Synthesis, characterisation and structural studies of amidinate and guanidinate alkaline earth–transition metal bonded complexes

Article abstract of DOI:10.1016/j.poly.2016.02.028

Reaction of magnesium amidinate complexes of the form [{MesC(NR)₂}MgBr(OEt₂)]₂(R?=?ⁱPr, Dipp, Mes) with the potassium salts of transition metal anions K[CpFe(CO)₂] (K[Fp]) and K[Co(CO)₃(PCy₃)](THF)₂gave the complexes {MesC(NR)₂}MgFp(THF) and {MesC(NR)₂}Mg{Co(CO)₃(PCy₃)}(THF). Single crystal X-ray diffraction studies of {MesC(NR)₂}Mg{Co(CO)₃(PCy₃)}(THF) for R?=?ⁱPr and Dipp confirm these to have Mg–Co bonds in the solid state. Reaction of the structurally similar magnesium guanidinate complex {Me₂NC(NDipp)₂}MgI(OEt₂) with the aforementioned transition metal anions or K[Co(CO)₃(PPh₃)](THF) gave the series of complexes [{Me₂NC(NDipp)₂}MgFp]₂, {Me₂NC(NDipp)₂}Mg{Co(CO)₃(PCy₃)}(OEt₂) and {Me₂NC(NDipp)₂}Mg{Co(CO)₃(PPh₃)}(OEt₂). Structural authentication by X-ray crystallography showed [{Me₂NC(NDipp)₂}MgFp]₂to be a very rare example of a base-free alkaline earth–transition bonded complex, having two Mg–Fe bonds. IR and diffusion NMR spectroscopy was carried out to gain further insight into the solid state and solution phase structures.

Full text of DOI:10.1016/j.poly.2016.02.028

Polyhedron xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterisation and structural studies of amidinate and
guanidinate alkaline earth–transition metal bonded complexes
⇑
⇑
Ross Green, Alicia C. Walker, Matthew P. Blake , Philip Mountford
Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
a r t i c l e i n f o
a b s t r a c t
Reaction of magnesium amidinate complexes of the form [{MesC(NR)2}MgBr(OEt2)]2 (R = iPr, Dipp, Mes)
with the potassium salts of transition metal anions K[CpFe(CO)2] (K[Fp]) and K[Co(CO)3(PCy3)](THF)2
gave the complexes {MesC(NR)2}MgFp(THF) and {MesC(NR)2}Mg{Co(CO)3(PCy3)}(THF). Single crystal
X-ray diffraction studies of {MesC(NR)2}Mg{Co(CO)3(PCy3)}(THF) for R = iPr and Dipp confirm these to
have Mg–Co bonds in the solid state. Reaction of the structurally similar magnesium guanidinate com-
plex {Me2NC(NDipp)2}MgI(OEt2) with the aforementioned transition metal anions or K[Co(CO)3(PPh3)]
(THF) gave the series of complexes [{Me2NC(NDipp)2}MgFp]2, {Me2NC(NDipp)2}Mg{Co(CO)3(PCy3)}
(OEt2) and {Me2NC(NDipp)2}Mg{Co(CO)3(PPh3)}(OEt2). Structural authentication by X-ray crystallogra-
phy showed [{Me2NC(NDipp)2}MgFp]2 to be a very rare example of a base-free alkaline earth–transition
bonded complex, having two Mg–Fe bonds. IR and diffusion NMR spectroscopy was carried out to gain
further insight into the solid state and solution phase structures.
Article history:
Received 22 January 2016
Accepted 19 February 2016
Available online xxxx
Keywords:
Metal–metal bonding
Alkaline earth
Transition metal
Amidinate
Guanidinate
Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction
Group 2 contains some of the most electropositive elements
and as a consequence Ae–TM bonds are considerably ionic. Any
Compounds containing metal–metal bonds have been the focus
of renewed attention for over a decade [1]. Reports of Zn–Zn [2] and
Mg–Mg [3] single bonds, transition metal quintuple bonds [4],
Group 12 homo- and hetero-trimetallic [5] species and myriad 4f
element– and 5f element–main group and transition metal bonded
complexes [6] have piqued interest in the synthesis, structure,
bonding and reactivity of such compounds. One area that has
received little attention until very recently is that of Ae–TM
(alkaline earth–transition metal) bonding. Since the first report of
Cp(DPPE)FeMgBr(THF)2 (1) [7] by Felkin in 1974 there have been
few examples of structurally authenticated Ae–TM bonded
complexes, most of which feature Ae = Mg. These include Green’s
Mg–Mo species Cp2Mo(H){MgBr(THF)2} [8], the Mg–Ir species
[Cp*Ir(PMe3)(H)MgPh]2 [9], and the two Mg–Co species
potential TM bond partner must therefore be able to accommodate
significant anionic charge. Investigation of the literature [14] for
similarly polar M–TM bonded species (e.g. where M = lanthanide
(Ln) or actinide (An)) [15] or early-late heterobimetallics [16]
reveals only a handful of metal anions that are routinely exploited
for these purposes. These ‘‘privileged anions” are [CpM(CO)2]ꢀ
(M = Fe (‘‘Fp”) or Ru (‘‘Rp”)), [Cp2Re]ꢀ, [Co(CO)4]ꢀ and its
monophosphine analogue [Co(CO)3(PR3)]ꢀ. Shore et al. have also
utilised the ‘‘supernucleophile” [Fe(CO)4]2ꢀ successfully to form
Yb–Fe bonded structures [17]. However attempts to extend this
to achieve Ae–TM bonds were unsuccessful [13]. Carbonylate
anions stabilise the build-up of negative charge on the TM moiety
through
ever, their presence introduces the possibility of Ae–(
p
back-donation from TM(d ) to C–O(p⁄) orbitals. How-
p
l-OC)–TM
CpCo(g
3-C3H5)MgBr(THF)2 (2) and CpCo(
g
2-C2H4)(Ph)MgBr
isocarbonyl bonding, which can often occur in preference to Ae–
TM bonding. This dilemma has been referred to by Kempe as
‘‘the isocarbonyl problem” [15] and has been similarly observed
by Marks for the highly oxophilic 5f elements in the pursuit of
An–TM bonds [18].
Work in our laboratories has recently led to the report of several
structurally authenticated Ae–TM bonded species, including
[MgFp2(THF)]2 (6) [12] and [Mg{Co(CO)3(PCy3)}2(THF)]2 (7) [13],
synthesised from the reductive cleavage of Fp2 and [Co(CO)3(PCy3)]2
by a Mg/Hg amalgam. These were found to undergo significant
(TMEDA) (3) [10]. The first Be–TM bonded compounds, (Cy3P)2Pt
{Be(Cl)X} (X = Cl or Me), were only characterised and structurally
authenticated as recently as 2009 [11]. Ca–TM bonds are even more
elusive; [CaFp2(THF)3]2 (4) [12] and [Ca{Co(CO)3(PCy3}2(THF)3]x (5)
[13] remain the only examples reported to date.
⇑
Corresponding authors.
E-mail
addresses:
matthew.blake@chem.ox.ac.uk
(M.P.
Blake),
philip.mountford@chem.ox.ac.uk (P. Mountford).
http://dx.doi.org/10.1016/j.poly.2016.02.028
0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

2
R. Green et al. / Polyhedron xxx (2016) xxx–xxx
structural changes in solution, with loss of the Mg–Fe interaction
for the latter. This gave us significant impetus to synthesise
In particular the bite angle of the amidinate in 9 (N(1)–Mg(1)–N
(2) = 64.29(6)°) is comparable with that for 10 (64.76(8)°).
(
DippNacNac)MgFp(THF)
(8,
Dipp = 2,6-diisopropylphenyl,
The salt-elimination reaction of 9 with K[Co(CO)3(PCy3)](THF)2
in THF gave {MesC(NiPr)2}Mg{Co(CO)3(PCy3)}(THF) (11) in 58% iso-
lated yield as illustrated in Scheme 1. Diffraction-quality crystals of
11 were grown from pentane at room temperature. The structure is
shown in Fig. 2 and selected distances and angles in Table 1. The
heterobimetallic species is monomeric in the solid state. The
geometry at the four-coordinate Mg centre is approximately tetra-
hedral with two bonds to the bidentate amidinate ligand and one
to each of the THF and Co(CO)3(PCy3) groups. The Mg–Co distance
(2.5310(7) Å) is comparable with our previously reported 7 (endo
Mg–Co 2.6163(6) and exo Mg–Co 2.5427(6) Å) [13] and Jonas’
complexes 2 (2.480(4) Å) and 3 (2.593(7) Å) [10]. The amidinate
bite-angle (N(1)–Mg(1)–N(2) = 65.28(7)°) is little changed from 9.
The geometry at the five-coordinate Co centre is approximately
trigonal bipyramidal with the three carbonyl groups lying in the
equatorial plane and the Mg and P atoms occupying the axial posi-
tions with a near-linear arrangement (Mg–Co–P = 174.58(2)°).
Interaction of the [Co(CO)3(PR3)]ꢀ anion with a cationic acceptor
RNacNac = HC{C(Me)NR}2), isolated from the salt-elimination reac-
tion of (DippNacNac)MgI(THF) and K[Fp] [19]. Complex 8 is soluble
in non-donor solvents and contains a Mg–Fe bond in both the solid
state and solution. Complex 8 features a b-diketiminate (NacNac)
ligand, ubiquitous in Ae chemistry for having stabilising and
solubilising properties [20]. Tuning of these properties can be
accomplished through variation of substituents on the N-atoms. A
complex featuring a larger Ae for instance, may be kinetically
stabilised via increased steric protection from bulky N-aryl groups.
