Electrophilic addition reactions of the Lewis acids B(C6F5)2R [R = C6F5, Ph, H or Cl] with the metallocene hydrides [M(η-C5H5)2H2] (M = Mo or W), [Re(η-C5H5)2H2] and [Ta(η-C5H5)H3]

Article abstract of DOI:10.1039/a908623d

The syntheses of the new compounds [η-C₅H₅)₂H₂], where R = (C₆F₅) 1, Ph 2, H 3 or Cl 4, [Mo(η-C₅H₅)₂H₂] 5, [Mo(n-C5H5)2(H)(n'-H2B(C6F5)2)] 6, [Mo(η-C₅H₅)₂H₂)] 7, [Re(η-C₅H₅)₂H₂]-0.5C ₆H₅Me 8, [Ta(η-C₅H₅)₂H₂] 9 and [Re(n-C₅H₅)(r,-C₅H₄-{B(C ₆F₅)₂})(C₆F₅)] 10 are described. The crystal structures of compounds 4 and 10 have been determined. Initial electrophilic addition of the Lewis acid B(C₆F₅)₃ occurs either by evo-addition to a carbon of a rj-cyclopentadienyl ring with formation of an cvo-{(C₆F₅)₁B}C₃Hj, or by formation of an M-u-H-B two-electron three-centre bond. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/a908623d

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Electrophilic addition reactions of the Lewis acids B(C6F5)2R
[R ؍ C6F5, Ph, H or Cl] with the metallocene hydrides
[M(ꢀ-C5H5)2H2] (M ؍ Mo or W), [Re(ꢀ-C5H5)2H] and
[Ta(ꢀ-C5H5)2H3]
Linda H. Doerrer, Andrew J. Graham, Daniel Haussinger and Malcolm L. H. Green*
Inorganic Chemistry Laboratory, South Parks Road, Oxford, UK OX1 3QR
Received 29th October 1999, Accepted 14th January 2000
Published on the Web 9th February 2000
The syntheses of the new compounds [W(η-C5H5)(η-C5H4{B(C6F5)2R})H3], where R = (C6F5) 1, Ph 2, H 3 or Cl 4,
[Mo(η-C5H5)2(H)(η1-HB(C6F5)3)] 5, [Mo(η-C5H5)2(H)(η1-H2B(C6F5)2)] 6, [Mo(η-C5H4Me)2(H)(η1-HB(C6F5)3)] 7,
[Re(η-C5H5)(η-C5H4B(C6F5)3)H2]ؒ0.5C6H5Me 8, [Ta(η-C5H5)2(H)2(η1-HB(C6F5)3)] 9 and [Re(η-C5H5)(η-C5H4-
{B(C6F5)2})(C6F5)] 10 are described. The crystal structures of compounds 4 and 10 have been determined. Initial
electrophilic addition of the Lewis acid B(C6F5)3 occurs either by exo-addition to a carbon of a η-cyclopentadienyl
ring with formation of an exo-{(C6F5)3B}C5H5, or by formation of an M–µ-H–B two-electron three-centre bond.
The strong Lewis acid B(C6F5)3 has been shown to add to
metal–alkyl and metal–hydrogen bonds to form two-electron
three-center systems such as M–µ-Me–B(C6F5)3 and M–µ-H–
(η-C5H4{BRCl2})H3] where R = Pri or But which were formed
by the reaction of [W(η-C5H5)2H2] with BRCl2.8 The 1H NMR
spectroscopic data and coupling constants obtained for
the compounds 1–4 are closely similar to those obtained
for Braunschweig’s complexes.
1
B(C6F5)3.2 We have recently explored the addition reactions
of B(C6F5)3 to transition metal-oxo3 and -nitrido4 compounds.
The compound B(C6F5)3 also reacts in an unexpected manner
with the compounds [M(η-C5H5)(CO)nMe], where M = Fe and
n = 2 or M = Mo, W and n = 3, and in these cases transfer of a
fluoroaryl group occurs.5 Other related transfer reactions have
also been described.6
The 1H NMR spectra in the region δ Ϫ6.26 to Ϫ6.7 showed
a doublet and a triplet (integrating in the ratio 1:2) with
additional 183W satellite peaks, a typical pattern for an AB2X
spin system. The H–H coupling constants for the WH3 hydro-
gens in compounds 1 to 3 lie in the region 4.8–9.6 Hz, consistent
2
Since there are relatively few systematic studies of the reac-
tions of Lewis acid molecules with transition metal compounds
and since the organo-borane B(C6F5)3 is a readily available5b,7
thermally stable crystalline compound, we have set out to
explore its reactions more widely. Here we report the reactivity
of the Lewis acids B(C6F5)2R [R = (C6F5), Ph, H or Cl] towards
a selection of metallocene hydrides of Groups 5, 6 and 7.
with data reported for [W(η-C5H5)2H3]Cl.9 The value of JHH
for compound 2 in CD2Cl2 is lower (4.8 Hz), and is comparable
with that observed in the compound [W(η-C5Me5)2H3][BPh4].10
The one bond 183W–H coupling constant (where it could be
determined) is of a similar magnitude to that found in the
previously cited compounds8–10 with coupling to the central
hydride being greater than that to the outer ones.
The 11B-{1H} NMR spectra for compounds 1–4 showed
single sharp resonances in the range δ ca. Ϫ7 to Ϫ25, consistent
with fourfold coordinated boron. For compound 3, a doublet
Results and discussion
1
Treatment of the compound [W(η-C5H5)2H2] in toluene at
Ϫ78 ЊC with B(C6F5)3 gave a deep purple solution which, on
warming to ca. Ϫ50 ЊC, gradually became pale yellow. This
final product contained substantial quantities of starting
dihydride as well as several other species and no tractable
products could be obtained. However, the reaction between
[W(η-C5H5)2H2] and the boranes B(C6F5)2R, where R = (C6F5),
Ph, H or Cl, in an aliphatic solvent at ambient temperature
follows an entirely different course. On addition of these
boranes to [W(η-C5H5)2H2] in petroleum ether (bp 100–120 ЊC),
a flocculent white precipitate separated immediately. After
stirring for one hour, the products were isolated by filtration
and washed thoroughly with petroleum ether to remove
remaining traces of [W(η-C5H5)2H2] and B(C6F5)2R. The
zwitterionic compounds [W(η-C5H5)(η-C5H4{B(C6F5)2R})H3],
where R = (C6F5) 1, Ph 2, H 3 or Cl 4, were obtained analytic-
ally pure in high yield, as white or off-white powdery air- and
moisture-sensitive solids which are moderately soluble in
aromatic solvents and dichloromethane. Donating solvents such
as tetrahydrofuran were found to cause decomposition. Full
characterising data for compounds 1–4 are given in Table 1.
