Bis(isodiazene) and related complexes of molybdenum(VI). Syntheses and structures of [Mo(OTf)2(NNPh2)2(py)2], [MoCl(OTf)(NNPh2){NC5H3(CH 2C(O)Ph2)2-2,6}]

Article abstract of DOI:10.1039/a903372f

Possible routes to [Mo(NNPh₂)₂R₂], where R = alkyl or aryl groups, have been investigated including the interaction of [MoCl₂(NNPh₂)₂(dme)] 1 (dme = 1,2-dimethoxyethane) with the standard alkylating agents LiR, RMgX, R₂Mg or R₂Zn under various conditions of solvent and temperature. There was, however, no evidence to suggest alkylation had taken place. Treatment of 1 with two equivalents of silver trifluoromethanesulfonate, silver triflate (AgOTf), in the presence of pyridine gave the golden-yellow bis(triflate) complex [Mo(OTf)₂(NNPh₂)₂(py)₂] 2 in good yield. In the presence of an excess of bipy (2,2′-bipyridine) the known dicationic species [Mo(NNPh₂)₂(bipy)₂]²⁺ was isolated as its PF₆^- salt. Attempts to replace triflate by alkyl groups in 2 were unsuccessful. A similar reaction of 1 with silver triflate in the presence of the bulky tridentate alkoxide 2,6-bis(2-hydroxy-2,2-diphenylethyl)pyridine (H₂L) led to loss of an NNPh₂ group (presumably as hydrazine) and formation of the green mono-isodiazene complex [MoCl(OTf)-(NNPh₂)(L)] 3. The compound [Mo(CH₂CMe₂Ph)₂(NBu^t)₂] underwent partial imido ligand exchange with an excess of 1,1-diphenylhydrazine hydrochloride to give the brown bis(isodiazene) chloro-bridged dimer [{MoCl(NNPh₂)₂-(μ-Cl)(NH₂Bu ^t)}₂] 4. A chloride substitution reaction of 1 with potassium tris(3,5-dimethylpyrazolyl)hydroborate, (KTp′) afforded the bis(isodiazene) complex [MoTp′Cl(NNPh₂)₂] 5. The crystal and molecular structures of 2-5 have been determined. The complexes all contain linear isodiazene groups with Mo-N distances in the range 1.755(6) to 1.768(7) A. In 2 the molybdenum(VI) centre has a pseudo octahedral geometry with axial pyridines and cis-triflate groups. In six-co-ordinate 3 the pyridinediolate ligand has a meridional donor atom arrangement with an equatorial isodiazene ligand. The binuclear compound 4 has slightly asymmetric chloro bridges coplanar with the terminal isodiazene ligands. Complex 5 is octahedral, having a facially co-ordinated Tp′ ligand and linear NNPh₂ ligands.

Full text of DOI:10.1039/a903372f

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Bis(isodiazene) and related complexes of molybdenum(VI).
Syntheses and structures of [Mo(OTf)2(NNPh2)2(py)2],
[MoCl(OTf)(NNPh2){NC5H3(CH2C(O)Ph2)2-2,6}],
[{MoCl(NNPh2)2(ꢀ-Cl)(NH2But)}2] and [MoTpЈCl(NNPh2)2]
[OTf = O3SCF3, TpЈ = tris(3,5-dimethylpyrazolyl)hydroborate]
Jonathan R. Dilworth,*a Vernon C. Gibson,*b Nicola Davies,a Carl Redshaw,b
Andrew P. Whiteb and David J. Williamsb
a Inorganic Chemistry Laboratory, South Parks Road, Oxford, UK OX1 3QR.
E-mail: Jon.Dilworth@chemistry.oxford.ac.uk
b Department of Chemistry, Imperial College, South Kensington, London, UK SW7 2AY.