Amidinates (R0C(NR)2) and guanidinates (R02NC(NR)2) are similar
classes of bidentate mono-anionic ligand that have been success-
fully deployed in Ae chemistry [21]. However, they are yet to be suc-
cessfully exploited for Ae–TM bonding. As with b-diketiminates,
these ligands can be readily modified at their N-substituents to
allow the properties of the complex to be tuned as required. Amid-
inates and guanidinates differ from b-diketiminates in having only
one, rather than three, backbone carbons. This results in formation
of a four-membered, rather than six-membered ring, when com-
plexed to the metal and a more acute N–Ae–N bite-angle (typically
between 63° and 65° [21a]), giving a potentially more accessible
is known to bring about a significant geometric change in the anion
P
[22]. The sum of the three P–Co–CO angles ( (P–Co–CO)) repre-
sents one measure of this geometric change and a way in which
the strength of interaction can be quantified. A greater strength
of interaction is expected to cause a deviation in this value away
metal centre to participate in metal–metal bonding with
a
suitable anion. We were therefore interested to see if our initial
success with 8 could be extended to complexes with amidinate
and guanidinate supporting ligands with a view to increasing the
breadth of Ae–TM bonded systems, particularly those where
metal–metal bonding is maintained in solution.
from that of the tetrahedral free anion towards that of trigonal
P
bipyramidal geometry. In the case of 11
(P–Co–CO) = 302.27
(12)° consistent with a significant interaction between the Mg
and Co centres and very similar to that measured for our recently
reported Mg–Co bonded 7 (300.9(2)° and 303.2(2)°) and Ca–Co
bonded 5 (305.8(3)°) [13].
2. Results and discussion
The solid state IR spectrum of 11 shows three main higher fre-
quency
lower frequency
structure without Mg(
m
(CO) bands at 1963, 1922 and 1879 cmꢀ1 and no significant
2.1. Magnesium amidinate complexes
m
(CO) bands, consistent with a Mg–Co bonded
l-OC)Co isocarbonyl bridging. The solution
[{MesC(NiPr)2}Mg(
l
-Br)(OEt2)]2 (9) was prepared in 88% yield
IR spectrum of 11 in toluene is more complicated with three m(CO)
i
from PrNCNiPr and MesMgBr in Et2O using an analogous proce-
dure to that reported by Coles et al. [21c]. Diffraction-quality
crystals of 9 were grown from an Et2O solution at 5 °C. The
structure is shown in Fig. 1. Complex 9 is dimeric in the sold
bands at 1969, 1904 and 1895 cmꢀ1, attributed to a Mg–Co bonded
species, and lower frequency bands at 1839 and 1755 cmꢀ1, possi-
bly indicative of more complex behaviour in solution.
Reaction of 9 with K[Fp] in THF-d8 on the NMR tube scale
showed quantitative formation of {MesC(NiPr)2}MgFp(THF) by 1H
NMR spectroscopy. However, benzene extraction during the
preparative scale reaction resulted in a complex mixture of prod-
ucts, evidenced by the presence of multiple ligand environments
and Fp2 in the 1H NMR spectrum, the latter being a common
decomposition product in the chemistry of the [Fp]ꢀ anion [23].
Given the stability of 11 in a non-donor solvent, the apparent
decomposition of the desired Mg–Fe bonded species was some-
what unexpected. Of note is that the related 8 is also successfully
isolated via a benzene extraction. It was postulated that substitut-
ing the N-bound iPr groups for more sterically demanding Dipp or
Mes (Mes = 2,4,6-trimethylphenyl) groups would improve the
overall complex stability and allow isolation of an amidinate
Mg–Fe, alongside Mg–Co, bonded complex.
state with two
l-Br bridging the Mg centres. Each Mg centre is
five-coordinate with distorted trigonal bipyramidal geometry.
Distances and angles are as expected and similar to that reported
by Coles for the analogous [{MesC(NCy)2}Mg(l-Br)(OEt2)]2 (10).
The synthesis of the required carbodiimide, DippNCNDipp (12),
has been reported in the literature previously, albeit on a relatively
small scale, from the reaction of Dipp(H)NC(S)N(H)Dipp with HgO/
MgSO4 [24]. A report by Patel et al. details the conversion of arylth-
ioureas to carbodiimides via reaction with I2 in the presence of
NEt3 [25]. Using this general procedure Dipp(H)NC(S)N(H)Dipp
was converted to 12. However, the carbodiimide was contami-
nated with residual elemental sulfur. A modified procedure was
therefore developed based on a report by Blumer [26] in which
the contaminated hydrocarbon solution of carbodiimide was trea-
ted with an excess of activated Cu, thereby removing the elemental
sulfur as insoluble CuS and giving 12 in 65% isolated yield.
Fig. 1. Displacement ellipsoid plot (20% probability) of [{MesC(NiPr)2}Mg(
l-Br)
(OEt2)]2 (9). H atoms omitted. Atoms carrying the suffix ‘A’ are related to their
counterparts by the symmetry operator 1 ꢀ x, 1 ꢀ y, 1 ꢀ z. Selected distances (Å)
and angles (°): Mg(1)–Br(1) 2.6677(8), Mg(1)–Br(1A) 2.5560(8), Mg(1)–N(1) 2.1144
(17), Mg(1)–N(2) 2.0757(17), Mg(1)–O(1) 2.0398(16), N(1)–Mg(1)–N(2) 64.29(6), N
(1)–Mg(1)–Br(1) 164.69(5), N(1)–Mg(1)–Br(1A) 101.55(6), N(1)–Mg(1)–O(1) 97.40
(7), N(1)–C(1)–N(2) 114.02(17), Br(1)–Mg(1)–Br(1A) 87.36(3).
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

R. Green et al. / Polyhedron xxx (2016) xxx–xxx
3
THF
R
Cp
Fe
Mg
N
CO
N
CO
Mes
R
R = Dipp (15), Mes (19)
K[CpFe(CO)2]
THF
R
Mes
N
OEt2
Mg
R
Br
Br
N
Mg
RN=C=NR
Et2O
1
MesMgBr
/
2
N
R
OEt2
N
Mes
R
R = iPr (9), Dipp (13), Mes (17)
K[Co(CO)3(PCy3)](THF)2
THF
THF
Mg
CO
R
Co
PCy3
CO
N
N
CO
Mes
R
i
11
14
18
R = Pr ( ), Dipp ( ), Mes (
)
Scheme 1. Synthetic routes to Mg–Fe (15, 19) and Mg–Co (11, 14, 18) bonded amidinate complexes.
Table 1
Selected bond lengths (Å) and angles (°) for {MesC(NiPr)2}Mg{Co(CO)3(PCy3)}(THF)
(11).
Mg(1)–Co(1)
Mg(1)–N(2)
Co(1)–P(1)
Co(1)–C(18)
2.5310(7)
2.0498(17)
2.2071(5)
1.759(2)
Mg(1)–N(1)
Mg(1)–O(4)
Co(1)–C(17)
Co(1)–C(19)
2.0777(18)
2.0312(16)
1.745(2)
1.745(2)
C(1)–N(1)
1.332(3)
C(1)–N(2)
1.327(3)
Co(1)–Mg(1)–N(1)
Co(1)–Mg(1)–O(4)
N(1)–Mg(1)–O(4)
Mg(1)–Co(1)–P(1)
Mg(1)–Co(1)–C(18)
P(1)–Co(1)–C(17)
P(1)–Co(1)–C(19)
C(17)–Co(1)–C(19)
N(1)–C(1)–N(2)
137.70(6)
109.92(5)
106.23(7)
174.58(2)
80.87(7)
Co(1)–Mg(1)–N(2)
N(1)–Mg(1)–N(2)
N(2)–Mg(1)–O(4)
Mg(1)–Co(1)–C(17)
Mg(1)–Co(1)–C(19)
P(1)–Co(1)–C(18)
C(17)–Co(1)–C(18)
C(18)–Co(1)–C(19)
120.64(6)
65.28(7)
108.22(7)
76.45(7)
80.20(7)
98.62(7)
99.02(7)
104.63(7)
115.48(11)
113.75(17)
115.17(10)
119.07(11)
Fig. 2. Displacement ellipsoid plot (25% probability) of {MesC(NiPr)2}Mg{Co(CO)3(-
PCy3)}(THF) (11). H atoms omitted for clarity.
observed in 11 which features less bulky N–iPr substituents on
the amidinate ligand. This can be attributed to one or two different
effects. First, the orientation of the Dipp groups in 14 away from
the metal anion. In the case of 11 the iPr substituents orient them-
selves such that the Me groups are pointing away from the Mes
group and towards the Co centre, potentially increasing the Mg–
Co distance as a result. This effect may be viewed as an extension
of that reported by Jordan et al. for steric repulsion within steri-
cally demanding amidinate aluminium systems [27]. In addition,
the N-aryl substituted ligand in 14 gives a more electrophilic Mg
centre than the N-alkyl functionalised ligand in 11. Consistent with
this, the Mg–N distances are shorter in 11 (2.0498(17) and 2.0777
Reaction of 12 with MesMgBr in Et2O gave [{MesC(NDipp)2}Mg
(l-Br)(OEt2)]2 (13) in 67% isolated yield. Whilst crystalline samples
of 13 could be isolated these were not suitable for analysis by sin-
gle crystal X-ray diffraction. Reaction of 13 with K[Co(CO)3(PCy3)]
(THF)2 in THF followed by pentane extraction gave {MesC(NDipp)2}
Mg{Co(CO)3(PCy3)}(THF) (14) as a grey solid in 39% isolated yield.
Diffraction-quality crystals of 14 were grown from a benzene solu-
tion at room temperature. The structure of 14 is monomeric in the
solid state (Fig. 3) containing a four-coordinate magnesium centre
with approximately tetrahedral geometry. Somewhat surprisingly
the Mg–Co distance (2.5193(5) Å) in 14 is shorter than that
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

4
R. Green et al. / Polyhedron xxx (2016) xxx–xxx
Mg–Fe bonded 8 in toluene was recorded and showed two
bands at 2017 and 1925 cmꢀ1. The experimentally identical posi-
tion of the (CO) bands in 8 and 15 strongly support the latter as
m(CO)
m
being Mg–Fe bonded in solution.
MesNCNMes (16) was synthesised from Mes(H)NC(S)N(H)Mes
using an analogous procedure to that employed for Dipp(H)NC(S)
N(H)Dipp. Reaction of 16 with MesMgBr in Et2O gave [{MesC
(NMes)2}Mg(l-Br)(OEt2)]2 (17) in 93% isolated yield. Diffraction-
quality crystals of 17 were grown from an Et2O solution at 5 °C.
X-ray crystallographic studies confirmed 17 as having a dimeric
structure in the solid state, very similar to that observed for 9.
