A simple straightforward synthesis of phenylphosphane and the photoinitiator bis(mesitoyl)phenylphosphane oxide (IRGACURE 819)

Article abstract of DOI:10.2533/chimia.2008.18

A straightforward high-yield synthesis for the photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphane oxide (16, IRGACURE 819) involves: i) the reaction of phenyldichlorophosphane, PhPCl₂, with sodium to give [Na₂(P₂Ph₂)(tmeda)]₆ (5); ii) protonation of 5 with tert-butanol to give 1,2-diphenyldiphosphane, PhHP-PHPh (12); iii) reduction of 12 by sodium to yield [Na(PHPh)_x (13); iv) protonation of 13 with tert-butanol to give phenylphosphane PhPH₂ (14) in excellent yields; v) reaction of 14 with 2,4,6-trimethylbenzoylchloride (MesCOCI) in presence of the NaOt-Bu formed in steps ii and iv to give bis(2,4,6-trimethylbenzoyl)phenylphosphane 7; vi) oxygenation of 7 with 30% aqueous hydrogen peroxide to give the final product 16. This reaction can be performed in toluene with about 4 vol-% of tmeda as an activator in a one-pot synthesis without changing the solvent. The structures determined by X-ray diffraction of the unique hexameric aggregate 5 and 16 are reported. Schweizerische Chemische Gesellschaft.

Full text of DOI:10.2533/chimia.2008.18

HOT TOPICS
18
doi:10.2533/chimia.2008.18
CHIMIA 2008, 62, No. 1/2
Chimia 62 (2008) 18–22
Schweizerische Chemische Gesellschaft
ISSN 0009–4293
©
A Simple Straightforward Synthesis of
Phenylphosphane and the Photoinitiator
Bis(mesitoyl)phenylphosphane Oxide
(IRGACURE 819)
a
a
a
a
a
Hansjörg Grützmacher* , Jens Geier , Daniel Stein , Timo Ott , Hartmut Schönberg , Reinhard
b
b
c
c
d
H. Sommerlade , Souad Boulmaaz , Jean-Pierre Wolf , Peter Murer , and Thomas Ulrich
Abstract: A straightforward high-yield synthesis for the photoinitiator bis(2,4,6-trimethylbenzoyl)phenylphosphane
oxide (16, IRGACURE 819) involves: i) the reaction of phenyldichlorophosphane, PhPCl , with sodium to give
2
[
Na (P Ph )(tmeda)] (5); ii) protonation of 5 with tert-butanol to give 1,2-diphenyldiphosphane, PhHP-PHPh (12); iii)
2 2 2 6
reduction of 12 by sodium to yield [Na(PHPh)] (13); iv) protonation of 13 with tert-butanol to give phenylphosphane
x
PhPH (14) in excellent yields; v) reaction of 14 with 2,4,6-trimethylbenzoylchloride (MesCOCl) in presence of the
2
NaOt-Bu formed in steps ii and iv to give bis(2,4,6-trimethylbenzoyl)phenylphosphane 7; vi) oxygenation of 7 with
30% aqueous hydrogen peroxide to give the final product 16. This reaction can be performed in toluene with about
4
vol-% of tmeda as an activator in a one-pot synthesis without changing the solvent. The structures determined
by X-ray diffraction of the unique hexameric aggregate 5 and 16 are reported.
Keywords: Acylphosphanes · Ion triples · Phosphanes · Phosphorus · Photoinitiators · Sodium
1. Introduction
acylchloride in presence of a base which vantages in this preparation are the use of
leads to bis(acyl)phosphanes (BAPs) in the lithium as reducing metal and the necessity
Bis(acyl)phosphanoxides (BAPOs) are first step (Eqn. (1), Scheme 1). Oxidation to change the solvent before the oxygen-
very potent photoinitiators for a wide va- with hydrogen peroxide subsequently leads ation with H O .
