Browsing by Author "He, C."

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    A stable aluminacyclopropene LA1(eta(2)-C2H2) and its end-on azide insertion to an aluminaazacyclobutene
    (Wiley-v C H Verlag Gmbh, 2005)
    Zhu, H. P.
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    Chai, J. F.
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    Fan, H. J.
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    Roesky, H. W.  
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    He, C.
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    Jancik, V.  
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    Schmidt, H. G.
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    Noltemeyer, M.
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    Merrill, W. A.
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    Power, P. R.
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    Collective Modes and Structural Modulation in Ni-Mn-Ga(Co) Martensite Thin Films Probed by Femtosecond Spectroscopy and Scanning Tunneling Microscopy
    (Amer Physical Soc, 2015)
    Schubert, M.
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    Schaefer, H.
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    Mayer, J.
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    Laptev, Aleksej
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    Hettich, M.
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    Merklein, M.
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    He, C.
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    Rummel, C.
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    Ristow, O.
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    Grossmann, Marius  
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    Luo, Y.
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    Gusev, V.
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    Samwer, Konrad H.  
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    Fonin, M.
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    Dekorsy, T.
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    Demsar, J.
    The origin of the martensitic transition in the magnetic shape memory alloy Ni-Mn-Ga has been widely discussed. While several studies suggest it is electronically driven, the adaptive martensite model reproduced the peculiar nonharmonic lattice modulation. We used femtosecond spectroscopy to probe the temperature and doping dependence of collective modes, and scanning tunneling microscopy revealed the corresponding static modulations. We show that the martensitic phase can be described by a complex charge-density wave tuned by magnetic ordering and strong electron-lattice coupling.
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    Stepwise hydrolysis of aluminum chloride iodide LAlClI (L = HC[(CMe)(NAr)](2), Ar=2,6-iPr(2)C(6)H(3)) in the presence of N-heterocyclic carbene as hydrogen halide acceptor
    (Amer Chemical Soc, 2005)
    Zhu, H. P.
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    Chai, J. F.
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    He, C.
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    Bai, G. C.
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    Roesky, H. W.  
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    Jancik, V.  
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    Schmidt, H. G.
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    Noltemeyer, M.
    The aluminum chloride iodide LAlClI (2, L = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(6)H(3)) has been synthesized to study the stepwise hydrolysis of this compound in the presence of 1,3diisopropyl-4,5-dimethylimidazol-2-ylidene as hydrogen halide acceptor. The isolation and characterization of the aluminum chloride hydroxide [LAlCl(mu-OH)](2) (3) and the dihydroxide LAl(OH)(2) (4) demonstrate the realization of a controlled hydrolysis.
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    Synthesis of a new class of compounds containing a Ln-O-Al arrangement and their reactions and catalytic properties
    (Amer Chemical Soc, 2005)
    Chai, J. F.
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    Jancik, V.  
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    Singh, S.
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    Zhu, H. P.
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    He, C.
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    Roesky, H. W.  
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    Schmidt, H. G.
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    Noltemeyer, M.
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    Hosmane, Narayan S.
