The tetradecaisopropoxydihydridotetratungsten story

Akiyama, Morito; Chisholm, M. H.; Cotton, F. Albert; Extine, M. W.; Haitko, D. A.; Leonelli, J.; Little, Dustin J.

doi:10.1021/ja00394a009

Cited by 47 publications

(12 citation statements)

References 10 publications

(15 reference statements)

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“….747 (2), W(3)-W(4) = 2.795 (2) , W(l)-C(55) = 1.914 ( 14), W(2)-C(55) = 1.956 (15), W(3)-C(55) The W4CN012 skeleton of I is shown in Figure 1. The molecule bears a striking resemblance to the well-known "ironbutterfly" Fe4(g-C)(CO)13.7 If, for the sake of electron counting, charge is partitioned between the metal atoms and the ligands as C4-, NMe2-, and OR-, then the tetranuclear center is formally W418+ having only 6 electrons for M-M cluster bonding.…”

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confidence: 99%

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Tetranuclear carbidotungsten and nitridomolybdenum clusters supported by alkoxide ligands: W4(C)(OCHMe2)12(NMe) and Mo4(N)2(OCHMe2)12

Chisholm¹,

Folting²,

Huffman³

et al. 1985

J. Am. Chem. Soc.

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confidence: 99%

“…By changing the stoichiometry to that shown in eq 2, II may be 2) isolated in ca. 60% yield based on Mo after recrystallization from hot hexane.…”

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confidence: 99%

Tetranuclear carbidotungsten and nitridomolybdenum clusters supported by alkoxide ligands: W4(C)(OCHMe2)12(NMe) and Mo4(N)2(OCHMe2)12

Chisholm¹,

Folting²,

Huffman³

et al. 1985

J. Am. Chem. Soc.

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“…70.8 ( 7) 73.4 (11) C( 6) W( 1) 0(8) 82.7 ( 4) 86.6 (6) W(l) 0( 8) 0( 7) 73.3 (8) 70.6 (11) C( 7) W( 1) 0( 8) 35.9 (5) 36.0 (6) C( 8) 0( 7) 0(37) 133.3 (17) 0( 17) W( 2) 0( 21) 87.3 (3) 93.0 ( 5) C( 7) 0( 8) C( 38) 139.0 (17) 0( 17) W( 2) 0( 25 C-C-C angles of the alkyne ligand are in the range 133-139°, quite markedly bent from linearity. The acetylenic C-C distance, 1.28 Á, while significantly longer than in a typical free alkyne, 1.21 A, are not nearly lengthened as much as the µ-€2 2 alkynes discussed previously.1,2 (4) The terminal W-OR distances, which fall within the range 1.90-1.93 A, are typical of W-O distances having some rr-character7 while the distances to the bridging OR ligand, 0 (17), are longer and asymmetric with the W(2)-0 (17) distances being more than 0.1 A shorter than the W(l)-0(17)…”

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confidence: 85%

“…This, together Table I. Fractional Coordinates and Isotropic Thermal Parameters for the W2(0-i-Pr)6(C4H4)(C2H2) Molecule" atom 4* W4y 104z 105iso, A2 W(l) 7465.5 (3) 683.6 (4) (1) 12 W(2) 7678.3 (3) C( 15) 7114 ( 9) 3666 (11) (15) 24 C( 16) 5947 ( 8) 4290 (11) (15) 23 0 (17) 8459 (5) -862 (7) (9) 14 C( 18) 9387 25 " Isotropic values for those atoms refined anistropically are calculated by using the formula given by: Hamilton, W. C. Acta Crystallogr. 1959, 12, 609. with NMR spectra, show that the p-C4 ligand is formed by a simple coupling of C-C bonds.…”

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confidence: 99%

Metal alkoxides models for metal oxides. 5. Coupling of alkyne ligands in reactions involving ditungsten hexaalkoxides: an alternative to the metathesis reaction M.tplbond.M + C.tplbond.C- .fwdarw. 2M.tplbond.C

