The molecule dimethylphosphinoethane \(\left[\left(\mathrm{CH}_{3}\right)_{2} \mathrm{PCH}_{2}^{-}\right.\) \(\mathrm{CH}_{2} \mathrm{P}\left(\mathrm{CH}_{3}\right)_{2},\) which is abbreviated dmpe \(]\) is used as a ligand for some complexes that serve as catalysts. A complex that contains this ligand is \(\mathrm{Mo}(\mathrm{CO})_{4}(\) dmpe \() .\) (a) Draw the Lewis structure for dmpe, and compare it with ethylenediammine as a coordinating ligand. (b) What is the oxidation state of Mo in \(\mathrm{Na}_{2}\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\) dmpe \()\right] ?(\mathrm{c})\) Sketch the structure of the \(\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\mathrm{dmpe})\right]^{2-}\) ion, including all the pos- sible isomers.

1. Write the molecular formula for dmpe: \(\left(\mathrm{CH}_{3}\right)_{2}\mathrm{PCH}_{2}\mathrm{CH}_{2}\mathrm{P}\left(\mathrm{CH}_{3}\right)_{2}\) 2. Count the total number of valence electrons in the dmpe molecule: - There are 2 P (phosphorus) atoms with 5 valence electrons each (total 10). - There are 10 C (carbon) atoms with 4 valence electrons each (total 40). - There are 20 H (hydrogen) atoms with 1 valence electron each (total 20). - The total number of valence electrons is 10+40+20=70. 3. Draw the Lewis structure of dmpe by arranging the atoms and distributing the valence electrons: - Connect each P (phosphorus) atom to one CH2 group each, these groups are connected to each other, forming the backbone of the molecule. - Connect each CH2 group to two CH3 groups, one on each end. - Distribute the remaining valence electrons to form multiple bonds and satisfy the octet rule for each atom. 4. Compare dmpe with ethylenediammine as coordinating ligands: - Ethylenediammine (\(\mathrm{NH}_{2}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2}\)) is a bidentate ligand capable of donating lone pairs of electrons from its two nitrogen atoms. - dmpe is also a bidentate ligand but is capable of donating lone pairs of electrons from its two phosphorus atoms. - Both ligands are able to form chelate complexes due to their ability to form multiple bonds with a metal ion, but they do this through different atoms (phosphorus in dmpe and nitrogen in ethylenediammine).

1. Write the formula for the complex: \(\mathrm{Na}_{2}\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\mathrm{dmpe})\right]\) 2. Determine the charges contributed by the ligands in the complex: - Each CN (cyanide) ligand has a charge of -1, contributing -2 to the complex. - CO (carbonyl) ligands and dmpe are neutral with no charge contribution. 3. Calculate the charge of the metal ion (Mo) in the complex: - Since this is a complex, let's assign the charge of Mo as 'x'. - The overall charge of the complex is -2. - The complex is neutralized by 2 sodium (Na) ions, each with a charge of +1. - Solve for x: x - 2 (CN) + 0 (CO & dmpe) = (-2 overall charge) - x -2 = -2 - x = 0 4. The oxidation state of Mo in the complex is 0.

1. Write the formula for the ion: \(\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\mathrm{dmpe})\right]^{2-}\) 2. Identify the coordination number of Mo in the complex: - Coordination number represents the number of ligand bonds with the central metal ion. - Mo is coordinated to 2 CN ligands, 2 CO ligands, and 1 bidentate dmpe ligand, which contributes 2 lone pairs to the coordination sphere. - The coordination number of Mo in this complex is 2 + 2 + 2 = 6. 3. Draw the structure of the ion, considering possible isomers, by placing Mo at the center and arranging the ligands around it: - The structure of the \(\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\mathrm{dmpe})\right]^{2-}\) ion is an octahedral complex, with the desired coordination number of Mo. - The possible isomers of this complex are determined by the placement of CN, CO, and dmpe ligands around the Mo center. - There are two structural isomers: one with cis-arranged CN ligands (CN ligands are adjacent) and one with trans-arranged CN ligands (CN ligands are opposite to each other). - Draw the cis-[Mo(CN)2(CO)2(dmpe)]^(2-) ion with CN ligands adjacent, CO ligands adjacent, and the dmpe ligand forming two bonds with Mo. - Draw the trans-[Mo(CN)2(CO)2(dmpe)]^(2-) ion with CN ligands opposite each other, CO ligands opposite each other, and the dmpe ligand forming two bonds with Mo. 4. In conclusion, two possible isomers of the \(\left[\mathrm{Mo}(\mathrm{CN})_{2}(\mathrm{CO})_{2}(\mathrm{dmpe})\right]^{2-}\) ion are cis-[Mo(CN)2(CO)2(dmpe)]^(2-) and trans-[Mo(CN)2(CO)2(dmpe)]^(2-).