B. A. Frenz

Fluxional organometallic molecules

Abstract The crystal structure and low temperature PMR spectra of the diironhexacarbonyl adduct of bicyclo[6.2.0]deca-1,3,5-triene have been determined. The entire body of data suggests that the ground state structure of the molecule is of the asymmetric cis-(1,2,6-trihapto-3,4,5-trihapto-cyclooctatriene)diironhexacarbonyl type previously found in (cyclooctatriene)diironhexacarbonyl and (cyclooctatetraene)diruthenium hexacarbonyl. Below −70° the PMR spectrum broadens and the complex spectrum in the slow exchange limit (−130°) is consistent with such an instantaneous structure. Above −70° the spectrum is indicative of a time-average plane of symmetry resulting from fluxionality of the molecule.Abstract The crystal structure and low temperature PMR spectra of the diironhexacarbonyl adduct of bicyclo[6.2.0]deca-1,3,5-triene have been determined. The entire body of data suggests that the ground state structure of the molecule is of the asymmetric cis-(1,2,6-trihapto-3,4,5-trihapto-cyclooctatriene)diironhexacarbonyl type previously found in (cyclooctatriene)diironhexacarbonyl and (cyclooctatetraene)diruthenium hexacarbonyl. Below −70° the PMR spectrum broadens and the complex spectrum in the slow exchange limit (−130°) is consistent with such an instantaneous structure. Above −70° the spectrum is indicative of a time-average plane of symmetry resulting from fluxionality of the molecule.

Conformations of cyclobutane

Abstract The literature concerning the structures of compounds containing saturated, 4-carbon rings is reviewed critically, and the variety of conformations (dihedral angles of 0° to 30° ± 6°) of the cyclobutane ring are tabulated and discussed.

Complexes of polypyrazolylborate ligands. V. Characterization of acety(tri-1-pyrazolylborato)(dicarbonyl)iron, (HBpz3)(COCH3)(CO)2Fe, in solution and in the crystal

Abstract The reaction of diiron enneacarbonyl with potassium tris-1-pyrazolylborate in the presence of excess methyl iodide affords an 8% yield of the new compound acetyl(tri-1-pyrazolylborato)(dicarbonyl)iron, 1 in addition to a larger quantity of the previously characterized by compound bis-(tri-1-pyrazolylborato)iron, 2. Compound 1 has been unequivocally characterized by elemental analyses, molecular weight measurement pmr spectrum, and X-ray crystallographic structure determination. The infrared spectrum of 1 in solution shows that conformers are present; these presumably differ in the rotational orientation of the acetyl group relative to the rest of the molecule. The principal crystallographic data are: space group P21/c; cell dimensions a = 9.233(1), b = 12.331(4), c = 15.507(2) A, β = 109.64(1)°, V = 1662.7(6) A3; observed and calculated densities ϱo = 1.40 gcm −3 ϱc = 1.36 gcm−3 for Z = 4. Least-squares refinement using 1804 counter data gave final conventional R factors of 0.035 and 0.040. The structure consists of well-separated monomeric units of (HBpz3) (COCH3)(CO)2Fe. Although not required crystallographically, the molecules possess near mirror symmetry. The coordination of the Fe atom is slightly perturbed from an octahedral arrangement, owing primarily to the non-orthogonal N-Fe-N angles of 86.8° (av). The pyrazolylborate nitrogen atoms occupy three mutually cis positions and the two CO groups are cis each other. the oxygen atom of the acetyl group lies over the bisector of the angle subtended at Fe by the carbonyl groups. The FeN bond distances are 1.992(4), 1.99(3), and 2.082(4) A (trans to acetyl); the Fe-C distances are 1.758(6), 1.771(5), and 1.968(5) A (acetyl).

Complexes of polypyrazolylborate ligands. VII. X-ray crystal structure of a complex containing both a unidentate pyrazole ligand and a bidentate pyrazolylborate ligand: (Diethylbispyrazolylborato) (pyrazylato)(trihaptoally)(dicarbonyl)molybdenum

