Complexes with a monohapto bound phosphorus tetrahedron and phosphaalkyne

Article abstract of DOI:10.1021/om9806794

The reaction of white phosphorus with the coordinatively unsaturated [M(CO)₃(PR₃)₂] complexes (M = Mo, W; R = Cy, Prⁱ) yields the compounds [M(CO)₃-(PR₃) ₂(η¹-P₄)] in which the P ₄-tetrahedron is end-on bonded to the metal. In the same manner reacts Ar′C≡P (Ar′ = C₆H₂Bu ^t₃-2,4,6) with this complex to give [W(CO) ₃-(PCy₃)₂(η¹-P≡CAr′) ]. The X-ray structures of the products are discussed, and for the P ₄-unit in [W(CO)₃(PCy₃)₂(η ¹-P₄)] the librational analysis was performed to correct their translational and rotational motions.

Full text of DOI:10.1021/om9806794

5916
Organometallics 1998, 17, 5916-5919
Com p lexes w ith a Mon oh a p to Bou n d P h osp h or u s
Tetr a h ed r on a n d P h osp h a a lk yn e1
Thomas Gro¨er, Gerhard Baum, and Manfred Scheer*,2
Institut fu¨r Anorganische Chemie der Universita¨t Karlsruhe, D-76128 Karlsruhe, Germany
Received August 7, 1998
Summary: The reaction of white phosphorus with the
coordinatively unsaturated [M(CO)3(PR3)2] complexes (M
) Mo, W; R ) Cy, Pri) yields the compounds [M(CO)3-
(PR3)2(η1-P4)] in which the P4-tetrahedron is end-on
bonded to the metal. In the same manner reacts Ar′CtP
[FeH(η1-PtCBut)(dppe)2][BPh4] 3b9 with a η1-ligated
phosphaalkyne are structurally characterized. Recently,
Bedford et al. reported the synthesis of the complex
[Ru(η1-PtCAr′)(CO)2(PPh3)2] suggesting an η1-coordina-
tion of the phosphaalkyne PtCAr′ (Ar′ ) C6H2But -
3
(Ar′ ) C6H2But -2,4,6) with this complex to give [W(CO)3-
3
2,4,6) to the central ruthenium atom, which was con-
(PCy3)2(η1-PtCAr′)]. The X-ray structures of the products
are discussed, and for the P4-unit in [W(CO)3(PCy3)2(η1-
P4)] the librational analysis was performed to correct
their translational and rotational motions.
firmed by spectroscopic data.10
Interest has been focused on unsubstituted group 15
ligands bonded to transition metal complexes for several
years.3 Most of the Px ligand complexes are formed by
reaction of white phosphorus with the appropriate
transition metal complexes. However, only one type of
compounds with a monohapto bound P4-tetrahedron is
known, the [(η1-P4)M(np3)] (1) (M ) Ni (a ), Pd (b); np3
) N(CH2CH2PPh2)3) complexes reported by Sacconi and
co-workers.4 Moreover, Ginsberg and Lindsell suggested
the occurrence of a side-on coordinated P4-unit in
compounds of the type [(R3P)2MCl(η2-P4)] (2) (M ) Rh
(a ), Ir (b)).5 The nature of bonding to P4 in the latter
complexes was established to be a side-on coordination
of a P-P edge of the intact P4 tetrahedron. The long
P-P bond of 2.4616(22) Å, however, rather gives evi-
dence for an open edge, where a tetraphosphabicyclo-
butane coordinates to a metal(III) center. Other reac-
tions of transition metal complexes with white phos-
phorus lead to transformation of the tetrahedral P4-
unit.3,6 In a similar manner, the number of mononuclear
coordination complexes formed with untransformed
phosphaalkyne remains small.7 Among them only the
complexes trans-[Mo(η1-PtCAd)2(depe)2] 3a 8 and trans-
We found that in both respectssforming η1-complexes
of P4 as well as of phosphaalkynessthe electronically
and coordinatively unsaturated compounds [M(CO)3-
(PCy3)2] (M ) Mo, W), serve as the ideal starting
material. These complexes are known to coordinate
numerous small molecules such as H2 and N2.11
The reaction of [M(CO)3(PR3)2] with 1 equiv of P4 in
toluene at -78 °C leads to the capture of one phosphorus
lone pair yielding the η1-bonded P4 complexes [M(CO)3-
(PR3)2(η1-P4)] (4a -c) (4a : M ) W, R ) Cy; 4b: M ) W,
R ) Pri; 4c: M ) Mo, R ) Cy). These complexes are
stable in solution (hexane, toluene) up to 0 °C, and then
they decompose to the 18 VE compounds [M(CO)4-
(PR3)2]12 (5a ,b) (M ) W, Mo) and P4. However at low
temperatures 4a -c crystallize as orange-yellow com-
pounds. The air-sensitive solids are stable at ambient
temperatures under argon. They are soluble in common
organic solvents.
