Amidine and guanidine complexes of manganese and molybdenum. Crystal structures of (η-cyclopentadienyl)(N,N′-diphenylguamdino)-and (η-cyclopentadienyl)(N,N′,N″-triphenylguanidino)- dicarbonylmolybdenum(II)

Article abstract of DOI:10.1039/a704269h

Reactions of N,N′-diphenyl- and N,N′,A″-triphenylguanidine with [MnBr(CO)₅] gave cis-[MnBr{PhNC(NHR)-NHPh}(CO)₄], fac-[MnBr{PhNC(NHR)NHPh}₂(CO)₃] and [Mn{PhNC(NHR)NPh}(CO)₄] (R = H or Ph), the last complex being formed at higher temperatures with an excess of ligand. In reactions of these guanidines with [MoCl(η-C₅H₅)(CO)₃], HCl was eliminated and [Mo(η-C₅H₅){PhNC(NHR)NPh}(CO)₂] complexes (R = H or Ph) formed. Crystal structures of these molybdenum complexes have been determined, revealing symmetrically chelating co-ordination of the guanidino ligands (in close semblance of corresponding amidino-complexes) with the four-membered metallacycle planar for R = Ph but unusually (by 21°) folded for R = H due to hydrogen bonding of an uncommon type. Reaction of lithio-N,N′-di-p-tolylbenzamidine with [Mo(′-C₇H₇)-(CO)₃]BF₄ yielded [Mo{η-C₇H₇N(p-MeC₆H ₄)C(Ph)NC₆H₄Me-p}(CO)₃], consistent with nucleophilic attack at the ring, followed by nitrogen co-ordination at the metal by a pendant amidine group.

Full text of DOI:10.1039/a704269h

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Amidine and guanidine complexes of manganese and molybdenum.
Crystal structures of (ç-cyclopentadienyl)(N,NЈ-diphenylguanidino)-
and (ç-cyclopentadienyl)(N,NЈ,NЉ-triphenylguanidino)-
dicarbonylmolybdenum(II)
José R. da S. Maia, Pauline A. Gazard, Melvyn Kilner,* Andrei S. Batsanov and
Judith A. K. Howard
Department of Chemistry, University of Durham, South Road, Durham, UK DH1 3LE
Reactions of N,NЈ-diphenyl- and N,NЈ,NЉ-triphenylguanidine with [MnBr(CO)5] gave cis-[MnBr{PhNC(NHR)-
NHPh}(CO)4], fac-[MnBr{PhNC(NHR)NHPh}2(CO)3] and [Mn{PhNC(NHR)NPh}(CO)4] (R = H or Ph), the
last complex being formed at higher temperatures with an excess of ligand. In reactions of these guanidines
with [MoCl(η-C5H5)(CO)3], HCl was eliminated and [Mo(η-C5H5){PhNC(NHR)NPh}(CO)2] complexes
(R = H or Ph) formed. Crystal structures of these molybdenum complexes have been determined, revealing
symmetrically chelating co-ordination of the guanidino ligands (in close semblance of corresponding amidino-
complexes) with the four-membered metallacycle planar for R = Ph but unusually (by 21Њ) folded for R = H due
to hydrogen bonding of an uncommon type. Reaction of lithio-N,NЈ-di-p-tolylbenzamidine with [Mo(η-C7H7)-
(CO)3]BF4 yielded [Mo{η-C7H7N(p-MeC6H4)C(Ph)NC6H4Me-p}(CO)3], consistent with nucleophilic attack at the
ring, followed by nitrogen co-ordination at the metal by a pendant amidine group.
Amidines RNHC(RЈ)᎐NR and their deprotonated anions dis-
ing the proton on co-ordination, especially with molybdenum.
In the present work we studied the co-ordinating abilities of
aryl-substituted guanidines in similar reactions with 1 and 2,
and extended the studies of amidine systems as well.
᎐
play a great variety of modes of co-ordination with transition
metals1 and interesting isoelectronic and isostructural relation-
ships with other pseudo-allylic ligands, namely triazines, carb-
oxylates, dithiocarboxylates, dithiocarbamates, dithiophos-
phates and diselenophosphonates.2 Guanidines, i.e. amidine
derivatives with an amino-substituent RЈ, seem even more
promising, being stronger electron donors than amidines3 and
apparently possessing all the co-ordination possibilities of the
latter plus another potential co-ordination centre in the form of
the third nitrogen atom. On the other hand, it was supposed4
that electron delocalisation over the N3C moiety should actu-
ally impair the co-ordinating ability of the nitrogen atoms by
making their lone pairs more diffuse. The first complexes of
transition metals (Co, Cu, Zn, Pd and Ni) with 1,1,3,3-
tetramethylguanidine (tmg) were reported long ago5 and the
monodentate two-electron co-ordination of tmg through the
imine nitrogen atom was postulated on the basis of the IR spec-
tra. Such co-ordination was later confirmed by X-ray diffrac-
tion studies in the complexes of Tc with tmg4 and of Pt with
Results and Discussion
(a) Manganese carbonyl complexes
N,NЈ-Diphenyl- and N,NЈ,NЉ-triphenyl-guanidine react with
complex 1 in a manner typical for monodentate two-electron
donors,11 displacing one and then another carbonyl group to
form cis-[MnBr{PhNC(NHR)NHPh}(CO)4] 5 and fac-[MnBr-
{PhNC(NHR)NHPh}2(CO)3] 6, where R = H or Ph. We sup-
pose that the guanidine ligands are co-ordinated via the imino
nitrogen atom, as has been observed earlier.4,6 The stereo-
chemical configurations of 5 and 6 were assigned on the basis
of the intensities and pattern of the ν(CO) stretching frequen-
cies (see Table 1) and there was no evidence for isomerisation of
the fac into the mer isomer of 6, as occurs for bulkier ligands
such as triphenylphosphine.16 The ν(CN) stretching frequencies
of the guanidine ligands remain virtually the same as those for
the free guanidines and their complexes with other Lewis acids.
