Synthesis, characterisation and reactivity of germanium(ii) amidinate and guanidinate complexes

Article abstract of DOI:10.1039/b801168k

Reactions of lithium salts of the bulky guanidinate ligands, [ArNC(NR ₂)NAr]^- (NR₂ = N(C₆H ₁₁)₂ (Giso^-) and cis-NC₅H ₈Me₂-2,6 (Pipiso^-); Ar = C₆H ₃Prⁱ₂-2,6), with GeCl₂?dioxane afforded the heteroleptic germylenes, [(Giso)GeCl] and [(Pipiso)GeCl], the former of which was structurally characterised. The further reactivity of these and the related complexes, [(Piso)GeCl] and [(Priso)GeCl] (Piso^- = [ArNC(Bu^t)NAr]^-, Priso^- = [ArNC(NPr ⁱ₂)NAr]^-) has been investigated. Salt elimination reactions have yielded the new monomeric complexes, [(Piso)Ge(NPrⁱ₂)] and [(Piso)GeFeCp(CO)₂], whilst a ligand displacement reaction afforded the heterometallic species, [(Piso)Ge(Cl){W(CO)₅}]. Chloride abstraction from [(Priso)GeCl] with GaCl₃ has given the structurally characterised contact ion pair, [(Priso)Ge][GaCl₄]. In addition, the inconclusive outcome of a number of attempts to reduce the germanium halide complexes are discussed. The Royal Society of Chemistry.

Full text of DOI:10.1039/b801168k

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis, characterisation and reactivity of germanium(II) amidinate and
guanidinate complexes†
Cameron Jones,*a Richard P. Roseb and Andreas Stascha
Received 22nd January 2008, Accepted 13th March 2008
First published as an Advance Article on the web 17th April 2008
DOI: 10.1039/b801168k
Reactions of lithium salts of the bulky guanidinate ligands, [ArNC(NR2)NAr]− (NR2 = N(C6H11)2
(Giso−) and cis-NC5H8Me2-2,6 (Pipiso−); Ar = C6H3Pri2-2,6), with GeCl2·dioxane afforded the
heteroleptic germylenes, [(Giso)GeCl] and [(Pipiso)GeCl], the former of which was structurally
characterised. The further reactivity of these and the related complexes, [(Piso)GeCl] and [(Priso)GeCl]
(Piso− = [ArNC(But)NAr]−, Priso− = [ArNC(NPri2)NAr]−) has been investigated. Salt elimination
reactions have yielded the new monomeric complexes, [(Piso)Ge(NPri2)] and [(Piso)GeFeCp(CO)2],
whilst a ligand displacement reaction afforded the heterometallic species, [(Piso)Ge(Cl){W(CO)5}].
Chloride abstraction from [(Priso)GeCl] with GaCl3 has given the structurally characterised contact ion
pair, [(Priso)Ge][GaCl4]. In addition, the inconclusive outcome of a number of attempts to reduce the
germanium halide complexes are discussed.
(Nacnac−), which have been extensively used for the preparation
Introduction
of low oxidation state metal complexes.15
Amidinates and guanidinates have been widely used as ligands
The b-diketiminate complex of most relevance to this study
to form complexes with metals from across the periodic table.1
From group 14, the majority of the literature deals with tin(II)
amidinate complexes which have found use as, for example,
catalysts for the polymerisation of lactide2 and the cyclisation
of isocyanates.3 In contrast, very few studies of amidinate or
guanidinate complexes of Si(II),4 Ge(II)3,5,6 or Pb(II)7,8 have been
reported, and no complexes of the type, LGeX (L = amidinate or
guanidinate, X = halide), were known prior to our involvement
in the field. In a preliminary communication we described the
synthesis and structural characterisation of two such monomeric
complexes, [(Piso)GeCl] and [(Priso)GeCl],9 which incorporate
the bulky Piso− ([ArNC(But)NAr]−, Ar = C6H3Pri2-2,6) and
Priso− ([ArNC(NPri2)NAr]−) ligands. These complexes were suc-
cessfully reduced by treatment with potassium metal to give
the thermally stable dimeric germanium(I) amides, [{(Piso)Ge}2]
and [{(Priso)Ge}2], which can be considered as base stabilised
amido-germynes (cf. Power’s terphenyl substituted digermynes,
e.g. [{(C6H3Ar2-2,6)Ge}2]10). The exceptional stability of these
complexes derives from the kinetic protection provided by the
bulky ligands. In other work, we have employed Piso−, Priso−
and related ligands to prepare stable Ga(I),11 As(I),12 Mg(I)13
and lanthanide(II)14 complexes. It has become clear from these
studies that the stabilising properties of these ligands are similar to
those of sterically hindered b-diketiminates, e.g. [(ArNCMe)2CH]−
is [(Nacnac)GeCl]16 which has been used as a precursor for an
impressive array of Ge(II) and Ge(IV) complexes.17–19 Following on
from our preliminary study, we proposed to extend the range of
known LGeX complexes and to explore their further chemistry,
drawing comparisons with that of [(Nacnac)GeCl]. The results of
our efforts towards this goal are reported here.
Results and discussion
(i) Germanium(II) amidinates
Our initial investigations centred on the use of amidinates related
to Piso−, but with less bulky backbone substituents, to form
complexes of the type, LGeX. To this end Li[Fiso] (Fiso−
=
[ArNC(H)NAr]−) was reacted with GeCl2·dioxane in a 1 : 1
stoichiometry. However, this reaction led to a moderate yield of
[Ge(Fiso)2], 1, as the only identifiable product (Scheme 1). Presum-
ably, [(Fiso)GeCl] is initially formed and this reacts with a second
equivalent of Li[Fiso] more rapidly than the excess GeCl2·dioxane
can. It is of note that Gibson and co-workers have recently
reported that the related 1 : 1 reactions of SnCl2 with Li[Piso]
or Li[ArNC(Me)NAr] led to monomeric [(Piso)SnCl] and a 2 : 3
mixture of [{ArNC(Me)NAr}SnCl] and [Sn{ArNC(Me)NAr}2],
respectively.2 The outcomes of the germanium and tin halide
reactions indicate that bulky amidinates, e.g. Piso−, are required
to prevent the formation of bis(amidinate) complexes.