The solid state structure of 17 and a table containing selected dis-
tances and angles for 9 and 17 is presented in the SI. 1H NMR anal-
ysis of crystals of 17 grown from Et2O shows one equivalent of Et2O
per amidinate ligand. However, prolonged drying of the bulk mate-
rial in vacuo leads to loss of Et2O and two distinct amidinate ligand
environments in the 1H NMR spectrum recorded in C6D6. In con-
trast, the 1H NMR spectrum recorded for 17 in THF-d8 shows only
one set of ligand environments consistent with a single species.
Reaction of 17 with K[Co(CO)3(PCy3)](THF)2 in THF followed by
benzene extraction gave {MesC(NMes)2}Mg{Co(CO)3(PCy3)}(THF)
(18) as a white solid in 84% isolated yield. The solid state IR spec-
Fig. 3. Displacement ellipsoid plot (25% probability) of {MesC(NDipp)2}{MgCo
(CO)3(PCy3)}(THF) (14).
H atoms and independent molecule of protio-ligand
omitted for clarity.
trum of 18 shows a large number of m(CO) bands at 1964, 1937,
(18) Å) than 14 (2.0590(12) and 2.0983(13) Å), and hence the N
1885, 1865 and 1720 cmꢀ1. Comparison with the IR data for 14
(1)–Mg(1)–N(2) bite-angle in 14 (64.51(5)°) is slightly more acute
suggests that those at 1964, 1885 and 1865 cmꢀ1 are attributable
P
than in 11 (65.28(7)°). For 14 (P–Co–CO) = 301.37(9)°, very sim-
ilar to that for 11 (302.27(12)°), indicative of a significant interac-
tion between the metal centres (see Table 2).
to the A1- and two E-type
meric Mg–Co complex. The bands at 1937 and 1720 cmꢀ1 are likely
to be for a secondary species which exhibits Mg( -OC)Co isocar-
bonyl interactions. The solution IR spectrum of 18 in toluene shows
(CO) bands at 1970, 1910, 1890, 1836 and 1755 cmꢀ1, again con-
m(CO) stretching modes of the mono-
l
The solid state IR spectrum of 14 shows two strong
at 1965 and 1873 cmꢀ1, the latter of which is broad and may
comprise two overlapping bands. There are no (CO) bands at
m(CO) bands
m
m
sistent with two species with at least one band in the range indi-
cating an isocarbonyl interaction. These data are in contrast to
lower frequencies, indicating an absence of isocarbonyl interac-
tions in the solid state. The solution IR of 14 in toluene shows only
three m
(CO) bands at 1968, 1891 and 1840 cmꢀ1, consistent with
those of 14, which showed no significant low frequency
m(CO)
bands in solution or the solid state, and was confirmed to be
Mg–Co bonded by X-ray crystallography.
preservation of the Mg–Co bond in solution.
Reaction of 13 with K[Fp] in THF followed by benzene extrac-
tion gave {MesC(NDipp)2}MgFp(THF) (15) as a light brown solid
in 74% yield. This is in contrast to the attempted reaction of 9 with
K[Fp] to form {MesC(NiPr)2}MgFp(THF) which was unstable in
non-donor solvents. Although diffraction-quality crystals of 15
could not be grown, 1H and 13C{1H} NMR spectroscopic data are
consistent with formation of the desired species. A diffusion NMR
spectroscopic study of 15 (see below) suggests that it is monomeric
The reaction of 17 with K[Fp] in THF followed by benzene extrac-
tion gave {MesC(NMes)2}MgFp(THF) (19) by 1H NMR spectroscopy,
albeit accompanied by other ligand environments. This susceptibil-
ity to decomposition in non-donor solvents was also observed for
the product of the reaction between 9 and K[Fp]. To combat this
decomposition the procedure was modified to use THF as the only
solvent. This allowed isolation of {MesC(NMes)2}MgFp(THF) (19)
as a light brown solid in 68% isolated yield. The solid state IR spec-
in toluene. The solid state IR spectrum of 15 shows four m(CO)
trum of 19 showed two main
Notably absent are lower frequency
m
(CO) bands at 1923 and 1858 cmꢀ1
(CO) bands that would
.
bands: two strong bands at 1930 and 1866 and medium intensity
bands at 1961 and 1791 cmꢀ1. The solution IR spectrum of 15 in
m
toluene shows two m
(CO) bands at 2017 and 1925 cmꢀ1 consistent
indicate the presence of isocarbonyl interactions. The solution IR
spectrum of 19 in THF is more complicated but nonetheless
with a non-isocarbonyl bridged species in the solution phase. For
comparison, the solution IR spectrum of structurally authenticated
dominated by m
(CO) bands at 1921 and 1861 cmꢀ1. Reassuringly,
the previously reported solution IR spectrum of Mg–Fe bonded 8
in THF similarly shows bands at 1926 and 1871 cmꢀ1 [19].
Table 2
Selected bond lengths (Å) and angles (°) for {MesC(Dipp)2}Mg{Co(CO)3(PCy3)}(THF)
(14).
2.2. Magnesium guanidinate complexes
Guanidinate ligands (R02NC(NR)2) are structurally and geomet-
rically very similar to amidinate ligands but have subtly different
electronic properties as a result of the distal nitrogen. Donation
of electron density from this nitrogen has the ultimate effect of
increasing the overall ligand Lewis basicity, potentially increasing
the strength of interaction with the Lewis acidic Ae centre and
overall complex stability as a result [28]. Given our successful syn-
thesis of Mg–TM complexes using the Dipp substituents in both
our NacNac and aforementioned amidinate systems we selected
this for the R-group in these complexes. Whilst a range of bulky
R0 groups for the distal nitrogen have been reported [21a], these
offer little steric protection at the Mg centre and primarily have
Mg(1)–Co(1)
Mg(1)–N(2)
Co(1)–P(1)
Co(1)–C(36)
2.5193(5)
2.0983(13)
2.2026(4)
1.7494(16)
1.3356(17)
118.74(4)
109.46(4)
116.86(5)
174.780(18)
80.13(5)
Mg(1)–N(1)
Mg(1)–O(4)
Co(1)–C(35)
Co(1)–C(37)
2.0590(12)
2.0317(11)
1.7580(16)
1.7605(16)
1.3531(18)
134.60(4)
64.51(5)
106.64(5)
80.37(5)
78.54(5)
C(1)–N(1)
C(1)–N(2)
Co(1)–Mg(1)–N(1)
Co(1)–Mg(1)–O(4)
N(1)–Mg(1)–O(4)
Mg(1)–Co(1)–P(1)
Mg(1)–Co(1)–C(36)
P(1)–Co(1)–C(35)
P(1)–Co(1)–C(37)
C(35)–Co(1)–C(37)
N(1)–C(1)–N(2)
Co(1)–Mg(1)–N(2)
N(1)–Mg(1)–N(2)
N(2)–Mg(1)–O(4)
Mg(1)–Co(1)–C(35)
Mg(1)–Co(1)–C(37)
P(1)–Co(1)–C(36)
C(35)–Co(1)–C(36)
C(36)-Co(1)-C(37)
104.51(5)
100.97(5)
112.35(7)
111.23(12)
95.89(5)
116.22(7)
121.96(7)
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R. Green et al. / Polyhedron xxx (2016) xxx–xxx
5
a solubilising effect. Therefore, given the solubilising R-groups
already selected, we opted for a simple NMe2 group.
supporting ligand. Being shorter than those in Felkin’s 1 (2.593
(7) Å) [7], the Mg–Fe distances in 22 are the shortest reported to
date [14].
The absence of a coordinated donor solvent in 22, that is, it is
isolated ‘‘base-free”, is notable. All reported Mg–Fe bonded com-
plexes to date have THF bonded by virtue of their syntheses.
Indeed the only structurally authenticated base-free Ae–TM
Reaction of LiNMe2 with DippNCNDipp, followed by an aqueous
workup gave the protio-ligand Me2NC(NDipp)(NHDipp) (20) as a
white solid in 69% isolated yield. Crystals of 20 suitable for analysis
by X-ray diffraction were grown from a hexane solution at RT. The
structure of 20 and selected distances and angles are presented in
the SI.
Reaction of 20 with MeMgI afforded {Me2NC(NDipp)2}MgI
(OEt2) (21) as a white solid in 95% isolated yield. Crystals of 21 suit-
able for analysis by X-ray diffraction were grown from benzene at
room temperature. The structure of 21, shown in Fig. 4, has a four-
coordinate Mg centre with approximately tetrahedral coordination
geometry, with two Mg–N bonds to the bidentate guanidinate
ligand and one bond to each of the iodine and ether ligands. The
N(1)–Mg(1)–N(2) bite-angle (66.86(13)°) is similar to that for the
bonded complex reported to date is Jones’ Mg–Mn bonded
(
MesNacNac)MgMnN(Ar⁄)SiiPr3 (Ar⁄ = C6H2{C(H)Ph2}2 Pr-2,6,4) syn-
i
thesised by the reaction of [(MesNacNac)Mg]2 with [(iPr3Si(Ar⁄)N)
Mn( -Br)(THF)]2 in cyclohexane [29]. The lack of coordinated
l
Et2O in the bulk sample of 22 is confirmed by the absence of signals
attributable to Et2O in the 1H or 13C{1H} NMR spectra. Our recent
findings have shown the presence of coordinated donor groups to
be potentially very disruptive to Ae–TM bonding, favouring the for-
mation of isocarbonyl linkages and in extreme cases separated ion
pairs [13]. Therefore, to isolate a base-free Ae–TM bonded complex
is significant and may enable enhanced reactivity in future studies.
To investigate the potential interaction of 22 with THF, a sample of
22 was dissolved in THF then volatiles removed under reduced
pressure and the solid dried in vacuo. 1H NMR analysis showed
there to be no THF present. This lack of coordination and therefore
maintenance of the dimeric structure is somewhat remarkable but
would appear to be the exception rather than rule for the series of
guanidinate complexes investigated in this study (see below). The
structurally similar (Priso)Mg(l–I)2Mg(OEt2)(Priso) (66.47(8)°,
Priso = iPr2NC(NDipp)2) reported by Jones et al. [3]. It is also similar
to the aforementioned Mg–Br (9: 64.29(6)°, 17: 63.44(6)°) and
Mg–Co (11: 65.28(7)°, 14: 64.51(5)°) bonded amidinate complexes
consistent with the concept of
a similar geometry despite
substitution of a mesityl for the more electron-donating NMe2
group (see Scheme 2).
