Molybdenum tricarbonyls

In recent work, Ashe et al. have prepared a series of molybdenum tricarbonyl complexes of C6H6B-R ligands.142 X-ray diffraction data on [H6C6B-N(CHMe2)2]Mo(CO)3 123 revealed that the metal is coordinated to the six ring carbons but not to boron. 

Few examples have been reported of metals coordinated to six-membered boron-sulfur heterocycles. Ashe et al. prepared 4-methyl-l,4-thiaborin (SC4H4BMe) which forms a stable molybdenum tricarbonyl sandwich complex 144.158 jn g etjert s laboratory, the reaction of the diborolyl complex 33 (Section 3.01.3.2) with COS afforded the dinuclear complex 145 whose structure was determined crystallographically.36 Other products, not involving boron-sulfur heterocycles and hence outside the scope of this discussion, were obtained via the treatment of 33 with different sulfur reagents such as CS2.36... 

S. P. Nolan, C. D. Hoff. The Heats of Reaction of Phosphines with Toluene-Molybdenum Tricarbonyl. Importance of Both Steric and Electronic Factors in Determining the Mo-Plf Bond Strength. J. Organometal. Chem. 1985, 290, 365-373. 

Similarly, acetylene itself gave ferrocene. Cyclopentadienyl(methyl)molybdenum tricarbonyl reacted with diphenylacetylene to produce some tetraphenylcyclopentadiene. The corresponding ethylmolybdenum derivative gave some tetraphenyl-methylcyclopentadiene. The cyclizations involved in these reactions and the trimethylchromium reaction above are quite unusual and certainly deserve further study. 

In the course of a study of the formation of fluorophosphoranes from chloro-phosphines (22) we observed one exception in the compound chloromethyldi-chlorophosphine, which reacted smoothly with antimony trifluoride to give the flammable fluorophosphine, C1CH2PF2, under conditions where many other chloro-phosphines were invariably converted into fluorophosphoranes. As this fluorophosphine is readily available, its interaction with a metal carbonyl derivative was studied, and cycloheptatriene molybdenum tricarbonyl, obtained from the reaction of molybdenum hexacarbonyl with cycloheptatriene (I, 2), was chosen as a starting compound. 

In an inert atmosphere, excess chloromethyldifluorophosphine was distilled on cycloheptatriene molybdenum tricarbonyl, and the hydrocarbon ligand was readily displaced in a mildly exothermic reaction, requiring a reaction time of as little as 20 to 30 minutes. A high boiling colorless liquid (b.p. 127° at 0.05 mm.) was isolated by distillation, which could be shown to be the expected molybdenum tricarbonyl derivative, formed according to ... 

The tris(chloromethyldifluorophosphine)molybdenum tricarbonyl exhibited strong CO absorptions typical for terminal CO groups at 2038 and 1970 cm.-1. Strong P-F absorptions were found at 866 and 842 cm.-1, which in view of the above-mentioned observation in the case of tetrakis(trifluorophosphine)nickel-(0) may also be representative ef the uncoordinated fluorophosphine. Compared with molybdenum tricarbonyl derivatives with nitrogen compounds as donor mole-... 

In this latter reaction, the iridiabenzene complex cleanly displaces the para-xylene ligand so as to form complex 68, in which the iridiabenzene acts as if it were a normal pMigand coordinated to the molybdenum tricarbonyl moiety. 

BF4MoOPCwH](), Molybdenum(l +), car-bonyl-(-n5-cyclopentadienyl)-(diphenylacetylene)-(triphenylphosphine)-tetrafluoroborate(l -), 26 104 BF4MoO2PC25H20, Molybdenum, dicarbonyl-(T) -cyclopentadienyl)-[tetrafluoroborato(l -)] (triphenylphosphine)-, 26 98 BF4MoOjCbH5, Molybdenum, tricarbonyl-(ry -cyclopentadienyl) [tetrafluorobor-ato (1-)]-, 26 96... 

MoBFjO,C5H, Molybdenum, tricarbonyl-( ty -cyclopen tadienyl) [ te trafluoro-borato(l —)]-, 26 96... 

A number of readily reversible cr-7r rearrangements have been observed wherein a labile ligand such as carbon monoxide is lost by pyrolysis or photolysis, producing a coordinatively unsaturated metal center, which then regains coordinative saturation by means of a tr-n rearrangement. For example, irradiation of o--alkyl-7r-cyclopentadienyl-molybdenum tricarbonyl (15) produces the rr-allene complex (16) (25). These... 

