment in the cation can best be considered as a distorted octahedron with the two but-2-yne groups taking up individual sites trans to phosphorus atoms of the dppen ligand. The coordination sphere is completed by mutually trans-carbonyl and iodide groups.     

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.     

Model of the crystal structure of Np(VI) sulfate with dimethyl sulfoxide, NpO2SO4 ⋅ 2SO(CH3)2 ⋅ H2O

A new complex compound, neptunium(VI) sulfate, was grown from aqueous solutions and studied by the methods of X-ray structure analysis. The model of the crystal structure was determined by direct methods within the sp. gr. P2₁ and was refined in the anisotropic approximation (R = 6.2%, 1044 independent reflections). The structure is built by tetragonal and hexagonal Np bipyramids. A hexagonal bipyramid can be considered as a polyhedron derived from a pentagonal bipyramid, in which one equatorial O atom is replaced by two atoms located above and below the equatorial plane. The polyhedra are linked in chains through S-tetrahedra. The chains are linked into a three-dimensional framework by hydrogen bonds with the participation of DMSO groups.     

Reactions of [Mn2(μ-pyS)2(CO)6] (pySH=pyridine-2-thiol) with triphenylphosphine (PPh3), diphenylphosphine (PHPh2) and bis(diphenylphosphino)methane (dppm): X-ray crystal structure of [Mn(pyS)(η1-dppm)2(CO)2]

The dimeric complex [Mn₂(-pyS)₂(CO)₆] (1) reacted with 2 M equivalents of both PPh₃ and PHPh₂ to give the respective monomeric phosphine complexes [Mn(pyS)(L)(CO)₃][L = PPh₃ (2) and PHPh₂ (3)]; with 4 M equivalents of dppm, it yielded the complex [Mn(pyS)(¹-dppm)₂(CO)₂](4). An X-ray structure determination of 4 shows that it crystallizes in the monoclinic space group P2₁/n with a = 11.027(3), b = 24.984(7), c = 18.379(5) Å, = 99.870(8)°, V = 4988(2) ų, and Z = 4. The complex has an octahedral geometry with the chelating pyS ligand and two CO groups occupying the equatorial sites and the two monodentate dppm ligands lying in the trans positions.     

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.     

Interaction of cystamine with palladium(II) monoethanolaminate complex: Crystal structure of [Pd(NH2CH2CH2OH)4][Pd6(NH2CH2CH2S)8]Cl6 · 5H2O

The new compound [Pd(NH₂CH₂CH₂OH)₄][Pd₆(NH₂CH₂CH₂S)₈]Cl₆ · 5H₂O (I) is synthesized and its crystal structure is determined. The crystals are monoclinic, a = 25.625(6) Å, b = 9.633(5) Å, c = 24.847(7) Å, β = 91.47(2)°, Z = 4, and space group C2/c. The structural units of crystals I are the centrosymmetric hexanuclear [Pd₆(NH₂CH₂CH₂S)₈]⁴⁺ cations, the mononuclear [Pd(NH₂CH₂CH₂OH)4]²⁺ cations with C ₂ symmetry, the Cl^? anions, and crystallization water molecules. In the hexanuclear cation, the interaction between the Pd atoms occurs through the S atoms of the mercaptoethylaminate ligands. The Pd(2) and Pd(3) atoms and the ligands form two metallochelate fragments in which the N and S atoms are located in cis positions. The average lengths of the Pd-S and Pd-N bonds are equal to 2.274(1) and 2.074(6) Å, respectively. The metallochelate fragments are joined to each other and to their centrosymmetric analogues through the Pd(1) atom, which coordinates four S atoms [the average Pd-S_av bond length is 2.332(1) Å]. In the mononuclear cation, the Pd(4) atom coordinates four N atoms of the monoethylaminate ligands [the Pd-N bond lengths are 2.045(6) and 2.056(6) Å]. The shortest Pd?Pd distance is equal to 3.207(1) Å. The bonding in the structure is provided by numerous hydrogen bonds with the participation of all the H₂O molecules, NH₂ groups, and Cl^? anions.     

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}].     

