14878-28-5Relevant articles and documents
The structure and reactivity of phenylacetylene-derived metallacycles containing cobalt and mercury
Tyler, Stephen J.,Burlitch, James M.
, p. 231 - 247 (1989)
The crystal structure of the product of the reaction of phenylacetylene and Hg[Co(CO)4]2, viz. (C6H5)2C4H3[Co(CO)2HgCo(CO)4]2 (1) was determined by X-ray diffraction (space group C2/c; Z = 8; R = 0.051; a 22.08, b 11.62, c 28.08 A; β 114.78°) to be a C4Co2-containing dimetallacycle the cobaltcobalt bond distance of which (2.548(3) A) is asymmetrically bridged by the mercury atom of an HgCo(CO)4 moiety. The three-coordinate, bridging mercury atom, Hg(2), is 2.553(2) A from the π-bonded cobalt and 2.641(2) A from the σ-bonded cobalt of the metallacycle. This bridged Hg is compared to the semi-bridging CO in the iron metallacycles, Fe2(CO)6(C4R4)2. The two-coordinate mercury, Hg(1), of the second HgCo(CO)4 group is 2.475(2) A from the σ-bonded cobalt fo the metallacycle. Symmetrization reaction of 1 gave previously known Hg{Co2(CO)4(C6H5C2H)2[Hg-Co(CO)4]}2 (2), the structure of which was also determined by X-ray diffraction (space group P1; Z = 1; R = 0.065' a 11.448, b 12.757, c 10.353 A; α 94.37, β 75.49, γ 66.87°). Compound 2 contains two [HgCo(CO)4]-bridged metallacyclic units symmetrically disposed about a third Hg atom. The metal-metal distances of compound 2 are similar to those in 1. Sodium amalgam reduction of 1 gave, in addition to NaCo(CO)4, an anion postulated to be [(CO)2Co(η5-C5H2(C6H5)2O)]- (3) on the basis of its reaction with acetyl chloride to give 1-acetoxy-2,5-diphenyl-cyclopentadienyldicarbonylcobalt (4). Although no reaction was observed with acetic acid, treatment of 3 with trifluoroacetic acid produced a hydroxy-derivative, 5 analogous to the acetoxy compound, 4.
Chemistry of polyfunctional molecules. 133. X-ray crystal structural, solid-state 31P CP/MAS NMR, TOSS, 31P COSY NMR, and mechanistic contributions to the co-ordination chemistry of octacarbonyldicobalt with the ligands bis(diphenylphosphanyl)amine, Bis(diphenylphosphanyl)methane, and 1,1,1-Tris(diphenylphosphanyl)ethane
Bauer, Walter,Ellermann, Jochen,Dotzler, Martina,Pohl, Diana,Heinemann, Frank W.,Moll, Matthias
, p. 574 - 587 (2008/10/08)
Co2(CO)8 reacts with bis(diphenylphosphanyl)-amine, HN(PPh2)2 (Hdppa, 1), in two steps to afford the known compound [Co(CO)(Hdppa-κ2P)2][Co(CO)4] · 2 THF (6a · 2 THF). The intermediate [Co(CO)2(Hdppa-κ2P) · (Hdppa-κP)] [Co(CO)4] · dioxane · n-pentane (5 · dioxane · n-pentane) was isolated for the first time and was characterized by X-ray analysis. The cation 5+ exhibits a slightly distorted trigonal-bipyramidal geometry. Detailed 31P-NMR investigations (solid-state CP/MAS NMR, TOSS, 31P-COSY, 31P-EXSY) showed that the additional tautomer [Co(CO)2(Hdppa-κ2P)(Ph2P-N=P(H)Ph 2-κP)]+ (5′+) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state only tetragonal pyramidal species of 5 are found in solution. At -90°C there is slow exchange between the three diastereomeric species 5a+-5c+. Compound 5 forms [Co(CO) · (Hdppa-κ2P)2]BPh4 · THF (6b · THF) in THF with NaBPh4 under CO-Elimination. A X-ray diffraction investigation shows that the cation 6+ consists of a slightly distorted trigonal-bipyramidal co-ordination polyeder. However, a distorted tetragonal-pyramidal structure has been found for the cation 7+ of the related compound [Co(CO)(dppm)2][Co(CO)4] · 2THF (7 · 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph2PCH2PPh2). A comparison with the known [8] trigonal-bipyramidal stereoisomer, ascertained for 7+ of the solventfree 7, is described. In solutions of 6a · 2 THF and 7 · 2 THF 13C{1H}- and 31P{1H}-NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cation and cobalt(-I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism by forming binuclear substitution products such as the isolated Co2(CO)2 · (μ-CO)2(μ-dppm)2 · 0.83 THF (8 · 0.83 THF), which was characterized by spectroscopy and X-ray analysis. For_the dissolved [Co(CO)2CH3C(CH2PPh2) 3][Co(CO)4] · 0.83 n-pentane (9 a · 0.83 n-pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9a · 0.83 n-pentane with NaBPh4 yields [Co(CO)2CH3C(CH2PPh2) 3]BPh4 (9b) which has been characterized by single-crystal X-ray analysis. The cation shows a small distorted tetragonal-pyramidal structure.