    Synthesis of a new class of compounds containing a Ln-O-Al moiety has been accomplished by the reaction of LAIOH(Me) (L = HC(CMeNAr)(2), Ar = 2,6-iPr(2)C(6)H(3)) with a series of CP(3)Ln compounds. The terminal Al-OH group shows selective reactivity, and the complexes CP(2)Ln(THF)-O-AlL(Me) (Ln = Yb, 1; Er, 2; Dy, 3), CP2Yb-O-AlL(Me) (4), and CP(3)Ln(mu-OH)AIL(Me) (Ln = Er, 5; Dy, 6; Sm, 7) were obtained. This allows further insight into the proton exchange process, and two different mechanisms, intermolecular and intramolecular elimination of CpH, are proposed under different conditions. Complexes 1-4, 6, and 7 have been characterized by X-ray structural analyses which reveals a Ln-O-Al or Ln(mu-OH)AI core in these complexes. The obtuse Ln-O-Al angles fall in the range 151.9-169.8 degrees. The reaction of 1 or 4 with Me3SnF in toluene under refluxing conditions unexpectedly yielded the compounds [CP2Yb(mu-OSnMe3)](2) (8) and LAI(Me)F (9). Reactions of LAIOH(Me) with the mono- and dicyclopentaclienyl complexes LYbCp(CI) (10) and LYbCp2 (11) Supported by the bulky beta-diketiminate ligand were unsuccessful. However, the reaction of LAI(OH)Me with LYbN(SiMe3)(2)Cl (12) containing a labile Yb-N bond leads to the formation of LYbCl-O-AIL(Me) (13) under elimination of HN(SiMe3)(2). Furthermore, complexes 1, 3, 4, and 6 exhibit good catalytic activity for the polymerization of c-caprolactone.
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    Synthesis, characterization, and hydrolysis of aluminum(III) compounds bearing the C6F5-substituted beta-diketiminate HC[(CMe)(NC6F5)](2) (L) ligand
    (Amer Chemical Soc, 2006)
    Yang, Z.
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    Zhu, H. P.
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    Ma, X. L.
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    Chai, J. F.
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    Roesky, H. W.  
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    He, C.
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    Magull, Joerg  
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    Schmidt, H. G.
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    Noltemeyer, M.
    A series of Al(III) compounds containing the C6F5-substituted beta-diketiminate ligands LAlMeCl (2), LAlMe2 (3), LAlMel (4), and LAlBr2 (5) (L = HC[(CMe)(NC6F5)](2)) were synthesized and characterized. The hydrolysis of 2 and 4 in the presence of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene as the hydrogen halide acceptor both lead to (LAIMe)(2)(mu-O) (6), a methylalumoxane derivative, which is the first hydrolysis product with the general formula of (RAIMe)nO. A comparison of the hydrolysis products of 2 and 4 with that of L'AIMeCl (L' = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(7)H(3)) shows that with the C6F5-substituted beta-diketiminate ligand, it was not possible to generate LAIMe(OH). This is obviously due to the stronger Bronsted acidity of the proton and the smaller size of the C6F5 group in this compound compared to that of the corresponding 2,6-iPr(2)C(6)H(3) derivative.
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    Synthesis, structure, and reactivity of beta-diketiminate complexes of manganese(II)
    (2004)
    Chai, J. F.
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    Zhu, H. P.
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    Roesky, H. W.  
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    He, C.
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    Schmidt, H. G.
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    Noltemeyer, M.
    Reaction of the beta-diketiminate lithium salt LLi(OEt2) (1) (L = HC(CMeNAr)(2), Ar = 2,6-iPr(2)C(6)H(3)) with MnCl2 in diethyl ether provided the metalate complex LMn(mu-Cl)(2)Li(OEt2)2 (3) in high yield. The dimeric compound [LMn(mu-Cl)](2) (4) free of alkaline salt was obtained when the beta-diketiminate potassium salt LK (2) was used instead of 1. The substitution reactions of 4 with CpNa, MeLi, and PhLi resulted in the formation of organomanganese complexes LMnCp(THF) (7), [LMn(mu-Me)](2) (8), and LMnPh (9), respectively. The novel ionic compound [LMnCl2] [{C(Me)N(iPr)}(2)CH] (6) was obtained, when the N-heterocyclic carbene {C(Me)N(iPr)}(2)C was used as a proton acceptor. The first doubly carboxylato-bridged complex with four-coordinate manganese(II), [LMn(mu-O2CMe)](2z) (5), was synthesized from the reaction of 2 and Mn(O2CMe)(2) in THF. Complexes 3-7 were characterized by single-crystal X-ray structural analysis. The structures show that the beta-diketiminate ligand backbone is essentially planar and the metal centers reside in distorted tetrahedral geometry.