aSchool of Chemistry, PO Box 23, Monash University, VIC, 3800, Australia
The X-ray crystal structure of 1 was determined and its
molecular structure is depicted in Fig. 1. This shows it to be
isostructural with [Pb(Fiso)2].8 It is monomeric with a four-
coordinate germanium centre that has a heavily distorted saw-
horse coordination geometry and a stereochemically active lone
pair of electrons. As expected, the distances from the axial
nitrogens, N(2) and N(4), to Ge(1) are significantly longer than
the equatorial N(1)–Ge and N(2)–Ge separations. The geometry
bSchool of Chemistry, Main Building, Cardiff University, Cardiff, UK CF10
3AT
† Electronic supplementary information (ESI) available: ORTEP diagram
and metrical parameters for 5 and full crystallographic details for the co-
crystallised mixture of [(Priso)GeGa(I0.6/Cl0.4)(Giso)]. Crystallographic
data (excluding structure factors) for the structures of 1, 3–6, 8 and
[(Priso)GeGa(I0.6/Cl0.4)(Giso)]. CCDC reference numbers 675662–675668.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/b801168k
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without interconversion of the axial and equatorial N-sites on
the NMR timescale at ambient temperature. In contrast, the
room-temperature H and 13C{ H} NMR spectra of 1 display
broadened signals compatible with four chemically inequivalent
sets of methyl groups and two sets of inequivalent methine centres.
This suggests a fluxional process is occurring in solution, the speed
of which is approximately equal to the NMR timescale. Although
the low solubility of 1 in D8-toluene prevented the resolution
of its NMR spectra at lower temperatures, the fluxional process
is proposed to involve an exchange of the axial and equatorial
nitrogen sites. A similar exchange process has been previously
proposed for the less hindered germanium bis(amidinate) com-
plex, [Ge{PriNC(Me)NPri}2].5
1
1
As the germanium amidinate complex, [(Fiso)GeCl], proved
inaccessible in our hands, attention turned to the bulkier complex,
[(Piso)GeCl], as a precursor for further reactivity studies. The
utility of this compound towards salt elimination was tested
in its reactions with Li[NPri2] and Na[CpFe(CO)2]. These gave
the expected germanium(II) amide, 2, and the Ge–Fe bonded
complex, 3, in moderate isolated yields (Scheme 1). Complex
2 is comparable to the related amidinato germanium(II) amide,
e.g. [Ge{Me3SiNC(But)NSiMe3}{N(SiMe3)2}],3 and the tin com-
plexes, [(Piso)Sn(NR2)] (R = Me or SiMe3),2 the latter of which
have recently been shown to be effective as lactide polymerisation
catalysts. In addition, if comparisons are made with the chemistry
of [(Nacnac)GeCl], its treatment with Li[N(SiMe3)2] does not
lead to [(Nacnac)Ge{N(SiMe3)2}], but instead to deprotonation
of one Nacnac− methyl substituent.17 Moreover, there are no
known metal functionalised amidinato germanium complexes for
comparison with 3.
Scheme 1 Reagents and conditions: (i) Li[Fiso], diethyl ether, −LiCl;
(ii) LiNPri2, THF, −LiCl; (iii) Na[CpFe(CO)2], THF, −NaCl; (iv)
[W(CO)5(THF)], THF.
Given that the germanium lone pair of [(Nacnac)GeOH]18
has been shown to coordinate to metal fragments, e.g. Fe(CO)4
or CpMn(CO)2, it seemed that the metal functionalisation of
[(Piso)GeCl] could also be achieved by its coordination to related,
neutral metal carbonyl fragments. This proved to be the case in
its reaction with [W(CO)5(THF)] which gave the heterometallic
system, 4, in good yield (Scheme 1). In a similar fashion, oxidation
of [(Nacnac)GeCl] by treatment with elemental chalcogens is
=
known to give the monomeric complexes, [(Nacnac)Ge( E)Cl]
(E = S or Se).19 In contrast, the reactions of [(Piso)GeCl] with
elemental sulfur, selenium or tellerium, gave intractable mixtures
of products in our hands. In order to add control to the oxidation
of [(Piso)GeCl] with sulfur, the complex was treated with one
equivalent of propylene sulfide, a soluble source of the chalcogen.
However, again a mixture of products was obtained from this
reaction, the only one of which could be isolated (18% yield)
was the amidinium salt, [PisoH2][GeCl3] 5, which presumably
forms due to the presence of adventitious water in the reaction
mixture. Subsequently, compound 5 was intentionally synthesised
in moderate yield by treating GeCl2·dioxane with one equivalent
of [PisoH2]Cl.
Fig. 1 Molecular structure of 1 (25% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity). Selected bond lengths (A)
˚
and angles (◦): Ge(1)–N(3) 1.994(4), Ge(1)–N(1) 2.008(4), Ge(1)–N(4)
2.258(4), Ge(1)–N(2) 2.293(4), N(1)–C(1) 1.325(6), N(2)–C(1) 1.297(6),
N(3)–C(26) 1.326(6), N(4)–C(26 1.308(6), N(3)–Ge(1)–N(1) 102.78(17),
N(3)–Ge(1)–N(4) 62.29(16), N(1)–Ge(1)–N(4) 94.51(17), N(3)–Ge(1)–
N(2) 91.07(16), N(1)–Ge(1)–N(2) 61.76(17), N(4)–Ge(1)–N(2) 140.57(14),
N(2)–C(1)–N(1) 115.9(5), N(4)–C(26)–N(3) 114.1(5).
of the backbone amidinate NCN fragments show them to be
effectively delocalised. The structure of 1 is closely related
to that of [Sn{ArNC(Me)NAr}2]2 and [Ge{PriNC(Me)NPri}2].5
Interestingly, it differs from those of [Ge{CyNC(R)NCy}2] (R =
Me or But, Cy = cyclohexyl) which have three-coordinate Ge
centres ligated by one chelating, delocalised amidinate and one
monodentate, localised amidinate.6
The NMR spectroscopic data for 2–4 are as would be expected
for these complexes retaining their solid state structures in
1
solution. The 1H and 13C{ H} NMR spectra of each displays four
methyl and two methine signals arising from their aryl isopropyl
substituents. Similar spectral patterns have been observed for
[(Piso)ECl] (E = Ge9 or Sn2) and [(Piso)Sn(NR2)] (R = Me
The NMR spectral data for
1 differ from those of
[Sn{ArNC(Me)NAr}2]2 in that the latter are consistent with
or SiMe3 ) and originate from the tetrahedral geometry of the
2
the tin compound retaining its solid state structure in solution
germanium centres of the complexes, ensuring different chemical
2872 | Dalton Trans., 2008, 2871–2878
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environments on either side of the plane of the germanium
heterocycle.