Alkylcobalt carbonyls. 10. CO activation and phase-transfer-active coordination sites in organocobalt carbonyls. Mechanism of the reaction of benzyl halides and tetracarbonylcobaltate (-I)
Haász, Ferenc,Bartik, Tamás,Galamb, Vilmos,Pályi, Gyula
, p. 2773 - 2779 (2008/10/08)
(4′-Halomethyl-1′,2′-benzo)-15-crown-5 (RX, 1; X = Cl (a), I (b)) compounds were reacted with Na-[Co(CO)4] (2). The corresponding η1-RC(O)Co(CO)4 (5), η1-RCo(CO)4 (6), and η3-RCo(CO)3 (7) derivatives were obtained through intermediates [(η5-RX)Na][Co(CO)4] (3) and [(η5-Na+)RC(O)Co(CO)3(X-)] (4). The reactions leading to 7 from 1 were found to be reversible. Derivatives of 4 and 5 were prepared by monosubstitution with PPh3, giving 8 and 9, respectively. The reversibility of the reaction of PhCH2Cl with 2 was also demonstrated.
Alkylcobalt carbonyls. 9. Alkoxy-, silyloxy-, and hydroxy-substituted methyl- and acetylcobalt carbonyls. Reduction of formaldehyde to methanol by hydridocobalt tetracarbonyl
Sisak, Attila,Sámpár-Szerencsés, Ella,Galamb, Vilmos,Németh, László,Ungváry, Ferenc,Pályi, Gyula
, p. 1096 - 1100 (2008/10/08)
(Alkoxymethyl)-, ((silyloxy)methyl)-, and (hydroxymethyl)cobalt and (alkoxyacetyl)-, ((silyloxy)acetyl)-, and (hydroxyacetyl)cobalt tetracarbonyls and phosphine-substituted derivatives were prepared. The interconversions of these compounds by carbonylatio
Synthesis and Properties of Na3-C3H5Fe(NO)(CO)CN> and η3-C3H5Fe(NO)(CO)CNMe (η3-C3H5 = Allyl)
Moll, Matthias,Behrens, Helmut,Seibold, Hans-Juergen,Merbach, Peter
, p. 409 - 410 (2007/10/02)
The allyl iron complexes η3-C3H5Fe(NO)(CO)L (L = CN(-), CNMe) can be obtained by the reaction of η3-C3H5Fe(NO)(CO)2 with NaN(SiMe3)2 and subsequent methylation. - Keywords: Allyl Nitrosyl Carbonyl, Cyano, Isonitrile Iron Complexes
Synthesis, stereochemistry, and bonding of the cobalt-cobalt multiple-bonded (pentamethylcyclopentadienyl)- and cyclopentadienylcobalt carbonyl dimers, a comparative analysis of the antibonding dimetal nature of the unpaired electron in the monoanions and its structural effects upon oxidation
Cirjak, Larry M.,Ginsburg, Robert E.,Dahl, Lawrence F.
