Manganese carbonyl

The decomposition of Mn(CO)5Cl, Mn(CO)5Br and Mn(CO)sI in the presence of a wide variety of ligands [P(C6H5)3, As(C6H5)3, C5H5N, P(OC4H9)3, etc.] proceeds by the slow loss of CO followed by fast coupling with the ligand28, viz. 

For Mn(CO)5Br in nitrobenzene, k1 = 3.6x 107 exp(—30,900/RT) sec-1. The variation in k1 with solvent and the unusually high pre-exponential factors reflect the decrease in solvation on formation of the activated complex. 

A single value for the rate coefficient for loss of CO from Mn2(CO)10 has been obtained29. At 80 °C, k = 3.9 x 10 6 sec-1. Solvent effects should play only a minor role in this decomposition. Therefore, an assumed value for the preexponential factor of 1014 sec-1 is reasonable. This gives an activation energy of 31.4 kcal.mole-1 which is in accord with the values for Mn(CO)sX. 

The work cited in sections 2.4 and 2.5 is representative of the SN1 substitution reactions of metal carbonyls. However, a much more extensive and detailed account has recently been published covering similar reactions of vanadium, chromium, molybdenum, tungsten, rhenium, iron and nickel carbonyls in addition to those of manganese and cobalt2 9a. 

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In an attempt to formulate a new photoresistant and presensitized lithographic plate, Wagner and Purbrick [61] have used poly(vinyl trichloroacetate) and styrene, which together with manganese carbonyl or phenyl chro-... 

This reaction is used with different boron halides and manganese carbonyl derivates in 12 at RT to yield B—Mn compounds (Table 1). 

The Reaction of Manganese Carbonyl Halides with CNC H, and CNCH3 (Tetrahydrofuran) ... 

Methylcyclopentadienyl manganese tricarbonyl that has been suggested as a fuel additive is decomposed primarily by photolysis in aqueous medium. This resulted in the formation of methylcyclopentadiene that may plausibly be presumed to polymerize, and a manganese carbonyl that decomposed to Mn304 (Garrison et al. 1995). 

Group VIIA (Mn, Tc. Re). A number of mononuclear manganese carbonyl derivatives have been y- irradiated and examined by e.s.r. spectroscopy. The motivation behind much of this effort was the search for the elusive radical Mn(CO)s. The e.s.r. spectrum of this species is now firmly (35-37) established (Figure 4), although there is still some suggestion that the true "naked Mn(CO)s has yet to be observed (37). 

When propylene chemisorbs to form this symmetric allylic species, the double-bond frequency occurs at 1545 cm-1, a value 107 cm-1 lower than that found for gaseous propylene hence, by the usual criteria, the propylene is 7r-bonded to the surface. For such a surface ir-allyl there should be gross similarities to known ir-allyl complexes of transition metals. Data for allyl complexes of manganese carbonyls (SI) show that for the cr-allyl species the double-bond frequency occurs at about 1620 cm-1 formation of the x-allyl species causes a much larger double-bond frequency shift to 1505 cm-1. The shift observed for adsorbed propylene is far too large to involve a simple o--complex, but is somewhat less than that observed for transition metal r-allyls. Since simple -complexes show a correlation of bond strength to double-bond frequency shift, it seems reasonable to suppose that the smaller shift observed for surface x-allyls implies a weaker bonding than that found for transition metal complexes. 

The Mn atom has 25 electrons. Adding five carbonyl groups would raise the number to 35, leaving the atom one electron short of the krypton configuration. If the single unpaired electron on one manganese atom is then allowed to pair up with an unpaired electron on another to form a metal-metal bond, we have the formula (CO)5Mn-Mn(CO)5 or [Mn(CO)5]2, which is the formula for a manganese carbonyl that obeys the EAN rule. 

Herrmann and coworkers183 reported a series of Cp-manganese carbonyl complexes which bind Ge, Sn and Pb as central atoms linearly coordinated in clusters, to two Mn atoms in one series and trigonal-planar coordinated to three Mn atoms in another series 8 and 9. The group 14 atoms are double-bonded to two Mn atoms in these compounds, or carry one double bond and two single bonds to three Mn atoms. Potentiometric measurements of these compounds show irreversible reductions and oxidation by CV. No products could be isolated from either reduction or oxidation. The exceptionally high oxidation potential of (/i-Pb) r/ -CsHs )Mn(CO)2]2 as compared to the apparently similar Sn compound is noteworthy (Table 15). 

As in the case of chromium and tungsten, manganese carbonyl adducts of Me2SO have been used as catalysts for the polymerization of vinyl chloride (248). Preparative studies have allowed the isolation of complexes of the type [MnCCpHjMeXCOlXRaSO)] [RjSO = (CH2)4SO, (CH20)2S0 see ref. 255], and infrared (257) and mass spectral studies (154, 275) have appeared on these and related systems. 

W. D. Good, D. M. Fairbrother, G. Waddington. Manganese Carbonyl Heat of Formation by Rotating-Bomb Calorimetry. J. Phys. Chem. 1958, 62, 853-856. 

Finally, manganese carbonyl complexes also show potential for effecting interesting phase transfer catalyzed carbonylation reactions. Alkynes react with carbon monoxide and methyl iodide in methylene chloride, using 5N NaOH as the aqueous phase, benzyl-triethylammonium chloride as the phase transfer catalyst, and either bromopentacarbonylmanganese or dimanganese decacarbonyl to afford... 

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