Compounds 3–5 were crystallographically characterised and
the molecular structures of 3 and 4 are depicted in Figs. 2
and 3, respectively. As the [GeCl3]− anion has been structurally
characterised on a number of occasions20 and the structure of the
amidinium cation, [PisoH2]+, is similar to that of neutral PisoH,21
the molecular structure of 5 has been included in the ESI† and
will not be commented on here. There are two crystallographically
independent molecules in the asymmetric unit of 3 that have
no significant geometric differences and, therefore, the metric
parameters of only one will be discussed. The geometries of the
germanium heterocycles of the compounds are similar to each
other and to that of [(Piso)GeCl]. Both compounds possess heavily
distorted tetrahedral germanium centres, chelated by a delocalised
Piso− ligand. The Ge–M distances are in the known ranges22 (Fe–
˚
˚
˚
˚
Ge 2.240–2.496 A, 2.389 A mean; W–Ge 2.486–2.724 A, 2.574 A
mean), whilst the Ge–Cl distance in 4 is slightly longer than that
in [(Piso)GeCl] (2.174(2) A).
9
Fig. 3 Molecular structure of 4 (25% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity). Selected bond lengths (A)
˚
˚
and angles (◦): W(1)–Ge(1) 2.5564(6), Ge(1)–N(1) 1.961(3), Ge(1)–N(2)
1.978(3), Ge(1)–Cl(1) 2.2091(10), N(1)–C(1) 1.352(4), C(1)–N(2) 1.340(4),
N(1)–Ge(1)–N(2) 66.42(12), N(1)–Ge(1)–Cl(1) 100.64(9), N(2)–Ge(1)–
Cl(1) 95.93(9), N(1)–Ge(1)–W(1) 132.01(9), N(2)–Ge(1)–W(1) 138.78(8),
Cl(1)–Ge(1)–W(1) 111.86(3), N(2)–C(1)–N(1) 106.5(3).
extend the available range of guanidinato germanium halides.
To this end, two bulky guanidinate salts, Li[Giso] and
Li[Pipiso] (Giso− = [ArNC(NCy2)NAr]−; Pipiso− = [ArNC(cis-
2,6-Me2C5H8N)NAr]−) were reacted with GeCl2·dioxane in 1 : 1
stoichiometries. Both reactions yielded the desired products, 6 and
7 respectively, in good yields (Scheme 2). It is of note that the tin
analogues of these complexes have been recently reported.24
Fig. 2 Molecular structure of 3 (25% thermal ellipsoids are shown. Hy-
˚
drogen atoms are omitted for clarity). Selected bond lengths (A) and angles
(◦): Ge(1)–N(1) 2.042(4), Ge(1)–N(2) 2.043(4), Ge(1)–Fe(1) 2.4415(11),
Fe(1)–C(35) 1.750(6), Fe(1)–C(36) 1.756(6), N(1)–C(1) 1.341(6),
N(2)–C(1) 1.351(6); N(1)–Ge(1)–N(2) 64.19(15), N(1)–Ge(1)–Fe(1)
110.45(11), N(2)–Ge(1)–Fe(1) 111.61(12), C(35)–Fe(1)–C(36) 95.7(3),
N(1)–C(1)–N(2) 107.5(4).
(i) Germanium(II) guanidinates
Scheme 2 Reagents and conditions: (i) Li[Giso] or Li[Pipiso], THF, −LiCl;
The only guanidinato germanium(II) halide reported in the liter-
ature is [(Priso)GeCl] which we have shown to be readily reduced
to the dimeric germanium(I) species, [{(Priso)Ge}2].9 We have also
demonstrated that [(Priso)GeCl] can participate in a salt elimina-
tion reaction with the sterically demanding, anionic gallium(I)
heterocyclic complex, [K(tmeda)2][:Ga{ArNC(H)C(H)NAr}],
which yielded the monomeric germanium(II) gallyl complex,
[(Priso)GeGa{ArNC(H)C(H)NAr}].23 In order to extend guani-
dinato germanium(II) chemistry, it was seen as desirable to
(ii) GaCl3, toluene.
The NMR spectra of the complexes are similar to those of
[(Giso)SnCl] and [(Pipiso)SnCl],24 and like those of [(Priso)GeCl]9
exhibit four methyl and two methine signals arising from their
aryl isopropyl substituents. This pattern is consistent with the
solid state structure of 6 (Fig. 4) which was determined by
an X-ray crystallographic study. The molecule is monomeric
and possesses a heavily distorted pyramidal germanium centre
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In addition to reduction of guanidinato germanium chloride
complexes, we are interested in abstraction of chloride from them
to give cations of the type, [(guanidinate)Ge]+. If achievable, these
would be isoelectronic to the gallium(I) heterocycle, [(Giso)Ga:],
we reported in 2006.11 A comparison of the structural aspects of
the two complex types would be of significant interest. A similar
study has compared the [(Nacnac)Ge]+ cation with the monomeric
gallium(I) heterocycle, [(Nacnac)Ga:], with the conclusion that
there is partial p-delocalisation over the whole heterocycle of the
cation, which also has shorter, and apparently stronger, E–N bonds
than the neutral heterocycle.27
In an attempt to access the target heterocycles, toluene so-
lutions of [(Giso)GeCl] or [(Priso)GeCl], were treated with the
chloride abstraction agent, Na[B{C6H3(CF3)2-3,5}4]. No reaction
occurred in either case, probably due to the low solubility of
Na[B{C6H3(CF3)2-3,5}4] in toluene. Attention shifted to the use
of toluene soluble GaCl3 as a chloride abstraction agent. When
toluene solutions of both germylene precursors were treated with
GaCl3, colourless precipitates formed, though only that from the
[(Priso)GeCl] reaction had sufficient solubility to be recrystallised
in a pure form. Subsequent analyses proved this to be the contact
ion pair, 8 (Scheme 2), which was formed in high yield.
Fig. 4 Molecular structure of 6 (25% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity). Selected bond lengths (A)
˚
and angles (◦): Ge(1)–N(1) 1.993(3), Ge(1)–N(2) 2.003(3), Ge(1)–Cl(1)
2.245(2), N(1)–C(1) 1.363(5), C(1)–N(2) 1.342(5), C(1)–N(3) 1.360(5);
N(1)–Ge(1)–N(2) 65.76(13), N(1)–Ge(1)–Cl(1) 102.01(13), N(2)–Ge(1)–
Cl(1) 99.84(12), N(2)–C(1)–N(3) 127.1(3), N(2)–C(1)–N(1) 106.6(3),
N(3)–C(1)–N(1) 126.2(4).