Initial attempts to synthesise [{Me2NC(NDipp)2}MgFp(THF)x]n
by reacting 21 with K[Fp] in THF were unsuccessful. Analysis of
this reaction on the NMR tube scale showed there to be no conver-
sion to the desired product, contrasting with the syntheses of 8 and
15, which proceeded under ambient conditions. Gratifyingly how-
ever, repeating the reaction on the NMR tube scale in C6D6 gave
quantitative conversion to [{Me2NC(NDipp)2}MgFp]2 (22) by 1H
NMR. The reaction was scaled-up, affording 22 as a yellow solid
in 64% isolated yield (Scheme 3).
Crystals of 22 suitable for analysis by X-ray diffraction were
grown from a benzene solution at 5 °C. The structure is shown in
Fig. 5 and selected distances and angles in Table 3. Complex 22
crystallises as a dimer in the solid state with two Mg–Fe bonds
solid state IR spectrum of 22 shows two main m(CO) bands at 1944
and 1778 cmꢀ1. The former is attributed to the terminal carbonyl
and latter to the isocarbonyl groups, consistent with the structure
determined by X-ray crystallography. The solution IR spectrum of
22 in toluene also shows
1781 cmꢀ1, consistent with isocarbonyl interactions in solution.
The solution IR spectrum in THF was dominated by two major
(CO) bands (2014 and 1946 cmꢀ1) consistent with dissociation to
monomeric structure without isocarbonyl bridging, most
a low frequency m(CO) band at
m
a
probably a THF adduct.
Given the successful synthesis of 22 in benzene, this was also
attempted for the reaction between 21 and K[Co(CO)3(PCy3)]
(THF)2, giving {Me2NC(NDipp)2}Mg{Co(CO)3(PCy3)}(OEt2) (23) as
a red solid in 68% isolated yield. Crystals of 23 suitable for analysis
by X-ray crystallography could not be obtained. However, unlike
22, the presence of one coordinated Et2O per set of ligand environ-
and two Mg(l-OC)Fe linkages. Each Mg centre is four-coordinate
with an approximately tetrahedral geometry. The Mg–Fe bond
distances (2.5279(4) Å) are shorter than those in monomeric 8
(2.6326(4) Å) [19], which also features a considerably larger
bite-angle compared to 22 (90.97(4)° versus 66.00(4)°). The
Mg–Fe distances are also shorter than those in dimeric 6 (2.6112
(5) & 2.5629(5) Å), which does not feature a sterically demanding
ments is apparent by 1H NMR spectroscopy. Low frequency
m(CO)
bands are absent in the solid state IR spectrum, consistent with
no isocarbonyl bridging, suggesting a monomeric Mg–Co bonded
structure. The solution IR spectrum of 23 in toluene also supports
this, having only three m
(CO) bands (1962, 1858, 1804 cmꢀ1), all at
comparatively high frequency. These observations are consistent
with that for the structurally authenticated monomeric Mg–Co
bonded complex 14 which also exhibits three m(CO) bands (1968,
1891 and 1840 cmꢀ1) at high frequency only. It is notable that
the bands in 23 are at a lower frequency than the respective bands
in 14. This is consistent with the greater electron donating effect of
the guanidinate versus amidinate ligand and ultimately increased
back-donation of electron density from the Co(d ) to C–O(p⁄
)
p
orbitals.
The [Co(CO)3(PPh3)]ꢀ anion has been shown to be a viable anion
for metal–metal bonding, with a range of structurally authenti-
cated examples [14] featuring bonds to transition metals, main
group metals and also electropositive metals such as in Liddle’s
U–Co bonded (TsXyl)U{Co(CO)3(PPh3)} (TsXyl = HC(SiMe2NXyl)3;
Xyl = 3,5-dimethylphenyl) [30]. However, our recent studies with
this anion in combination with unsupported alkaline earth systems
such as Ca{Co(CO)3(PPh3)}2(THF)4 showed these complexes to have
poor solubility in non-donor solvents (Mg{Co(CO)3(PPh3)}2(THF)x
was insoluble in THF) necessitating manipulations and crystallisa-
tions from THF, giving complexes with isocarbonyl bridging
Fig. 4. Displacement ellipsoid plot (20% probability) of {Me2NC(NDipp)2}MgI(OEt2)
(21). H atoms omitted for clarity. Selected distances (Å) and angles (°): Mg(1)–I(1)
2.6500(13), Mg(1)–N(1) 2.052(3), Mg(1)–N(2) 2.040(3), Mg(1)–O(1) 2.029(3), N(1)–
Mg(1)–N(2) 66.86(13), N(1)–C(1)–N(2) 112.8(3).
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

6
R. Green et al. / Polyhedron xxx (2016) xxx–xxx
OEt2
Mg
Dipp
I
i) LiNMe2, ii) H2O
THF
N
MeMgI
Et2O
DippN=C=NDipp
Me2NC(NDipp)(NHDipp)
N
20
Me2N
Dipp
21
Scheme 2. Synthesis of {Me2NC(NDipp)2}MgI(OEt2) (21).
Dipp
Me2N
N
Cp
N
Mg
OC
Fe
Dipp
CO
OC
Dipp
Fe
CO
Mg
N
N
Cp
NMe2
Dipp
22
K[CpFe(CO)2]
Benzene
OEt2
OEt2
Mg
CO
Dipp
Dipp
Mg
I
K[Co(CO)3(PCy3)](THF)2
Benzene
N
Co
PCy3
CO
N
N
N
Me2N
CO
Me2N
Dipp
Dipp
21
23
K[Co(CO)3(PPh3)](THF)
Benzene
OEt2
CO
Dipp
Mg
Co
PPh3
CO
N
N
CO
Me2N
Dipp
25
Scheme 3. Synthesis of guanidinate Mg–Fe bonded 22 and Mg–Co bonded 23 and 25 from 21.
between the metal centres only [13]. Therefore we were interested
to see if use of a supporting, solubilising ligand could enable the
isolation of a complex with the [Co(CO)3(PPh3)]ꢀ anion that could
be crystallised in the absence of a donor-solvent thus favouring a
principal m
(CO) bands (2049, 1976, 1896 cmꢀ1), all at high fre-
quency, consistent with a monomeric Mg–Co bonded structure as
with 23. The higher frequency A1 stretch for 25 compared to that
of 23 is consistent with the lower
r-donating ability of the PPh3
Mg–Co over Mg(l-OC)Co interaction. Complex 21 was reacted
compared to PCy3 group and resultant decreased Co(d ) to C–O
p
with K[Co(CO)3(PPh3)](THF) (24, structure in the SI) in benzene
to afford {Me2NC(NDipp)2}Mg{Co(CO)3(PPh3)}(OEt2) (25) as a red
solid in 58% isolated yield. As with 23, crystals suitable for analysis
by X-ray crystallography could not be obtained. NMR spectroscopic
analysis confirms there is one Et2O per set of guanidinate ligand
environments, consistent with that for 23. The solid state IR
(
p⁄) back bonding.
2.3. Diffusion NMR spectroscopy
We used diffusion NMR spectroscopy to further investigate the
solution phase structures of complexes 14, 15, 18, 22 and 23. The
results are shown in Table 4, together with comparative reference
data for 8.
spectrum for 25 shows no significant low frequency
m(CO) bands.
Also the solution IR spectrum for 25 in toluene shows only three
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R. Green et al. / Polyhedron xxx (2016) xxx–xxx
7
state structure for 18 could not be determined but its effective
monomeric volume based on the 18 Å3 rule (1116 Å3) is similar
to that determined by NMR (1224 Å3). Therefore based on diffusion
NMR measurements the amidinate complexes 14, 15 and 18 are
monomeric in solution.
Turning to the guanidinate complexes, 22 has a solution effec-
tive volume (1139 Å3) very similar to that for the dimeric solid
state structure (1239 Å3). The close match in effective volume sug-
gests very little, if any, dissociation in toluene at this concentration.
This is consistent with the IR spectroscopic data where a low fre-
quency band, indicative of an isocarbonyl bridging interaction, is
present in both the solid state and toluene. Diffusion NMR mea-
surements were also made in THF-d8. These showed a solution
effective volume (663 Å3) very close to half of that for the dimeric
solid state structure, consistent with dissociation to monomeric
units in the donor solvent environment as supported by IR spec-
troscopy in THF solution. Although a solid state structure could
not be obtained, diffusion NMR measurements for 23 were carried
out. There is a significant disparity (ca. 33%) between the solution
effective volume (849 Å3) and that expected for a dimeric solid
state structure (1116 Å3) based on the 18 Å3 rule. Whilst it may
be the case that solid state volume is overestimated, the fact that
the measured solution effective volume is significantly below this
is strongly indicative of a monomeric structure in solution.
Fig. 5. Displacement ellipsoid plot (20% probability) of [{Me2NC(NDipp)2}MgFp]2
(22). H atoms and solvent of crystallisation omitted for clarity. Atoms carrying the
suffix ‘A’ are related to their counterparts by the symmetry operator 1 ꢀ x, 1 ꢀ y,
1 ꢀ z.
3. Conclusion
Table 3
Selected bond lengths (Å) and angles (°) for [{Me2NC(NDipp)2}MgFp]2 (22).
