259875-26-8Relevant articles and documents
Mixed chloride/amine complexes of dimolybdenum(II,II). 6. Stepwise substitution of amines by tertiary phosphines and vice versa: Stereochemical hysteresis
Cotton, F. Albert,Dikarev, Evgeny V.,Herrero, Santiago
, p. 609 - 616 (2008/10/08)
The substitution reactions of primary amines by tertiary phosphines in quadruply bonded, dimolybdenum(II,II) complexes Mo2Cl4(NH2R)4 have been studied. The exchange reaction has been shown to result at room temperature in disubstituted species Mo2Cl4(NH2R)2(PR3)2 (PR3 = PMe3, NH2R = NH2Pr(n) (1a), NH2Bu(t) (2a), NH2Cy (3a); PR3 = PMe2Ph, NH2R = NH2CY (4a)), while heating is needed to obtain fully substituted complexes Mo2Cl4-(PR3)4. The crystal structure of disubstituted products has been investigated by X-ray crystallography and revealed that they all belong to the α-isomer, having both phosphine groups at the same Mo atom. Crystal data are as follows: for 1a, tetragonal space group I41/a with a = 17.737(2) A, c = 15.6915(6) A, and Z = 8; for 3a, monoclinic space group P21 with a = 10.963(3) A, b = 10.117(2) A, c = 13.323(4) A, β = 90.05(2)°, and Z = 2; for 4a, triclinic space group P1 with a = 9.329(3) A, b = 10.206(2) A, c = 18.975(3) A, α = 85.45(2)°, β = 87.10(1)°, γ = 80.88(1)°, and Z = 2. The substitution processes for the direct and reverse reactions have been monitored by 31P NMR. They both proceed in a stepwise manner; however, a stereochemical hysteresis is taking place, i.e., the back reaction, the substitution of phosphines by amines, goes through another isomer of Mo2Cl4-(NH2R)2(PR3)2, having phosphine ligands on different Mo atoms. This β-isomer is more thermodynamically stable and can be obtained by thermal conversion of the α-form. All chemical equilibria studied in the paper have been explained as governed by a higher trans effect of PR3 groups compared to NH2R groups.
Triangular Trinuclear Cluster Compounds: Molybdenum and Tungsten Complexes of the Type + with X = Cl and H
Cotton, F.Albert,Llusar, Rosa,Eagle, Cassandra T.
, p. 4332 - 4338 (2007/10/02)
New synthetic methods of an essentially nonaqueous nature are reported for the preparation of compounds containing the Mo3S44+ and W3S44+ cluster cores surrounded by a combination of diphosphine ligands and either Cl- or H- ligands.The synthetic methods entail reactions of MoCl3(THF)3 or WCl4 with NaHS and dmpe (or depe) in THF to obtain the chloro species and treatment of tungsten chloro compounds with LiBH4 to obtain the hydrido compounds.The new compounds described in detail (including crystal structures for those marked*) are as follows: CH3OH* (1), *H2O* (2), * (3), * (4), and (5).Compounds 1 and 2 form isomorphous crystals in space group R3c with Z=6; for 1, a = 15.310 (7) Angstroem and c = 30.640 (3) Angstroem; for 2, a = 15.269 (2) Angstroem and c = 30.620 (6) Angstroem.The two cations have almost identical dimensions, with Mo-Mo = 2.766 (4) Angstroem, W-W = 2.755 (1) Angstroem, and all other distances (e.g., M-S, M-Cl, M-P) equal within +/- 0.01 Angstroem.In each case, the dmpe ligands span positions such that one P is trans to μ3-S and the other trans to a μ2-S atom within the approximately octahedral coordination sphere, MS3ClP2, about each metal atom.The cations are therefore chiral.The + ion in compound 3 is very similar to the + ion in 2.Compound 3 crystallizes in space group P with Z = 2, a = 15.552 (6) Angstroem, b = 17.768 (7) Angstroem, c = 10.572 (3) Angstroem, α = 106.54 (3) deg, β = 98.25 (3) deg, γ = 95.70 (3) deg.Compound 4 has a cation nearly isostructural with that in 2 except that each Cl atom is replaced by an (X-ray-invisible) H atom.The W-W distances are equal in the two cations.Compound 4 crystallizes in space group P21/c with Z = 4, a = 14.947 (2) Angstroem, b = 11.237 (2) Angstroem, c = 32.942 (5) Angstroem, β = 97.90 (1) deg.The two hydrido compounds, 4 and 5, react smoothly with PhCOCl to regenerate the chloro compounds.The + ion undergoes two quasirreversible one-electron reductions (-0.64 and -0.85 V vs Ag/AgCl electrode).The + and + ions showed reductions at -1.11 and -1.12 V that appear to produce unstable products.NMR studies of the cation in 2, 4, and 5 support the formulation of 4 and 5 as hydride complexes. 4 and 5 show (1)H resonances at -0.914 and -0.80 ppm, respectively, which appear as doublets of doublets with 2JHP values of 30 and 45 Hz and satellites with 1JHW of ca. 30 Hz.