Thus, ν(CN) in Nujol are 1636 cmϪ1 for (PhNH)2CNPh, 1620–
1625 for complexes 5 and 6 and 1638 cmϪ1 for (PhNH)2-
CNPhؒBF3.
When a two-fold excess of the guanidine is used in the reac-
tion with complex 1 in toluene the guanidine acts also as a
proton base, precipitating its hydrobromide salt and leaving
[Mn{PhNC(NHR)NPh}(CO)4] (R = H 7a or Ph 7b) in solu-
tion. The same reaction occurs during spontaneous decom-
position of 6 in solutions. The guanidinium bromide released
thereupon is probably the reason why the solutions of 6 in polar
solvents behave as 1:1 electrolytes, e.g. with the molar conduct-
ivity of 91 ohmϪ1 cm2 molϪ1 in nitromethane [cf. 89 ohmϪ1 cm2
molϪ1 for PhNC(NHPh)2ؒHBr]. Complex 7b was also syn-
thesized in the metathetical reaction of 1 with lithio-N,NЈ,NЉ-
triphenylguanidine in tetrahydrofuran (thf) solution, the
presence or absence of Me2NCH2CH2NMe2 being of no con-
sequence to the outcome of the reaction. However, attempts to
HN᎐C(NEt ) .6 Of the substituted guanidines, cyanoguanidine
᎐
2
2
recently became popular as a ligand, capable of terminal, bridg-
ing and chelating co-ordination.7 Guanidino, i.e. deprotonated
guanidine, ligand can give more sophisticated modes of co-
ordination, similar to those of amidines.1 In particular, a bridg-
ing HNC(NH2)NH anion8 and a chelating PhNC(᎐NPh)NPh
᎐
dianion9 were observed in structurally characterised platinum
complexes.
We have found earlier10 that amidines RNHC(RЈ)᎐NR (R =
᎐
Ph or p-tolyl; RЈ = H, Me or Ph) and their lithio-derivatives
RN(Li)C(RЈ)᎐NR react with [MnBr(CO) ] 1 and [MoCl(η-
᎐
5
C5H5)(CO)3] 2 to form complexes of the [Mn{CON(R)C(RЈ)N-
R}(CO)4], [Mn{RNC(RЈ)NR}(CO)4] 3, [Mo(η-C5H5){CON-
(R)C(RЈ)NR}(CO)2] and [Mo(η-C5H5){RNC(RЈ)NR}(CO)2] 4
types. The lithiated amidines attack a carbonyl ligand of both 1
and 2 to produce a carbamoyl group CON(R)C(RЈ)NR which
acts as a three-electron chelate ligand, its subsequent decarbon-
ylation yielding 310a or 4.10b,c Complex 4 can be also obtained
directly from RNHC(RЈ)᎐NR and 2, the amidine readily los-
᎐
J. Chem. Soc., Dalton Trans., 1997, Pages 4625–4630
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Table 1 ν(CO) Stretching frequencies of the prepared and related complexes
Complex
R
Form
ν (CO)/cmϪ1
Ref.
5a [MnBr{PhNC(NHR)NHPh}(CO)4]
5b
H
Ph
H
—
Ph
H
Ph
Me
Ph
—
—
—
—
H
Ph
—
Me
Ph
—
—
Nujol
Nujol
Nujol
CH2Cl2
Nujol
Hexane
Nujol
cyclo-C6H12
cyclo-C6H12
CHCl3
CCl4
C6H14
CHCl3
Nujol
2100m, 2030s, 2000s, 1960s
2099w, 2030s, 2001s, 1958s
2010s, 1920s, 1895s
2091w, 2013s, 1990s, 1950s
2012s, 1923s, 1898s
2092, 2011s, 1991s, 1949s
2093m, 2010s, 1990s, 1933s
2096w, 2017s, 1996s, 1955s
2093w, 2010s, 1995s, 1950s
2123w, 2055s, 1973s, 1950s
2100w, 2022s, 2017 (sh), 1972s
2092m, 2014s, 2000s, 1963s
2075w, 2010s, 1982s, 1933m
1942s, 1848s
1935s, 1830s
1915s, 1857s
1953s, 1859s
1970s, 1890s
1950s, 1864 (sh), 1852s
1925s, 1840s, 1800s
This work
This work
This work
This work
This work
This work
This work
10(a)
10(a)
12
13
14
6a [MnBr{PhNC(NHR)NHPh}2(CO)3]
6b
7a [Mn{PhNC(NHR)NPh}(CO)4]
7b
[Mn{PhNC(R)NPh}(CO)4]
[Mn(CF3COCHCOCF3)(CO)4]
[Mn(S2CPh)(CO)4]
[Mn(S2PEt2)(CO)4]
[Mn{S2C2(CN)2}(CO)4]Ϫ
8a [Mo(η-C5H5){PhNC(NHR)NPh}(CO)2]
8b
15
This work
This work
This work
10(c)
10(b)
10(b)
Nujol
Et2O
Toluene
CCl4
Nujol
[Mo(η-C5H5){PhNC(R)NPh}(CO)2]
10 [Mo{C7H7(p-MeC6H4)NC(Ph)NC6H4Me-p}(CO)3]
Nujol
This work
H
H
–
R
BF4
H
C6H4Me-p
+
H
N
Ph
N
LiR
thf
or
or
N
C6H4Me-p
(OC)3Mo
C6H4Me-p
Mo(CO)3
Mo(CO)3
Ph
C6H4Me-p
N
(OC)3Mo
10A
10B
H
H
R
H
H
R
etc.