1
The 1H and 13C{ H} NMR spectra (D8-THF) of 8 are not
as symmetrical as would be expected if the [(Priso)Ge]+ was
1
uncoordinated in solution. For example, the H NMR spectrum
exhibits four broad aryl isopropyl methyl signals and two aryl
isopropyl methine resonances. Consistent with this is the presence
ꢀ
angles = 267.6◦, cf. 263.5◦ for [(Priso)GeCl]) that is coordi-
of six aryl carbon resonances in the 13C{ H} NMR spectrum
1
(
nated by a delocalised guanidinate ligand. The Ge–Cl distance for
the compound is close to those seen for [(Priso)GeCl] (2.252(4)
of the compound. It is possible that the lower than expected
symmetry of these spectra is due to either a persistent cation-
anion interaction in solution, or the germanium centre of an ion
separated [(Priso)Ge]+ cation being coordinated by one molecule
of THF, leading to a pyramidal geometry at that centre.
˚
A) but both are significantly greater than that for the amidinate
˚
complex, [(Piso)GeCl] (2.174(2) A). A possible explanation for this
observation arises from the fact that guanidinate ligands are more
N-electron rich than amidinates. This would lead to more electron
density being placed on the Ge centres of 6 and [(Priso)GeCl]
relative to that of [(Piso)GeCl], thus weakening the Ge–Cl bonds
of the guanidinate complexes. In contrast to 6, it is of note that the
structure of the lead analogue of this compound, [{(Giso)Pb(l-
Cl)}2], has been recently reported to be a chloride bridged dimer.8
Preliminary efforts have been made to study the further chem-
istry of [(Giso)GeCl] and [(Pipiso)GeCl]. Their reduction over
potassium mirrors in toluene led to deep green solutions in both
cases. Although no crystalline or pure materials could be isolated
from these reactions, the colours of the reaction mixtures are sim-
ilar to that of toluene solutions of [{(Priso)Ge}2].9 This suggests
that related Ge(I) species were formed in the reductions, though
no other evidence for this proposition was forthcoming. The
reduction of [(Giso)GeCl] with [AlH3(NMe3)] was also attempted,
with the expectation that the corresponding terminal hydride
complex, [(Giso)GeH], would be formed. This seemed reasonable
as [(Nacnac)GeH] has recently been reported to be formed in
the reaction of [(Nacnac)GeCl] with [AlH3(NMe3)].25 However,
the reaction proceeded via a transmetallation process to give a
co-crystallised guanidinate aluminium hydride/halide mixture,
[(Giso)AlHxCl2−x], as determined by an X-ray crystallographic
study. The outcome of the germanium in this reaction is not
known. A number of other reductions of [(L)GeCl] (L = Priso−,
Giso− or Pipiso−) with various reagents were attempted with
largely inconclusive results.26
The molecular structure of 8 (Fig. 5) shows it to exist as a
˚
contact ion pair with a Ge · · · Cl interaction that is ca. 0.28 A
longer than the Ge–Cl distance in [(Priso)GeCl], but within the
known range for Ge–Cl bonds.22 This interaction should therefore
be considered as relatively strong, as additionally evidenced by the
˚
fact that the bridging Ga–Cl bond is ca. 0.1 A longer than the three
terminal Ga–Cl bonds. The C3N ligand backbone of the cation of 8
appears to be largely delocalised, as is the case with [(Priso)GeCl].
In addition, its Ge–N bond lengths and N–Ge–N angle are not
˚
significantly different to those of [(Priso)GeCl] (1.954 A (mean)
and 67.22(12)◦ A, respectively). They are, however, markedly
˚
shorter and more obtuse, respectively, than the Ga–N distances
and N–Ga–N angle of the isoelectron◦ic gallium(I) heterocycle,
[(Giso)Ga:] (2.091 A mean and 63.77(7) ).11 These differences are
˚
likely to be predominantly a result of the smaller radius of Ge
28
˚
˚
(1.22 A) than Ga (1.25 A). The probable greater positive charge
on the Ge centre in 8 than the Ga centre in [(Giso)Ga:] may
also lead to a more pronounced E–N interaction in the former.
Similar arguments have been put forward to explain the structural
differences between [(Nacnac)Ge]+ and [(Nacnac)Ga:].27
Conclusion
In summary, two new heteroleptic germylenes, [(Giso)GeCl]
and [(Pipiso)GeCl], have been prepared and one shown to be
monomeric by an X-ray crystallographic study. A preliminary
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[W(CO)5(THF)]31 were synthesised by variations of literature
procedures. [PisoH2]Cl was prepared by treating PisoH with 3M
HCl followed by rigorous drying of the salt in vacuo. All other
reagents were used as received.
Preparation of [Ge(Fiso)2] 1. BunLi (1.10 cm3 of a 1.6 M
solution in hexanes, 1.76 mmol) was added to a solution of FisoH
(0.62 g, 1.70 mmol) in diethyl ether (20 cm3) at 20 ◦C and the solu-
tion stirred overnight. This was then added at −80 ◦C to a slurry
of GeCl2·dioxane (0.42 g, 1.81 mmol) in diethyl ether (20 cm3) over
5 min. The resultant mixture was warmed to room temperature
over 4 h. Volatiles were removed in vacuo and the residue extracted
into toluene (30 cm3) and cooled to 4 ◦C yielding 1 as colourless
crystals (0.29 g, 41%). Mp 255–257 ◦C (280 ◦C rapid decomp.). 1H
NMR (400 MHz, C6D6, 298 K): d 1.10–1.40 (overlapping m, 48 H,
CH(CH3)2), 3.40–3.70 (overlapping m, 8 H, CH(CH3)2), 7.00–7.38
(m, 12 H, Ar–H), 7.60 (s, 2 H, CH); 13C NMR (100.6 MHz, C6D6,
298 K): d 23.1, 23.8, 24.2, 24.8 (CH(CH3)2), 28.5, 28.9 (CH(CH3)2),
123.7, 123.9, 127.7, 137.2, 141.6, 144.0 (Ar–C), 160.1 (NCN); MS
(APCI) m/z (%): 365 (FisoH2 , 100); IR m/cm−1 (Nujol): 1668 (m),
+
1634 (m), 1593 (m), 1558 (m), 1261 (s), 1186 (m), 1098 (s), 1057
(m), 956 (m), 769 (m), 754 (m).
