A new, flexible N,N,N-Tripodal facially capping ligand system: Synthesis and structural characterization of β-Triketimines and their M(CO) 3 complexes (M = Cr, Mo, W)

FULL PAPER

DOI: 10.1002/ejic.200801022

A New, Flexible N,N,N-Tripodal Facially Capping Ligand System: Synthesis

and Structural Characterization of β-Triketimines and Their M(CO)₃

Complexes (M = Cr, Mo, W)

Donna Barnes,^[a]Gemma L. Brown,^[a]Martyn Brownhill,^[a]Ian German,^[a]

Christopher J. Herbert,^[a]Andrew Jolleys,^[a]Alan R. Kennedy,^[b]Boyang Liu,^[a]

Katy McBride,^[a]Francis S. Mair,*^[a]Robin G. Pritchard,^[a]Arron Sanders,^[a]and

John E. Warren^[c]

Dedicated to the memory of Swiatoslaw (Jerry) Trofimenko^[†]

Keywords: Tridentate ligands / N ligands / Ligand design / Chromium / Microporous materials

Reaction of imidoyl chlorides Ar*N=CClR (Ar* = 2-iPrC₆H₄,

2,6-iPr₂C₆H₃, 2-MeOC₆H₄; R = Me, Ph, tBu) with [Li(nacnac)]

[nacnac = (Ar*NCMe)₂CH] gives β-triketimines L, most of

which exist in solution in equilibrium with their imine/

enamine tautomers. The route is highly modular, allowing

independent variation of at least five parameters. The solu-

tion equilibria are very sensitive to such substituent pattern

variation. Single-crystal X-ray diffraction analyses of exam-

ples of both tautomers and a geometric isomer in the solid

state are presented, alongside solution NMR studies of the

tautomerism. All examples revert exclusively to the β-tri-

imine form on complexation with M(CO)₃fragments (M = Cr,

Mo, W). Facial isomers result. The ligands are weak σ-do-

nors, as adjudged by CO IR stretching frequencies in

[LM(CO)₃]. Crystal-structure determination on the iso-

structural pair [HC(2-iPrC₆H₄N=CMe)₃M(CO)₃] (M = Cr, Mo)

revealed a hexagonal packing arrangement composed of

aryl–aryl and carbonyl (CO)–H–C interactions which gener-

ates pseudocylindrical voids accounting for 6–9% of the crys-

tal volume. In only one case were these occupied by solvent

molecules. This family of facially capping N,N,N-ligands

with finely tunable bulk have wide potential in coordination

chemistry.

Germany, 2009)

versible addition of ketones to generate a fragile N,N,O-

scorpionate ligand which dissociated upon dissolution or

attempted isolation as neutral species.^[4]We also reported

the C-alkylation of the anions to generate neutral β-di-

imines lacking α-hydrogen acidity.^[5]Here, we report the use

of more functional electrophiles, imidoyl chlorides, which

proceed by elimination of LiCl to yield isolable tridentate

proligands, also posessed of the significant and variable or-

tho-bulk that characterized the renaissance of the nacnac

ligand class, which we term β-triketimines. The resultant

ligands (i) merit consideration alongside such well-estab-

lished ligand classes as “trisox” (ii),^[6]tris(pyrazolyl)meth-

anes (iii),^[7]“protach” triimines (iv),^[8]triazacyclohexanes

(v),^[9]and tris(imidazoles) (vi),^[10]in applications which in-

clude supramolecular, biomimetic and catalytic chemistry

(see ref.^[6–10]and references therein).

Introduction

The provision of new ligands underpins the development

of new coordination chemistry. Illustrating this tenet is the

wide array of novel results across main group, organometal-

lic and classical coordination chemistry supported by the

bulky β-diketiminate ligand class: since its introduction as

a neutral β-diimine in 1997,^[1]followed by its more frequent

use as an N,N-bidentate spectator monoanion in 1998,^[2]

[(2,6-iPr₂C₆H₃NCMe)₂CH]^–(dipp-nacnac) has become a li-

gand of choice in generating low-coordination-number

complexes.^[3]In a recent paper we described some fluori-

nated examples of this type of anion, and reported the re-

[†] Pioneer of scorpionate chemistry

[a] School of Chemistry, University of Manchester,

Brunswick Street, Manchester M13 9PL, UK

Fax: +44-161-275-4598

The closest literature precedents to the triketimines L de-

scribed here concern trialdimines, lacking ortho bulk, which

have been used only in their anionic form, as bidentate,

fluxional ligating species.^[11]Relevant precedent exists also

in the work of Busch and others, where addition of acetoni-

E-mail: mair@manchester.ac.uk

[b] Department of Pure and Applied Chemistry, University of

Strathclyde, Thomas Graham Building,

295 Cathedral Street, Glasgow G1 1XL, UK

[c] Synchrotron Radiation Department, Daresbury Laboratory,

Daresbury, Warrington WA4 4AD, UK

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F. S. Mair et al.

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trile to macrocyclic N₄-ligands, followed by hydrogen re- are shown in Table 1. These were obtained from reaction of

arrangement, furnished complexes, which could be regarded lithiated diketimines with imidoyl chlorides, in turn ob-

as aza-cryptand analogues.^[12]More recent work has seen tained from amides by chlorination with thionyl chloride,

this concept applied to open-chain N₄-ligands, with an ex- or triphosgene in the case of N-acetylanilines. For this case

tended range of nitriles used on a single dipyridyl-substi- also, in the imidoyl chloride synthesis, the ortho bulk on the

tuted β-diketiminate Fe complex.^[13]We here demonstrate aniline is necessary to inhibit imidoyl self-condensation;^[16]

triketimines as neutral, tridentate facially capping ligands this, coupled with the lower temperature of the triphosgene-

in the products of their reactions with M(CO)₆(M = Cr, mediated synthesis, was found to be advantageous in mini-

Mo, W), report the remarkably flexible and controllable mizing this side-reaction. Where the imidoyl substituent R¹

modular synthesis of range of examples varying both diketi- does not posess aza-enolizable protons (as for N-pivaloyl-

minate and imidoyl electrophile, and discuss the imine/en- or N-benzoylanilines) the choice of aniline substituent is

amine tautomerism exhibited by these proligands.

wider, allowing introduction of functional groups such as

OMe. The ligand synthesis is shown in full in Scheme 2.

Table 1. Triketimine key.

Results and Discussion

Triketimine

R¹

R²

R³

R⁴

R⁵

1a

1b

1c

1d

1e

1f

1g

1h^[a]

1i

1j

1k

Me

tBu

Me

tBu

Me

tBu

Ph

H

iPr

H

iPr

H

iPr

Me

H

iPr

tBu

iPr

Me

iPr

OMe

iPr

H

iPr

H

iPr

H

iPr

tBu

iPr

Ligand Synthesis

The parent β-enamine-imines were prepared rapidly in

moderate yield by the literature method of acid-catalysed

condensation facilitated by toluene/water azeotropic distil-

lation.^[2]In the current paper, only examples with identical

aniline groups on each arm of the enamine-imine are re-

ported, but the azeotropic distillation technique has pre-

viously been used to synthesise from acetylacetone en-

amine-imines with two different aniline groups present.^[14]

Furthermore, the lowered symmetry can be achieved in the

carbon backbone also, either by starting with a less sym-

metric diketone, or by using different imidoyl chlorides in

the coupling process used to prepare bulkier versions of

nacnac.^[15]In principle, therefore, the route could offer a

total of nine independently variable parameters, giving ex-

quisite control of the ligating pocket dimensions. We restrict

ourselves in this first paper to discussion of variation in

only 5 of those parameters, as defined in Scheme 1 (i).

Eleven representative examples of the resultant triketimines

H

[a] p-Me in addition to R²and R³(mesityl).

Scheme 2. Overall synthesis of triketimines from commercial rea-

gents.

Scheme 1. Tripodal N,N,N-ligands.

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Flexible N,N,N-Tripodal Facially Capping Ligand System

Addition of the imidoyl chlorides to the lithium diketimi-

nates appears to proceed with good chemoselectivity for C–

C bond formation, as was previously found for other elec-

trophiles.^[5]The synthesis does not appear to suffer from

competing imidoylation at the nitrogen atom, as was found

by Knorr in reactions with dialdimines (vinamidines).^[11]

We ascribe this difference to the protective effect of the

ortho-aryl substituents in the diketiminates used in this

study, though a full analysis of minor byproducts removed

by crystallization was not undertaken.

Figure 1. Crystal and molecular structure of 1a, tautomerizing hy-

drogen atom shown, others omitted.

Ligand Solid-State Structures

Three crystal structures of proligands L were obtained,

fortuitously, one for each tautomer/isomer believed to exist

in solution (vide infra). The three forms are depicted sche-

matically in Scheme 3.

The (E,E,E) conformation adopted by 1a means that 1,3-

sigmatropic hydrogen shift is all that is required to generate

the tridentate proligand geometry B. The alternative en-

amine-diimine (E,E,Z) geometry C was disfavoured because

it would render adjacent the two bulkiest substituents about

the C(25)–N(3) double bond.

The bond lengths (Table 2) within the enamine-imine H-

bonded ring of 1a are consistent with the alternating single

and double bonds of a conjugated system, typical of the

parent enamine-imine.^[5]The unique imine is isolated by its

almost orthogonal angle to the enamine-imine plane, and

Scheme 3. Tautomer/geometrical isomer equilibria.

Figure 1 shows the solid-state structure of 1a, potentially shows a bond length more typical of an unconjugated im-

the most symmetrical case, but which prefers to crystallise ine. At 69°, the angle between the C(6) aryl plane and the

in the enamine-diimine tautomeric form A (Scheme 3) imine plane C(1)–C(2)–N(2)–C(3) evidenced minimal con-

which allows the intramolecular N–H–N hydrogen bond jugation there also, consistent with the short C=N bond

found in the starting material to persist.

[1.277(2) Å].

Table 2. Selected bond lengths [Å] and angles [°] for 1a–c.

1a

1b

1c

N(1)–C(4)

N(1)–C(15)

N(2)–C(2)

N(2)–C(6)

N(3)–C(25)

N(3)–C(26)

C(2)–C(1)

C(2)–C(3)

1.3584(19)

1.417(2)

1.3046(18)

1.4156(19)

1.277(2)

1.4270(19)

1.507(2)

1.450(2)

N(1)–C(10)

N(1)–C(1)

N(2)–C(25)

N(2)–C(13)

N(3)–C(39)

N(3)–C(30)

C(10)–C(11)

C(10)–C(12)

1.272(3)

1.431(3)

1.276(3)

1.424(3)

1.274(3)

1.427(3)

1.504(3)

1.526(3)

1.520(4)

1.537(4)

1.506(4)

119.8(2)

129.2(2)

120.4(2)

126.6(2)

117.7(2)

115.6(2)

109.0(2)

112.7(2)

111.2(2)

114.4(2)

128.3(3)

117.1(2)

126.5(3)

118.6(3)

114.9(3)

N(1)–C(2)

N(1)–C(15)

N(2)–C(4)

N(2)–C(6)

N(3)–C(25)

N(3)–C(26)

C(1)–C(2)

C(3)–C(2)

1.326(2)

1.429(2)

1.326(2)

1.426(2)

1.286(2)

1.417(2)

1.506(3)

1.416(2)

C(3)–C(4)

C(3)–C(25)

C(25)–C(24)

1.379(2)

1.512(2)

1.508(2)

C(12)–C(39)

C(12)–C(25)

C(39)–C(40)

C(3)–C(4)

C(3)–C(25)

C(25)–C(24)

1.425(3)

1.509(3)

1.551(3)

C(4)–N(1)–C(15)

C(2)–N(2)–C(6)

C(25)–N(3)–C(26)

N(2)–C(2)–C(3)

N(2)–C(2)–C(1)

C(3)–C(2)–C(1)

C(4)–C(3)–C(2)

C(4)–C(3)–C(25)

C(2)–C(3)–C(25)

N(3)–C(25)–C(24)

N(3)–C(25)–C(3)

C(24)–C(25)–C(3)

N(1)–C(4)–C(3)

C(3)–C(4)–C(5)

N(1)–C(4)–C(5)

127.59(13)

121.35(13)

121.95(14)

120.25(14)

122.37(13)

117.38(13)

123.90(13)

117.92(13)

118.10(13)

125.34(14)

117.44(14)

117.21(14)

120.58(14)

121.12(13)

118.27(13)

C(10)–N(1)–C(1)

C(25)–N(2)–C(13)

C(39)–N(3)–C(30)

N(1)–C(10)–C(11)

N(1)–C(10)–C(12)

C(11)–C(10)–C(12)

C(39)–C(12)–C(10)

C(39)–C(12)–C(25)

C(10)–C(12)–C(25)

N(2)–C(25)–C(12)

N(2)–C(25)–C(26)

C(12)–C(25)–C(26)

N(3)–C(39)–C(40)

N(3)–C(39)–C(12)

C(40)–C(39)–C(12)

C(2)–N(1)–C(15)

C(4)–N(2)–C(6)

C(25)–N(3)–C(26)

N(1)–C(2)–C(3)

N(1)–C(2)–C(1)

C(3)–C(2)–C(1)

C(2)–C(3)–C(4)

C(4)–C(3)–C(25)

C(2)–C(3)–C(25)

N(3)–C(25)–C(24)

N(3)–C(25)–C(3)

C(3)–C(25)–C(24)

N(2)–C(4)–C(3)

C(3)–C(4)–C(5)

N(2)–C(4)–C(5)

123.88(17)

122.92(16)

123.04(15)

121.39(17)

117.97(16)

120.55(16)

122.71(17)

118.54(15)

118.53(16)

114.24(16)

123.89(16)

121.78(15)

120.56(16)

120.28(16)

119.16(16)

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For 1b, in which both 2- and 6-isopropyl groups are pres-

ent on one aryl group, and where a tert-butyl group has

replaced methyl substituent R¹(Figure 2), the true triketim-

ine form B was observed, mirroring the behaviour of simi-

larly bulky β-diimines.^[17]It seems at first strange that there

was no requirement for (E) disposition of the tert-butyl

group and the 2,6-disubstituted aryl group, giving the alter-

native enamine-diimine form C. This was prevented by the

unfavourable R²–C(12) steric repulsion that would result.

Consequently, form B has a (Z) disposition of the tert-butyl

group and the pendant aryl group, as does form A. The

strain that this causes in form B for 1b is shown by the

C(26)–C(25)–N(2) and C(25)–N(2)–C(13) angles of 128.3

and 129.2°, respectively (Table 2). Mapping of this situation

onto form A would push R¹significantly towards fulcrum

carbon atom C(12). Hence, it is the avoidance of an induced

steric clash, which pushes C(12) away from R¹, and guaran-

tees the sacrifice of the N–H–N hydrogen bond. Conse-

quently, all three imine bonds in 1b exhibit an (E,E,E) dis-

position and define an as-yet unfilled pocket. This confor-

mation is perfectly predisposed for coordination: minimal

reorganisation is required upon metal binding.

Figure 3. Crystal and molecular structure of 1c, tautomerizing hy-

drogen atom shown, others omitted; methyl groups on isopropyl

methine atoms C(12), C(21) and C(32) omitted.