Mo(CO)3H
R
R
(OC)3Mo
H(OC)3Mo
Mo(CO)3
Scheme 1 Supposed rearrangements of cycloheptatrienylamidino molybdenum complexes; R = p-MeC6H4NC(CHPh)NC6H4Me-p
prepare the same complex from 5b (R = Ph), using n-
butyllithium or triethylamine were unsuccessful, and only 6b,
the product of the reaction of 5b with additional free guani-
dine, was detected. The additional guanidine can arise only
from decomposition of a portion of the starting complex, 5b.
The guanidine and guanidino complexes are less stable in
solution towards decomposition and air oxidation than the
amidine and amidino complexes, but otherwise are similar to
the latter in their properties and IR spectra (see Table 1), which
suggest similar molecular structures. For 7, as for correspond-
ing amidino complexes, two structures are possible: mono-
nuclear with a chelating NCN moiety or binuclear with bridg-
ing ones. From the available evidence (mass spectral study being
unsuccessful) the structure cannot be assigned unequivocally
but is more likely to be mononuclear, as in related complexes, in
view of the similarity of the IR spectra (see Table 1).10a–c,12–15
both contain chelating three-electron guanidine ligands. The
course of the reaction, the structure, properties and IR spectra
(Table 1) of the products are similar to those observed for the
corresponding amidines.
(c) Cycloheptatriene molybdenum complexes
Lithio-N,NЈ-di-p-tolylbenzamidine reacts with [Mo(η-C7H7)-
(CO)3]BF4 9 in thf solution at Ϫ40 ЊC to produce a complex
having the formal composition [Mo{η-C7H7(p-MeC6H4)NC-
(Ph)NC6H4Me-p}(CO)3] 10. Thus, the amidine enters the com-
plex as the formally anionic amidino-group, while all three car-
bonyl ligands remain there in a facial arrangement, as indicated
by three strong ν(CO) stretching frequencies in the IR spectrum
of 10. These frequencies (1925s, 1840s, 1800s cmϪ1) are con-
siderably lower than for [Mo(η-C7H8)(CO)3] (1970s, 1910, 1860s
cmϪ1 in Nujol),17 as should be expected when a strong electron
donor, such as the amidine nitrogen atom, enters the co-
ordination sphere. The only possible explanation is that the
lithioamidine attacks the cycloheptatrienyl ring with one nitro-
gen atom and then co-ordinates to the metal atom with another,
in a strap-type structure (Scheme 1), while the cycloheptatrienyl
co-ordination switches from η6 to η4.
(b) Cyclopentadienyl molybdenum complexes
Guanidines PhNC(NHR)NHPh react smoothly with complex
2 to form [Mo(η-C5H5){PhNC(NHR)NPh}(CO)2] (R = H 8a
or Ph 8b), substitution of a carbonyl group by the amidine
being followed by elimination of HCl, captured by a second
amidine molecule as the amidinium chloride. The intermediate
complex, [MoCl(η-C5H5){PhNC(NHR)NHPh}(CO)2], was not
detected in the solution during the reaction. Compounds 8a
and 8b, characterised by single-crystal structures (see below),
1
The H NMR spectrum of complex 10 contains signals due
to aromatic protons (phenyl group) and C(sp2)-bound cyclo-
heptatrienyl protons [δ 7.25 (m), 7.1 (br m), 6.7 (t), 6.2 (dt) and
5.2 (dd)], an intense signal due to the methyl protons at δ 2.2,
4626
J. Chem. Soc., Dalton Trans., 1997, Pages 4625–4630

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Table 2 Selected bond distances (Å) and angles (Њ) in complexes 8a
and 8b
Complex 8a
Mo᎐N(1)
Mo᎐C(1)
Mo᎐C(2)
Mo᎐C(3)
Mo᎐C(4)
2.187(3)
1.966(4)
2.399(4)
2.317(4)
2.296(5)
Mo᎐Cp*
N(1)᎐C(5)
N(2)᎐C(5)
N(1)᎐C(6)
2.012(5)
1.336(4)
1.357(6)
1.414(4)
N(1)᎐Mo᎐C(1)
N(1)᎐Mo᎐Cp*
C(1)᎐Mo᎐Cp
N(1)᎐C(5)᎐N(1Ј)
N(1)᎐Mo᎐N(1Ј)
86.5(1)
116.0(2)
120.4(2)
108.6(4)
59.5(2)
C(1)᎐Mo᎐C(1Ј)
N(1)᎐Mo᎐C(1Ј)
Mo᎐N(1)᎐C(5)
N(1)᎐C(5)᎐N(2)
74.4(2)
122.6(1)
94.0(2)
125.7(2)
Complex 8b
Mo᎐N(1)
Mo᎐C(1)
Mo᎐C(3)
Mo᎐C(4)
Mo᎐C(5)
N(1)᎐C(8)
N(1)᎐C(9)
N(3)᎐C(21)
2.172(4)
1.952(4)
2.407(5)
2.322(5)
2.285(5)
1.327(6)
1.427(6)
1.413(5)
Mo᎐N(2)
Mo᎐C(2)
Mo᎐C(7)
Mo᎐C(6)
Mo᎐Cp*
N(2)᎐C(8)
N(2)᎐C(15)
N(3)᎐C(8)
2.191(4)
1.962(5)
2.394(5)
2.312(5)
2.016(5)
1.336(6)
1.418(6)
1.387(6)
N(1)᎐Mo᎐N(2)
N(1)᎐Mo᎐C(1)
N(1)᎐Mo᎐C(2)
N(1)᎐Mo᎐Cp
C(1)᎐Mo᎐Cp
N(1)᎐C(8)᎐N(2)
N(1)᎐C(8)᎐N(3)
59.8(1)
86.9(2)
121.9(2)
117.6(2)
120.0(2)
109.4(4)
123.0(4)
C(1)᎐Mo᎐C(2)
N(2)᎐Mo᎐C(2)
N(2)᎐Mo᎐C(1)
N(2)᎐Mo᎐Cp
C(2)᎐Mo᎐Cp
C(8)᎐N(3)᎐C(21)
N(2)᎐C(8)᎐N(3)
73.3(2)
84.7(2)
121.0(2)
118.6(2)
119.7(2)
127.3(4)
127.4(4)
Fig. 1 Molecular structure of complex 8a, showing the intermolecular
hydrogen bonds. Primed atoms are symmetry-related via plane m,
double primed via plane a
* Cp = Centroid of the cyclopentadienyl ring.
