Synthesis, structures and reactivity of group 4 hydrazido complexes supported by calix[4]arene ligands

Inorg. Chem. 2008, 47, 12049-12062

Synthesis, Structures and Reactivity of Group 4 Hydrazido Complexes

Supported by Calix[4]arene Ligands

Andrew J. Clulow, Jonathan D. Selby, Michael G. Cushion, Andrew D. Schwarz,

and Philip Mountford*

Chemistry Research Laboratory, UniVersity of Oxford, Mansﬁeld Road, Oxford OX1 3TA, U.K.

Received September 9, 2008

Reaction of TiCl₂(Me₂Calix) with 2 equiv of LiNHNRR′ afforded the corresponding terminal hydrazido(2-) complexes

Ti(NNRR′)(Me₂Calix) (R ) Ph, R′ ) Ph (1) or Me; R ) R′ ) Me (3)) which were all structurally characterized.

The X-ray structure of Ph₂NNH₂is reported for comparison. Compound 1 was also prepared from Na₂[Me₂Calix]

and Ti(NNPh₂)Cl₂(py)₃. Reaction of ZrCl₂(Me₂Calix) with 2 equiv of LiNHNR₂afforded only the bis(hydrazido(1-))

complexes Zr(NHNR₂)₂(Me₂Calix) (R ) Ph or Me). Treatment of Ti(NNMe₂)(Me₂Calix) (3) with MeI gave the zwitterionic

hydrazidium species Ti(NNMe₃)(MeCalix) (6) via a net isomerization reaction which was found to be catalytic in

MeI. The corresponding reaction of 3 with CD₃I gave Ti(NNMe₂CD₃)(MeCalix) (6-d₃) with concomitant elimination

of MeI. Reaction of 3 with 1 equiv of MeOTf gave [Ti(NNMe₃)(Me₂Calix)][OTf] (7-OTf) which in turn reacted with

ⁿBu₄NI to form 6 and MeI. Addition of PhCHO to 3 gave the µ-oxo dimer [Ti(µ-O)(Me₂Calix)]₂and benzaldehyde-

dimethylhydrazone. Reaction of either 3 or 6 with ^tBuNCO gave the zwitterionic species Ti{^tBuNC(NNMe₃)O}(MeCalix)

(10) which has been crystallographically characterized. Compound 10 is the formal product of insertion of an

isocyanate into the TidN_Rbond of a titanium hydrazide or hydrazidium species (Me₂Calix or MeCalix ) dianion

or trianion of the di- or monomethyl ether of p-tert-butyl calix[4]arene, respectively).

Introduction

become interested in developing the chemistry of titanium

hydrazido complexes.^17-21This contribution describes our

recent results using calix[4]arenes as supporting ligands.

Although Wiberg reported the ﬁrst terminal titanium

hydrazido complex in 1978 (Cp₂Ti{NN(SiMe₃)₂}²²), the ﬁrst

structurally authenticated example was described only re-

cently by Odom, namely, Ti(dpma)(NNMe₂)(^tBubipy) (dpma

The chemistry of hydrazido complexes (L)MdNNR₂

continues to be of considerable interest, particularly in the

context of the biological and synthetic activation and ﬁxation

of dinitrogen.^1-9Although the structures, properties, and

reactivity of such compounds are well-established for the

Groups 5-7 transition metals, there remains a paucity of

examples for Group 4.¹⁰This is in contrast to the situation

for the apparently related imido complexes (L)MdNR (R

) alkyl or aryl) which are very well established for titanium

and zirconium in particular.^11-16In our group, we have

t

) N,N-di(pyrrolyl-R-methyl)-N-methylamine; Bubipy )

(12) Duncan, A. P.; Bergman, R. G. Chem. Rec. 2002, 2, 431.

(13) Odom, A. L. Dalton Trans. 2005, 225.

(14) Hazari, N.; Mountford, P. Acc. Chem. Res. 2005, 38, 839.

(15) Bolton, P. D.; Mountford, P. AdV. Synth. Catal. 2005, 347, 355.

(16) Fout, A. R.; Kilgore, U. J.; Mindiola, D. J. Chem. Eur. J. 2007, 13,

9428.

*

To whom correspondence should be addressed. E-mail:

philip.mountford@chem.ox.ac.uk.

(1) Fryzuk, M. D. Chem. Rec. 2003, 3, 2.

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(18) Parsons, T. B.; Hazari, N.; Cowley, A. R.; Green, J. C.; Mountford,

P. Inorg. Chem. 2005, 44, 8442.

(19) Selby, J. D.; Manley, C. D.; Felix, M.; Schwarz, A. D.; Clot, E.;

Mountford, P. Chem. Commun. 2007, 4937.

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Organometallics 2008, in press.

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C.; Mountford, P. Chem. Commun. 2008, 5103.

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111, 2708.

10.1021/ic801735c CCC: $40.75  2008 American Chemical Society

Inorganic Chemistry, Vol. 47, No. 24, 2008 12049

Published on Web 11/11/2008

Clulow et al.

