Synthesis and characterisation of complexes of Group 13 metal amidinate heterocycles with the CpFe(CO)2 fragment

Article abstract of DOI:10.1039/b611758a

The first examples of complexes between a 4-membered amidinato-Group 13 metal(iii) heterocycle and a transition metal fragment are formed in salt elimination reactions between Na[CpFe(CO)₂] and [MX ₂(amid)], M = Al, Ga or In; X = Cl or Br; amid^- = [(RN)₂CBu^t]^-; R = Prⁱ or cyclohexyl (Cy). The formed complexes, [CpFe(CO)₂M(X)(amid)] (4 examples) have been crystallographically characterised and subject to halide abstraction reactions. In one case, the cationic complex, [CpFe(CO)₂Ga(OEt ₂){(CyN)₂CBu^t}][BAr^f₄], was isolated and crystallographically characterised. A hydrolysis product of this complex, [{CpFe(CO)₂Ga[(CyN)₂CBu^t]} ₂(-OH)][BAr^f₄], was also isolated in low yield from this reaction and structurally characterised. The Royal Society of Chemistry.

Full text of DOI:10.1039/b611758a

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Synthesis and characterisation of complexes of Group 13 metal amidinate
heterocycles with the CpFe(CO)2 fragment†
Cameron Jones,* Simon Aldridge,* Timo Gans-Eichler and Andreas Stasch
Received 15th August 2006, Accepted 20th September 2006
First published as an Advance Article on the web 29th September 2006
DOI: 10.1039/b611758a
The first examples of complexes between a 4-membered amidinato–Group 13 metal(III) heterocycle and
a transition metal fragment are formed in salt elimination reactions between Na[CpFe(CO)2] and
[MX2(amid)], M = Al, Ga or In; X = Cl or Br; amid− = [(RN)2CBut]−; R = Pri or cyclohexyl (Cy). The
formed complexes, [CpFe(CO)2M(X)(amid)] (4 examples) have been crystallographically characterised
and subject to halide abstraction reactions. In one case, the cationic complex,
[CpFe(CO)2Ga(OEt2){(CyN)2CBut}][BArf4], was isolated and crystallographically characterised. A
hydrolysis product of this complex, [{CpFe(CO)2Ga[(CyN)2CBut]}2(l-OH)][BArf4], was also isolated in
low yield from this reaction and structurally characterised.
2,4,6),8,9 via halide abstraction from the neutral complexes,
Introduction
[(C5R5)Fe(CO)2E(X)Rꢀ]8,10 using, for example, Na[BArf4], Arf =
The amidinate class of ligand, [RNC(Rꢀ)NR]−, has been utilised
C6H3(CF3)2-3,5. Of note here are the significant levels of Fe–B p-
in the formation of a multitude of complexes of metals from
bonding exhibited by the cationic iron borylene complexes. This is
across the periodic table.1 Complexes of Group 13 metals in
brought about by the presence of two empty p-orbitals at the boron
the +3 oxidation state have received particular attention as
centre and the cationic nature of the complexes which enhances
these have found a number of applications as, for example,
the overlap of symmetry related orbitals on the Fe and B centres.
If complexes of the type, [LnMꢀM(amid)]+, could be accessed, the
likely empty p-orbital at the Group 13 element centre may similarly
act as a p-acceptor and lead to a degree of metal–metal back
bonding. Our efforts in this direction are reported herein.
