3-Hexyne complexes of molybdenum(II) and tungsten(II). Crystal structures of [WI2(CO)(PPh3)2(η2-EtC 2Et)] and [WI2(CO){Ph2P(CH2)3PPh 2}(η2-EtC2Et)]

Article abstract of DOI:10.1515/znb-1999-0204

Treatment of [MI₂(CO)₃(NCMe)₂] (M = Mo, W) with two equivalents of EtC₂Et in CH₂Cl₂ at 0°C yields the bis(3-hexyne) complexes [MI₂(CO)(NCMe)(η²-EtC₂Et)₂] (1 and 2). Complexes 1 and 2 react with two equivalents of PPh₃ in CH₂Cl₂ to give the complexes [MI₂(CO)(PPh₃)₂ (η²-EtC₂Et)] (3 and 4). The molecular structure of 4 (M = W) has been crystallographically determined and has a pseudo-octahedral geometry with the two PPh₃ ligands trans to each other with the two cis-iodo-ligands, which together with the carbonyl and 3-hexyne ligand are occupying the equatorial plane. Reaction of 1 and 2 with an equimolar amount of Ph₂P(CH₂)_nPPh₂ (for M = Mo, n = 1; for M = W, n = 1 to 6) in CH₂Cl₂ affords the mono(3-hexyne) complexes [MI₂(CO){Ph₂P(CH₂)_nPPh ₂}(η²-EtC₂Et)] (5 - 11). The tungsten complex [WI₂(CO){Ph₂P(CH₂)₃PPh ₂}(η²-EtC₂Et)] (8) has also been crystallographically characterised and has cis-phosphorus atoms in the equatorial plane with the carbonyl and one of the iodo-ligands, with the other iodo-ligand and the 3-hexyne occupying the axial sites.

Full text of DOI:10.1515/znb-1999-0204

3-Hexyne Complexes of Molybdenum(II) and Tungsten(II).
Crystal Structures of [WI2(CO)(PPh (r/2-EtC Et)] and
[WI2(CO){Ph2P(CH2)3PPh2}(»72-EtC2Et)]
3
)2
2
Mutlaq Al-Jahdalia, Paul K. Baker3’*, Michael G. B. Drewb’*
a Department of Chemistry, University of Wales, Bangor, Gwynedd, LL57 2UW, UK
b Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6 AD, UK
Z. Naturforsch. 54 b, 171-178 (1999); received August 13, 1998
3-Hexyne Complexes, Molybdenum(II), Tungsten(II)
Treatment of [Ml2(CO)3(NCMe)2] (M = Mo, W) with two equivalents of EtC2Et in CH2CI2 at
0°C yields the bis(3-hexyne) complexes [MI2(CO)(NCMe)(r7'-EtC2Et)2] (1 and 2). Complexes
1 and 2 react with two equivalents of PPI13 in CH2CI2 to give the complexes [Ml2(CO)(PPh;?)2
(772-EtC2Et)] (3 and 4). The molecular structure of 4 (M = W) has been crystallographi-
cally determined and has a pseudo-octahedral geometry with the two PPh3 ligands trans to
each other with the two m-iodo-ligands, which together with the carbonyl and 3-hexyne
ligand are occupying the equatorial plane. Reaction of 1 and 2 with an equimolar amount
of Ph2P(CH2)«PPh2 (for M = Mo, n - 1; for M = W, n = 1 to 6 ) in CH2CI2 affords the
mono(3-hexyne) complexes [Ml2(CO){Ph2P(CH2)nPPh2}(f?2-EtC2Et)] (5 - 11). The tungsten
complex [Wl2(CO){Ph2P(CH2)3PPh2}(r?2-EtC2Et)] (8) has also been crystallographically char-
acterised and has m-phosphorus atoms in the equatorial plane with the carbonyl and one of the
iodo-ligands, with the other iodo-ligand and the 3-hexyne occupying the axial sites.