Fig. 5 Molecular structure of 8 (25% thermal ellipsoids are shown.
Hydrogen atoms are omitted for clarity). Selected bond lengths (A) and
˚
angles (◦): Ge(1)–N(1) 1.9477(18), Ge(1)–N(2) 1.9552(18), Ge(1)–Cl(1)
2.5333(9), Ga(1)–Cl(4) 2.1406(8), Ga(1)–Cl(3) 2.1451(11), Ga(1)–Cl(2)
2.1590(8), Ga(1)–Cl(1) 2.2613(8), N(1)–C(1) 1.359(3), C(1)–N(3) 1.344(3),
C(1)–N(2) 1.377(3); N(1)–Ge(1)–N(2) 67.47(7), N(1)–Ge(1)–Cl(1)
95.20(6), N(2)–Ge(1)–Cl(1) 92.55(5), Ga(1)–Cl(1)–Ge(1) 105.80(3),
N(3)–C(1)–N(1) 128.52(19), N(3)–C(1)–N(2) 126.7(2), N(1)–C(1)–N(2)
104.76(18).
Preparation of [(Piso)GeNPri2] 2. To a solution of [(Piso)GeCl]
(0.25 g, 0.47 mmol) in THF (30 cm3) at −78 ◦C was added
a solution of Li[NPri2] (0.05 g, 0.47 mmol) in THF (10 cm3)
over 5 min. The resultant colourless solution was warmed to
room temperature and stirred overnight. Volatiles were removed in
vacuo and the residue extracted with hexane (15 cm3). Filtration,
concentration and cooling to −50 ◦C overnight yielded colourless
crystals of 2 (0.12 g, 42%). Mp 138–140 ◦C; 1H NMR (400 MHz,
study of the reactivity of these and two related complexes,
[(Piso)GeCl] and [(Priso)GeCl], has been carried out. Salt
elimination reactions have yielded the new monomeric com-
plexes, [(Piso)Ge(NPri2)] and [(Piso)GeFeCp(CO)2]. A neutral
ligand displacement reaction afforded the heterometallic species,
[(Piso)Ge(Cl){W(CO)5}], whilst a chloride abstraction reaction
gave the contact ion pair, [(Priso)Ge][GaCl4], the cation of which
is isoelectronic to the previously reported gallium(I) heterocycle,
[(Giso)Ga:]. Studies continue in our laboratory on the use of bulky
guanidinates to prepare stable complexes containing low oxidation
state metal centres from across the periodic table.
3
C6D6, 298 K): d 0.68 (s, 9 H, But), 0.85 (d, JHH = 6.7 Hz, 6 H,
3
CH(CH3)2), 0.94 (d, JHH = 6.7 Hz, 6 H, CH(CH3)2), 0.98 (d,
3
3JHH = 6.7 Hz, 6 H, CH(CH3)2), 1.05 (d, JHH = 6.7 Hz, 6 H,
3
CH(CH3)2), 1.10 (d, JHH = 6.8 Hz, 12 H, NCH(CH3)2), 3.25
(sept, 3JHH = 6.8 Hz, 2 H, NCH(CH3)2), 3.40 (sept, 3JHH = 6.7 Hz,
3
2 H, CH(CH3)2), 3.68 (sept, JHH = 6.7 Hz, 2H, CH(CH3)2),
6.75–6.86 (m, 6 H, Ar–H); 13C NMR (75 MHz, C6D6, 298
K): d 21.4 (NCH(CH3)2), 23.4 (CH(CH3)2), 24.1 (CH(CH3)2),
27.4 (CH(CH3)2), 28.2 (CH(CH3)2), 28.6 (CH(CH3)2), 28.7
(CH(CH3)2), 29.1 (NCH(CH3)2), 29.9 (C(CH3)3), 42.1 (C(CH3)3),
123.0, 124.0, 124.8, 138.3, 141.0, 142.0 (Ar–C), 166.5 (NCN); IR
m/cm−1 (Nujol): 1652 (s), 1616 (s), 1585 (s), 1321 (s), 1258 (s), 1042
(m), 933 (m); MS (APCI) m/z (%): 593 (M+, 100), 493 (M+ − NPri2,
90), 421 (PisoH+, 100). Elemental analysis: C35H57N3Ge requires:
C 70.95, H 9.70, N 7.09. Found: C 70.69, H 9.41, N 6.86%.
Experimental
General considerations
All manipulations were carried out using standard Schlenk and
glove box techniques under atmospheres of high purity argon or
dinitrogen. Hexane, toluene and THF were distilled over molten
potassium metal, diethyl ether was distilled over Na/K alloy,
whilst dichloromethane was distilled over CaH2. Melting points
were determined in sealed glass capillaries under argon and are
uncorrected. Mass spectra were recorded at the EPSRC National
Mass Spectrometric Service at Swansea University. Microanalyses
were obtained from Medac Ltd. IR spectra were recorded using
a Nicolet 510 FT-IR spectrometer as Nujol mulls between NaCl
plates. H and 13C{ H} NMR spectra were recorded on either
Bruker DXP400 or Jeol Eclipse 300 spectrometers and were refer-
enced to the resonances of the solvent used. FisoH,29 Li[Giso],11
Li[Pipiso],24 [(Piso)GeCl],9 [(Priso)GeCl],9 GeCl2·dioxane30 and
Preparation of [(Piso)GeFeCp(CO)2] 3. To a solution of
[(Piso)GeCl] (0.30 g, 0.57 mmol) in THF (15 cm3) was added a
solution of Na[CpFe(CO)2] (0.11 g, 0.57 mmol) in THF (15 cm3) at
−78 ◦C over 5 min. The resultant red solution was warmed to 20 ◦C
and stirred overnight. Volatiles were removed in vacuo and the
residue extracted with hexane (10 cm3). Filtration, concentration
and cooling to −30 ◦C overnight yielded red crystals of 3
(0.21 g, 56%). Mp 120–150 ◦C; 1H NMR (400 MHz, C6D6,
3
298 K): d 0.82 (s, 9H, But), 1.15 (d, JHH = 6.8 Hz, 6 H,
1
1
3
CH(CH3)2), 1.20 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.21 (d,
3
3JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.25 (d, JHH = 6.8 Hz, 6
3
H, CH(CH3)2), 3.49 (sept, JHH = 6.8 Hz, 2 H, CH(CH3)2),
3
3.90 (s, 5H, CpH), 3.97 (sept, JHH = 6.8 Hz, 2 H, CH(CH3)2),
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6.86–6.92 (m, 6 H, Ar-H); 13C NMR (75 MHz, C6D6, 298 K):
d 22.9 (CH(CH3)2), 23.4 (CH(CH3)2), 27.4 (CH(CH3)2), 28.0
(CH(CH3)2), 28.7 (CH(CH3)2), 29.2 (CH(CH3)2), 29.4 (C(CH3)3),
41.9 (C(CH3)3), 84.5 (C5H5), 123.5, 124.1, 126.1, 140.5, 144.1,
145.4 (Ar–C), 165.0 (NCN), 216.5 (CO); IR m/cm−1 (Nujol): 1964
(CO str, s), 1921 (CO str, s), 1315 (s), 1253 (s), 969 (m); MS (EI) m/z
(%): 666 (M+, 6), 493 (PisoGe+, 42), 421 (PisoH+, 100); accurate
MS (EI) calc. for C36H48N2GeFeO2: 666.2320, found 666.2328.