Previously, Braunschweig and Wagner have described the
closely related zwitterionic trihydride compounds [W(η-C5H5)-
with JBH = 86 Hz was observed in the proton-coupled 11B
NMR spectrum. Selected infrared spectral data are listed in
Table 1. All the compounds 1–4 display a weak, broad band at
ca. 1940–1990 cmϪ1 which may be assigned to ν(W–H).8
Single crystals of 4 suitable for analysis by X-ray crystal-
lography were grown by slow evaporation of a solution in
benzene at ambient temperature. The molecular structure of
compound 4 is given in Fig. 1 and selected bond angles
and distances are summarised in Table 2. The structure is
essentially similar to that of the compound [W(η-C5H5)-
(η-C5H4{BPriCl2})H3].8 The W–H bonds in compound 4 are
slightly shorter (1.41–1.52 Å) than those of the PriBCl2
analogue (1.51–1.58 Å) and the Houter–W–Houter angle much
tighter (115.6 vs. 141.0Њ).
The 1H NMR spectra of initially pure samples of com-
pounds 1–4 showed a slow appearance of a small quantity
of [W(η-C5H5)2H2] but the intensity of these signals did not
increase after about 12 hours. This observation suggested
there was a slow equilibrium dissociation of the B(C6F5)2R
groups. Hence, compound 1 was reacted with a series of com-
peting Lewis bases, L = NEt3, PMe3, THF, in the expectation
that they would trap the free borane. In a typical experiment,
ca. 20 mg of 1 was dissolved in toluene and an excess of the
DOI: 10.1039/a908623d
J. Chem. Soc., Dalton Trans., 2000, 813–820
This journal is © The Royal Society of Chemistry 2000
813

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Table 1 Analytical and spectroscopic data for compounds 1–9
Compounda
NMR datab
1
2
[W(η-C5H5)(η-C5H4{B(C6F5)3})H3]
White
1H: Ϫ6.38 (d, 2H, 2JHH = 9.6, WHouter), Ϫ6.27 (t, 1H, 2JHH = 9.6, WHcentre), 5.23 (s, 5H, C5H5),
5.52 and 5.56 (s, 2H, each, C5H4B)
C, 40.7 (40.6); H, 1.1 (1.5); B, 1.05 (1.3)
11B-{1H}: Ϫ15.6 (s)
Mass: 851, [M ϩ Na]ϩ; 828, [M]ϩ; 660, 13C-{1H}: 83.30 and 84.18 (s, C5H4B), 87.11 (br s, C5H4B, Cipso), 96.93 (s, C5H5), 130.46 (d,
[M Ϫ (C6F5) Ϫ H]ϩ; 316, [M Ϫ B(C6F5)3]ϩ
IR: 1939w (ν(W–H)), 1768w, 1645w,
1516m, 1262s, 1089s, 975m, 833m, 800s
[W(η-C5H5)(η-C5H4{B(C6F5)2(C6H5)})H3]
Off-white
1JCF = 251, B(C6F5), Cm), 137.60 (d, 1JCF = 253, B(C6F5), Cp), 148.46 (d, 1JCF = 249, B(C6F5), Co)c
1H: Ϫ6.48 (d, 2H, 2JHH = 4.8, WHouter), Ϫ6.38 (t, 1H, 2JHH = 4.8, WHcentre), 4.94 and 5.38 (s, 2H
each, C5H4B), 5.10 (s, 5H, C5H5), 7.1–7.3 (m, 5H, C6H5)
C, 45.6 (45.6); H, 2.1 (2.3); B, 1.7 (1.5)
Mass: 316, [M Ϫ B(C6F5)2(C6H5)]ϩ
IR: 3551m (aromatic ν(C–H)), 1951w
11B-{1H}: Ϫ13.1 (s)
13C-{1H}: 71.60 and 84.03 (s, C5H5B), 83.42 (s, C5H5), 87.24 (br s, C5H4B, Cipso), 96.91 (br s,
B(C6H5), Cipso), 112.60 (br s, B(C6F5), Cipso), 124.80 (s, B(C6H5), Cm), 126.41 (s, B(C6H5), Cp),
(ν(W–H)), 1645m, 1518m, 1103m, 1082s, 133.91 (s, B(C6H5), Co), 137.16 (d, 1JCF = 258, B(C6F5), Cm), 138.46 (d, 1JCF = 239, B(C6F5), Cp),
981s, 811s (br)
[W(η-C5H5)(η-C5H4{B(C6F5)2H})H3]
Off-white
C, 39.9 (39.9); H, 1.7 (2.0); B, 1.6 (1.6)
IR: 1991w (ν(W–H)), 1636w, 1510m,
1275m, 1108m, 1087m, 1073m, 1023w,
964s (br)
148.21 (d, 1JCF = 220, B(C6F5), Co)
3
4
1H: Ϫ6.71 (d, 2H, 2JHH = 7.6, 1JWH = 4.60, WHouter), Ϫ6.44 (t, 1H, 2JHH = 7.6, 1JWH = 66.6,
WHcentre), 4.5 (br s, BH), 5.25 and 5.29 (m, 2H, each, C5H4B), 5.33 (s, 5H, C5H5)
11B-{1H}: Ϫ23.4 (s)
11B: Ϫ23.4 (d, 1JBH = 86)
13C-{1H}: 71.77 and 82.67 (s, C5H4B), 84.71 (s, C5H5), 89.50 (br s, C5H4B, Cipso), 136.88 (d,
1JCF = 242, B(C6F5), Cm), 138.55 (d, 1JCF = 242, B(C6F5), Cp), 148.24 (d, 1JCF = 293, B(C6F5), Co)
1H: Ϫ6.37 (d, 2H, 2JHH = 7.8, 1JWH = 46.2, WHouter), Ϫ6.26 (t, 1H, 2JHH = 7.8, 1JWH = 66.2,
WHcentre), 5.20 and 5.52 (s, 2H, each, C5H4B), 5.40 (s, 5H, C5H5)
[W(η-C5H5)(η-C5H4{B(C6F5)2Cl})H3]
Grey-white
C, 39.25 (37.9); H, 2.5 (1.7); B, 1.2 (1.55); 11B-{1H}: Ϫ6.7 (s)
Cl, 5.5 (5.1)
13C-{1H}: 83.71 (s, C5H5), 84.66d (s, C5H4B), 87.70 (br s, C5H4B, Cipso), 123.0 (br s, B(C6F5), Cipso),
IR: 1941w (ν(W–H)), 1645m, 1516m, 137.16 (d, 1JCF = 264, B(C6F5), Cm), 139.26 (d, 1JCF = 269, B(C6F5), Cp), 147.54 (d, 1JCF = 239,
1280m, 1089s (br), 1019w, 974s
[Mo(η-C5H5)2(H)(η1-HB(C6F5)3)]
Blue
C, 45.2 (45.4); H, 2.2 (1.6)
IR: 2135m (ν(B–H)), 1550m, 1470s
B(C6F5), Co)
5
6
1H: Ϫ17.5 (br s, Mo–H–B), Ϫ6.21 (s, 1H, MoH), 4.95 (s, 10H, C5H5)
11B-{1H}: Ϫ25.8 (s)
11B: Ϫ25.8 (d, 1JBH = 87)
13C-{1H}: 83.6 (s, C5H5), 127.0 (br s, B(C6F5), Cipso), 136.63 (d, 1JCF = 256, B(C6F5), Cm), 138.02