E-mail: v.gibson@ic.ac.uk
Received 28th April 1999, Accepted 28th June 1999
Possible routes to [Mo(NNPh2)2R2], where R = alkyl or aryl groups, have been investigated including the interaction
of [MoCl2(NNPh2)2(dme)] 1 (dme = 1,2-dimethoxyethane) with the standard alkylating agents LiR, RMgX, R2Mg or
R2Zn under various conditions of solvent and temperature. There was, however, no evidence to suggest alkylation
had taken place. Treatment of 1 with two equivalents of silver trifluoromethanesulfonate, silver triflate (AgOTf), in
the presence of pyridine gave the golden-yellow bis(triflate) complex [Mo(OTf)2(NNPh2)2(py)2] 2 in good yield. In
the presence of an excess of bipy (2,2Ј-bipyridine) the known dicationic species [Mo(NNPh2)2(bipy)2]2ϩ was isolated
as its PF6Ϫ salt. Attempts to replace triflate by alkyl groups in 2 were unsuccessful. A similar reaction of 1 with silver
triflate in the presence of the bulky tridentate alkoxide 2,6-bis(2-hydroxy-2,2-diphenylethyl)pyridine (H2L) led to loss
of an NNPh2 group (presumably as hydrazine) and formation of the green mono-isodiazene complex [MoCl(OTf)-
(NNPh2)(L)] 3. The compound [Mo(CH2CMe2Ph)2(NBut)2] underwent partial imido ligand exchange with an excess
of 1,1-diphenylhydrazine hydrochloride to give the brown bis(isodiazene) chloro-bridged dimer [{MoCl(NNPh2)2-
(µ-Cl)(NH2But)}2] 4. A chloride substitution reaction of 1 with potassium tris(3,5-dimethylpyrazolyl)hydroborate,
(KTpЈ) afforded the bis(isodiazene) complex [MoTpЈCl(NNPh2)2] 5. The crystal and molecular structures of 2–5
have been determined. The complexes all contain linear isodiazene groups with Mo–N distances in the range 1.755(6)
to 1.768(7) Å. In 2 the molybdenum() centre has a pseudo octahedral geometry with axial pyridines and cis-triflate
groups. In six-co-ordinate 3 the pyridinediolate ligand has a meridional donor atom arrangement with an equatorial
isodiazene ligand. The binuclear compound 4 has slightly asymmetric chloro bridges coplanar with the terminal
isodiazene ligands. Complex 5 is octahedral, having a facially co-ordinated TpЈ ligand and linear NNPh2 ligands.
The present studies arose from attempts to synthesize
isodiazene† analogues of the four-co-ordinate molybdenum()
organoimido complexes [Mo(NC6H3Pri2-2,6)(CHCMe2Ph)-
(OR)2] [R = CMe3, CMe2(CF3) or CMe(CF3)2], which have
found widespread use in ring-opening metathesis polymeriz-
ation (ROMP).2 This objective has been difficult to achieve, due
primarily to surprising problems in alkylating the direct iso-
diazene analogues of imido-complexes which themselves can
readily be alkylated in high yield. Nevertheless, a series of new
molybdenum() isodiazene compounds has been isolated and
structurally characterized.
interaction of 1 with an excess of Zn(CH2CMe2Ph)2 in diethyl
ether at room temperature for 12 h afforded 1ؒMeCN, after
work-up and recrystallization from MeCN (characterised by 1H
NMR and microanalysis) as the only tractable product.
In view of the failure to substitute the chloride ligands of
compound 1 we turned to the trifluoromethanesulfonate (tri-
flate, OTf ) ligand which is known to be a better leaving group
than chloride. Golden-yellow [Mo(OTf)2(NNPh2)2(py)2] 2 was
obtained as an air and moisture sensitive compound in good
yield (50–60%) upon treatment of 1 with two equivalents of
silver triflate in acetonitrile and subsequent addition of pyrid-
ine (see Experimental section). Crystals suitable for a structure
determination were obtained by diffusion of diethyl ether into a
dichloromethane solution of 2. Solutions of the complex
deteriorate in light and were therefore stored in the dark. The
X-ray analysis shows 2 to have approximate molecular C2 sym-
metry (Fig. 1), the molybdenum co-ordination geometry being
distorted octahedral with cis O3SCF3 groups [O(5)–Mo–O(6)
73.6(3)Њ] trans to a pair of cis isodiazene ligands [N(1)–Mo–
N(3) 104.1(3)Њ], the remaining sites being occupied by pyridine
ligands [N(7)–Mo–N(8) 168.2(3)Њ] Table 1. The two equatorial
Mo–N bond lengths [1.765(8) and 1.768(7) Å] and the associ-
Results and discussion
A number of possible routes to [Mo(NNPh2)2R2] (where
R = alkyl or aryl) have been studied, including the interaction
of [MoCl2(NNPh2)2(dme)] 11 with the standard alkylating
agents LiR, RMgX, R2Mg or R2Zn (R = Me, CH2CMe3 or
CH2SiMe3) using a wide range of solvents and reaction con-
ditions. There was, however, no evidence from any of the reac-
tions to suggest clean alkylation had taken place. For example
ated N᎐N distances [ca. 1.31 Å] are very close to those found
† We have in an earlier publication1 discussed the problems of nomen-
clature and bonding in NNR2 ligands and advocated the use of the
isodiazene designation as being the most generally applicable.
