High yield synthesis, molecular structure, and reactions of the 16-electron norbornadiene complex, [WI2(CO)2(nbd)]

Article abstract of DOI:10.1002/1521-3749(200208)628:8<1727::AID-ZAAC1727>3.0.CO;2-A

Reaction of equimolar amounts of [WI₂(CO)₃(NCMe)₂] and norbornadiene (nbd) in toluene at 95°C for 3h gave the 16-electron crystallographically characterised complex, [WI₂(CO)₂(nbd)] (1) in 96% yield. The structure of 1 has a distorted octahedral geometry, with the two cis- iodo ligands opposite to the two alkene groups in the equatorial plane, with the carbonyl groups in the axial sites. Treatment of 1 with two equivalents of PhC₂Ph in CH₂Cl₂ at room temperature afforded the bis(alkyne) complex [WI₂(CO)₂(η²-PhC₂Ph) ₂] (2). Equimolar quantities of 1 and 4,4′-bipyridine react in CH₂Cl₂ at room temperature to yield the seven-coordinate complex, [WI₂(CO)₂(4,4′-bipyridine)(nbd)] (3).

Full text of DOI:10.1002/1521-3749(200208)628:8<1727::AID-ZAAC1727>3.0.CO;2-A

High Yield Synthesis, Molecular Structure, and Reactions of the 16-Electron
Norbornadiene Complex, [WI2(CO)2(nbd)]
Paul K. Bakera,*, Michael G. B. Drewb, Margaret M. Meehana, and Jan Müllera
a Bangor, Gwynedd / UK, Department of Chemistry, University of Wales
b Whiteknights, Reading / UK, Department of Chemistry, University of Reading
Received June 26th, 2001, revised March 18th, 2002.
Abstract. Reaction of equimolar amounts of [WI2(CO)3(NCMe)2]
and norbornadiene (nbd) in toluene at 95 °C for 3h gave
the 16-electron crystallographically characterised complex,
[WI2(CO)2(nbd)] (1) in 96 % yield. The structure of 1 has a dis-
torted octahedral geometry, with the two cis- iodo ligands opposite
to the two alkene groups in the equatorial plane, with the carbonyl
groups in the axial sites. Treatment of 1 with two equivalents of
PhC2Ph in CH2Cl2 at room temperature afforded the bis(alkyne)
complex [WI2(CO)2(η2ϪPhC2Ph)2] (2). Equimolar quantities of 1
and 4,4Ј-bipyridine react in CH2Cl2 at room temperature to yield
the seven-coordinate complex, [WI2(CO)2(4,4Ј-bipyridine)(nbd)]
(3).
Keywords: Tungsten; Tungsten norbornadiene iodocarbonyl com-
plex
Halocarbonyl complexes of molybdenum(II) and tungsten(II) have
been extensively studied [1]. A number of norbornadiene halocar-
bonyls complexes of the types, [WBr2(CO)2(nbd)] [2, 3],
[WBr(SC6F5)(CO)2(nbd)] [4], [MoX2(CO)2(nbd)] (X ϭ Br, I) [5],
[WBr(CO)2(terpyridine) (nbd)]ϩ [6] and [WCl(SnCl3)(CO)3(nbd)]
[7] have been described. In 1999, Davidson et al. [8] described the
reactions of [WI2(CO)3(NCMe)2] with diene (diene ϭ nbd, cod)
in refluxing 60Ϫ80 petroleum ether to afford the six-coordinate
complexes, [WI2(CO)2(diene)] (diene ϭ nbd, 42 % yield, cod, 31 %
yield). Several dibromo seven-coordinate complexes, including
[WBr2(CO)2(PMePh2)(nbd)] and [WBr2(CO)(NCCHϭCH2)(nbd)],
which have been crystallographically characterised were also re-
ported. Earlier [9], we also described the synthesis of
[WI2(CO)2(nbd)], by an analogous method to Davidson et al, by
refluxing nbd in hexane for 6h, to give 17 % yield of the product,
which we have now reported [10]. In order to further investigate
the reaction of [WI2(CO)3(NCMe)2] with nbd under a variety of
different conditions, we found that treatment of equimolar quantit-
ies of [WI2(CO)3(NCMe)2] and nbd in toluene at 95 °C for 3h gives
96 % yield of pure [WI2(CO)2(nbd)]. Herein we describe these new
results, together with the molecular structure of [WI2(CO)2(nbd)]
(1), and its reaction with PhC2Ph and 4,4Ј-bipyridine.