Abstract The crystal structure (diethylbispyrazolylborato) (pyrazylato)(trihaptoally)(dicarbonyl)molybdenum, [Et2B(pz)2] (η3-C3H5)(Hpz)(CO)2Mo, crystallizes in the space group P21/n. Unit cell dimensions area = 8.144(2), b = 13.833(3), c = 18.792(3) A, β = 93.49(2)°; the density (by flotation) = 1.46 g cm−3; calculated (for Z = 4)1.459 g cm−3. The intensities of 2948 independent reflections were collected with Mo Kα radiation on a Syntex P 1 diffractometer. The structure was solved by the usual Patterson and Fourier methods and refined by full-matrix least-squares methods to final unweighted and weighted residuals of 0.027 and 0.037, respectively. The coordination geometries of the molybdenum and the boron atoms are distorted octahedral and tetrahedral, respectively The N-N distances are 1.367(4) A for the pyrazolylborate and 1.348(4) A in the pyrazole, with the Mo-N distances being 2.238(3) A and 2.237(3) A. The non-bonded distance between the Mo and boron is 3.806(4) A, approximately 1.0 A longer than the respective distances in the [H2B(Me2pz)2] (η3-C7H7(CO)2Mo and [H2B(Me2pz)2] (η3-C3H5(CO)2Mo molecules.

Copper(I) and copper(II) complexes of tetramethyldiphosphinedisulfide. I. Structural characterization of the dinuclear, molecular complex of copper(I) chloride

Abstract The potentially bidentate ligand, tetramethyldiphosphinedisulfide(CH3)4P2S2, has been found to react with copper(II) chloride dihydrate, CuCl2·2H2O, in ethanol at room temperature to yield, as the major product, a white compound. This is apparently the same substance reported in 1965 by Meek and Nicpon and formulated by them as [Cu(S2P2Me4)2][CuCl2) An X-ray crystallographic investigation has shown that the white substance is a molecular, dinuclear compound (which may, of course, dissociate or other- wise rearrange in solution) in which each Cu(I) is sur- rounded by a tetrahedral array of three sulfur atoms and one chlorine atom. The Me4P2S2 ligands have a gauche rotational configuration and each one chelates to one Cu(I) atom to form a five-membered ring. The Me4P2S4CuCl halves of the molecule are joined by two bridging sulfur atoms, one from each half, thus forming a planar Cu2S2 rhombic ring. The entire molecule has as its only symmetry element an inversion center. The principal crystallographic data are: space group, P21/n; a = 7.998(1) A; b = 9.688(2) A c = 14.473(3) A; β = 104.90(1)°; V = 1083.7(3) A3; Z = 2.

The molecular structure of the dimer of bis(tetramethyldiphosphinoethane)ruthenium that results from paired oxidative additions of CH bonds to two metal atoms

The compound of stoichiometry (Me 2 PCH 2 CH 2 PMe 2 ) 2 Ru reported in 1965 and formulated as a mononuclear species containing an RuH bond and a three-membered RuPC ring has been shown by x-ray crystallography to be a dinuclear species. This is formed by union of two dmpe 2 Ru molecules, where dmpe = Me 2 PCH 2 CH 2 PMe 2 , so that one CH bond of a methyl group in one unit adds oxidatively to the Ru atom of the other unit. A central ring with a chair configuration is formed and each metal atom is octahedrally coordinated by four P atoms, one C atom and one H atom. Crystal data: Space group, P ; Z = 4(dmpe 2 Ru); a = 10.028(4) A ; b = 13.880(6) A ; c = 15.018(6) A ; α = 95.87(3)°; β = 101.27(3)°; γ = 112.02(3)°; V = 1865(1) A 3 . There are two crystallographically independent dinuclear molecules, each located on an inversion center (at 0, 0, 0 and , , ). Anisotropic refinement of all non-hydrogen atoms gave residuals of R 1 = 0.052 and R 2 = 0.076. Using data for which λ −1 sin Θ A −1 the ligate hydrogen atoms were then located; a mean RuH distance of 1.67(7) A was obtained after refinement of the hydride positions.

Copper(I) and copper(II) complexes of tetramethyldiphosphinedisulfide. II. Isolation and characterization of a polymeric copper(II) precursor, (Me4P2S2)CuCl2, to the ultimate copper(I) product, [(Me4P2S2)CuCl]2

Abstract It has been found that the reaction of CuCl2·2H2O with Me4P2S2 in ethanol at room temperature affords a small amount of a brown, crystalline product as well as the major, white Cu(I) product, [(Me4P2S2)CuCl]2. The brown compound decomposes to form the white one if left in contact with the reaction mixture for a few hours. X-ray crystallographic investigation has shown that the brown compound has the stoichiometry (Me4P2S2)CuCI2 and that it crystallizes as an infinite polymer in which CuCl2 groups (∠ClCuCl = 141.4°) are connected by Me4P2S2 molecules. The latter retain their anti rotational configuration and are thus incapable of chelating. The SCuS angle is 137.3°; thus the coordination geometry at copper(II) is a flattened tetra- hedron. The mean metal-ligand distances are: CuCl, 2.22 A and CuS = 2.33 A. The principal crystallographic data are: space group, P21/c; a = 6.138(1) A; b = 15.452(5) A; c = 12.465(7) A; β = 93.30(40)°; V= 1180.1(8) A; z=4.