᎐
in other isodiazene complexes.3 There are departures from
linearity at both N(1) and N(3), the angles being 164.2(6) and
J. Chem. Soc., Dalton Trans., 1999, 2695–2699
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Table 1 Selected bond lengths (Å) and angles (Њ) for compound 2
Table 2 Selected bond lengths (Å) and angles (Њ) for compound 3
Mo–N(3)
Mo–O(6)
Mo–N(7)
N(1)–N(2)
1.765(8)
2.203(7)
2.216(8)
1.328(10)
Mo–N(1)
Mo–N(8)
Mo–O(5)
N(3)–N(4)
1.768(7)
2.212(8)
2.266(6)
1.299(11)
Mo–N(34)
Mo–O(9)
Mo–N(3)
1.763(6)
1.878(5)
2.319(6)
1.306(8)
Mo–O(1)
Mo–O(48)
Mo–Cl
1.861(5)
2.181(5)
2.393(2)
N(34)–N(35)
N(3)–Mo–N(1)
N(1)–Mo–O(6)
N(1)–Mo–N(8)
N(3)–Mo–N(7)
O(6)–Mo–N(7)
N(3)–Mo–O(5)
O(6)–Mo–O(5)
N(7)–Mo–O(5)
N(1)–N(2)–C(32)
C(32)–N(2)–C(26)
N(3)–N(4)–C(46)
C(46)–N(4)–C(52)
104.1(3)
91.4(3)
93.6(3)
98.4(3)
84.3(3)
90.8(3)
73.6(3)
85.8(3)
119.9(6)
121.6(6)
122.4(7)
118.1(6)
N(3)–Mo–O(6)
N(3)–Mo–N(8)
O(6)–Mo–N(8)
N(1)–Mo–N(7)
N(8)–Mo–N(7)
N(1)–Mo–O(5)
N(8)–Mo–O(5)
N(2)–N(1)–Mo
N(1)–N(2)–C(26)
N(4)–N(3)–Mo
N(3)–N(4)–C(52)
164.1(4)
90.1(3)
85.3(3)
N(34)–Mo–O(1)
O(1)–Mo–O(9)
O(1)–Mo–O(48)
N(34)–Mo–N(3)
O(9)–Mo–N(3)
N(34)–Mo–Cl
O(9)–Mo–Cl
N(3)–Mo–Cl
N(34)–N(35)–C(41)
C(41)–N(35)–C(47)
98.6(3)
163.8(2)
85.5(2)
178.4(2)
82.8(2)
89.8(2)
91.4(2)
88.7(2)
119.5(6)
123.3(5)
N(34)–Mo–O(9)
N(34)–Mo–O(48)
O(9)–Mo–O(48)
O(1)–Mo–N(3)
O(48)–Mo–N(3)
O(1)–Mo–Cl
O(48)–Mo–Cl
N(35)–N(34)–Mo
N(34)–N(35)–C(47)
96.9(3)
94.3(2)
88.8(2)
81.8(2)
87.3(2)
93.3(2)
175.9(1)
169.5(6)
117.1(6)
92.2(3)
168.2(3)
165.0(3)
86.0(3)
164.2(6)
118.6(6)
171.7(7)
117.4(7)
Fig. 2 View of the molecular structure of compound 3.
within, the isodiazene ligand is essentially the same as
observed in 2 (Table 2), and there is also a retention of near
coplanarity between the two N–Ph bonds and the equatorial
co-ordination plane. The co-ordination of the tridentate pyri-
dinediolate ligand is characterized by a pair of short Mo–O
bonds [1.861(5) and 1.878(5) Å] and a long Mo–N (pyridine)
distance [2.319(6) Å]. The Mo–Cl distance is typical at
2.393(2) Å, as is the Mo–O bond to the triflate ligand
[2.181(5) Å]. It is interesting that there is a short intra-
molecular contact of 2.86 Å between one of the triflate
oxygen atoms, O(50), and the α-nitrogen atom, N(34), of the
isodiazene ligand with the O ؒ ؒ ؒ N vector being essentially
orthogonal to the equatorial co-ordination plane. However,
this is not due to the presence of hydrogen bonding as the
N–N distance remains unaffected, and the diamagnetism of
the complex is not consistent with the presence of a formally
monoanionic hydrazide(1Ϫ) ligand. There is nothing note-
worthy in the packing of the molecules.
Fig. 1 View of the molecular structure of compound 2 (hydrogen
atoms omitted for clarity as in all Figures).