polymerisation catalysts and as materials precursors in chemical
vapour deposition processes.2,3 In this field we are interested in
exploiting sterically bulky amidinates and related guanidinates,
[RNC(NRꢀ2)NR]−, in the stabilisation of thermally labile frag-
ments, e.g. indium and gallium hydrides.4 In addition, we have
recently been successful in forming the first Group 13 metal(I)
and (II) complexes incorporating amidinate and/or guanidinate
ligands.5 Of most note are the monomeric, 4-membered, N,N-
chelated metal(I) heterocycles, [:M{(Ar)NC(NCy2)N(Ar)}], M =
Ga or In, Ar = C6H3Pri2-2,6, Cy = cyclohexyl. Theoretical studies
on models of these compounds suggest that they should act as
good r-donor ligands to transition metal fragments, as is now well
known for Group 13 metal diyls, :M(I)R.6
Although we are examining this possibility with some success,7
an alternative synthetic route to complexes between transition
metal fragments and less bulky Group 13-amidinate heterocycles
would be attractive as this would allow a wider range of complex
types to be accessed. It seemed that the reaction of amidinate
metal(III) dihalides, [(amid)MX2], (amid = general amidinate)
with anionic transition metal fragments, [MꢀLn]−, could give
complexes of the type, [LnMꢀM(X)(amid)], halide abstraction
from which could yield cationic complexes, [LnMꢀM(amid)]+.
There are close parallels here with the formation of cationic
iron borylene and related complexes, e.g. [(C5R5)Fe(CO)2BRꢀ]+
or [{(C5R5)Fe(CO)2EMes*}2(l-X)]+ (R = H or Me, Rꢀ = aryl
or amido, E = Ga or In, X = Cl or Br, Mes* = C6H2But3-
Results and discussion
In order to access precursors suitable for halide abstraction
reactions, suspensions of Na[CpFe(CO)2] in diethyl ether were
treated with the amidinato Group 13 dihalides, 1(a–d), to give
the neutral complexes, 2(a–d), in moderate yields after work-
up (Scheme 1). Although 1(a–c) were prepared by literature
procedures, 1(d) has not previously been reported and its synthesis
and spectroscopic details can be found in the experimental
Centre for Fundamental and Applied Main Group Chemistry, School of
Chemistry, Main Building, Cardiff University, Cardiff, UK CF10 3AT.
E-mail: jonesca6@cardiff.ac.uk
† Electronic supplementary information (ESI) available: ORTEP diagrams
and selected bond lengths and angles for 2(a) and 2(c). See DOI:
10.1039/b611758a
Scheme 1 i) Na[Fp], Et2O, −NaX; ii) Na[BArf4], CH2Cl2–Et2O, −NaCl
(M = Ga, X = Cl, R = Cy); iii) trace H2O, CH2Cl2–Et2O.
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section. The spectroscopic data for 2 are consistent with their
proposed monomeric structures and all display two CO stretching
absorptions in their infrared spectra (e.g. 2(b): mCO 1985, 1933 cm−1)
at wavenumbers close to those previously reported for related
complexes, e.g. [CpFe(CO)2E(X)Mes*]; E = Ga, X = Cl (mCO 1999,
1952 cm−1); E = In, X = Br (mCO 1996, 1945 cm−1).10
X-Ray crystal structure analyses were carried out on complexes
2(a–d), which are the first structurally authenticated complexes of
4-membered Group 13 metal heterocycles with transition metal
fragments. An analysis of the crystallographic data revealed 2(a–
c) to be structurally similar (2(a) and 2(b) are isomorphous) and
thus only the molecular structure of 2(b) is depicted in Fig. 1 (see
also Table 1). The halide ligands of these monomeric complexes
effectively adopt an anti-conformation with respect to the Fe–Cp
linkage, as evidenced by their halide–M–Fe–Cp centroid torsion
angles (2(a) 176.6◦, 2(b) 177.9◦, 2(c) 171.7◦). In contrast, the In–
Br bond in 2(d) (Fig. 2, see Table 1) adopts a conformation with
respect to the Fe–Cp unit which is closer to a syn-disposition
(Br–In–Fe–Cp centroid torsion angle: 45.8◦). These differences
possibly occur because the increased Fe–M bond length in 2(d)
may reduce the steric interaction between the CpFe(CO)2 fragment
and the indium heterocycle thereby allowing a more free rotation
about the M–Fe bond than is possible in the other compounds.
