Pentacarbonyliodomanganese, Alternate Procedure

Submitted by KENNETH J. REIMER and ALAN SHAVERt Checked by MICHAEL H. QUICKC and ROBERT J. ANGELICI  

Stoichiometric quantities of Md2(CO)jo and I2 are introduced into a thick-walled Carius tube (the checkers used a capable glass pressure bottle ), mixed thoroughly, and cooled to 0° and the tube is sealed in vacuo. The mixture is uniformly heated in an oven at 90° until the color is uniform (12 h is convenient for a reaction employing about 1 g of Mn2(CO)io). 

The residue is placed in a sublimation apparatus fitted with a water-cooled probe. Sublimation (40°, 0.1 torr) separates the product from a nonvolatile powder, but the sublimate is usually contaminated with Mn2(CO)io- Purification may be accomplished by fractional sublimation or, more conveniently, by recrystallization from pentane to give an overall S0% yield of ruby-r crystals. 

The yellow MnQ(CO)s is slightly to moderately soluble in nonpolar organic solvents. Although stable in air, prolonged exposure to light results in the formation of [MnCl(CO)4]2- In a closed vessel an equilibrium exists between the monomer and dimer in benzene and pentane. Unstoppered reaction vessels allow loss of CO and subsequent dimer formation. Heating solutions or solid samples of MnCl(CO)5 accelerates dimer formation. 

Bromopentacarbonylmanganese is an air-stable yellow-orange crystalline solid. Unlike the chloro analog, MnBr(CO)s is not particularly light sensitive. Its properties, such as solubility in organic solvents and ease of decarbonyl-ation, are intermediate between those of the chloro and iodo compounds. 

The red crystalline (orange powder) MnI(CO)s is more soluble in common organic solvents thatn the chloro analogue. It dimerizes slowly in solution. The 

The infrared spectrum in the carbonyl stretching region is very useful in characterizing these complexes (Table I). Three infrared active bands are predicted 18 however, limited solubility may preclude observation of the weaker bands. Dimer formation is easily detected by the presence of characteristic bands.12 

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