- Mechanistic studies of the oxidative cleavage of the molybdenum-mercury bonds in [CpMo(CO)2(PPh3)]2Hg
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Chemical or electrochemical oxidation of the trimetallic complex [CpMo(CO)2(PPh3)]2Hg (Cp = η5-C5H5) occurs in two one-electron steps. The first electron transfer generates a transient cation which undergoes Mo-Hg bond cleavage to generate a 16-electron species, [CpMo(CO)2(PPh3)]+, and a mercury-centered radical, CpMo(CO)2(PPh3)Hg?. To account for the products, it is proposed that the radical dimerizes and then reacts with half of the available 16-electron cation to form an observable pentametallic intermediate. The second electron transfer generates [CpMo(CO)2(PPh3)Hg]+ and returns the 0.5 mol of [CpMo(CO)2(PPh3)]+ which was incorporated into the intermediate. The mercury-containing cation subsequently eliminates metallic mercury to yield a second mole of [CpMo(CO)2(PPh3)]+. The 16-electron cation coordinates solvent or other available neutral or anionic ligands to yield 18-electron complexes.
- Lin, Chen C.,Gipson, Stephen L.
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p. 167 - 172
(2008/10/08)
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- Preparation and reactivity of an organometallic Lewis acid bearing two accessible coordination sites
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Treatment of the η3-allyl complex Cp(CO)2Mo(CH2CHCH2) with 1 equiv of HBF4 generates the η2-propene compound Cp(CO)2Mo(CH2=CHCH3)(FBF3) (7), a covalent molecule containing ligated propene and FBF3-, as a rapidly equilibrating mixture (on the NMR time scale) of cis and trans isomers. Carbonylation (1 atm) of 7 thus gives the propene salt Cp(CO)3Mo(CH2= CHCH3)+BF4-. Of more importance, 7 functions as a labile precursor to the formally 14-electron (or doubly unsaturated) Lewis acid Cp(CO)2Mo+. For example, both latent coordination sites on 7 are available for selectively forming the disubstituted derivatives Cp(CO)2Mo(PPh3)2+ and (Cp(CO)2MoI)2 upon treatment with PPh3 and I-, respectively, under mild conditions. The corresponding Lewis acid Cp(CO)3MoFBF3 (1a) with only one latent coordination site (ligated FBF3-), in contrast, gives only the monosubstituted derivatives Cp(CO)3Mo(PPh3)+ and Cp(CO)3MoI under comparable reaction conditions. A study was also instituted to see if the Lewis acids 7 and 1a convert Cp(CO)3MoCH3 and Cp(CO)3MoH to their bimetallic and symmetric μ-(η2-C,O)-acyl complexes [Cp(CO)2Mo]2(COR)+, where R = CH3 and H, respectively. [Note that using 7 instead of 1a now entails a net conservation of CO ligands in the formal Lewis acid promoted alkyl (or hydride) migration.] Reaction between 7 and Cp(CO)3MoCH3 indeed gives the known μ-(η2-C,O)-acetyl compound (42% yield vs. 36% from 1a), whereas 7 and Cp(CO)3MoH afford no discernible reaction products.
- Markham,Menard,Cutler
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p. 1581 - 1587
(2008/10/08)
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- Organometallic Lewis Acids, V. Reactions of Carbonyl-η5-cyclopentadienyl Molybdenum Tetrafluoroborates (η5-C5H5)Mo(CO)2(L)FBF3 (L = CO, PR3) with Phosphanes and Alkenes
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Tetrafluoroborate complexes (η5-C5H5)(Mo(CO)2(PR3)FBF3 have been prepared by hydride abstraction from the corresponding hydrido compounds using Ph3CBF4.The tetrafluoroborate ligand in (η5-C5H5)Mo(CO)2(L)FBF3 (L = CO, PR3) is easily substituted by phosphanes, cis- and trans-butene(2), α-acetamidocinnamic acid and butadiene.Nucleophilic addition of HNMe2 to the butadiene complex 5-C5H5)Mo(CO)3butadiene)>(+)BF4(-) gives the β-aminoacyl chelate compound 7. - Keywords: Carbonyl-η5-Cyclopentadienyl Molybdenum Complexes, Tetrafluoroborate Complexes, Cationic Organometallic Lewis Acids
- Suenkel, Karlheinz,Ernst, Herbert,Beck, Wolfgang
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p. 474 - 481
(2007/10/02)
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- METALLORGANISCHE LEWIS-SAEUREN; METALLKOMPLEXE MIT SCHWACH KOORDINIERTEN LIGANDEN. VIII. REAKTIONEN VON TETRAFLUOROBORATO-KOMPLEXEN (η5-C5H5)(CO)2(L)(MoFBF3 (L = CO, PR3) MIT ALKINEN
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The reaction of the tetrafluoroborato compounds (η5-C5H5)(CO)2(L)MoFBF3 with various alkynes gives mono- and bis-alkyne complexes 5-C5H5)Mo(CO)(RCCR')2>+ BF4- (III) and 5-C5H5)Mo(CO)(L)(RCCR')>
- Suenkel, Karlheinz,Nagel, Ulrich,Beck, Wolfgang
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p. 251 - 262
(2007/10/02)
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