(d, 1JCF = 237, B(C6F5), Cp), 148.36 (d, 1JCF = 229, B(C6F5), Co)
1H:f Ϫ18.2 (br s, Mo–H–B), Ϫ13.56 (s, 1H, MoH), 4.18 (s, 10H, C5H5), 4.6 (br s, 1H, BH)
11B-{1H}:f Ϫ12.1 (s)
[Mo(η-C5H5)2(H)(η1-H2B(C6F5)2)]
Blue
C, 44.5 (46.0); H, 1.75 (2.3); B, 1.6 (1.8)
IR:e 3600w, 3130w, 2964w, 2930w, 2866w,
2390w, 1724w, 1645m, 1516s, 1470s,
1405m, 1340m, 1308m, 1102s, 984s
[Mo(µ-C5H4Me)2(H)(η1-HB(C6F5)3)]
Blue
13C-{1H}:f 63.1 (s, C5H5). Remaining resonances not detected
7
8
1H:g Ϫ17.8 (br s, Mo–H–B), Ϫ7.01 (s, 1H, MoH), 1.27 and 1.45 (s, 3H, each, CH3), 3.73, 3.92,
4.04 and 4.23 (s, 2H each, C5H4CH3)
C, 47.1 (46.9); H, 2.5 (2.1)
[Re(η-C5H5)(η-C5H4B(C6F5)3)H2]h
Light brown
1H: Ϫ13.87 (s, 2H, ReH), 2.34 (s, 1.5H, H3CC6H5), 4.98 (s, 5H, C5H5), 5.07 and 5.16 (br s, 2H
each, C5H4B), 7.0–7.3 (m, 2.5H, H3CC6H5)
C, 43.4 (43.2); H, 2.0 (1.7); B, 0.9 (1.2)
11B-{1H}: Ϫ15.8 (s)
Mass: 852, [M ϩ Na]ϩ; 829, [M]ϩ; 828, 13C-{1H}: 74.63 and 77.60 (s, C5H4B), 76.63 (s, C5H5), 84.10 (br s, C5H4B, Cipso), 134.71 (d,
[M Ϫ H]ϩ; 662, [M Ϫ (C6F5)]ϩ; 512,
[B(C6F5)3]ϩ; 318, [M ϩ H Ϫ B(C6F5)3]ϩ;
317, [M Ϫ B(C6F5)3]ϩ; 167, [(C6F5)]ϩ
IR: 2727m, 1644s, 1515s, 1456s, 1273s,
1089s, 967s, 858m
1JCF = 232, B(C6F5), Cm), 136.76 (d, 1JCF = 243, B(C6F5), Cp), 148.20 (d, 1JCF = 222, B(C6F5), Co)c
9
[Ta(η-C5H5)2(H)2(η1-HB(C6F5)3)]
Light orange
1H:g Ϫ4.1 (br s, fwhh ca. 200 Hz, TaH2), 4.65 (s, 9H, C5H5), 5.08 (s, 23H, C5H5)
11B-{1H}:g Ϫ0.2 (s)
C, 40.7 (40.7); H, 1.7 (1.6); B, 1.5 (1.3)
Selected 13C-{1H}:g 91.60 (s, C5H5), 106.44 (s, C5H5)i
a Analytical data given as found (calculated) in %. Mass spectral data (fast atom bombardment) given as m/z (assignment), selected IR data (cmϪ1) as
Nujol mulls except where stated otherwise. b At probe temperature. Data given as: chemical shift (δ) (multiplicity, relative intensity, J in Hz,
assignment). Data obtained in CD2Cl2 except where stated otherwise. c B(C6F5), Cipso resonance not detected. d Two coincident peaks. e KBr disc.
f Data obtained in D3CC6D5. g Data obtained in C6D6. h Obtained with one half an equivalent of co-crystallised toluene. i Peaks in ca. 3:1 ratio.
Lewis base added either neat (THF or NEt3) or as a solution in
petroleum ether (PMe3). In all three cases, the solution quickly
became yellow and, where L = PMe3, there was precipitation of
poorly soluble Me3PؒB(C6F5)3. After 1 hour stirring, volatiles,
including any excess of the Lewis base, were removed under
vacuum and the reaction residues dissolved in C6D6 for analysis
by 1H and 11B-{1H} NMR spectroscopy.
For all three Lewis bases (L) almost total reaction of 1 to
give [W(η-C5H5)2H2] and the adducts LؒB(C6F5)3 had occurred.
The adducts were independently synthesised from B(C6F5)3
and L and characterised for the purpose of comparison.
The reaction between [Mo(η-C5H5)2H2] and B(C6F5)3 in either
toluene or petroleum ether yields a dark blue solid 5 even
at Ϫ78 ЊC. The product 5 was difficult to investigate owing
to its extreme insolubility in toluene and petroleum ether.
Dichloromethane causes fairly rapid decomposition of the
product to an intractable green solution but it was possible to
obtain NMR spectra. These strongly suggested that 5 could be
formulated as an adduct of the form [Mo(η-C5H5)2(H)(η1-HB-
(C6F5)3)] 5, since two resonances were observed in the hydride
1
region of the H NMR spectrum; a sharp peak at δ Ϫ6.21
in the region expected for a molybdenum-bound hydride
and a very broad signal at δ Ϫ17.5. The latter signal is assigned
to a Mo–H–B bridging hydride rather than abstracted
1
[HB(C6F5)3]Ϫ since the H NMR spectral shift of this anion
is known to occur at δ 3.98.2a Also, the proton-coupled 11B
1
NMR spectrum shows a doublet with JBH = 87 Hz, consistent
with other reported M–H–B bridging units.11 Infrared and
microanalytical data for 5 are also consistent with the proposed
formulation.
The Lewis base 4-methylpyridine was added to 5 in order to
support the proposal that it was a simple adduct (the (C6F5)3-
814
J. Chem. Soc., Dalton Trans., 2000, 813–820

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Table 2 Selected bond distances (Å) and angles (Њ) for compound 4
δ Ϫ13.56, which was assigned to a Mo–H moiety, and a broad
resonance at δ Ϫ18.2 attributed to a bridging Mo–H–B unit.
The other hydrogen bound to boron was observed at δ 4.59,
close to its position in the free borane (δ 4.5, fwhh = 25 Hz13)
but having a sharper appearance.