Complexes containing unbridged homonuclear or heteronuclear quadruple bonds. Crystal and molecular structures of MoWCl4(PMePh2)4, MoWCl4(PMe3)4, and Cl2(PMe3)2MoWCl2(PMePh 2)2
Luck, Rudy L.,Morris, Robert H.,Sawyer, Jeffery F.
, p. 2422 - 2429 (2008/10/08)
The reactions of Mo(η6-PhPMePh)(PMePh2)3 and Mo(η6-PhPMe2)(PMe2Ph)3 with MoCl4(THF)2 yield the homonuclear unbridged quadruply bonded complexes Mo2Cl4(PR3)4 (PR3 = PMePh2 (1), PMe2Ph (2)). Complex 1 readily undergoes phosphine substitution with PMe3 to yield Mo2Cl4(PMe3)4 (3). The reactions of Mo(η6-PhPMe2)(PMe2Ph)3 and Mo(η6-PhPMePh)(PMePh2)3 with WCl4(PPh3)2 yield the complexes MoWCl4(PR3)4 (PR3 = PMe2Ph (4), PMePh2 (5)), which are among the first to contain an unbridged quadruple bond between two different elements. Complex 5 undergoes phosphine substitution reactions with PMe3 to give sequentially Cl2(PMe3)2MoWCl2(PMePh 2)2 (6) and then MoWCl4(PMe3)4 (7). Complex 4 can also be synthesized by reacting 5 with PMe2Ph. The 31P and 1H NMR spectra, electronic and visible spectra, and cyclic voltammograms of these complexes are interpreted, and the crystal and molecular structures of 5-7 are reported. Compounds 5 and 7 were found to have disordered arrangements of the metal atoms; compound 6 with the different phosphine ligands on the metal atoms is, however, ordered with a Mo4-W bond length of 2.207 (1) A?. In 6 and 7 the molecules have crystallographic 2-fold symmetry. In all three structures the ligand arrangement over the metal-metal bond defines an eclipsed geometry with chlorine next to phosphine across the bond in a pseudo-D2d arrangement. The metal-metal distances in 5 and 7 are 2.208 (4) (average) and 2.2092 (7) A?, respectively. These values are close to distances expected on the basis of homonuclear M4-M bonds, and therefore there is no extra shortening of these bonds due to electronegativity differences. Crystal data: 5, monoclinic, space group P21/a, a = 21.511 (4) A?, b = 12.176 (6) A?, c = 40.863 (8) A?, β = 92.65(2)°, V = 10692 A?3, Dcalcd = 1.52 g cm-3 for Z = 8, R = 0.0957 for 3554 observed (I > 3σ(I)) reflections; 6, monoclinic, space group I2/a, a = 16.817 (4) A?, b = 11.925 (3) A?, c = 19.685 (5) A?, β = 103.87 (2)°, V = 3832.4 A?3, Dcalcd = 1.69 g cm-3 for Z = 4, R = 0.0364 for 2203 observed reflections; 7, monoclinic, space group I2/a, a = 17.312 (4) A?, b = 9.193 (1) A?, c = 19.085 (3) A?, β = 119.69 (2)°, V = 2638.9 A?3, Dcalcd = 1.57 g cm-3 for Z = 4, R = 0.0312 for 2084 observed reflections.