In 1a the plane of the isolated imine lies approximately

orthogonal to the plane of the conjugated enamine-imine.

In 1c the angle between these planes is 62.4°. Steric clash

of the isopropyl substituent of the isolated arylimine arm

[C(32)] and C(5) is prevented by twisting of the aryl plane

from orthogonality with the imine plane (twist angle 51.4°):

This option is not available to 1b, because the additional

isopropyl group on the aryl group would force orthogonal-

ity, making a clash with C(5) and, as previously discussed,

with the fulcrum carbon atom [C(3) in the case of 1a and

1c, C(12) in the case of 1b] unavoidable. Consequently, the

tris(imine) form is adopted by 1b, and the aryl groups all

lie approximately orthogonal to the imines, whose C=N dis-

tances (Table 2) all lie in the range 1.272–1.274 Å.

Tautomerism

The above arguments, giving a molecular structural basis

to the preferred isomers/tautomers in the solid state, are

potentially open to the criticism that packing forces may

be equally important in deciding the observed solid-state

structure. However, the NMR spectroscopic data in CDCl₃

solution are in persuasive accord with the solid-state results.

For those triketimines with either tBu or Ph at R¹, a

Figure 2. Crystal and molecular structure of 1b, C(12) hydrogen

atom shown, others omitted.

In 1c (Figure 3), bearing one fewer isopropyl substituent single tautomer/isomer was observed in solution. Of these

than 1b, the (E) disposition of the pendant imine causes no cases, those where the unique imine arm derived from the

serious steric clash with the fulcrum carbon atom C(3), and imidoyl chloride contained a 2,6-disubstituted aryl group

so the N–H–N hydrogen bond and conjugated system of (R¹϶ Me, R²= R³: 1b, 1h) were composed exclusively of

the enamine-imine is regained. In fact, in 1c the C(2)–C(3) triketimine tautomer B in solution, as evidenced by the α-

and C(3)–C(4) lengths (Table 2) both lie close to 1.42 Å, the CH singlet at δ = 4–5 ppm, and the absence of the NH

arithmetic mean of the corresponding distances in 1a, and signal at δ = 12–15 ppm. Those where the unique aryl group

the C–N and C=N distances are crystallographically indis- was 2-substituted only (R¹϶ Me, R²= H: 1c, 1j, 1k) were

tinguishable. The situation was modelled as a 2-site disorder composed exclusively of tautomer/isomer C (Scheme 3).

in N–H hydrogen position, with an implicit (unresolved) 2- The distinction between the (E)/(Z) isomers A and C is

site disorder in the positioning of single and double bonds based upon the assumption that the structure isolated in

round the enamine-imine, reflecting closely the dynamic the solid state is likely to be representative of the single

solution NMR behaviour. A satisfactory refinement also re- tautomer/isomer observed in solution, and the improbabil-

sulted if the hydrogen atom was left as a single atom, which ity of an (E) geometry in cases where R¹is larger than Me.

appeared equidistant between the two nitrogen atoms, There is an alternative hypothesis that the face-strain on

which would be consistent with a fully delocalised π-system. the imine bond is increased by the larger substituents, thus

We favour the interpretation of the data as disordered.

lowering the barrier to nitrogen inversion mechanism of

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Eur. J. Inorg. Chem. 2009, 1219–1233

Flexible N,N,N-Tripodal Facially Capping Ligand System

(E)/(Z) exchange to a point where it is fast at room tem- tion, seen in coalescence of the diastereotopic pair of iso-

perature;^[18]however, no evidence was found for such an propyl methyl groups in form B at approximately 70 °C; A/

exchange.

C exchange [i.e. (E)/(Z) isomerism by nitrogen inversion of

For those triketimines with methyl substituents on each the pendant imine]^[18]was observed through coalescence of

arm (i.e. R¹= Me: 1a, 1d–1g, 1i), a number of exchanging the backbone methyl groups at approximately 90 °C. Ex-

tautomers were observed in solution, i.e. many more peaks change broadening of peaks assigned to triimine tautomer

than expected for either C₃-symmetric triimine form B or B was observed at 120 °C, suggesting commencement of

enamine-diimine forms A and/or C (Scheme 3) were ob- coalescence with the A/C peaks, indicating equilibration of

served. However, single-spot TLC and satisfactory elemen- forms A, B and C by 1,3-prototopic imine/enamine ex-

tal analyses attested to the purity of the compounds; cross- change.^[19]

peaks between exchanging positions in room-temperature

NOESY spectra confirmed that the complexity was the re-

sult of a combination of (Z)/(E) isomerism and imine/en-

amine tautomerism, i.e. the equilibria shown in Scheme 3,

Carbonylmetal Complexes

rather than the presence of more than a single compound.

In thermally induced ligand substitution reactions using

In all these cases the dominant form (ca. 50–70%) was A, refluxing dibutyl ether with catalytic thf of 1a–1j with

rather than C, as shown crystallographically for 1a. For [M(CO)₆] (M = Cr: 2a–2j; M = Mo: 3a–3j; M = W: 4a) the

cases in which R¹= Me but all three aryl groups were not relative abundance of the different tautomers appears to

equivalent, the sterically least demanding aryl group occu- have little bearing on the result or speed of reaction. In all

pied the isolated imine position in the most abundant form cases, scorpionate complexes were formed, with loss of

of the two isomers of A possible.

3 mol-equiv. of CO. In line with reports detailing other, sim-

Interestingly, the (Z) form C caused slowed rotation of ilar ligands, yields of fac-[LM(CO)₃]and reaction speeds

the C–C single bond connecting the pendant imine to the were maximum for molybdenum (Cr Ͻ Mo ϾϾ W).^[7,20]In

fulcrum carbon atom [e.g. C(3)–C(25) in 1c]. This was the case of [W(CO)₆], optimal yields, though not in excess

shown by doubling of isopropyl methine and m-aryl peaks of 30%, could be attained by use of trimethylamine N-oxide

where a 2,6-iPr₂C₆H₃group occupied an enamine position. as a CO scavenger.^[20]Use of 3 mol-equiv. gave a superior

In turn, this confirmed slow rotation of the aryl–N bond in yield in a shorter time.

those cases.

The purely thermally induced reactions proceed through

In all the R¹= Me cases, a small pair of doublets at δ = several colour changes to yield red (Cr), orange (Mo) or

0.9–1.0 ppm was observed, and was assigned to inequiva- crimson (W) complexes. These colours are typical of

lent methyl groups of isopropyl substituents in the B form. charge-transfer transitions seen in other similar complexes

The observation of two distinct environments indicated that where the M(CO)₃fragment is presented with tri-N lig-

no molecular plane of symmetry bisected the two methyl ation.^[7,20,21]The tris(chelating) nature of the ligands 1 is

groups in any conformation accessible to this tautomer. clearly important in determining this κ₃coordination, be-

This indicated that the phenyl groups were essentially fixed cause for N-aryl monoketimines or N-aryl monoaldimines,

on the NMR timescale, precluding even a transient confor- π-coordination of the N-aryl group was the favoured mode

mation where they shared the imine plane. This was the of binding.^[22]The three carbonyl fragments dictate the ori-

minor solution tautomer (1a, 1e, 1f, 1g, 1i: ca. 10–20%; 1d: entation of the N-aryl groups to be pseudo-perpendicular

50%) in all cases where R¹= Me. The major tautomer was to the imine planes (84.9°), such that they have minimal

a mixture of (E)/(Z) isomers A and C, with A dominant. electronic interaction to influence the UV/Vis spectra of the

However, it is clear that for cases where R¹= Me, the energy products, all of which show expected aryl π*ǟπ and imine

differences between these tautomers is slight. It is notable π*ǟn transitions in addition to MLCT transitions around

that relatively subtle changes in substituent patterns have 500 nm. However, the complexes where R¹= Ph (2k, 3k)

such a significant effect on the positions of the equilibria.

were notably different, giving very darkly coloured com-

In many cases where R¹= Me but substituent pattern on plexes, in which the two MLCT absorptions^[21]were red-

the three aryl groups varied, this led to an even greater ar- shifted by 20–70 nm. In all other respects, 2k and 3k were

ray of conformers/isomers: In 1e, for example, there are 5 essentially identical to the other examples.

possible isomers/tautomers likely, even neglecting possible

In many cases, IR spectroscopy showed three CO stretch-

syn/anti isomerism of monosubstituted aryl conformation. ing vibrations, consistent with the solid-state structure de-

Each of these would give rise to multiple isopropyl reso- termined for [1a·Cr(CO)₃], i.e. 2a, by X-ray crystallography.

nances. It was not always possible to resolve all peaks for A C_3vstructure would give 2 bands, A₁and E, but here

all expected isomers, but the observed spectral complexity the presence of the isopropyl groups destroys the planes of

was consistent with their presence.

symmetry, thus splitting the E band into a doublet. This

It proved possible to monitor exchange of these different splitting was not resolved in all cases, however.

tautomers in the simplest case: A solution of 1a in (CD₃)₂-

The mean CO stretching frequency (weighted 2:1 in cases

1

SO showed major changes in the H NMR spectrum over where the E band split was not resolved) of 1819 cm^–1was

the temperature range 25–120 °C. Three processes were ob- approximately 15 cm^–1higher than in analogous complexes

served: The lowest energy of these was aryl–N bond rota- of tris(pyrazolyl)methanes.^[7]This would suggest that the

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triketimines 1 are slightly weaker σ-donors than the tris-

(pyrazolyl)methanes. The mean frequency varied little over

1a–1k for a given metal. It would appear that the ortho-

MeO substituent of 1j was prevented from influencing the

donicity of the ligand by the orthogonality of the aryl group

with the imine plane. Similarly, varying the ketimine carbon

substituent R¹(Me, tBu, Ph), or varying the metal from Cr

to Mo to W, had negligible electronic effect, as adjudged

from carbonyl stretching frequencies.

Three isopropyl groups, one on each aryl group, appears

to be the optimum fit. In bulkier cases, such as 1f in which

an o-tBu group was present on two aryl groups, and 2,6-

diisopropyl substitution on the remaining one, reactions

were sluggish, and yields and stabilities were low. For 1d,

with 2,6-diisopropyl substituents on all three aryl groups,

the reaction failed to proceed at all. On inspection of the

crystal structures of 1a·Cr(CO)₃and 1a·Mo(CO)₃, 2a and

3a, respectively, it becomes clear that increased bulk would

be difficult to accommodate without causing severe steric

clashes around the 6-coordinate metal centre.

Figure 4. Crystal and molecular structure of 2a, hydrogen atoms

omitted. Compound 3a is isostructural.

Table 3. Selected bond lengths [Å] and angles [°] for 2a and 3a.^[a]

2a

3a

Cr(1)–C(13)

Cr(1)–N(1)

O(1)–C(13)

N(1)–C(2)

N(1)–C(4)

C(1)–C(2)

C(2)–C(3)

C(13)–Cr(1)–C(13)# 183.46(6)

C(13)–Cr(1)–N(1)#1 93.99(4)

C(13)–Cr(1)–N(1)

1.8336(12) Mo(1)–C(13)

2.1218(10) Mo(1)–N(1)

1.1673(15) O(1)–C(13)

1.2804(15) N(1)–C(10)

1.4460(14) N(1)–C(1)

1.5211(13) C(10)–C(11)

1.4949(17) C(10)–C(12)

1.9434(19)

2.2599(16)

1.170(2)

1.287(2)

1.448(2)

1.521(2)

1.494(3)

Figure 4 depicts the crystal and molecular structure of

2a. That of 3a is identical, but for small changes in lattice

parameters. Selected bond lengths and angles for each are

listed in Table 3. The pair are isostructural and isotypic

(see Table 4 for lattice parameters). The asymmetric unit

comprises a single imine arm and carbonyl group; a crys-

tallographic axis passes through Cr(1) and C(1), rendering

the molecule rigorously C₃-symmetric. The splayed aryl

groups result in an inefficient packing of the molecules in

C(13)–Mo(1)–C(13)#1 84.19(9)

N(1)–Mo(1)–C(13)#1 95.51(8)

N(1)–Mo(1)–C(13)#2 99.65(8)

98.87(4)

C(13)–Cr(1)–N(1)#2 176.36(4)

N(1)–Cr(1)–N(1)#1 83.81(4)

N(1)–Mo(1)–C(13)

N(1)–Mo(1)–N1#1

C(1)–N(1)–C(10)

Mo(1)–N(1)–C(10)

Mo(1)–N(1)–C(1)

176.11(8)

80.71(6)

118.34(16)

120.81(13)

120.85(11)

C(2)–N(1)–C(4)

C(2)–N(1)–Cr(1)

C(4)–N(1)–Cr(1)

C(2)#1–C(1)–C(2)

N(1)–C(2)–C(3)

N(1)–C(2)–C(1)

C(3)–C(2)–C(1)

O(1)–C(13)–Cr(1)

117.83(9)

120.73(8)

121.43(7)

110.38(8)

127.33(11) N(1)–C(10)–C(12)

117.18(12) N(1)–C(10)–C(11)

115.47(12) C(11)–C(10)–C(12)

172.10(11) Mo(1)–C(13)–O(1)

¯

their P3c1 space group. This packing motif and space

C(10)–C(11)–C(10)#1 111.44(15)

group clearly have their seed in the inherent threefold

point symmetry of the molecule, which results in genera-

tion of significant pores along the c-axis (Figure 5). The

pore volumes of 219 Å³for 2a, 311 Å³for 3a after removal

of solvent,^[23]are of the order of the smaller pores in an

aluminium trimesate crystal.^[24]It, however, was a true 3-

dimensional coordination polymer, rather than a molecu-

lar crystal. In the case of carbonylmetal complexes, larger

126.10(19)

117.98(19)

115.90(17)

175.07(16)

[a] Symmetry transformations used to generate equivalent atoms:

#1: –y + 1, x – y, z; #2: –x + y + 1, –x + 1, z.

The high melting point (neither compound melts, but

hexagonal pores have recently been found, though these both decompose at elevated temperaures), and rather poor

are solvent-filled, and from a kinetic product; the crystals solubility of 2a and 3a suggested that the solid lattice is

do not survive desolvation in the same form.^[25]The per- robust. An analysis of close contacts revealed that two dis-

centage solvent-accessible volume figures^[23]for 2a (6.5%) tinct intermolecular interactions may have been responsible:

and 3a (8.8%) are modest in comparison, though crystals C–H···OC hydrogen bonds, and aryl–aryl interactions. Tak-

of 2a and 3a are distinguished from the larger-pore com- ing the first of these, the seminal work of Braga and Desi-

pounds by their capacity to retain crystallinity upon sol- raju gave ranges of the C···O distance from 3.25 up to

vent loss by evacuation.