Saying this, the effects of crystal packing forces cannot be ruled
out as a reason.
Fig. 1 Molecular structure of 2(b) (hydrogen atoms omitted for clarity;
˚
ellipsoids shown at the 25% probability level). Selected bond lengths (A)
and angles (◦): Ga(1)–N(2) 1.984(2), Ga(1)–N(1) 1.987(2), Ga(1)–Cl(1)
2.2294(8), Ga(1)–Fe(1) 2.3540(6), N(1)–C(1) 1.341(4), N(2)–C(1)
1.347(3); N(2)–Ga(1)–N(1) 66.39(9), N(2)–Ga(1)–Cl(1) 104.45(7), N(1)–
Ga(1)–Cl(1) 106.18(8), N(2)–Ga(1)–Fe(1) 130.24(8), N(1)–Ga(1)–Fe(1)
124.29(7), Cl(1)–Ga(1)–Fe(1) 115.20(3), N(1)–C(1)–N(2) 108.0(2).
In all complexes, the amidinate ligands appear to be largely
delocalised while the N–M and M–Fe distances lie within the
reported ranges.11 It is of interest that the Fe–M bond length of 2(a)
is slightly longer than those of 2(b) and 2(c). This is, however, in
line with the now established larger covalent radius of aluminium
5358 | Dalton Trans., 2006, 5357–5361
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complexes 3 and 4 (Scheme 1). Compound 3 doubtless results from
chloride abstraction and subsequent coordination of the generated
3-ccordinate gallium centre by a molecule of diethyl ether. This
is reminiscent of the formation of the Lewis base adducts,
[CpFe(CO)2B(L)NCy2]+ (L = THF or 4-picoline), which arise
from the treatment of the borylene complex, [CpFe(CO)2BNCy2]+,
with the donor (L).8a Compound 4 was obtained in low yield (<
5%) and almost certainly arises from the hydrolysis of 3 by traces
of water in the reaction mixture.
The spectroscopic data for 3 are consistent with its proposed
formulation. Of most note is its infrared spectrum which exhibits
CO stretching bands (mCO 2007 cm−1, 1958 cm−1) which are shifted
to higher wavenumbers by ca. 20 cm−1 relative to those in the
precursor complex, 2(b), as expected for a cationic complex.
Because of the low yield of 4, no meaningful spectroscopic data
could be obtained for this compound.
The structures of the cationic components of 3 and 4 are
depicted in Fig. 3 and 4 respectively. During the course of
refinement, the asymmetric unit of 3 was found to contain
two crystallographically independent cations and anions. No
significant geometric differences were found between the two and,
accordingly, geometric parameters for only one are reported here.
A relatively high R-factor was obtained for this structure due to
extensive disorder in the [BArf4]− counter-ions. Despite this, the
connectivity within the cations is unambiguous. The gallium centre
of 3 has a distorted tetrahedral geometry, very similar to that in
2(b). As a result, there is no possibility of any Fe–Ga p-bonding
in this complex. Its Ga–Fe and Ga–N bonds are slightly shorter
than those in the precursor molecule, an observation that can be
attributed to a contracted gallium radius in the cationic complex.
The structure of the cation of 4 shows it also to have distorted
Fig. 2 Molecular structure of 2(d) (hydrogen atoms omitted for clarity;
ellipsoids shown at the 25% probability level). Selected bond lengths
◦
˚
(A) and angles ( ): In(1)–N(2) 2.178(2), In(1)–N(1) 2.190(2), In(1)–Fe(1)
2.5151(7), In(1)–Br(1) 2.5652(11), N(1)–C(1) 1.337(3), N(2)–C(1) 1.336(3);
N(2)–In(1)–N(1) 60.40(8), N(2)–In(1)–Fe(1) 129.09(7), N(1)–In(1)–Fe(1)
125.21(7), N(2)–In(1)–Br(1) 103.81(7), N(1)–In(1)–Br(1) 108.29(7),
Fe(1)–In(1)–Br(1) 117.06(3), N(2)–C(1)–N(1) 110.6(2).