Introduction
In 1988 [25], we reported the synthesis and X-
ray crystal structures of the tungsten bis(alkyne)
complexes [WI2(CO)(NCMe)(/y2 -RC2R)2] (R
Me, Ph). Very recently, [26] we have also described
the synthesis and crystal structures of the related
molybdenum complexes [MoI2(CO)(NCMe)(?72-
The ability of alkyne ligands to act as four-elec-
tron donor ligands to transition-metal centres has
been well illustrated in the alkyne complexes of
molybdenum(II) and tungsten(II) [1,2]. Although
a number of 2 -butyne, methylpropyne, pheny-
lacetylene and related alkyne complexes of molyb-
denum ^) and tungsten(II) have been prepared
[1 - 20], very few 3-hexyne derivatives have been re-
ported; these include the dimeric tungsten complex
=
RC2R)2] (R
=
Me, Ph). The chemistry of
[MI2(CO)(NCMe)(772-RC2R)2] (M = Mo, W; R =
Me, Ph) with both neutral and anionic ligands
has been studied in detail [2, 27]. In this pa-
per we describe the first 3-hexyne diiodo-com-
plexes [MI2(CO)(NCMe)(772-EtC2Et)2] (M = Mo,
W) and their reactions with phosphines. The crys-
tal structures of [WI2(CO)(PPh3)2(ry2-EtC2Et)] and
[WI2(CO){Ph2P(CH2 PPh2} (rj1-EtC2Et)] are also
discussed.
[{W(//-Br)Br(CO)072-EtC2Et)2}2] [21], molybde-
num dichloro- and dibromo-phosphine complexes
[MoX2(CO)L2(7/2-EtC2Et)] (X = Cl, L = PPh3;
X
= Br, L = PEt3, PPh3; X = Cl, Br, L2 =
dppe) [2 2 ] and the bis(dialkyldithiocarbamate)
complexes [Mo(CO)(S2CNEt2)2(772-EtC2Et)] [23]
and [Mo(772-PhC2H)(?72-EtC2Et)(S2CNMe2)2] [24].
None of the above 3-hexyne complexes have been
crystallographically characterised, and until this
work no diiodo-3-hexyne complexes of molybde-
num^!) and tungsten(II) have been reported.
Experimental
Physical measurements and instruments
Elemental analyses (C, H and N) were determined
by Glyn Connolly (Department of Chemistry, University
of Wales, Bangor) using a Carlo Erba Elemental Anal-
yser MOD 1108 (using helium as a carrier gas). Infrared
spectra were obtained as thin CHCI3 films between NaCl
plates and recorded on a Perkin-Elmer 1430 ratio record-
ing IR spectrophotometer. 'H, 13C and MP NMR spectra
* Reprint requests to Dr. P. K. Baker or Dr. M. G. B. Drew.
0932-0776/99/0200-0171 $ 06.00 © 1999 Verlag der Zeitschrift für Naturforschung, Tübingen ■www.znaturforsch.com
K
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172
M. Al-Jahdali et al. • 3-Hexyne Complexes of Molybdenum(II) and Tungsten(II)
Table I. Crystal data and structure refinement for 8 and 4.
8
4
Formula
[WI2(CO)(dppp)(rf-EtC2Et)]
C35H38C12I2OP2W
1045.14
293(2)
0.71073
monoclinic, P2|/c
18.90(2)
9.632(9)
[WI2(CO)(PPh3)2(?/2-EtC2Et)]
C4^H40l2OP,W
1072.34
293(2)
0.71073
orthorhombic, P2 j2121
9.823(9)
16.378(17)
Empirical formula
Formula weight
Temperature(K)
Wavelength (A)
Crystal system, space group
Cell dimensions (A,0) a
b
21.63(2)
c
25.10(3)
107.98(10)
3746(7)
90
4039(7)
ß
Volume (A )
Z, Calculated density (Mgm-3)
Absorption coefficient (mm- 1)
F(000)
Crystal size (mm)
0 Range for data collection (°)
Index ranges
4, 1.853
4.986
2000
4, 1.764
4.500
2064
0.25 x 0.30 x 0.30
2.40 to 25.93
0</?<23, -10<fc< 10, -26</<25
12362/6637
0.0477
0.15 x 0.25 x 0.25
2.42 to 25.94
0<h<9, -\9< k< \9, -30</<30
7410/5006
0.0615
Reflections collected / unique
R{int)
Data / restraints / parameters
Final R indices [I > 2<r(I)] R 1, wR2
R indices (all data) R 1, wR2
Extinction coefficient
Largest diff. peak, hole (eA~3)
Flack Parameter
6637/0/391
0.0504, 0.1227
0.0717, 0.1401
0.00018(10)
1.950,-1.843
5006 / 36 / 405
0.0785,0.1883
0.0911,0.1959
0.00065(10)
4.124,-1.985
Z: 0.01(13)
were recorded on a Bruker AC 250 MHz NMR spectro-
meter. 1H and 13C NMR spectra were referenced to SiMe4,
whereas l3P NMR spectra were referenced to 85% H3PC>4.
