Rhenium carbonyl structure

Reaction of the manganese and rhenium carbonyls, M2(CO)10, with Ru3(CO)12 or Os3(CO)12 in a 3 1 ratio yields the products [M(CO)5]2M (CO)4, with M = Re or Mn, M = Ru or Os. These are considered to be linear trinuclear metal systems. The only other trinuclear carbonyl derivative isolated is OsCo2(CO)n, obtained as one of a number of compounds from the reaction of Co2(CO)8 with H2Os(CO)4. No structural data are available for this compound (241). 

The existence of the neutral rhenium carbonyl [Re(C0)4] was first claimed in 1965 206 but, although it is easily sublimed, it has not yet been characterized by mass spectrometry and the value of n is still not known. This colourless substance [v (CO) 2055 and 1995 cm-1 in CHC13] has been obtained as a by-product in the synthesis of Re2(CO)i0 starting from Re2S7, copper powder, and carbon monoxide at 85 atm, 200 °C206>. There has also been a report of the compound Re4(CO)10(PPh2Me)6, which can be considered to be a substitution product of the hypothetical species, Re4(CO)i6 it has been obtained by a photochemical reaction between Re2(CO)j0 and PPh2Me194. In both cases, and particularly in the phosphine derivative, a tetrahedral structure seems improbable because of steric constraints. 

Polymethylarsine (MeAs) reacts with the rhenium carbonyl Re2(CO),o, yielding a coordination compound of very complex structure and electron arrangement, [cyclo-(MeAs)7(As)Re(CO)4]Re(CO)6. This rhenium complex contains a nine-membered AsgRe ring, which contains one As atom without any methyl substitution and is coordinated to two Re(CO)3 units. 

Although less fully documented than osmium cluster chemistry, rhenium cluster chemistry has been subjected to many structural studies, including those on approximately 20 neutral or anionic carbonyls, particularly carbonyl hydrides [Rev(CO). H ] of nuclearities x = 2 to 6 (Fig. 7). In addition, some ten or more rhenium carbonyl carbides [Rev(CO)vH C] have been shown to contain a core carbon atom, usually occupying a central octahedral site. These systems offer scope not only to explore for rhenium the trends we have already shown for osmium, but also to study the effect on metal-metal distances (and so enthalpies) of such core carbon atoms, which formally donate all four of their valence shell electrons to the cluster bonding. To our knowledge only one rhenium carbonyl cluster compound, Re2(CO)io, has been subjected to calorimetric study to determine its enthalpy of formation. ... 

E2.1 Rhenium carbonyl clusters synthesis, structure, reactivity... 

What formulas would you expect for the metal carbonyls of (a) molybdenum, (b) osmium (c) rhenium Note that the simple carbonyls shown in Figure 23-15 have one metal atom per molecule. Some metal carbonyls are hinuclear that is, they have two metal atoms bonded together in the carbonyl structure. Also, (d) explain why iron and nickel carbonyls are liquids at room temperature, whereas that of cobalt is a solid, and (e) describe the probable nature of the bonding in the compound Na[V(CO)g]. 

A series of main-group transition metal clusters of manganese and rhenium with the structural types [37] and [32] has been isolated from reactions of the carbonyls with gallium and indium 201, 202, 323, 324. ... 

Structural features of the compounds in entries 1-6 have already been discussed in Section IV,A. The manganese compound in entry 2 (and its rhenium analog) were prepared by heating Ph2SiH2 with the metal carbonyl M2(CO)i0 similar germanium- and tin-manganese derivatives have been made via Eq. (144) (263, 414). 

---