2
2
riety of polymerization, coating, and cur- to the corresponding BAPO. However, due
Hence,thedevelopmentofaprotocolfor
ing processes and have been intensively to its pyrophoric and toxic properties, phe- the synthesis of IRGACURE 819 in hydro-
[1]
investigated over the last two decades.
nylphosphane is no longer available in bulk carbon solvents and employing sodium as a
Commonly they are synthesized from a quantities.Alternatively, the reaction of bis- cheaper reducing metal was desirable. With
primary phosphane and two equivalents of metallated phosphandiides, [M PR], with this aim in mind, we started to investigate
2
acylchlorides was proposed (Eqn. (2)). Th e
the reaction of phenyldichlorophosphane,
‘
M PR’ compounds were believed to be PhPCl (IUPAC: phenylphosphonous acid
2
2
formed in the reaction of organyl phospho- dichloride) with sodium in toluene or xy-
rus dichlorides, RPCl , with alkali metals M lene in the presence of small amounts of te-
2
=
Li, Na, K. Specifically, the commercially tramethylethylenediamine, tmeda, as an ac-
available bis(2,4,6-trimethylbenzoyl)phe- tivator. In this report, we describe the tmeda
nylphosphane oxide IRGACURE 819 has complex of disodium diphenyldiphosphan-
been prepared from PhPCl , lithium, and diide, [Na (P Ph )(tmeda)] , whose struc-
2
2
2
2
6
2
,4,6-trimethylbenzoylchloride (MesCO- ture we finally could determine, and a con-
[2]
Cl) in TH F as solvent (Scheme 1).
Disad- venient one-pot synthesis of IRGACURE
*
Correspondence: Prof. Dr. H. Grützmachera
Tel.: +41 1 632 28 55
Fax: +41 1 633 10 32
E-mail: hgruetzmacher@ethz.ch
a
Department of Chemistry and Applied Biosciences
ETH Zürich, Wolfgang-Pauli-Strasse 10
CH-8093 Zürich
b
Process Research, Coating Effects Segment
Ciba Inc., P. O. Box, CH-4002 Basel
c
R&D, Coating Effects Segment, Ciba Inc., P. O. Box
CH-4002 Basel
d
Process Optimization, Coating Effects Segment
Ciba Inc., P. O. Box, CH-4002 Basel
Scheme 1. Synthetic routes to bis(acyl)phosphane oxides

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19
CHIMIA 2008, 62, No. 1/2
8
19 from PhPCl , sodium, and MesCOCl
2
in a hydrocarbon solvent.
2
. Results and Discussion
InthefirststepsofthereactionofPhPCl2
with sodium, the cyclic pentaphenylcyclo-
pentaphosphane, (PhP) , is obtained in re-
5
ductive bond-forming reactions without the
[
3]
detection of any other intermediates.
In the following steps, P−P bonds are
reductively cleaved (a reaction typical for
compounds containing bonds between
heavier main group elements, c.f. sulfur,
silanes, etc.) and depending on the reac-
tion conditions the 1,2,3,4-tetraphenyltetra-
phosphane-1,4-diide, [Na (P Ph )(tmeda) ]
Scheme 2. Synthesis of disodium oligo(phenyl)phosphandiides 3–5 in hydrocarbon solvents
2
4
4
2
[4]
(
3), 1,2,3-triphenyltriphosphane-1,3-diide,
[4]
[
Na (P Ph )(tmeda) ] (4), or 1,2-diphenyl-
2
3
3
3
diphosphan-1,2-diide [Na (P Ph )(tmeda)]
2
2
2
6
(
5) were obtained (Scheme 2). In Fig. 1,
simplified sketches of the structures of 3 and
and the dimethoxyethane (dme) solvate
4
+
–
[
Na(dme) ] [Na(P Ph )(dme) ] , which was
3 2 2 3
obtained previously by crystallization from
[4]
dme, are displayed (• = P, ⊕ = Na, ꢀ = C).