4.00 Å as possibly indicating such a hydrogen bond,^[26]but

The effect of replacing Cr with Mo is seen in the larger that a CH···O angle close to 140° was a superior indicator

cell constants (Table 4) of 3a versus 2a. The larger atomic of such interactions having a structure-directing influence.

radius of Mo over that of Cr is accommodated by an expan- In both these respects, values for 2a (3.41 Å and 146.8°,

sion of the ligand pocket, as judged by the N–N distance respectively, by using a corrected C–H distance of 1.08 Å,

in the Mo case of 2.927 Å versus 2.834 Å in the Cr case. as in the original paper^[26]) seem to support this view. In-

This expansion allows the C=N–metal angle to remain deed, the corrected H···O distance of 2.45 Å lies within the

close to the sp²ideal (M = Cr: 120.73°; M = Mo: 120.85°). most populated range of the observed distribution of dis-

It also can account for a lengthening of the a/b cell dimen- tances.^[26]Less consistent with the view of the interaction

sion of 0.215 Å. The observed lengthening of 0.293 Å re- as structure-directing is the CO–H angle, which at 94.87°

sults from a combination of this effect with that of the in- (corrected), is some way sharper than the mean (127.1°)

clusion of a molecule of solvent in the pores of 3a, where previously recorded for terminal carbonyl groups. It is pos-

those of 2a were vacant.

sible that packing is more strongly dictated by the short

1224

www.eurjic.org

Eur. J. Inorg. Chem. 2009, 1219–1233

Flexible N,N,N-Tripodal Facially Capping Ligand System

Table 4. X-ray data collection and refinement details.

1a

1b

1c

2a

3a·0.39Et₂O

Empirical formula

M_w

C₃₄H₄₃N₃

493.71

C₄₀H₅₅N₃

577.87

C₃₇H₄₉N₃

535.79

C₃₇H₄₃CrN₃O₃

629.74

C_39.57H₄₃MoN₃O_3.39

698.83

Crystal system

a [Å]

b [Å]

c [Å]

monoclinic

13.7441(2)

10.8258(2)

20.3707(4)

90

monoclinic

9.7230(3)

15.1749(4)

24.1171(8)

90

monoclinic

9.8756(2)

19.9334(4)

17.1360(4)

90

rhombohedral

14.5311(4)

18.4788(10)

90

rhombohedral

14.8240(4)

14.8240(5)

18.5430(4)

90

α [°]

β [°]

γ [°]

Space group

Z

102.6210(10)

90

P2₁/c

90.548(1)

90

P2₁/n

104.9990(10)

90

P2₁/n

90

120

¯

P3c1

4

T [K]

123(2)

0.064

123(2)

0.062

150(2)

0.063

120(2)

0.315

200(2)

0.41

µ [mm^–1]

Reflections measured

Reflections observed^[a](R_int

R₁(observed)

wR₂(all data)^[b]

Device

7205

7205 (0)

0.0508

0.1882

Kappa CCD

10910

5590 (0.1106)

0.0573

0.1297

Kappa CCD

40515

5711 (0.0655)

0.0589

0.1696

Kappa CCD

25211

3416 (0.0848)

0.0445

0.1217

Synchrotron

4602

)

2450(0.0365)

0.0395

0.0882

Kappa CCD

[a] I Ͼ 2σ(I). [b] wR₂= {σ[w(F_o– F_c) ]/σ[w(F_o²)²]}^1/2

.

2

2 2

Figure 5. Crystal packing diagram of 3a, viewed along the c-axis, with disordered solvent occupying the pores omitted.

aryl–aryl interactions shown by C(6)–C(6Ј) and C(7)–C(7Ј)

contacts of 3.37 and 3.38 Å, respectively.^[27]The two phenyl

rings define mutually parallel planes. These distances and

geometry characterise quite strong parallel-slipped aryl in-

teractions. The degree of slippage is so large that it would

be incorrect to term it π–π interaction.^[25]According to

Hunter and Sanders’ “rule 3”, the interaction is principally

a σ–π one.^[28]The combination of these two interactions for

Figure 6. Sketch of supramolecular interactions between two asym-

metric units of 2a/3a.

two asymmetric units from different molecules is shown in

Figure 6.

Because there are three asymmetric units per molecule,

crystal symmetry generates an intricate 2D supramolecular weaker. Interestingly, 2g and 3g, with a single additional

network composed of a double-layer of molecules in the ab- isopropyl substituent precluding the supramolecular net-

plane which, though composed of interactions which are work, were significantly more soluble than 2a and 3a.

individually relatively weak, produce a robust lattice

For both 2a and 3a, NMR spectra in dimethyl sulfoxide

through cooperativity.^[29]In 3a, the aryl σ–π interactions solution were consistent with the retention of the C₃solid-

are stretched by the larger radius of Mo, distances of 3.419 state molecular structures. Two isopropyl methyl resonances

and 3.434 Å being less convincing as structure-directing ele- confirmed that rotation around the aryl C–N bonds was

ments. However, the O···H distance is a full 0.1 Å longer slow, and hence that the solutions were racemic mixtures

than in 2a, so both intermolecular contacts must be deemed of enantiomers.Very small peaks in some cases of 2 and

Eur. J. Inorg. Chem. 2009, 1219–1233

www.eurjic.org

1225

F. S. Mair et al.

FULL PAPER

were distilled from sodium/benzophenone ketyl, hexane from so-

dium/benzophenenone ketyl with 5% added tetraglyme. The fol-

lowing compounds were synthesised according to literature pro-

cedures: enamine-imines 2,6-iPr₂C₆H₃NHCMeCHCMeN-2,6-

iPr₂C₆H₃(CAS reference 181708-81-6),^[2]2-iPrC₆H₄NHCMeCHC-

MeN-2-iPrC₆H₄(368891-65-0),^[5]2-tBuC₆H₄NHCMeCHCMeN-2-

tBuC₆H₄(213275-19-5),^[30]2-MeOC₆H₄NHCMeCHCMeN-2-Me-

OC₆H₄(613685-98-6);^[5]amides tBuCONH-2-iPrC₆H₄(33768-49-

9),^[30]tBuCONH-2-MeOC₆H₄(33768-49-9),^[31]MeCONH-2-

iPrC₆H₄(19246-04-9),^[32]PhCONH-2-iPrC₆H₄,(93007-80-8)^[32]Me-

3 evidenced minor contributions from alternative rotamers

placing 2-substituents from adjacent rings close to each

other, suggesting that some slow interconversion was pos-

sible, but attempts to monitor this process at raised tem-

peratures were thwarted by sample decomposition. Lower-

symmetry cases also showed the effects of “fixed” N–aryl

bonds; for example in 3c, where the C₃symmetry element

is destroyed by the presence of an R¹= tBu group, separate

signals were observed for each of the six distinct methyl

isopropyl groups, indicating a C₁symmetry in solution on CONH-2,6-iPr₂C₆H₃(116637-13-1),^[33]MeCONH-2-tBuC₆H₄

(7402-70-2);^[32]tBuCONH-2,4,6-Me₃C₆H₂(19699-10-6)^[34]and

the NMR timescale.

Given the robust lattice of 2a, an attempt was made to

track structural changes resulting from pumping of the

MLCT electronic transitions with constant 532 nm laser ir-

radiation, while diffraction data were recorded. Whereas

none were detected, the overnight exposure of a crystal of

2a to a stream of nitrogen gas at –120 °C caused an increase

tBuCONH-2,6-iPr₂C₆H₃(215715-81-4);^[15]imidoyl chlorides

MeC(Cl)=N-2,6-iPr₂C₆H₃(304865-77-8),^[35]tBuC(Cl)=N-2,4,6-

Me₃C₆H₂(2085-36-8)^[15]and tBuC(Cl)=N-2,6-iPr₂C₆H₃(215715-

82-5).^[15]Other materials were purchased from commercial vendors

and used as received. All manipulations except the workup of the

ligand syntheses and characterization of ligands and complexes

were performed under argon by using argon/vacuum double mani-

fold or argon-filled recirculating glovebox equipped with internally

mounted moisture- and oxygen-scrubbing columns. Details of

in residual electron density in the pores, corresponding to

approximately 20% of a nitrogen molecule, despite the per-

fluoro(polyether) oil coating of the crystal. This observation NMR spectroscopic equipment and referencing procedures are as

described elsewhere.^[5]Assignments were confirmed by appropriate

COSY, HMQC, DEPT and NOESY experiments. In all cases,

prompted a study of the gas adsorption properties of 2a

and 3a, the results of which will be subject to a future publi-

where coupling constants are not stated, it is because chemically

cation. Reports of coordination and catalytic chemistry

reasonable, reproducible and self-consistent values were not ex-

with oxidised metal ions, and introduction of further func-

tractable from the data, which in most cases was suffering from

tionality to positions R²and R³directed at the obvious

serious overlap. Microanalyses were obtained from the University

biomimetic applications of the new ligand system, shall also

be forthcoming.

of Manchester School of Chemistry Microanalysis Service.

Imidoyl Chlorides

MeC(Cl)=N-2-iPrC₆H₄: In a round-bottomed flask equipped with

a reflux condenser, triphosgene (16.51 g, 0.0556 mol; CAUTION:

Conclusions

A range of examples of the new triketimine proligand

class L are presented, demonstrating the convenient modu-

larity and flexibility of synthesis, which makes fine control

of the dimensions and shape of the ligating pocket possible.

Solution equilibria [(E)/(Z) and imine/enamine] are strongly

dependent on substitution patterns, but have little effect on

behaviour of the species as ligands.

The behaviour of the triketimines as facially capping tri-

dentate neutral ligands, complementing such well-estab-

lished ligand classes as tris(pyrazolyl)methanes, etc. was

demonstrated in [LM(CO)₃] (M = Cr, Mo, W). A limit to

the degree of ortho bulk tolerated in such six-coordinate

complexes was found. Where each imine-aryl group was 2-

substituted by a single isopropyl group, crystalline com-

pounds were obtained. Rigorous crystallographic C₃sym-

metry was imposed, and a combination of aryl–aryl and C–

H···OC interactions built a 2D network of a double-layer

of molecules in the ab-plane with pores along the c-axis,

occupied by solvent in the case of 3a, but vacant in 2a.

This C₃-symmetrical conformation was retained in solution.

Spectroscopically, only minor differences were noted with

varying substituent patterns in complexes, but we expect

more striking variation in forthcoming catalysis studies.

lachrymator, may liberate phosgene under heating) was added por-

tionwise by means of a solids addition tube to a magnetically

stirred solution of amide MeCONH-2-iPrC₆H₄(29 g, 0.164 mol) in

dichloromethane (100 mL) at 0 °C. The colourless solution was

stirred for 30 min then heated to reflux for 4 h, and stirred at room

temperature overnight. Liberated HCl was scrubbed from the pro-

tective nitrogen stream with an aqueous NaOH absorption tower

before being discharged to the fumehood. Distillation under vac-

uum (0.01 Torr) gave 3a as a colourless liquid at 72–76 °C (23.3 g,

1

3

73%). H NMR (300 MHz, CDCl₃): δ = 1.24 [d, J_HH= 4.5 Hz, 6

3

H, CH(CH₃)₂], 2.68 (s, 3 H, CH₃), 2.98 (sept, J_HH= 6 Hz, 1 H,

iPr CH), 6.75–7.38 (aromatic protons, 4 H) ppm. ¹³C{¹H} NMR

(100.57 MHz, CDCl₃): δ = 23.5 [s, (CH₃)₂CH], 28.8 [s, (CH₃)₂CH],

30.2 [s, N=C(Cl)CH₃], 120.3, 125.7, 126.1, 126.5 (4 s, aryl CH),

139.0 (s, aryl C–iPr), 143.2 [N=C(Cl)CH₃], 145.6 (s, aryl C–N)

ppm. IR (thin film on NaCl plates): ν = 1708 [ν(C=N)] cm^–1. The

˜

crude, air-sensitive oil was used in subsequent transformations

without further characterisation.

MeC(Cl)=N-2-tBuC₆H₄: Prepared in an analogous way to that de-

scribed above, from amide MeCONH-2-tBuC₆H₄, to yield a

colourless oil distilling at 84–92 °C (0.01 Torr) (4.97 g, 70%). ¹H

NMR (400 MHz, CDCl₃): δ = 1.40 (s, 9 H, tBu CH₃), 2.25 (s, 3 H,

CH₃), 7.20–7.65 (4 H, aromatic protons) ppm.

tBuC(Cl)=N-2-MeOC₆H₄: Amide tBuCONH-2-MeOC₆H₄(26.0 g,

0.126 mol) was dissolved in SOCl₂(36 mL, 0.493 mol) to give an

orange solution, which was heated under reflux for 2 h. Excess

thionyl chloride was removed by distillation under argon. Vaccum

distillation (80–84 °C, 0.01 Torr) gave tBuC(Cl)=N-2-MeOC₆H₄as

Experimental Section

General: Anilines, amines and chlorinated solvents were distilled

from calcium hydride. Toluene, diethyl ether and tetrahydrofuran

1

a bright yellow oil (26.82 g, 94%). H NMR (400 MHz, CDCl₃): δ

1226

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Eur. J. Inorg. Chem. 2009, 1219–1233

Flexible N,N,N-Tripodal Facially Capping Ligand System

= 1.40 (s, 9 H, tBu CH₃), 3.85 (s, 3 H, OCH₃), 6.75–7.15 (4 H,

aromatic protons) ppm.

ppm; enamine-diimine tautomer (major geometric isomer): δ =

18.68 (2 CH₃CN), 24.51 (1 CH₃CN), 23.34, 23.62 [CH(CH₃)₂],

27.81 [1 CH(CH₃)₂], 28.11 [2 CH(CH₃)₂], 110.44 (alkenyl α-C)

ppm; enamine-diimine tautomer (minor geometric isomer): δ =

20.41 (1 CH₃CN), 21.28 (2 CH₃CN), 23.06, 23.46 [CH(CH₃)₂],

27.44, 27.92 [CH(CH₃)₂], 105.58 (alkenyl α-C) ppm; peaks due to

aromatic CH for all isomeric species: δ = 118.29, 118.58, 119.68,

123.84, 123.98, 124.14. 124.20, 124.57, 124.61, 124.80, 125.02,

125.45, 125.56, 125.70, 125.74, 125.81, 125.91, 125.95, 126.13,

126.23 ppm; peaks due to aromatic ipso-CN and -CiPr for all iso-

meric species: δ = 138.47, 141.29, 141.80, 141.84, 142.47, 142.65,

146.58, 148.74 ppm; peaks due to conjugated C=N for all species:

δ = 157.81, 158.17 ppm; peaks due to isolated C=N/triimine C=N

for all species: δ = 169.95, 171.96 ppm. C₃₄H₄₃N₃(493.73): calcd.

C 82.71, H 8.78, N 8.51; found C 82.75, H 9.01, N 8.46. MS (ES⁺):

tBuC(Cl)=N-2-iPrC₆H₄: Prepared in an analogous way to that de-

scribed above, from amide MeCONH-2-iPrC₆H₄(28.5 g,

0.130 mol) and SOCl₂(100 mL) to yield a yellow oil distilling at

1

130 °C (0.01 Torr) (24.90 g, 84%). H NMR (400 MHz, CDCl₃): δ

3

= 1.12 (d, J_HH= 7.5 Hz, 6 H, iPr CH₃), 1.33 (s, 9 H, tBu CH₃),

3

1

2.83 (sept, J_HH= 7.5 Hz, H, iPr CH), 6.60–7.30 (non-first-order

m, 4 H, aromatic protons) ppm.