We have reported the first examples of amidinate and guanidi-
nate supported Ae–TM bonded complexes ultimately synthesised
from reduction of their corresponding carbodiimides. In order to
achieve this on a suitable scale we developed an improved syn-
thetic procedure via the corresponding thiourea. Structurally
authenticated examples of Ae–TM bonded species have been
achieved featuring Mg bonded to the [Fp]ꢀ and [Co(CO)3(PCy3)]ꢀ
anions. A guanidinate magnesium complex using the [Co(CO)3(-
PPh3)]ꢀ anion was also synthesised. IR analysis is consistent with
Mg(1)–Fe(1)
Mg(1)–N(1)
Fe(1)–C(1)
Fe(1)–Mg(1)–O(1A)
Fe(1)–Mg(1)–N(2)
N(1)–C(3)–N(2)
2.5279(4)
2.0620(10)
1.6985(12)
108.46(3)
137.58(3)
113.05(10)
Mg(1)–O(1A)
Mg(1)–N(2)
Fe(1)–C(2)
Fe(1)–Mg(1)–N(1)
N(1)–Mg(1)–N(2)
2.0552(10)
2.0627(10)
1.7469(14)
121.23(3)
66.00(4)
The structure of 8 is known to be monomeric in the solid state
and solution. It is also structurally similar to the amidinate and
guanidinate complexes studied in this investigation making it a
suitable reference molecule. Indeed the solution effective molecu-
lar volume in toluene (519 Å3) and THF (536 Å3) are similar to that
expected (698 Å3) based on the solid state structure. There is good
agreement between the effective volume for 14 in the solid state
(1034 Å3) and solution (1209 Å3) supporting this as being a mono-
mer in both environments. It was not possible to obtain a solid
state structure for 15, making the diffusion NMR measurement
for this particularly insightful. The solution effective volume
(812 Å3) is similar to that for a monomeric structure (936 Å3) based
on that predicted using the 18 Å3 rule [31]. As with 15, the solid
this being Mg–Co rather than Mg(l-OC)Co bonded in both the solid
state and solution. Crucially this introduces another anion to the
limited number shown to be capable of bonding with the alkaline
earth metals without suffering from the ‘‘isocarbonyl problem”.
Diffusion NMR spectroscopy measurements on a series of these
complexes are consistent with them existing as monomers in
toluene-d8 with the exception of [{Me2NC(NDipp)2}MgFp]2 (22)
where a dimeric structure is maintained. However, measurements
in THF-d8 were consistent with dissociation of 22 to monomeric
units. Complex 22 was also shown to be a very rare example of a
‘‘base-free” Ae–TM complex and as having the shortest Mg–Fe
bond reported to date.
Table 4
Diffusion NMR data for (DippNacNac)MgFp(THF) (8), {MesC(NDipp)2}Mg{Co(CO)3(PCy3)}(THF) (14), {MesC(NDipp)2}MgFp(THF) (15), {MesC(NMes)2}Mg{Co(CO)3(PCy3)}(THF) (18),
[{Me2NC(NDipp)2}MgFp]2 (22), and {Me2NC(NDipp)2 }Mg{Co(CO)3(PCy3)}(OEt2) (23).
c
c
Compound
Solvent
X-ray volume (Å3)a
NMR volume (Å3)b
D (mean) ꢁ 10ꢀ10 (m2 sꢀ1
)
D (Solvent) ꢁ 10ꢀ10 (m2 sꢀ1
)
8
14
15
18
22
23
8
Toluene-d8
Toluene-d8
Toluene-d8
Toluene-d8
Toluene-d8
Toluene-d8
THF-d8
698
1034
936*
519
1209
812
1224
1139
849
7.96
6.01
6.87
5.98
6.12
6.75
9.94
8.84
22.02
21.21
17.72
18.45
20.19
19.63
27.43
26.76
1116*
1239
1116*
698
536
663
22
THF-d8
1239
a
*
b
c
Molecular volume based on the caption formula and X-ray crystal structures measured using 1.4 Å probe radius. Volumes denoted with.
are instead based on that expected for a monomeric structure using the 18 Å3 rule.
Molecular volume measured by diffusion NMR spectroscopy in toluene-d8 or THF-d8.
Diffusion coefficient of the compound and the residual protio solvent in the sample under consideration (for comparison the diffusion coefficients for the protio solvents
were 23.54 ꢁ 10ꢀ10 m2 sꢀ1 in pure toluene-d8 and 27.0154 ꢁ 10ꢀ10 m2 sꢀ1 in pure THF-d8). Further details are provided in the SI.
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

8
R. Green et al. / Polyhedron xxx (2016) xxx–xxx
4.4. {MesC(NiPr)2}Mg{Co(CO)3(PCy3)}(THF) (11)
To [{MesC(NiPr)2}Mg(
4. Experimental
l
-Br)(OEt2)]2 (400 mg, 0.472 mmol) and K
4.1. General
[Co(CO)3(PCy3)](THF)2 (572 mg, 0.944 mmol) was added THF
(20 mL). The brown solution was stirred for 3 h before removal of
volatiles under reduced pressure. The dark brown solid was
extracted with benzene (3 ꢁ 5 mL) and volatiles removed under
reduced pressure. The residue was washed with cold pentane
(10 mL, ꢀ78 °C) and dried in vacuo to afford 11 as a grey-brown
solid. Yield: 418 mg (58%). 1H NMR (C6D6, 400.2 MHz): d 6.79 (2
H, s, C6H2), 4.13 (4 H, s, OCH2), 3.19 (2 H, br sept, 3J = 5.3 Hz,
All manipulations were carried out using standard Schlenk line
or dry-box techniques under an atmosphere of argon or dinitrogen.
Solvents were either degassed by sparging with dinitrogen and
dried by passing through a column of the appropriate drying agent
(benzene, pentane and hexane) [32]. Alternatively solvents were
predried over activated 4 Å molecular sieves and refluxed over
sodium (toluene), potassium (THF) or sodium–potassium alloy
(Et2O) and distilled. Deuterated solvents were dried over sodium
(toluene-d8) or potassium (C6D6, THF-d8), distilled under reduced
pressure and stored under argon in Teflon valve ampoules. NMR
samples were prepared under dinitrogen in 5 mm Wilmad
507-PP tubes fitted with J. Young Teflon valves. 1H, 13C{1H} and
31P{1H} spectra were recorded on a Bruker Ascend 400 or Varian
Mercury-VX 300 at ambient temperature. 1H and 13C{1H} spectra
are referenced internally to residual protio-solvent (1H) or solvent
CHMe2), 2.43 (6 H, s, 2,6-C6H2Me3), 2.15 (3 H, s, 4-C6H2Me3),
2.04 (3 H, m, 1-C6H11), 1.79 (6 H, m, 4-C6H11), 1.64 (12 H, m,
2,6-C6H11), 1.35 (4 H, s, OCH2CH2), 1.24 (24 H, d & m overlapping,
3J = 5.3 Hz, CHMe2 & 3,5-C6H11). 13C{1H} NMR (C6D6, 100.6 MHz): d
210.2 (s, CO), 173.9 (s, CN2), 136.9 (s, 4-C6H2), 134.6 (s, 2,6-C6H2),
133.0 (s, 1-C6H2), 128.5 (s, 4-C6H2), 70.0 (s, OCH2), 46.8 (s, CHMe2),
37.6 (d, 1J = 16.8 Hz, 1-C6H11), 30.5 (s, 2,6-C6H11), 28.2 (d,
3J = 10.2 Hz, 3,5-C6H11), 27.0 (m, overlapping CHMe2 & 4-C6H11),
(
13C) resonances, and are reported relative to tetramethylsilane
(d = 0 ppm). 31P{1H} spectra were referenced externally to an 85%
H3PO4 solution. Assignments were confirmed as necessary with
the use of two-dimensional 1H–1H and 13C–1H NMR correlation
experiments. Diffusion NMR spectroscopic studies were performed
on a Bruker Avance III 500 spectrometer (further details are con-
tained in the SI). IR spectra were recorded on a Thermo Scientific
Nicolet iS5 FTIR spectrometer and samples prepared in a dry-box
as Nujol mulls between NaCl plates or as a solution (THF or
toluene) in a NaCl cell. Mass spectra were recorded by the mass
spectrometry service of Oxford University’s Department of
Chemistry. Elemental analyses were carried out by the Elemental
Analysis Service at London Metropolitan University.
25.3 (s, OCH2CH2), 21.2 (s, 4-C6H2Me3), 20.6 (s, 2,6-C6H2Me3). 31P
{1H} (C6D6, 162.0 MHz): d 70.0 (s). IR (NaCl plates, Nujol mull,
cmꢀ1): 3818 (w), 3438 (w), 1963 (m), 1922 (m), 1879 (s), 1864
(s), 1821 (m), 1756 (w), 1611 (w), 1582 (w), 1335 (m), 1240 (w),
1168 (w), 1143 (w), 1110 (m), 917 (w), 876 (w) 853 (m), 766
(w). IR (NaCl cell, toluene,
m
(CO), cmꢀ1): 2038 (w), 1969 (m),
1904 (s), 1895 (s), 1839 (m). It was not possible to obtain a
satisfactory elemental analysis for 11.
4.5. DippNCNDipp (12)
To
a stirring solution of DippN(H)C(S)N(H)Dipp (7.93 g,
20.0 mmol) and NEt3 (5.58 mL, 40.0 mmol) in ethyl acetate
(100 mL) was added I2 (5.58 g, 22.0 mmol) in portions over
30 min. The mixture was stirred for 2 h at room temperature then
filtered to give a brown solution. Volatiles were removed under
reduced pressure to give a brown solid. The solid was extracted
with pentane (4 ꢁ 50 mL), filtered through a silica plug and
the resultant brown solution added to activated Cu (3.00 g,
48.0 mmol). The mixture was stirred for 16 h at room temperature
to give a black suspension. The suspension was filtered through
silica to give a colourless solution. Volatiles were removed under
reduced pressure and the resultant solid was dried in vacuo to
afford 12 as a colourless crystalline solid. Yield: 4.74 g (65%). The
1H NMR spectrum was consistent with that reported by Cowley
et al. [24].
4.2. Starting materials
K[Fp] [33], [Co(CO)3(PPh3)]2 [34], K[Co(CO)3(PCy3)](THF)2 [13],
DippN(H)C(S)N(H)Dipp, MesN(H)C(S)N(H)Mes [24] and activated
Cu [26] were synthesised according to published procedures.
Metals and other reagents were purchased from Strem Chemicals,
Sigma Aldrich or Alfa Aesar and either used as received or purified
according to standard procedures.