W(1)–H(202)
W(1)–H(203)
W(1)–H(204)
Cpcent–W(1)
CpЈcent–W(1)
1.49(5)
1.52(5)
1.41(6)
1.98
B(1)–Cl(1)
B(1)–C(20)
B(1)–C(30)
B(1)–C(1)
1.915(5)
1.652(6)
1.648(5)
1.637(6)
The 11B-{1H} NMR spectrum shows a single peak at δ Ϫ12.1
in the region typical for fourfold coordination of boron. No
splitting ascribable to protons appears on removal of proton-
decoupling; although it may be that the relatively large line
width of the signal precludes its observation. Unfortunately,
the solubility of 6 was too low to permit the weak (C6F5)
resonances to be observed in the 13C-{1H} NMR spectrum
and a sample in CD2Cl2 decomposed before spectra could be
acquired.
1.97
Cpcent–W–CpЈcent
H(202)–W–H(203)
Cpcent = centroid of (η5-C5H5) ring; CpЈcent = centroid of (η5-C5H4B-
(C6F5)2Cl) ring
145.9
54.8(27)
H(203)–W–H(204)
H(202)–W–H(204)
60.8(30)
115.6(33)
An infrared spectrum of 6 showed several strong bands in
the range 950–1500 cmϪ1 due to C–F absorptions; a broad band
at 1724 cmϪ1 is assigned to ν(Mo–H). The B–Hbridge stretch is
predicted to appear at around 2000 cmϪ1;11 however no peak
is observed in this region, it is possibly broadened into the
baseline. A weak absorption at 2390 cmϪ1 can be assigned to
the B–Hterminal stretch.
In view of the low solubility of both compounds 5 and 6
it was decided to study the reactions of B(C6F5)3 with the
alkyl-cyclopentadienyl compounds [Mo(η-C5H4R)2H2], where
R = Me, Pri or Bun. The reaction between [Mo(η-C5H4Me)2-
H2]14 and B(C6F5)3 gave a blue product [Mo(η-C5H4Me)2-
(H)(η1-HB(C6F5)3)] 7 which was more soluble in benzene than
was 5; however the improvement in solubility was insufficient
to obtain meaningful 13C-{1H} NMR spectral data. The iso-
propyl derivative, [Mo(η-C5H4Pri)2H2], was synthesised from
[MoCl4ؒdme], Na[C5H4Pri] and LiAlH4 following the method
of Persson and Andersson.15 Reaction with B(C6F5)3 in toluene
was slow, even on warming and although a different compound
was obtained, it was oily and could not be purified. No reaction
at all was observed between [Mo(η-C5H4Bun)2H2] and B(C6F5)3.
It is clear that adding longer chain alkyl substituents to the
cyclopentadienyl rings, although improving the solubility of
the adduct, also hinders the reaction considerably and increases
the oiliness of the products, so this approach was abandoned.
Lewis acid adducts of the d4 compound [Re(η-C5H5)2H] with
Fig.
1
Molecular structure of compound [W(η-C5H5)(η-C5H4-
{B(C6F5)2Cl})H3] 4.
16
17
BF3 and with AlX3 (X = Cl or Br) or AlHCl2 have been
described and have been assigned a structure where the Lewis
acid is attached to one of the two lone pairs on the rhenium
centre. However, in view of the reactivity of [W(η-C5H5)2H2]
BؒNC5H4(CH3) adduct had been independently synthesised
and characterised).12 Excess 4-methylpyridine was added to a
suspension of the blue adduct 5 in toluene and, over the course
of 2 days, the blue solid had vanished and the solution phase
became golden yellow. The NMR spectrum of this solution
revealed it to contain a mixture of [Mo(η-C5H5)2H2] and
(C6F5)3BؒNC5H4(CH3). The long reaction period may be attrib-
uted to the low solubility of compound 5 in toluene.
The reaction between [Mo(η-C5H5)2H2] and bis(pentafluoro-
phenyl)borane HB(C6F5)2 in toluene at Ϫ78 ЊC gave an
immediate colour change from yellow to red via orange. Upon
warming to ambient temperature and removal of volatiles
in vacuo, an olive-green oily solid was obtained which, after
washing thoroughly with petroleum ether (bp 40–60 ЊC),
afforded a blue powder [Mo(η-C5H5)2(H)(η1-H2B(C6F5)2)], 6
in 35% yield. Compound 6 could be crystallised from toluene
at Ϫ80 ЊC as needles which were not suitable for study by X-ray
diffraction.
The blue compound 6 shared many characteristics with
the product formed from [Mo(η-C5H5)2H2] and B(C6F5)3 (5),
being unstable both thermally and to air. The high air-
sensitivity precluded the acquisition of entirely satisfactory
microanalytical or mass spectral data. The solubility of 6
was somewhat greater than that of compound 5 and so NMR
spectra were obtained in d8-toluene. A single (C5H5) resonance
was observed in both the 1H and 13C-{1H} NMR spectra,
indicating that the Lewis acid had not added to a cyclopenta-
with B(C6F5)3, attack at
anticipated.
a cyclopentadienyl ring was
The hydride [Re(η-C5H5)2H] in petroleum ether (bp 100–
120 ЊC) was treated with one equivalent of B(C6F5)3. A light
brown precipitate formed immediately and was isolated by
filtration after 1 hour of stirring. Washing with petroleum ether
to remove excess starting materials failed to render the product
entirely pure so it was crystallised from toluene by slow cooling
to Ϫ80 ЊC which yielded brown microcrystals of the zwittionic
compound [Re(η-C5H5)(η-C5H4{B(C6F5)3})H2]ؒ0.5C6H5Me 8
in 65% yield.
1
The H NMR spectrum of 8 in CD2Cl2 showed a typical
pattern in the cyclopentadienyl region expected for the
proposed structure including a sharp resonance of relative
intensity 5 at δ 4.98, ascribable to the unsubstituted (η-C5H5)
ligand, and two broader signals, each of intensity 2, downfield
of this which are assigned to the (η-C5H4{B(C6F5)3}) ligand.
Only a single upfield resonance is observed, at δ Ϫ13.87, with a
relative intensity 2 and this may be assigned to the two identical
hydrides of an ReH2 group. Unlike the analogous tungsten
compound 1 compound 8 is stable in solution, and thus no
hydride resonance due to the starting material at δ Ϫ12.90 was
observed. Note that in the report of the [Re(η-C5H5)2H2]ϩ
cation in the literature18 the hydride also moves upfield when
compared to the starting monohydride, although not to such
a great extent as is observed here. Toluene is also observed
1
dienyl ring. Two H NMR spectroscopic resonances appeared
in the high field region of the spectrum, a sharp signal at
J. Chem. Soc., Dalton Trans., 2000, 813–820
815

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in the spectrum and integration of both the methyl peak and
the phenyl region indicates that there is one half an equivalent
of solvent present; this was supported by the microanalytical
data.
The 11B-{1H} NMR spectrum of 8 showed a single sharp
peak at δ Ϫ15.8 which remains a singlet in the absence of
decoupling, providing further evidence that the borane has not
added to a Re–H bond.
The 13C-{1H} NMR spectrum of 8 showed the resonances
expected except that of the ipso-C6F5 signal which was pre-
sumed either to be too weak or too broad to be located. As is
the case with compounds 1 to 4, assignment is straight-
forward with similar patterns being observed in both the
cyclopentadienyl and pentafluorophenyl regions in all five
complexes.
