Dimanganese decacarbonyl
Dimanganese decacarbonyl is the chemical compound with the formula Mn(CO). This metal carbonyl is an important reagent in the organometallic chemistry of manganese. Synthesis. The compound was first prepared in low yield by the reduction of manganese iodide with magnesium under CO. A more efficient preparation entails reduction of anhydrous MnCl with sodium benzophenone ketyl under 200 atmospheres of CO. The availability of inexpensive methylcyclopentadienyl manganese tricarbonyl ("MMT") has led to a low pressure route to Mn(CO). Structure. The crystal structure of Mn(CO) was redetermined at high precision at room temperature in 1981 and bond lengths mentioned herein  refer to results from that study. Mn(CO) has no bridging CO ligands: it can be described as containing two axially-linked (CO)Mn- subunits. There are two kinds of CO ligands; there is one CO linked to each Mn atom that is coaxial with the Mn-Mn bond and there are four “equatorial” carbonyls bonded to each Mn atom that are nearly perpendicular to the Mn-Mn bond (Mn’-Mn-CO(equatorial) angles range from 84.61(7) to 89.16(7) degrees). The axial carbonyl distance of (181.1 pm) is 4.5 pm shorter than the average equatorial manganese-carbonyl distance of 185.6 pm. In the stable  rotamer, the two Mn(CO) subunits are staggered. Thus, the overall molecule has approximate point group D symmetry, which is an uncommon symmetry shared with SF. The Mn(CO) molecule is isomorphous with Re(CO) and the corresponding decacarbonyl of Tc. Reactions. Mn(CO) is air stable as a crystalline solid, but solutions require Schlenk techniques. It finds limited use in organic synthesis. Characteristic reactions: The anion is a versatile nucleophile. Protonation gives the hydride [HMn(CO)], and methylation gives [(CH)Mn(CO)]. Safety. Mn(CO) is a volatile source of a metal and a source of CO.