4.3. [{MesC(NiPr)2}Mg(
l-Br)(OEt2)]2 (9)
To a stirring solution of MesMgBr in Et2O (60.0 mL, 0.5 M,
30.0 mmol) was added PrNCNiPr (4.50 mL, 29.0 mmol) dropwise.
i
4.6. [{MesC(NDipp)2}Mg(l-Br)(OEt2)]2 (13)
The solution was stirred for 18 h at room temperature to give a
white precipitate. The solid was isolated by filtration then washed
with cold Et2O (2 ꢁ 20 mL, ꢀ78 °C) before drying in vacuo to afford
9 as a white solid. Yield: 10.8 g (88%). Diffraction-quality crystals
were grown from an Et2O solution at 5 °C. 1H NMR (C6D6,
400.2 MHz): d 6.82 (s, 4 H, C6H2), 3.73 (8 H, quart, 3J = 7.0 Hz,
OCH2), 3.24 (4 H, sept, 3J = 5.9 Hz, CHMe2), 2.38 (12 H, s,
2,6-C6H2Me3), 2.16 (6 H, s, 4-C6H2Me3), 1.27 (24 H, d, 3J = 5.9 Hz,
To a stirring solution of MesMgBr in Et2O (43.0 mL, 0.3 M,
12.9 mmol) was added a solution of DippNCNDipp (12, 4.50 g,
12.4 mmol) in Et2O (30 mL) dropwise. The solution was stirred
for 18 h to give a white precipitate. The solid was isolated by filtra-
tion and washed with cold Et2O (2 ꢁ 50 mL, ꢀ78 °C) before drying
in vacuo to afford (13) as a white solid. Yield: 5.05 g (67%). 1H NMR
i
(C6D6, 400.2 MHz): d 7.02 (12 H, s, C6H3 Pr2), 6.34 (4 H, s, C6H2Me3),
CHMe2), 1.17 (12 H, t, 3J = 7.0 Hz, OCH2Me). 13C{1H} NMR (C6D6,
100.6 MHz): d 173.9 (CN2), 136.8 (4-C6H2), 134.5 (2,6-C6H2),
3.60 (8 H, s, OCH2), 3.33 (8 H, br s, CHMe2), 2.04 (12 H, s,
2,6-C6H2Me3), 1.81 (6 H, s, 4-C6H2Me3), 1.38 (24 H, s, CHMe2),
1.07 (24 H, s, CHMe2), 0.91 (12 H, s, OCH2Me). 13C{1H} NMR
133.6 (1-C6H2), 128.4 (3,5-C6H2), 65.5 (OCH2), 47.2 (CHMe2), 26.9
i
(CHMe2), 21.2 (4-C6H2Me3), 20.5 (2,6-C6H2Me3), 14.5 (OCH2Me).
IR (NaCl plates, Nujol mull, cmꢀ1): 1355 (m), 1340 (m), 1233 (m),
1181 (m), 1166 (m), 1119 (m), 1090 (m), 1051 (m), 998 (m), 902
(w), 860 (m), 836 (w), 824 (w), 783 (m), 767 (m), 693 (w). EI-MS
m/z = 499 (95%) [{MesC(NiPr)2}Mg{(NiPr)2C(C6H2Me2)}]+. It was
not possible to obtain a satisfactory elemental analysis for 9.
(C6D6, 100.6 MHz):
d
175.0 (CN2), 142.9 (2-C6H3 Pr2), 141.7
i
i
(6-C6H3 Pr2), 141.2 (1-C6H3 Pr2), 137.9 (4-C6H2Me3), 137.0
(2,6-C6H2Me3), 130.5 (1-C6H2Me3), 129.6 (3,5-C6H2Me3), 124.1
i
i
i
(4-C6H3 Pr2), 123.6 (3-C6H3 Pr2), 123.4 (5-C6H3 Pr2), 65.7 (OCH2),
28.8 (CHMe2), 27.0 (CHMe2), 22.1 (CHMe2), 21.6 (2,6-C6H2Me3),
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

R. Green et al. / Polyhedron xxx (2016) xxx–xxx
9
cmꢀ1): 2020 (m), 2003 (m), 1961 (sh), 1930 (s), 1866 (s), 1791
(sh), 1609 (m), 1567 (m), 1433 (s), 1412 (s), 1311 (m), 1228 (m),
1178 (m), 1078 (m), 1052 (m), 962 (w), 945 (w), 934 (w), 872
(m), 861 (m), 852 (m), 815 (m), 800 (m), 779 (m), 760 (s), 698
20.6 (4-C6H2Me3), 13.6 (OCH2Me). IR (NaCl plates, Nujol mull,
cmꢀ1): 1437 (s), 1412 (sh), 1392 (s), 1319 (m), 1231 (w), 1189
(w), 1177 (m), 1051 (m), 996 (m), 967 (m), 949 (w), 936 (w), 889
(w), 853 (m), 834 (w), 779 (m), 762 (m), 754 (m), 672 (w), 659
(w). Anal. found (calcd for C76H110Mg2Br2N4O2): C, 68.92 (69.15);
H, 8.52 (8.40); N, 4.28 (4.24)%.
(w), 664 (m). IR (NaCl cell, toluene, m
(CO), cmꢀ1): 2017 (s), 1925
(m). It was not possible to obtain a satisfactory elemental analysis
for 15.
4.7. {MesC(NDipp)2}Mg{Co(CO)3(PCy3)}(THF) (14)
4.9. MesNCNMes (16)
To [{MesC(NDipp)2}Mg(l-Br)(OEt2)]2 (13, 500 mg, 0.379 mmol)
To
a
stirring solution of MesN(H)C(S)N(H)Mes (12.5 g,
and K[Co(CO)3(PCy3)](THF)2 (460 mg, 0.757 mmol) was added THF
(20 mL). The brown solution was stirred for 18 h before removal of
volatiles under reduced pressure. The grey solid was extracted with
pentane (3 ꢁ 10 mL) and volatiles removed under reduced pres-
sure. Drying in vacuo afforded 14 as a grey solid. Yield: 298 mg
40.0 mmol) and NEt3 (11.2 mL, 80.0 mmol) in ethyl acetate
(300 mL) was added I2 (10.2 g, 40.0 mmol) in portions over
30 min. The mixture was stirred for 2 h at room temperature then
filtered to give a brown solution. Volatiles were removed under
reduced pressure to give a brown solid. The solid was extracted
with pentane (4 ꢁ 50 mL), filtered through a silica plug and the
resultant brown solution added to activated Cu (6.10 g, 96.0 mmol).
The mixture was stirred for 16 h at room temperature to give a
black suspension. The suspension was filtered through silica to give
a colourless solution. Volatiles were removed under reduced pres-
sure and the resultant solid was dried in vacuo to afford 16 as a
colourless crystalline solid. Yield: 6.97 g (63%). The 1H NMR spec-
trum was consistent with that reported by Cowley et al. [24].
(39%). 1H NMR (C6D6, 400.2 MHz): d 7.03 (6 H, s, 4- & 3,5-C6H3 Pr3),
i
6.40 (1 H, s, 3-C6H2Me3), 6.36 (1 H, s, 5-C6H2Me3), 4.16 (4 H, s,
OCH2), 3.42 (4 H, br s, CHMe2) 2.38 (3 H, s, 2-C6H2Me3), 2.02 (3 H,
m, 1-C6H11), 1.95 (3 H, s, 6-C6H2Me3), 1.83 (3 H, s, 4-C6H2Me3),
1.78 (6 H, m, 4-C6H11), 1.62 (12 H, m, 2,6-C6H11), 1.51 (12 H, s,
CHMe2), 1.35 (s, 4 H, OCH2CH2), 1.26 (12 H, s, CHMe2), 1.21 (12 H,
m, 3,5-C6H11). 13C{1H} NMR (C6D6, 100.6 MHz): d 209.4 (s, CO),
i
i
174.7 (s, CN2), 143.3 (s, 2-C6H3 Pr2), 142.5 (s, 6-C6H3 Pr2), 138.3 (s,
2-C6H2Me3), 137.6 (s, 6-C6H2Me3), 137.5 (s, 4-C6H2Me3), 131.0
(s, 1-C6H2Me3), 130.0 (s, 3-C6H2Me3), 129.3 (s, 5-C6H2Me3), 127.9
4.10. [Mg{MesC(NMes)2}(l-Br)(OEt2)]2 (17)
i
i
i
To a stirring solution of MesMgBr in Et2O (43.0 mL, 0.3 M,
12.9 mmol) was added a solution of MesNCNMes (16, 3.48 g,
12.5 mmol) in Et2O (30 mL) dropwise. The solution was stirred
for 18 h to give a white precipitate. The solid was isolated by filtra-
tion and washed with cold Et2O (2 ꢁ 20 mL, ꢀ78 °C) before drying
in vacuo to afford 17 as a white solid. Yield: 6.66 g (93%). 1H NMR
(s, 1-C6H3 Pr2), 123.9 (s, 4-C6H3 Pr2), 123.7 (s, 3-C6H3 Pr2), 123.6
(s, 5-C6H3 Pr2), 71.0 (s, OCH2), 37.7 (d, 1J = 17.3 Hz, 1-C6H11), 30.3
i
(s, 2,6-C6H11), 28.9 (s, CHMe2), 28.5 (s, CHMe2) 28.1 (d,
3J = 10.3 Hz, 3,5-C6H11), 26.9 (s, 4-C6H11), 25.0 (OCH2CH2), 23.8
(2-C6H2Me3), 22.7 (6-C6H2Me3), 20.6 (4-C6H2Me3). 31P{1H} (C6D6,
162.0 MHz): d 68.6 (s). IR (NaCl plates, Nujol mull, cmꢀ1): 3827
(w), 3747 (w), 2040 (w), 1965 (s), 1873 (s), 1612 (m), 1586 (w),
1569 (w), 1433 (s), 1413 (m), 1316 (m), 1230 (w), 1198 (w), 1174
(m), 1079 (m), 1041 (m), 963 (w), 947 (w), 935 (w), 916 (w), 875
(m), 851 (m), 777 (m), 758 (m), 700 (w), 659 (w), 585 (m), 562
(THF-d8, 400.2 MHz): d 6.54 (8 H, s, N-C6H2Me3), 6.42 (4 H, s,
C-C6H2Me3), 3.38 (8 H, quart, 3J = 7.0 Hz, OCH2), 2.18 (24 H,
s, N-(2,6-C6H2Me3)), 2.09 (12 H, s, C-(2,6-C6H2Me3)), 2.06 (12 H,
s, N-(4-C6H2Me3)), 2.02 (6 H, s, C-(4-C6H2Me3)), 1.11 (12 H, t,
3J = 7.0 Hz, OCH2Me). 13C{1H} NMR (C6D6, 100.6 MHz): d 173.5
(CN2), 144.9 (N-(2,6-C6H2)), 137.9 (C-(2,6-C6H2)), 137.7
(C-(4-C6H2)), 134.7 (C-(1-C6H2)), 132.8 (N-(1-C6H2)), 130.7
(N-(4-C6H2)), 129.5 (N-(3,5-C6H2)), 129.3 (C-(3,5-C6H2)), 66.5
(m). IR (NaCl cell, toluene, m
(CO), cmꢀ1): 1968 (m), 1891 (s), 1840
(w). Anal. found (calcd for C59H86CoMgN2O4P): C, 70.54 (70.75);
H, 8.50 (8.66); N, 2.88 (2.80)%.