12
˚
˚
(1.30 A) versus gallium (1.25 A). The difference between these
radii is not reflected in the magnitudes of the N–M–N angles of
the complexes, which become narrower with increasing molecular
weight of the metal. An examination of the M–X bonds of the
compounds showed them to be unexceptional and close to the
˚
means for previously reported terminal interactions (Al–Cl 2.13 A,
11
˚
˚
Ga–Cl 2.18 A, In–Br 2.55 A).
In order to prepare cationic complexes with 3-coordinate
Group 13 centres, 2(a–d) were treated with one equivalent of
Na[BArf4] in dichloromethane. Although this halide abstraction
methodology has proved successful for related complexes, e.g.
[(C5R5)Fe(CO)2E(X)Mes*] (R = H, E = Ga, X = Cl; R = Me,
E = In, X = Br),10 no reactions were observed with 2, despite
extended reaction times. It is not known why these differences
occur but reasons could include the presumably more hindered
4-coordinate Group 13 centres in the latter relative to the 3-
coordinate centres in the former. In addition, the M–X bonds
in the latter are shorter and probably stronger than those in the
former despite their 4-coordinate Group 13 metal centres. This
shortening is likely a result of a negative inductive effect of the
electronegative N-centres of the amidinate ligands in 2. Saying
this, a chloride abstraction from a similarly hindered 4-coordinate
gallium centre (in [(nacnac)Ga–Au–Ga(Cl)(nacnac)], nacnac =
(ArNCMe)CH−) has recently been reported.13
Fig. 3 Structure of the cationic component of 3 (hydrogen atoms omitted
Repeating the halide abstraction reactions in the presence of a
donor solvent, diethyl ether, met with mixed success. Again, 2(a)
remained unreactive towards Na[BArf4], presumably because of
the relative strength of its M–X bond, whilst reactions with 2(b–
d) did occur. However, only in the case of the reaction with 2(b)
could products be isolated from the reaction mixture, viz. the ionic
for clarity; ellipsoids shown at the 25% probability level). Selected bond
◦
˚
lengths (A) and angles ( ): Ga(1)–N(1) 1.958(7), Ga(1)–N(2) 1.963(6),
Ga(1)–O(1) 2.042(6), Ga(1)–Fe(1) 2.3183(15), N(1)–C(1) 1.340(11),
N(2)–C(1) 1.335(10); N(1)–Ga(1)–N(2) 66.8(3), N(1)–Ga(1)–O(1) 98.0(3),
N(2)–Ga(1)–O(1) 100.1(3), N(1)–Ga(1)–Fe(1) 130.1(2), N(2)–Ga(1)–Fe(1)
131.1(2), O(1)–Ga(1)–Fe(1) 117.78(17), N(2)–C(1)–N(1) 107.7(7).
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Spectrometry Service at Swansea University. Microanalyses were
obtained from Medac Ltd. Where reproducible microanalyses
could not be obtained, accurate mass spectra were obtained,
except for compound 3. The NMR spectra of this compound
suggested its purity was greater than 98%. IR spectra were
recorded using a Nicolet 510 FT-IR spectrometer as Nujol
mulls between NaCl plates, or as solutions in CH2Cl2. Melting
points were determined in sealed glass capillaries under argon,
and are uncorrected. Na[CpFe(CO)2],15 [AlCl2{(CyN)2CBut}],2e
[GaCl2{(RN)2CBut}] (R = Cy or Pri)2c and Na[BArf4]16 were
synthesised by literature procedures whilst all other chemicals were
obtained from commercial sources and used as supplied.
