What does the term ligand mean when used in the chemistry of the transition elements?
Describe the bond type formed between a ligand and a transition element.
Chromium hexacarbonyl is involved in the following ligand replacement reaction: $\text{Cr(CO)}_6 + \text{PR}_3 \rightarrow \text{Cr(CO)}_5\text{PR}_3 + \text{CO}$ Two different experiments were run to investigate the rate of this reaction. In the first, the ligand $\text{PR}_3$ was present in large excess and $[\text{Cr(CO)}_6]$ was recorded against time. The graph displays the results. In the second, $\text{Cr(CO)}_6$ was in large excess, and $[\text{PR}_3]$ was tracked with time. Plot the table values onto the graph above, keeping to the same axis scales, and draw the best-fit line through the points.
Chromium hexacarbonyl is involved in the following ligand replacement reaction: $\text{Cr(CO)}_6 + \text{PR}_3 \rightarrow \text{Cr(CO)}_5\text{PR}_3 + \text{CO}$. Two separate experiments were used to study how fast this reaction occurs. In the first, $\text{PR}_3$ was in large excess and $[\text{Cr(CO)}_6]$ was followed with time. The results appear on the graph.
Use the graphs to find the order of reaction with respect to $\text{Cr(CO)}_6$ and $\text{PR}_3$. In each case, explain how you reached your conclusion.
Write the rate equation for the reaction, and work out a value for the rate constant, using the method of initial rates or any other method you choose.
State the units that apply to the rate constant.
Four possible mechanisms for this reaction are shown below. Circle the letter beside the mechanism that agrees with the rate equation you wrote in (iii). Explain your answer.