The infrared spectrum of compound 8 showed no bands
between 1650 cmϪ1 and 2400 cmϪ1 assignable to Re–H groups.
However, the infrared spectrum of the [Re(η-C5H5)2H2]ϩ cation
showed, at best, only very weak bands around 2000 cmϪ1 for
the Re–H stretch18 and later solution and matrix isolation
studies found no infrared-active Re–H stretch.19 A fast atom
bombardment mass spectrum of 8 showed several peaks
assignable to expected fragments of 8 and a weak peak for the
parent ion was observed at m/z = 829. Treatment of compound
8 with an excess of PMe3 in toluene gave only an extremely
small peak at δ Ϫ3.9 in the 11B-{1H} NMR spectrum due
1
to (C6F5)3BؒPMe3 and the resulting H NMR spectrum was
essentially that of 8.
Scheme 1 i B(C6F5)2R (where R = (C6F5), Ph, H or Cl) in petroleum
ether (bp 100–120 ЊC) at room temperature; ii add L (where L = Et3N,
PMe3 or THF).
The metallocene trihydride [Ta(η-C5H5)2H3] was treated with
one equivalent of B(C6F5)3 in toluene at room temperature.
A slow colour change from pale yellow to dark orange was
observed over 3 hours and then the volatiles were removed
under vacuum to yield an orange oil. Sonication in petroleum
ether for 15 minutes rendered a light orange powder of
[Ta(η-C5H5)2(H)2(η1-HB(C6F5)3)] 9. Microanalytical data were
correct for a 1:1 adduct, but unfortunately NMR spectroscopy
failed to confirm unambiguously that adduct formation had
occurred. The 11B-{1H} NMR spectrum showed a fairly sharp
resonance at δ Ϫ0.2 in the region expected for four-coordinate
boron, however there was no splitting visible on removal
of decoupling and the line width was of a sufficiently low
magnitude to lead one to expect that proton coupling should
be observable if a B–H unit existed.
Previous studies of the reaction of [Ta(η-C5H5)2H3] with
Lewis acids have found that attack occurs at the central
hydride ligand e.g. the reaction with triethylaluminium
described by Tebbe.20 In accord with this, one might therefore
1
expect that H NMR spectroscopy of the product from the
reaction with B(C6F5)3 would show a more or less unaltered B2
component and a shifted and broadened A component in the
hydride region of the spectrum. In actual fact, the only
observed upfield resonance is an extremely broad (fwhh = ca.
200 Hz), very weak signal centred at δ Ϫ4.1 which could pos-
sibly correspond to the borane rapidly hopping between all
three hydrides.
In conclusion, selected new compounds and their reactions
are shown in Schemes 1 and 2. Addition of the Lewis acid
B(C6F5)3 to metallocene hydrides occurs either at the M–H
bond or by initial exo-addition to a carbon of an η-cyclo-
pentadienyl ring. In the latter reaction this would result in a
η-cyclopentadiene ring, i.e. (η-C5H5{BR3}), and the compound
would have a formal electron count of 16-electrons. These com-
pounds are not observed and the isolated product results from
oxidative addition of the endo-C–H group of the (η-C5H5-
{BR3}) ligand to the metal centre resulting in the formation of
a zwiterrionic 18-electron compound. This reaction sequence is
illustrated in Scheme 1. The fact that [Mo(η-C5H5)2H2] adds
B(C6F5)3 to the Mo–H bond whilst for [W(η-C5H5)2H2] the
reaction with B(C6F5)3 proceeds via addition to the η-cyclo-
pentadienyl ring may be associated with the greater ease of
Scheme 2 i B(C6F5)3 in toluene at Ϫ78 ЊC, then triturate with petrol-
eum ether (bp 40–60 ЊC); ii 4-methylpyridine (L) in toluene for 2 days at
room temperature; iii B(C6F5)3 in petroleum ether (bp 100–120 ЊC) at
room temperature; iv B(C6F5)3 in toluene at room temperature.
oxidation of 6d transition metals compared with that for the
corresponding 5d metals. The tantalum trihydride is a d0 com-
pound so further oxidation is not possible; thus addition to
the Ta–H bonds is the only option. For the d4 compound
[Re(η-C5H5)2H] the observation that the product is formed by
exo-addition to the η-cyclopentadienyl ring followed by proton
816
J. Chem. Soc., Dalton Trans., 2000, 813–820

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Table 3 Selected bond lengths (Å) and angles (Њ) for compound 10
Re(1)–C(30)
Re(1)–Cpcent
Re(1)–CpЈcent
2.174(3)
1.90
1.88
C(1)–B(1)
B(1)–C(40)
B(1)–C(50)
1.526(3)
1.581(3)
1.602(3)
C(1)–B(1)–C(40)
C(1)–B(1)–C(50)
126.7(2)
115.2(2)
C(40)–B(1)–C(50)
115.70(18)
Fig.
2
Molecular structure of compound [Re(η-C5H5)(η-C5H4-
{B(C6F5)2})(C6F5)] 10.
migration to the metal is consistent with the analogous reaction
of [W(η-C5H5)2H2].
The reaction between [Re(η-C5H5)2CH3] and B(C6F5) in
1
dichloromethane was monitored by the H NMR spectra at
intervals of 10 ЊC from Ϫ80 to Ϫ10 ЊC. The 1H NMR spectrum
changed only slightly over the temperature range and the main
peaks observed initially showed only one resonance in the
C5H5 region (δ 4.25) together with one signal assignable to a
CH3-moiety (at δ 0.30). We note that the compound [Re-
(η-C5H5)2CH3] in CD2Cl2 has two peaks, at δ 4.27 (η-C5H5)
and 0.39 (CH3). The 11B-{1H} NMR spectrum shows a strong,
sharp peak at δ Ϫ15, its intensity dropped as the temperature
rose from Ϫ80 to Ϫ10 ЊC. The data are consistent with an initial
equilibrium between a mixture of [Re(η-C5H5)2(CH3)] ϩ
B(C6F5)3 and the adduct [Re(η-C5H5)2(CH3ؒB(C6F5)3)].
Unfortunately the 19F NMR spectra were broad and complex,
possibly due to hindered rotation and the sample was too dilute
to give meaningful 13C-{1H} NMR spectra. At Ϫ30 ЊC the
sample was still yellow but a yellow precipitate had formed
and it is this which accounts for the weakness of the 13C-{1H}
NMR spectrum.
Scheme 3 Mechanism proposed for the formation of 10.
Experimental
All preparations and manipulations of air and/or moisture
sensitive materials were carried out under an atmosphere of
dinitrogen using standard Schlenk line techniques or in an inert-
atmosphere glove-box containing dinitrogen. Dinitrogen was
purified before use by passage through a drying column filled
with activated molecular sieves (4 Å) and a de-oxygenating
column filled with either manganese() oxide suspended on
vermiculite (Schlenk line) or BASF catalyst (glove-box).