Syntheses
Preparation of [InBr2{(CyN)2CBut}] 1(d). A suspension of
[Li{(CyN)2CBut}] (1.30 g, 5.6 mmol) in diethyl ether (30 cm3)
was added over 5 min to a suspension of InBr3 (1.71 g, 4.8 mmol)
in diethyl ether (30 cm3) at 0 ◦C. After warming to 20 ◦C and
stirring for 2 h, volatiles were removed from the reaction mixture
in vacuo and the residue extracted with hot toluene (50 cm3) and
filtered. The filtrate was concentrated to 10 cm3 and placed at
−30 ◦C yielding 1(d) as colourless crystals. Mp: 190–192 ◦C (Yield:
2.50 g, 93%). 1H NMR (400 MHz, C6D6): d 1.10 (s, 9H, C(CH3)3),
Fig. 4 Structure of the cationic component of 4 (hydrogen atoms omitted
for clarity; ellipsoids shown at the 25% probability level). Selected bond
◦
˚
lengths (A) and angles ( ): Ga(1)–O(1) 1.971(3), Ga(1)–N(2) 1.986(5),
Ga(1)–N(1) 1.998(5), Ga(1)–Fe(1) 2.3354(11), Ga(2)–O(1) 1.975(3),
Ga(2)–N(3) 1.987(4), Ga(2)–N(4) 1.993(5), Ga(2)–Fe(2) 2.3148(12),
N(1)–C(1) 1.341(8), N(2)–C(1) 1.330(8), N(3)–C(25) 1.347(7), N(4)–
C(25) 1.335(7); O(1)–Ga(1)–N(2) 96.29(19), O(1)–Ga(1)–N(1)
103.29(19), N(2)–Ga(1)–N(1) 66.1(2), O(1)–Ga(1)–Fe(1) 122.83(12),
N(2)–Ga(1)–Fe(1) 126.86(15), N(1)–Ga(1)–Fe(1) 126.20(15), O(1)–
Ga(2)–N(3) 97.90(18), O(1)–Ga(2)–N(4) 105.04(19), N(3)–Ga(2)–N(4)
66.37(19), O(1)–Ga(2)–Fe(2) 116.22(12), N(3)–Ga(2)–Fe(2) 130.03(14),
N(4)–Ga(2)–Fe(2) 129.49(15), N(2)–C(1)–N(1) 108.9(5), N(4)–C(25)–
N(3) 108.6(5).
1
0.92–1.60 (m, 20H, CH2), 3.74 (m, 2H, CH); 13C{ H} NMR
(75.57 MHz, C6D6): d 25.2, 25.3, 38.4 (CH2), 29.2 (C(CH3)3),
39.6 (C(CH3)3), 55.7 (CH), 176.4 (NCN); (MS/EI) m/z : 536
[M+, 6%], 262 [M+ − InBr2, 100%]; acc. mass MS (EI): calc. for
C17H31N2Br2In 535.9887, found 535.9887.
tetrahedral gallium centres with iron–gallium separations similar
to those in 3. These centres are effectively symmetrically bridged
by a hydroxide ligand with a Ga–O–Ga angle of 163.0(2)◦
and Ga–O distances similar to those previously reported for
Preparation of [CpFe(CO)2Al(Cl){(CyN)2CBut}] 2(a). To a
suspension of Na[CpFe(CO)2] (300 mg, 1.50 mmol) in diethyl ether
(20 cm3) at −78 ◦C was added a solution of [AlCl2{(CyN)2CBut}]
(500 mg, 1.40 mmol) in diethyl ether (20 cm3). After warming
˚
hydroxy bridged digallium fragments, e.g. 1.965 A (mean) in
(Me3Si)3CGa(Me)(OH)(l-OH)GaC(SiMe3)3(Me)(OH2).14
◦
to 20 C and stirring for 18 h, the reaction mixture was filtered
and the filtrate concentrated to ca. 10 cm3. This was stored at
−30 ◦C overnight, affording 2(a) as yellow crystals. Mp: 159–
161 ◦C (Yield: 150 mg, 21%). 1H NMR (400 MHz, C6D6): d
1.25 (s, 9H, C(CH3)3, 1.21–2.21 (m, 20H, CH2), 3.30 (m, 2H,
Conclusion
In summary, the first examples of complexes in which 4-membered
amidinato–Group 13 heterocycles act as ligands towards transi-
tion metal fragments have been described. Neutral examples of the
form [CpFe(CO)2M(X)(amid)] have been readily accessed via salt
elimination reactions between Na[CpFe(CO)2] and [MX2(amid)].