PhC(Cl)=N-2-iPrC₆H₄: Prepared in an analogous way to that de-

scribed above, from amide PhCONH-2-iPrC₆H₄(20.02 g,

0.084 mol) and SOCl₂(92 mL) to yield a yellow oil distilling at

1

122 °C (0.01 Torr) (15.10 g, 70%). H NMR (400 MHz, CDCl₃): δ

= 1.14 (d, ³J_HH= 7.5 Hz, 6 H, iPr CH₃), 2.96 (sept, ³J_HH= 7.5 Hz,

1 H, iPr CH), 6.70–7.50 (non-first-order m, 8 H, aromatic protons),

m/z = 494.4 [MH]⁺. IR: ν = 1643, 1610, 1593, 1573 [ν(C=N)] 1537

˜

3

[ν(C=C), aromatic] cm^–1.

8.12 (d, J_HH= 7.5 Hz, 1 H) ppm.

Triketimine Proligands: All triketimines were synthesised in a sim-

ilar manner. Full details are given for 1a, outline data for other

cases.

1b: Synthesised as above; 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄

(10 g, 0.0299 mol), nBuLi (19.5 mL of a 1.6  hexane solution,

0.0312 mol), tBuC(Cl)=N-2,6-iPr₂C₆H₃(8.6 mL, 0.0308 mol) and

hexane (70 mL) were used. Large colourless crystals from meth-

1a: In

a

typical procedure,

a

suspension of 2-

1

iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(17.10 g, 0.0512 mol) in n-

hexane (100 mL) was treated with n-butyllithium (32.0 mL of a

1.6  solution in hexanes, 0.0512 mol) at 0 °C, forming a dark yel-

low solution. This was stirred at 0 °C for 30 min, after which time

MeC(Cl)=N-2-iPrC₆H₄(10.0 mL, 0.0512 mol) was added, immedi-

ately causing the formation of a yellow precipitate. The mixture

was warmed to room temperature and stirred overnight. The volu-

minous yellow mixture was poured into water (200 mL), and ex-

tracted with diethyl ether. The organic phase was separated, and

the aqueous phase was further extracted with diethyl ether

(3ϫ200 mL). The combined organic layers were washed with water

(200 mL), dried with MgSO₄, filtered and stripped of solvent under

vacuum. The crude product was triturated with a small amount of

methanol, filtered and washed with cold methanol. Recrystalli-

sation from methanol gave 1a as a pale yellow crystalline material

(16.63 g, 66%); m.p. 130–132 °C. ¹H NMR (500 MHz, CDCl₃), tri-

imine tautomer (ca. 10%; reported integrals normalised): δ = 0.93,

anol/dichloromethane (11.96 g, 70%); m.p. 123–126 °C. H NMR

(500 MHz, CDCl₃): δ = 0.96 (d, ³J_HH= 6.5 Hz, 6 H), 1.02 (d, ³J_HH

3

= 6.9 Hz, 6 H), 1.05 (d, J_HH= 6.9 Hz, 6 H), 1.12 (d, J_HH

=

6.9 Hz, 6 H, CH(CH₃)₂], 1.15 [s, 9 H, tBu C(CH₃)₃], 1.92 (s, 6 H,

3

CH₃CN), 2.97–2.98 [2 overlapping sept, J_HH= 6.5 and 6.9 Hz, 4

3

4

H, CH(CH₃)₂], 4.90 (br. s, 1 H, α-CH), 6.48 (dd, J_HH= 7.6, J_HH

= 1.3 Hz, 2 H, Ar^iPro-CH), 6.88 (t, J_HH= 7.6 Hz, 1 H, Ar^iPr2p-

3

CH), 6.96 (d, J_HH= 7.6 Hz, 2 H, Ar^iPr2m-CH), overlapped with

3

6.97 (td, J_HH= 7.6, J_HH= 1.2 Hz, 2 H, Ar^iPrp-CH), 7.03 (td,

3

4

³J_HH= 7.5, J_HH= 1.5 Hz, 2 H, Ar^iPrm-CH), 7.19 (dd, J_HH

=

4

3

7.7, ⁴J_HH= 1.3 Hz, 2 H, Ar^iPrmЈ-CH) ppm. ¹³C NMR (125 MHz,

CDCl₃): δ = 20.61 (CH₃CN), 22.04, 23.26, 24.44 [3 CH(CH₃)₂],

27.68, 28.11 [iPr CH(CH₃)₂], 29.04 [tBu C(CH₃)₃], 44.20 [tBu

C(CH₃)₃], 68.11 (α-CH), 118.38 (Ar^iPro-CH), 122.21 (Ar^iPr2mЈ-

CH), 122.38 (Ar^iPr2m-CH), 123.60 (Ar^iPrp-CH), 125.50 (Ar^iPrmЈ-

CH) 126.05 (Ar^iPrm-CH), 134.04, 138.00 (aromatic ipso-CiPr),

146.23, 148.71 (aromatic ipso-CN), 169.58 (C=N) ppm. C₄₀H₅₅N₃

(577.89): calcd. C 83.14, H 9.59, N 7.27; found C 83.55, H 9.87, N

3

0.96 [2 d, J_HH= 6.9 Hz, CH(CH₃)₂, 18 H], 1.69 (s, 9 H, CH₃CN),

3

7.26. MS (ES⁺): m/z = 578.3 [MH]⁺. IR: ν = 1663, 1656 [ν(C=N)]

2.70 [sept, J_HH= 6.9 Hz, CH(CH₃)₂, 3 H], 4.59 (s, 1 H, α-CH),

˜

3

4

1591, 1574 [ν(C=C), aromatic] cm^–1.

6.69 (dd, 3 H, J_HH= 7.0, J_HH= 1.8 Hz, 3 H, o-aryl); enamine-

diimine tautomer (major geometric isomer, ca. 80%, reported inte-

3

grals normalised): δ = 1.07 [d, J_HH= 6.9 Hz, 12 H, CH(CH₃)₂],

1c: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(10.15 g, 0.0304 mol),

3

1.11 [d, J_HH= 7.0 Hz, 6 H, CH(CH₃)₂], 1.97 (s, 6 H, CH₃CN), nBuLi (19.25 mL of

a 1.6  hexane solution, 0.0308 mol),

3

2.02 (s, 3 H, CH₃C=N), 3.03 [sept, J_HH= 7.0 Hz, 1 H, CH-

(CH₃)₂], 3.13 [sept ³J_HH= 6.9 Hz, 2 H, CH(CH₃)₂], 6.54 (dd, ³J_HH

= 7.4, ⁴J_HH= 1.5 Hz, 1 H, Ar^iPro-CH), 6.83 (dd, ³J_HH= 7.5, ⁴J_HH

tBuC(Cl)=N-2-iPrC₆H₄(7.10 mL, 0.0300 mol) and hexane (80 mL)

were used. Yellow crystals from MeOH (9.41 g, 59%); m.p. 128–

1

3

130 °C. H NMR (500 MHz, CDCl₃): δ = 0.95 (d, J_HH= 6.9 Hz,

= 1.6 Hz, 2 H, Ar^iPro-CH), 7.0–7.1 (complex m, 4 t overlapped, 6 6 H), 0.99 (d, J_HH= 6.9 Hz, 6 H), 1.14 (d, J_HH= 6.8 Hz, 6 H,

3

4

H, m- and p-aryl CH), 7.20 (dd, J_HH= 7.4, J_HH= 1.0 Hz, , 2 H,

aryl mЈ-CH), 7.25 (dd, ³J_HH= 7.7, ⁴J_HH= 1.0 Hz, 1 H, aryl mЈ-CH)

13.57 (br. s, 1 H, NH), enamine-diimine tautomer (minor geometric

isomer, ca. 10%, reported integrals normalised): δ = 1.07, 1.11 [2

d overlapped with peaks due to major isomer, 18 H, CH(CH₃)₂],

1.93 (s, 3 H, CH₃CN), 2.45 (s, 6 H, CH₃CN), 3.02 [sept, J_HH

CH(CH₃)₂], 1.34 [s, 9 H, tBu C(CH₃)₃], 1.63 (s, 6 H, CH₃CN), 2.81

3

(sept, J_HH= 6.9 Hz, 2 H), 3.26 (sept, J_HH= 6.8 Hz, 1 H,

CH(CH₃)₂], 6.60 (dd, 1 H, distorted by non-first-order effects, o-

3

4

CH), 6.65 (dd, J_HH= 6.9, J_HH= 2.3 Hz, 2 H, o-CH), 6.95–7.02

(4 t, 6 H, overlapped, aromatic m- and p-CH), 7.11–7.17 (2 dd, 3

H, distorted by non-first-order effects, mЈ-CH), 13.49 (br. s, NH)

ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 20.60 (CH₃CN), 22.98,

3

=

3

6.9 Hz, 2 H, CH(CH₃)₂], 3.26 [sept J_HH= 6.9 Hz, 1 H, CH-

3

4

(CH₃)₂], 6.56 (dd, J_HH= 7.7, J_HH= 1.4 Hz, 2 H, o-aryl), 6.52, 23.12, 23.30 [CH(CH₃)₂], 27.79 [1 CH(CH₃)₂], 27.96 [2 CH-

3

4

(dd, J_HH= 7.8, J_HH= 1.1 Hz, 1 H, o-aryl), 13.30 (br. s, 1 H,

NH), 6.68–6.69 (non-first-order m), 6.83 (dd, J_HH= 7.5, J_HH

(CH₃)₂], 30.57 [C(CH₃)₃], 43.00 [C(CH₃)₃], 103.79 (alkenyl α-C),

118.64, 124.38, 124.72, 125.07, 125.20, 125.76, 125.94 (aromatic

CH), 141.51, 141.83, 142.77, 146.91 (aromatic ipso-CN and -CiPr),

158.57 (conjugated C=N), 179.34 (isolated C=N) ppm. C₃₇H₄₉N₃

(535.81): calcd. C 82.94, H 9.22, N 7.84; found C 83.89, H 9.18, N

3

4

=

1 Hz), 6.94–7.09 (non-first-order m), 7.12–7.15 (non-first-order m),

7.18–7.25 (non-first-order m) ppm. Other minor isomer/tautomer

aryl CH peaks overlapped with major isomer, in range δ = 6.94–

7.24 ppm. ¹³C{¹H} NMR (125 MHz, CDCl₃), triimine tautomer:

7.93. MS (ES⁺) m/z: 536.4 [MH]⁺. IR: ν = 1604, 1589, 1558

˜

δ = 19.03 (CH₃CN), 23.15, 23.19 [CH(CH₃)₂], 27.88 [CH(CH₃)₂] [ν(C=N)] 1527 [ν(C=C), aromatic] cm^–1.

Eur. J. Inorg. Chem. 2009, 1219–1233

www.eurjic.org

1227

F. S. Mair et al.

FULL PAPER

1d: 2,6-iPr₂C₆H₃NHCMeCHCMeN-2,6-iPr₂C₆H₃(4.2 g, 0.01 30.46 [CH(CH₃)₂and tBu C(CH₃)₃], 27.42, 27.64, 27.82, 27.88,

mol), nBuLi (6.3 mL of a 1.6  hexane solution, 0.01 mol) and 28.15 [CH(CH₃)₂], 35.05, 35.18, 35.29 [tBu C(CH₃)₃], 72.46 (α-CH,

MeC(Cl)=N-2,6-iPr₂C₆H₃(2.5 mL, 0.01 mol) were used. Pale- triimine tautomer), 106.41, 111.09 (alkenyl α-C, enamine-diimine

green crystals from methanol/dichloromethane (2.90 g, 47%); m.p.

tautomers), 118.30, 118.57, 119.52, 119.83, 120.61, 123.42, 123.53,

123.89, 123.95, 124.15, 124.19, 124.37, 124.43, 124.55, 124.62,

124.87, 125.18, 125.43, 125.55, 125.71, 125.79, 125.81, 125.86,

125.89, 126.15, 126.21, 126.23, 126.32, 126.50, 126.52, 126.56,

166–168 °C. ¹H NMR (500 MHz, CDCl₃) triketimine tautomer

3

(50%, reported integrals are normalised): δ = 1.02 [d, J_HH

=

3

6.7 Hz, 18 H, CH(CH₃)₂], 1.14 [d, J_HH= 6.8 Hz, 18 H, CH-

(CH₃)₂], 1.89 (s, 9 H, CH₃CN), 2.95 [sept, overlapped with unique 126.63 (aromatic CH), 138.06, 138.45, 139.64, 140.17, 141.21,

3

imine arm of enamine-diimine, J_HH= 6.8 Hz, 6 H, CH(CH₃)₂], 141.81, 141.87, 142.19, 142.35, 142.51, 142.74, 143.17, 143.83,

4.74 (s, 1 H, α-CH) ppm; enamine-diimine tautomer (50%, re-

144.78, 146.56, 148.44, 148.80, 149.67, 149.94 (aromatic ipso-CN,

-CiPr and -CtBu), 156.88, 157.17, 157.50, 158.87, 158.97 (conju-

ported integrals are normalised): δ = 1.04 [d, ³J_HH= 6.9 Hz, 12 H,

3

CH(CH₃)₂], 1.05 [d, J_HH= 6.9 Hz, 6 H, CH(CH₃)₂], 1.06 [d, J_HHgated C=N, enamine-diimine tautomers), 167.63, 168.63, 168.72,

= 6.9 Hz, 12 H, CH(CH₃)₂], 1.08 [d, 7.1 Hz, 6 H, CH(CH₃)₂], 1.86 169.88, 171.90 (isolated C=N, enamine-diimine tautomers/C=N,

(s, 6 H, CH₃CN), 1.93 (s, 3 H, CH₃CN), 2.95 [m, overlapped with triimine tautomer) ppm. C₃₅H₄₅N₃(507.76): calcd. C 82.79, H 8.93,

3

triketimine, J_HH= 7.1 Hz, 2 H, CH(CH₃)₂], 3.08 [sept, J_HH

=

N 8.28, found C 82.80, H 9.02, N 8.26. MS (ES⁺): m/z = 508.4

6.9 Hz, 4 H, CH(CH₃)₂], 13.5 (br. s, 1 H, NH) ppm; peaks due to

aromatic protons for both isomeric species (9 H): δ = 6.97–7.07

(non-first-order m) ppm. ¹³C{¹H} NMR (125 MHz, CDCl₃), peaks

due to both isomeric species (unless otherwise specified): δ = 19.03

[2 CH₃C(N), enamine-diimine tautomer], 21.59 [CH₃C(N), triimine

tautomer], 23.26, 23.34, 23.74, 23.83, 23.96, 24.36 [iPr CH(CH₃)₂],

25.27 [1 CH₃C(N), enamine-diimine tautomer], 27.75, 27.84, 28.31

(iPr CH(CH₃)₂], 72.06 (α-CH, triimine tautomer), 108.68 (alkenyl

α-C, enamine-diimine tautomer), 122.96, 123.26, 123.34, 123.59,

123.79,123.35 (aromatic CH), 136.55, 136.87, 140.22, 142.47,

145.91, 146.12 (aromatic ipso-CN and -CiPr), 160.15 (conjugated

C=N, enamine-diimine tautomer), 169.01, 171.97 (isolated C=N,

enamine-diimine tautomer/C=N, triimine tautomer) ppm.