Chisholm¹,

Hoffman²,

Huffman³

1984

J. Am. Chem. Soc.

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W2(0-Z-Bu)6 and W2(OR)6(py)2, where R = z'-Pr or CH2-z-Bu, react in hydrocarbon solvents at ambient temperatures with ethyne (>3 equiv) to give the compounds W2(0-Z-Bu)6(/i-C4H4) and W2(OR)6(g-C4H4)(C2H2), respectively. The same compounds are produced from reactions involving the ethyne adducts W2(0-r-Bu)6(py)(ju-C2H2) and W2(0-z'-Pr)6^-C2H2)(py)2 and ethyne, and an intermediate W2(OCH2-Z-Bu)6(M-C4H4)(py) has been isolated and shown to be isomorphous and isostructural with its previously characterized molybdenum analogue. The nature of the C-C coupling has been investigated by using the labeled ethynes 13C2H2 and 12C2D2 and found to occur without C-C or C-H rupture. Analogous reactions employing MeC^CMe lead to the alkylidyne complex (z-BuO)3W=CMe or W2(OR)6(^-C4Me4)(C2Me2) compounds, where R = z'-Pr and CH2-z-Bu. These new compounds provide models for the cyclotrimerization and/or polymerization of alkynes at a dimetal center, though the elimination of the hydrocarbon fragment does not readily occur from the ditunsten center. These observations are contrasted with earlier findings in the chemistry of Mo2(OR)6 compounds. Single-crystal X-ray studies reveal the connectivity (RO)3W(m-íj*,i;4-C4R,4)(OR)W(OR)2 (tz2-C2R,2) for the compounds where R = z'-Pr and R' = H and Me. One tungsten atom is in a distorted octahedral environment being coordinated to three terminal OR ligands, a bridging OR ligand, and forming two W-C a bonds (W-C = 2.13 (2) Á, averaged) to the g-C4R'4 ligand. This tungsten atom lies in a plane with the four carbon atoms of the m-C4 ligand. The other tungsten atom is coordinated to one bridging and two terminal OR ligands, the ?j2-alkyne (W-C = 2.07 (2) A, averaged, and with C-C-C angle =136 (3)°, averaged) and the four carbon atoms of the

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“…W H (u-H) 2 (0-i-Pr) llt (30) is one of the very few transition metal hydrido alkoxides that have been claimed in the litera ture (58,59).…”

Section: Cffisholmmentioning

confidence: 99%

Metal Alkoxides: Models for Metal Oxides

Chisholm¹

1983

ACS Symposium Series

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In the spirit of this symposium, I should like to invite discussion of my proposal that metal alkoxides (1) may act as models for metal oxides in their reactions with a wide variety of hydrocarbons and small unsaturated molecules. Since metal oxides provide the most versatile class of heterogeneous catal ysts used in the petrochemical industry, studies of metal alkoxides, which are hydrocarbon soluble, could shed light on metal oxide catalyzed reactions and furthermore might yield a new generation of homogeneous catalysts. The fact that metal oxide catalysts are effective for reactions such as olefin -hydrogenation, -isomerization, -polymerization and -metathesis implies that metal-hydrogen and metal-carbon bonds are involved, perhaps in an analogous manner to those which are well documented in organometallic chemistry (2). This by itself is an interesting thought since metal oxides seem far removed from the now classical organometallic compounds which abound with ligands such as tertiary phosphines, carbonyls, π-bonded eyelopentadienes and arenes, etc. How can a metal-oxide environ ment compete with the sophisticated ligand systems that the contemporary organometallic chemist has available for catalyst design? Apparently, metal-oxide systems compete very effective ly and certainly in some instances there are no known homoge neous analogues. One can think of CO/H 2 activation in FischerTropsch chemistry as just one system in which the metal oxide catalysts win hands down over homogeneous metal-carbonyl chemis try Ο ). Let us speculate what special requirements a metal oxide environment or surface may provide. Factors which come to my mind include (i) unusual coordination numbers, geometries and electronic configurations for metal atoms; (ii) oxo ligands are strong π-donors, which contrast with most ligands commonly used in organometallic chemistry which are ιτ-acceptors; (iii) oxo ligands may act as terminal six-electron (M=0) or four-elec tron (M=0) ligands (4) or may act as bridging (μ 2 -> U3~> VU -, μ 5 -and μ 6 -) ligands and changes from one form to another may readily occur in response to the addition or elimination of

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The tetradecaisopropoxydihydridotetratungsten story

Cited by 47 publications

References 10 publications

Tetranuclear carbidotungsten and nitridomolybdenum clusters supported by alkoxide ligands: W4(C)(OCHMe2)12(NMe) and Mo4(N)2(OCHMe2)12

Tetranuclear carbidotungsten and nitridomolybdenum clusters supported by alkoxide ligands: W4(C)(OCHMe2)12(NMe) and Mo4(N)2(OCHMe2)12

Metal alkoxides models for metal oxides. 5. Coupling of alkyne ligands in reactions involving ditungsten hexaalkoxides: an alternative to the metathesis reaction M.tplbond.M + C.tplbond.C- .fwdarw. 2M.tplbond.C

Metal Alkoxides: Models for Metal Oxides

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