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Metal Reagents (metal + reagent)

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Chemistry100%

Selected Abstracts

Metal-Promoted Cage Rearrangements in the Tricarbollide Series: Conversion of Ligand Derivatives 7-L- nido -7,8,9-C3B8H10 (L = H3N, tBuH2N, Me2HN) into Neutral 8-R- nido -7,8,9-C3B8H11 (R = H2N, tBuHN, Me2N) Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2003
Bohumír Grüner
Abstract Deprotonation of the eleven-vertex tricarbaborane zwitterions 7-L- nido -7,8,9-C3B8H10 [1: L = H3N (1a), tBuH2N (1b), Me2HN (1c)], followed by reactions with metal reagents [FeI2, NiCl2, and Ni(C5H5)2] at higher temperatures and in situ acidification, led to the 7 , 8 rearrangement of the N -substituted cage carbon atom to yield a series of 8-amino-substituted derivatives of nido -7,8,9-C3B8H12. These were characterized as 8-R- nido -7,8,9-C3B8H11 [2: R = H2N (2a), tBuHN (2b), Me2N (2c)]. A possible rearrangement mechanism for their formation has been proposed. Deprotonation of compound 2a with proton sponge [PS = 1,8-bis(dimethylaminonaphthalene)] generated the [8- tBuHN- nido -7,8,9-C3B8H10], (2b,) anion, which can be reprotonated to give the original compound 2b and not the tautomeric zwitterion 8- tBuH2N- nido -7,8,9-C3B8H10 (3b). All compounds were characterized by high-field (11B and 1H) NMR and IR spectroscopy, and mass spectrometry. The molecular structures of the neutral carbaborane 2b and its salt PSH+2b,were determined by single-crystal X-ray diffraction analyses. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Mild and Efficient Allylation of Aldehydes by using Copper Fluorapatite as Catalyst

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2008
M. Lakshmi Kantam
Abstract A facile synthesis of homoallylic alcohols is achieved by the allylation of aldehydes with allylic metal reagents or allyl halides using copper fluorapatite (CuFAP) as catalyst under mild reaction conditions. A variety of aldehydes were converted to the corresponding homoallylic alchohols, demonstrating the versatility of the reaction. [source]

Organometallic chemistry on rhodaheteroborane clusters: reactions with bidentate phosphines and organotransition metal reagents,

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6-7 2003
Oleg Volkov
Abstract This article reviews our recent work on the reactions of the rhodaheteroboranes [8,8-(PPh3)2 - nido -8,7-RhSB9H10] (1) and [9,9-(PPh3)2 - nido -9,7,8-RhC2B8H11] (2), and their derivatives, with the bidentate phosphines, dppe [(CH2)2(PPh2)2], dppp [(CH2)3(PPh2)2], and dppm [CH2(PPh2)2], and also with organotransition metal reagents. Simple substitution of the two PPh3 ligands by a single bidentate phosphine takes place when a 1 : 1 molar ratio of base (dppe or dppp) to rhodathiaborane (1) is used. However, in the presence of an excess of dppe or dppp, products containing 1 or 2 mol of base are formed. These products include a bidentate ligand on the metal and a monodentate ligand on the cage. The displaced hydrogen atom from the cage has moved to the metal center. These bis(ligand) species are unstable with respect to the loss of dihydrogen, affording closo -11 vertex clusters with a pendent phosphine ligand on the cage. In concentrated solutions, the pendent phosphine attacks another cage to afford linked clusters. Under both sets of conditions, when dppm is used, only one product is observed. This species has two dppm ligands coordinated to the metal: one in a unidentate mode and the other bidentate. A similar product is obtained in the reaction of 2 with dppm, although the arrangement of the ligands on the metal in the product is different. Ligand exchange experiments on the dppm,thiaborane system lead to results that provide keys to the reaction pathways in some of these processes. The bis(dppm) derivatives of 1 and 2 are amenable to further derivatization. A second metal may be added, either as an exo -polyhedral atom in a nido cluster in which the metal is part of a bidentate ligand, in the case of 1 and 2, or in a closo cluster derivative of 1 in which the metal is bonded to a dangling PPh2 moiety. Thus, it was possible to add the metals iridium, rhodium or ruthenium to the cluster, in the case of 1 and ruthenium in the case of 2. However, the reaction of more electrophilic organotransition metal reagents, such as Wilkinson's catalyst, with the dppm derivative of 1 affords species resulting from removal of ligand rather than incorporation of metal, and the products shed light on the rearrangement processes in these systems. Copyright © 2003 John Wiley & Sons, Ltd. [source]

The Efficient Direct Synthesis of N,O-Acetal Compounds as Key Intermediates of Discorhabdin A: Oxidative Fragmentation Reaction of ,-Amino Acids or ,-Amino Alcohols by Using Hypervalent Iodine(III) Reagents

CHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2006
Yu Harayama
Abstract Hypervalent iodine(III) reagents are readily available, easy to handle, and have a low toxicity and similar reactivities to those of heavy metal reagents, and hence they are used for various oxidative reactions. The oxidative cleavage of alkynes or carbonyl compounds by using bis(trifluoroacetoxy)iodo(III) pentafluorobenzene (C6F5I(OCOCF3)2) has been reported.1 Herein, the efficient direct synthesis of N,O-acetal compounds as key intermediates of discorhabdin A, by the oxidative fragmentation reaction of ,-amino acids or ,-amino alcohols by using C6F5I(OCOCF3)2, is described. [source]