Synthesis and structural characterisation of a novel tris-methylene bridged compound (NO)(4)Fe2Se(mu-CH2)(3)

The tris-methylene bridged compound (NO)(4)Fe2Se(mu-CH2)(3) has been isolated. It has been characterised by IR and H-1, C-13, and Se-77 NMR spectroscopy. Its structure has been determined by single-crystal X-ray diffraction methods. The structure consists of a heavy atom triangle consisting of one Se and two Fe atoms. The Fe-Fe and the two Fe-Se edges are bridged by methylene groups. (C) 1997 Elsevier Science S.A

Synthesis and spectroscopic characterisation of closo-Ru-4(CO)(12)(mu(4),eta(2)-HC2Ph) and closo-Ru-4(CO)(9)(mu-CO)(2)(mu(4),eta(2)-HC2Ph)(mu(4)-Se). Crystal structure of closo-Ru-4(CO)(12)(mu(4),eta(2)-HC2Ph)

Reaction of the chalcogen stabilised butterfly cluster Fe-2(CO)(6){mu-SeC(H)=C(Ph)Se} with Ru-3(CO)(12) occurs under thermal conditions affording the clusters FeRu2(CO)(9)(mu-Se)(2) (2), closo-Ru-4(CO)(12)(mu(4) eta(2)-HC2Ph) (3) and closo-Ru-4(CO)(9)(mu-CO)(2)(mu(4),eta(2)-HC2Ph)(mu(4)-Se) (4) in 30%, 22% and 18% yield respectively. They were characterised by IR and H-1, C-13 and Se-77 NMR spectroscopy. Compound 3 was further characterised by X-ray methods: space group P2(1)/n, a = 20.138(4), b = 9.333(2), c = 26.219(6) Angstrom, beta = 97.43(2)degrees, Z = 8, rho(calc) = 2.291 gcm(-3). The structure was solved using direct methods and was refined to the final values of the residuals R = 0.0377 and R-w = 0.0455. The molecule consists of a butterfly arrangement of four ruthenium atoms with a quadruply bridged alkyne ligand. Compound 4 was characterised by comparison of its spectroscopic data with that of the analogous S-compound

Silsesquioxane models for silica surface silanol sites with adjacent siloxide functionalites and olefin polymerization catalysts thereof

Incompletely condensed silsesquioxanes of the type R7Si7O9(O {SiR'2O}n)OH (R = c-C5H9, c-C6H11; R' = Me, Ph; n = 1-4), contg. a siloxane ring of variable size and rigidity and a remaining silanol, are described. Compared with a truly isolated silanol [R7Si8O12(OH)], soln. and solid state FT-IR spectra of these compds. show a nOH shift of approx. 150 cm-1 to lower frequency, which suggests hydrogen bonding of the silanol with the internal siloxane ring. In agreement with this, the relative ion pair acidities of the silanols in THF, detd. by UV/Vis, were lowered by 0.8-1.2 compared with a truly isolated silanol. D. functional theory (DFT) calcns. on these systems confirm the presence of intramol. hydrogen bonding. Possible interaction of the silyl ether functionalities with Lewis acidic metal sites was studied for the neutral gallium-substituted systems and cationic titanium silsesquioxane complexes, models for an immobilized titanium olefin polymn. catalyst. The electron donating capability of the siloxide functionalities in 1, 6, and 7 is not sufficient to satisfy the electron deficiency of the corresponding gallium silsesquioxane species, which form dimeric structures with a bridging siloxide unit rather than Lewis base adducts with coordinated siloxide functionalities. Metalation of 1 and 4 with [Cp''Ti(CH2Ph)3] (Cp'' = h5-1,3-C5H3(SiMe3)2) in a 1:1 ratio afforded monomeric titanasilses-quioxanes. To probe the effect of the neighboring siloxane ring on the highly Lewis acidic titanium center, the catalytic activities of the corresponding cationic half-sandwich complexes were tested in 1-hexene polymn. Compared with the catalyst system based on the isolated silanol [(c-C5H9)7Si8O12OH], the presence of a neighboring siloxane ring causes considerable retardation of the polymn. process but also improves the stability of the catalyst. [on SciFinder (R)