The tungsten-tungsten triple bond. 11. Ligand redistribution reactions involving chloride and dimethylamide ligands at dimolybdenum and ditungsten (M≡M) centers induced by added tertiary phosphines. Preparations and characterizations of W2Cl2(NMe2)4(Me2PCH 2PMe2), W2Cl3(NMe ...
Ahmed, Kazi J.,Chisholm, Malcolm H.,Folting, Kirsten,Huffman, John C.
, p. 4039 - 4044 (2008/10/08)
Full title: The tungsten-tungsten triple bond. 11. Ligand redistribution reactions involving chloride and dimethylamide ligands at dimolybdenum and ditungsten (M≡M) centers induced by added tertiary phosphines. Preparations and characterizations of W2Cl2(NMe2)4(Me2PCH 2PMe2), W2Cl3(NMe2)3(PMe2Ph) 2, and W2Cl4(NMe2)2(PMe2Ph) 2. Tertiary phosphines react with M2Cl2(NMe2)4 (M≡M) compounds (M = Mo and W) in hydrocarbon solvents to give a variety of products depending upon the metal and the phosphine. The bidentate phosphines L-L (L-L = Me2PCH2PMe2 and Me2PCH2CH2PMe2) give isolable and kinetically stable 1:1 adducts: M2Cl2(NMe2)4(L-L). The monodentate phosphines L (L = PMe3 and PMe2Ph) induce ligand redistribution reactions to give M2Cl3(NMe2)3L2, M2Cl4(NMe2)2L2, and M2(NMe2)6 compounds. The compounds M2Cl4(NMe2)2L2, where M = Mo and L = PMe3 and PMe2Ph but not where M = W, were found to undergo reductive elimination (by way of β-hydrogen elimination from a NMe2 ligand) in the presence of added phosphine to give Mo2Cl4L4 (M-4M) compounds. The compounds M2Cl2(NMe2)4(L-L) and M2Cl4-n(NMe2)2+nL2, where n = 0 or 1, are formulated as compounds containing four-coordinate metal atoms united by M-M triple bonds. This has been verified by single-crystal X-ray diffraction studies for the compounds W2Cl3(NMe2)3(PMe2Ph) 2 (at -160°C, a = 11.909 (3) A?, b = 13.271 (4) A?, c = 11.551 (3) A?, α = 104.76 (1)°, β = 108.64 (1)°, γ = 71.09 (1)°, Z = 2, dcalcd = 1.916 g cm-3, and the space group is P1) and W2Cl4(NMe2)2(PMe2Ph) 2 (at -158°C, a = 17.624 (8) A?, b = 11.995 (5) A?, c = 14.397 (6) A?, β = 114.29 (3)°, Z = 4, dcalcd = 2.093 g cm-3, and the space group is P21/c). In both molecules the W-W distances, 2.33 (2) A? (averaged), and W-P distances, 2.53 (1) A? (averaged), are similar while the W-N distances are notably shorter when N is bonded to W atoms having two Cl ligands and one PMe2Ph ligand, 1.93 (1) A? (averaged), relative to W-N distances, 1.99 (1) A? (averaged), involving W atoms bonded to two NMe2, one Cl, and one PMe2Ph. In both compounds, the NMe2 ligands contain trigonal-planar nitrogen atoms and the W-NC2 units are aligned along with the W-W axis such that the nitrogen lone pairs may interact with the W dxy atomic orbital, the one d orbital not used in either the M≡M bond or the four M-L σ bonds. In a formal sense the W-N distance of 1.93 A? corresponds to a W-N double bond and the W-N distance of 1.99 A? to a W-N bond order of 1 1/2.