that Davidson et alЈs yield of 42 % for this reaction is the best which
could be achieved by this method. We previously observed [10] that
reaction of [WI2(CO)3(NCMe)2] with a 200 fold excess of nbd in
toluene at 35 °C, 40 °C and 50 °C for 24h give only the starting
materials with no evidence of complex formation or poly(noborna-
diene). We decided to reinvestigate this reaction at higher tempera-
ture, and after many experiments it was observed that the optimum
conditions for complex formation was reaction in toluene at 95 °C
precisely, using an oil bath for 3h, which gave a 96 % yield of
[WI2(CO)2(nbd)] (1). Complex 1 was characterised by elemental
1
analysis (C, H, N), IR and H NMR spectroscopy (see experimen-
tal) and by X-ray crystallography. The spectroscopic data are the
same as for the previously reported synthesis [8 Ǟ 10] of this com-
plex. We observed that if the temperature is maintained above
95 °C, for example, at 100 °C, poly(norbornadiene) was observed
and no diene complex
1
was obtained. Reaction of
[WI2(CO)3(NCMe)2] with nbd in a 1:500 ratio at 100 °C, after
10 min. almost quantitative polymerisation of norbornadiene was
observed. These results suggest that there is a fine line between
when complex formation/polymerisation of norbornadiene occurs
in these reactions of nbd with halocarbonyl complexes of MoII
and WII.
In order to compare the structure of [WI2(CO)2(nbd)] (1) with the
related dibromo complex, [WBr2(CO)2(nbd)], which has been pre-
viously structurally characterised [3] we grew suitable crystals of 1
by cooling a concentrated diethyl ether solution of 1 to Ϫ17 °C for
24h. The structure of 1 is shown in Fig. 1, together with the atomic
numbering scheme. The structure is isomorphous with the dibro-
mide analogue [3] and while it has no crystallographic symmetry,
it comes close to C2v symmetry. The molecular dimensions are
shown in Table 1. The coordination geometry is best considered
as a distorted octahedron with an equatorial plane containing a
norbornadiene occupying two adjacent sites trans- to iodide anions
Synthesis, catalytic studies and molecular structure of
[WI2(CO)2(nbd)] (1)
The seven-coordinate starting material for this research,
[WI2(CO)3(NCMe)2] was prepared by the reaction of fac-
[W(CO)3(NCMe)3] (prepared in situ) with one equivalent of I2 as
previously described [11]. Initially we decided to carry out the reac-
tions of [MI2(CO)3(NCMe)2] with nbd in petroleum ether (60 Ϫ
80) [8] or hexane [9] as has been previously described, and we found
˚
(W-I 2.703(4), 2.704(3) A). The structure is completed by two mu-
˚
tually trans carbonyl groups in axial sites at 2.067(15), 2.068(16) A.
The distances from the metal to the norbornadiene carbon atoms
are equivalent within experimental error ranging from 2.270(16) to
2.318(14) A. These dimensions differ only slightly from those found
* Dr. Paul K. Baker
Department of Chemistry, University of Wales,
Bangor, Gwynedd, LL57 2UW / UK
E-mail: chs018@bangor.ac.uk
˚
in the dibromide analogue where the W-Br distances are 2.489(1),
Z. Anorg. Allg. Chem. 2002, 628, 1727Ϫ1729  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 0044Ϫ2313/02/628/1727Ϫ1729 $ 20.00ϩ.50/0
1727

P. K. Baker, M. G. B. Drew, M. M. Meehan, J. Müller
Fig. 2 Proposed structure of [WI2(CO)2(4,4Ј-bipyridine)(nbd)] (3).