Elemental analysis: C36H48N2GeFeO2 requires: C 64.61, H 7.23, N
4.18. Found: C 64.36, H 7.15, N 4.33%.
stirred for a further 2 h. All volatiles were removed in vacuo
and the residue extracted into hexane (40 cm3). The extract was
◦
concentrated to ca. 12 cm3 and slowly cooled to −30 C to give
colourless crystals of 6 (1.07 g, 75%). Mp 198–200 ◦C; 1H NMR
(400 MHz, 296 K, C6D6): d 0.73–0.90 (m, 6 H, CH2), 1.21–1.90
3
(m, 14 H, CH2), 1.38 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.45
(d, 3JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.53 (d, 3JHH = 6.8 Hz, 6 H,
3
CH(CH3)2), 1.66 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 3.70 (mc,
3
2 H, NCH), 3.72 (sept, JHH = 6.8 Hz, 2 H, CH(CH3)2), 4.17
(sept, 3JHH = 6.8 Hz, 2 H, CH(CH3)2), 7.13–7.29 (m, 6 H, Ar–H);
1
13C{ H} NMR (100.6 MHz, C6D6, 298 K): d 21.3 (CH(CH3)2),
Preparation of [(Piso)Ge(Cl){W(CO)5}] 4. To a solution of
[(Piso)GeCl] (0.30 g, 0.57 mmol) in THF (10 cm3) was added a
solution of [W(CO)5(THF)] (0.23 g, 0.57 mmol) in THF (40 cm3)
at −78 ◦C over 5 min. The resultant colourless solution was
warmed to room temperature and stirred overnight. Volatiles were
removed in vacuo and the residue extracted with hexane (15 cm3).
Filtration, concentration and cooling to −30 ◦C overnight yielded
colourless crystals of 4 (0.27 g, 56%). Mp 138–142 ◦C; 1H
NMR (400 MHz, C6D6, 298 K): d 0.48 (s, 9 H, But), 0.96 (d,
22.1 (CH2), 24.0 (CH2), 25.5 (CH(CH3)2), 27.2 (CH(CH3)2), 27.4
(CH(CH3)2), 27.6 (CH(CH3)2), 27.8 (CH(CH3)2), 33.1 (CH2), 57.1
(NCH), 122.3, 123.4, 125.1, 137.3, 143.3, 145.9 (Ar–C), 161.2
(backbone CN3); IR m/cm−1 (Nujol): 1612 (s), 1582 (m), 1162 (m),
1094 (m), 1018 (m), 894 (m), 797 (m); MS (EI 70 eV), m/z (%):
651.3 (M+, 3), 616.4 (M+ − Cl, 2), 544 (GisoH+, 33); accurate MS
(EI) calc. for C37H56ClGeN3: 651.3369, found: 651.3374.
Preparation of [(Pipiso)GeCl] 7. A solution of Li[Pipiso]
(1.00 g, 2.08 mmol) in THF (20 cm3) was added to a solution
of GeCl2·dioxane (0.51 g, 2.24 mmol) in THF (10 cm3) at
−80 ◦C. The resultant mixture was warmed to room temperature
over 4 h and stirred for a further 2 h. All volatiles were removed
in vacuo and the residue extracted into hexane (40 cm3). The
extract was concentrated to ca. 12 cm3 and slowly cooled to
−30 ◦C to give colourless crystals of 7 (0.93 g, 77%). Mp 195–
197 ◦C (decomp.); 1H NMR (400 MHz, C6D6, 298 K): d 0.83 (d,
3JHH = 7.1 Hz, 6 H, NCHCH3), 0.90–1.71 (m, 6 H, CH2), 1.37
3
3JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.01 (d, JHH = 6.8 Hz, 6 H,
3
CH(CH3)2), 1.09 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.23 (d,
3
3JHH = 6.8 Hz, 6 H, CH(CH3)2), 3.35 (sept, JHH = 6.8 Hz,
3
2 H, CH(CH3)2), 3.82 (sept, JHH = 6.8 Hz, 2 H, CH(CH3)2),
6.72–6.80 (m, 6 H, Ar–H); 13C NMR (75 MHz, C6D6, 298 K):
d 22.2 (CH(CH3)2), 23.6 (CH(CH3)2), 27.7 (CH(CH3)2), 28.4
(CH(CH3)2), 28.9 (CH(CH3)2), 29.1 (CH(CH3)2), 29.4 (C(CH3)3),
41.9 (C(CH3)3), 124.1, 124.7, 125.6, 135.8, 146.3, 146.8 (Ar–C),
185.1 (NCN), 196.0 (CO); IR m/cm−1 (Nujol): 2073 (CO str, s),
1978 (CO str, s), 1948 (CO str, s), 1318 (s), 1260 (s), 1208 (m), 1185
(s), 933 (m); MS (APCI) m/z (%): 815 (M+ − Cl, 25), 421 (PisoH+,
100). Elemental analysis: C34H43N2GeClO5 requires: C 47.95, H
5.09, N 3.29. Found: C 46.96, H 5.14, N 3.19%.
