The steric, electronic, and synthetic characteristics o
f 3,4-diazaphospholanes are reported. Crystallographic structures o
f free and metal-complexed 3,4-diazaphospholanes provide steric metrics (coneangle, solid angle, etc.). Diazaphospholanes span a wide range o
f sizes with cone angles varying
from135 to 188
![](/images/entities/deg.gi<font color=)
f">. The electron-donating abilities o
f diazaphospholanes have been estimated using the carbonylin
frared stretching
frequencies,
![](/images/gi<font color=)
fchars/nu.gi
f" BORDER=0 >(CO), o
f [
trans-Rh(diazaphospholane)
2(CO)Cl] complexes. Frequencies
for the CO stretches range
from 1975 to 2011 cm
-1, thus indicating that 3,4-diazaphospholanes may beas electron rich as dialkylarylphosphines or as electron de
ficient as trialkyl phosphites. Reduction o
fN,
N'-phthalamido-3,4-diazaphospholanes with BH
3·SMe
2 yields diazaphospholanes that not only are moreelectron rich but also show a reorientation o
f the phospholane substituents that may a
ffect catalyticproperties. Diazaphospholanes readily react with many Rh and Pd catalyst precursors to
form complexes.Metal complexes o
f 3,4-diazaphospholanes exhibit reactivities di
fferent
from those o
f common phosphinecomplexes, presumably due to the generally greater steric bulk and electron de
ficiency o
f 3,4-diazaphospholanes relative to phosphines. Cationic Rh(I) complexes o
f 3,4-diazaphospholanes abstractchloride ligands
from chlorinated solvents to a
fford chloride-bridged dimers. The complex [(
rac-
17)Pd(Me)Cl] rearranges in solution-stereoselectively trans
ferring methyl
from palladium to phosphorus whilesimultaneously opening a diazaphospholane ring. Many o
f the 3,4-diazaphospholane-metal complexeshave extremely close Cl···H-C(P)(N) contacts, suggesting Cl···H hydrogen bonding.