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Various dicobalt hexacarbonyl acetylene complexes were efficiently converted to the unprotected acetylene by the reaction of two molar equivalents of sodium methylthiolate. Yields and reaction times depend upon the choice of solve...
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Various dicobalt hexacarbonyl acetylene complexes were efficiently converted to the unprotected acetylene by the reaction of two molar equivalents of sodium methylthiolate. Yields and reaction times depend upon the choice of solvent. DMF proved to be the most efficient solvent, with the reaction proceeding at >80% conversion in 5 minutes at room temperature. (C) 1999 Elsevier Science Ltd. All rights reserved. [References: 10]
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CoSi/sub 2/ is being used commonly for the advanced IC technologies. There are several process choices to be made for the formation of a high yielding and reproducible silicide. In this paper the various CoSi/sub 2/ technologies a...
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CoSi/sub 2/ is being used commonly for the advanced IC technologies. There are several process choices to be made for the formation of a high yielding and reproducible silicide. In this paper the various CoSi/sub 2/ technologies are discussed. The scalability of the process of record, the Co/Ti(cap) process are presented for 0.18 /spl mu/m and below.
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Lewis acid treatment of #gamma#-benzyl protected Cp_2(CO)_6-#alpha#,#gamma#-acetylenic diols yielded after cobalt demetallation bishomopropargylic alcohols in good yields.The method works with both primary and secondary benzyl eth...
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Lewis acid treatment of #gamma#-benzyl protected Cp_2(CO)_6-#alpha#,#gamma#-acetylenic diols yielded after cobalt demetallation bishomopropargylic alcohols in good yields.The method works with both primary and secondary benzyl ethers and is compatible with many kinds of protecting groups and functionalities.
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Alkyl transition metal reagents are being increasingly used for alkylations in organic synthesis. They have various advantages over alkyllithium and alkylmagnesium reagents including higher selectivity, lower basicity, and--as lon...
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Alkyl transition metal reagents are being increasingly used for alkylations in organic synthesis. They have various advantages over alkyllithium and alkylmagnesium reagents including higher selectivity, lower basicity, and--as long as the transition metal is not in its highest oxidation state-- their willingness to undergo oxidative addition with electrophiles. Alkyl derivatives of Fe~(II)and Co~(II), which are not stabilized by special ligands but still can be easily handled, are in many cases superior to the well-known alkyl-Cu~I and -Mn~(II) reagents and can also undergo unexpected reactions. The introduction of alkyl-cyanoate complexes of Fe~(II) and Co~(II), the cyanide ligands of which (in contrast to neutral pi-acidic ligands) do not reduce the reactivity, has led to further advances. Reaction mechanisms will be discussed and comparisons will be made with alkylating reagents containing Cu~, Mn~(II), Ni~(II), or Ti~(IV) as well as with Pd-catalyzed coupling reactions. Furthermore, it will beshown that super-ate Fe~(II) complexes are almost certainly the reactive species in highly selective catalytic alkylations.
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"Phosphaalkynes correspond to alkynes in all aspects, to nitriles in nothing." This remark by Regitz'11 is substantiated by the results of our investigations of the chemistry of [omega-phosphanyl(ethylcyclopentadienyl)]cobalt comp...
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"Phosphaalkynes correspond to alkynes in all aspects, to nitriles in nothing." This remark by Regitz'11 is substantiated by the results of our investigations of the chemistry of [omega-phosphanyl(ethylcyclopentadienyl)]cobalt complexes. Herein we report on reactions of such complexes with tert-butylphos-phaethyne that in addition to diphosphete complexes result in the formation of mu_3-phosphide clusters in good yields. The "naked" phosphorus ligand in these clusters can be oxidized with elemental sulfur or with oxygen in the air to give PS and PO ligands. respectively.
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The nonclassical structure 1 of boriranylideneboranes (the classical formulation is1 was predicted by Schleyer and others years before proof was provided by an X-ray structure determination of 1 a. Among the versatile reactions of...
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The nonclassical structure 1 of boriranylideneboranes (the classical formulation is1 was predicted by Schleyer and others years before proof was provided by an X-ray structure determination of 1 a. Among the versatile reactions of 1 b, c several occurwith cleavage of bonds in the three-membered ring and migration of substituents.
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A series of 12-vertexcloso-cobaltacarboranes 1,2-R?2-3-(C5R5)-3,1,2-CoC2B9H9(1a: R?=?R??=?H;1b: R?=?Me, R??=?H;2a: R?=?H, R??=?Me;2b: R?=?R??=?Me) were synthesized by reactions of the carbonyl cobalt complexes (C5R5)Co(CO)I2with T...