Solvents were pre-dried over activated 4 Å molecular sieves
and then distilled from sodium (petroleum ether (bp 100–
120 ЊC) and toluene), sodium/potassium alloy (pentane and
petroleum ether (bp 40–60 ЊC)) or potassium (THF) under
a slow continuous stream of dinitrogen. Deuterated solvents
for NMR spectroscopy were dried over calcium hydride
(dichloromethane) or potassium (benzene and toluene) and
de-oxygenated by three freeze–pump–thaw cycles.
As the sample was warmed from Ϫ10 to ϩ25 ЊC, the reaction
mixture changed steadily from yellow via orange to bright
1
red and gas evolution was observed. At the same time the H
NMR spectra developed two weak Re–hydride resonances, at
δ Ϫ12.32 and Ϫ11.83, whilst the C5H5 region showed 6 clear
peaks. The initially single bands attributed to the Re–methyl
group first split into two bands and these then broadened and
then disappeared. These changes in the methyl region were
accompanied by the development of unusually sharp bands
NMR spectra were recorded on a Bruker AM300 spec-
trometer (1H, 11B and 13C NMR spectra were recorded at
300.13, 96.25 and 75.5 MHz respectively). The spectra were
referenced internally using the residual protio-solvent (1H) and
solvent (13C) resonances and measured relative to tetramethylsi-
lane (δ = 0); or referenced externally to BF3ؒEt2O (11B, δ = 0).
Chemical shifts are quoted in δ (ppm); a positive sign indicates
a downfield shift relative to the standard. Coupling constants
are given in Hz. Fast atom bombardment mass spectra were
obtained by the EPSRC Mass Spectrometry Service at the
University College of Swansea under the supervision of Dr J.
A. Ballantine. Infrared spectra were recorded as Nujol mulls
between NaCl plates or as KBr discs on a Perkin-Elmer 1710
FTIR spectrometer in the range 400 to 4000 cmϪ1. Elemental
analyses were obtained by the microanalytical department of
the Inorganic Chemistry Laboratory. 4-Methylpyridine (99%)
and NEt3 (99%) were purchased from Aldrich and pre-dried
before use over activated 4 Å molecular sieves. [W(η-C5H5)2-
H2],15 PMe3,21 [Mo(η-C5H5)2H2],14 [Mo(η-C5H4Me)2H2],14 [Mo-
(η-C5H4Pri)2H2],15 [Mo(η-C5H4Bun)2H2],15 [Re(η-C5H5)2H],22
1
in the H NMR spectrum at δ Ϫ0.21 and for 13C-{1H} NMR
at δ Ϫ2. These latter bands can be assigned unambiguously
to CH4. After room temperature was reached these bands
assigned to CH4 had reduced in intensity due to the diminished
solubility of CH4 in CD2Cl2 with the increase of temperature.
This was confirmed by recooling the sample, which restored
the original intensity of the CH4 signal. After standing at
room temperature red crystals of 10 separated from
the reaction mixture and the crystal structure was determined.
The molecular structure of the compound 10 is shown in
Fig. 2 and selected distances and angles are given in Table 3.
The structure shows that the compound 10 has a Re–C6F5
group and a B(C6F5)2 group. The distance F(31)–C(31) is at
1.361(2) Å significantly longer than F(45)–C(45) at 1.347(3) Å.
Similar elongation is seen for the bond F(35)–C(35) when
compared to F(41)–C(41).
25
[Ta(η-C5H5)2H3],23 B(C6F5)3,5,7 PhB(C6F5)2,24 ClB(C6F5)2 and
HB(C6F5)2 13 were prepared by literature methods.
A possible mechanism for the formation of 10 is shown in
Scheme 3.
Preparations
In conclusion, the new reactions and compounds 1–10 are
shown in Schemes 1–3.
[W(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)3})H3] 1. To a stirred solution
J. Chem. Soc., Dalton Trans., 2000, 813–820
817

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of [W(η-C5H5)2H2] (0.316 g, 1.00 mmol) in petroleum ether
(bp 100–120 ЊC) (40 cm3) a solution of B(C6F5)3 (0.530 g, 1.04
mmol) in petroleum ether (bp 100–120 ЊC) (10 cm3) was added
dropwise. Immediate precipitation of a flocculant white solid
was observed and the solution rapidly lost its yellow colour.
Stirring was maintained for one hour after which time the
product was isolated by filtration, washed with petroleum
ether (bp 40–60 ЊC) (2 × 20 cm3) and dried in vacuo overnight.
It was shown to be pure by microanalysis. Yield: 0.750 g
(91%).
[Mo(ꢀ-C5H4Me)2(H)(ꢀ1-HB(C6F5)3)] 7. To a cold (Ϫ78 ЊC)
solution of [Mo(η-C5H4Me)2H2] (0.310 g, 1.21 mmol) in
toluene (20 cm3) was added a solution of B(C6F5)3 (0.620 g,
1.21 mmol) in toluene (20 cm3) with stirring. An immediate
colour change to dark blue was observed and the reaction was
allowed to warm to ambient temperature. Removal of volatiles
under vacuum afforded a blue oily solid which yielded a blue
powder after trituration with petroleum ether (bp 40–60 ЊC)
(2 × 30 cm3). The product purity was confirmed by micro-
analysis. Yield 0.5 g (54%).
[W(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)2(C6H5)})H3] 2. To a stirred
solution of [W(η-C5H5)2H2] (0.316 g, 1.00 mmol) in petroleum
ether (bp 100–120 ЊC) (30 cm3) was added dropwise a solution
of B(C6F5)2(C6H5) (0.430 g, 1.02 mmol) in petroleum ether (bp
100–120 ЊC) (15 cm3). Immediate precipitation of a flocculent
off-white solid was observed and the solution rapidly lost its
yellow colour. Stirring was maintained for thirty minutes after
which time the product was isolated by filtration, washed with
petroleum ether (bp 100–120 ЊC) (2 × 20 cm3) and dried in
vacuo overnight. It was shown to be pure by microanalysis.
Yield: 0.550 g (75%).
[Re(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)3})H2] 8. To a stirred solution
of [Re(η-C5H5)2H] (0.317 g, 1.00 mmol) in petroleum ether (bp
100–120 ЊC) (40 cm3) was slowly added a solution of B(C6F5)3
(0.530 g, 1.04 mmol) in petroleum ether (bp 100–120 ЊC)
(10 cm3). Immediate formation of a light brown precipitate
was observed and after 1 hour of stirring this was isolated
by filtration. The product was washed with petroleum ether
(bp 40–60 ЊC) (3 × 20 cm3) and recrystallised from toluene as a
brown microcrystalline solid at Ϫ80 ЊC. Purity as 8ؒ0.5C6H5Me
was confirmed by microanalysis and NMR spectroscopy. Yield:
0.53 g (65%).
