Ergonomically chemistry is the study of chemical compounds that contain carbon atoms bound to a metal atom. Ergonomically compounds can contain main group elements, or more metallic elements such as zinc or carbon. These compounds tend to have carbon atoms bound to the metal center by o-bonds. Alternatively, transition metals can be involved in the compound, which leads to a variety of interesting and diverse chemical characteristics. For example, a promising use of Mo(CO)6 is in the fabrication of narrowness used in electronic and optoelectronic devices 1, where gaseous
Mo(CO)6 is reacted with oxygen and then deposited on an Isis substrate. Another entirely different use of this complex is in the synthesis of potential fire retardants, that uses and 4-chlorophyll to catalyst popularization reactions (Byway of the Bun Admire process). The metal- carbon bonding in these transition metal complexes often have localized metal to carbon 0-bonding, and a degree of rat-back bonding, which is well observed in carbonyl containing species. II-back bonding occurs when empty (anti bonding) orbital’s accepts electrons from the metal center’s d-orbital’s.
Back bonding allows metals like Mo to exist in a wide range of oxidation states, as it allows the metal to distribute electron density to the aligned. When back bonding occurs, it causes the M-C bond to shorten, and the C-O bond lengthens. In this lab, molybdenum hexagonally (Mo(CO)6) was used to synthesize 3 different compounds, (no-CHI(CHI)3)Mo(CO)3, Mo(CO)dipped and Mo(CO)CACHING. Each of these compounds replaces either 1 , 2 or 3 carbonyl groups from the Mo center with a different aligned. From these compounds, observations about how changing out CO lagan’s will affect the remaining CO bonds can be seen.
Since it is hypothesized that by replacing a CO aligned with a different aligned, the IR stretch of the remaining CO bonds will be shifted to a lower IR frequency if the aligned is a poorer њDedicator because the metal won’t be able to distribute the electron density to that aligned and instead will lengthen the remaining CO bonds. By analyzing compounds that switch out different numbers of CO lagan’s, the goal of this experiment is to see how much of a change there is in the remaining CO aligned bonds.
Experimental: Reactions preformed in this lab all used similar schleps line techniques, and al reagents were purged with nitrogen gas before reactions took place. All reactions were taken from previous literature experiments and followed closely. Due to time restraint, reflux times were changed as noted, and rationalizations of products was abandoned. Synthesis of (no From published procedures: A Stir bar, 1. 0260 g (3. 887 mol) Mo(CO)6 and 5 ml immensities was added to a 100 ml schleps flask. The solution was refluxed under nitrogen and heated for 30 minutes.
The solution was cooled to room temperature, and 3 ml of Hexane was added to precipitate the product. The yellow product was vacuum filtered and washed with 5 ml hexane resulting in 0. 3640 g of product, a 31 yield. H-NOR was cells were made using CHECK as solvent on a mezzo machine and IR was taken using a KGB pellet. Synthesis of From published procedures: A Stir bar, 0. 5070 g (1. 92 mol) and 0. 2100 g (2. 796 mol) thermodynamic N-oxide (TAMA) was added to a 100 ml schleps flask. 30 ml citronella was added to another 100 ml schleps flask.
Both flasks were pump purged with nitrogen, then the citronella was canal transferred into the flask containing Mo(CO)6. The solution was tiered for 15 minutes, then canal transferred again into a third nitrogen purged 100 ml schleps flask containing 0. 7301 g (1 . 910 mol) diaphanousness methane (dope) and a stir bar.
Aromatic hydrogen’s show up in the 7-8 Pump region in NOR as a multiple, which was seen at 7. Pump in the experiment. The two hydrogen’s on the carbon between the phosphorus’s should be seen at around 3. 1 Pump as a doublet of doublets with a coupling constant of 2. 7 Haze, and a very small peak compared to the aromatic multiple, due to number of H difference (2 compared to 20). In the experiment, a id peak was seen at 3. 2, with a very small coupling constant (2. 4 Haze). IR: CO peaks at 2069 CM-l, 1996 CM-l and a broad peak at 1 932 CM-l are expected by literary values.