3
3
(d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.40 (d, JHH = 6.8 Hz,
3
6 H, CH(CH3)2), 1.44 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2),
3
3
1.62 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 3.62 (sept, JHH
=
6.8 Hz, 2 H, CH(CH3)2), 3.91 (mc, 2 H, NCHCH3), 4.22 (sept,
3JHH = 6.8 Hz, 2 H, CH(CH3)2), 7.11–7.28 (m, 6 H, Ar–H);
Preparation of [PisoH2][GeCl3] 5. To a solution of [PisoH2]Cl
(0.25 g, 0.55 mmol) in THF (20 cm3) was added a solution of
GeCl2·dioxane (0.13 g, 0.55 mmol) in THF (20 cm3) at −78 ◦C
over 5 min. The resultant pale yellow solution was warmed to
room temperature and stirred overnight. Volatiles were removed
in vacuo and the residue extracted with dichloromethane (5 cm3).
Filtration and layering with hexane yielded pale yellow crystals of
1
13C{ H} NMR (100.6 MHz, C6D6, 298 K): d 11.9 (CH2), 19.8
(CH3), 21.7 (CH(CH3)2), 22.3 (CH(CH3)2), 26.6 (CH(CH3)2), 26.8
(CH(CH3)2), 27.2 (CH(CH3)2), 27.6 (CH(CH3)2), 28.2 (CH2), 46.3
(NCHCH3), 122.3, 123.5, 125.4, 136.9, 143.7, 146.1 (Ar–C), 160.2
(backbone CN3); IR m/cm−1 (Nujol): 1613 (m), 1577 (m), 1116
(m), 1080 (m), 1054 (m), 801 (s), 759 (s), 666 (m); MS (EI 70 eV),
m/z (%): 583.1 (M+, 7), 548.2 (M+ − Cl, 6), 540.1 (M+ − Pri, 7),
475.3 (PipisoH+, 5), 432.3 (PipisoH+ − Pri, 100); Accurate MS
(EI) calc. for C32H48ClN3Ge: 583.2743, found: 583.2748.
◦
1
5 (0.15 g, 46%). Mp 194–196 C; H NMR (400 MHz, C6D6,
3
298 K): d 0.99 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.30 (d,
3
3JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.31 (d, JHH = 6.8 Hz, 6
3
H, CH(CH3)2), 1.33 (d, JHH = 6.8 Hz, 6 H, CH(CH3)2), 1.44
Preparation of [(Priso)Ge][GaCl4] 8. A solution of GaCl3
(0.11 g, 0.61 mmol) in toluene (6 cm3) was added to a soluti◦on
of [(Priso)GeCl] (0.35 g, 0.61 mmol) in toluene (15 cm3) at −50 C
over 5 min. A white crystalline precipitate immediately formed.
The resultant suspension was warmed to room temperature, stirred
for 2 h and the colourless product was filtered off. X-Ray quality
crystals of 8 were obtained by cooling a saturated toluene solution
of the compound to 4 ◦C (0.40 g, 88%). Mp ca. 230 ◦C (decomp.);
1H NMR (400 MHz, THF-d8, 298 K): d 1.06 (d, 3JHH = 6.8 Hz, 12
H, NCH(CH3)2), 1.35 (2 x overlapping v br d, 12 H, ArCH(CH3)2),
3
(s, 9 H, But), 2.86 (2 × overlapping sept, JHH = 6.8 Hz, 4
H, CH(CH3)2), 5.20 (s, 1 H, CNH), 7.08–7.52 (m, 6 H, Ar–
H), 9.60 (s, 1 H, CNH); 13C NMR (75 MHz, C6D6, 298 K):
d 22.2 (CH(CH3)2), 22.5 (CH(CH3)2), 25.8 (CH(CH3)2), 26.1
(CH(CH3)2), 29.1 (CH(CH3)2), 29.6 (CH(CH3)2), 29.8 (C(CH3)3),
40.1 (C(CH3)3), 124.7, 125.6, 125.8, 129.6, 131.3, 132.3, 145.6,
146.7 (Ar–C), 175.2 (NCN); IR m/cm−1 (Nujol): 3265 (br, N–H
str), 1260 (s), 1095 (m), 802 (m); MS (APCI) m/z (%): 421 (PisoH+,
100). Elemental analysis: C29H45Cl3GeN2 requires: C 57.99, H 7.55,
N 4.66. Found: C 57.68, H 7.38, N 4.48%.
1.42 (br d, 3JHH = 6.8 Hz, 6 H, ArCH(CH3)2), 1.48 (br d, 3JHH
=
3
Preparation of [(Giso)GeCl] 6. A solution of Li[Giso] (1.20 g,
2.18 mmol) in THF (20 cm3) was added to a solu◦tion of
GeCl2·dioxane (0.54 g, 2.34 mmol) in THF (10 cm3) at −80 C. The
resultant mixture was warmed to room temperature over 4 h and
6.8 Hz, 6 H, ArCH(CH3)2), 3.59 (br sept, JHH = 6.8 Hz, 2
3
H, CH(CH3)2), 3.87 (br sept, JHH = 6.8 Hz, 2 H, CH(CH3)2),
3
4.05 (sept, JHH = 6.8 Hz, 2 H, NCH(CH3)2), 7.19–7.31 (m,
1
6 H, Ar–H); 13C{ H} NMR (100.6 MHz, THF-d8, 298 K): d
2876 | Dalton Trans., 2008, 2871–2878
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Table 1 Crystal data for compounds 1, 3–6 and 8
Compound
1
3
4
5
6
8
Empirical formula
Mr
T/K
C50H70GeN4
799.69
150(2)
C36H48FeGeN2O2 C34H43ClGeN2O5W C29H45Cl3GeN2 C37H56ClGeN3 C31H48Cl4GaGeN3
669.20
851.59
150(2)
600.61
150(2)
650.89
150(2)
746.83
150(2)
150(2)
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/c
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/c
Monoclinic
P21/c
˚
a/A
10.697(2)
15.758(3)
27.692(6)
91.22(3)
4666.7(16)
4
1.138
0.692
1720
28378
22.080(4)
16.626(5)
19.551(5)
109.60(1)
6761(3)
8
1.315
1.351
2816
48937
10.592(2)
16.684(3)
21.013(4)
101.67(3)
3636.6(13)
4
1.555
4.100
1696
26171
10.665(2)
18.049(4)
17.156(3)
102.93(3)
3218.7(11)
4
1.239
1.220
1264
18619
10.586(2)
18.950(4)
18.311(4)
103.50(3)
3571.9(11)
4
1.210
0.961
1392
34978
16.025(3)
12.550(3)
19.558(4)
110.87(3)
3675.4(13)
4
1.350
1.865
1544
15624
˚
b/A
˚
c/A
b/◦
3
˚
V/A
Z
Dc/Mg m−3
l(Mo-Ka)/mm−1
F(000)
No. reflections collected
No. independent reflns (Rint
Final R1 (I > 2r(I)) and
wR2 indices (all data)
)
8212 (0.1827)
13741 (0.0576)
7377 (0.0613)
6527 (0.0900)
6257 (0.0895)
R1 = 0.0724
8003 (0.0311)
R1 = 0.0353
R1 = 0.0840 wR2 = R1 = 0.0675
R1 = 0.0335 wR2 = R1 = 0.0572
0.1501
wR2 = 0.01418
0.0788
wR2 = 0.1294
wR2 = 0.1621 wR2 = 0.0746
21.2 (NCH(CH3)2), 21.8 (ArCH(CH3)2), 25.2 (ArCH(CH3)2), 26.0
(ArCH(CH3)2), 26.4 (ArCH(CH3)2), 26.7 (ArCH(CH3)2), 47.3
(NCH(CH3)2), 122.0, 122.8, 124.6, 136.4, 143.0, 145.2 (Ar–C),
161.0 (backbone CN3), N.B. one ArCH(CH3)2 resonance obscured
by solvent resonance; IR m/cm−1 (Nujol): 1603 (s), 1538 (m), 1261
(m), 1170 (m), 1105 (m), 805 (m), 759 (m); MS (EI), m/z (%): 420.4
(PrisoH+, 100).