(1) Dedicated to Prof. Dr. O. J . Scherer in occasion of his 65th
birthday.
(2) To whom the correspondence should be addressed. Tel.:
+49(0) 721 608 3088. Fax: +49 (0) 721 662119. E-mail: mascheer@
achibm6.chemie.uni-karlsruhe.de.
(3) (a) Scheer, M.; Herrmann, E. Z. Chem. 1990, 30, 41. (b) Scherer,
O. J . Angew. Chem., Int. Ed. Engl. 1990, 29, 1137.
(4) (a) Dapporto, P.; Midollini, S.; Sacconi, L. Angew. Chem., Int.
Ed. Engl. 1979, 18, 510. (b) Dapporto, P.; Sacconi, L.; Stoppioni P.;
Zanobini, F. Inorg. Chem. 1981, 20, 3834.
The structure of 4a reveals the 18-valence-electron
complex [W(CO)3(PCy3)2(η1-P4)] with a η1-bonded P4
tetrahedron (Figure 1). The distance of the coordinated
(5) Ginsberg, P.; Lindsell, W. E.; McCullough, K. J .; Sprinkle, C.
R.; Welch, A. J . J . Am. Chem. Soc. 1986, 108, 403.
(6) (a) Scheer, M.; Schuster, K.; Becker, U. Phosphorus, Sulfur,
Silicon 1996, 109-110, 141. Scheer, M.; Becker, U. Chem. Ber. 1996,
129, 1307. (c) Scheer, M.; Becker, U. J . Organomet. Chem. 1997, 545-
546, 451.
(7) (a) Nixon, J . F. Chem. Rev. 1988, 88, 1327. (b) Binger, P. In
Multiple Bonds and Low Coordination in Phosphorus Chemistry;
Regitz, M., Scherer, O. J ., Eds.; G. Thieme Verlag: Stuttgart, 1990; p
90ff. (c) Nixon, J . F.; Chem. Ind. 1993, 7, 404. (d) Nixon, J . F. Chem.
Soc. Rev. 1995, 319. (e) Nixon, J . F. Coord. Chem. Rev. 1995, 95, 201-
258.
(9) (a) Nixon, J . F.; Meidine, M. F.; Lemos, M. A. N. D. A.; Hitchcock,
P. B.; Pombeiro, A. J . L. J . Chem. Soc, Dalton, Trans. 1998, in press.
(b) Hitchcock, P. B.; Amelia, M.; Lemos, M. A. N. D. A.; Meidine, M.
F.; Nixon, J . F.; Pombeiro, A. J . L. J . Organomet. Chem. 1991, 402,
C23.
(10) Bedford, B.; Hill, A. F.; Wilton-Ely, J . D. E. T.; Francis, M. D.;
J ones, C. Inorg. Chem. 1997, 36, 5142.
(11) Wassermann, J .; Kubas, G. J .; Ryan, R. R. J . Am. Chem. Soc.
1986, 108, 2294.
(8) Hitchcock, P. B.; Maah, M. J .; Nixon, J . F.; Zora, J . A.; Leigh, G.
J .; Bakar, M. A. Angew. Chem., Int. Ed. Engl. 1987, 26, 474.
(12) Moers, F. G.; Reuvers, J . G. A. Recl. Trav. Chim. Pays-Bas.
1974, 93, 246.