5,5′-di-tert-butyl-2,2′-bipyridine).²³Since this report in 2004,

only a handful of other terminal titanium hydrazides have

been structurally characterized.^18-20,24,25Certain TidNNR₂

species have been implicated in the catalytic hydrohydrazi-

nation^23,26-32and iminohydrazination^24,31of alkynes and in

the synthesis of indoles^13,28,30and tryptamines.²⁹In these

reactions, a [2 + 2] cycloaddition reaction between

TidNNR₂and an alkyne (or allene) is considered to be the

key N-C bond forming step. Little is directly known about

these catalytic processes or the intermediates involved.

Very few papers have addressed the stoichiometric reac-

tions of titanium (or zirconium^33,34) hydrazides. We found

that the macrocycle-supported complex Ti(NNPh₂)(Me₄taa)

underwent [2 + 2] cycloaddition reactions of the TidN_R

bond with CO₂and p-tolyl isocyanate (Me₄taa ) dianion of

tetramethyl dibenzotetraaza[14]annulene).¹⁷Woo subse-

quently observed hydrazone formation on reaction of por-

phyrin-supported hydrazides with certain aldehydes³⁵via a

TidNNR₂/CdO metathesis reaction. Odom found that

Ti(dpma)(NNMe₂)(^tBubipy) reacted with MeI to form the

corresponding hydrazidium salt [Ti(dpma)(NNMe₃)-

(^tBubipy)]I via electrophilic attack at the hydrazido ꢀ-nitro-

gen.²³In all of these reactions the hydrazide N_R-N_ꢀbonds

remained intact. In constrast, we recently found that the

diamide-amine supported complex Ti(NNPh₂){MeN(CH₂-

CH₂NSiMe₃)₂}(py) reacted with MeCCR (R ) Me or Ph)

via an apparent insertion reaction into the N_R-N_ꢀbond.¹⁹

Possibly related N_R-N_ꢀbond cleavage chemistry has been

found for a couple of types of zirconium hydrazide.^33,34

To explore further the chemistry of the TidNNR₂func-

tional group we have been developing routes to new types

of titanium hydrazide complexes.¹⁹Ligand choices have been

guided by our and others experience from the area of Group

4 imido chemistry. Calixarene ligands (and in particular

calix[4]arenes) have been widely used platforms for coor-

dination, supramolecular and organometallic chemistry over

the past 10-15 years.^36-43In particular, such ligands have

been used for a range of metal-imido complexes of Group 4

(including reactions of TidNR multiple bonds with unsatur-

ated substrates)^44-46and one example of a Group 6 hy-

drazide(2-).⁴⁷In a recent communication we found that

[Ti(NNPh₂)Cl₂(py)₂]₂reacted with Na₂[Bn₂Calix] to form

Ti(NNPh₂)(Bn₂Calix) (Bn₂Calix ) dianion of 1,3-dibenzyl

ether of p-tert-butyl calix[4]arene).¹⁹No structure was

reported and no reactivity studies were carried out. In this

paper we build on these preliminary results using the related

Me₂Calix ligand (Me₂Calix ) dianion of 1,3-dimethyl ether

of p-tert-butyl calix[4]arene).

Results and Discussion

Synthesis of New Hydrazido(2-) and Hydrazido(1-)

Complexes. Building on our recent communication¹⁹we

found that reaction of Na₂[Me₂Calix] with monomeric

Ti(NNPh₂)Cl₂(py)₃in cold C₆H₆gave the terminal hydrazido

derivative Ti(NNPh₂)(Me₂Calix) (1) in 35% isolated yield

1

as a brown solid (eq 1). The H and ¹³C NMR spectra of 1

indicated the presence of a C_2vsymmetric Me₂Calix[4]arene

ligand on the NMR time scale, consistent with the solid state

X-ray structure discussed below.

The low yield of 1 by this method was disappointing. This

prompted us to seek a higher yielding and more versatile

route which could also lead to alternative terminal hy-

drazides. Terminal hydrazide synthons such as

Ti(NNPh₂)Cl₂(py)₃are not yet available for titanium with

dialkyl or monoalkyl NNR₂ligands. Although the dimeric

species Ti₂(µ-η¹:η²-NNMe₂)₂Cl₄(py)₄has been reported,¹⁸its

reactions with Na₂[Me₂calix] gave intractable mixtures.

Therefore we developed the route summarized in eq 2.

Reaction of the previously reported⁴⁶TiCl₂(Me₂Calix) with

2 equiv of the lithiated hydrazides LiNHNRR′ (R ) Ph, R′

) Ph or Me; R ) R′ ) Me) at 60 °C afforded the

corresponding terminal hydrazides Ti(NNRR′)(Me₂Calix) (R

) Ph, R′ ) Ph (1) or Me (2); R ) R′ ) Me (3)) in 75-91%

isolated yield along with 1 equiv of the corresponding

RR′NNH₂(observed when followed in C₆D₆). Analogous

dehydrohalogenative routes were used previously for the

corresponding imido complexes M(NR)(Me₂Calix) (M ) Ti

(23) Li, Y.; Shi, Y.; Odom, A. L. J. Am. Chem. Soc. 2004, 126, 1794.

