- Synthesis and thermolysis of neutral metal formyl complexes of molybdenum, tungsten, manganese, and rhenium
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The possible intermediacy of catalyst-bound formyls in syngas transformations has prompted efforts to prepare and study the chemistry of transition-metal formyl complexes over more than a decade. We have used a mild borohydride in our reactions with metal carbonyl cations and have introduced some variations into the syntheses which allow, in almost all cases, for the pure formyl complex to be precipitated from solution as it is formed. The formyl complexes and their cationic precursors are shown. Seven of the formyls are new; improved procedures have been established for the other four. All but one of the compounds have been isolated.
- Gibson,Owens,Mandal,Sattich,Franco
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p. 498 - 505
(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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- 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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