[MoBr(CO)(terpyridine)(nbd)]ϩ [6], [MoBr(CO)(bipy)(nbd)]ϩ [6],
[WBr2(CO)2(PMePh2)(nbd)] [8] and [WCl(SnCl3)(CO)3(nbd)] [7]
where the structures are 7-coordinate. In all but the last the M-
C(norbornadiene) distances are equivalent but in this latter struc-
˚
ture they vary from 2.326(8), 2.306(9) A trans to chlorine to
˚
2.407(9), 2.413(8) A trans to carbonyl. There are two other six-co-
ordinate
structures
[WBr(SC6H5)(CO)2(nbd)]
[4]
and
[WBr2(CO)(NϵCCHϭCH2)(nbd)] [8] in which the metal atoms
have a distorted octahedral environment. In the former, there is a
significant difference between W-C(norbornadiene) distances, with
2.23(2), 2.28(2) A trans to Br and 2.40(2), 2.38(2) A trans to S.
However, in the latter structure the norbornadiene is trans to the
two bromine atoms and WϪC(norbornadiene) distances are equiv-
alent. The distortions in the octahedral environment of this struc-
ture are equivalent to those found in 1 and the dibromide analogue.
Fig. 1 The molecular structure of [WI2(CO)2(nbd)] (1) with the
atomic numbering scheme. Ellipsoids shown at 30 % occupancy.
˚
˚
˚
Table 1 Dimensions/A, ° in the Metal Coordination Sphere of 1
W(1)-C(200)
W(1)-C(100)
W(1)-C(2)
W(1)-C(4)
W(1)-C(1)
W(1)-C(3)
W(1)-I(12)
W(1)-I(11)
2.067(15)
2.068(16)
2.270(16)
2.285(16)
2.292(12)
2.318(14)
2.703(4)
Reactions of [WI2(CO)2(nbd)] (1) with PhC2Ph and
4,4Ј-bipyridine
Reactions of 1 with two equivalents of PhC2Ph in CH2Cl2 at room
temperature for 24h gave the bis(alkyne) complex, [WI2(CO)2(η2-
PhC2Ph)2] (2) in 36 % yield. Complex 2 has been previously de-
scribed [12], as a result of reaction of the bis(alkyne) complex
2.704(3)
C(200)-W(1)-C(100)
C(200)-W(1)-C(2)
C(100)-W(1)-C(2)
C(200)-W(1)-C(4)
C(100)-W(1)-C(4)
C(2)-W(1)-C(4)
C(200)-W(1)-C(1)
C(100)-W(1)-C(1)
C(2)-W(1)-C(1)
C(4)-W(1)-C(1)
C(200)-W(1)-C(3)
C(100)-W(1)-C(3)
C(2)-W(1)-C(3)
C(4)-W(1)-C(3)
C(1)-W(1)-C(3)
C(200)-W(1)-I(12)
C(100)-W(1)-I(12)
C(2)-W(1)-I(12)
C(4)-W(1)-I(12)
C(1)-W(1)-I(12)
C(3)-W(1)-I(12)
C(200)-W(1)-I(11)
C(100)-W(1)-I(11)
C(2)-W(1)-I(11)
C(4)-W(1)-I(11)
C(1)-W(1)-I(11)
C(3)-W(1)-I(11)
I(12)-W(1)-I(11)
170.5(6)
112.2(7)
76.4(7)
77.4(7)
111.3(7)
34.8(7)
111.2(6)
76.0(5)
62.4(5)
73.1(5)
75.1(6)
112.2(5)
73.7(5)
61.3(5)
36.2(5)
86.7(5)
88.5(4)
94.7(4)
94.6(3)
154.7(4)
152.2(3)
86.8(4)
86.5(5)
153.6(4)
154.1(4)
94.2(3)
95.0(4)
104.90(5)
[WI2(CO)(NCMe)(η2-PhC2Ph)2] with CO. It has
a carbonyl
stretching band at 2100 cmϪ1 which suggests a trans-dicarbonyl
structure. The structure of the related bis(2-butyne) complex
[WI2(CO)2(η2-MeC2Me)2] has been previously reported [12].