In a similar reaction of [WI2(CO)3(NCMe)2] with
two equivalents of 3-hexyne in CH2C12 at 0°C gave the
bis(3-hexyne) complex [WI2(CO)(NCMe)(772-EtC2Et)2]
(2). See Table I for physical and analytical data.
Reagents and materials
Preparation of [WI2(CO)(PPh3)2(ii2-EtC2Et)] (4)
All reactions and purifications were carried out
under an atmosphere of dry nitrogen using stan-
To
a stirred solution of [WI2(CO)(NCMe)(?72-
dard vacuum/Schlenk line techniques. The complexes EtC2Et)2] (0.50 g, 0.745 mmol) in CH2C12 (20 cm3)
[MI2(CO)3(NCMe)2] (M = Mo, W) [28], were prepared was added PPh3 (0.39 g, 1.48 mmol). After stirring
by the published method. All solvents and chemicals used the solution for 48 h, filtration, and removal of sol-
were of reagent grade quality and were purchased from
commercial sources. The solvents used were dried and which was recrystallised from CH2C12/Et20 to give pure
vent in vacuo yielded a dark green crystalline powder
distilled before use.
[WI2(CO)(PPh3)2(rf-EtC2Et)] (4), (yield = 0.76 g, 95%).
Single crystals for X-ray crystallography were grown by
cooling a CH2C12/Et20 mixture at -20 °C for 24 h.
A similar reaction of [MoI2(CO)(NCMe)(?72-EtC2Et)2]
with two equivalents of PPh3in CH2C12 at room temper-
ature gave the complex [MoI2(CO)(PPh3)2(?y2-EtC2Et)]
(3). See Table I for physical and analytical data.
Preparation of [MoIi(CO)(NCMe)(r]2-EtC2Et)2] (1)
To a stirred solution of [MoI2(CO)3(NCMe)2] (0.50 g,
0.968 mmol) in 20 ml of CH2C12 at 0 °C was added
3-hexyne (0.218 ml, 0.158 g, 1.926 mmol). The solu-
tion was slowly allowed to return to room temperature
and stirred at room temperature for 24 h. Filtration, and
removal of solvent in vacuo gave a brown crystalline
powder, which was recrystallized from dichloromethane
and diethyl ether, giving pure [MoI2(CO)(NCMe)(/;2-
EtC2Et)2] (1) (yield = 0.318 g, 56%).
Preparation of
[WI2(CO){ Ph2P(CH2)3PPh2}(rf -EtC2Et)] (8)
To
a stirred solution of [WI2(CO)(NCMe)(7/2-
EtC2Et)2] (0.50 g, 0.74 mmol) in CH2C12 (15 cm3) was
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M. Al-Jahdali et al. • 3-Hexyne Complexes of Molybdenum(II) and Tungsten(II)
173
Table II. Dimensions in the metal coordination spheres; Table III. Physical and analytical data for the 3-hexyne
distances (A), angles (°).
complexes 1-11.
In 4:
Compound (No.):
Colour Yield Analytical data: Found (Calcd.a) %
W (l)-C (100)
W (l)-C (74)
W (l)-P(2)
W (l)-I(3)
1.93(2)
2.03(3)
2.599(6)
2.900(3)
W (l)-C (73)
2.03(3)
2.584(5)
2.843(3)
(%)
C
H
N
W (i)-P (D
W( 0-1(2)
[MoMCO)(NCMe)(r72-EtC,Et)2] (1):
brown 56 30.3(30.9) 3.9 (4.0) 2.5 (2.4)
C( 100)-W( 1)-C(73)
C (73)-W (l)-C (74)
C (73)-W (l)-P (l)
C (100)-W (l)-P(2)
C (74)-W (l)-P(2)
C (100)-W (l)-I(2)
C (74)-W (l)-I(2)
P(2)-W (l)-I(2)
C( 100)-W ( 1)-C(74)
110.2(11)
37.3(11)
95.3(6)
89.2(7)
92.9(7)
72.9(11)
91.9(7)