[Ta(ꢀ-C5H5)2(H)2(ꢀ1-HB(C6F5)3)] 9. To a stirred solution
of [Ta(η-C5H5)2H3] (0.314 g, 1.00 mmol) in toluene (20 cm3)
was added a solution of B(C6F5)3 (0.512 g, 1.00 mmol) in
toluene (15 cm3). Over the course of 3 hours stirring, a slow
colour change from pale yellow to dark orange was observed.
After this time, volatiles were removed in vacuo to yield an
orange oil. Sonication of this compound in petroleum ether
(bp 40–60 ЊC) (20 cm3) for 15 minutes yielded the product as a
light orange powder which was isolated by filtration and dried
overnight under vacuum. Microanalysis confirmed that this
compound could be formulated as a 1:1 adduct of the two
starting materials; however, NMR spectroscopic data were not
straightforward. No further purification could be achieved by
crystallisation from toluene at Ϫ80 ЊC.
[W(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)2H})H3] 3. To a stirred solution
of [W(η-C5H5)2H2] (0.316 g, 1.00 mmol) in petroleum ether
(bp 100–120 ЊC) (40 cm3) was added dropwise a solution of
HB(C6F5)2 (0.355 g, 1.03 mmol) in petroleum ether (bp 100–
120 ЊC) (20 cm3). Rapid precipitation of a flocculent off-white
solid was observed and the solution lost its yellow colour. After
stirring for one hour, the product was isolated by filtration,
washed with petroleum ether (bp 100–120 ЊC) (30 cm3) then
petroleum ether (bp 40–60 ЊC) (2 × 30 cm3) and dried in vacuo
overnight. It was shown to be pure by microanalysis. Yield:
0.470 g (72%).
[W(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)2Cl})H3] 4. To a stirred solution
of [W(η-C5H5)2H2] (0.316 g, 1.00 mmol) in petroleum ether
(bp 100–120 ЊC) (20 cm3) was added dropwise a solution of
ClB(C6F5)2 (0.400 g, 1.05 mmol) in petroleum ether (bp 100–
120 ЊC) (10 cm3). Immediate precipitation of a flocculent grey-
white solid was observed and the solution rapidly lost its yellow
colour. Stirring was maintained for one hour after which time
the product was isolated by filtration, washed with petroleum
ether (bp 100–120 ЊC) (3 × 10 cm3) and dried in vacuo over-
night. Single crystals suitable for analysis by X-ray diffraction
were grown by slow evaporation at room temperature from
a solution of 4 (20 mg) in benzene (15 cm3) under a flow of
dinitrogen. Yield: 0.450 g (65%).
[Re(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)2})(C6F5)] 10. In an NMR tube,
a mixture of [Re(η-C5H5)2CH3] (0.016 g, 48 mmol) and
B(C6F5)3 (0.025 g, 49 mmol) was quickly cooled to liquid
nitrogen temperature. CD2Cl2 (0.8 cm3) was condensed onto
the mixture and the tube was flame-sealed. The sample
was then warmed to Ϫ80 ЊC, giving a yellow solution. The
NMR tube was transferred to the precooled (Ϫ80 ЊC) NMR
spectrometer and allowed to warm slowly to room temperature.
1
At intervals of 10 ЊC, the H NMR spectrum was recorded at
each temperature. After the sample reached room temperature
bright red microcrystals of 10 precipitated in the NMR tube.
The compound 10 is very sensitive to moisture, only sparingly
soluble in CH2Cl2 and almost insoluble in toluene and other
hydrocarbons. It reacts readily with donor atom solvents like
THF or DMSO, presumably to give the simple adducts.
Single crystals of 10 suitable for X-ray diffraction analysis
were grown by layering a solution of [Re(η-C5H5)2CH3] (0.050
g, 0.15 mmol) in CH2Cl2 (0.8 cm3) with neat CH2Cl2 (2.0 cm3)
followed by careful addition of a solution of B(C6F5)3 (0.075 g,
0.15 mmol) in CH2Cl2 (0.5 cm3) in an NMR tube fitted with a
Young’s tap. Crystallisation occurred on standing at room
temperature over one week to give dark red blocks. Estimated
yield ca. 50%.
[Mo(ꢀ-C5H5)2(H)(ꢀ1-HB(C6F5)3)] 5. To a cold (Ϫ78 ЊC)
solution of [Mo(η-C5H5)2H2] (0.550 g, 2.41 mmol) in toluene
(30 cm3) was added dropwise B(C6F5)3 (1.240 g, 2.42 mmol)
in toluene (30 cm3). A deep blue suspension formed immedi-
ately and stirring was maintained while the reaction mixture
was allowed to reach ambient temperature. The solvent was
removed under vacuum and the resulting dark blue oily solid
triturated with petroleum ether (bp 40–60 ЊC) (3 × 30 cm3) to
yield the product as a blue powder which was dried overnight
in vacuo. Yield: 1.1 g (62%).
[Mo(ꢀ-C5H5)2(H)(ꢀ1-H2B(C6F5)2)] 6. To a cold (Ϫ78 ЊC)
solution of [Mo(η-C5H5)2H2] (0.228 g, 1.00 mmol) in toluene
(25 cm3) a solution of HB(C6F5)2 (0.346 g, 1.00 mmol) in
toluene (30 cm3) was slowly added with stirring. The solution
gradually darkened from yellow through orange to red and was
allowed to reach ambient temperature. Removal of volatiles
under vacuum yielded an olive-green oily solid which afforded
a blue powder after trituration with petroleum ether (bp 40–
60 ЊC) (30 cm3). The product was crystallised from toluene
(Ϫ80 ЊC) as blue needles. Yield: 0.2 g (35%).
Reactions
Between [W(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)3})H3] 1 and L [where
L ؍ THF, NEt3 or PMe3]. To a solution of [W(η-C5H5)(η-
C5H4B(C6F5)3)H3] 1 (20 mg, 0.024 mmol) in toluene (10 cm3)
was added an excess of the Lewis base L; either THF (3 drops),
NEt3 (3 drops) or PMe3 (1 cm3 of a 0.105 M solution in
petroleum ether (bp 40–60 ЊC)). The solutions rapidly became
818
J. Chem. Soc., Dalton Trans., 2000, 813–820

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Table 4 Crystal structure data
located in the final difference map and their positions refined
with isotropic thermal parameters. A Chebychev weighting
scheme with the parameters 2.84, 0.362 and 2.06 was applied
as well as an empirical absorption correction.31 This yielded
R = 0.0264 and Rw = 0.0296 with maximum residual electron
density of 1.76 e ÅϪ3.
CCDC reference number 186/1803.
See http://www.rsc.org/suppdata/dt/a9/a908623d/ for crystal-
lographic files in .cif format.