While arsabenzene does not act as a nucleophile toward hard acids, it does form a-Mo(CO)5 complex 57 on treatment with pyridine-Mo(CO) and boron trifluoride etherate100). Qualitatively complex 57 seems rather weak since on heating it is destroyed, forming small quantities of tc-Mo(CO)3complex 58 101). This rt-complex is more conveniently prepared directly from arsabenzene and Mo(CO)6 or from acid-catalyzed displacement from tris-(pyridine)molybdenum tricarbonyl. 

The molybdenum tricarbonyls, 44, 45 and 46, have been reported as being antibacterial with 45 and 46 being active against H. pylori [134] while oral administration of ALF-186, 47, prevents the induction of a gastric ulcer by the NSAID, indomethacin [209]. 

Richard followed the course of the reactions of Cr(CO)6 and Mo(CO)6 with hexamethylborazine by UV-vis spectroscopy but although he observed that the intensity of the absorption maximum of the hexacarbonyls at around 290 nm decreased and a new band at around 350 nm appeared, he was unable to identify the new product. Experiments with other starting materials such as norborna-diene chromium and molybdenum tetracarbonyl or tris(aniline) molybdenum tricarbonyl which readily react with arenes by ligand exchange, also failed. The key to success was to use tris(acetonitrile) chromium tricarbonyl as the precursor, which in dioxan under reduced pressure afforded the desired hexamethylborazine chromium tricarbonyl as a stable crystalline solid in 90% yield. This was the breakthrough and, after we had communicated the synthesis and spectroscopic data of the complex in the January issue 1967 of Angewandte Chemie, Richard finished his work and defended his Ph.D. thesis in June 1967. Six months before, in December 1966,1 defended my Habilitation thesis in front of the faculty and became Privatdozent (lecturer) on the 1st of January 1967. 

Apart from the di- and oligoolefm iron tricarbonyl complexes, which nowadays are frequently used in organic synthesis [71, 72], the chemistry of the readily accessible cyclohepatriene chromium and molybdenum tricarbonyls 2 and 3 was the focus of intense research efforts as well. Only a few months after the synthesis of 2 and 3 was published [58,59], both Hyp Dauben and Peter Pauson reported that these compounds react with triphenylmethyl tetrafluoro-borate in methylene chloride to give the tropylium complexes 4 and 5 in excellent yield (Scheme 7.1) [73, 74]. Later this method of hydride abstraction was also used for the preparation of the tropylium cation itself and subsequently led to the generation of several cationic rc-complexes of iron, manganese and cobalt [71, 72], The reactions of the cations of 4 and 5 with nucleophilic... 

Cool the Schlenk tube under argon down to -78°C (dry ice-isopropanol slush bath), and then admit the tube to a vacuum (c. 0.1 mmHg). Pump for 60 s, then admit argon gas and allow the apparatus to warm up to room temperature. Repeat this freeze-thaw process twice more. Heat the stirred mixture at 160°C under argon for 2 h. An abundant yellow precipitate of the molybdenum tricarbonyl complex develops. 

Reactions of B-Substituted Borepin Molybdenum Tricarbonyl Complexes 1045... 

As indicated in Section 14.20.3.4, borepins can react with organometallics to form complexes in which the borepin ring serves as an rf ligand to the metal. Thus, 1-methylborepin 15 reacted with tris(pyridine)molybdenum tricarbonyl to afford the corresponding molybdenum complex 16 as a red, air-sensitive oil, as in Equation (1) <19970M1884>. 

This is believed to occiu- by intercalation of the positively charged phenanthridinium iinit, and it is noted that this occurs 50 times more effectively at the electron-rich C and G bases than at the AT sites. Ligand 46 was prepared by reaction of the acid chloride form of the pendant 61) to the molybdenum tricarbonyl complex of cyclen (62). The monosubstituted cyclen was then reacted with 3 moles of (R)-or (S)-JV-(2-chloroethanoyl)-2-phenylethylamine (61). Quartemization was achieved by reaction of methyl iodide with the Eu(III) complex (61). 

CYCLOHEPTATRIENE see COYOOO CYCLOHEPTATRIENE (DOT) see COYOOO CYCLOHEPTATRIENE MOLYBDENUM TRICARBONYL see COYIOO CYCLOHEXAAN (DUTCH) see CPBOOO CYCLOHEXADIENEDIONE see QQS200... 

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