Halide abstraction from one example has yielded the cationic
complex, [CpFe(CO)2Ga(OEt2){(CyN)2CBut}][BArf4], the gal-
lium centre of which is coordinated by a molecule of diethyl ether,
thus precluding any Fe–Ga p-backbonding in this complex.
1
CH), 4.52 (s, 5H, CpH); 13C{ H} NMR (126.0 MHz, C6D6): d
25.7, 26.1, 35.5 (CH2), 29.5 (C(CH3)3), 39.4 (C(CH3)3), 56.0 (CH),
82.2 (Cp), 179.0 (NCN), CO resonance not observed; IR m/cm−1
(CH2Cl2): 1974, 1914 (CO); (MS/EI) m/z : 502 [M+, 15], 446
[M+ − 2CO, 14], 325 [M+ − CpFe(CO)2, 100]; acc. mass MS (EI):
calc. for C24H36O2N2FeClAl 502.1625, found 502.1625; anal.: calc
for C24H36O2N2FeClAl C 57.33, H 7.22, N 5.57; found C 56.85, H
7.34, N 5.68.
Similar synthetic procedures were used for 2(b–d)
Experimental
[CpFe(CO)2Ga(Cl){(CyN)2CBut}] 2(b). Mp: 151–153 ◦C
(Yield: 31%). 1H NMR (400 MHz, C6D6): d 1.30 (s, 9H, C(CH3)3),
1.21–2.29 (m, 20H, CH2), 3.81 (m, 2H, CH), 4.47 (s, 5H, CpH);
General considerations
All manipulations were carried out using standard Schlenk and
glove box techniques under an atmosphere of high purity argon.
Hexane and toluene were distilled over potassium whilst diethyl
ether was distilled over Na/K then freeze/thaw degassed prior
1
13C{ H} NMR (126.0 MHz, C6D6): d 24.4, 24.7, 35.4 (CH2), 28.2
(C(CH3)3), 37.6 (C(CH3)3), 54.4 (CH), 81.1 (Cp), 173.1 (NCN),
214.8 (CO); IR m/cm−1 (CH2Cl2): 1985, 1933 (CO); (MS/EI) m/z :
544 [M+, 5], 488 [M+ − 2CO, 20], 368 [M+ − CpFe(CO)2, 100];
acc. mass MS (EI): calc. for C24H36O2N2FeClGa 544.1065, found
544.1069; anal. calc for C24H36O2N2FeClGa C 52.84, H 6.65, N
5.13; found C 52.18, H 6.61, N 5.14%.
1
1
to use. H and 13C{ H} NMR spectra were recorded on either a
Bruker DXP400 or a JEOL Eclipse 300 plus spectrometer and
were referenced to the residual 1H or 13C resonances of the solvent
used. Mass spectra were obtained from the EPSRC National Mass
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[CpFe(CO)2Ga(Cl){(PriN)2CBut}] 2(c). Mp: 120–122 ◦C
(Yield: 52%). 1H NMR (400 MHz, C6D6): d 1.21 (d, 3JHH = 6.1 Hz,
non-hydrogen atoms are anisotropic with H-atoms included in
calculated positions (riding model). Crystal data, details of data
collections and refinement are given in Table 1.