171.7(7)Њ respectively; the former deviation is at the lower end
of the range anticipated for a “linear” isodiazene ligand. For
both ligands, the N–Ph bonds lie approximately coplanar with
the (isodiazene)N2O2 co-ordination plane. The two axial Mo–N
(pyridyl) distances [2.212(8) and 2.216(8) Å] are noticeably
shorter than the normal value [ca 2.30 Å] observed for such
systems. The Mo–O (triflate) bonds differ significantly and have
distances [2.203(7) and 2.266(6) Å] that are slightly longer than
typical values observed for co-ordination to molybdenum,
possibly reflecting the trans influence of the isodiazene ligands.
A related organoimido complex cis[W(OTf)2(NBut)2(NH2-
But)2], formed on protonation of [W(NBut)2(NH2But)2] with
triflic acid, has been structurally characterised.4 Reaction of 1
with bipy and silver triflate in acetonitrile afforded, after work-
Ϫ
up, the known5 dication [Mo(NNPh2)2(bipy)2]2ϩ as its PF6
salt.
Although we were unable to alkylate compounds 1 and 2 it
seemed possible that an imido ligand exchange reaction of
[MoR2(NBut)2] with 1,1-diphenylhydrazine hydrochloride, simi-
lar to that observed for [MoCl2(NBut)2(dme)] to give [MoCl2-
(NNPh2)2(dme)],1 would provide an entry into alkylated iso-
diazene species. However, the reaction of [Mo(CH2CMe2Ph)2-
(NBut)2] with Ph2NNH2ؒHCl (two equivalents) in refluxing dme
afforded after work-up an orange-brown crystalline solid 4 in
high yield (ca. 75%). The infrared spectrum showed N–H
stretches at ν 3289 and 3179 cmϪ1, while the 1H NMR spectrum
contained resonances in the region for aromatic protons, tert-
butyl protons and a signal at ca. δ 4.1 due to NH. The structure
was determined by X-ray diffraction. An ORTEP7 represent-
ation of the molecule is shown in Fig. 3 and selected bond
lengths and angles are given in Table 3.
All attempts to obtain stable isodiazene/alkyl derivatives by
substitution of the triflate ligands of compound 2 via inter-
action with standard alkylating agents were unsuccessful.
Interaction of 1 with silver triflate and the bulky tridentate
alkoxide 2,6-bis(2-hydroxy-2,2-diphenylethyl)pyridine (H2L)
afforded green [MoCl(OTf)(NNPh2)(L)] 3, which has ν(Mo–
Cl) at 489 cmϪ1 and ν(NN) at 1590 cmϪ1 in the IR spectrum.
The structure has been confirmed by an X-ray analysis (Fig. 2).
The co-ordination geometry is best described as distorted
octahedral with a triflate and a chloride ligand occupying the
trans sites; the isodiazene group is trans to the pyridine ring of
the tridentate pyridinediolate ligand. The meridional arrange-
ment of the pyridinediolate is similar to its co-ordination mode
in the dioxo complexes [Mo(O)2L(Me2SO)] and [Os(O)2L(NH2-
But)],6 the pyridine ring being twisted by ca. 32Њ out of the
equatorial co-ordination plane. The pattern of bonding to, and
The binuclear compound 4 adopts a centrosymmetric edge-
shared bi-octahedral geometry with slightly asymmetric chloro
2696
J. Chem. Soc., Dalton Trans., 1999, 2695–2699

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Table 3 Selected bond lengths (Å) and angles (Њ) for compound 4
Table 4 Selected bond lengths (Å) and angles (Њ) for compound 5
Mo–N(3)
Mo–N(5)
Mo–Cl(1)
N(1)–N(2)
1.755(6)
2.255(6)
2.566(1)
1.333(8)
Mo–N(1)
Mo–Cl(2)
Mo–Cl(1Ј)
N(3)–N(4)
1.758(6)
2.468(2)
2.642(2)
1.321(8)
Mo–Cl(1)
Mo–N(3)
Mo–N(7)
N(1)–N(2)
2.451(2)
1.780(4)
2.191(4)
1.310(6)
Mo–N(1)
Mo–N(5)
Mo–N(9)
N(3)–N(4)
1.790(4)
2.279(5)
2.303(5)
1.312(6)
N(3)–Mo–N(1)