Methyl aluminosilsesquioxanes, models for Lewis acidic silica- grafted methyl aluminum species

The hydroxysilsesquioxanes (c-C5H9)(7)Si8O12(OH) (I) and (c- C5H9)(7)Si7O9(OH)(2)OSiMePh2 (II) have been studied as model supports for silica-grafted aluminum alkyl species. Treatment of AlMe3 with I gave polymeric {[(c-C5H9)(7)Si8O13]AlMe2}(n) (1a), which is readily transformed into the corresponding monomeric pyridine adduct, [(c-C5H9)(7)Si8O13]AlMe2. PY (1b). When AlMe3 was reacted with II, noticeable amounts of the 2:1 product {[(c-C5H9)(7)Si7O11(OSiMePh2)](AlMe2)(2)}(2) (2) and the Bronsted acidic 1:2 product {[(c- C5H9)(7)Si7O11(OSiMePh2)](2)Al-}{H+} (III) were obtained besides the main product of the reaction, {[(c- C5H9)(7)Si7O11(OSiMePh2)]AlMe}(2) (3a-c). The main product is a mixture of three dimeric conformational isomers all with the aluminum methyls trans to each other. The difference of the conformers originates from the different orientation of the silsesquioxane ligands. Reaction of the Bronsted acid III with AlMe3 yielded the kinetic product [(c- C5H9)(7)Si7O11(OSiMePh2)](2)Al2Me2 (4). The kinetic and thermodynamic stability of the three conformeric methyl aluminosilsesquioxanes {[(c-C5H9)(7)Si7O11(OSiMePh2)]AlMe}(2) (3a-c) and their chemical isomer {[(c- C5H9)(7)Si7O11(OSiMePh2)(]2)Al2Me2 (4) has been investigated. Isomerization experiments showed that 3a isomerizes to 3b, which subsequently isomerizes to 3c, affording the thermodynamically most stable mixture with a 3a:3b:3c ratio of 1:4:4 after 400 h at 76 degreesC. Isomerization of 3a to 3b is considerably faster than from 3b to 3c. Direct conversion of 3a into 3c was not observed. Complex 4 slowly isomerizes into 3c, which consecutively isomerizes into the thermodynamic most stable isomeric mixture (1000 h at 76 degreesC, E-a = 117 kJ . mol(-1)). Treating Cp2ZrMe2 with the Bronsted acid III gave clean transfer of a silsesquioxane ligand to zirconium, yielding [(c-C5H9)(7)Si7O11(OSiMePh2)]ZrCP2 (5). The methyl aluminosilsesquioxanes 1a and 2-4 are not Lewis acidic enough to effectively abstract a substituent X from Cp2ZrX2 (X = Me, CH2Ph, Cl). Though, 3a-c and 4 definitely interact with Cp2ZrX2. Dependent on the substituent X, the zirconocene can accelerate the rate of isomerization over 2 orders of magnitude (3a, 1.5 h; 4, 8 h at 76 degreesC).. Surprisingly, complex 4 also reacts with the strongly Lewis acidic B(C6F5)(3). As soon as all 4 has been converted into 3a-c, the accelerating effect stops, which demonstrates that Lewis acids have no effect on the isomerization of 3a-c. Complexes 2, 3a, 3c, 4, and 5 have been structurally characterize

Mixed-chalcogenide, mixed-metal carbonyl clusters. Synthesis and characterization of Cp(2)Mo(2)Fe(2)(mu(4)-Te)(mu(3)-E')(CO)(6) (E,E'=Te; E=S,E'=Te; E,E'=S; E=S, E'=Se), Cp(2)Mo(2)Fe(2)(mu(3)-Te)(mu(3)-E)(CO)(7), and Cp(2)Mo(2)Fe(mu(3)-E)(CO)7 (E=S, TE)

