Final Exam extra info Flashcards
(32 cards)
organometallic reactions form..
polymers, catalysts
ligand dissociation
L leaves, changes e- count, the less stable form can more easily pick up a different L
ligand association
often not for complexes with 18 e, add ligand, and then typically an L will be lost to bring it to the stable e configuration
trans effect
for square planar, ligand trans to Cl is more likely to leave than trans to NH3 (the electroneg pulls the bond on that axis towards Cl). this is true for pi acceptors, donors, and least effective are sigma donors
oxidative addition
adding usually H2 to a M, increases e- count by 2 and ox state by 2. add as cis, trans, or mixture depending on what orbital the molecule first binds with
reductive elimination
lose 2 e- and 2 ox state. used to form HH, CH, CC, CX bonds when the 2 L are removed
1,1 insertion
inserts 1 atom of a molecule into the ML bond
1,2 insertion
inserts 1 attached to M and 2 attached to L in ML bond
beta hydride elimination
aka deinsertion, beta H attacks M and e- from M-L bond come up to fill where it was attached, often releasing the product we want from M
how to do 1,2 etc
start with least substituted (is most likely to bind with M)
metathesis
switching part of the molecule. can be cross- or self-. can be double or triple too but we often see sigma bond metathesis. we also call substituting a ligand in 1 transition step
olefin
another word for alkene
hydrogenation
a reaction scheme (not just 1 step). forming CH bonds
Wilkinsons catalyst
used for hydrogenation, (PPh3)3RhCl, needs to dissociate a PPh3 to be less stable and start catalyzing
changes in catalytic cycle based on metal center
for metals with lots of d-electrons, pathway can include redox, but without d-electrons another route must be used.o
olefin polymerization
uses catalyst with usually Ti, Hf or Zr and forms ion with MAO. (MAO will pick up halides, alkyls = lewis acid). add ethylene btwn M and H repeatedly forming chain, and stop adding by forming alkene at end of chain (beta hydride elim) or metathesis with H, leads to initial catalyst either way.
tacticity
direction of C coming off a chain (PE doesnt have these but polypropylene).
atactic
chains come off in random pattern
syndiotactic
alternating C btwn out and in the plane
isotactic
all C on chain point the same direction
heterogenous catalyst
solid and reactant is liquid or gas, inc. Ziegler and Phillips, and these are needed in very small amts as reaction substrate
homogenous catalyst
used in aq form usually and reactants are also aqueous
Ziegler catalyst
for olefin polymerization (most widely used one), TiCl4/MgCl2 solid.
Phillips catalyst
for olefin polymerization, CrO?/SiO2