and away from the metal atom.20 Therefore the hypothetical
structure of the endo isomer 10B is much less favourable for
strong Mo᎐N (amidino) co-ordination than 10A, and in the exo
isomer such co-ordination is altogether impossible. Hence the
two isomers should exhibit very different ν(CO) stretching fre-
quencies, while only one set of three bands is observed.
Reported reactions of complex 9 with Lewis bases (Nu) are
of three types,21 i.e. nucleophilic attacks at the metal centre
(substituting one CO group for a Nu ligand), at the C7H7 ring
(forming a η6-C7H7Nu ligand), and at a carbonyl group [form-
ing a C(᎐O)Nu ligand]. Under mild conditions hard bases (neu-
᎐
tral or anionic) tend to react at the carbocyclic ring, and soft
bases at the metal.22 Thus the attack of the lithioamidine at the
ring is not unusual. Its mechanism may be similar to the reac-
tion of 9 with MeOϪ ion in methanol, which proceeds through
fast initial formation of an [Mo]᎐CO2Me group or an [Mo(η-
C7H8)(CO)3][OMe] ion pair to the irreversible formation of the
C7H7OMe ligand.23 Such reactions normally end with the
nucleophile attached to the non-co-ordinated (sp3) carbon atom
of the η6 ring. However, a 1,3-shift isomerisation process
(shown in Scheme 1), well known for linear-chain alkenes24 and
similar to some processes observed in fused aromatic π ligands
(e.g. ricochet inter-ring haptotropic rearrangements in dihydro-
[10]annulene complexes of tricarbonylchromium25), can change
the position of the saturated carbon atom in the ring, leaving
the amidino substituent at an sp2 carbon atom. In principle,
each position of the substituent with respect to the CH2 group
is accessible in this way, but from the NMR evidence it is the
3 isomer, shown in Scheme 1 (10A) which is formed. The
equilibrium process of this interconversion does not manifest
itself in the NMR spectrum, only one isomer being detected.
Fig. 2 Molecular structure of complex 8b, showing intermolecular
hydrogen bonds. Primed atoms are symmetry-related via an inversion
centre
and two one-proton singlets, δ 2.3 (s) and 2.0 (s). The last two
signals can be attributed respectively to the exo- and endo-
protons of the cycloheptatrienyl CH2 group, by analogy with
the assignments for [Co(η-C7H8)(PMe3)]BPh4 [δ 2.0 (br) and 2.3
(s)]18 and [Mo(η-C7H8)(CO)3] (δ 2.40 and 3.01, respectively).19
The structure most consistent with the available data is 10A
(Scheme 1), in which the amidino-bridge is bonded to one of
the sp2-carbon atoms of the cycloheptatrienyl ring. An altern-
ative explanation, the presence of equal amounts of [Mo(η-
C7H7R)(CO)3] isomers with the amidino (R) substituents in the
endo and exo positions at the sp3 carbon of the ring, seems
implausible. In a η6-cycloheptatriene ligand the sp3 carbon
atom is always bent out of the planar η6 co-ordinated moiety
(d) Crystal structures of complexes 8a and 8b
The molecular structures of complexes 8a and 8b are similar
(Figs. 1 and 2, Table 2). Molecule 8a is situated on a crystallo-
graphic mirror plane, passing through the Mo, C(4), C(5) and
N(2) atoms. In both complexes the Mo atoms lie at a distance
J. Chem. Soc., Dalton Trans., 1997, Pages 4625–4630
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of 2.01 Å from the cyclopentadienyl ring plane and are chelated
by the guanidino-ligand symmetrically (in 8a) or almost sym-
metrically (in 8b). The Mo᎐N distances are within the range
usual for amidino complexes of the [Mo(η-C5H5){RNC(RЈ)-
NR}(CO)2] type (2.15–2.20 Å).10d,26 The chelation in such com-
plexes is usually symmetrical: Mo᎐N distances never differ by
more than 0.04 Å (cf. by 0.02 Å in 8b) and often are crystal-
lographically equivalent.
(0.54 g, 1.96 mmol) was dissolved in toluene (40 cm3) and solid
N,NЈ,NЉ-triphenylguanidine (0.30 g, 1.04 mmol) added against
a counterflow of nitrogen. The mixture was heated at 45–50 ЊC
for 12 h, and produced a clear orange solution. On cooling to
Ϫ10 ЊC the excess of 1 separated and was filtered off. Removal
of solvent (20 cm3) in vacuo from the solution, addition of hex-
ane and cooling to Ϫ10 ЊC gave the product, [MnBr{PhNC(NH-
Ph)2{(CO)4] 5b, an air-stable yellow microcrystalline solid.
Yield: 0.36 g (65% based on the guanidine). M.p. 115–117 ЊC
(decomp.) (Found: C, 51.39; H, 3.11; Br, 14.43; N, 7.68.
C23H17BrMnN3O4 requires C, 51.71; H, 3.21; Br, 14.96; N,
7.87%).