Characterization of a minor product of the reaction of diiron nonacarbonyl with cis-bicyclo[6.2.0]Deca-2,4,6-triene: trans-DI-μ-bis(2,3,4,5,6-pentahapto-tricyclo[6.2.0.02,6] deca-2,4dien-6-yl)dicarbonyldiiron(FeFe)

Abstract The identity of a minor product obtained from the reaction of diiron nonacarbonyl with cis-bicyclo[6.2.0]deca-2,4,6-triene has been ascertained by X-ray crystallography. The product, with the formula [(C10H11)Fe(CO)2]2, is a substituted [(h5-C5H5)Fe(CO)2]2 molecule in which the h5-C5H5 groups are replaced by penta hapto-tricyclo[6.2.0.O2,6]deca-2,4-dien-6-yl groups. The mechanism by which the C10H11 tricyclic system is formed from the initial bicyclo triolefin is obscure although (C10H11)FeH(CO)2 is a probable intermediate. The compound crystallizes in the monoclinic system, space group P21n with a = 9.231(4), b = 9.138(5), c = 12.140(6)A, β = 106.16(4)°, and Z = 2. The intensities of 928 independent reflections (2θmax = 45°) with I > 3 σ(I), collected on a computer-controlled diffractometer with Mo-Ka radiation were used to solve and refine the structure to R1 = 0.051 and R2 = 0.063.

The preparation, properties and crystal structure of bis(η5-cyclopentadienyldicarbonyliron)dimethylgermyl]oxide, [(η5-C5H5)(CO)2FeGe(CH3)2]2O☆

Abstract One of the main products of oxidation of (η 5 -C 5 -H 5 ) 2 Fe 2 (CO) 3 Ge(CH 3 ) 2 by air has been shown to be [(η 5 -C 5 H 5 )(CO) 2 FeGe(CH 3 ) 2 ] 2 O. The infrared, NMR and mass spectra are consistent with this formula and the detailed structure has been established by X-ray crystallography. In polar solvents the NMR suggests the existence of major and minor conformers interconverting only slowly on the NMR time scale at ≈ 25°. The X-ray diffraction study has shown the compound to consist of two (η 5 -C 5 H 5 )(CO) 2 FeGe(CH 3 ) 2 moieties joined by a bridging oxygen atom. Two rotational isomers are present in the unit cell in a disordered fashion. Some pertinent average distances and angles are: FeGe, 2.372 A; GeO, 1.785 A; GeOGe′, 134°. The compound crystallizes in the monoclinic system, space group P 2 1 / n , with a 8.056(2), b 12.506(2), c 22.631(3) A, β 98.01(1)°, d calc 1.692 g cm −3 . Counter data were collected using Mo- K α radiation. The 1780 reflections above background were used in least-squares refinement which converged at R 1 = 0.051 and R 2 = 0.068.

The molecular structure of a product of the reaction of bicyclo[6.2.0]deca-2,4,6-triene with diiron nonacarbonyl ☆

Abstract The reaction of bicyclo[6.2.0]deca-2,4,6-triene with diiron nonacarbonyl affords at least four products, one of which is a yellow substance with the empirical formula C10H12Fe2(CO)6. The structure of this substance has been determined by X-ray crystallography. The organic portion consists of a 1,3-cyclohexadiene ring with a CH2 group at the 5 position and an allyl group at the 6 position. One Fe(CO)3 group is bound to the 1,3-diene part of the organic group and another Fe(CO)3 group is bound to the CH2 group by a CFe σ bond and to the allyl group functioning as a trihapto allyl ligand. The essential crystallographic data are as follows: The space group is P 1 with a a = 7.140(3), b = 10.029(6), c = 13.875(5) Ǎ, α = 110.09(4)°, β = 118.50 (3)°, γ = 77.65(4)°, V = 818.5(7)Ǎ3 and Z = 2. The structure was solved by Patterson heavy atom methods. With all atoms located the conventional R value for 1210 observed reflections measured with a Syntex P 1 diffractometer is 0.044.