98.6(7)
95.3(6)
168.2(2)
177.9(8)
84.34(15)
162.9(8)
124.2(8)
89.57(16)
[WI2(CO)(NCMe)(r72-EtC2Et)2] (2):
C(100)-W (1)-P(D
C(74)-W (1)-P(D
C(73)-W (l)-P(2)
P (l)-W (l)-P (2)
C(73)-W ( 1)-I(2)
P(l)-W ( 1)-I(2)
C(100)-W ( 1)-I(3)
C(74)-W ( 1)-I(3)
P(2)-W ( 1)-I(3)
yellow 79
27.0(26.9) 3.5 (3.4) 2.0 (2.1)
[Mol2(CO)(PPh3)2(f72-EtC2Et)] (3):
brown 48
52.3 (52.3) 4.1 (4.1)
—
71.9(8)
[WI2(CO)(PPh3)2(772-EtC2Et)] (4):
144.8(8)
84.88(15)
87.0(8)
green
95
48.2 (48.2) 3.7 (3.8)
—
C(73)-W ( 1)-I(3)
P (l)-W (l)-I(3)
[MoI2(CO){Ph2P(CH2)PPh2}(T72-EtC2Et)] (5):
brown 81 45.2(45.4) 3.8 (3.8)
85.91(15)
90.95(7)
—
I(2)-W( 1)-I(3)
[WI2(CO){Ph2P(CH2)PPh2}(?72-EtC2Et)] (6):
green 88 41.3 (41.2) 3.7 (3.5)
In 8:
—
W (l)-C (54)
W (O-C(100)
W (l)-C (53)
W (l)-P(5)
W( 1)-I(2)
1.967(10)
2.023(9)
2.633(3)
2.862(3)
2.006(10)
2.545(3)
2.824(2)
[WI2(C O ){P h.P(C H 2)2PPh^}(7?2-EtC2Et)] (7):
W (l)-P (l)
W( 0-1(3)
green
[WI2(CO){Ph2P(CH2)3PPh2}(?72-EtC2Et)] (8):
green 89 42.5 (42.5) 3.9 (3.8)
[WI,(CO){PhoP(CH2)4PPh2}(r?2-EtC2Et)] (9):
green 61 43.1(43.2) 4.0 (3.9)
[WI2(CO){Ph2P(CH2)5PPh'>}(^2-EtCiEt)] (10):
green 31 43.3 (43.8) 4.3 (4.1)
40
41.7(41.9) 3.6 (3.6)
—
—
C( 100)-W ( 1)-C(54) 109.7(4)
C(100)-W (l)-C(53) 72.1(4)
37.7(4)
86.4(3)
160.0(3)
125.6(3)
83.9(3)
96.8(3)
91.7(3)
88.6(3)
C (54)-W (l)-C (53)
C (100)-W (l)-P (0
—
C(54)-W (1)-P(D
C (100)-W (l)-P(5)
C(53)-W ( 1)-P(5)
C(100)-W ( 1)-I(3)
C(53)-W ( 1)-I(3)
P(5)-W( 1)-I(3)
C (53)-W (l)-P (0
C(54)-W (l)-P(5)
P( 1)-W(1)-P(5)
C(54)-W ( 1)-I(3)
P (l)-W ( 1)-I(3)
C(100)-W( 1)-I(2)
C(53)-W ( 1)-I(2)
P(5)-W( 1)-I(2)
92.15(11)
102.3(3)
170.54(6)
82.5(3)
151.8(3)
81.74(7)
-
[W l2(C O ){Ph2P(CH2)6PPh^}(772-EtC2Et)] (11):
97.4(3)
green
88
44.7 (44.3) 4.4 (4.2)
—
84.39(10)
162.3(3)
79.22(7)
91.55(6)
C(54)-W ( 1)-I(2)
P(l)-W ( 1)-I(2)
a Calculated values in parenthesis.
1(3)-W( 1)-I(2)
time of 2 min. Data analyses were carried out with the
XDS program [29]. The structures were solved using
direct methods with the SHELX-86 program [30]. The
non-hydrogen atoms were refined with anisotropic ther-
mal parameters. The hydrogen atoms were included in
geometric positions and given thermal parameters equiv-
alent to 1.2 times those of the atom to which they were
attached. Empirical absorption corrections were carried
out using the DIFABS program [31]. The structures were
then refined on F2 using the SHELXL-93 program [32],
All calculations were carried out on a Silicon Graphics
R4000 Workstation at the University of Reading.
added Ph2P(CH2)3PPh2 (0.307 g, 0.744 mmol). After
24 h, filtration and removal of solvent in vacuo gave a
green crystalline powder which was dissolved in the min-
imum quantity of CH2Cl2/Et20, and cooled to -20 °C for
24 h to afford suitable single crystals for X-ray analysis of
[WI2(CO){Ph
2
P(CH2)
3
PPh2}(r?2-EtC Et)] (8). (Yield =
2
0.635 g, 89%).
