Dimer-Forming Transition Elements Given that Mn(CO)5 exists,find its chemical properties: Manganese:[Ar](4s)2(3d)5-7 valence e 5 CO's provide 10 electrons to Mn,leaving Mn with 17 total e; but Mn wants 18 electrons.So,Mn forms a dimer: CO CO co co Mn. Mn. C0二 Mn co co CO co CO CO CO CO CO Mn2(CO)10 Halides,like fluorine,also act this way,because they also need only one electron to fill their shell.There are other similarities between transition elements with 7 valence e and halides... XIV-6
Mn Mn Dimer-Forming Transition Elements • Given that Mn(CO)5 exists, find its chemical properties: Manganese: [Ar] (4s)2 (3d)5 → 7 valence e- • 5 COʼs provide 10 electrons to Mn, leaving Mn with 17 total e- ; but Mn wants 18 electrons. So, Mn forms a dimer: Mn Mn • Halides, like fluorine, also act this way, because they also need only one electron to fill their shell. There are other similarities between transition elements with 7 valence e- and halides... Mn2(CO)10 CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO XIV-6
Transition Metals That Are Like Halides As we have seen,transition elements with 7 valence e (like Mn and Re)which are bonded to 2e donors (like CO) form dimers,because they need only one extra e. Another similarity is reactivity with light: Br2 hv→2Br Mnz(CO)o-hv2Mn(CO) Another similarity is a phenomenon called "coupling": Br+ Br-l co cO cO CO- Re, cO co co Mn(CO)5 Re(CO)5 CO XIV-7
Transition Metals That Are Like Halides • As we have seen, transition elements with 7 valence e- (like Mn and Re) which are bonded to 2 e- donors (like CO) form dimers, because they need only one extra e- . • Another similarity is reactivity with light: Br2 2 Br Mn2(CO)10 2 Mn(CO)5 • Another similarity is a phenomenon called “coupling”: Br + I Br—I Mn(CO)5 + Re(CO)5 Mn Re CO CO CO CO CO CO CO CO CO CO hν hν XIV-7