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  • 1
    ISSN: 0947-6539
    Keywords: allyl complexes ; butadienes ; C-C coupling ; rhodium ; vinylidene complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the first part of this work, a general method for the preparation of aryl, methyl, vinyl and alkynyl(vinyl-idene)rhodium(I) complexes trans-[Rh(R')-(=C=CHR)(PiPr3)2] (8-14, 18-22) and trans-[Rh(R')(=C=CMe2)(PiPr3)2] (16, 17) from the corresponding chloro(vinyl-idene) derivatives and Grignard reagents is described. Whilst compounds 8 and 10-13 react with pyridine to give trans-[Rh(C≡CR)(py)(PiPr3)2] (23-25) by elimination of R'H, treatment of 8-11, 16, and 18 with carbon monoxide yields the square-planar η1-vinyl and η1-butadienylrhodiumcarbonyl complexes trans-[Rh{η1-(Z)-C(R')=CHR}(CO)(PiPr3)2] (27-32). The reaction of 8 or 18 with methyl or tert-butylisocyanide leads stereoselectively to the isocyaniderhodium(I) compounds trans- [Rh{η1-(Z)-C(R)=CHPh}(CNR') (PiPr3)2] (33-35). Acid-induced cleavage of the rhodium-carbon σ bond of 27, 30, or 31 with CH3CO2H gives trans-[Rh(η1-O2CCH3)-(CO)(PiPr3)2] (38) and the corresponding olefin or diene, respectively. In the absence of a Lewis base such as pyridine, CO, or CNR', compounds 18-20 rearrange in benzene at 40-50 °C to afford the isomeric π-allyl complexes [Rh(η3-1-RC3H4)(PiPr3)2] (40-42) almost quantitatively. The vinyl(vinylidene) compounds 11 and 12 also undergo an intramolecular rearrangement that leads to the η3-2,3,4-butadienyl- or to the alkynyl(ethene)rhodium(I) isomers, depending on the reaction conditions. In an analogous manner to the η1-vinyl-and η1-butadienyl(carbonyl) derivatives 27, 30, and 31, the π-allyl and π-butadienyl complexes also react with acetic acid to give [Rh(η1-O2CCH3)(PiPr3)2] (47) and the respective olefin.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0947-6539
    Keywords: carbene complexes ; C—C coupling ; diazo compounds ; ligand effects ; rhodium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A synthetic methodology to obtain square-planar carbenerhodium(I) complexes of the general composition trans-[RhCl(=CRR′)(L)2] where L is a tertiary phosphane, arsane, or stibane has been developed. The starting material trans-[RhCl(C2H4)(SbiPr3)2] (3) reacts with diazoalkanes RR′CN2 [RR′ = Ph2, Ph(C6H4X), (C6H4X)2, Ph(CF3), C12H8] under mild conditions to give the compounds trans-[RhCl(=CRR′)(SbiPr3)2] (4-11) almost quantitatively. On treatment of 3 with EtO2CCHN2 and PhC(N2)C(O)R, the olefinrhodium and diazoalkanerhodium compounds trans-[RhCl{(E)-C2H2(CO2Et)2}(SbiPr3)2] (12) and trans-[RhCl{N2C(R)C(O)Ph}(SbiPr3)2] (13, 14) are obtained instead of carbene complexes. Displacement of the SbiPr3 ligands in 4 (R = R′ = Ph) by PiPr3, PiPr2Ph, PiPrPh2, PPh3, PPh2Me, AsiPr3, and SbEt3 leads to the corresponding carbene complexes trans-[RhCl-(=CPh2)(L)2] (15-21) in high yields. The results of the X-ray crystal structure analyses of 4 and 15 (L = PiPr3) illustrate that the different donor - acceptor properties of SbiPr3 and PiPr3 have little influence on the Rh—C bond length. The reactions of 4 and 15 with CO and CNtBu afford, by metal-assisted C—C coupling, diphenylketene Ph2C=C=O (23) and the corresponding imine Ph2C=C=NtBu (26). On treatment of 4 and 15 with ethene, however, two different olefinic products, 3,3-diphenyl-1-propene (31) and 1,1-diphenyl-1-propene (32), are formed. Compound 15 reacts with KBr, NaOPh, and NaC5H5 by substitution of the chloride to give trans-[RhBr(=CPh2)-(PiPr3)2] (33), trans-[Rh(OPh)(=CPh2)-(PiPr3)2] (34) and [C5H5Rh(=CPh2)-(PiPr3)] (35), and with HCl by oxidative addition to yield [RhCl2(CHPh2)-(PiPr3)2](36).
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0947-6539
    Keywords: antimony ; arene complexes ; diene complexes ; rhodium ; ylides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first representatives of phosphino(stibino)methanes R2PCH2Sb-R′2 (3-5) with bulky alkyl or cycloalkyl groups R and R′ were prepared in two steps from Ph3SnCH2I via the isolated stannylated phosphanes Ph3SnCH2PR2 (1, 2) as intermediates. X-ray structural analysis of 5 (R = C6H11, R′ = tBu) reveals that the lone pairs and the substituents R and R′ at phosphorus and antimony and the hydrogen atoms of the CH2 bridge adopt staggered conformations. Treatment of [{C8H12RhCl}2] with 3-5 affords the neutral compounds [Rh-Cl(η4-C8H12)(κ-P-R2PCH2SbR′2)] (6-8), of which 7 and 8 react with CH3MgI to give the corresponding methylrhodium derivatives [RhCH3(η4-C8H12)(κ-P-R2-PCH2SbR′2)] (9, 10). Cationic complexes [Rh(η4-C8H12)(η2-P,Sb-R2PCH2SbR′2)]-X (X = PF6: 11a, 12a, 13; X = BPh4: 11b, 12b) containing the phosphino(stibino)methanes as chelating ligands were obtained either from [{C8H12RhCl}2], R2PCH2SbR′2 and MX, or (for 13) from 8 and AgPF6. Compound 12a (R = iPr, R′ = tBu) was characterized by X-ray crystallography. The PF6 salts 11a, 12a, and 13 react with CH2N2 by insertion of CH2 into the Rh-Sb bond to yield the complexes 14-16, the first examples of transition-metal compounds with Sb ylides as ligands. Treatment of BPh4 salts 11b and 12b with H2 gives the half-sand-wich-type complexes [(η6-C6H5BPh3)Rh(κ2-P,Sb-R2PCH2SbR′2)] (17, 18), in which the tetraphenylborate is coordinated like a substituted arene to the metal center.
    Additional Material: 2 Ill.
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