Molybdenum complexes alkylidyne

Alkyne Metathesis Using Molybdenum Alkylidyne Complex 304... 

Protonation of vinylidene and acetylide ligands was also found to be useful for the synthesis of high-oxidation state molybdenum alkylidyne complexes. Green and co-workers demonstrated protonation of the vinylidene complex 20 as shown in Eq. (21) (64). Selegue and co-workers... 

Treatment of the molybdenum alkylidyne complex 191 with 300 atm CO affords a mixture of three products the products of substitution of one and two phosphite ligands and complex 192 [Eq. (154)] (91). The methox-ycarbonyl group in 192 may have arisen from the reaction of an intermediate ketenyl ligand with methanol (derived from hydrolysis of trimethyl-phosphite). Reaction of the compounds 193 with xylylisocyanide was shown to give complexes 194 [Eq. (155)] (91). The products contain the... 

The transformation of reaction (t) forms the basis for metathesis of 3-heptyne " . Products of reaction (t) also catalyze metathesis of 3-heptyne. Related molybdenum-alkylidyne complexes similarly catalyze alkyne metathesis . 

The stoichiomeric reaction of another molybdenum alkylidyne complex 56 with 2-methylthiirane as the sulfur source yielded the thioacyl complex 57. A further reaction of 57 with Seg-LiBHEt3 furnished the selenothioate complex 58 in high yield (Scheme 5) [19]. 

Krouse, S.A., Schrock, R.R., and Cohen, R.E. (1989) Preparation of polycyclooctyne by ring-opening polymerization employing dO tungsten and molybdenum alkylidyne complexes. Macromolecules, 22, 2569-2576. 

Metallacumulenes with alkylidynes, 5, 458-459 in molybdenum carbonyl complexes, 5, 401 Metallacycles with bis-Gp Ti(IV), 4, 563 with nickel... 

R. R. Schrock, High-Oxidation-State Molybdenum and Tungsten Alkylidyne Complexes, Acc. Chem. Res. 19, 342-348 (1986). 

Molybdenum and tungsten carbyne (alkylidyne) complexes frequently undergo 2+2 cycloaddition reactions with alkynes to give the corresponding metallacyclobutadiene... 

NMR resonances of the alkylidyne carbon atom and selected IR absorptions for new carbyne complexes are given in Table 11. In other studies, the Mo and NMR spectra of molybdenum and tungsten alkylidyne complexes were determined by Enemark and co-workers (23). The metal atoms in the alkylidyne complexes were found to be less shielded than those in nitrido complexes but more shielded than those in compounds containing metal-metal multiple bonds. 

Metal alkylidyne complexes undergo a variety of oxidation and reduction reactions as well as redox-induced transformations of the alkylidyne ligands. A method for the direct transformation of Fischer-type carbyne complexes into Schrock-type alkylidyne complexes was developed in our laboratory. Bromine oxidation of the /ra/7, -carbyne bromo tetracarbonyl complexes 49 of molybdenum and tungsten in the presence of dimethox-yethane affords the dme-stabilized alkylidyne tribromo metal complexes 50 [Eq. (42)] (81). For alkyl-substituted complexes (R = Me, CH2CMe3)... 

Protonation of several molybdenum and tungsten alkylidyne complexes of the type M(CR)(f) -C5H5)(CO)L with acids such as HCI or CFjCOjH was reported by KreissI et al. to afford the / -acyl complexes 121 [Eq. (104)] (134). The formation of the acyl complexes I2I presumably in-... 

McCullough, L. G., Schrock, R. R. Multiple metal-carbon bonds. 34. Metathesis of acetylenes by molybdenum(VI) alkylidyne complexes. J. Am. Chem. Soc. 1984,106,4067 068. 

Molybdenum(Vl) complexes, 1256,1375-1414 alkyl, 1407 alkylidyne, 1407 alkylimido, 1396 arylimido, 1396 bipyridyldibromodioxo, 1388 bis(acetylacetonate) dioxo, 1388 catecholate dioxo, 1389 dimethyl, 1406 dinuclcar, 1408 IR spectroscopy, 1412 O or S bridge, 1411 preparation, 1411 Raman spectroscopy, 1412 single 0X0 bridge, 1408 structure, 1408 triple bridge, 1410 dioxo... 

Scheme 6 Formation of molybdenum complexes bearing ditbiocarboxylato ligands by sulfurization of tbe alkylidyne complexes...

Electrophilic addition to anionic molybdenum isocyanide derivatives [Na][Tp Mo(CNR)(CO)2] is dominated by direct attack at nitrogen to form alkylidyne products however, alkylation at the metal followed by isonitrile insertion can lead to j -iminoacyl complexes in some cases. The aminocarbyne products Tp Mo(=CNRMe)(CO)2 are formed in high yield for methyl and phenyl isocyanide reagents. However, the formation of the corresponding tcrt-butylamino-alkylidyne complex is accompanied by formation of f/ -acyl and / -iminoacyl complexes (Scheme 22). ... 

The metal-alkylidyne complex TpW( = CMe)(CO)2 reacts with Cp2Mo2(CO)4 or Mo(CO)3(NCMe)3 to afford the trimetal complexes Cp2TpMo2W(/t3-CMe)(CO)6 and Tp2MoW2(ia-CMe)2(ia-CO)2(CO)4, respectively (Scheme 75)." In the latter complex, one of the terminal carbonyl ligands of each tungsten centre is f/ -bound to the central molybdenum atom. 

Treatment of TpMo( = CR)(CO)2 (R = C6H4Me-4) initially gives a mixture of TpMoFe( U-CR)(CO) (k = 5, 6), but the saturated molybdenum complex readily loses CO under a nitrogen atmosphere." Parallel reaction between bis(pyrazolyl) borate alkylidyne complexes and Fe2(CO)g similarly provides the 32-valence electron dimetal species BpWFe( -CR)(CO)6." These heteronuclear bimetallic complexes have a rich further chemistry, as summarised in Scheme 78. 

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