3 S. R. Foley, Y. Zhou, G. P. A. Yap and D. S. Richeson, Inorg. Chem.,
2000, 39, 924.
4 (a) C.-W. So, H. W. Roesky, P. M. Gurubasavaraj, R. B. Oswald, M. T.
Gamer, P. G. Jones and S. Blaurock, J. Am. Chem. Soc., 2007, 129,
12049; (b) C.-W. So, H. W. Roesky, J. Magull and R. B. Oswald, Angew.
Chem., Int. Ed., 2006, 45, 3948.
5 H. H. Karsch, P. A. Schlu¨ter and M. Reisky, Eur. J. Inorg. Chem., 1998,
433.
6 S. R. Foley, C. Bensimon and D. R. Richeson, J. Am. Chem. Soc., 1997,
119, 10359.
7 U. Kilimann, M. Noltemeyer and F. T. Edelmann, J. Organomet. Chem.,
1993, 443, 35.
X-Ray crystallography
8 A. Stasch, C. M. Forsyth, C. Jones and P. C. Junk, New J. Chem.,
DOI: 10.1039/b718537e.
9 S. P. Green, C. Jones, P. C. Junk, K.-A. Lippert and A. Stasch, Chem.
Commun., 2006, 3978.
10 E. Rivard and P. P. Power, Inorg. Chem., 2007, 46, 10047, and references
therein.
Crystals of 1, 3–6 and 8 suitable for X-ray structural determination
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)32 using all unique data. Hydrogen atoms
have been included in calculated positions (riding model) for all
structures. Crystal data, details of data collections and refinement
are given in Table 1.
11 C. Jones, P. C. Junk, J. A. Platts and A. Stasch, J. Am. Chem. Soc., 2006,
128, 2206.
12 S. P. Green, C. Jones, G. Jin and A. Stasch, Inorg. Chem., 2007, 46,
8.
13 S. P. Green, C. Jones and A. Stasch, Science, 2007, 318, 1754.
14 D. Heitmann, C. Jones, P. C. Junk, K.-A. Lippert and A. Stasch, Dalton
Trans., 2007, 187.
15 L. Bourget-Merle, M. F. Lappert and J. R. Severn, Chem. Rev., 2002,
102, 3031.
CCDC reference numbers 675662–675668.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b801168k
16 Y. Ding, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt and P. P. Power,
Organometallics, 2001, 20, 1190.
17 M. Driess, S. Yao, M. Brym and C. von Wu¨llen, Angew. Chem., Int.
Ed., 2006, 45, 4349.
Acknowledgements
18 L. W. Pineda, V. Jancik, J. F. Colunga-Valladares, H. W. Roesky, A.
Hofmeister and J. Magull, Organometallics, 2006, 25, 2381.
19 Y. Ding, Q. Ma, H. W. Roesky, I. Uson, M. Noltemeyer and H.-G.
Schmidt, Dalton Trans., 2003, 1094.
20 See for exampleL. Apostolico, M. F. Mahon, K. C. Molloy, R. Binions,
C. S. Blackman, C. J. Carmalt and I. P. Parkin, Dalton Trans., 2004,
470.
We thank the Australian Research Council (fellowships for C. J.
and A. S.) and the EPSRC (partial studentship for R. P. R.). The
EPSRC Mass Spectrometry Service at Swansea University is also
thanked.
21 A. Xia, H. M. El-Kaderi, M. J. Heeg and C. H. Winter,
J. Organomet.Chem., 2003, 682, 224.
22 As determined from a survey of the Cambridge Crystallographic
Database, January, 2008.
References
1 (a) For general references on the coordination chemistry of amidinate
and guanidinate ligands, see: J. Barker and M. Kilner, Coord. Chem.
Rev., 1994, 133, 219; (b) F. T. Edelmann, Coord. Chem. Rev., 1994, 137,
403; (c) P. J. Bailey and S. Price, Coord. Chem. Revs., 2001, 214, 91, and
references therein.
2 N. Nimitsiriwar, V. C. Gibson, E. L. Marshall, A. J. P. White, S. H. Dale
and M. R. J. Elsegood, Dalton Trans., 2007, 4464.
23 S. P. Green, C. Jones, K.-A. Lippert, D. P. Mills and A. Stasch, Inorg.
Chem., 2006, 45, 7242.
24 M. Brym, M. D. Francis, G. Jin, C. Jones, D. P. Mills and A. Stasch,
Organometallics, 2006, 25, 4799.
25 L. W. Pineda, V. Jancik, K. Starke, R. B. Oswald and H. W. Roesky,
Angew. Chem., Int. Ed., 2006, 45, 2602.
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26 It is of note that the attempted reduction of a co-crystallised mixture,
[(Priso)GeCl0.4/I0.6], with the gallium(I) heterocycle, [(Giso)Ga:],11 led
instead to an oxidative insertion reaction and the formation of the
germanium gallyl complex mixture, [(Priso)GeGa(I0.6/Cl0.4)(Giso)].
Details of the crystallographic characterisation of this mixture are
included in the ESI†.
28 A. F. Wells, Structural Inorganic Chemistry, Clarendon, Oxford, 5th
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