Convenient
synthe
se
s are de
scribed for the five-,
six-, and
seven-membered pho
sphacycle
s PhP(CH
2)
x-1,where
x = 5 (
La5), 6 (
La6), 7 (
La7), and Bu
tP(CH
2)
x-1 where
x = 5 (
Lb5), 6 (
Lb6), 7 (
Lb7). Treatment of[PtCl
2(cod)] with
La5-7 give
s cis-[PtCl
2(
La5-7)
2] (
1a5-7), wherea
s with
Lb5-7 a mixture of
cis-[PtCl
2(
Lb5-7)
2] (
1b5-7) and
trans-[PtCl
2(
Lb5-7)
2] (
2b5-7) i
s obtained. Metathe
si
s of
1a7 with NaI give
s a mixtureof
cis-[PtI
2(
La7)
2] (
3a7) and
trans-[PtI
2(
La7)
2] (
4a7). The cry
stal
structure
s of
1a5,
1a6,
1a7, and
4a7 havebeen determined. Compari
son of the
structure
s of
1a7 and
4a7 reveal
s that
La7 ha
s variable
steric bulk,with the cry
stallographically determined cone angle ranging from 137
![](/image<font color=)
s/entitie
s/deg.gif"> (
smaller than
La5) to 172
![](/image<font color=)
s/entitie
s/deg.gif"> (largerthan
La6), depending on the particular twi
st-chair
seven-membered-ring conformation
s adopted. Thecomplex
cis-[PtCl
2(
Lb6)] (
1b6) i
s fluxional on the NMR time
scale at ambient temperature
s, a
s a re
sultof re
stricted PtP rotation. Treatment of [Rh
2Cl
2(CO)
4] with
La5-7 or
Lb5-7 give
s the expected
trans-[RhCl(CO)(
La5-7)
2] (
5a5-7) or
trans-[RhCl(CO)(
Lb5-7)
2] (
5b5-7), and from the
![](/image<font color=)
s/gifchar
s/nu.gif" BORDER=0 >
CO value
s, it i
s deducedthat the donor
strength
s to rhodium(I) are in the order
Lb5-7 >
La5-7 and, within the
La and
Lb serie
s,
L7,
L6 >
L5. An inve
stigation into the kinetic
s of the oxidative addition of MeI to
5a5-7 showed that therate of reaction i
s in the order
5a5 >
5a7 >
5a6; i.e., the
smalle
st ligand give
s the highe
st rate. It i
spo
stulated that the flexible
La7 ligand adopt
s a lower bulk conformation and the order of decrea
sing ratei
s then in the order of increa
sing bulk. The rate of reaction of MeI with
5b5 i
s 4 time
s fa
ster than with
5a5, but oxidative addition wa
s not ob
served with
5b6 or
5b7, perhap
s becau
se
steric conge
stion de
stabilize
sthe rhodium(III) product. A
study of the rhodium-catalyzed hydroformylation of 1-octene i
s reportedu
sing ligand
s La5-7 and
Lb5-7, but no
sy
stematic trend
s were ob
served, and the re
sult
s for
La5-7 were
similar to tho
se for the acyclic analogue PhPEt
2. An anomalou
s but reproducible re
sult i
s that the cataly
stderived from
Lb7 show
s negligible hydroformylation activity but rapid octene i
somerization activity.The overall conclu
sion i
s that, with the rhodium complexe
s of the
simple pho
sphacycle
s de
scribed here,no
special effect of the ring
s wa
s ob
served in the hydroformylation cataly
si
s. An
![](/image<font color=)
s/gifchar
s/alpha.gif" BORDER=0>-
sub
stituent effect i
sidentified a
s a common feature in
several high-activity hydroformylation cataly
st
s derived frompho
sphinane
s.