Equimolar quantities of 1 and 4,4Ј-bipyridine react in CH2Cl2 at
room temperature to give the 18-electron complex, [WI2(CO)2(4,4Ј-
bipyridine)(nbd)] (3), which has been characterised by elemental
analysis, IR. and 1H NMR spectroscopy (see Experimental section
2.1.3.). This relatively unstable complex, is related to the dibromo
complexes [WBr2(CO)2L(nbd)] (L ϭ PMePh2, PEt3, PPh3) reported
by Davidson et al. [8]. It is interesting to note that the reaction
of organonitriles, NCR with [WBr2(CO)2(nbd)] afforded the 16-
electron complexes [WBr2(CO)(NCR)(nbd)] (R ϭ Me, iPr, Ph,
C6H4Me-4, CHϭCH2), which has been structurally characterised
for R ϭ CHϭCH2. We have chosen an intermediate type ligand,
4,4Ј-bipyridine, and we have the less electronegative iodo ligands,
which should favour addition rather than CO displacement reac-
tions, which is what we have observed. Complex 3 has two carbonyl
bands in its IR spectrum, which is compatible with the formulation
as [WI2(CO)2(4,4Ј-bipyridine)(nbd)]. Since the structure of
[WBr2(CO)2(PMePh2)(nbd)] has been determined [8], and has a
distorted pentagonal bipyramidal structure with the trans-carbonyl
ligands in the axial plane and the nbd, bromo ligands and the phos-
phine in the equatorial plane. In view of these observations the
likely structure of [WI2(CO)2(4,4Ј-bipyridine)(nbd)] (3) is shown in
Fig. 2.
˚
2.493(1) A. The distortions from octahedral symmetry are similar
in the two compounds such that the I-W-I angle is 104.9(1)° in 1
compared to an Br-W-Br angle of 105.9(1)°.
The structure can be compared to several others containing the
norbornadiene ligand with Mo or W. These include
1728
Z. Anorg. Allg. Chem. 2002, 628, 1727Ϫ1729

Norbornadiene Complex, [WI2(CO)2(nbd)]
with MoKα radiation using the MARresearch Image Plate System.
The crystal was positioned at 70 mm from the Image Plate. 100
frames were measured at 2° intervals with a counting time of 2
mins. to give 4210 reflections of which 2256 were independent
(R(int) ϭ 0.0331). Data analysis was carried out with the XDS
program [13]. The structure was solved using direct methods with
the Shelx86 program [14]. The non-hygrogen atoms were refined
with anisotropic thermal parameters. The hydrogen atoms were in-
cluded in geometric positions and given thermal parameters equiv-
alent to 1.2 times those of the atom to which they were attached.
An empirical absorption correction was carried out using DIFABS
[15]. The structure was refined on F2 using Shelx [16]. The final R
values were R1 ϭ 0.0509 and wR2 ϭ 0.1451 for 2256 data with
I > 2σ(I). Details have been deposited at the Cambridge Data Cen-
tre Reference No CCDC 160243.
Experimental
The synthesis and purification of the complexes described in this
paper were carried out using standard vacuum/Schlenk line tech-
niques. The starting material, [WI2(CO)3(NCMe)2] was prepared as
we have previously described [11]. All chemicals were purchased
from commercial sources. Toluene and ether were dried and dis-
tilled before use. Elemental analyses were determined using a Carlo
Erba Elemental Analyser MOD 1108 (using helium as the carrier
gas). Infrared spectra were recorded on a Perkin-Elmer 1600 FT
IR spectrophotometer. Proton NMR spectra were recorded on a
Brucker AC 250 MHz NMR spectrometer and were referenced to
SiMe4.
[WI2(CO)2(nbd)] (1). To a stirred solution of [WI2(CO)3(NCMe)2]
(1.25g, 2.07mmol) in 100ml of toluene, nbd (0.28ml, 2.07mmol)
was added. The reaction mixture was heated to 95 °C for 3h. The
solvent was removed in vacuo, and the residue was extracted with
diethyl ether, after filtration and reducing to minimum volume,
1.17g, 96 %, yield of the dark green product [WI2(CO)2(nbd)] (1),
was obtained.
MMM thanks the EPSRC for a studentship, and JM thanks ER-
ASMUS scheme for support. We also thank Mr. A.W. Johans for
his help in determining the structure, and we thank the EPSRC and
the University of Reading for funds for the Image Plate System.
Data for 1 (%): Found: C, 18.4; H, 1.6. C9H8O2I2W requires, C,
18.4; H, 1.4.
[1] P.K. Baker, Adv. Organomet. Chem. 1996, 40, 45, and refer-
ences cited therein.
[2] J.L. Davidson, G. Vasapollo, J. Chem. Soc., Dalton Trans.
1985, 2231.
[3] F. A. Cotton, J.H. Meadows, Inorg. Chem. 1984, 23, 4688.