Especially tetraphosphandiides, [M (P Ph )
2
4
4
(
solv) ], were intensively investigated and a
x
number of X-ray diffraction studies were per-
[5]
formed to elucidate their structures.
Fig. 1. Schematic representations of [Na (P Ph )(tmeda) ] (3), [Na (P Ph )(tmeda) ] (4), and
2
4
4
2
2
3
3
3
Due to dynamic processes and the fact
that relatively small changes in their con-
formations provoke large variations in the
+
–
[
Na(dme) ] [Na (P Ph ) (dme) ] highlighting the core-structures composed from the P atoms (•), the
3 5 2 2 3 3
sodium cations (⊕) and ipso-carbons of the phenyl rings (ꢀ).
31
31
31
P, P coupling constants, the P NMR
spectra of M (P R ) species in solution
2
4 4
are complicated and ill-defined very broad
resonances at room temperature are fre-
quently observed.[ However, these data
allowed us to identify the yellow almost in-
soluble compound obtained in the reaction
between (PhP) (or PhPCl ) with sodium in
6,7]
5
2
toluene or xylene in the absence of tmeda
as the almost solvent-free tetraphosphan-
diide, [Na (P Ph )] (3’). Th is compound
2
4
4 x
is not further degraded to smaller dianions
in the absence of additives like tmeda. Th e
triphosphandiide [Na (P Ph )(tmeda) ] (4)
2
3
3
3
is a rare example of a structurally charac-
terized compound.[ Remarkably, 4 is not
formed by reductive degradation of the tet-
raphosphandiide [Na (P Ph )(tmeda) ] (3)
8]
2
4
4
2
but by a synproportionation reaction be-
[
5d]
tween 3 and [Na (P Ph )(tmeda)] . Note
2
2
2
6
that we were not able to detect any species
which may be formulated as [Na PPh] un-
2
der any of our reaction conditions (hydro-
carbon/tmeda solvents, T u p to 140 °C).
+
Th e dme solvate [Na(dme) ] [Na
3
5
and
–
[5a]
Fig. 2. Structure of [Na (P Ph )(tmeda)] (5). A) Hydrogen atoms are omitted for clarity. B) Schematic
(
[
P Ph ) (dme) ] (see Fig. 1C)
2 2 2 6
2
2 3
3
[6]
representation of 5 highlighting the core structure composed from the P atoms (•), the sodium cations
⊕) and ipso-carbons of the phenyl rings (ꢀ). Selected bond lengths [Å] and angles [°]: Na1−P1
.796(4), Na1−P4 2.939(4), Na1−P5 2.911(4), Na2−P1 2.870(4), Na2−P3 2.852(4), Na3−P3 2.837(4),
Na3−P2 2.965(4), Na3−P6’ 2.920(4), Na4−P1 3.043(4), Na4−P2 2.911(4), Na4−P5’ 2.974(4), Na5−P4
.970(4), Na5−P6 2.998(4), Na6−P2’ 2.935(4), Na6−-P4 3.013(4), Na6−P6 2.927(4), Na6−P5 2.982(4),
P1−P2 2.160(3), P3−P4 2.148(3), P5−P5’ 2.170(5), P6−P6’ 2.152(5), Na1···C25 2.750(9), Na3···C31’
2.804(8), C1-P1-P2-C7 71.5(4), C13-P3-P4-C19 74.2(4), C25-P5-P5’-C25’ –92.3(6), C31-P6-
P6’-C31’ –86.6(5).
Li (P Ph )(tmeda) ] are the only com-
2
2
2
2
(
pounds known to date which contain the
2
2–
vicinal dianion [P Ph ] . We were now
2
2
able to determine the structure of the tmeda
2
complex 5 by an X-ray diffraction study.
Th is shows 5 to be a hexameric ionic ag-
gregate with a unique structure (Fig. 2).