Similar reactions of equimolar quantities of [MI2-
(CO)(NCMe)(772-EtC2Et)2] and Ph2P(CH2)nPPh2 in
CH2CI2 at room temperature gave the complexes
[Ml2(CO){Ph2P(CH2)„PPh2}(r-E tC 2Et)] (M = Mo,
n = 1; M = W, n = 1, 2,4, 5, 6) (5 - 7,9 -11). See Table I
for physical and analytical data.
Results and Discussion
X-ray data collection and processing for 4 and 8
The starting materials used in this research,
Crystal data are given in Table I, together with refine- [MI2(CO)3(NCMe)2] (M
pared by treating the zero-valent complexes fac-
using the MAR-research Image Plate System. The crys- [M(CO)3(NCMe)3] (prepared in situ) with one
tals were positioned at 70 mm from the Image Plate. 95 equivalent of I2 at
°C [28]. Reaction of
frames were measured at 2° intervals with a counting
[MI2(CO)3(NCMe)2] (M = Mo, W) with two equi-
= Mo, W) were pre-
ment details. Data were collected with MoKa radiation
0
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174
M. Al-Jahdali et al. • 3-Hexyne Complexes of Molybdenum(II) and Tungsten(II)
Table V.1H NMR dataafor selected 3-hexyne complexes3.
Complex 1H NMR (6) ppm
Table IV. Infrared dataafor the 3-hexyne complexes 1 - 11.
Compound
No.
v(C = 0)
cm-1
i/(C=N)
cm-1
i/(C=C)
cm-1
1
3.15 - 3.4 (br, m, 4H, C=CCHi), 2.9 - 3.1 (br,
m, 4H, CH.), 2.75 (s, 3H, NCCfh), 1.2 - 1.35
(t, 12H, CHt,)
2290(w)
1604(w)
1634(w)
1664(w)
1654(w)
1658(w)
1603(w)
1654(w)
1656(w)
1639(w)
1635(w)
1658(w)
1
2
3
2059(s)
2056(s)
1952(s)
1942(s)
1943(s)
1931 (s)
1930(s)
1942(s)
1936(s)
1934(s)
1935(s)
2253(w)
—
—
—
—
—
—
—
—
—
2
3
4
5
3.2 - 3.4 (m, 4H, CHi), 2.9 - 3.1 (m, 4H, C=C-
C//2), 2.85 (s, 3H, NCC//0, 1-2 (dt, 12H. C //3)
7.1- 7.65 (br, m, 30H, Ph), 2.6 - 3.4 (br, m, 4H,
C=CCHi), 0.55 - 1.3 (dt, 6H, CH3)
7.2 - 7.65 (br, m, 30H, Ph), 3.15 (dq, 4H,
C=CCH2), 0.70 (t, 6H, C //3)
6.8 - 7.35 (br, m, 20H, Ph), 4.5 - 4.7 (q, 2H,
C=CCH2, J = 10 Hz), 3.35 - 3.6 (q, 2H, CHi),
2.9-3.15 (br, 2H, C=CCH2), 0.9- 1.25
(t, 6H, C //3, J = 7.5 Hz)
4
5
6
7
8
9
10
11
a Spectra recorded in CHCI3 as thin films between NaCl
plates; s = strong, w = weak.
6
7.0 - 7.8 (br, m, 20H, Ph), 4.55 - 4.85 (dt, 2H.
J = 8 Hz, PCH2), 3.6 (q, 2H, C=CCHi, J =
7.5 Hz), 3.1 - 3.3 (q, 2H, C=CCH2, J = 7.3 Hz),
1.05 - 1.25 (t, 6H, CHi, J = 7.5 Hz)
7
8
7.5 - 8.1 (m, 20H, Ph), 3.7 (br, m, 4H, Ph2PC//2),
3.4 (q, 4H, C=CCH2), 1.4 (t, 6H, CH^)
7.4 - 8.0 (m, 20H, Ph), 3.5 (q, 4H, C=CCH2),
3.3 (br, m, 4H, Ph2PC//2), 1.2 (t, 6H, C //3), 0.8
(br, m, 2H, Ph2PCH.C//2)
9
6.8 - 7.7 (br, m, 20H, Ph), 3.35 - 3.45 (m, 4H,
Ph2PCH2), 3.3 (q, 4H, C=CCH2), 2.6 - 3.15
(br, m, 4H, Ph2PCH2C//2), 1.0 - 1.25 (t, 6H, C //3)
6.9 - 7.6 (br, m, 20H, Ph), 3.2 - 3.4 (br, m, 4H,
PhiPC//2CH2), 2.95 - 3.2 (br, m, 4H, C=CCH2,
0.8- 1.35 (t, 6H, CHt,), 0.8 - 1.35
Me
Et
10
Fig. 1. Proposed structure of [MI2(CO)(NCMe)(?72-Et-
C2Et)2] (1 and 2).