C₄₃H₆₁N₃(619.98): calcd. C 83.31, H 9.92, N 6.78; found C 82.87,

[MH]⁺. IR: ν = 1643, 1608, 1593, 1571 [ν(C=N)] 1537 [ν(C=C),

˜

aromatic] cm^–1.

1f: 2-tBuC₆H₄NHCMeCHCMeN-2-tBuC₆H₄(2.0 g, 0.0055 mol),

nBuLi (3.5 mL of

a 1.6  hexane solution, 0.0055 mol),

MeC(Cl)=N-2,6-iPr₂C₆H₃(1.3 mL, 0.0055 mol) and toluene

(40 mL) were used. Pale-yellow powder from methanol (0.60 g,

20%); m.p. 116–118 °C. ¹H NMR (500 MHz, CDCl₃), peaks due to

major (E) isomer of 2,6-iPr₂C₆H₃NHCMeC[C(Me)=N-2-tBuC₆H₄]

CMeN-2-tBuC₆H₄(57% abundant; reported integrals normalised):

3

δ = 1.298 [s, 9 H, C(CH₃)₃], 1.301 [s, 9 H, C(CH₃)₃], 1.00 [d, J_HH

3

= 6.7 Hz, 6 H, CH(CH₃)₂], 1.14 [d, J_HH= 6.9 Hz, 6 H, CH-

(CH₃)₂], 1.79, 1.94, 2.09 (3 s, 3ϫ3 H, H₃CCN), 3.06 [2 sept over-

3

lapped, J_HH= 6.7 Hz, 2ϫ1 H, CH(CH₃)₂], 6.47 (dd, J_HH= 7.7,

⁴J_HH= 1.3 Hz, 1 H, isolated imine aryl o-CH), 6.68 (dd, J_HH

=

3

H 9.98, N 6.74. MS (ES⁺): m/z = 620.5 [MH]⁺. IR: ν = 1631, 1599,

˜

7.7, ⁴J_HH= 1.3 Hz, enamine aryl o-CH), 6.92–7.10 (non-first-order

m, 7 H, aryl m- and p-CH), 7.29 (d overlapped with minor isomer

1585 [ν(C=N)], 1537 [ν(C=C), aromatic] cm^–1.

3

4

peaks, 1 H, aryl m-CH), 7.32 (d, J_HH= 7.9, J_HH= 1.2 Hz, 1 H,

aryl m-CH), 13.30 (s), 13.89 (br. s, 1 H, NH) ppm; peaks due to

1e: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(4.45 g, 0.013 mol),

nBuLi (8.2 mL of

a

1.6  hexane solution, 0.013 mol), (Z) isomer and triketimine form: both 19%, and minor (E)-2-

MeC(Cl)=N-2-tBuC₆H₄(3.0 mL, 0.013 mol) and hexane (40 mL)

tBuC₆H₄NHCMeC[C(Me)=N-2,6-iPr₂C₆H₃]CMeN-2-tBuC₆H₄iso-

mer, 5%: δ = 0.85, 0.90, 0.94, 1.02, 1.04, 1.06, 1.09, 1.10 [8 d,

were used. Pale-yellow crystals from methanol/dichloromethane

(3.27 g, 50%); m.p. 130–133 °C. ¹H NMR (500 MHz, CDCl₃), 3 CH(CH₃)₂], 1.24, 1.28, 1.37, 1.43 [4 s, C(CH₃)₃], 1.75, 1.90, 1.93,

3

tautomers and 4 geometric isomers possible; (E) isomer of 2-

iPrC₆H₄NHCMeC[C(Me)=N-2-iPrC₆H₄]CMeN-2-tBuC₆H₄tauto-

mer dominant (ca. 65%) peaks reported refer to this, unless other-

1.98, 2.03, 2.08, 2.42 (7 s, H₃CN), 2.53 [sept, J_HH= 6.5 Hz, 2 H,

triketimine CH(CH₃)₂], 2.88, 2.95 [2 sept, other isomers CH-

3

(CH₃)₂], 4.69 (s, 1 H, α-CH, triimine tautomer), 6.42 (dd, J_HH

=

3

4

wise stated: δ = 1.04 [d, J_HH= 6.9 Hz, 6 H, CH(CH₃)₂], 1.11 [d,

7.5 Hz, J_HH= 1.2 Hz, 2 H, triketimine aryl o-CH), 6.54 (br. d, o-

aryl CH), 6.77, 7.26 (2 dd, mЈ-aryl CH), 13.25 [s, 1 H, (Z) isomer,

NH], 13.89 [br. s, minor (E) isomer, NH]. ¹³C{¹H} NMR

(125 MHz, CDCl₃), peaks due to all isomeric species (unless other-

wise specified): δ = 18.95, 19.03, 19.78, 20.28, 21.54, 21.95, 22.89,

23.00, 23.11, 23.73, 23.85, 23.99, 24.19, 24.41, 24.55, 25.05, 25.44,

30.96, 32.13 [iPr CH(CH₃)₂/CH₃CN], 27.78, 28.26, 28.47

³J_HH= 6.9 Hz, 6 H, CH(CH₃)₂] ppm; other isomers: δ = 0.90, 0.94,

(2 d, triketimine isomer, ca. 10%), 1.07 [2 overlapping d, (Z) isomer

of major tautomer, ca. 25%], 1.28 [s, 9 H, C(CH₃)₃] ppm; other

isomers: δ = 1.13, 1.29, 1.31, 1.38 [4 s, C(CH₃)₃], 1.92, 1.96, 2.00

(3 s, 3ϫ3 H, CH₃CN) ppm; other isomers: δ = 1.63, 1.64, 1.74,

1.97, 1.98, 2.09, 2.44 (7 s, CH₃CN), 3.02 [sept, ³J_HH= 6.9 Hz, 1 H,

3

CH(CH₃)₂] 3.13 [sept, J_HH= 6.9 Hz, 1 H, CH(CH₃)₂] ppm; other [CH(CH₃)₂], 29.58, 29.85, 30.44, 30.55, 31.27 [tBu C(CH₃)₃], 35.14,

isomers: δ = 2.67, 2.88, 2.97, 3.12, 3.26 [5 sept, CH(CH₃)₂], 4.60 (s,

35.19, 35.29, 36.08 [tBu C(CH₃)₃], 72.84 (α-CH, triimine tautomer),

105.97, 111.10 (alkenyl α-C, enamine-diimine tautomers), 119.42,

120.51, 121.26, 123.01, 123.21, 123.24, 123.34, 123.57, 123.61,

123.94, 124.16, 124.35, 124.81, 125.15, 125.42, 125.54, 125.70,

125.95, 126.26, 126.31, 126.33, 126.35, 126.45, 126.47, 126.53,

126.59, 126.61 (aromatic CH), 136.29, 136.83, 139.20, 139.43,

139.57, 140.23, 142.69, 142.77, 142.98, 143.29, 143.41, 143.48,

143.60, 144.09, 144.34, 144.99, 145.78, 146.93, 149.77, 149.85 (aro-

matic ipso-CN, -CiPr and -CtBu), 158.07, 158.43, 158.86, 159.61

(conjugated C=N, enamine-diimine tautomers), 164.98, 166.16,

167.91, 169.22 (isolated C=N, enamine-diimine tautomers/C=N,

3

4

α-CH, triimine tautomer), 6.53 (dd, J_HH= 7.4, J_HH= 1.2 Hz, 1

H, o-CH Ar^iPrisolated imine), 6.73, (dd, ³J_HH= 7.8, ⁴J_HH= 1.2 Hz,

1 H, o-CH Ar^tBuenamine), 6.82–6.87 (non-first-order m, o-CH

Ar^iPrenamine, 1 H + overlap from other isomers), 6.93–7.12 (non-

first-order m, m- and p-aryl CH, 6 H + overlap from other iso-

3

4

mers), 7.18 (dd, 1 H, mЈ-CH Ar^tBu), 7.24 (dd, J_HH= 7.7, J_HH

=

1.3 Hz, 1 H, mЈ-CH Ar^iPr), 7.30 (dd, J_HH= 7.8, J_HH= 1.3 Hz, 1

H, mЈ-CH Ar^iPr) ppm; other isomers: δ = 6.45, 6.47, 6.55, 6.60,

6.62, 6.68, 6.83 (dd, o-CH), 7.15, 7.21, 7.25, 7.29, 7.33 (dd, mЈ-aryl

CH) 13.38 (br. s, 1 H, NH) ppm; other isomers: δ = 13.20, 13.39,

3

4

13.65 (3 br. s) ppm. ¹³C{¹H} NMR (125 Hz, CDCl₃), peaks due to triimine tautomer) ppm. C₃₉H₅₃N₃(563.87): calcd. C 83.07, H 9.47,

all isomeric species (unless otherwise specified): δ = 18.42, 19.00

19.35 19.59, 19.76, 20.72, 21.12, 24.61, 25.08, 31.38 (CH₃CN),

23.06, 23.11, 23.24, 23.28, 23.34, 23.42, 23.59, 29.63, 29.97, 30.36,

N 7.45; found C 83.20, H 9.40, N 7.45. MS (ES⁺): m/z = 564.4

[MH]⁺. IR: ν = 1638, 1602, 1586 [ν(C=N)] 1534 [ν(C=C), aromatic]

˜

cm^–1.

1228

www.eurjic.org

Eur. J. Inorg. Chem. 2009, 1219–1233

Flexible N,N,N-Tripodal Facially Capping Ligand System

1g: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(3.55 g, 0.0106 mol),

MeC(Cl)=N-2-iPrC₆H₄(1.8 mL, 0.0088 mol) and hexane (40 mL)

were used. Large yellow crystals from methanol/dichloromethane

(2.82 g, 56%); m.p. 139–141 °C. ¹H NMR (500 MHz, CDCl₃),

nBuLi (6.6 mL of

a 1.6  hexane solution, 0.0106 mol),

MeC(Cl)=N-2,6-iPr₂C₆H₃(2.6 mL, 0.0106 mol) and hexane

(50 mL) were used. Off-white powder from methanol/dichloro-

methane (3.39 g, 60%); m.p. 111–114 °C. ¹H NMR (500 MHz,

peaks from triketimine form (9%)

+ (E)- and (Z)-2,6-

iPr₂C₆H₃NHCMeC[C(Me)=N-2-iPrC₆H₄]CMeN-2,6-iPr₂C₆H₃

CDCl₃), peaks due to major isomer (E)-2,6-iPr₂C₆H₃NHCMeC[C- (E)/(Z) = 45%:39%) + (E)-2,6-iPr₂C₆H₃NHCMeC[C(Me)=N-2,6-

(Me)=N-2-iPrC₆H₄]CMeN-2-iPrC₆H₄(65%, reported intensities

normalised): δ = 1.03, 1.07, 1.11, 1.14 [4 d, J_HH= 6.9 Hz, 4ϫ6

iPr₂C₆H₄]CMeN-2-iPr₂C₆H₄(7%): δ = 0.89, 0.94, 1.02–1.15 (mul-

tiple overlapping d, 30 H, CH(CH₃)₂], 1.56, 1.57, 1.81, 1.83, 1.85,

1.94, 1.99, 2.05, 2.43 (9 s, 9 H, CH₃CN), 2.55, 2.86–3.19, 3.26 (mul-

3

H, CH(CH₃)₂], 1.79, 1.99, 2.01 (3 s, 3ϫ3 H, H₃CCN), 3.02 [sept,

3

³J_HH= 6.9 Hz, 2 H, CH(CH₃)₂], 3.03 [sept, J_HH= 6.9 Hz, 1 H, tiple overlapping sept, 5 H, CH(CH₃)₂], 6.47, 6.51, 6.64, 6.82 (4 dd,

3

CH(CH₃)₂], 3.14 [sept, J_HH= 6.9 Hz, 1 H, CH(CH₃)₂], 6.53 (br. 1 H, o-aryl CH), 6.97–7.09, 7.15–7.24 (2 non-first-order m, 9 H,

3

dd, J_HH= 7.6 Hz, 1 H, isolated imine o-aryl CH), 6.82 (dd, J_HH

m-, mЈ- and p-aryl CH), 4.71, 13.08, 13.10, 13.83 (4 s, 1 H, α-

= 7.6 Hz, 1 H, enamine o-aryl CH), 6.94–7.10 (non-first-order CH, triimine tautomer + NH, enamine-diimine tautomers) ppm.

3

overlapped m, 7 H, m- and p-aryl CH), 7.19 (dd, J_HH= 7.4 Hz, 1 ¹³C{¹H} NMR (125 MHz, CDCl₃), peaks due to all isomeric spe-

3

H, mЈ-aryl CH), 7.24 (dd, J_HH= 7.7 Hz, 1 H, mЈ-aryl CH), 13.47 cies (unless otherwise specified): δ = 18.45, 18.96, 20.89, 24.38,

(br. s, 1 H, NH) ppm; other isomers {triketimine, 8%, and (Z)-2,6-

24.68, 31.49 [CH₃C(N)], 22.93, 23.08, 23.10, 23.18, 23.20, 23.35,

iPr₂C₆H₃NHCMeC[C(Me)=N-2-iPrC₆H₄]CMeN-2-iPrC₆H₄, 27%}: 23.37, 23.41, 23.50, 23.71, 23.81, 23.86, 23.99, 24.15, 24.32

δ = 0.84, 0.90, 0.98, 0.99, 1.01 [5 d, CH(CH₃)₂], 1.49, 1.76, 1.83,

1.95, 2.45(5 s, CH₃CN), 4.65 (s, 1 H, α-CH, triimine tautomer),

2.34, 2.81, 2.90, 2.94, 3.25 [5 sept, CH(CH₃)₂], 6.49, 6.59, 6.66,

7.14, 7.21 (5 dd, aryl CH), 13.34 (br. s, NH) ppm. ¹³C{¹H} NMR

(125 MHz, CDCl₃), peaks due to all isomeric species (unless other-

wise specified): δ = 18.52, 18.53, 18.55, 19.19, 19.22, 20.53, 20.63,

[CH(CH₃)₂], 27.46, 27.85, 27.90, 28.31 28.37, 28.40 [CH(CH₃)₂],

103.88, 108.55 (alkenyl α-C, enamine-diimine tautomers), 118.31,

119.73, 122.96, 123.00, 123.14, 123.18, 123.23, 123.27, 123.37,

123.61, 123.91, 124.62, 124.72, 124.76, 125.34, 125.36, 125.61,

125.76, 125.25 (aromatic CH), 136.36, 136.49, 136.85, 138.24,

139.89, 140.19, 141.40, 142.14, 142.23, 142.52, 146.01, 146.62,

24.60, 24.25, 31.35 (CH₃CN), 22.64, 22.84, 22.94, 22.99, 23.02, 148.61, 148.96 (aromatic ipso-CN and -CiPr), 158.83, 159.44 (con-

23.13, 23.15, 23.24, 23.31, 23.54, 23.67, 23.72, 24.18, 24.28 jugated C=N, enamine-diimine tautomers), 169.05, 169.46, 169.65,

[CH(CH₃)₂], 27.45, 27.83, 27.88, 28.08, 28.36, 28.56 [CH(CH₃)₂], 170.04, 171.72 (isolated C=N, enamine-diimine tautomers/C=N,

72.32 (α-CH, triimine tautomer), 104.64, 109.66 (alkenyl α-C, en- triimine tautomer) ppm. C₄₀H₅₅N₃(577.89): calcd. C 83.14, H 9.59,

amine-diimine tautomers), 118.31, 118.46, 119.81, 122.94, 123.02,

123.13, 123.16, 123.36, 123.54, 123.83, 123.86, 123.94, 124.22,

124.54, 124.59, 124.60, 124.90, 125.22, 125.48, 125.53, 125.68,

125.71, 125.74, 125.79, 125.93, 125.99, 126.14, 126.23 (aromatic

CH), 136.36, 138.04, 138.35, 139.37, 140.50, 141.27, 141.64, 141.95,

142.12, 142.34, 142.37, 142.55, 143.09, 146.65, 148.53, 148.84 (aro-

matic ipso-CN and -CiPr), 157.64, 157.80, 158.64, 158.86, 159.80

(conjugated C=N, enamine-diimine tautomers), 168.62, 170.10,

171.84 (isolated C=N, enamine-diimine tautomers/C=N, triimine

tautomer) ppm. C₃₇H₄₉N₃(535.81): calcd. C 82.94, H 9.22, N 7.84;

found C 82.69, H 9.27, N 7.78. MS (ES⁺): m/z = 536.4 [MH]⁺. IR:

N 7.27, found C 83.36, H 9.69, N 7.26. MS (ES⁺): m/z = 578.3

[MH]⁺. IR: ν = 1617, 1589, 1602 [ν(C=N)] 1537 [ν(C=C), aromatic]

˜

cm^–1.