, p. 940 - 957 (2008/10/08)
The preparation, properties, structure, and resulting bonding implications of the (pentamethylcyclopentadienyl)cobalt carbonyl neutral dimer, [Co2(η5-C5Me5) 2(μ-CO)2]n (n = 0), and its paramagnetic monoanion (n = 1-) as the [Na(2,2,2-crypt)]+ salt are reported together with the corresponding cyclopentadienyl [Co2(η5-C5H5) 2(μ-CO)2]- monoanion as the tetraphenylarsonium salt. Distinct geometrical differences are found among the solid-state structures of the neutral dimer and both monoanions. The entire molecular configuration of the neutral dimer closely conforms to C2ν-m2m symmetry with the two eclipsed, almost parallel C5Me5 rings being essentially perpendicular to the nearly planar Co2(CO)2 core, which is puckered by only 4-5° from planarity. In contrast, the C5Me5-containing monoanion exhibits the following marked geometrical distortions: (1) its Co2(CO)2 core is significantly puckered by 10-12° from planarity; (2) the two C5Me5 rings are twisted from an eclipsed conformation and inclined by 26.5° from being coparallel; (3) one of the two bridging carbonyl ligands possesses extremely large out-of-plane thermal ellipsoids indicative of an averaged structure in which this one bridging carbonyl occupies at least two bent orientations in the crystalline state. The fact that the corresponding electronically equivalent C5H5-containing monoanion (of crystallographic Ci-1 site symmetry) experimentally conforms to a C2h-2/m geometry consisting of a planar D2h Co2(CO)2 core with perpendicular C5H5 ligands points to steric effects being responsible for the considerable distortion of the C5Me5-containing monoanion from an analogous geometry. Despite these geometrical differences, the corresponding Co-Co and Co-CO bond lengths (for the well-behaved bridging carbonyl) in the C5Me5-containing monoanion are only 0.008 and 0.012 A? longer, respectively, than those in the C5H5-containing monoanion. Salient structural differences between the two members of the [Co2(C5Me5)2(μ-CO) 2]n series (n = 0, 1-) are completely consistent with the Pinhas-Hoffmann energy-level ordering diagram, which for each monoanion places the unpaired electron in a HOMO (of b2 representation under C2ν symmetry) composed mainly of out-of-plane antibonding π* dimetal symmetry orbital character. In the C5Me5-containing monoanion, the Co-Co and Co-CO bond lengths are 2.372 (1) and 1.827 A? (average of 1.820 (6) and 1.834 (6) A?), respectively, while the corresponding bond lengths in its oxidized neutral dimer are 2.338 (2) and 1.851 A? (average of four values in the range 1.841 (12)-1.860 (12) A?), respectively. Hence, removal of an electron from the monoanion results in a shortening of the Co-Co distance by 0.034 A? and a concomitant lengthening of the mean Co-CO bond length by 0.024 A?. The much smaller observed decrease in the Co-Co bond length relative to that of 0.08 A? predicted by Pinhas and Hoffmann from quantum-mechanical calculations may be readily ascribed to the simultaneous increase in the lengths of the Co-CO bonds (upon oxidation of the monoanion), which in being much stronger than the Co-Co interactions are the dominant factor in opposing any decrease in the Co-Co distance. The fact that the imposed symmetry of the HOMO (b2) precludes any carbonyl orbital character for a planar Co2(CO)2 core points to the observed increase in the Co-CO bond lengths being an indirect consequence of the loss of negative charge, which in turn lowers the metal AO's relative to the π*(CO) symmetry Orbitals (SO's) and thereby decreases the dπ(Co) → π*(CO) back-bonding; this charge effect is also in harmony with the IR carbonyl frequency of 1670 cm-1 for the monoanion in THF solution being 80 cm-1 less than that of 1750 cm-1 for the neutral dimer in THF solution. Additional bond length evidence that the LUMO in the neutral dimer and HOMO in its reduced monoanion is the out-of-plane MO (b2), which from energetic considerations must have considerable [dyz(Co)-e1-(Cp ring)]* antibonding character, has been uncovered from the distinct geometrical variations in the corresponding Co-C5Me5(ring) and C(ring)-C(ring) distances between the neutral Co2(η5-C5Me5) 2(μ-CO)2 dimer and the previously analyzed Co(η5-C5Me5)(CO)2 molecule.