10.1021/om9806794 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 11/20/1998

Notes
Organometallics, Vol. 17, No. 26, 1998 5917
F igu r e 1. Molecular structure of 4a (ellipsoids drawn at
50% probability level). Selected bond distances (Å) and
angles (deg) [by librational analysis corrected distances]:
W-P(1) 2.520(2), W-P(2) 2.525(2), W-P(3) 2.463(2), P(3)-
P(4) 2.162(3) [2.187], P(3)-P(5) 2.181(3) [2.199], P(3)-P(6)
2.172(3) [2.199], P(4)-P(5) 2.191(3) [2.225], P(4)-P(6)
2.195(5) [2.238], P(5)-P(6) 2.183(3) [2.214], P(1)-W-P(2)
179.29(5), C(2)-W-P(3) 174.5(2), C(1)-W-C(3) 171.9(3).
phosphorus to the central tungsten atom is of 2.463(2)
Å, which is shorter than the P-W bond lengths of the
two tricyclohexylphosphine phosphorus atoms which
increase from 2.463(1) and 2.494(1) Å in the starting
complex to 2.520(2) and 2.525(2) Å upon coordination
of P4.
There are substantial differences in the bond dis-
tances within the P4-tetrahedron compared to those in
1a reported by Sacconi and co-workers.4a The basal P-P
bonds [P(4)-P(5), P(5)-P(6), P(6)-P(4)] in 4a vary
between 2.183(3) Å and 2.195(5) Å and hence tend to
be longer than the apical P-P distances [P(3)-P(4),
P(3)-P(5), P(3)-P(6)], which are in the range of 2.162(3)
Å to 2.181(3) Å. Whereas in 1a was found the basal P-P
distances at 2.09(3) Å to be shorter than the apical P-P
bond lengths at 2.20(3) Å (due to symmetry reasons, all
basal as well as apical distances are equal). The
structure of 1a was established at ambient temperature
without a librational analysis. For the X-ray structure
of 4a at 200 K, the rigid-body model was applied for
the P4 unit to correct the shortened bond length due to
translational and rotational motions of the P atoms.13
14
By using a “dummy atom“ as described for â-P4 the
iterations converged to R ) 0.020 with a lengthening
of the P-P bond distance between 1.8 and 4.3 pm
(Figure 1). The analysis shows the same relation of the
P-P bonds, longer basal and shorter apical bonds. These
experimental features are furthermore supported by
recent MP2/6-31G(d,p) calculations, revealing at the
“end-on” H+ attached P4 tetrahedron longer basal P-P
bonds of 2.269 Å and shorter apical ones of 2.122 Å.15
31P NMR data of the isostructural complexes 4a -c
reveals three different groups of signals as an A2MX3
spin system [A ) P(1), P(2); M ) P(3); X ) P(4), P(5),
P(6)], two of which, a doublet and a quartet, are
assignable to the η1-bound P4-tetrahedron. No WP-
coupling can be observed in the quartet resonance of
the coordinated PM-atom, probably due to the similarity
between PP- and WP-coupling constants, which causes
the set of satellites to be obscured by the main signals.
F igu r e 2. Molecular structure of 5a (ellipsoids drawn at
30% probability level). Selected bond distances (Å) and
angles (deg): W-P(2) 2.506(3), W-P(1) 2.525(3), W-C(1)
2.129(13), W-C(2) 2.064(13), W-C(3) 2.018(14), W-C(4)
1.99(2), P(2)-W-P(1) 170.93(8), C(4)-W-C(2) 170.0(4),
C(3)-W-C(1) 177.9(5), C(2)-W-C(1) 96.6(4).
Hz, reflect a relatively high s-character in the P-P
bonds of the P4 tetrahedron. The third group of signals
(PA) can be assigned to the phosphine phosphorus atoms
and bears a set of satellites due to a WP-coupling. The
spectra of 4a ,b reveal a doublet with a very small
2J P(A)P(M) of 11 and 20 Hz, respectively.
The molecular structure of the complex 5a is shown
in Figure 2. For the isostructural Mo complex 5b, the
X-ray structural analysis was also carried out.16 The
cyclohexyl substituents are eclipsed with a slightly bent
P-M-P axis. In contrast to this, the Cy groups in the
P4-complex 4a are staggered with an almost linear
P(2)-W-P(1) arrangement.
1
The J P(M),P(X) values, ranging from 206 (4b) to 185 (4c)
(13) Dunitz, J . D.; Maverick, E. F.; Trueblood, K. N. Angew. Chem.,
Int Ed. Engl. 1988, 27, 880.
(14) Simon, A.; Borrmann, H.; Horakh, J . Chem. Ber./ Recueil 1997,
130, 1235.
(15) Abboud, J .-L. M.; Herreros, M.; Notario, R.; Esseffar, M.; Mo´,
O.; Ya´n˜ez, M. J . Am. Chem. Soc. 1996, 118, 1126.