1j: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(14.0 g, 0.0419 mol),

nBuLi (26.2 mL of

a 1.6  hexane solution, 0.0419 mol),

tBuC(Cl)=N-2-MeOC₆H₄(9.5 mL, 0.0419 mol) and hexane

(100 mL) were used. Large pale-yellow blocks from methanol

(10.15 g, 46%), m.p. 107–109 °C. ¹H NMR (500 MHz, CDCl₃)

peaks for single isomer (Z)-2-iPrC₆H₄NHCMeC[C(tBu)=N-2-

3

MeO-C₆H₄]CMeN-2-iPrC₆H₄: δ = 0.91 (d, J_HH= 6.8 Hz, 6 H),

3

0.94 [d, J_HH= 7.0 Hz, 6 H, CH(CH₃)₂], 1.33 [s, 9 H, C(CH₃)₃]

ν = 1593 (br.) [ν(C=N)] 1537 [ν(C=C), aromatic] cm^–1.

˜

3

1.68 (s, 6 H, CH₃CN), 2.71 [sept, J_HH= 6.8 Hz, 2 H, CH(CH₃)₂],

3

4

1h: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(10.11 g, 0.0302 mol),

3.61 (s, 3 H, OCH₃), 6.46 (dd, J_HH= 7.6, J_HH= 1.3 Hz, 1 H,

3

4

nBuLi (19.5 mL of

a

1.6  hexane solution, 0.0312 mol), Ar^OMeo-CH), 6.61 (dd, J_HH= 7.1, J_HH= 1.1 Hz, 2 H, Ar^iPro-

3

tBuC(Cl)=N-2,4,6-Me₃C₆H₂(7.20 mL, 0.0303 mol) and hexane

(70 mL) were used. Colourless crystals from methanol/dichloro-

methane (11.36g, 71%); m.p. 144–146 °C. ¹H NMR (500 MHz,

CH), 6.70 (br. dd, J_HH= 8.0 Hz, 1 H, Ar^OMemЈ-CH), 6.74 (td,

4

3

³J_HH= 7.6, J_HH= 1.0 Hz, 1 H, Ar^OMep-CH), 6.90 (td, J_HH

=

7.9, J_HH= 1.6 Hz, 1 H, Ar^OMem-CH), 6.95, 6.98 (2 non-first-

4

3

4

CDCl₃): δ = 0.99, 1.01 [2 overlapping d, J_HH= 7.0 Hz, 12 H,

order td, 4 H, Ar^iPrm- and p-CH), 7.10 (dd, J_HH= 6.9, J_HH

=

CH(CH₃)₂], 1.17 [br. s, 9 H, C(CH₃)₃], 1.88 (br. s, 6 H, CH₃CN), 2.4 Hz, 2 H, Ar^iPrmЈ-CH), 13.48 (br. s, 1 H, NH) ppm. ¹³C{¹H}

2.02 (s, 6 H, Mes o-CH₃), 2.16 (s, 3 H, Mes p-CH₃), 3.02 [sept,

NMR (125 MHz, CDCl₃): δ = 20.65 (CH₃CN), 23.16 [CH(CH₃)₂],

27.93 [CH(CH₃)₂], 30.73 [C(CH₃)₃], 42.16 [C(CH₃)₃], 55.21

(OCH₃), 104.53 (alkenyl α-C), 111.12 (Ar^OMemЈ-CH), 119.32

(Ar^OMeo-CH), 120.17 (Ar^OMep-CH), 124.04 (Ar^OMem-CH),

124.41 (Ar^iPro-CH), 125.65 (Ar^iPrp-CH), 125.69 (Ar^iPrmЈ-CH),

125.90 (Ar^iPrm-CH), 140.85 (Ar^iPripso-CiPr), 141.83, 142.84 (aro-

matic ipso-CN), 150.34 (Ar^OMeipso-COCH₃), 158.61 (conjugated

³J_HH= 7.0 Hz, 2 H, CH(CH₃)₂], 4.83 (br. s, 1 H, α-CH), 6.47 (dd,

4

³J_HH= 7.7, J_HH= 1.3 Hz, 2 H, o-aryl CH), 6.69 (br. s, 2 H, Mes

3

4

CH), 6.96, 7.02 (td, J_HH= 7.6, J_HH= 1.3 Hz, 2ϫ2 H, p- and m-

3

4

aryl CH), 7.18 (dd, J_HH= 7.8, J_HH= 1.3 Hz, 2 H, mЈ-aryl CH)

ppm. ¹³C NMR (125 MHz, CDCl₃): δ = 19.32 (Mes o-CH₃), 20.62

(Mes p-CH₃), 21.01 (CH₃CN), 23.20, 23.31 [CH(CH₃)₂], 27.51

[CH(CH₃)₂], 28.91 [C(CH₃)₃], 43.49 [C(CH₃)₃], 67.86 (α-CH), C=N), 182.36 (isolated C=N) ppm. C₃₅H₄₅N₃O (523.76): calcd. C

118.21 [Ar^iPr(–N=C) o-CH], 123.56 [Ar^iPr(–N=C) p-CH], 125.61

(Ar^iPrmЈ-CH), 126.03 (Ar^iPrm-CH), 128.37 (Mes CH), 130.71 (br.,

Mes ipso-CCH₃), 138.17 (Ar^iPripso-CiPr), 146.46, 148.65 (aromatic

ipso-CN), 169.58 (C=N) ppm. C₃₇H₄₉N₃(535.81): calcd. C 82.94,

H 9.22, N 7.84; found C 83.46, H 9.61, N 7.81. MS (ES⁺): m/z =

80.26, H 8.66, N 8.02, found C 80.79, H 8.57, N 8.08. MS (ES⁺):

m/z = 524.4 [MH]⁺. IR: ν = 1604, 1589 [ν(C=N)] 1531 [ν(C=C),

˜

aromatic] cm^–1.

1k: 2-iPrC₆H₄NHCMeCHCMeN-2-iPrC₆H₄(3.34 g, 0.0100 mol),

nBuLi (6.3 mL of

a 1.6  hexane solution, 0.0101 mol),

536.5 [MH]⁺. IR: ν = 1683, 1659 [ν(C=N)] 1595, 1571 [ν(C=C),

˜

PhC(Cl)=N-2-iPrC₆H₄(2.70 mL, 0.0105 mol) and diethyl ether

(20 mL) were used. Large yellow crystals from methanol/dichloro-

methane (3.63 g, 65%), m.p. 121–124 °C. ¹H NMR (500

aromatic] cm^–1.

1i: 2,6-iPr₂C₆H₃NHCMeCHCMeN-2,6-iPr₂C₆H₃(3.68 g, 0.0088

mol), nBuLi (5.5 mL of a 1.6  hexane solution, 0.0088 mol),

MHz,

CDCl₃)

peaks

for

single

isomer

(Z)-2-

Eur. J. Inorg. Chem. 2009, 1219–1233

www.eurjic.org

1229

F. S. Mair et al.

FULL PAPER

3

iPrC₆H₄NHCMeC[C(Ph)=N-2-iPrC₆H₄]CMeN-2-iPrC₆H₄:

δ

=

(2 overlapping t, J_HH= 7.3 Hz, 2ϫ3 H, m- and p-CH), 7.41 (d,

³J_HH= 7.5 Hz, 3 H, mЈ-CH) ppm. ¹³C{¹H}NMR (100.65 MHz,

[D₆]dmso): δ = 22.76 (CH₃CHCH₃), 24.07 (CH₃CHCH₃), 25.42

(CH₃C=N), 27.11 (CH₃CHCH₃), 65.23 (α-CH), 120.33, 125.86,

126.01, 126.26 (4 aryl CH), 137.47 [aryl C–CH(CH₃)₂], 149.22 (aryl

C–N), 175.99 (N=C), 218.39 (Mo–CO) ppm. C₃₇H₄₃MoN₃O₃

(673.71): calcd. C 65.96, H 6.43, N 6.24; found C 66.05, H 6.50, N

3

0.98, 1.01, 1.16 [3 d, J_HH= 6.9 Hz, 3ϫ6 H, CH(CH₃)₂], 1.56 (s,

3

6 H, CH₃CN), 2.82 (sept, J_HH= 6.9 Hz, 2 H), 3.31 (sept, J_HH

=

6.9 Hz, 1 H) [2 CH(CH₃)₂], 6.66–6.70 (non-first-order m, 2 H, en-

amine aryl o-CH), 6.73–6.77 (non-first-order m, 1 H, isolated imine

aryl o-CH), 6.97–7.02 (non-first-order m, 4 H, enamine aryl m- and

p-CH), 7.03–7.07 (non-first-order m, 2 H, isolated imine aryl m-

and p-CH) 7.12–7.14 (non-first-order m, 2 H, enamine aryl mЈ-

CH), 7.20–7.24 (non-first-order m, 1 H, isolated imine aryl mЈ-

CH), 7.37–7.43 (non-first-order m, 3 H, m- and p-Ph), 8.09–8.13

6.24. IR: ν = 1897, 1787, 1776 [ν(C=O)] 1618, 1599, 1574 [ν(C=N)]

˜

cm^–1. UV/Vis (dichloromethane): λ_max= 290 (π*ǟn, tailing into

π*ǟπ), 444, 510 [shoulder (MLCT)] nm.

3

(dd, J_HH= 7.6 Hz, 2 H, o-Ph), 13.56 (br. s, 1 H, NH) ppm. ¹³C

1a·W(CO)₃(4a): Ligand 1a (0.250 g, 0.0005 mol), W(CO)₆

(0.180 g, 0.0005 mol), nBu₂O (10 mL), thf (1.2 mL) and trimeth-

ylamine N-oxide (0.170 g, 0.0015 mol) were stirred for 30 min, then

heated to 100 °C for 2 h, then stirred overnight. Dark-crimson pre-

cipitate (0.11g, 29%). ¹H NMR (500 MHz, [D₆]dmso): δ = 1.10 [d,

NMR (125 MHz, CDCl₃): δ = 18.19 (CH₃CN), 22.05, 22.11, 22.20

[CH(CH₃)₂], 26.99 [CH(CH₃)₂], 101.15 (alkenyl α-C), 118.05,

123.27, 123.73, 123.88, 124.08, 124.49, 124.69, 124.86, 127.37,

127.52, 129.25 (aromatic CH), 140.64, 140.80, 141.40,

141.47,146.00 (aromatic ipso-CN and -CiPr), 158.44 (conjugated

C=N), 165.34 (isolated C=N) ppm. C₃₉H₄₅N₃(555.80): calcd. C

84.28, H 8.16, N 7.56; found C 84.08, H 8.05, N 7.53. MS (ES⁺):

³J_HH= 6.7 Hz, 9 H, CH(CH₃)₂] 1.39 [d, J_HH= 6.7 Hz, 9 H,

CH(CH₃)₂], 2.31 (s, 9 H, CH₃C=N), 2.82 [sept, J_HH= 6.7 Hz, 3

H, CH(CH₃)₂], 5.62 (br. s, 1 H, α-CH), 6.69 (d, J_HH= 7.2 Hz, 3

H, o-CH), 7.22, 7.25 (2 overlapping t, J_HH= 7.2 Hz, 2ϫ3 H, m-

3

m/z = 556.4 [MH]⁺. IR: ν = 1607, 1589, 1569 [ν(C=N)] 1543

˜

3

[ν(C=C), aromatic] cm^–1.

3

and p-CH), 7.39 (d, J_HH

= 7.2 Hz, 3 H, mЈ-CH) ppm.

¹³C{¹H}NMR (100.65 MHz, [D₆]dmso): δ = 22.32 (CH₃CHCH₃),

24.06 (CH₃CHCH₃), 25.52 (CH₃C=N), 27.08 (CH₃CHCH₃), 67.26

(α-CH), 120.89, 125.86, 126.16, 126.26 (4 aryl CH), 137.41 [aryl C–

CH(CH₃)₂], 149.22 (aryl C–N), 175.99 (N=C), 206.48 (W–CO)

Carbonylmetal Complexes: None of the compounds described be-

low showed a clear melting point. However, all of the chromium

complexes darken slowly above ca. 250 °C, and all of the molybde-

num and tungsten complexes darken slowly above ca. 300 °C. A

typical procedure is given in full for 2a. All other carbonylmetal

complexes were prepared analogously. Outline data, and deviations

from standard procedure, are given for other cases. 1d gave no reac-

tion with Cr(CO)₆or Mo(CO)₆under similar conditions to those

described for other examples. 1f gave some product, but solutions

decomposed during attempts at characterization. 1i gave some

product which decomposed over 1–2 d even in the solid state. Ex-

amples listed are indefinitely stable in the solid state in air, and are

stable for a number of hours in solution if protected from light.

ppm. IR: ν = 1889, 1785, 1775 [ν(CO)] 1620, 1599, 1575 [ν(C=N)]

˜

cm^–1. UV/Vis (dichloromethane): λ_max= 325 (π*ǟn, tailing into

π*ǟπ), 450, 530 [br. shoulder (MLCT)] nm.