(br, m, 6H, Ph2PCH2C//2C //2C//2)
11
7.2 - 7.7 (m, 20H, Ph), 3.4 (q, 4H, C=CCH2),
3.0 (br, m, 4H, Ph2PC//2), 2.4 (br, m, 4H,
Ph.PCH.CHi), 0.8 (t, 6H, CH3), 0.5
valents of EtC2Et in CH2CI2 at room tempera-
ture gave good yields of the bis(3-hexyne) com-
plexes [MI2(CO)(NCMe)(772-EtC2Et)2] (1 and 2 ).
Both complexes 1 and 2 were characterised by el-
emental analysis (C, H and N) (Table III), IR (Ta-
ble IV) and ’H NMR spectroscopy (Table V). Both
complexes are air-sensitive in solution, but can be
stored under nitrogen or argon in the solid state for
an indefinite period. The complexes are very solu-
ble in polar organic solvents such as CH2C12 and
CHCI3, but only slightly soluble in diethyl ether.
The IR spectra for 1 and 2 show carbonyl stretching
bands at v (C = 0 ) = 2059 and 2056 cm - 1 respec-
tively. These are in very similar positions to their
related 2-butyne derivatives [Ml2(CO)(NCMe)(/y2-
MeC2Me)2] {K C = 0 ) = 2061 cm“ 1 (M = Mo) [26],
2050 cm“ 1 (M = W) [25]}. The nitrile bands
z/(N=C) at 2290 and 2253 cm- 1 are typical of com-
plexes where the acetonitrile is acting purely as a
<7 -donor ligand [33]. The weak alkyne stretching
bands at 1604 and 1634 cm- 1 for 1 and 2 are con-
siderably lower than for the uncoordinated alkyne,
(br, m, 4H, Ph2PCH2CH2C //2)
3 Spectra recorded in CDCI3 (+25 °C) and referenced to
SiMe4; s = singlet, br = broad, d = doublet, m = multiplet,
t = triplet, q = quartet.
which is expected since there is back-donation of
electron density from filled metal d-type orbitals
to empty 7r*-orbitals on the 3-hexyne ligands. The
X-ray crystal structures of a number of bis(alkyne)
complexes, [MI2(CO)(NCR)(7?2-R’C2R')2] (M = W,
R = Me, R' = Me, Ph [25]; M = Mo, R = Me, R' =
Me, Ph [26]; M = W, R’ = Me, R = Bu' [34], Ph
[35], CH2(3 -C4H3S) [36]) have been reported and
all have the structure shown in Fig. 1. It is very likely
the structure of the bis(3-hexyne) complexes 1 and
2 is very similar as shown in Fig. 1, since the spec-
troscopic properties are closely related to the previ-
ously reported bis(alkyne) complexes of molybde-
num(II) and tungsten(II) [1,2,25 - 27,34 - 36]. The
1H NMR spectra of 1 and 2 show two different sets
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M. Al-Jahdali et al. • 3-Hexyne Complexes of MoIybdenum(II) and Tungsten(II)
175
Fig. 2. The structure
ofrWI2(CO)(PPh3)2-
(?7 -EtC2Et)] (4) with
the atom numbering
scheme. Ellipsoids
are shown at 30%
probability.
Table VI. I3C NMR data (<5) for selected 3-hexyne Table VII. 31P NMR data (6) for selected 3-hexyne
complexes“.
complexes“.