[4] L. Carlton, J.L. Davidson, G. Vasapollo, G. Douglas, K.W.
Muir, J. Chem. Soc., Dalton Trans. 1993, 3341.
[5] T. Daniel, H. Nagao, K. Tanaka, A. Nakamura, Chem. Ber.
1995, 128, 1007.
.
IR (CHCl3) ν (CO) ϭ 2058 (w), 1982 (s) cmϪ1 1H NMR (CDCl3): δ ϭ 0.56
(t, 2H, nbd), 3.99 (s, 2H, nbd), 4.59 (m, 4H, nbd).
[WI2(CO)2(η2-PhC2Ph)2] (2). To
a
stirred solution of
[WI2(CO)2(nbd)] (0.4g, 0.68mmol) was added PhC2Ph (0.24g, 1.36
mmol). After stirring the solution for 24h at room temperature,
filtration gave the yellow complex [WI2(CO)2(η2-PhC2Ph)2] (2),
which was recrystalised from CH2Cl2/Et2O, 80:20. (Yield of pure
product ϭ 0.21g, 36 %).
[6] T. Daniel, H. Nagao, H. Nakojima, K. Tanaka, A. Nakamura,
J. Organomet. Chem. 1996, 509, 225.
Data for 2. Conforms with the previously reported complex [12].
´
[7] T. Szymanska-Buzar, T. Głowiak, Polyhedron 1997, 16, 1599.
[WI2(CO)2(4,4Ј-bipyridine)(nbd)] (3). To
a stirred solution of
[8] J.L.Davidson, H. Richtzenhein, B.J.S. Thiebaut, K. Land-
skron, G.M. Rosair, J. Organomet. Chem. 1999, 592, 168.
[9] D.J. Muldoon, PhD thesis, Univ. of Wales, Bangor, 1994,
page 93.
[10] M. Al-Jahdali, P.K. Baker, A.J. Lavery, M.M. Meehan, D.J.
Muldoon, J. Mol. Catal. A, Chem. 2000, 159, 51
[11] P.K. Baker, S.G. Fraser, E.M. Keys, J. Organomet. Chem. 1986
309, 319.
[WI2(CO)2(nbd)] (0.22g, 0.375mmol) in CH2Cl2 (25ml) was added
4,4Јbipyridine (59mg, 0.375mmol). After stirring for 1h., a brown
precipitate was formed which was washed four times with diethyl
ether and dried to give, [WI2(CO)2(4,4Ј-bipyridine)(nbd)] (3),
(0.23g, 83 %).
Data for 3 (%): Found C, 30.5, H, 2.5; N, 3.7. C19H16N2O2I2W
requires C, 30.8; H, 2.2; N, 3.8.
IR(CHCl3). ν(CO) ϭ 1985 (s), 1909 (s) cmϪ1 {ν(CO) ϭ 2025, 1920 cmϪ1
(KBr disc)}. 1H NMR (CDCl3, ϩ25 °C): δ ϭ 8.8 Ǟ 7.8 (brm, 8H, 4,4Ј-
bipyridine), 3.6 (m, 4H, nbd), 2.4 (s, 2H, nbd), 2.2 (s, 2H, nbd).
[12] E. M. Armstrong, P.K. Baker, M.G.B. Drew, J. Organomet.
Chem. 1987, 336, 377.
[13] W. Kabsch, J.Appl. Cryst. 1988, 21, 916.
[14] G. M. Sheldrick, Acta Crystallogr. 1990, A46, 467.
[15] N. Walker, D. Stuart, Acta Crystallogr. 1983, A39, 158
[16] G. M. Sheldrick, Shelxl 1993, Program for Crystal Structure
Refinement, University of Göttingen.
Crystal data for [WI2(CO)2(nbd)] (1) C9H8I2O2W, M ϭ 585.80,
monoclinic, spacegroup P21/c, a ϭ 7.624(12), b ϭ 11.326(15), c ϭ
˚
˚
14.632(18) A, β ϭ 101.33(1)°, U ϭ 1239 A, Z ϭ 4, dc ϭ
3.141 gm cmϪ3, µ ϭ 14.282 mmϪ1. Intensity data were collected
Z. Anorg. Allg. Chem. 2002, 628, 1727Ϫ1729
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