Reflux of a benzene solution of Fe3STe(CO)(9) and Cp(2)Mo(2)(CO)(6) yielded the new cluster Cp(2)Mo(2)Fe(2)STe(CO)(7) (6) as the major product and the following clusters in smaller amounts: Cp(2)Mo(2)Fe(2)Te(3)(CO)(6) (1), Cp(2)Mo(2)Fe(2)STe(2)(CO)(6) (2), Cp(2)Mo(2)Fe(2)S(2)Te(CO)(6) (3), Cp(2)-Mo2FeTe(CO)(7) (4), Cp(2)Mo(2)FeS(CO)(7) (5), and Cp(2)Mo(2)Fe(2)Te(2)(CO)(7) (7). The new cluster 3 was formed in good yield when a benzene solution of 6 was refluxed with sulfur powder. Similarly, 2 was obtained when a benzene solution of 6 was refluxed with tellurium powder. A new cluster with three different chalcogen ligands, Cp(2)Mo(2)Fe(2)SSeTe(CO)(6) (8), was obtained when a benzene solution of 6 was refluxed in the presence of selenium powder. Structures of 1-4, 6, and 8 were established by crystallographic methods. The structures of 1-3 and 8 consist of Mo2Fe2 butterfly cores with a mu(4)-Te atom and two mu(3)-chalcogen atoms (1, Te and Te; 2, S and Te; 3, S and S; 8, S and Se) capping the two Mo2Fe faces. Each Mo atom has a Cp ligand, and each Fe atom has three terminally bonded carbonyl groups. The structure of 4 conists of a Mo2FeTe tetrahedron with each Mo possessing a Cp ligand and two terminally bonded carbonyl groups and the Fe atom having three terminal carbonyl groups attached to it. The structure of 6 consists of a Mo2Fe2 tetrahedron. One Mo2Fe face is capped by a mu(3)-S ligand and the other by a mu(3)-Te atom. The Fe-Fe bond is bridged by a carbonyl group; there are two terminally bonded carbonyl groups attached to each Fe atom. A semitriply bridging earbonyl group is attached to one Mo atom. The other Mo atom has one terminal carbonyl group. Each Mo atom has one Cp ligand attached to it

Diyne-bridged metal clusters: Synthesis and spectroscopic characterization of [(CO)(6)Fe2Se2{mu-HC=C(CCR)}M] (R=Me and Bu-n; M=Cp2Mo2(CO)4, Co-2(CO)(6), Ru-3(CO)(10) and Os-3(CO)(10)). Structural characterization of [(CO)(6)Fe2Se2{mu-HC=C((CCBu)-Bu-n)}Cp2Mo2(CO)(4)] and [(CO)(6)Fe2Se{mu-HC=C(CCMe)}Ru-3(CO)(10)]

Room temperature reaction of [(CO)(6)Fe-2{mu-SeC(H)=C(C=CR)Se}], with the dimetallic species, Cp2Mo2(CO)(4) and Co-2(CO)(8), afforded the adducts [(CO)(6)Fe2Se2(mu-HC=C(CCR)}Cp2Mo2(CO)(4)] (R = Me, 1; R = Bu-n, 2) and [(CO)(6)Fe2Se2{mu-HC=C(CCR))Co-2(CO)(6)] (R=Me, 3; R=Bu-n, 4) respectively. On reaction of Ru-3(CO)(10) (NCMe)(2) with [(CO)(6)Fe-2{mu-SeC(H)=C(C=CR)Se}], the new diyne-bridged mixed-metal clusters [(CO)(6)Fe2Se2{mu-HC=C(CCR)}Ru-3(CO)(10)] (R = Me, 5; R = Bu-n, 6) were obtained. Similarly, [(CO)(6)Fe2Se2{mu-HC=C((CCBu)-Bu-n)}Os-3(CO)(10)], 7, was isolated from the reaction of [(CO)(6)Fe-2{mu-SeC(H)=C(C=(CBu)-Bu-n)Se}] with Os-3(CO)(10)(NCMe)(2). Compounds 1-7 were characterized by IR and H-1, C-13 and Se-77 NMR spectroscopy. The structures of 2 and 5 were established by single crystal X-ray diffraction study. Both contain an Fe2Se2 butterfly core bridged by an HCC unit of the diyne HC=CC=CR across the two Se atoms. In 2, the substituted acetylenic moiety is transversely bridged to the Mo-Mo bond and in 5, it forms a mu(3)-//-eta(2) bridge to an Ru, triangular core