(b) A mixture of complex 1 (0.52 g, 1.9 mmol) and N,NЈ,NЉ-
triphenylguanidine (1.09 g, 3.8 mmol), suspended in hexane (45
cm3), was heated for 12 h at 45–50 ЊC. Carbon monoxide was
evolved during the heating process. The yellow solid product,
[MnBr{PhNC(NHPh)2}2(CO)3] 6b, precipitated and was separ-
ated from the reaction mixture by filtration, washed with hex-
ane, and dried in vacuo. Yield: 1.12 g (75% based on 1) (Found:
C, 60.09; H, 4.26; Br, 10.02; N, 10.46. C41H34BrMnN6O3
requires C, 62.05; H, 4.32; Br, 10.07; N, 10.59%). M.p. 68–71 ЊC
(decomp).
(c) Complex 1 (0.50 g, 1.8 mmol) was added to a solution of
N,NЈ,NЉ-triphenylguanidine (1.04 g, 3.6 mmol) in toluene (30
cm3), and the mixture slowly warmed to 50 ЊC. Eventually 1
dissolved, and with further heating a pale solid separated. Heat-
ing was continued for 6 h, after which time the solid was filtered
off, washed with toluene and dried in vacuo. The white solid was
identified as [PhNHC(NHPh)2]Br by analysis and by com-
parison with an authentic sample (Found: C, 62.50; H, 4.89; N,
11.90. C19H18BrN3 requires C, 61.97; H, 4.93; N, 11.41%). The
filtrate was evaporated to dryness in vacuo, and the residue
extracted with dichloromethane (3 × 10 cm3). Evaporation of
the filtered extracts to small bulk and cooling to Ϫ10 ЊC yielded
yellow microcrystalline [Mn{PhNC(NHPh)NPh}(CO)4] 7b.
Yield: 0.64 g (77%), based on 1 (Found: C, 60.96; H, 3.91; N,
9.96. C23H16MnN3O4 requires C, 60.94; H, 3.56; N, 9.27%).
Both N(1) and N(1Ј) atoms of complex 8a form (symmetry-
related) hydrogen bonds with the N(2)H2 group of another
molecule, generated from the former one by a glide plane a
[N(1) ؒ ؒ ؒ N(2Љ) 3.131(6), N(2Љ)᎐H 0.83(3), H ؒ ؒ ؒ N(1) 2.50(4) Å,
N(2Љ)᎐H᎐N(1) 133(3)Њ], thus linking molecules into an infinite
chain parallel to the crystallographic x axis. Although the bond
is not particularly strong, it causes a substantial distortion of
the planar trigonal (sp2) bond geometry (characteristic for
other amidino complexes10d,26) of N(1), which is displaced by
0.15 Å from the MoC(5)C(6) plane in the direction of the
hydrogen bond. Consequently, the four-membered metal-
lacycle, which is usually nearly planar, is folded along the
N(1) ؒ ؒ ؒ N(1Ј) vector by 21Њ. Of 90 structurally characterised
amidino-complexes of various transition metals,27 only four
show folding angles (φ) as high as 15–19Њ, these being sterically
overcrowded complexes with Me3SiNC(Ph)NSiMe3 ligands.28
In all other complexes φ does not exceed 11Њ, and in the [Mo(η-
C5H5){RNC(RЈ)NR}(CO)2] complexes, it does not exceed 6Њ.
A three-co-ordinate sp2-nitrogen atom forming a hydrogen
bond is very uncommon. The Cambridge Structural Database27
contains only one example of such an atom, participating in co-
ordination with a metal and in multiple C᎐N bonds, to form
any intermolecular N ؒ ؒ ؒ H contact shorter than the sum of van
der Waals radii (2.66 Å),29 namely [V(η-C5H5)(p-MeC6H4-
NCHNC6H4Me-p)2]30 with a N ؒ ؒ ؒ H (tolyl) contact of 2.58 Å.
Characteristically, in the latter complex the nitrogen atom form-
ing the hydrogen bond is noticeably more pyramidalised than
the other (the sums of bond angles around them are 354.6 and
359.4Њ, respectively), and the metallacycle is folded by 11Њ.
In contrast, in complex 8b the Mo, C(8) and three nitrogen
atoms are essentially coplanar. The bulky phenyl substituent at
N(3) causes the twist of ca. 32Њ around the C(8)᎐N(3) bond,
interfering with the π delocalisation in the guanidino moiety.
Thus, the C(8)–N(3) bond in 8b is 0.03 Å longer than C(5)᎐N(2)
bond in 8a, while bond lengths in the chelating NCN moiety
remain the same.
Complex 1 with N,NЈ-diphenylguanidine. (a) The same
method, as described in (a) above, using complex 1 (0.45 g, 1.6
mmol) and PhNC(NH2)NHPh (0.34 g, 1.6 mmol) yielded
[MnBr{PhNC(NH2)NHPh}(CO)4] 5a, as a yellow microcrystal-
line solid. Yield: 0.61 g, 81% (Found: C, 44.46; H, 3.02; N, 8.90.
C17H13BrMnN3O4 requires C, 44.57; H, 2.86; N, 9.17%).
The amino group in complex 8b forms an intermolecular
hydrogen bond with one of the carbonyl groups [N(3) ؒ ؒ ؒ O(1Ј)
2.995(5), N(3)᎐H 0.88(6), H ؒ ؒ ؒ O(1Ј) 2.18(6) Å, N᎐H᎐O
154(5)Њ] of the molecule, symmetry-related to the former one
via the inversion centre (¹, ¹, ¹).
(b) The same reaction, as described in (b) above, using com-
plex 1 (0.17 g, 0.62 mmol) and PhNC(NH2)NHPh (0.27 g, 1.3
mmol) yielded [MnBr{PhNC(NH2)NHPh}2(CO)3] 6a, as a yel-
low solid. Yield: 0.31 g (48%) (Found: C, 54.02; H, 4.41; N,
12.80. C29H26BrMnN6O3 requires C, 54.31; H, 4.09; N, 13.10%).
(c) The same reaction, as described in (c) above, using com-
plex 1 (0.26 g, 0.95 mmol) and PhNC(NH2)NHPh (0.40 g, 1.9
mmol) gave [Mn{PhNC(NH2)NPh}(CO)4] 7a, a yellow solid.