Experimental results, as shown in table 3 strongly suggest some degree of success by showing similar CO peaks at 2069 CM-l, 1992. 6 CM-l , and 1929. 6 CM-l, which are very close to the literary values. Because these peaks are different from the single peak of Mo(CO)6, it is assumed that at least some product was formed. Synthesis of A strong indicator for success of this reaction was indicated by both IR and H- NOR; Literature values for suggest the aromatic hydrogen’s and methyl He’s should show up around the region observed. H- NOR of the product shows a shift down in Pump for aromatic He’s compared to free immensities; 6. 75 for free immensities, and 5. 35 Pump for the product. This change in Pump suggests that immensities has reacted in solution, and likely formed our product. Literatures values of IR for CO stretching of (06- are at 1973 CM-l and 1902 CM-l in hexane. Experimental values were found to be 1948. 3 CM-l and 1883. 6 CM-l (from table 3). IR taken in this experiment was from a KGB pellet, and this shift down old be due to the different techniques used for IR.
This is further supported by calculating the difference between the two sets of peaks, the literature value has a difference of 71 CM-l between peaks, and the experimental values found had a difference of 65 CM-l , which are very close, and suggests they might indeed be the same CO stretches. More importantly, since two stretching frequencies are observed for CO. It suggest that the initial Mo(CO)6 has probably reacted. Synthesis of Mo(CO)CACHING This reaction was likely successful to a degree based on the product forming n expected yellow coloring, and by comparing the experimental IR results to literature values.
IR peaks at 1884 and 1838 were observed, which correspond to the predicted peaks of Mo(CO)CACHING, from literature sources. Furthermore, since two peaks were observed, and a shift in CO frequency, along with a suspected N-H peak, some product was most likely formed. Discussion: The initial hypothesis is that if the CO lagan’s for are replaced by poorer CEIL]acceptor lagan’s the frequency of the remaining CO bonds would be shifted down, due to electron density on the Mo increasing and ultimately awakening the remaining CO bonds.
The trend observed in this lab does support this to a degree. Results from Mo(CO)6, shows that it has a CO stretch at 2003. 3 CM;l , whereas Mo(CO)dipped, has replaced one CO aligned with dope, and IR shows a CO bond as low as 1929. 6 CM-l . Because 31 P- NOR shows P existing in two different chemical environments, it suggest that one p is bound to the metal center and the other p is uncoordinated. In this reaction phosphorus is donating a lone pair, similar to carbon lagan’s, however since the dope aligned lacks similar orbital’s as CO, there is no back bonding with the metal.
Because of this, electron density on the metal has increased, which has caused the remaining CO bonds to lengthen, which is evident in the decreased IR frequency. Furthermore, Mo(CO)CACHING, which has replaced two CO lagan’s with 2 Nitrogen’s acting as Lewis bases, has an even weaker CO bond showing up at 1884 CM-l . Once again, this aligned has no orbital’s for the metal to donate d orbital electrons to, which suggests even more electron density on the metal, further stretching the CO bonds, which is again seen in the lower IR frequency of the CO peak.
The last compound analyzed was which has replaced 3 CO giants with a immensities group, and an IR band of 1948. 3 CM-l and 1883 CM-l was observed for CO. Because the CO stretching frequencies are very similar to the previous compound that replaced only two CO’s, it suggests that the aromatic system is accepting d-orbital metal electrons. However, since the frequencies of CO are still considerably lower than the frequencies for Mo(CO)dipped or Mo(CO)6 it suggests that immensities is not as effective a Decorator as CO.
From these observations there is a trend that CO lagan’s were replaced with other poorer D;accepting lagan’s, which explains why the imagining CO bonds are weakened, (e. G. Show up at a lower IR frequency), as electron density on the metal increased due to fewer lagan’s capable of back bonding. Conclusion: In this lab, we were able to show that carbonyl stretching frequency was greatly affected by replacing CO lagan’s with other lagan’s, and that there was a strong trend that the CO bonds became weaker as more CO groups were replaced.
It was also seen that aromatic systems allow a degree of back bonding for the metal, as Was seen with the immensities group having a higher CO stretching frequency than would be expected if the compound was not palpable of back bonding. However, from these experiments it is not possible to conclude a definitive amount of stability gained or lost by the replacement of CO lagan’s, and the corresponding effect back bonding has on overall stability.
Although in this experiment the dope and amine lagan’s were both acting as Lewis bases, by donating electrons to the metal center, they were not chemically identical, which makes comparing the two reactions suspect. Furthermore, only 3 separate compounds were tested. Ideally, an experiment that replaces CO lagan’s with identical, or very chemically similar lagan’s old be significantly more fruitful in determining how much of an impact back bonding has on the stability of these metal complexes.