1b·Cr(CO)₃(2b): Ligand 1b (0.570 g, 0.000988 mol), Cr(CO)₆

(0.222 g, 0.00101 mol), nBu₂O (15 mL) and thf (1 mL) were heated

to reflux for 6.5 h. Red powder (0.478 g, 68%). ¹H NMR

(500 MHz, [D₆]dmso): δ = 1.09, 1.16, 1.20, 1.28 [4 d, ³J_HH= 6.7 Hz,

4ϫ3 H, CH(CH₃)₂], 1.38–1.41 [2 overlapping d, 2ϫ3 H, CH-

(CH₃)₂], 1.44, 1.54 [2 d, 2ϫ3 H, CH(CH₃)₂], 1.12 [s, 9 H, C-

(CH₃)₃], 2.25, 2.28 (2 s, 2ϫ3 H, CH₃C=N), 2.63, 2.72, 2.93, 3.33

1a·Cr(CO)₃(2a): A magnetically stirred mixture of 1a (0.493 g,

0.001 mol) and hexacarbonylchromium (0.220 g, 0.001 mol) in di-

n-butyl ether (20 mL) and thf (1 mL) were heated to reflux. A red

precipitate became visible after approximately 20 min; heating was

continued for a further 4 h. After cooling, the mixture was stirred

at room temperature overnight, then the red precipitate (2a) was

collected by filtration, washed with hexane (4ϫ10 mL), and dried.

Yield: 0.48 g, 82%. ¹H NMR (500 MHz, [D₆]dmso): δ = 1.07 [d,

3

[4 sept, J_HH= 6.7 Hz, 4ϫ1 H, CH(CH₃)₂], 6.06 (s, 1 H, α-CH),

6.84–6.87 (non-first-order m, 1 H), 7.09–7.11 (non-first-order m, 1

H), 7.16–7.30 (non-first-order m, 7 H), 7.44–7.48 (non-first-order

m, 2 H, aromatic CH) ppm. C₄₃H₅₅CrN₃O₃(713.92): calcd. C

72.34, H 7.76, Cr 7.28, N 5.89; found C 72.31, H 8.02, Cr 7.18, N

5.81. IR: ν = 1894, 1796, 1770 [ν(C=O)] 1617, 1599, 1572 [ν(C=N)]

˜

cm^–1. UV/Vis (dichloromethane): λ_max= 289, 345 [shoulder (π*ǟn,

π*ǟπ)], 475, 550 [shoulder (MLCT)] nm.

3

³J_HH= 6.8 Hz, 9 H, CH(CH₃)₂], 1.43 [d, J_HH= 6.8 Hz, 9 H,

3

CH(CH₃)₂], 2.29 (s, 9 H, CH₃C=N), 2.80 [sept, J_HH= 6.8 Hz, 3

1b·Mo(CO)₃(3b): Ligand 1b (0.571 g, 0.000990 mol), Mo(CO)₆

(0.260 g, 0.000985 mol), nBu₂O (15 mL) and thf (3 mL) were

heated to reflux for 6 h. Red powder (0.640 g, 86%). ¹H NMR

(500 MHz, [D₆]dmso): δ = 1.08–1.50 [multiple d, 24 H, CH-

(CH₃)₂], 1.15 [s, 9 H, C(CH₃)₃], 2.27, 2.30 (2 s, 2ϫ3 H, CH₃C=N),

3

H, CH(CH₃)₂], 5.65 (s, 1 H, α-CH), 6.72 (d, J_HH= 7.5 Hz, 3 H,

o-CH), 7.21, 7.25 (2 overlapping t, ³J_HH= 7.2 Hz, 2ϫ3 H, m- and

3

p-CH), 7.41 (d, J_HH= 7.3 Hz, 3 H, mЈ-CH) ppm. ¹³C{¹H}NMR

(100.65 MHz, [D₆]dmso):

δ = 22.85 (CH₃CHCH₃), 24.22

3

(CH₃CHCH₃), 25.67 (CH₃C=N), 26.99 (CH₃CHCH₃), 64.42 (α-

CH), 120.69, 125.75, 125.81, 126.21 (4 aryl CH), 137.35 [aryl C-

CH(CH₃)₂], 149.84 (aryl C–N), 175.21 (N=C), 232.14 (Cr–CO)

ppm. C₃₇H₄₃CrN₃O₃(629.76): calcd. C 70.57, H 6.88, N 6.67,

2.82, 3.00, 3.09, 3.29 [4 sept, J_HH= 6.7 Hz, 4ϫ1 H, CH(CH₃)₂],

6.05 (s, 1 H, α-CH), 6.74–6.78 (non-first-order m, 1 H), 6.95 (br.

d, 1 H), 7.15–7.21 (non-first-order m, 3 H), 7.23–7.31 (non-first-

order m, 4 H), 7.44–7.48 (non-first-order m, 2 H, aromatic CH)

ppm. C₄₃H₅₅MoN₃O₃(757.87): calcd. C 68.15, H 7.31, Mo 12.66,

found C 69.73, H 6.93, N 6.53. IR: ν = 1893, 1796, 1775 [ν(C=O)]

˜

δ = 1619, 1598, 1574 [ν(C=N)] cm^–1. UV/Vis (dichloromethane):

λ_max= 330 (π*ǟn, br., tailing into π*ǟπ ), 469, 550 [shoulder

(MLCT)] nm.

N 5.54; found C 67.49, H 7.42, Mo 11.84, N 5.40. IR: ν = 1900,

˜

1799, 1769 [ν(C=O)] 1617, 1597, 1572 [ν(C=N)] cm^–1. UV/Vis

(dichloromethane): λ_max= 290, 345 [weak br. shoulder (π*ǟn,

π*ǟπ)], 447, 515 [shoulder (MLCT)] nm.

1a·Mo(CO)₃(3a): Ligand 1a (0.990 g, 0.002 mol), hexacarbon-

ylmolybdenum (0.53 g, 0.002 mol), nBu₂O (40 mL) and thf (2 mL)

were heated to reflux for 1 h and 45 min. Orange powder (0.80 g,

1c·Cr(CO)₃(2c): Ligand 1c (0.538 g, 0.00101 mol), Cr(CO)₆

(0.217 g, 0.000986 mol), nBu₂O (15 mL) and thf (1 mL) were

heated to reflux for 5 h. Bright-red powder (0.310 g, 47%). ¹H

60%). ¹H NMR (500 MHz, [D₆]dmso): δ = 1.10 [d, ³J_HH= 6.7 Hz,

3

9 H, CH(CH₃)₂] 1.41 [d, J_HH= 6.7 Hz, 9 H, CH(CH₃)₂], 2.31 (s, NMR (500 MHz, [D₆]dmso): δ = 1.06, 1.10, 1.24, 1.43, 1.47, 1.51

3

9 H, CH₃C=N), 2.91 [sept, J_HH= 6.7 Hz, 3 H, CH(CH₃)₂], 5.66

[6 d, J_HH= 6.8 Hz, 6ϫ3 H, CH(CH₃)₂], 1.14 [s, 9 H, C(CH₃)₃],

3

(br. s, 1 H, α-CH), 6.69 (d, J_HH= 7.5 Hz, 3 H, o-CH), 7.22, 7.27

2.25, 2.27 (2 s, 2ϫ3 H, CH₃C=N), 2.73–2.83 [3 overlapping sept,

1230

www.eurjic.org

Eur. J. Inorg. Chem. 2009, 1219–1233

Flexible N,N,N-Tripodal Facially Capping Ligand System

³J_HH= 6.8 Hz, 3ϫ1 H, CH(CH₃)₂], 6.06 (s, 1 H, α-CH), 6.75 (dd,

³J_HH= 7.6 Hz, 1 H), 6.79 (dd, ³J_HH= 7.5 Hz, 1 H), 6.82 (dd, ³J_HH

= 7.6 Hz, 1 H), 7.07–7.13 (non-first-order m, 2 H), 7.20–7.26 (non-

first-order m, 5 H), 7.42 (2 overlapping d, 2ϫ1 H, aromatic CH)

ppm. C₄₀H₄₉CrN₃O₃(671.84): calcd. C 71.51, H 7.35, Cr 7.74, N

orly defined sept, 4 H, CH(CH₃)₂], 5.64 (br. s, 1 H, α-CH), 6.71–

7.51 (poorly defined m, 11 H, aromatic CH) ppm. C₄₀H₄₉CrN₃O₃

(671.84): calcd. C 71.51, H 7.35, Cr 7.74, N 6.25; found C 70.76,

H 7.49, Cr 7.87, N 6.08. IR: ν = 1893, 1792, 1770 [ν(C=O)] 1612,

˜

1599, 1578 [ν(C=N)] cm^–1. λ_max= 340 (π*ǟn, broad, tailing into

π*ǟπ), 471, 550 [shoulder (MLCT)] nm.

6.25; found C 69.79, H 7.08, Cr 7.64, N 5.95. IR: ν = 1898, 1802,

˜

1770 [ν(C=O)] 1620, 1597, 1578 [ν(C=N)] cm^–1. UV/Vis (dichloro-

methane): λ_max= 290, 330 [shoulder (π*ǟn, π*ǟπ )], 471, 550

[shoulder (MLCT)] nm.

1g·Mo(CO)₃(3g): Ligand 1g (0.500 g, 0.000930 mol), Mo(CO)₆

(0.247 g, 0.000930 mol), nBu₂O (30 mL) and thf (1 mL) were

heated to reflux for 3.5 h. Bright-red powder (0.62 g, 93%). ¹H

NMR (400 MHz, [D₆]dmso): δ = 0.93–1.49 [multiple d, 24 H,

CH(CH₃)₂], 2.28–2.36 (multiple s, 9 H, CH₃C=N), 2.80–3.17 [mul-

tiple sept, 4 H, CH(CH₃)₂], 5.66 (br. s, 1 H, α-CH), 6.50–7.48 (non-

first-order m, 11 H, aromatic CH) ppm. C₄₀H₄₉MoN₃O₃(715.79):

calcd. C 67.12, H 6.90, Mo 13.40, N 5.87; found C 65.70, H 7.21,

1c·Mo(CO)₃(3c): Ligand 1c (0.540 g, 0.00101 mol), Mo(CO)₆

(0.268 g, 0.00102 mol), nBu₂O (15 mL) and thf (1 mL) were heated

to reflux for 6 h. Red powder (0.448 g, 63%). ¹H NMR (500 MHz,

[D₆]dmso): δ = 1.07, 1.12, 1.26, 1.40, 1.44, 1.47 [6 d, ³J_HH= 6.8 Hz,

6ϫ3 H, CH(CH₃)₂], 1.17 [s, 9 H, C(CH₃)₃], 2.27, 2.28 (2 s, 2ϫ3

3

H, CH₃C=N), 2.83 (sept, J_HH= 6.8 Hz, 2 H), 2.91 (sept, J_HH

=

Mo 12.08, N 5.70. IR: ν = 1897, 1790, 1774 [ν(C=O)] 1612, 1597,

˜

1578, 1571 [ν(C=N)] cm^–1.

6.8 Hz, 1 H, CH(CH₃)₂], 6.04 (s, 1 H, α-CH), 6.72, 6.74 (2 overlap-

3

4

ping d, 2ϫ1 H), 6.81 (dd, J_HH= 7.0, J_HH= 2 Hz, 1 H), 7.07–

7.13 (non-first-order m, 2 H), 7.20–7.29 (non-first-order m, 5 H),

7.41, 7.43 (2 overlapping d, 2ϫ1 H, aromatic CH) ppm.

C₄₀H₄₉MoN₃O₃(715.79): calcd. C 67.12, H 6.90, Mo 13.40, N

1h·Cr(CO)₃(2h): Ligand 1h (0.533 g, 0.000997 mol), Cr(CO)₆

(0.218 g, 0.00991 mol), nBu₂O (15 mL) and thf (1 mL) were heated

to reflux for 7 h. Deep-red powder (0.520 g, 78%). ¹H NMR

(500 MHz, [D₆]dmso): δ = 1.08–1.09 [m, 6 H, CH(CH₃)₂], 1.27,

5.87; found C 65.40, H 6.84, Mo 13.11, N 5.63. IR: ν = 1904,

˜

3

1803, 1769 [ν(C=O)] 1617, 1597, 1586, 1576 [ν(C=N)] cm^–1. UV/

Vis (dichloromethane): λ_max= 289, 340 [weak br. shoulder (π*ǟn,

tailing into π*ǟπ)], 445, 505 [shoulder (MLCT)] nm.

1.42 [2 d, J_HH= 6.7 Hz, 2ϫ3 H, CH(CH₃)₂], 1.11 [s, 9 H,

C(CH₃)₃], 2.13, 2.22, 2.24, 2.25, 2.28 (5 s, 5ϫ3 H, CH₃C=N and

3

Mes CH₃), 2.67, 2.83 (2 sept, J_HH= 6.7 Hz, 2ϫ1 H, CH(CH₃)₂],

6.06 (s, 1 H, α-CH), 6.78 (s, 1 H), 6.81 (s, 1 H, aromatic Mes CH),

6.87–6.91 (non-first-order m, 1 H), 7.07–7.11 (non-first-order m, 1

H), 7.20–7.28 (non-first-order m, 4 H), 7.40–7.46 (non-first-order

m, 2 H, aromatic CH) ppm. C₄₀H₄₉CrN₃O₃(671.84): calcd. C

71.51, H 7.35, Cr 7.74, N 6.25; found C 71.50, H 7.69, Cr 7.62, N

1e·Cr(CO)₃(2e): Ligand 1e (0.507 g, 0.001 mol), Cr(CO)₆(0.220 g,

0.001 mol), nBu₂O (20 mL) and thf (1 mL) were heated to reflux

for 5 h. Bright-red powder (0.580 g, 90%). ¹H NMR (500 MHz,

3

[D₆]dmso): δ = 1.08 [d, J_HH= 6.7 Hz, 3 H, CH(CH₃)₂], 1.12 [d,

3

³J_HH= 6.7 Hz, 3 H, CH(CH₃)₂], 1.43, 1.44 [2 overlapping d, J_HH

6.19. IR: ν = 1894, 1796, 1773 [ν(C=O)] 1612, 1598, 1578 [ν(C=N)]

˜

= 6.7 Hz, 2ϫ3 H, CH(CH₃)₂], 1.38 [s, 9 H, C(CH₃)₃], 2.24 (s, 3

cm^–1. UV/Vis (dichloromethane): λ_max= 289, 355 [shoulder (π*ǟn,

π*ǟπ)], 470, 550 [shoulder (MLCT)] nm.