N(1)–Mo–N(5)
N(1)–Mo–Cl(2)
N(3)–Mo–Cl(1)
N(5)–Mo–Cl(1)
N(3)–Mo–Cl(1Ј)
N(5)–Mo–Cl(1Ј)
Cl(1)–Mo–Cl(1Ј)
N(2)–N(1)–Mo
N(1)–N(2)–C(11)
N(4)–N(3)–Mo
N(3)–N(4)–C(29)
107.1(3)
101.2(3)
93.0(2)
162.3(2)
83.2(2)
87.3(2)
76.1(2)
75.00(5)
168.9(5)
120.2(5)
170.7(5)
116.9(5)
N(3)–Mo–N(5)
N(3)–Mo–Cl(2)
N(5)–Mo–Cl(2)
N(1)–Mo–Cl(1)
Cl(2)–Mo–Cl(1)
N(1)–Mo–Cl(1Ј)
Cl(2)–Mo–Cl(1Ј)
Mo–Cl(1)–MoЈ
N(1)–N(2)–C(17)
C(17)–N(2)–C(11)
N(3)–N(4)–C(23)
C(23)–N(4)–C(29)
92.2(2)
92.8(2)
162.9(2)
90.6(2)
87.10(6)
165.6(2)
87.85(6)
105.00(5)
118.4(5)
119.6(5)
120.7(5)
122.3(4)
Cl(1)–Mo–N(1)
Cl(1)–Mo–N(5)
Cl(1)–Mo–N(9)
N(1)–Mo–N(5)
N(1)–Mo–N(9)
N(3)–Mo–N(7)
N(5)–Mo–N(7)
N(7)–Mo–N(9)
N(1)–N(2)–C(1)
C(1)–N(2)–C(7)
N(3)–N(4)–C(13)
C(13)–N(4)–C(19)
96.0(1)
88.3(1)
88.3(1)
89.5(2)
164.0(2)
91.4(2)
85.9(2)
82.6(2)
121.1(5)
120.7(5)
120.0(5)
121.5(5)
Cl(1)–Mo–N(3)
Cl(1)–Mo–N(7)
N(1)–Mo–N(3)
N(1)–Mo–N(7)
N(3)–Mo–N(5)
N(3)–Mo–N(9)
N(5)–Mo–N(9)
Mo–N(1)–N(2)
N(1)–N(2)–C(7)
Mo–N(3)–N(4)
N(3)–N(4)–C(19)
92.2(1)
170.2(1)
105.8(2)
91.7(2)
164.6(2)
89.4(2)
75.3(2)
174.0(4)
118.0(5)
178.2(4)
118.1(4)
Fig. 3 View of the molecular structure of compound 4.
Fig. 4 View of the molecular structure of compound 5.
bridges [Mo–Cl(1) 2.566(1) and Mo–Cl(1Ј) 2.642(2) Å] which
are coplanar with the terminal isodiazene ligands. The main
equatorial angular distortions [Cl(1)–Mo–Cl(1Ј) 75.0(1) and
N(1)–Mo–N(3) 107.1(3)Њ] arise from the chloride bridging
ligands and steric interactions between the bulky diphenyliso-
diazene ligands whose geometries are essentially the same as
in both 2 and 3, with a retention of near coplanarity of the
N–Ph bonds with the (isodiazene) N2Cl2 co-ordination plane.
The terminal axial Mo–Cl distances are long, at 2.468(2) Å,
whereas the associated trans Mo–N bond is normal at
2.255(6) Å. The co-ordination geometry to the tert-
butylamine ligand is noticeably distorted, with the Mo–N
bonds being inclined by ca. 75Њ to the equatorial co-
ordination plane, this distortion probably being due to a
weak intramolecular N–H ؒ ؒ ؒ Cl hydrogen bond to the prox-
imal axial chlorine atom on the adjacent molybdenum centre
[N ؒ ؒ ؒ Cl 3.50, H ؒ ؒ ؒ Cl 2.61 Å, N–H ؒ ؒ ؒ Cl 172Њ]. The only
feature of note in the packing of the molecules is a weak
π–π stacking between symmetry related phenyl rings in
adjacent molecules [mean interplanar separation 3.20 Å,
centroid–centroid separation 3.97 Å]. Clearly the hydrazine
hydrochloride effects hydrogen transfer to both imido and
alkyl groups with loss of the latter as hydrocarbon.‡
with inequivalent pyrazole rings in the ratio 2:1. The X-ray
analysis of 5, shown in Fig. 4, reveals the molybdenum centre
to have a distorted octahedral geometry with a conventional
fac co-ordination for the TpЈ ligand, the other sites being
occupied by a pair of isodiazene ligands and a chloride ion.
All the co-ordination distances are unexceptional (Table 4),
and there is the anticipated enlargement of the angle between
the cis-co-ordinated isodiazene moieties [N(1)–Mo–N(3)
105.8(2)Њ]. The geometries of these two ligands are essentially
the same as those observed for 2, 3 and 4, with again a
retention of near coplanarity of both sets of N–Ph bonds
with their associated equatorial co-ordination plane. There
are no notable intermolecular contacts. The structure of the
related complex [MoTp(NNPh2)2Cl] (Tp = hydrotris(pyrazolyl)-
borate) has been described,8 and the bond lengths and angles
are similar to those of 5.