Yield: 0.43 g (60%) (Found: C, 53.81; H, 3.53; N, 10.81.
C17H12MnN3O4 requires C, 54.13, H, 3.21; N, 11.14%).
¯ ¯ ¯
² ² ²
Experimental
N,NЈ-Di-p-tolylbenzamidine was prepared by a published pro-
cedure31 and recrystallised from toluene–hexane mixtures
before use. N,NЈ-Diphenylguanidine and N,NЈ,NЉ-triphenyl-
guanidine (Pfaltz and Bauer, Inc.) were recrystallised from
toluene–hexane. Other chemicals were supplied by Aldrich. The
complex [MnBr(CO)5] 1 was prepared from [Mn2(CO)10],
[MoCl(η-C5H5)(CO)3]32 2 and [Mo(η-C7H8)(CO)3]17 from [Mo-
(CO)6] using literature methods. Precautions were taken to
exclude air and moisture; solvents were pre-dried, and degassed
before use. Infrared spectra in the range 4000–250 cmϪ1 were
Complex 5b with triethylamine. Triethylamine (0.12 g, 0.5
mmol) was added to a solution of complex 5b (0.25 g, 0.46
mmol) in diethyl ether–chloroform (2:1), and the mixture
heated at 40 ЊC for 12 h. The reaction was monitored by IR
spectroscopy in the carbonyl stretching region. The changes
recorded were consistent with the formation of 6b rather than
of 7b. Removal of the solvent in vacuo yielded a yellow solid
which was recrystallised from hexane. Its IR spectrum was iden-
tical to that of 6b.
1
recorded using a Perkin-Elmer 1600 spectrometer, H NMR
spectra at 250 MHz using a Bruker AC 250 spectrometer, using
SiMe4 as an internal standard. The carbon, hydrogen, and
nitrogen contents of the complexes were determined using a
Carlo Erba EMA 1106 elemental analyser.
Irradiation of complex 6b in hexane. The solution was
exposed to sunlight, and the IR spectrum monitored over 2 d.
New carbonyl absorptions slowly formed as the yellow solution
became dark. After 2 d the solution was filtered through Celite
and cooled to Ϫ20 ЊC for 2 d, after which time a yellow solid
Reactions
Complex 1 with N,NЈ,NЉ-triphenylguanidine. (a) Complex 1
4628
J. Chem. Soc., Dalton Trans., 1997, Pages 4625–4630

View Article Online
separated. Infrared spectroscopy (Nujol) identified the product
as complex 7b: ν(CO) 2093m, 2010s, 1990s, 1933s; ν(NH)
Table 3 Crystal data for complexes 8a and 8b
3375w; ν(CN) 1601w cmϪ1
.
8a
8b
Formula
M
Colour
Crystal size/mm
T/K
Crystal system
Space group
a/Å
b/Å
c/Å
C20H17MoN3O2
427.3
Brown
0.3 × 0.35 × 0.45
150
Orthorhombic
Pnma (no. 62)
7.813(7)
C26H21MoN3O2
503.4
Brown
0.07 × 0.3 × 0.4
150
Monoclinic
P21/c (no. 14)
10.935(1)
9.706(1)
21.483(2)
97.76(1)
2259.3(4)
350, 10–20
4
1.48
6.1
Complex 1 with lithio-N,NЈ,NЉ-triphenylguanidine in the pres-
ence of N,N,NЈ,NЈ-tetramethyl-1,2-diaminoethane (tmen). n-
Butyllithium (2.3 mmol, 1.62  in hexane) was added to a
frozen solution of tmen (0.27 g, 2.3 mmol) in thf (5 cm3) at
Ϫ196 ЊC. The mixture was warmed to ambient temperature and
stirred for 0.5 h before being cooled again to Ϫ196 ЊC. A sol-
ution of PhNC(NHPh)2 (0.67 g, 2.3 mmol) in thf (20 cm3) was
added and the mixture warmed again to ambient temperature.
After stirring for 0.75 h, a solution of complex 1 (0.64 g, 2.3
mmol) in thf (20 cm3) was added dropwise to the lithioguan-
idine solution at Ϫ78 ЊC. After 2 h the reaction mixture was
slowly warmed to room temperature before the solvent was
removed in vacuo to yield a yellow gum. Extraction with diethyl
ether, followed by evaporation, was found to be the most suc-
cessful procedure for producing the solid product from the
gum. Recrystallation from light petroleum (b.p. 60–80 ЊC)
yielded 7b as a yellow solid. Yield: 0.47 g (45% based on 1)
(Found: C, 61.68; H, 4.54; N, 8.56. C23H16MnN3O4 requires C,
60.94; H, 3.56; N, 9.27%). The same product was obtained from
the same reactants in thf solution in the absence of tmen. Yield:
65%.
18.565(8)
12.025(7)
β/Њ
U/Å3
1744(2)
24, 11–14
4
1.63
7.7
50
1722, 1585, 0.006
Empiricala
0.92, 1.00
Setting reflections, θ/Њ
Z
Dc/g cmϪ3
µ/cmϪ1
Maximum 2θ/Њ
Data total, unique, Rint
Absorption correction
Minimum, maximum
transmission
Data observed, I > 2σ(I)
Number of variables
R(F, observed data)
wR(F2, all data)
Goodness of fit
Maximum, minimum
∆ρ/e ÅϪ3
60
17 826, 6115, 0.086
Semiempiricalb
0.80, 0.95
1387
128
0.032
0.081
1.15
4066
373
0.061
0.135
1.17
Complex 5b with n-butyllithium. The complex (0.24 g, 0.44
mmol), dissolved in monoglyme (ethylene glycol dimethyl ether)
(15 cm3), was cooled to Ϫ196 ЊC and n-butyllithium (0.43 mmol,
1.31  in hexane) added. The mixture was allowed to warm to
ambient temperature and stirred for 1.5 h. The solution dark-
ened to deep orange-red. Removal of the solvent in vacuo, fol-
lowed by extraction of the yellow residue into toluene (10 cm3),
produced a yellow solution, which after adjustment of the vol-
ume of solution in vacuo, addition of hexane and cooling to
Ϫ10 ЊC yielded a small amount of a yellow solid, which IR spec-
troscopy showed to contain 6b and not the target complex 7b.