(16) Recently, Alyea et al. described the X-ray structure of the
solvent-free Mo complex 5b: Alyea, E. C.; Ferguson, G.; Kannan, S.
Acta Crystallogr. C 1996, 52, 765.

5918 Organometallics, Vol. 17, No. 26, 1998
Notes
Ta ble 1. Cr ysta llogr a p h ic Da ta for 4a a n d 5a ,b
4a ‚0.5C7H8 5a ‚0.5C7H8
C42.5H70O3P6W C43.5H70O4P2W
5b‚0.5C6H6
C43H69O4P2Mo
formula
formula weight
cryst size, mm
T, K
998.15
902.79
807.86
0.15 × 0.15 × 0.08
0.15 × 0.04 × 0.02
0.12 × 0.08 × 0.02
200(1)
203(2)
200(1)
space group
crystal system
a, Å
b, Å
c, Å
P1h (no. 2)
P1h (no. 2)
P1h (no. 2)
triclinic
10.913(2)
14.150(3)
14.807(4)
65.63(2)
83.34(2)
83.03(2)
2061.9(7)
2
triclinic
triclinic
9.518(2)
10.096(2)
24.217(5)
92.54(3)
100.13(3)
96.20(3)
2272.6(8)
2
10.996(2)
14.247(3)
14.799(4)
66.02(2)
82.91(2)
82.92(2)
2089.5(7)
2
R, deg
â, deg
γ, deg
V, Å3
Z
dc, g/cm3
µc, cm-1
radiation (λ, Å)
diffractometer
2θ range, deg
hkl range
1.459
27.89
1.435
28.80
1.301
4.35
Mo KR (0.71073)
STOE IPDS
4.40 e 2Θ e 52.26
-11 e h e 11, -12 e k e 9,
-29 e l e 28
6855/0/480
5866 (Rint ) 0.0234)
1.067
Mo KR (0.71073)
STOE IPDS
4.62 e 2Θ e 52
-11 e h e 13, -17 e k e 13,
-18 e l e 15
5873/14/446
4207 (Rint ) 0.0611)
0.938
Mo KR (0.71073)
STOE IPDS
3.74 e 2Θ e 52
-13 e h e 13, -17 e k e
17-18 e l e 18
7481/0/458
6042 (Rint ) 0.0363)
1.007
0.0313, 0.0734
0.0454, 0.0776
0.603, -0.339
data/restraints/parameters
independent reflections with I > 2σ(I)
goodness-of-fit on F2
R1,a wR2 (I > 2σ(I))
0.0418, 0.1037
0.0519, 0.1097
1.250, -1.238
0.0525, 0.1168
0.0815, 0.1266
0.895, -1.488
b
R1,a wR2 (all data)
b
largest diff peak, hole, e/Å3
R ) ∑|F0| - |Fc||/∑|F0|. wR2 ) [∑ω(F0 - Fc2)2]/[∑(F02)2]1/2; ω-1 ) σ2(F02) + a(P)2 + bP; P ) [F0 + 2Fc2]/3.
a
b
2
2
Addition of the phosphaalkyne PtCAr′ (Ar′ ) C6H2-
But -2,4,6) to [M(CO)3(PCy3)2] (M ) W, Mo) in hexane
3
produces an orange precipitate of [M(CO)3(PCy3)2(η1-
PtCAr′)] (6a ,b),17 which is insoluble in nonpolar sol-
vents, but slightly soluble in toluene, CH2Cl2, and THF.
The mass spectrum of 6b reveals the molecular ion,
while 6a shows significant fragmentation assignable to
the free phosphaalkyne and the complex fragment
[W(CO)3(PCy3)2]+. 31P{1H} NMR spectra of 6 reveal a
doublet at δ 29.6 and 54.1 ppm, respectively, assigned
to the two equivalent phosphine phosphorus atoms and
a triplet at δ 24.4 and 57.0 ppm, respectively, due to
the phosphorus atom of the η1-coordinated PtCAr′, the
two showing mutual PP-coupling of 25 and 31 Hz,
respectively. In the X-ray structure analysis the poor
quality of the very small crystals of 6a led to significant
residual electron density at the phosphine phosphorus
atoms of the PCy3 groups and hence did not allow the
complete refinement of its structure. However, the
position of all desired atoms could be determined and
clearly reveals the monohapto coordination of PtCAr′
to the tungsten atom (d(W-PC) ) 2.390(5) Å, d(PtC)
) 1.54(2) Å, Figure 3). To the best of our knowledge 6a
is one of the very rare examples for the coordination
chemistry of the “supermesityl” phosphaalkyne
PtCAr′10,18 and for a structurally characterized η1-
ligated phosphaalkyne.3
F igu r e 3. Molecular structure of 6a (ellipsoids drawn at
30% probability level). Selected bond distances (Å) and
angles (deg): W-P(1) 2.390(5), W-P(2) 2.523(5), W-P(3)
2.510(5), P(1)-C(4) 1.54(2), P(1)-W-P(3) 92.4(2), P(1)-
W-P(2) 91.5(2), P(3)-W-P(2) 175.1(2), C(4)-P(1)-W
179.3(7), C(5)-C(4)-P(1) 178(2).