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20
CHIMIA 2008, 62, No. 1/2
In this C -symmetric species, only six of
2
the twelve sodium cations (Na2, Na4, Na5
and their symmetry equivalents) are coordi-
nated to tmeda molecules. Na2 and Na5 re-
side in slightly distorted tetrahedral coordi-
nation spheres (two nitrogen, two phospho-
rus centers) while Na4 is pentacoordinated
to three phosphorus atoms and one tmeda
molecule. Th e other sodium cations, Na1,
Na3, and Na6, are tmeda free. Th e Na1 and
Na3 ions are coordinated to three phospho-
rus centers and show an additional long con-
tact (2.750 Å and 2.804 Å, respectively) to
one ipso-carbon of an adjacent phenyl group
(
see dotted lines in Fig. 2B). Na6 resides in
a strongly flattened tetrahedral coordination
sphere spanned by four P atoms. Th e Na−P
distances (2.796–3.043 Å) lie within the
usual range (for a listing see ref. [6]). Th e
P−P bond distances (2.148–2.170 Å) in the
2
–
[
Ph P ] dianions which all have a gauche
2 2
conformation (|C-P-P-C| 71.5–92.3°) are re-
markably short compared to the previously
Scheme 3. Reactions of 5 with 2,4,6-trimethylbenzoylchloride (MesCOCl) 6 and Me SiCl and
synthesis of BAP 7
reported values (>2.2 Å).[
5a,6]
Th e aggregate
is the first we observe that is not composed
from {(Na ) (P Ph ) } ion triples. In such
3
5
+
2–
2
x
x
+
an ion triple, the Na cations bridge the neg-
atively charged phosphorus atoms in form Obviously, the monoacylated product, in liquid ammonia in the presence of tert-
–
[13]
of a (flat or modestly folded) parallelogram [(MesCO)PhP-PPh] undergoes
a
fast butanol as proton source. We wondered
which is an especially stable arrangement fragmentation into the phospha-enolate whether the addition of tert-butanol under
–
for electrostatic reasons (see discussion in [PhP=CO(Mes)] which is immediately our reaction conditions would likewise al-
ref.[6]). In 5, only the sodium cation Na4 intercepted by a second equivalent of the low the in situ preparation of phenylphos-
resides in such a bridging position over one acid chloride 6. Th e other product of this
phane 14. To test this hypothesis, we reacted
2–
[
P Ph ] dianion, all other sodium cations fragmentation, phenylphosphinidene PhP, the disodium diphosphanediide 5 with two
2 2
take bridging positions between different immediately oligomerizes to (PhP) which equiv. of tert-butanol which cleanly led to
5
2
–
31
[
P Ph ] dianions. We assume that the is the other observed species (Scheme 3).
the diphosphane 12 ( P NMR: δ = –68 and
2
2
increased steric bulk of the tmeda as co-
On the other hand, trimethylsilylchlo- –72 ppm for the meso- and rac-form, re-
ligand[ is responsible for the formation of ride as electrophile reacts cleanly with 5 to spectively ) (Scheme 4). At T
9]
[14]
= 100 °C,
a larger cluster than with dme. Th e steric
yield the expected 1,2-diphenyl-1,2-disilyl- 12 reacts quantitatively with sodium metal
31
[10]
31
encumbrance lowers the coordination en- diphosphane8( PNMR:δ=–108ppm ). to give sodium(phenylphosphide) 13 ( P
[15]
thalpies of the sodium cations which in turn Th e P-P bond in 8 is easily reductively
NMR: δ = –121 ppm) ), which is proto-
search additional (longer) contacts to phos- cleaved by sodium in toluene and gives the nated by another two equiv. of tert-butanol to
phorus or carbon centers whereby the aggre- soluble monosilylated phenylphosphanide give phenylphosphane in almost quantitative
31
1
gation state increases. It is likely that larger sodium salt 9 (aggregation state x unknown) yield ( P NMR: δ = –123 ppm, triplet, J
PH
31
[11]
[16]
aggregates are generally observed with the ( P NMR: δ = –156 ppm ). Without iso- = 197.4 Hz) ). Only traces (<3%) of the
+
+
+
heavier alkali cations (M = Na – Cs ) and lation, 9 was further reacted with MesCOCl monosodium salt [Na(P Ph H)(solv)] 15
2
2
x
diphosphandiides as counter-dianions. In to give the desired bis(acyl)phosphane 7 as are observed.[17]
the corresponding lithium compounds, the the main product. Further by-products are
When MesCOCl is added slowly to this
+
–
Li , P distances are short (≈2.6 Å) which the phosphaenols 10 and 11, which were reaction mixture and the temperature is kept
gives rise to a sufficiently high electrostatic obtained as E- and Z- isomers and identified below 70 °C an almost quantitative yield
31
stabilization energy (ESP) even in a simple by their typical P NMR chemical shifts of BAP 7 is obtained. Note that the reac-
archetypical ion triple as [Li (P Ph )(tme- (E-10: δ = 196.0 ppm, Z-10: δ = 189 ppm; tion mixture contains exactly the amount
2
2
2
[6]
[12]
da)2].