Complex
l3C NMR (<5) ppm
Complex
31P NMR (6) ppm
<5(P) = -2.69
<5(P) = -15.93, J(W-P) = 272.54 Hz
6(Pa ) = -23.733, <S(PB) = -36.21
6(PA) = 3.66, 6(PB) = -9.50,
7(W-Pb) = 270.78 Hz
1
6.85 (s, CH3.CN); 12.37, 13.86, 14.109, 14.37
(s, CH2CFh); 25.92, 29.19 (s, CFb); 129.55
(s, C=N); 172.18, 163.48 (s, C=C); 217.06
(s,C = 0 )
3
4
8
9
2
5
5.04 (s, CFh.CN); 13.63, 13.75 (s, CFI2CFh);
25.73, 29.35 (s, CH2CH3); 128.63 (s, C=N);
160.82, 171.45 (s, C=C); 206.54 (s, C =0)
12.49, 13.41, 13.77, 14.50 (s, CH3), 28.13,
29.64, 31.68 (s, CH2); 54.59 (s, PCH2); 128.25,
128.40, 128.63, 128.92, 129.08, 130.46, 131.63,
131.85, 132.04, 132.29, 133.32, 133.67, 133.82
(s, Ph); 210.1, 212 (C=C) 228.90 (C=0)
12.27, 13.48, 14.35, 15.28 (s, CH2CFh); 22.66,
24.91, 25.39 (s, PCFLCH2, CH9CH3); 28.87,
29.67, 30.97, 31.75, 34.21, 53.51, 65.84
(s, PCH2); 127.55, 127.87, 128.61, 129.51,
130.27, 130.55, 130.94, 132.16, 133.69 (s, Ph);
203.10, 205.02 (s, C=C), 222.75 (s, C =0)
11
<$(PA) = -9.47, 6(Pb) = -15.79
a Spectra recorded in CDCI3 (+25°C) and referenced to
H3 PO4 .
nances at 6 = 1 7 2 . 1 8 and 1 6 3 . 4 8 (for 1) and 1 6 0 .8 2
and 1 7 1 .4 5 (for 2). Templeton and Ward [3 7 ] have
correlated l3C NMR alkyne contact carbon chemi-
cal shifts with the number of electrons donated by
the alkyne to the metal. The resonances observed
for complexes 1 and 2 are in accord with the two
alkynes donating a total of six electrons to the metal
centre, which also enables the complexes to obey
the effective atomic number rule.
9
a Spectra recorded in CDCI3 (+25 °C) and referenced to
SiMe4; s = singlet.
Treatment of [Ml2(CO)(NCMe)(r;2-EtC2Et)2]
(M = Mo, W) with two equivalents of PPI13 in
CH2CI2 at room temperature gives the complexes
[Ml2(CO)(PPh3)2(772-EtC2Et)] (3 and 4). Com-
plexes 3 and 4 have also been characterised by
of CH2 groups, which conform with the structure
shown in Fig. 1. The room temperature 13C NMR
spectra of 1 and 2 have alkyne carbon contact reso-
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176
M. Al-Jahdali et al. • 3-Hexyne Complexes of Molybdenum(Il) and Tungsten(II)
Fig. 3. The structure of [Wl2(CO){Ph2P(CH2)3PPh2}(f72-EtC2Et)] (8), with the atom numbering scheme. Ellipsoids
are shown at 30% probability.
elemental analysis (Table III), IR (Table IV), 'H
is shown in Fig. 2 together with the atom number-
NMR (Table V) and 31P NMR spectroscopy (Ta- ing scheme. It is discussed and compared with the
ble VII). Complexes 3 and 4 are more stable in structure of 8 below.
solution, but very much less soluble than their bis-
(3-hexyne) precursors 1 and 2. They are both rea-
sonably soluble in CH2CI2 and CHCI3, however it
was difficult to obtain good l3C NMR spectra due
to their moderate solubility in polar NMR solvents.