Crystal structure and vibrational spectra of two cadmium halide complexes with 1,2-Bis[2-(Diphenylphosphinylmethyl)phenoxy]ethane (L 1) and 1,3-bis[2-diphenylphosphinylmethyl)phenoxy]propane (L), CdBr2 ⋅ L 1 and CdI2 ⋅ L

Two cadmium halide complexes with 1,2-bis[2-(diphenylphosphinylmethyl)phenoxy]ethane (L ¹) and 1,3-bis[2-(diphenylphosphinylmethyl)phenoxy]propane (L), namely, CdBr₂ ? L ¹ (I) and CdI₂ ? L(II), have been synthesized. An analysis of their vibrational spectra is carried out. The structures of I and II are determined by X-ray diffraction. Crystals I are monoclinic, a = 31.562(6) Å, b = 13.548(3) Å, c = 18.733(4) Å, β = 91.28(3)°, space group C2/c, Z = 8, and R = 0.051 for 3776 reflections. Crystals II are triclinic, a = 11.803(2) Å, b = 12.554(3) Å, c = 14.686(3) Å, α = 90.30(3)°, β = 90.29(3)°, γ = 106.08(3)°, space group $P\bar 1$ , Z = 2, and R = 0.043 for 4916 reflections. Compounds I and II exhibit a polymeric chain structure. The potentially tetradentate ligands L ¹ and L are coordinated to the metal atoms only through two phosphoryl oxygen atoms and fulfill the bidentate bridging function. The environment of the Cd atom is completed to the tetrahedral coordination by two Br atoms in complex I and two I atoms in complex II. The mean distances are as follows: Cd-Br, 2.526(2) Å; Cd-I, 2.695 Å; and Cd-O, 2.243(8) Å in I and 2.210(4) Å in II. The L ¹ and L ligands in complexes I and II adopt an S-shaped conformation.     

Synthesis and structure of an unusual complex formed between 1,2-bis(3′-pyridyl)ethyne and C-methyl calix[4]resorcinarene

The X-ray crystal structure of the complex formed between 1,2-bis(3-pyridyl)ethyne and C-methylresorcinarene is described. The structure (C₄₅H₄₇N₃O₁₂) is monoclinic with a = 11.8086(7), b = 31.2037(17), c = 11.2933(6) Å, = 101.9330(10)° and space group P2₁/c. The structure reveals that the resorcinarene adopts the common bowl-shaped conformation however the four intramolecular hydrogen bonds are arranged asymmetrically. One of the pyridyl rings sits inside the resorcinarene and is hydrogen bonded to two adjacent resorcinarenes.     

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 diethoxynitrobenzene-p-tert-butylcalix [4]arene⋅2(CH3)2C=O: Evidence of intra- and intermolecular CH/π interactions forced by crystal packing

Diethoxynitrobenzene-p-tert-butylcalix[4]arene2(CH₃)₂C=O crystallized in the monoclinic system, space group P2₁/c, with cell dimensions a = 16.1437(2) Å, b = 21.0292(2) Å, c = 18.9685(3) Å and = 110.308(1)°. The asymmetric unit consists of a diethoxynitrobenzene-p-tert-butylcalix[4]arene molecule and two solvated acetone molecules. Besides the usual CH/ interaction between p-tert-butylcalix[4]arene cavity and a solvated acetone, this structure shows the intra- and intermolecular CH/ interactions among a nitrobenzene ring, ethylene bridge of the ethoxynitrobenzene side chain and a solvated acetone molecule.     

Hydrothermal crystallization and X-ray structure determination of a new decavanadate with mixed cations [Mn(H2O)6]2[N(CH3)4]2[V10O28]·2H2O

A new decavanadate with mixed cations, [Mn(H₂O)₆]₂[N(CH₃)₄]₂[V₁₀O₂₈]·2H₂O (1), was crystallized from a hydrothermal reaction between MnCO₃ and V₂O₅ in the presence of N(CH₃)₄Br at 100°C. The structure of 1, as determined by x-ray single crystal analysis, consists of cations and anions of hexa-aqua manganese [Mn(H₂O)₆]²⁺, tetramethyl ammonium [N(CH₃)₄]⁺ and decavanadate [V₁₀O₂₈]^6–. The extended H-bonding between the [Mn(H₂O)₆]²⁺ and [V₁₀O₂₈]^6– ions gives rise to a pseudo- two-dimensional network in the crystal lattice x-ray crystallographic data for 1: monoclinic P2₁/n, a = 9.1499(5), b = 12.8725(7), c = 18.625(1) Å, = 92.252(1)°, V = 2192.0(2) ų, MZ = 2, and D _calcd = 2.22 g cm^–3.     

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.