E-11: δ = 149 ppm, Z-11: δ = 134 ppm ). of NaOtBu needed as base to promote the
In aggregates with M = Na – Cs, the lon- Th e O-acyl phosphaenols E/Z-10 undergo
reaction between PhPH 14 and the steri-
2
+
–
ger M ,P contacts do not sufficiently sta- a remarkable 1,2-acyl shift reaction to BAP cally congested MesCOCl 6. Weaker bases
bilize a small aggregate which is relatively 7 upon warming in toluene, however, the like NEt are ineffective. Because the reac-
3
more destabilized especially by the repul- O-silyl enolates E/Z-11 cannot be further tion of t-BuOH with sodium is slower than
–
–
sive P ,P interaction. Note that the number converted to 7 even at elevated temperature the reductive cleavage of the P−P bond in 12
+
–
of attractive M ,P contacts per additional and excess of MesCOCl. Because the con- even at elevated temperatures, the synthesis
incorporation of a M (P Ph ) unit increases tent of E/Z-11 amounts to about 15–20% of BAP 7 can be performed as a one-pot pro-
2
2
2
+
+
more rapidly than the repulsive M ,M , and of the product and furthermore Me SiCl is cedure: PhPCl is reacted with four equiv.
3
2
–
–
P ,P interactions (the exact ratio depends needed, this process for the preparation of of sodium in a toluene/tmeda mixture (100/4
[
6]
on the structural details ).
7 was abandoned.
by volume) at T = 120 °C until 5 precipi-
Brandsma et al. published a series of pa- tates as bright yellow powder. Subsequently,
When 5 is reacted with MesCOCl (6),
a 50% yield of the BAP compound 7 is pers describing the synthesis of alkali metal two equivalents t-BuOH are added, the re-
obtained and not the expected bis(acyl) phosphides, [M(PH )], from elemental phos- action kept at 120 °C until the remaining
2
diphosphane, (MesCO)PhP-PPh(COMes). phorus or PCl and lithium or sodium metal sodium completely dissolved, and addition
3

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21
CHIMIA 2008, 62, No. 1/2
forming and cleavage reactions, served as
basis for the successful development of a
new more environmentally friendly IRGA-
CURE synthesis. We are currently extend-
ing the synthetic method reported here to the
preparation of a broader range of BAPO type
photoinitiators.
5. Experimental Part
5
.1. General Techniques
All syntheses were performed in flame-
dried glassware under an atmosphere of
argon using standard Schlenk techniques.