Conclusion
Attempts to alkylate isodiazene complexes such as [MoCl2-
(NNPh2)2(dme)] under analogous conditions to those used for
[MoCl2(NBut)2(dme)] were unsuccessful. The precise reasons
for this are unclear, but the comparative inertness of the hal-
ides in the bis(isodiazene) complexes would be consistent with
a lower formal oxidation state. DFT Calculations on iso-
diazene complexes have suggested an overall charge on the
ligand closer to 1Ϫ than 2Ϫ, in accordance with the recently
reported calculations of Carrillo and co-workers.8 The bond
lengths within the M–N–NR2 systems were very similar to
those observed previously with complexes of this type, and
provide little direct information on formal metal oxidation
state.
The reaction of compound 1 with KTpЈ (TpЈ = tris(3,5-
dimethylpyrazolyl)hydroborate) in refluxing thf affords after
1
work-up red-brown prisms of [MoTpЈCl(NNPh2)2] 5. The H
NMR spectrum exhibits peaks at δ 5.29 and 5.76 (ratio 2:1)
attributable to the pyrazolyl ring protons, and four methyl
peaks at δ 1.79, 1.94, 2.27 and 2.51 (ratio 3:6:6:3) consistent
‡ The reaction corresponds to the transfer of all the hydrogens on
2R2NNH2ؒHCl with loss of 2 equivalents of alkane and 1 of ButNH2
per molybdenum.
J. Chem. Soc., Dalton Trans., 1999, 2695–2699
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Table 5 Crystal data, data collection and refinement parametersa for compounds 2–5
2
3
4
5
Formula
Formula weight
Space group, number
Crystal system
C36H30F6MoN6O6S2
916.7
C46H37ClF3MoN3O5S
1059.6
P1, 2
Triclinic
223
C56H62Cl4Mo2N10
1208.8
P21/n, 14
Monoclinic
293
C39H42BClMoN10
793.0
P21/n, 14
Monoclinic
291
Ia, 9b
¯
Monoclinic
293
T/K
a/Å
b/Å
c/Å
α/Њ
18.874(1)
10.753(1)
19.600(1)
—
97.97(1)
—
3939.7(3)
4
1.546
12.900(2)
14.588(3)
14.795(3)
119.41(2)
91.32(1)
95.50(2)
2406.4(8)
2
10.609(1)
18.777(2)
14.606(1)
—
106.57(1)
—
15.56(1)
13.67(1)
18.86(1)
—
105.09(3)
—
3871(9)
4
1.360
β/Њ
γ/Њ
V/Å3
2788.8(4)
Z
2c
Dc/g cmϪ3
F(000)
1.462
1078
0.60
1.440
1240
5.81
1856
4.43
1640
0.44
µ/mmϪ1
No. unique reflections
measured
observed
No. of variables
R1
3332
3009d
491
0.046
0.113
5708
4210d
514
0.063
0.149
4621
3289d
286
0.059
0.133
7065
5027e
469
0.049
0.081
wR2
a Detail in common: graphite monochromated radiation. b I-Centered cell used as C-centered cell has β = 129.8Њ. c The molecule has crystallographic
Ci symmetry. |Io| > 2σ(|Io|). e |Io| > 3σ(|Io|)
volatiles were removed in vacuo to afford an orange-red oily
Experimental
General
solid to which [Bun N]PF6 (1.8 g, 4.65 mmol) in MeOH (30 cm3)
4
was added. After 5 min stirring, the suspension was filtered and
the mother-liquor cooled (Ϫ20 ЊC) to afford red cubes. The
remaining solid was redissolved in warm MeOH (ca. 40 cm3)
and left to stand at ambient temperature for 2–3 d affording a
further crop of orange-red cubes. Overall yield 1.9 g, 80%.
Found: C, 49.6; H, 3.4; N, 10.4. C44H36F12MoN8P2 requires C,
All manipulations were carried out under an atmosphere of
dinitrogen using standard Schlenk and cannula techniques or in
a conventional nitrogen-filled glove-box. Solvents were refluxed
over an appropriate drying agent, and distilled and degassed
prior to use. Elemental analyses were performed by the micro-
analytical services of the Department of Chemistry at Imperial
College. The NMR spectra were recorded on a Varian VXR 400
S spectrometer at 400.0 (1H), 75.0 (13C) and 376.3 MHz (19F);
chemical shifts are referenced to the residual protio impurity of
the deuteriated solvent. The IR spectra (Nujol mulls, KBr win-
dows) were recorded on Perkin-Elmer 577 and 457 grating
spectrophotometers. The starting materials [MoCl2(NNPh2)2-
(dme)]1,1 and [Mo(CH2Ph)2(NBut)2]9 were prepared as
described in the literature. The ligand H2L was prepared by the
previously published procedure.6b All other chemicals were
obtained commercially and used as received unless stated
otherwise.