0.47, Ϫ0.81
0.82, Ϫ0.99
a On 108 ψ scans of three reflections (TEXSAN software34). b On Laue
equivalents (SHELXTL software).
cm3) was transferred by syringe onto solid complex 9 (0.24 g,
0.67 mmol) at Ϫ40 ЊC. The mixture was allowed to warm and
was stirred at ambient temperature for 2.5 h. Removal of the
solvent in vacuo to small bulk (ca. 2 cm3) and the addition of
light petroleum (b.p. 60–80 ЊC, 30 cm3) caused a white precipi-
tate to separate. Filtration and cooling the solution to Ϫ10 ЊC
gave a yellow solid which was filtered off. From the filtrate,
cooling and addition of further light petroleum gave an orange-
yellow solid of [Mo{η-C7H7(p-MeC6H4)NC(Ph)NC6H4Me-p}-
(CO)3] 10. Yield: 0.16 g, 45% based on 9 (Found: C, 64.9; H,
4.69; N, 4.68. C31H26MoN2O3 requires C, 65.27; H, 4.59; N,
Tricarbonylchloro(ç-cyclopentadienyl)molybdenum(II) 2 with
N,NЈ,NЉ-triphenylguanidine. The guanidine (1.40 g, 4.9 mmol)
in diethyl ether (10 cm3) was added dropwise to a solution of
complex 2 (0.68 g, 2.4 mmol) in diethyl ether (10 cm3) at 35–
40 ЊC, and the mixture heated at the reflux temperature for 1 h.
After cooling and standing at room temperature, the solution
was decanted from the white solid (N,NЈ,NЉ-triphenylguanidine
hydrochloride), and filtered through a column of Celite 521.
The red-wine coloured filtrate was evaporated to dryness in
vacuo, and the red solid crystallised from a toluene–hexane mix-
ture to yield dark red crystals of [Mo(η-C5H5){PhNC(NH-
Ph)NPh}(CO)2] 8b. Yield: 0.91 g (75% based on 2) (Found: C,
62.23; H, 4.31; Mo, 19.03; N, 8.16. C26H21MoN3O2 requires C,
62.03; H, 4.20; Mo, 19.06; N, 8.35%). 1H NMR (CDCl3): δ 5.53
(s, 5) and 6.91 (m, 15).
4.91%). IR (Nujol): ν(CO) 1925s, 1840s and 1800s cmϪ1
.
The corresponding N,NЈ-diphenylacetamidino complex was
prepared by a similar procedure using monoglyme as the solv-
ent. The product precipitated as a yellow solid during 24 h of
stirring at ambient temperature (Found: C, 59.7; H, 4.30; N,
5.92. C24H20MoN2O3 requires C, 60.01; H, 4.20; N, 5.83%).
The same reaction using lithio-N,NЈ-di-p-tolylformamidine
was also undertaken in monoglyme, but the product remained
in solution. Removal of the solvent in vacuo at ambient tem-
perature gave an orange gum, which was extracted with toluene.
The solution changed from orange to black, and filtration
through Celite 521 several times eventually gave an orange
solution which yielded [Mo(C7H8)(CO)3] in low yield. This
product was identified by analysis and IR spectroscopy, by
reference to an authentic sample (Found: C, 44.2; H, 2.61.
C10H8MoO3 requires C, 44.1; H, 2.96%).
Complex 2 with N,NЈ-diphenylguanidine. Complex 2 (0.50 g,
1.8 mmol), dissolved in toluene (20 cm3), was mixed with a
solution of PhNC(NH2)NHPh (0.77 g, 3.7 mmol) in toluene
(80 cm3) and the red reaction mixture heated to 50 ЊC for 7 h.
The solution remained clear but became orange-red. On cool-
ing a white precipitate of [(PhNH)2CNH2]Cl separated, and
was filtered off. The filtrate was evaporated to dryness in vacuo
until crystallisation was imminent, then the solution was cooled
to Ϫ10 ЊC. Red-brown crystals of [Mo(η-C5H5){PhNC(NH2)-
NPh}(CO)2] 8a formed, and were dried in vacuo. Yield: 0.59 g
(78% based on 2). M.p. 153 ЊC (decomp.) (Found: C, 56.13; H,
4.15; N, 9.86. C20H17MoN3O2 requires C, 56.22; H, 4.01; N,
9.83%). Mass spectrum: m/z 373, [P Ϫ 2CO]ϩ.