3

H), 2.29 (s, 6 H, CH₃C=N), 2.67 (sept, J_HH= 6.7 Hz, 1 H), 2.70

3

(sept, J_HH= 6.7 Hz, 1 H, CH(CH₃)₂], 5.63 (br. s, 1 H, α-CH),

3

6.75, 6.84 (2 non-first-order m, 2ϫ1 H), 7.09 (d, J_HH= 7.5 Hz, 1

1h·Mo(CO)₃(3h): Ligand 1h (0.535 g, 0.001 mol), Mo(CO)₆

(0.266 g, 0.00101 mol), nBu₂O (15 mL) and thf (3 mL) were heated

to reflux for 7 h. Bright-red powder (0.588 g, 82%). ¹H NMR

(500 MHz, [D₆]dmso): δ = 1.08, 1.10, 1.25, 1.41 [4 d, ³J_HH= 6.8 Hz,

4ϫ3 H, CH(CH₃)₂], 1.13 [s, 9 H, C(CH₃)₃], 2.18 (s, 3 H), 2.23 (s,

3 H), 2.25 (s, 6 H), 2.29 (s, 3 H, CH₃C=N and Mes CH₃), 2.87,

H, o-CH), 7.14–7.27 (non-first-order m, 6 H, m- and p-CH), 7.40–

7.45 (non-first-order m, 2 H), 7.52–7.56 (non-first-order m, 1 H,

mЈ-CH) ppm. C₃₈H₄₅CrN₃O₃(643.79): calcd. C 70.90, H 7.05, Cr

8.08, N 6.53; found C 70.90, H 7.27, Cr 8.04, N 6.42. IR: ν =

˜

1894, 1796, 1772 [ν(C=O)] 1617, 1598, 1573 [ν(C=N)] cm^–1. UV/

3

Vis (dichloromethane): λ_max

= 330 (br., π*ǟn, tailing into

2.88 [2 sept, J_HH= 6.8 Hz, 2ϫ1 H, CH(CH₃)₂], 6.05 (s, 1 H, α-

π*ǟπ ), 471, 540 [shoulder (MLCT)] nm.

CH), 6.78, 6.80 (s, 2ϫ1 H, Mes m- + mЈ-CH), 6.81–6.85 (non-first-

3

order m, 1 H), 6.96 (d, J_HH= 7.5 Hz, 1 H), 7.20–7.29 (non-first-

1e·Mo(CO)₃(3e): Ligand 1e (0.260 g, 0.000513 mol), Mo(CO)₆

(0.133 g, 0.000504 mol), nBu₂O (15 mL) and thf (1 mL) were

order m, 4 H), 7.40–7.46 (non-first-order m, 2 H, aromatic CH)

ppm. C₄₀H₄₉MoN₃O₃(715.79): calcd. C 67.12, H 6.90, Mo 13.40,

1

heated to reflux for 7 h. Orange powder (0.240 g, 69%). H NMR

3

N 5.87; found C 66.43, H 6.97, Mo 12.60, N 5.75. IR: ν = 1899,

˜

(500 MHz, [D₆]dmso): δ = 0.98, 1.01 [2 d, J_HH= 6.5 Hz, 2ϫ3 H,

1799, 1772 [ν(C=O)] 1612, 1598, 1576 [ν(C=N)] cm^–1. UV/Vis

(dichloromethane): λ_max= 290, 345 [weak br. shoulder (π*ǟn,

π*ǟπ)], 445, 508 [shoulder (MLCT)] nm.

CH(CH₃)₂], 1.29, 1.33 [2 overlapped d, 6 H, CH(CH₃)₂], 1.29 [s, 9

H, tBu C(CH₃)₃], 2.16 (s, 3 H, CH₃C=N), 2.19 [s, 6 H, (CH₃C=N)],

3

2.73 (sept, J_HH= 6.5 Hz, 1 H), 2.74 (sept, J_HH= 6.5 Hz, 1 H,

CH(CH₃)₂], 5.54 (s, 1 H, α-CH), 6.60 (d, ³J_HH= 6.8 Hz, 1 H), 6.67

(d, J_HH= 7.1 Hz, 1 H), 6.86 (d, J_HH= 7.5 Hz, 1 H) (3 o-CH),

7.03–7.21 (non-first-order m, 6 H, m- and p-CH), 7.31, 7.32 (2 over-

1j·Cr(CO)₃(2j): Ligand 1j (0.525 g, 0.001 mol), Cr(CO)₆(0.221 g,

0.001 mol), nBu₂O (20 mL) and thf (1 mL) were heated to reflux

3

1

for 5.5 h. Red powder (0.481 g, 73%). H NMR (500 MHz, [D₆]-

3

lapping d, 2ϫ1 H), 7.43 (d, J_HH= 6.9 Hz, 1 H, mЈ-CH) ppm.

dmso): δ = 1.05, 1.08, 1.41, 1.45 [4 poorly defined d, 4ϫ3 H,

CH(CH₃)₂], 1.12 [s, 9 H, C(CH₃)₃], 2.21, 2.23 (2 s, 2ϫ3 H,

CH₃C=N), 2.72–2.87 [2 poorly defined overlapping sept, 2ϫ1 H,

CH(CH₃)₂], 3.88 (s, 3 H, OCH₃), 5.97 (s, 1 H, α-CH), 6.70 (poorly

defined d, 1 H), 6.78–6.92 (non-first-order m, 3 H), 6.95–7.01 (non-

first-order m, 1 H), 7.02–7.10 (non-first-order m, 1 H), 7.13–7.29

C₃₈H₄₅MoN₃O₃(687.73): calcd. C 66.37, H 6.59, Mo 13.96, N

6.11; found C 64.34, H 6.60, Mo 13.34, N 5.79. IR: ν = 1898,

˜

1792, 1773 [ν(C=O)] 1617, 1597, 1578, 1571 [ν(C=N)] cm^–1. UV/

Vis (dichloromethane): λ_max= 290 (π*ǟn, tailing into π*ǟπ), 444,

510 [shoulder (MLCT)] nm.

1g·Cr(CO)₃(2g): Ligand 1g (0.500 g, 0.000930 mol), Cr(CO)₆(non-first-order m, 4 H), 7.36 (poorly defined d, 1 H), 7.40 (poorly

(0.20 g, 0.000930 mol), nBu₂O (30 mL) and thf (1 mL) were heated

to reflux for 5 h. Dark-red powder (0.38 g, 60%). ¹H NMR

(500 MHz, [D₆]dmso): δ = 0.99, 1.13 [2 overlapping d, 2ϫ6 H,

defined d, 1 H) (2 aromatic CH) ppm. C₃₈H₄₅CrN₃O₄(659.79):

calcd. C 69.18, H 6.87, Cr 7.88, N 6.37; found C 66.48, H 6.76, Cr

7.62, N 6.02. IR: ν = 1897, 1802, 1766 [ν(C=O)] 1620, 1597, 1573

˜

CH(CH₃)₂], 1.27–1.58 [non-first-order m, 12 H, CH(CH₃)₂], 2.26, [ν(C=N)] cm^–1. UV/Vis (dichloromethane): λ_max= 304 (br.), 340 [w

2.29 (2 overlapping s, 3 + 6 H, CH₃C=N), 2.87–3.16 [multiple po- br. shoulder (π*ǟn, π*ǟπ )], 469, 540 [shoulder (MLCT)] nm.

Eur. J. Inorg. Chem. 2009, 1219–1233

www.eurjic.org

1231

F. S. Mair et al.

1j·Mo(CO)₃(3j): Ligand 1j (0.529 g, 0.00101 mol), Mo(CO)₆chrotron, by using silicon-monochromated Zr-edge radiation, was

FULL PAPER

(0.260 g, 0.000985 mol), nBu₂O (20 mL) and thf (1 mL) were

employed. Data were collected by a mixture of φ and ω scans at

1

heated to reflux for 5 h. Orange powder (0.531 g, 77%). H NMR

different θ and κ settings using the program COLLECT.^[36]Raw

(500 MHz, [D₆]dmso): δ = 1.08, 1.11, 1.39, 1.43 [4 d, ³J_HH= 6.8 Hz, data were processed by using DENZO-SMN^[37]to produce hkl files,

4ϫ3 H, CH(CH₃)₂], 1.15 [s, 9 H, C(CH₃)₃], 2.24, 2.26 (2 s, 2ϫ3

H, CH₃C=N), 2.86, 2.91 [2 sept, J_HH= 6.8 Hz, 2ϫ1 H, CH-

which were solved by using SIR 92^[38]and refined by using

SHELXL.^[39]Two-site disorder in one isopropyl group of 1a was

modeled, and there was a disordered diethyl ether molecule with

partial occupancy of the channels in 3a. Hydrogen atoms from this

solvent molecule were not included in the refinement. All non-hy-

3

(CH₃)₂], 3.89 (s, 3 H, OCH₃), 5.97 (s, 1 H, α-CH), 6.68 (d, J_HH

=

7.6 Hz, 1 H, Ar^OMeo-CH), 6.82 (d, J_HH= 7.7 Hz, 2 H, Ar^iPro-

3

CH), 6.87 (t, J_HH= 7.5 Hz, 1 H, Ar^OMep-CH), 6.99 (d, J_HH

=

8.3 Hz, 1 H, Ar^OMemЈ-CH), 7.06 (t, J_HH= 7.7 Hz, 1 H, Ar^OMedrogen atoms were refined anisotropically, save for the aforemen-

3

m-CH), 7.19, 7.24 (2 overlapping t, 2ϫ2 H, Ar^iPrm- and p-CH),

tioned disordered solvent atoms; all hydrogen atoms were placed

in calculated positions and refined by using a riding model, except

where noted in the text. Key crystal, data-collection and refinement

data are shown in Table 4. CCDC-699157 (1a), -699158 (1b),

-699159 (1c), -699160 (2a), and -699161 (3a) contain the supple-

mentary crystallographic data for this paper. These data can be

obtained free of charge from The Cambridge Crystallographic

Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

7.37, 7.41 (2 d, J_HH= 7.7 Hz, 2ϫ1 H, Ar^iPrmЈ-CH) ppm.

3

C₃₈H₄₅MoN₃O₄(703.73): calcd. C 64.86, H 6.45, Mo 13.63, N

5.97; found C 64.07, H 6.60, Mo 13.35, N 5.77. IR: ν = 1895, 1790,

˜

1776 [ν(C=O)] 1615, 1597, 1576 [ν(C=N)] cm^–1. UV/Vis (dichloro-

methane): λ_max= 293 (π*ǟn, tailing into π*ǟπ), 444, 505 [shoul-

der (MLCT)] nm.

1k·Cr(CO)₃(2k): Ligand 1k (0.205 g, 0.000369 mol), Cr(CO)₆

(0.081 g, 0.000368 mol) and nBu₂O (10 mL) containing a few drops

of thf were heated to reflux for 2.5 h. Black powder (0.129 g, 51%).

Acknowledgments

3

¹H NMR (500 MHz, [D₆]dmso): δ = 0.44 (d, J_HH= 7.5 Hz, 3 H),

3

1.03 (d, J_HH= 6.7 Hz, 3 H), 1.10 (d, J_HH= 6.7 Hz, 3 H), 1.30

The Nuffield Foundation is thanked for provision of a Nuffield

Science Bursary (B. L.), The Engineering and Physical Sciences Re-

search Council for a research studentship (A. J.) and the grant of

synchrotron time at Daresbury Laboratories (F. S. M., J. E. W.).

F. S. M. is grateful to UMIST for granting a period of sabbatical

leave during which this research was initiated, and to the University

of Strathclyde for hosting it.

3

(d, J_HH= 6.7 Hz, 3 H), 1.45 (d, J_HH= 6.7 Hz, 3 H), 1.56 (d,

³J_HH= 6.7 Hz, 3 H) [6 CH(CH₃)₂], 2.14 (s, 3 H), 2.52 (s, 3 H,

3

CH₃C=N), 2.30 (sept, J_HH= 6.7 Hz, 1 H), 2.83 (sept, J_HH

=

3

6.7 Hz, 1 H), 2.98 (sept, J_HH= 6.7 Hz, 1 H, CH(CH₃)₂], 6.05 (s,

1 H, α-CH), 6.72–6.76 (non-first-order m, 2 H), 7.05–7.10 (non-

first-order m, 2 H), 7.18–7.30 (non-first-order m, 7 H), 7.33–7.39

(non-first-order m, 4 H), 7.42–7.47 (non-first-order m, 2 H, aro-

matic CH) ppm. C₄₂H₄₅CrN₃O₃(691.83): calcd. C 72.92, H 6.56,

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Cr 7.52, N 6.07; found C 72.62, H 6.67, Cr 7.30, N 6.00. IR: ν =

˜

1893, 1804, 1780 [ν(C=O)] 1620, 1597, 1579, 1557 [ν(C=N)] cm^–1.

UV/Vis (dichloromethane): λ_max= 290, 360 [shoulder (π*ǟn,

π*ǟπ)], 489, 610 (MLCT) nm.

1k·Mo(CO)₃(3k): Ligand 1k (0.201 g, 0.000362 mol), Mo(CO)₆

(0.095 g, 0.000360 mol) and nBu₂O (10 mL) containing a few drops

of thf were heated to reflux for 5 h. Very dark purple powder

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1

3

(0.196 g, 74%). H NMR (500 MHz, [D₆]dmso): δ = 0.30 (d, J_HH

3

= 6.9 Hz, 3 H), 0.83 (d, J_HH= 6.9 Hz, 3 H), 0.88 (d, J_HH

=

6.9 Hz, 3 H), 1.05 (d, ³J_HH= 6.9 Hz, 3 H), 1.20 (d, J_HH= 6.9 Hz,

3

3 H), 1.31 (d, J_HH= 6.9 Hz, 3 H) [6 CH(CH₃)₂], 1.91 (s, 3 H),

3

2.30 (s, 3 H) (2 CH₃C=N), 2.18 (sept, J_HH= 6.9 Hz, 1 H), 2.72

3

(sept, J_HH= 6.9 Hz, 1 H), 2.84 (sept, J_HH= 6.9 Hz, 1 H) [3

CH(CH₃)₂], 5.82 (s, 1 H, α-CH), 6.46–6.51 (non-first-order m, 2

H), 6.80–6.87 (non-first order m, 2 H), 6.94–7.24 (non-first-order

m, 13 H, aromatic CH) ppm. C₄₂H₄₅MoN₃O₃(735.78): calcd. C

68.56, H 6.16, Mo 13.04, N 5.71; found C 67.87, H 6.25, Mo 13.01,

N 5.59. IR: ν = 1898, 1802, 1779 [ν(C=O)] 1621, 1597, 1581, 1562

˜

[ν(C=N)] cm^–1. UV/Vis (dichloromethane): λ_max= 289, 360 [v. weak

shoulder (π*ǟn, π*ǟπ)], 462, 575 (MLCT) nm.

X-ray Crystallography: Crystals of 1a–1c, 2a and 3a suitable for

single-crystal X-ray diffraction were grown by vapour diffusion of

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(2a), or diethyl ether into acetone (3a) solutions. Mounting in oil

into an Oxford Instruments Cryostream direct from the mother

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isolated and allowed to dry fully, without any detrimental effects

to crystal quality, before being mounted in perfluoropolyether oil

on the diffractometer. For 1a–1c and 3a, diffraction intensities were

measured with the CCD of a Nonius Kappa diffractometer by

using graphite-monochromated Mo-K_αradiation. For 2a, a Bruker

APEX II diffractometer fitted to Station 9.8 of the Daresbury Syn-

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Published Online: February 5, 2009

Eur. J. Inorg. Chem. 2009, 1219–1233

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Article Doi

A new, flexible N,N,N-Tripodal facially capping ligand system: Synthesis and structural characterization of β-Triketimines and their M(CO) 3 complexes (M = Cr, Mo, W)

DOI: 10.1002/ejic.200801022

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