Exp er im en ta l Section
In conclusion, the reactivity of [M(CO)3(PR3)2] toward
Lewis-base, diminished by the steric influence of its
bulky phosphine ligands, allows the smooth formation
of complexes with unusual η1-coordination.
Gen er a l Com m en ts. All reactions were performed under
an Ar atmosphere using standard Schlenk techniques. Sol-
vents were dried prior to use: toluene over Na/benzophenone,
hexane over LiAlH4. Phosphaalkynes PtCAr′,19 PtCBut 20 as
well as the complexes [M(CO)3(PR3)2] (M ) W, Mo; R ) Cy,
Pri)11 were prepared according to modified literature methods.
(17) Furthermore the reaction of ButCtP with [W(CO)3(PCy3)2]
leads to a mixture of products inseparable by chromatography. The
31P{1H} NMR studies reveal resonances indicating primary products
with oligomerized phosphaalkynes. Within the resonances a doublet
at δ 25.4 ppm and a triplet at δ 18.2 ppm with a small PP-coupling of
4.4 Hz appear, which can be assigned to the compound [W(CO)3(PCy3)2-
(η1-PtCBut)] (6c).
(19) Ma¨rkl, G.; Sejpka, H. Tetrahedron Lett. 1986, 27, 171. Seipka,
H. Ph.D. Thesis, University of Regensburg, 1987.
(20) Ro¨sch, W.; Alspach, T.; Bergstra¨sser, U.; Regitz, M. In Synthetic
Methods of Organometallic and Inorganic Chemistry; Herrmann, W.
A., Ed.; Thieme Verlag: Stuttgart, 1996; p 13.
(18) Kramkowski, P.; Scheer, M. J . Organomet. Chem. 1998, 553,
511-516.

Notes
Syn th esis of [M(CO)3(P R3)2(η1-P 4)] (4a -c). To a solution
Organometallics, Vol. 17, No. 26, 1998 5919
2
δ 7.42 (s, 2H). 31P{1H} NMR (THF-d8): δ 54.1 (d, J PP 31 Hz),
2
of [M(CO)3(PR3)2] (M ) W, R ) Cy: 140 mg, 0.17 mmol) in
toluene at -78 °C was added 1 equiv of P4 (21 mg, 0.17 mmol)
in toluene over a period of 30 min. On warming up to -20 °C
the solution changed color from violet to green. On concentrat-
ing the solution in vacuo and storing it at -30 °C, orange-
yellow crystalline product could be obtained. Solutions of 4a -c
decompose above 0-5 °C, whereas the crystalline solids are
stable under argon at ambient temperature. 4a (65% yield):
31P{1H} NMR [101.26 MHz, 244 K, toluene-d8, A ) P(1), P(2);
M ) P(3); X ) P(4), P(5), P(6)]: δ 26.5 (PA) (d, 11 Hz, 1J WP 262
δ 57.0 (t, J PP 31 Hz). IR (KBr): 1979 s, 1960 w, 1881 vs cm-1
[ν (CO)]. EI MS: m/z (%) ) 1030.56 (3) [M]+, 742.34 (12) [M -
PCAr′]+.
X-r a y Str u ctu r e Deter m in a tion a n d Deta ils of Refin e-
m en t. Data were collected on a Stoe IPDS diffractometer using
Mo KR (λ ) 0.71069 Å) radiation, no absorption corrections
were performed. Machine parameters, crystal data, and data
collection parameters are summarized in Table 1. The struc-
tures were solved by direct methods using SHELXS-8621a and
a full-matrix-least-squares refinement on F2 in SHELXL-9321b
with anisotropic displacement for non-H atoms. Hydrogen
atoms were placed in idealized positions and refined isotro-
pically according to the riding model.