CCDC reference numbers 617851–657856.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b611758a
3
6H, CH(CH3)2), 1.23 (s, 9H, C(CH3)3), 1.49 (d, JHH = 6.1 Hz,
6H, CH(CH3)2), 4.13 (sept, 3JHH = 6.1 Hz, 2H, CH(CH3)2), 4.43
1
(s, 5H, CpH); 13C{ H} NMR (126.0 MHz, C6D6): d 24.5, 24.7,
(CH(CH3)2), 28.1 (C(CH3)3), 37.6 (C(CH3)3), 45.7 (CH), 81.1
(Cp), 173.7 (NCN), 215.0 (CO); IR m/cm−1 (Nujol): 1980, 1921
(CO); (MS/EI) m/z : 465 [M+, 5], 437 [M+ − CO, 26], 408 [M+ −
2CO, 35]; anal.: calc for C18H28O2N2FeClGa C 46.45, H 6.06, N
6.02; found C 45.85, H 5.98, N 5.73%.
Acknowledgements
We thank the EPSRC (postdoctoral fellowship for T.G.-E.) for
financial support. The EPSRC Mass Spectrometry Service at
Swansea University is also thanked.
◦
[CpFe(CO)2In(Br){(CyN)2CBut}] 2(d). Mp: 96–98 C (Yield:
37%)1H NMR (400 MHz, C6D6): d 1.34 (s, 9H, C(CH3)3), 1.22–
1
2.32 (m, 20H, CH2), 3.93 (m, 2H, CH), 4.43 (s, 5H, CpH); 13C{ H}
References
NMR (75.6 MHz, C6D6): d 25.1, 25.7, 38.2 (CH2), 29.7 (C(CH3)3),
40.1 (C(CH3)3), 55.5 (CH), 81.4 (Cp), 174.0 (NCN), 215.1 (CO);
IR m/cm−1 (CH2Cl2): 1989, 1938 (CO); (MS/EI) m/z : 634 [M+, 4],
606 [M+ − CO, 20], 578 [M+ − 2CO, 26], 368 [M+ − CpFe(CO)2,
100]; acc. mass MS (EI): calc. for C24H36O2N2FeBrIn 634.0343,
found 634.0347.
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[CpFe(CO)2Ga(OEt2){(CyN)2CBut}][BArf4] 3. To a suspen-
sion of Na[BArf4] (270 mg, 0.30 mmol) in dichloromethane–diethyl
◦
ether (10 cm3) at −78 C was added a solution of 2(b) (150 mg,
0.27 mmol) in dichloromethane (10 cm3◦). After stirring for 1 h
the reaction mixture was warmed to 20 C and stirred for 17 h.
The resultant suspension was filtered, the filtrate concentrated to
ca. 2 cm3 and layered with hexane (10 cm3). Storage for 48 h at
−30 ◦C afforded 3 as colourless crystals. Mp 133–135◦ (Yield:
200 mg, 52%). (NB: a small amount of the hydrolysis product,
4, was also isolated. Attempts to prepare this compound by the
reaction of 3 with 0.5 equivalent of H2O led only to low yields (<
5 (a) C. Jones, P. C. Junk, J. A. Platts and A. Stasch, J. Am. Chem. Soc.,
2006, 128, 2206; (b) C. Jones, P. C. Junk, M. Kloth, K. M. Proctor and
A. Stasch, Polyhedron, 2006, 25, 1592; (c) C. Jones, P. C. Junk, J. A.
Platts, D. Rathmann and A. Stasch, Dalton Trans., 2005, 2497.
6 G. Gemel, T. Steinke, M. Cokoja, A. Kempter and R. A. Fischer,
Eur. J. Inorg. Chem., 2004, 4161 and references therein.
7 C. Jones and A. Stasch, manuscript in preparation.
1
5%) of 4 and other unidentified products.) H NMR (400 MHz,
8 (a) S. Aldridge, C. Jones, T. Gans-Eichler, A. Stasch, D. L. Kays (ne´e
Coombs), N. D. Coombs and D. J. Willock, Angew. Chem., Int. Ed.,
2006, 45, 6118; (b) D. L. Coombs, S. Aldridge, C. Jones and D. J.