To luene or xylene was freshly distilled from
sodium/tetraglyme/benzophenone and tme-
da was dried over calcium hydride prior to
use. Air-sensitive compounds were stored
and weighed in an argon filled glove box
Scheme 4. Efficient synthesis of phenylphosphane 14 and the bis(acyl)phosphane oxide IRGACURE
(Braun MB 150 B-G system) and reactions
819 (16)
on small scale were performed directly in the
glove box.
of MesCOCl discloses the synthesis (>90%
yield of 7). Subsequently, the added tmeda is
neutralized with a stoichiometric amount of
conc. H SO acid before 30% aqueous H O
is added (3 equiv.) at 40–50 °C to oxygenate
BAP 7 to the final product IRGACURE 819
NMR spectra were recorded on Bruker
Avance 700, 500, 400, 300, 250, 200 spec-
trometers. Th e chemical shifts (δ) are mea-
sured according to IUPAC[ and expressed
18]
2
4
2 2
1
in ppm relative to TM S, or H PO for H,
3
4
13
31
C and P, respectively. Coupling con-
(
16). Under optimized conditions, overall
stants J are given in Hertz [Hz] as absolute
values, unless specifically stated. Where a
yields as high as 90 % can be obtained.
first order analysis is appropriate, the multi-
plicity of the signals is indicated as s, d, or m
Fig. 3. Structure of PhPO(COMes)2 (16). for singlets, doublets, or multiplets, respec-
3
. Structure Determination of
IRGACURE 819 (16)
Selected bond lengths [Å] and angles [°]: P1−O1 tively. Aromatic carbons are indicated as Car
1
.475(2), P1−C1 1.797(3), P1−C7 1.895(3), when not noted otherwise.
P1−C17 1.896(3), C7−02 1.210(3), C17−O3
To our knowledge, no X-ray diffrac-
1.226(3), C7−C8 1.491(4), C17−C18 1.487(4),
tion study has been performed to elucidate
the structure of a bis(acyl)phosphane or
5.2. Synthesis of Bis(2,4,6-trimethyl-
benzoyl)phenylphosphane Oxide (16)
O1-P1-C1 114.7(2), O1-P1-C7 111.9(1), O1-P1
C17 116.3(1), C1-P1-C7 110.1(1), C1-P1-C17
bis(acyl)phosphane oxide derivative. Th e
To luene (100 ml) and tmeda (4.0 ml,
1
6
05.9(1), C7-P1-C17 96.3(1), O2-C7-P1-O1
3.9(1), O3-C17-P1-O1 –174.4(1).
structures of several mono(acyl) substituted
26.68 mmol) are mixed and deoxygenated.
Na (2.06 g, 89.52 mmol) is added and the
[17]
phosphorus compounds are known. We
have performed an X-ray diffraction study
with a crystal of 16 grown from a saturated
mixture is heated for 30 min. at T = 120 °C.
Subsequently, PhPCl (4.01 g, 22.41 mmol)
2
toluene solution. A plot of the structure is the lengthening of the P-Cacyl bonds and the is added in one portion. Th e mixture turns
given in Fig. 3, selected bond lengths and special arrangement of the CO-PO-CO chro- pale yellow and a colorless precipitate starts
angles are given in the Fig. legend.
Of interest are the phosphorus acyl car- the reactive excited triplet state is populated a bright-yellow substance precipitates and
bonbondlengths,P1−C7andP1−C17,which and decays in an α-cleavage reaction. the supernatant solution is colorless. To this
suspension, t-BuOH (3.32 g, 44.85 mmol, 2
Th ese bonds in 16 are indeed remarkably equiv.) is added drop-wise over a period of
mophore, relate to the efficiency by which to form. Th e mixture is heated (3–5 h) until
[1a−h]
are broken in the photolytic process.
long (1.895(3)/1.896(3) Å) especially when 4. Conclusion
compared to the distance between P1 and the
30 min at T = 100 °C. Th e yellow precipitate
dissolves and the solution turns orange.After
ipso-carbon atom C1 of the phenyl group,
In summary, a straightforward one-pot about 20 min heating at 120 °C, all sodium
2
31
which is likewise sp hybridized: the P1−C1 synthesis of bis(2,4,6-trimethylbenzoyl) metal is consumed. A P NMR spectrum
bond (1.797(3) Å) is about 0.1 Å shorter phenyl phosphane oxide 16, the commercial indicates the presence of >95% PhPH (14)
2
and in the expected range. In other monoa- photoinitiator IRGACURE® 819 , could as phosphorus-containing species which is
TM
cylphosphane oxides the corresponding be developed. Th e new protocol avoids the
reacted with 2,4,6-trimethylbenzoylchloride
[
17]
P−C
bonds (1.808−1.872 Å ) are also use of ethereal solvents and employs sodi- 6 (8.19 g, 44.8 mmol) such that the tempera-
acyl
elongated but slightly shorter than in 16. um as metal of lower ecotoxicity compared ture is kept below 70 °C. Subsequently, conc.