1
49.7; H, 3.4; N, 10.5%. H NMR (CD3CN): δ 9.2 (dd, 2 H,
α-Hbipy), 8.66 (d, 2 H, αЈ-Hbipy), 8.48 (m, 4 H, β-Hbipy), 8.07–7.96
(m, 4 H, β-Hbipy) and 7.23–7.06 (overlapping br m[20H, aryl
H] ϩ m[4 H, γ-Hbipy]).
[MoCl(OTf)(NNPh2)(L)] 3. 1 (1.0 g, 1.61 mmol) and silver
triflate (0.82 g, 3.2 mmol) in MeCN (40 cm3) were stirred for
4 h. After filtration and removal of volatiles, the residue was
redissolved in CH2Cl2 (30 cm3) and H2L (0.76 g, 1.61 mmol)
was added. Stirring was continued for 12 h and after filtering a
diethyl ether layer was added and left to diffuse for 2–3 d afford-
ing 3 as green needles. Yield 0.96 g, 64%. Found: C, 58.6; H, 3.9;
N, 4.4. C46H37ClF3MoN3O5S requires C, 59.2; H, 4.0; N, 4.5%.
IR: 2363w, 1951w, 1716w, 1605w, 1590m, 1574w, 1332s, 1262s,
1234s, 1199s, 1125m, 1093m, 1063s, 1022s, 991s, 946s, 920s,
877m, 843m, 817m, 787m, 775m, 761m, 750s, 702s, 676m,
633m, 609m, 601w, 584w, 561w, 528w, 513w, 489w, 459w and
436w cmϪ1. 1H NMR (acetone-d6): δ 4.15 (s, 4 H, CH2) and 6.78–
7.81 (overlapping multiplets, 33 H, aryl H). 19F NMR (acetone-
d6): δ Ϫ78.0.
Preparations
[Mo(OTf)2(NNPh2)2(py)2] 2. Compound 1 (1.1 g, 1.77 mmol)
and silver triflate (0.92 g, 3.58 mmol) in MeCN (40 cm3) were
stirred for 4 h. After filtration and removal of volatiles the resi-
due was redissolved in CH2Cl2 (30 cm3) and pyridine (0.29 cm3,
3.58 mmol) added. At this stage the flask was wrapped in foil.
Stirring was continued for 12 h and after filtering a diethyl ether
layer was added and left to diffuse for 2–3 d affording 2 as large
golden prisms. Yield 0.96 g, 59%. Found: C, 45.3; H, 3.1; N, 7.9.
C36H30F6MoN6O6S2ؒCH2Cl2 requires C, 44.4; H, 3.2; N, 8.4%.
IR: 2359w, 1608m, 1588s, 1345s, 1323s, 1205s, 1152s, 1069s,
1023s, 920m, 833m, 804m, 751s, 692s, 632s, 558s, 497m, 446m
{MoCl(NNPh2)2(ꢀ-Cl)(NH2But)}2] 4. The compound [Mo-
(CH2CMe2Ph)2(NBut)2] (3.5 g, 6.95 mmol) and Ph2NNH2ؒHCl
(3.1 g, 14.03 mmol) were combined in a dry-box. Then dme (80
cm3) was added and the system refluxed for 12 h affording an
orange-brown solution. After removal of volatiles, the residue
was extracted into toluene–pentane (1:2) and cooled to give
large brown prisms. Yield 3.1 g, 74%. Found: C, 55.8; H, 5.2; N,
12.5. C28H31Cl2MoN5 requires C, 55.6; H, 5.2; N, 11.6%. IR:
3289w, 3179w, 1586m, 1340m, 1301m, 1261s, 1207m, 1159m,
1094s, 1025s, 929w, 895w, 801s, 748m, 689m, 629m, 543w, 474w
1
4
and 425s cmϪ1. H NMR (CH2Cl2): δ 8.71 (d, 4 H, JHH = 5.2
Hz, o-H of C5H5N) and 8.42–6.91 (multiplets, 26H, aryl H and
m-, p-H of C5H5N). 19F NMR (CDCl3): δ Ϫ78.5.