Synthesis and spectroscopic characterization of (CO)(6)Fe-2{mu-EC(H)=C(2-Th)E'} (E,E' = S, Se, Te; Th = C4H3S) - Structural characterization of (CO)(6)Fe-2{mu-SeC(H)=C(2-Th)Se}

Room temperature stirring of (CO)(6)Fe-2(mu-EE') with 2-thiopheneacetylene (2-ThC=CH) in methanol containing sodium acetate afforded the adducts (CO)(6)Fe-2{mu-EC(H)=C(2-Th)E'} (E = E', EE' = S (1), Se (2) and Te (3); E not equal E', EE' = SeS (4), STe (5), SeTe (6) and TeSe (7)). Compounds 1-7 have been characterized by IR and multinuclear (H-1, C-13, Se-77 and Te-125) NMR spectroscopy. The structure of (CO)(6)Fe-2{mu-SeC(H)=C(2-Th)Se} (2) has been established by single crystal X-ray diffraction methods. It crystallized in the triclinic space group with a = 7.771(2)Angstrom, b = 17.051(4)Angstrom, c = 20.981(5)Angstrom, alpha = 67.00(2)degrees, beta = 80.26(2)degrees, gamma = 88.67(2)degrees, V = 2520 Angstrom(3), Z = 6, D-calc = 2.159 g cm(-3). Full-matrix least squares refinement of 2 converged to R = 0.0635 and R-W = 0.0969. The structure consists of a tetrahedral butterfly core containing the thiopheneacetylene as a bridge between the two wingtip Se atoms, with three terminally bonded carbonyl groups on each Fe atom. (C) 1997 Elsevier Science S.A

Terminal platinum(II) phosphido complexes : synthesis, structure, and thermochemistry

A series of terminal Pt(II) phosphido complexes Pt(dppe)(Me)(PRR') (R = H; R' = Mes* (1), R' = Mes (2), R' = Ph (3), R' = Cy (4); R = R' = Mes (5); R = R' = Ph (6); R = R' = Cy (7); R = R' = Et (8); R = Ph, R' = i-Bu (9)) has been prepared by proton transfer from the appropriate phosphine to the methoxide ligand of Pt(dppe)(Me)(OMe) (10) (dppe = Ph2PCH2-CH2PPh2; Mes* = 2,4,6-(t-Bu)(3)C6H2; Mes = 2,4,6-Me3C6H2; Cy = cyclo-C6H11). Complexes 1 and 2 were also made by deprotonation of the cations [Pt(dppe)(Me)(PH2Ar)][BF4] (Ar = Mes* (13); Ar = Mes (14)). For comparison to 1, the arylthiolate and aryloxide complexes Pt(dppe)(Me)(EMes*) (E = S (11); E = O (12)) were also prepared from 10. NMR studies of the proton-transfer equilibria between Pt(dppe)(Me)(X), Pt(dppe)(Me)(Y), and the acids HY and HX (see Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw, J. E. J. Am. Chem. Sec. 1987, 109, 1444-1456 and Bryndza, H. E.; Domaille, P. J.; Tam, W.; Fong, L. K.; Paciello, R. A.; Bercaw, J. E. Polyhedron 1988, 7, 1441-1452) provide an approximate partial ranking of Pt-P bond strengths in this series: Pt-PHPh > Pt-PHMes > Pt-PHMes*; Pt-PPh2 > Pt-PMes(2). Complementary solution calorimetry investigations probe the role of entropic effects on the equilibria. Both steric and electronic factors appear to be important in controlling relative Pt-P bond strengths. The Pt-S bonds in 11 and Pt(dppe)(Me)(SPh) are stronger than the analogous Pt-P bonds in 1 and 3. Complexes 1 and 5.THF were structurally characterized by X-ray crystallography