4
10
Molecular formula
Formula weight
Crystal system
WClF10C22H12B
696.43
Triclinic
ReC28H9F15B
827.36
Orthorhombic
a/Å
b/Å
c/Å
α/Њ
8.470(4)
10.106(4)
13.403(3)
80.26(3)
74.88(3)
67.53(2)
1020.4
P1
2
125
6.01
5082
3795
0.00
0.0264
0.0296
15.427(3)
15.619(4)
19.877(2)
90.00
90.00
90.00
4789.4
Pbca
8
125
5.21
4766
β/Њ
Acknowledgements
We thank St John’s College, Oxford for a Junior Research
Fellowship (to L. H. D.) and the EPSRC for a graduate award
(to A. J. G.).
γ/Њ
V/Å3
¯
Space group
Z
T/K
µ/mmϪ1
Total data collected
Unique data
Merging R
R
References
3940
0.02
0.0238
0.0247
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Rw
yellow in colour and after the reactions had been allowed to
proceed for 1 hour, the volatiles were removed in vacuo and the
residues were dried for a further 2 hours. The products were
analysed by H and 11B-{1H} NMR spectroscopy and showed
1
that all three experiments gave virtually quantitative formation
of [W(η-C5H5)2H2] and (C6F5)3BؒL [L = THF, NEt3 or PMe3].
In the case where L = THF, a small amount (ca. 10%) of
[W(η-C5H5)(η-C5H4B(C6F5)3)H3] remained. Where L = PMe3,
some of the residue proved to be insoluble in C6D6 and this
was identified as (C6F5)3BؒPMe3 and an independent synthesis
of this adduct confirmed its insolubility in benzene.
2 (a) X. Yang, C. L. Stern and T. J. Marks, Angew. Chem., Int. Ed.
Engl., 1992, 31, 1375; (b) D. Röttger, S. Schmuck and G. Erker,
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1
NMR data for (C6F5)3BؒNEt3 (C6D6, 298 K): H, δ 0.51
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Soc., Dalton Trans., 1997, 1309; J. R. Galsworthy, J. C. Green,
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15; L. H. Doerrer, J. R. Galsworthy, M. L. H. Green and M. A.
Leech, J. Chem. Soc., Dalton Trans., 1998, 2483; L. H. Doerrer,
J. R. Galsworthy, M. L. H. Green, M. A. Leech and M. Müller,
J. Chem. Soc., Dalton Trans., 1998, 3191; M. L. H. Green,
G. Barrado, L. H. Doerrer and M. A. Leech, J. Chem. Soc., Dalton
Trans., 1999, 1061.
4 L. H. Doerrer, A. J. Graham and M. L. H. Green, J. Chem. Soc.,
Dalton Trans., 1998, 3941.
5 (a) M. L. H. Green, J. Haggitt and C. P. Mehnert, J. Chem. Soc.,
Chem. Commun., 1995, 1853; (b) A. N. Chernega, A. J. Graham,
M. L. H. Green, J. Haggitt, J. Lloyd, C. P. Mehnert, N. Metzler and
J. Souter, J. Chem. Soc., Dalton Trans., 1997, 2293.
(m, 9H, NCH2CH3), 1.62 (m, 6H, NCH2CH3); 11B-{1H},
δ Ϫ3.9 (s).
1
NMR data for (C6F5)3BؒTHF (C6D6, 298 K): H, δ 1.42
(m, 4H, C4H8O), 3.55 (m, 4H, C4H8O); 11B-{1H}, δ Ϫ3.7 (s).
Between [Mo(ꢀ-C5H5)2(H)(ꢀ1-HB(C6F5)3)] 5 and 4-methyl-
pyridine. To a suspension of [Mo(η-C5H5)2(H)(η1-HB(C6F5)3)]
5 (45 mg, 0.061 mmol) in toluene (5 cm3), excess 4-methyl-
pyridine (3 drops) was added. Over the course of 2 days’
stirring, the blue solid disappeared and the solution phase
became golden yellow. The volatiles were removed, the residue
dried overnight in vacuo and analysis by NMR spectroscopy
in C6D6 was undertaken. This allowed the products to be
identified as [Mo(η-C5H5)2H2] and (C6F5)3Bؒ4-methylpyridine
(which has been independently synthesised).
6 R. Gomez, M. L. H. Green and J. L. Haggitt, J. Chem. Soc., Dalton
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1
NMR data for (C6F5)3BؒNC5H4(CH3) (C6D6, 298 K): H,
δ 1.39 (s, 3H, NC5H4CH3), 6.14 (d, 2H, 3JHH = 6.5, NC5H4CH3,
Hm), 7.89 (d, 2H, 3JHH = 6.5, NC5H4CH3, Ho); 11B-{1H}, δ Ϫ4.0.
Between [Re(ꢀ-C5H5)(ꢀ-C5H4{B(C6F5)3})H2] 8 and PMe3.
The compound [Re(η-C5H5)(η-C5H4B(C6F5)3)H2] 8 (20 mg,
0.024 mmol) was dissolved in toluene (10 cm3) and PMe3
(1 cm3 of a 0.105 M solution in petroleum ether (bp 40–
60 ЊC), 0.105 mmol) was added with stirring. No immediate
colour change was evident and, after 1 hour, volatiles were
removed under vacuum and the residues were examined by
NMR spectroscopy. This revealed that compound 8 was present
unaltered.
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3916.
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Crystallography
31.
Data were collected as previously described,26 images were
processed with the DENZO and SCALEPACK programs.27
All solution, refinement and graphical calculations were per-
formed using the CRYSTALS28 and CAMERON29,30 software
packages. The three hydrogens bound to tungsten in 4 were
20 F. N. Tebbe, J. Am. Chem. Soc., 1973, 95, 5412.
21 M. L. Luetkens, A. P. Sattelberger, H. H. Murray, J. D. Basil and
J. P. Fackler, Inorg. Synth., 1989, 26, 7.
22 D. M. Heinekey and G. L. Gould, Organometallics, 1991, 10, 2977.
23 M. L. H. Green, J. A. McCleverty, L. Pratt and G. Wilkinson,
J. Chem. Soc., 1961, 4854.
J. Chem. Soc., Dalton Trans., 2000, 813–820
819

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25 R. D. Chambers and T. Chivers, Organomet. Chem. Rev., 1966, 1,
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26 L. H. Doerrer, M. L. H. Green, D. Häuβinger and J.
Saβmannhausen, J. Chem. Soc., Dalton Trans., 1999, 2111.
27 Z. Otwinowski and W. Minor, in Methods in Enzymology, Academic
Press, New York, 1996, vol. 276, p. 307.
29 D. J. Watkin, C. K. Prout and L. J. Pearce, CAMERON, Chemical
Crystallography Laboratory, University of Oxford, 1996.
30 A. Altomare, G. Cascarano, G. Giacovazzo, A. Guagliardi,
M. C. Burla, G. Polidori and M. Camalli, SIR92, Program for
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31 N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 158.
28 D. J. Watkin, C. K. Prout, J. R. Carruthers and P. W. Betteridge,
CRYSTALS User Guide, Issue 10, Chemical Crystallography
Laboratory, University of Oxford, 1996.
Paper a908623d
820
J. Chem. Soc., Dalton Trans., 2000, 813–820