[Mo(NNPh2)2(bipy)2]2؉. Compound 1 (1.4 g, 2.25 mmol) and
bipy (0.35 g, 2.24 mmol) were stirred in CH2Cl2 (30 cm3) for 4 h.
After removal of volatiles, silver triflate (1.16 g, 4.51 mmol) and
MeCN (40 cm3) were added. After stirring for 12 h, bipy (0.35 g,
2.24 mmol) was added and stirring continued for 3 h. The
1
and 455w cmϪ1. H NMR (CDCl3): δ 1.41 (s, 18 H, (CH3)3C),
4.13 (d, 4 H, NH2) and 6.75–8.17 (overlapping multiplets, 40 H,
aryl H).
2698
J. Chem. Soc., Dalton Trans., 1999, 2695–2699

View Article Online
[MoTpЈCl(NNPh2)2] 5. Tetrahydrofuran (20 cm3) was added
to compound 1 (1.0 g, 1.61 mmol) and KTpЈ (0.54 g, 1.61
mmol) in a thick-walled ’rotaflo’ ampoule. After refluxing for
12 h the volatiles were removed in vacuo and the residue was
extracted with hot MeCN (25 cm3) affording on-cooling red-
brown crystals of 5. Yield 0.41 g, 35% (isolated yield). Found:
C, 58.8; H, 5.2; N, 17.7. C39H42BClMoN10 requires C, 59.1; H,
5.2; N, 17.7%. IR: 2360m, 2342m, 1588w, 1542w, 1289m, 1261s,
1208w, 1155w, 1093s, 1022s, 800s, 757w, 723w and 693w cmϪ1.
1H NMR (CDCl3): δ 1.79 (s, 3 H, pz CH3), 1.94 (s, 6 H, pz CH3),
2.27 (s, 6 H, pz CH3), 2.51 (s, 3 H, pz CH3), 5.29 (s, 2 H, pz CH),
5.76 (s, 1 H, pz CH), 6.79 and 6.94 (2 × br s, 20 H, aryl H).
13C-{1H} NMR (CDCl3) : chemically inequivalent pyrazol rings
A and B (ratio 2:1), δ 12.5(A)/13.0(B) (5-CH3), 14.5(B)/15.1(A)
(3-CH3), 29.7 (CH2), 106.5(A)/106.6(B) (C-4), 119.6, 121.7,
122.0, 125.3, 128.7, 128.9, 129.1, 129.2 (aryls), 142.5(A)/
143.9(B) (C-3) and 151.4(A)/152.9(B) (C-5).
mined by both an R-factor test (Rϩ = 0.046, RϪ = 0.052) and by
use of the Flack parameter, which refined to a value of
Ϫ0.01(2).
CCDC reference number 186/1539.
See http://www.rsc.org/suppdata/dt/1999/2695/ for crystallo-
graphic files in .cif format.
Acknowledgements
The Engineering and Physical Sciences Research Council are
thanked for financial support.
References
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2 See for example: R. R. Schrock, Acc. Chem. Res., 1990, 23, 158;
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10 SHELXTL PC, version 5.03, Siemens Analytical X-Ray Instru-
ments, Inc., Madison, WI, 1994.
X-Ray crystallography
A summary of the crystal data, data collection and refinement
parameters for compounds 2–5 is given in Table 5. Data were
collected on Siemens P4 diffractometers using ω–scans. Struc-
tures were solved by the heavy atom method. All the major
occupancy non-hydrogen atoms were refined anisotropically
using full-matrix least squares based on F2 for 2–416 but on F
for 5.11 The crystals of 4 were found to contain full and partial
occupancy dichloromethane solvent molecules distributed over
multiple sites; only the major occupancy atoms were refined
anisotropically. In 3 both of the O3SCF3 groups exhibited
rotational disorder about the S–C bonds, with the fluorine
atoms occupying both the staggered (75%) and eclipsed (25%)
conformations; only the major occupancy fluorine atoms were
refined anisotropically. In 3–5 the pendant phenyl rings were
refined as idealized rigid bodies. The C–H hydrogen atoms in all
of the complexes were placed in calculated positions, assigned
isotropic thermal parameters, U(H) = 1.2Ueq(C) [U(H) =
1.5Ueq(C–Me/N)] for 2–4, and 1.3Ueq(C) for 5, and allowed to
ride on their parent atoms. The N–H hydrogen atoms in 4 were
located from a ∆F map and refined subject to a distance con-
straint (0.90 Å). The polarity of 3 was unambiguously deter-
11 MOLEN, Enraf-Nonius, Delft, 1990.
Paper 9/03372F
J. Chem. Soc., Dalton Trans., 1999, 2695–2699
2699