[W(CO)3(PCy3)2(η1-PtCAr′)] (6a): C58H62O3P3W, M ) 1083.83,
crystal dimensions 0.2 × 0.15 × 0.03 mm, triclinic, space group
P1h, unit cell parameters a ) 10.114(2), b ) 16.904(3), c )
19.054(4) Å, R ) 92.11(3), â ) 101.71(3), γ ) 97.69(3)°, Z ) 2,
V ) 3154.2(11) Å3, T ) 200(1) K, Dc ) 1.176 mg m-3, µ(Mo KR)
) 19.44 cm-1, 14230 independent reflections (2θmax ) 56.66°),
8115 observed with Fo g 4σ (Fo); 296 parameter, R1 ) 0.1584,
wR2 ) 0.4074. Only the W, P, and the C(4)-atom were refined
anisotropically. Several attempts to receive crystals of better
quality of 6a and 6b, respectively, remained unsuccessful.
1
Hz), δ -422 (PM) (q, 1J MX 204 Hz, 2J AM and J WP not resolved);
1
δ -473 (PX) (d, J MX 204 Hz). IR (KBr, cm-1): 1951 s, 1922 w,
1836 vs [ν (CO)]. EI MS: m/z (%) ) 952.6 (1) [M]+, 828.7 (1.5)
[M-P4]+, 123.9 (74) [P4]. 4b (58% yield): 1H NMR (250.13
MHz, 244 K, toluene-d8): δ 1.12 (dd, 36H, J HH 7.2 Hz, J PH 12.9
Hz), δ 2.10 (sept, 6H, J HH 7.2 Hz). 31P{1H} NMR (101.26 MHz,
244 K, toluene-d8): δ 33.7 (PA) (d, 2J AM 20 Hz, 1J WP 263.9 Hz),
2
1
δ -422.6 (PM) (q, J AM 20 Hz, J MX 206 Hz,), δ -476.9 (PX) (d,
1J MX 206 Hz, J WP not resolved). IR (KBr, cm-1): 1964 s, 1923
1
w, 1844 vs [ν (CO)]. EI MS: m/z (%) ) 656.1 (5) [M - 2CO]+,
588.2 (50) [M - P4]+. 4c (62% yield): 31P{1H} NMR (101.26
MHz, 244 K, toluene-d8): δ 51.2 (PA) (s), δ -400.2 (PM) (q, 1J MX
1
185 Hz), δ -480.0 (PX) (d, J MX 185 Hz). EI MS: m/z (%) )
742.4 (45) [M - P4]+.
Syn th esis of [M(CO)3(P Cy3)2(η1-P tCAr ′)] (6a ,b). To a
solution of [M(CO)3(PCy3)2] (M ) W: 166 mg, M ) Mo: 148
mg, 0.2 mmol) in hexane at -20 °C was added an equimolar
solution of PtCAr′ (58 mg, 0.2 mmol) in hexane dropwise over
a period of 30 min. The violet solution changed color to bright
red, and upon being warmed, a microcrystalline orange
precipitate formed, which was filtered off, washed with hexane,
and dried in vacuo (yields are about 76-85%). 6a : 1H NMR
(250.13 MHz, 300 K, THF-d8): δ 1.26-2.21 (m, 93H), δ 7.35
(s, 2H). 31P{1H} NMR (101.26 MHz, 300 K, THF-d8): δ 24.4
Ack n ow led gm en t. The authors thank the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen
Industrie for financial support.
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
atomic coordinates, H-atom parameters, bond distances and
anisotropic displacement parameters, and fully labeled figures
for 4a , 5a ,b, and 6a (38 pages). Ordering information is given
on any current masthead page.
2
1
2
1
(t, J PP 25 Hz, J WP 280 Hz), δ 29.6 (d, J PP 25 Hz, J WP 260
Hz). IR (KBr): 1975 w, 1965 s, 1859 vs cm-1 [ν (CO)]. EI MS:
m/z (%) ) 828.75 (1) [M - PCAr′]+, 288.2 (72) [PCAr′]+. 6b:
1H NMR (250.13 MHz, 300 K, THF-d8): δ 1.25-2.20 (m, 93H),
OM9806794
(21) (a) Sheldrick, G. M. SHELXS-86, University of Go¨ttingen, 1986.
(b) Sheldrick, G. M. SHELXL-93, University of Go¨ttingen, 1993.