Th e CO-PO-CO chromophore in 16 has a to lithium. Furthermore, the yield could be H SO (1.48 ml, 26.68 mmol) is slowly add-
2
4
syn,anti-conformation, i.e. the C7=O2 group improved significantly. Th e detailed knowl-
ed at room temperature in order to neutralize
points to the same side as the P1=O1 bond edge of the molecular components like the tmeda. In the final step of the synthesis, 30%
(
torsion angle 63.9°) while the C17=O3 hexameric ion aggregate [Na (P Ph )(tme- aqueous hydrogen peroxide (6.9 ml, 67.5
2 2 2
group points to the opposite side (torsion da)] (5) which are encountered along the mmol, 3 equiv) is added whereby the tem-
6
angle –174.4°). It remains to be seen, in complex reaction path when PhPCl reacts perature is kept at 45–55 °C. For work up of
2
how far these ground state properties, i.e. with sodium in consecutive reductive bond the reaction mixture, H O (10 ml) is added,
2

HOT TOPICS
22
CHIMIA 2008, 62, No. 1/2
the organic phase is separated and washed cam.ac.uk/conts/retrieving.html (or from [8] For the structure of the parent dianion
2
–
[
P H ] see: N. Korber, J. Aschenbrenner,
twice with a 10% sodium hydrogencarbon- the Cambridge Crystallographic Data Cen-
ate solution (10 ml) and subsequently twice tre, 12 Union Road, Cambridge CB21EZ,
3 3
J. Chem. Soc., Dalton Trans. 2001, 1165.
[
9] D. B. Collum, Acc. Chem. Res. 1992, 25,
with H O (10 ml). Th e organic phase is dried
UK; fax: (+44)1223-336-033; or deposit@
over anhydrous sodium sulfate and all vola- ccdc.cam.ac.uk).
2
4
48.
[
10] H. Schumann, R. Fischer, J. Organomet.
tile materials are evaporated under vacuum.
Chem. 1975, 88, C13.
Th e initially formed thick yellow oil starts to
Acknowledgements
[
11] U. Englich, K. Hassler, K. Ruhlandt-Senge,
Th is work is the result of a fruitful
solidify to give a brightly yellow substance
which is washed with hexanes and subse-
quently dried under vacuum to give crude
F. Uhlig, Inorg. Chem. 1998, 37, 3532.
collaboration between the E TH Zürich and the
[12] V. A. Wright, D. P. Derek, Angew. Chem.,
Ciba Specialty Chemicals Inc which funded this
research.
Int. Ed. 2002, 41, 2389.
[13] a) L. Brandsma, N. Gusarova, S. Arbuzova,
1
6 (7.9 –8.4 g, 85–90% yield, >95% pure by
H NMR).An analytical pure sample (5.88 g
62.7% yield) can be obtained by recrystal-
1
B. Tr ofimov, Phosphorus, Sulfur Silicon
Relat. Elem. 1996, 111, 807; b) L.
Received: November 29, 2007
=
Brandsma, N. K. Gusarova, A. V. Gusarov,
lization from a concentrated TH F solution.
[
1] For investigations of the photophysical
1
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36.0 (d, J = 41.9 Hz, Mes C1), 133.2 (d,
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1
5.0554(2), c = 8.6688(1) Å, α= 90.000(0),
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4
x
W. Hong-Gen, W. Ru-Ji, Jiegou Huaxue
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(
2
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[
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