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A series of 12-vertexcloso-cobaltacarboranes 1,2-R?2-3-(C5R5)-3,1,2-CoC2B9H9(1a: R?=?R??=?H;1b: R?=?Me, R??=?H;2a: R?=?H, R??=?Me;2b: R?=?R??=?Me) were synthesized by reactions of the carbonyl cobalt complexes (C5R5)Co(CO)I2with Tl[Tl(η-7,8-R?2-7,8-C2B9H9)]. The reaction of CpCo(CO)I2with Tl[Tl(η-7,8-Me2-7,8-C2B9H9)] is accompanied by side formation of the novel charge-compensatednido-carborane 10-{CpCo(C5H4)}-7,8-Me2-7,8-nido-C2B9H9(3) in 19% yield. The structures of2a,band3were determined by X-ray diffraction.
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The dehydrotropylium-Co_2(CO)_6 ion was generated by the action of HBF4 or BF3·OEt2 on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The ...
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The dehydrotropylium-Co_2(CO)_6 ion was generated by the action of HBF4 or BF3·OEt2 on the corresponding cycloheptadienynol complex, which in turn has been prepared in four steps from a known diacetoxycycloheptenyne complex. The reaction of the cycloheptadienynol complex via the dehydrotropylium-Co_2(CO) _6 ion with several nucleophiles results in substitution reactions with reactive nucleophiles (N>1) under normal conditions, and a radical dimerisation reaction in the presence of less reactive nucleophiles. Competitive reactions of the cycloheptadienynol complex with an acyclic trienynol complex show no preference for generation of the dehydrotropylium-Co_2(CO) _6 ion over an acyclic cation. DFT studies on the dehydrotropylium- Co_2(CO)_6 ion, specifically evaluation of its harmonic oscillator model of aromaticity (HOMA) value (+0.95), its homodesmotic-reaction- based stabilisation energy (≈2.8 kcal mol~(-1)) and its NICS(1) value (-2.9), taken together with the experimental studies suggest that the dehydrotropylium-Co_2(CO)_6 ion is weakly aromatic.
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We have carefully studied the relation between the critical and electrical behavior of rhombohedral La1-xSrxCoO3 (x = 0.2-0.5) compounds prepared by solid-state reactions. The results obtained from analyzing M(T, H) data indicate ...
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We have carefully studied the relation between the critical and electrical behavior of rhombohedral La1-xSrxCoO3 (x = 0.2-0.5) compounds prepared by solid-state reactions. The results obtained from analyzing M(T, H) data indicate that all compounds undergo a second-order phase transition and the ferromagnetic-paramagnetic (FM-PM) transition temperature increases from approximate 182 K for x = 0.2 to 253 K for x = 0.5. Basing on the modified Arrott and Kouvel-Fisher techniques, scaling hypothesis, and critical isotherm analysis, we have determined the critical exponent values characteristic of magnetic order of La1-xSrxCoO3, with beta = 0.361-0.489, gamma = 1.021-1.346, and delta = 2.99-4.72. Interestingly, though all compounds are metallic ferromagnets, we have found the phase segregation in magnetic order as x > 0.3, where magnetic interactions tend to change from long-to-short-range FM order together with the absence of the insulating-like behavior at temperatures below 100 K. These phenomena are related to the spatial coexistence of multiple electronic and magnetic phases due to the changes in concentration of cobalt ions, spin-state transitions, and the existence of poor-hole anti-FM and hole-rich FM regions.
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The reduction of tungsten hexachloride with iron powder or cobalt powder resulted in the formation of MW_2Cl_(10) (M = Fe and Co) in fused silica tubes at 250 °C and 225 °C, respectively. Crystal structures of the new compounds ...
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The reduction of tungsten hexachloride with iron powder or cobalt powder resulted in the formation of MW_2Cl_(10) (M = Fe and Co) in fused silica tubes at 250 °C and 225 °C, respectively. Crystal structures of the new compounds were refined isotypically from X-ray powder diffraction patterns [C2/c, Z = 4, a = 6.1226(1) ?, b = 16.7943(1) ?, c = 12.3737(1) ?, and β = 108.99(1)° for FeW _2Cl_(10), and a = 6.111(1) ?, b = 16.696(1) ?, c = 12.384(1) ?, and β = 108.97(1)° for CoW_2Cl _(10)]. The structures of Fe_(1/5)W_(2/5)Cl_2 and Co_(1/5)W_(2/5)Cl_2 can be considered as a cation-deficient CdI_2-type structure, in which bioctahedral [W _2Cl_(10)]~(n-) anions with n ≈ 2 introduce significant distortions. The compounds MW_6Cl_(14) (M = Fe and Co) were prepared following the same procedure at 475 °C. Their crystal structures were refined isotypically [Pn3, Z = 4, a = 12.567(1) ? for FeW_6Cl_(14), and 12.525(1) ? for CoW _6Cl_(14)] to the structure of PbMo_6Cl_(14) from X-ray powder diffraction patterns.
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