Complex 9 with lithio-N,NЈ-diphenylacetamidine in the pres-
ence of tmen. N,NЈ-Diphenylacetamidine (0.18 g, 0.9 mmol)
and tmen (0.20 g, 1.7 mmol) were dissolved in monoglyme (20
cm3), and the solution cooled to Ϫ196 ЊC. n-Butyllithium (0.9
mmol, 1.64  in hexane) was added by syringe, and the mixture
allowed to warm slowly to ambient temperature. After stirring
for 1 h at this temperature the pale yellow solution was trans-
ferred by syringe onto complex 9 (0.30 g, 0.8 mmol), cooled to
Ϫ196 ЊC. The reaction mixture was allowed to reach ambient
temperature slowly, changing from yellow to yellow-orange and
[Mo(ç-C7H7)(CO)3]BF4
9 with lithio-N,NЈ-di-p-tolylbenz-
amidine. A solution of the lithioamidine (0.67 mmol) in thf (15
J. Chem. Soc., Dalton Trans., 1997, Pages 4625–4630
4629

View Article Online
10 (a) T. Inglis, M. Kilner, T. Reynoldson and E. E. Robertson,
finally dark amber. After 2 h of stirring at ambient temperature
the solvent was removed in vacuo and the residue extracted with
toluene (30 cm3). Yellow-orange crystals of [Mo(CO)4(tmen)]
separated from the yellow-orange solution on reducing the vol-
ume of solvent and cooling to Ϫ10 ЊC. Yield: 0.16 g (60% based
on 9) (Found: C, 37.11; H, 5.18; N, 8.17. C10H16MoN2O4
requires C, 37.05; H, 4.97; N, 8.64%). Infrared spectra and anal-
ytical data were consistent with data for an authentic sample
prepared from [Mo(CO)6] and tmen.
J. Chem. Soc., Dalton Trans., 1975, 924; (b) T. Inglis and M. Kilner,
ibid., 930; (c) B. Gaylani and M. Kilner, J. Less-Common Met.,
1977, 54, 175; (d) B. Gaylani, M. Kilner, C. I. French, A. J. Pick and
S. C. Wallwork, Acta Crystallogr., Sect. C, 1991, 47, 257.
11 R. J. Angelici and F. Basolo, Inorg. Chem., 1963, 2, 728 and refs.
therein.
12 M. Kilner and A. Wojcicki, Inorg. Chem., 1965, 4, 591.
13 W. Heiber and M. Gscheidmeier, Chem. Ber., 1966, 99, 2312.
14 E. Lindner and K.-M. Matejcek, J. Organomet. Chem., 1970, 24, C57.
15 J. Locke and J. A. McCleverty, Chem. Commun., 1965, 102.
16 R. J. Angelici, F. Basolo and A. J. Poe, J. Am. Chem. Soc., 1963, 85,
2215; C. C. Addison and M. Kilner, J. Chem. Soc. A, 1968, 1539.
17 F. A. Cotton, J. A. McCleverty, J. E. White, R. B. King, A. F.
Fronzaglia and M. B. Bisnette, Inorg. Synth., 1990, 28, 45.
18 L. C. A. Carvalho, M. Dartiguenave and Y. Dartiguenave,
J. Organomet. Chem., 1989, 367, 187.
19 P. L. Pauson, G. H. Smith and J. H. Valentine, J. Chem. Soc. C, 1967,
1061.
20 F. J. Hadley, T. M. Gilbert and R. D. Rodgers, J. Organomet. Chem.,
1993, 455, 107.
21 E. E. Isaacs and W. A. G. Graham, J. Organomet. Chem., 1975, 90,
319.
22 A. Salzer, Inorg. Chim. Acta, 1976, 17, 221.
Crystallography
X-Ray single-crystal diffraction experiments were performed
for complex 8a on a Rigaku AFC6S four-circle diffractometer
(ω-scan mode with Lehmann–Larsen profile analysis) and for
8b on a Siemens SMART three-circle diffractometer with a
CCD area detector (full hemisphere of the reciprocal space
scanned by ω in frames of 0.3Њ), using graphite-mono-
-
chromated Mo-Kα radiation (λ = 0.710 73 Å) and a Cryo-
stream open-flow N2 gas cryostat. The structures were solved by
Patterson and Fourier methods and refined by full-matrix least
squares against F2 of all data, using SHELXTL software.33 The
largest residual peaks of electron density were found at ca. 1 Å
from the Mo atoms. Crystal data are given in Table 3.
CCDC reference number 186/740.
23 P. Powell, M. Stephens and K. H. Yassin, J. Organomet. Chem.,
1986, 301, 313.
24 J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke,
Principles and Applications of Organotransition Metal Chemistry,
Univ. Sci. Books, California, 1987.
25 Yu. F. Oprunenko, M. D. Reshetova, S. G. Malyugina, Yu. A.
Ustynyuk, N. A. Ustynyuk, A. S. Batsanov, A. I. Yanovsky and
Yu. T. Struchkov, Organometallics, 1994, 13, 2284.
Acknowledgements
26 M. W. Creswick and I. Bernal, Inorg. Chim. Acta, 1983, 74, 241;
M. Draux and I. Bernal, ibid., 1986, 114, 75.
27 F. H. Allen, J. E. Davis, J. J. Galloy, O. Johnson, O. Kennard, C. F.
Macrae, E. M. Mitchell, G. F. Mitchell, J, M. Smith and D. G.
Watson, J. Chem. Inf. Comput. Sci., 1991, 31, 187.
We wish to thank the Leverhulme Trust for a visiting fellowship
(A. S. B.), Conselho Nacional de Desenvolvimento Cientifico e
Tecnologico (Brazil) for a studentship (J. R. S. M.), and Ms.
Judith Magee for experimental assistance.
28 D. Fenske, E. Hartmann and K. Denicke, Z. Naturforsch., Teil B,
1988, 43, 1611; R. Gomez, R. Duchateau, A. N. Chernega,
A. Meetsma, E. T. Edelmann, J. H. Teuben and M. L. H. Green,
J. Chem. Soc., Dalton Trans., 1995, 217.
29 Yu. V. Zefirov and P. M. Zorkii, Russ. Chem. Rev., 1989, 58, 421.
30 F. A. Cotton and R. Poli, Inorg. Chim. Acta, 1988, 141, 91.
31 E. C. Taylor and W. A. Ehrhart, J. Org. Chem., 1963, 28, 1108.
32 R. B. King, Organometallic Syntheses, Wiley, New York, 1965.
33 G. M. Sheldrick, SHELXTL, Structure Determination Software
Programs, Version 5/VMS, Siemens Analytical X-Ray Instruments,
Madison, WI, 1995.
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4630
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