The IR and 'H NMR spectral properties of 3 and
4 are similar to their 2-butyne tungsten analogue,
[Wl2(CO)(PPh3 )2(772-MeC2Me)] [38], which has a
carbonyl stretching band at 1940 cm -1 , similar to 4
{^(CO) = 1942 cm-1 } in the same solvent. The
31P NMR spectra for 3 and 4 have single reso-
nances at 6 = -2.69 and -15.93, respectively. This
suggests a trans arrangement of the PPh3 ligands
which is confirmed by the X-ray crystal struc-
ture of the tungsten complex 4, discussed along
Equimolar quantities of [MI2(CO)(NCMe)(?72-
EtC2Et)2] (M = Mo, W) and Ph2P(CH2)wPPh2
(M = Mo, n - 1; M = W, n - 1 to 6 ) react in
CH2CI2 at room temperature to yield the mono(3-
hexyne) complexes [MI2(CO){Ph2P(CH2)nPPh2}-
(?72-EtC2Et)] (5 - 11). Complexes 5-11 were fully
characterised (see Tables III to VII). They are
intermediate in solubility between 1, 2 and 3,
4 and similar in air-sensitivity to the bis(PPh3)
complexes
3 and 4. The colours and spec-
troscopic properties resemble that of their 2 -
butyne analogues, [WI2(CO){Ph2P(CH2)MPPh2}-
(?/2-MeC2Me)] reported previously [38]. The room
temperature 13C NMR spectra (CDCI3) for 5 and 9
have alkyne contact carbon resonances at 6 = 2 1 0 .1 ,
212 (for 5) and 203.10, 205.02 ppm (for 9) which in-
dicate from Templeton and Ward’s [37] correlation
that the 3-hexyne is donating four electrons to the
metal in these complexes. This enables complexes 5
and 9 to obey the effective atomic number rule. The
with the complex [WI2(CO){Ph2P(CH2)3PPh2}-
{rf-MeC2Me)] (8 ) below.
Suitable single crystals of [W l2(CO)(PPh3)2(772-
EtC2Et)] (4) were grown by cooling a CH2C12/Et20
solution of 4 to -20°C for 24h. The structure of 4
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M. Al-Jahdali et al. • 3-Hexyne Complexes of Molybdenum(II) and Tungsten(II)
177
In 8 , the two phosphorus atoms from the dppp lig-
and are perforce mutually cis with a P( 1)-W( 1)-P(5)
angle of 92.1 (1)°. The two bond lengths are signif-
icantly different in that W-P(F) with P (l) trans to
iodine is shorter at 2.545(3) A than W-P(5) with
P(5) trans to carbonyl. The alkyne is trans to io-
dide with W-C distances 2.01 (1), 2.02( 1) and W-I(2)
at 2.862(3) A. The remaining distances are W (l)-
C(100) 1.97(1) and W (l)-I(3) 2.824(2) Ä. Thus 1(2)
trans to ethyne forms a longer bond than 1(3) trans
to phosphorus.
This arrangement of donor atoms around the
metal is very different from that found in [WI2(CO)-
(dppm)(772-MeC2Me)] [38] and [Wl2(CO)(dppm)-
(rf-MeC2Ph)] [41], where the two m-phosphorus
atoms are trans to iodine and ethyne rather than
iodine and carbonyl as in 8 . It is not clear why
this difference is found though the size of the dppp
ligand bite compared to that of dppm might be a
significant factor.
31P NMR spectra of [WI2(CO){Ph2P(CH2)/IPPh2 }-
(r72-EtC2Et)] (n = 3, 4 and 6 ) have two resonances
(Table VII), which is expected for a single iso-
mer of 8 , 9 and 11. In order to obtain informa-
tion about the solid state structure, suitable crys-
tals of [WI2(CO) {Ph2P(CH2)3PPh2 }(rj2-EtC2Et)]
(8 ) were grown by cooling a CF^CL/T^O solution
of 8 to -20 °C for 24 h.
The molecular structure of 8 is shown in Fig. 3
together with the atomic numbering scheme. The
structures of 4 and 8 are shown in Figures 2 and 3
together with the atomic numbering schemes. The
dimensions in the metal coordination spheres are
listed in Table II. In both structures, if the ethyne is
considered as occupying one position in the coordi-
nation sphere, then the geometry around the metal
can be considered to be octahedral. In 4, the two
monodentate phosphorus atoms are mutually trans
with W (l)-P (l) 2.584 (5), W (l)-P(2) 2.599(6) A.
One iodine is trans to the ethyne and the bond to
the metal is significantly shorter at 2.843(3) A than
the bond from the iodine trans to the carbonyl at
2.900(3) A. The tungsten to ethyne bond lengths are
W (l)-C(73) 2.03(3), W (l)-C(74) 2.03(3) A, and to
the carbonyl 1.93(2) A. This arrangement of donor
atoms around the metal is equivalent to that found
in [MoBr2(CO)(PMePh2)2(/72-MeC2Me)] [39] and
[WCl2(C0 )(PMe2)2(772-"PhC2Ph)] [401.
Acknowledgements
M. Al-Jahdali thanks the Saudi Arabian government
for supporting him on a PhD studentship. We also thank
A. W. Johans for his assistance with the crystallographic
investigations, and the EPSRC and the University of
Reading for funds for the Image Plate System.
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