(OCH2), 23.3 (C-(2,6-C6H2Me3)), 21.3 (N-(2,6-C6H2Me3)), 21.0
4.8. {MesC(NDipp)2}MgFp(THF) (15)
(C-(4-C6H2Me3)), 20.9 (N-(4-C6H2Me3)), 15.8 (OCH2Me). IR (NaCl
plates, Nujol mull, cmꢀ1): 1733 (w), 1396 (s), 1205 (m), 1181
(w), 1148 (m), 1086 (m), 1048 (m), 968 (w), 936 (w), 919 (w),
909 (w), 853 (s), 834 (w), 787 (m), 749 (w), 740 (w), 659 (w). It
was not possible to obtain a satisfactory elemental analysis for 17.
To a stirring solution of {MesC(NDipp)2}Mg(l-Br)(OEt2) (13,
1.00 g, 1.51 mmol) in THF (10 mL) was added a solution of K[Fp]
(326 mg, 1.51 mmol) in THF (10 mL) dropwise. The reaction mix-
ture was stirred for 2 h before removal of volatiles under reduced
pressure. The dark brown solid was extracted with benzene
(2 ꢁ 10 mL) and volatiles removed under reduced pressure. The
solid was triturated with pentane (5 mL) before removal of vola-
tiles under reduced pressure and drying in vacuo to afford 15 as
4.11. {MesC(NMes)2}Mg{Co(CO)3(PCy3)}(THF) (18)
To a stirring solution of [{MesC(NMes)2}Mg(l-Br)(OEt2)]2 (17,
a
light brown solid. Yield: 0.89 g (74%). 1H NMR (C6D6,
500 mg, 0.434 mmol) in THF (10 mL) was added a solution of K
[Co(CO)3(PCy3)](THF)2 (527 mg, 0.868 mmol) in THF (10 mL) drop-
wise. The reaction mixture was stirred for 2 h before removal of
volatiles under reduced pressure. The brown residue was extracted
with benzene (2 ꢁ 10 mL), volatiles were removed under reduced
pressure and the solid dried in vacuo to afford 18 as a pale brown
solid. Yield: 668 mg (84%). 1H NMR (C6D6, 400.2 MHz): d 6.71 (4 H,
s, N-(3,5-C6H2)), 6.42 (2 H, s, C-(3,5-C6H2)), 3.98 (4 H, s, OCH2), 2.46
i
400.2 MHz): d 7.01 (6 H, s, C6H3 Pr2), 6.36 (2 H, s, C6H2Me3), 4.51
(5 H, s, Cp), 4.00 (4 H, s, OCH2), 2.96 (2 H, br s, CHMe2), 2.12 (3
H, s, 2-C6H2Me3), 1.96 (3 H, s, 6-C6H2Me3), 1.87 (3 H, s,
4-C6H2Me3), 1.50 (12 H, br s, CHMe2), 1.26 (4 H, s, OCH2CH2). 13C
{1H} NMR (C6D6, 100.6 MHz): d 221.7 (CO), 173.6 (CN2), 142.4
i
(2,6-C6H3 Pr2), 137.8 (2-C6H2Me3), 137.7 (4-C6H2Me3), 137.3
(6-C6H2Me3), 131.2 (1-C6H2Me3), 130.0 (3-C6H2Me3), 129.8
(12 H, s, N-(2,6-C6H2Me3), 2.26 (6 H, s, C-(2,6-C6H2Me3), 2.15 (12 H,
br s, 2,6-C6H11), 2.06 (6 H, s, N-(4-C6H2Me3), 2.01 (3 H, br s,
1-C6H11), 1.86 (3 H, s, C-(4-C6H2Me3), 1.77 (12 H, br s, 3,5-C6H11),
i
i
(5-C6H2Me3), 128.6 (1-C6H3 Pr2), 124.0 (3-C6H3 Pr2), 123.8
i
i
(4-C6H3 Pr2), 123.6 (5-C6H3 Pr2), 78.7 (Cp), 71.0 (OCH2CH2), 28.9
(CHMe2), 27.0 (CHMe2), 25.2 (OCH2CH2), 23.6 (CHMe2), 22.8
(2,6-C6H2Me3), 20.6 (4-C6H2Me3). IR (NaCl plates, Nujol mull,
1.62 (12 H, br s, 4-C6H11), 1.32 (4 H, br s, OCH2CH2). 13C{1H}
NMR (C6D6, 100.6 MHz): d 211.1 (s, CO), 172.7 (CN2), 143.3
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

10
R. Green et al. / Polyhedron xxx (2016) xxx–xxx
(s, N-(2,6-C6H2)), 138.0 (s, C-(4-C6H2)), 137.3 (s, C-(1-C6H2)), 133.4
(s, C-(2,6-C6H2)), 131.5 (s, N-(4-C6H2)), 130.8 (s, N-(1-C6H2)), 129.9
(s, N-(3,5-C6H2)), 129.3 (s, C-(3,5-C6H2)), 70.0 (s, OCH2), 37.5
(d, 1J = 16.6 Hz, 1-C6H11), 30.4 (s, 2,6-C6H11), 28.2 (d, 3J = 10.2 Hz,
4.14. {Me2NC(NDipp)2}MgI(OEt2) (21)
To a stirring solution of MeMgI in Et2O (11.64 mL, 0.4 M,
4.91 mmol) was added a solution of Me2NC(NDipp)(NHDipp) (20,
2.00 g, 4.91 mmol) in Et2O (10 mL) dropwise at ꢀ20 °C. The
colourless solution was allowed to warm to room temperature
and stirred for a further 2 h. Volatiles were removed under reduced
pressure to give a white solid, which was washed with hexane
(3 ꢁ 5 mL) and dried in vacuo to afford 21 as a white solid. Yield:
2.94 g (95%). Diffraction-quality crystals were grown from an
Et2O solution at room temperature. 1H NMR (C6D6, 400.2 MHz): d
7.20 (2 H, br m, 4-C6H3), 7.14 (4 H, br m, 3,5-C6H3), 3.71 (4 H, sept,
3J = 6.8 Hz, CHMe2), 3.34 (4 H, q, 3J = 7.0 Hz, OCH2), 2.14 (6 H, s,
NMe2), 1.38 (12 H, d, 3J = 6.8 Hz, CHMe2), 1.31 (12 H, d,
3J = 6.8 Hz, CHMe2), 0.93 (6 H, t, 3J = 7.0 Hz, OCH2Me). 13C{1H}
NMR (C6D6, 101.6 MHz): d 167.0 (CNMe2), 143.4 (1-C6H3), 142.9
(2,6-C6H3), 123.8 (3,5-C6H3), 123.6 (4-C6H3), 66.9 (OCH2), 39.6
(NMe2), 27.9 (CHMe2), 26.2 (CHMe2), 23.7 (CHMe2), 14.1
3,5-C6H11), 27.0 (s, 4-C6H11), 25.3 (s, OCH2CH2), 22.0 (s, C-(2,
6-C6H2Me)), 20.8 (s, C-(4-C6H2Me)), 20.7 (s, N-(4-C6H2Me)), 20.5
(s, N-(2,6-C6H2Me)). 31P{1H} (C6D6, 162.0 MHz): d 70.0 (s). IR (NaCl
plates, Nujol mull, cmꢀ1): 2040 (w), 1964 (sh), 1937 (s), 1885 (sh),
1865 (s), 1784 (w), 1720 (s), 1569 (w), 1425 (s), 1396 (s), 1207 (m),
1172 (w), 1148 (w), 972 (w), 919 (w), 886 (m), 851 (s), 818 (w),
741 (m), 675 (w). IR (NaCl cell, toluene,
1910 (m), 1890 (m), 1836 (m), 1755 (m). Anal. found (calcd for
53H73CoMgN2O4P): C, 69.53 (69.39); H, 8.18 (8.13); N, 2.99
m
(CO), cmꢀ1): 1970 (m),
C
(3.05)%.
4.12. {MesC(NMes)2}MgFp(THF) (19)
To a stirring solution of [{MesC(NMes)2}Mg(l-Br)(OEt2)]2 (17,
300 mg, 0.260 mmol) in THF (15 mL) was added a solution of K
[Fp] (113 mg, 0.520 mmol) in THF (10 mL) dropwise. The reaction
mixture was stirred for 3 h before removal of volatiles under
reduced pressure. The dark brown solid was extracted with THF
(2 ꢁ 10 mL) and filtered before removal of volatiles under reduced
pressure. The solid was triturated with pentane before removal of
volatiles under reduced pressure and drying in vacuo to afford 19
as a light brown solid. Yield: 236 mg (68%). 1H NMR (THF-d8,
(OCH2Me). IR (NaCl plates, Nujol mull, cmꢀ1): 1522 (s), 1315 (m),
1250 (m), 1203 (m), 1100 (m), 1042 (s), 934 (w), 835 (w), 904
(m), 835 (w), 771 (s). Anal. found (calcd. for C31H50IMgN3O): C,
58.79 (58.92); H, 7.89 (7.98); N, 6.52 (6.65)%.