Willock, J. Am. Chem. Soc., 2003, 125, 6356; (c) D. L. Coombs, S.
Aldridge, A. Rossin, C. Jones and D. J. Willock, Organometallics, 2004,
23, 2911; (d) D. L. Kays (ne´e Coombs), J. K. Day, L.-L. Ooi and S.
Aldridge, Angew. Chem., Int. Ed., 2005, 44, 7457.
9 N. R. Bunn, S. Aldridge, D. L. Kays (ne´e Coombs), N. D. Coombs,
A. Rossin, D. J. Willock, J. K. Day, C. Jones and L.-L. Ooi,
Organometallics, 2005, 24, 5891.
10 N. R. Bunn, S. Aldridge, D. L. Kays (ne´e Coombs), N. D. Coombs, J. K.
Day, L.-L. Ooi, S. J. Coles and M. B. Hursthouse, Organometallics,
2005, 24, 5879.
11 As determined from a survey of the Cambridge Crystallographic
Database, August, 2006.
3
CD2Cl2): d 1.15 (t, JHH = 3.3 Hz, 6H, CH3CH2O), 1.28 (s, 9H,
C(CH3)3), 0.96–1.84 (m, 20H, CH2), 3.65 (m, 2H, CH), 3.75 (q,
3JHH = 3.3 Hz, 4H, CH3CH2O), 4.81 (s, 5H, CpH), 7.41 (s, 4H,
1
p-CH of [BArf4]−), 7.56 (s, 8H o-CH of [BArf4]−); 13C{ H} NMR
(126.0 MHz, CD2Cl2): d 14.3 (CH3CH2O), 25.5, 27.8, 33.9 (CH2),
29.5 (C(CH3)3), 37.4 (C(CH3)3), 55.9 (CH), 65.9 (CH3CH2O), 83.4
1
(Cp), 117.9 (p-CH of [BArf4]−), 124.9 (q, JCF = 269 Hz, CF3),
129.1 (q, 2JCF = 34 Hz, m-C of [BArf4]−), 137.6 (o-CH of [BArf4]−),
1
162.1 (q, JCB = 50 Hz, ipso-C of [BArf4]−), 180.1 (NCN), 213.3
(CO); IR m/cm−1 (CH2Cl2): 2002, 1941 (CO); (MS/EI) m/z : 262
[CyN(H)C(But)NCy+, 100].
12 (a) R. J. Wright, M. Brynda and P. P. Power, Angew. Chem., Int. Ed.,
2006, 45, 5953; (b) W. Uhl, Adv. Organomet. Chem., 2004, 51, 53.
13 A. Kempter, C. Gemel, M. J. Hardman and R. A. Fischer, Inorg. Chem.,
2006, 45, 3133.
X-Ray crystallography
Crystals of 2(a–d), 3 and 4 suitable for X-ray structural determina-
tion were mounted in silicone oil. Crystallographic measurements
were made using a Nonius Kappa CCD diffractometer. The
structures were solved by direct methods and refined on F2 by
full matrix least squares (SHELX97)17 using all unique data. All
14 C. Schnitter, H. W. Roesky, T. Albers, H.-G. Schmidt, C. Ropken, E.
Parisini and G. M. Sheldrick, Chem.–Eur. J., 1997, 3, 1783.
15 R. B. King and M. B. Bisnette, J. Organomet. Chem., 1967, 8, 287.
16 D. L. Reger, T. D. Wright, C. A. Little, J. J. S. Lamba and M. D. Smith,
Inorg. Chem., 2001, 40, 3810.
17 G. M. Sheldrick, SHELX-97, University of Go¨ttingen, Germany, 1997.
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 5357–5361 | 5361
©