Question

2. For each of the following compounds, 1) write the formal oxidation state of the transition metal and 2) the corresponding number of d electrons. 3) State whether or not each one is likely to be stable enough to be characterized. (a) [Re(CO)5] (b) [Cr(η6 -C6H6)2] (c) [Mo(CO)3(PPh3)3] (d) [Fe(η2 -C2H4)(CO)4] (e) [Zr(η5 -C5H5)Cl(OH)] (f) [Co(η5 -C5H5)2]

3. Identify the first-row transition metal (M) that follows the 18-electron rule for each of the following compounds (show how you arrived at your answer): (a) [M(CO)2(PPh3)2] − (b) [M(η 4 -C4H4)(CO)3] (c) [M(η 5 -C5H5)(CO)3]2 (assume single M−M bond)

4. Assuming that each of the following obeys the 18-electron rule, determine the number of metal-metal bonds in each complex. Show how you arrived at your answer and sketch a possible structure in each case. (a) [Mn(η5 -C5H5)(CO)2]2 (b) μ-CO-[Fe(η4 -C4H4)(CO)2]2 (c) (μ-Br)2-[Mn(CO)4]2

5. When [Mo(η 5 -C5H5)(CO)3]2 is heated, it loses two CO ligands to become [Mo(η5 -C5H5)(CO)2]2, and the energies of the CO stretches change from 1960 cm−1 and 1915 cm−1 to 1859 cm−1 and 1819 cm−1 . The Mo-Mo bond length also shortens by 80 pm. Suggest plausible chemical structures for each of the compounds, and explain the change in energy of the CO stretches.

6. First, briefly explain the following trend for the CO stretching energy. Next, predict the trend in the M-C and C-O bond lengths. M(CO)6 ν(CO), cm−1 [W(CO)6] 1977 [Re(CO)6] + 2085 [Os(CO)6] 2+ 2190 [Ir(CO)6] 3+ 2254

Answer 1

2.a) Re (co)s Fomal oxidation stef Re Cee)) no..ef d. electrons 57ave) Total Total valence alectyom 5 x -so it is uns table to be anan actenreed. FoTw Total do) of d-electrons- - it obeys 19e, o is stalule enough t Mo(CO)3 (PPh) - it obtys 1 -ul. So t is table to be stable enagh t be onnactntc

2) No of d-electronの = e204 TotoO valence electrons at (4+5+ -un stab] e to be enanactoriced. No.of d-electrown. = total valen (a elechon 5( five) (at Sts) e7 -Ur1stalole to be enon ac tur ted

Mi ) oxidation stecte 18 e- Min 군ero oxidation state n1.catty = 4e SM will be keelo) (o 12 MIS in ,ti, o.s. I Mn-Mn 2-е for each mo tal centr a= 26 36 Totnl valence e" (TVE): X2) + (SX 2) t lax?) 32 no of Metal- Meth s3 18x2) ← No.o 2 2. Ср Co OC

Co - (zw) (4x2) +(4x2) 34 stucture Co g,千 . 익 M-M bonds 2 (1812)- 3y 2. 0 fr Co Co

in follo asina γ.wcuns the LMo(P-15 Hs)(co)3]2 sbuctu ya -tHere cach Mo cntve han 1g vatanu CO neating, it undarqs the followi eR 4 Co Co or Here each Mo untre nig har eong in,psi tabe, there This is ony, upon heating, tne igecorupex İS LAtitized for back boning with bridging agend. But -fonra non-brndgrd eomplex, to te teminal eo tigjands. so, gveaten amount t b 4onchon

1Suy, in, cape non-brn dged system 16mm canbonyl decreaes