4.15. [{Me2NC(NDipp)2}MgFp]2 (22)
To a stirring suspension of K[Fp] (171 mg, 0.791 mmol) in C6H6
400.2 MHz): d 6.61 (4 H, s, N-C6H2Me3), 6.52 (2 H, s, C-C6H2Me3),
(10 mL) was added
a solution of {Me2NC(NDipp)2}MgI(Et2O)
4.40 (5 H, s, Cp), 2.10 (6 H, s, C-(2,6-C6H2Me3)), 2.09 (15 H, s,
(21, 500 mg, 0.791 mmol) in C6H6 (10 mL) dropwise at room tem-
perature. The mixture was stirred for 1 h at room temperature then
filtered. Volatiles were removed from the filtrate under reduced
pressure to give a red solid, which was washed with cold hexane
(3 ꢁ 5 mL, ꢀ78 °C) and dried in vacuo to afford 22 as a yellow solid.
Yield: 308 mg (64%). Diffraction-quality crystals were grown from
a benzene solution at 5 °C. 1H NMR (C6D6, 400.2 MHz): d 7.10 (4 H,
br m, 4-C6H3), 6.81 (8 H, br m, 3,5-C6H3), 4.15 (10 H, s, Cp), 3.64 (8
N-(2,6-C6H2Me3) & C-(4-C6H2Me3)), 1.98 (6 H, s, N-(4-C6H2Me3)).
13C{1H} NMR (C6D6, 100.6 MHz): d 223.1 (CO), 172.1 (CN2), 143.9
(N-(2,6-C6H2)), 138.6 (C-(4-C6H2)), 137.8 (C-(2,6-C6H2)), 134.0
((C-(1-C6H2))), 131.4 (N-(1-C6H2)), 131.0 (N-(4-C6H2)), 130.0 (N-
(3,5-C6H2)), 129.7 (C-(3,5-C6H2)), 78.8 (Cp), 22.2 (N-(4-C6H2Me3)),
21.0 (C-(2,6-C6H2Me3)), 20.8 (N-(2,6-C6H2Me3) & C-(4-C6H2Me3)).
IR (NaCl plates, Nujol mull, cmꢀ1): 2019 (m), 1961 (sh), 1923 (s),
1858 (s), 1790 (sh), 1678 (w), 1610 (m), 1168 (w), 1147 (w), 969
(m), 955 (w), 935 (w), 920 (m), 852 (s), 676 (m), 634 (m), 606
H, br s, CHMe2), 2.12 (12 H, s, NMe2), 1.35 (24 H, d, 3J = 7.1 Hz,
CHMe2), 1.25 (24 H, d, 3J = 7.1 Hz, CHMe2). 13C{1H} NMR (C6D6,
(m), 592 (m). IR (NaCl cell, THF m
(CO), cmꢀ1): 2013 (s), 1992 (sh),
101.6 MHz): d 166.0 (CNMe2), 144.0 (1-C6H3), 142.6 (2,6-C6H3),
123.8 (3,5-C6H3), 123.5 (4-C6H3), 80.5 (Cp), 39.5 (NMe2), 28.1
1950 (sh), 1921 (s), 1879 (sh), 1861 (s). It was not possible to
obtain a satisfactory elemental analysis for 19.
(CHMe2), 25.7 (CHMe2), 23.7 (CHMe2), (d (CO) not observed). IR
(NaCl plates, Nujol mull, cmꢀ1): 2020 (m), 1962 (s), 1944 (s),
1778 (s), 1626 (m), 1410 (w), 1018 (m), 800 (m), 770 (w). IR (NaCl
4.13. Me2NC(NDipp)(NHDipp) (20)
cell, toluene,
cell, THF,
(CO), cmꢀ1): 2014 (s), 1946 (m). Anal. found (calcd. for
68H90Fe2Mg2N6O4): C, 66.89 (67.18); H, 7.34 (7.46); N, 6.91
(6.76)%.
m
(CO), cmꢀ1): 2016 (s), 1921 (m), 1781 (m). IR (NaCl
To a stirring solution of LiNMe2 (0.561 g, 11.0 mmol) in THF
(10 mL) was added DippNCNDipp (12, 4.00 g, 11.0 mmol) over
5 min in THF (10 mL) at ꢀ78 °C. The colourless solution was
allowed to warm to room temperature then stirred for a further
2 h at room temperature, quenched with deionised water (10 mL)
and extracted into Et2O (3 ꢁ 10 mL). Volatiles were removed under
reduced pressure and the resultant white solid dried in vacuo to
afford 20. Yield: 4.13 g (92%). Diffraction-quality crystals were
grown from a hexane solution at room temperature. 1H NMR
(C6D6, 400.2 MHz): d 7.26 (2 H, app. d, 3J = 8.0 Hz, 4-C6H3), 7.00
(4 H, d, 3J = 7.0 Hz, 3,5-C6H3), 5.25 (1 H, s, NH), 3.45 (2 H, br m,
m
C
4.16. {Me2NC(NDipp)2}Mg{Co(CO)3(PCy3)}(OEt2) (23)
To a stirring suspension of K[Co(CO)3(PCy3)](THF)2 (480 mg,
0.791 mmol) in C6H6 (10 mL) was added a solution of {Me2NC
(NDipp)2}MgI(Et2O) (21, 500 mg, 0.791 mmol) in C6H6 (10 mL)
dropwise at room temperature. The mixture was stirred for 1 h
then filtered. Volatiles were removed from the filtrate under
reduced pressure and the resultant red solid (11) dried in vacuo.
Yield: 410 mg (56%). 1H NMR (C6D6, 400.2 MHz): d 7.20 (4 H, br
m, 3,5-C6H3), 7.11 (2 H, m, 3J = 7.4 Hz, 4-C6H3), 3.91 (8 H, br m,
CHMe2), 3.28 (2 H, br m, CHMe2), 2.48 (6 H, s, NMe2), 1.23 (24 H,
d, 3J = 6.9 Hz, CHMe2). 13C{1H} NMR (C6D6, 101.6 MHz): d 151.3
(CNMe2), 145.0 (1-C6H3), 140.1 (2,6-C6H3), 124.1 (3,5-C6H3),
123.5 (4-C6H3), 39.5 (NMe2), 29.0 (CHMe2), 28.8 (CHMe2), 25.0
(CHMe2), 24.7 (CHMe2), 23.4 (CHMe2), 22.5 (CHMe2). EI-HRMS:
CHMe2 & OCH2), 2.22 (6 H, s, NMe2), 1.97 (3 H, br m, 1-C6H11),
1.77 (6 H, br m, 4-C6H11), 1.56 (12 H, br m, 2,6-C6H11), 1.32 (27
H, br m, CHMe2 & OCH2Me), 1.21 (12 H, br m, 3,5-C6H11). 13C{1H}
m/z found (calc. for
407.3303 (407.3300). IR (NaCl plates, Nujol mull, cmꢀ1): 3391 (w,
(NH)), 1625 (s), 1260 (s), 1019 (m), 761 (w). Anal. found (calcd. for
27H41N3): C, 79.46 (79.55); H, 10.30 (10.14); N, 10.25 (10.31)%.
C
27H41N3, [Me2NC(NDipp)(NHDipp)]+)
NMR (C6D6, 101.6 MHz): d 209.4 (s, CO), 165.9 (s, CNMe2), 144.0
(s, 1-C6H3), 142.9 (s, 2,6-C6H3), 123.6 (s, 3,5-C6H3), 123.1
(s, 4-C6H3), 70.2 (s, OCH2), 39.9 (s, NMe2), 37.6 (d, 1J = 17.1 Hz,
m
C
Please cite this article in press as: R. Green et al., Polyhedron (2016), http://dx.doi.org/10.1016/j.poly.2016.02.028

R. Green et al. / Polyhedron xxx (2016) xxx–xxx
11
1-C6H11), 30.3 (s, 2,6-C6H11), 28.1 (d, 3J = 10.6 Hz, 3,5-C6H11), 28.0
reflections merged [35]. The structures were solved using SIR92
[36] or Superflip [37] and further refinements and all other crystal-
lographic calculations were performed using the CRYSTALS program
suite [38].
(s, CHMe2) 26.9 (s, 4-C6H11), 25.1 (s, OCH2Me), 24.0 (s, CHMe2).
31P{1H} NMR (C6D6, 162.0 MHz): d 69.2 (br s). IR (NaCl plates, Nujol
mull, cmꢀ1): 1960 (s), 1944 (s), 1879 (s), 1849 (s), 1517 (w), 769
(w). IR (NaCl cell, toluene, m
(CO), cmꢀ1): 1962 (s), 1858 (m), 1804
(m). It was not possible to obtain a satisfactory elemental analysis
for 23.
Acknowledgements
We thank the Leverhulme Trust for support and Corpus Christi
College, Oxford, for a Junior Research Fellowship for M.P. Blake.
4.17. K[Co(CO)3(PPh3)](THF) (24)
To a stirring K amalgam (121 mg, 3.08 mmol; 10 mL Hg) was
added a red suspension of [Co(CO)3(PPh3)]2 (500 mg, 0.617 mmol)
in THF (20 mL). The suspension was stirred over the amalgam for
16 h at room temperature to give a green-yellow solution, which
was filtered and volatiles removed under reduced pressure. The
resulting green-yellow solid was washed with pentane
(2 ꢁ 10 mL) and dried in vacuo to afford 24. Yield: 562 mg (88%).
Diffraction-quality crystals were grown from a THF solution at
room temperature. 1H NMR (THF-d8, 299.9 MHz): d 7.53 (6 H, s,
2,6-C6H3), 7.14 (9 H, s, 3,4,5-C6H3). 13C{1H} NMR (THF-d8,
75.5 MHz): d 144.0 (d, 1J = 27.1 Hz, 1-C6H3), 134.3 (d, 2J = 14.0 Hz,
2,6-C6H3), 128.3 (s, 4-C6H3), 127.9 (d, 3J = 8.7 Hz, 3,5-C6H3) (d(CO)
not observed). 31P{1H} NMR (THF-d8, 121.4 MHz): d 64.0 (br s). IR
(NaCl plates, Nujol mull, cmꢀ1): 1932 (s), 1855 (s), 1804 (s), 1583
(w), 1435 (s), 1305 (w), 1261 (w), 1177 (w), 1084 (m), 1056 (s),
1029 (m), 914 (w), 801 (w), 750 (m), 736 (m), 697 (s), 591 (m),
Appendix A. Supplementary data
CCDC 1448329–1448336 contains the supplementary crystallo-
graphic data for 9, 11, 14, 17, 20, 21, 22 and 24. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/re-
trieving.html, or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033;
or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.poly.2016.02.028.
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