(24) Banerjee, S.; Odom, A. L. Organometallics 2006, 25, 3099.

(25) Patel, S.; Li, Y.; Odom, A. L. Inorg. Chem. 2007, 46, 6373.

(26) Johnson, J. S.; Bergman, R. G. J. Am. Chem. Soc. 2001, 123, 2923.

(27) Cao, C.; Shi, Y.; Odom, A. L. Org. Lett. 2002, 4, 2853.

(28) Ackermann, L.; Born, R. Tetrahedron Lett. 2004, 45, 9541.

(29) Khedkar, V.; Tillack, A.; Michalik, M.; Beller, M. Tetrahedron Lett.

2004, 45, 3123.

(30) Tillack, A.; Jiao, H.; Garcia Castro, I.; Hartung, C. G.; Beller, M.

Chem. Eur. J. 2004, 10, 2410.

(31) Banerjee, S.; Shi, Y.; Cao, C.; Odom, A. L. J. Organomet. Chem.

2005, 690, 5066.

(32) Banerjee, S.; Barnea, E.; Odom, A. L. Organometallics 2008, 27, 1005.

(33) Walsh, P. J.; Carney, M. J.; Bergman, R. G. J. Am. Chem. Soc. 1991,

113, 6343.

(34) Herrmann, H.; Fillol, J. L.; Wadepohl, H.; Gade, L. H. Angew. Chem.,

Int. Ed. 2007, 46, 8426.

(35) Thorman, J. L.; Woo, L. K. Inorg. Chem. 2000, 39, 1301.

(36) Gutsche, C. D. Calixarenes; Royal Society of Chemistry: Cambridge,

1989.

46

t

or Zr, R ) Bu or certain aryl groups). The NMR spectra

(37) Bo¨hmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713.

(38) Bo¨hmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713.

(39) Roundhill, D. M. Prog. Inorg. Chem. 1995, 43, 533.

(40) Floriani, C.; Floriani-Moro, R. AdV. Organomet. Chem. 2001, 47, 167.

(41) Redshaw, C. Coord. Chem. ReV. 2003, 244, 45.

(42) Radius, U. Z. Anorg. Allg. Chem. 2004, 630, 957.

(43) Kotzen, N.; Vigalok, A. Supramol. Chem. 2008, 20, 129.

(44) Caselli, A.; Giannini, L.; Solari, E.; Floriani, C.; Re, N.; Chiesi-Villa,

A.; Rizzoli, C. Organometallics 1997, 16, 5457.

(45) Radius, U.; Friedrich, A. Z. Anorg. Allg. Chem. 1999, 625, 2154.

(46) Dubberley, S. R.; Friedrich, A.; Willman, D. A.; Mountford, P.; Radius,

U. Chem. Eur. J. 2003, 9, 3634.

(47) Redshaw, C.; Elsegood, M. R. Inorg. Chem. 2000, 39, 5164.

12050 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

Figure 1. Displacement ellipsoid plots (20% probability) with H atoms and solvent molecules of crystallization omitted for clarity. (a) Ti(NNPh₂)(Me₂Calix)

(1). (b) Ti{NN(Me)Ph}(Me₂Calix) (2).

of 2 and 3 were analogous to that of 1 and their X-ray

structures have also been determined (see below). The EI

mass spectra of 1 and 2 each showed the expected molecular

ions as well as peaks for [TiNN(Me)Ph₂]⁺and

[TiNN(Me₂)Ph]⁺, respectively; the EI-MS of 3 showed only

[TiNNMe₃]⁺as the highest m/z titanium fragment. The

formation of ꢀ-N-methylated fragments (potentially arising

from transfer of a calix[4]arene O-Me group) may be relevant

to the attempted alkylations and other reactions described

later in this paper.

derivatives Zr(NHR)₂(Me₂Calix), and only with the sterically

demanding LiNHAr (Ar ) 2,6-C₆H₃Pr₂) was a terminal

i

imide Zr(NAr)(Me₂Calix) and free ArNH₂formed.⁴⁶It

appears that the hydrazines used in our studies to date are

insufﬁciently bulky to promote formation of terminal hy-

drazido(2-) zirconium complexes. Nonetheless, zirconium

hydrazido(1-) species are relatively uncommon³³and have

been structurally characterized only very recently, this being

for a κ²- coordinated NHNMe₂moiety.⁴⁸The spectroscopic

data do not distinguish between κ¹- or κ²- coordinated

NHNR₂ligands in the case of 4 or 5.

Gade has shown that the zirconium hydrazides

Zr(NNRR′)(N₂N^py)(L) (R ) Ph, R′ ) Ph or Me; L ) py or

DMAP; N₂N^pyis a diamide-amine ligand) can be obtained

via treatment of the mono(chloride), mono(hydrazido(1-))

species Zr(NHNRR’)Cl(N₂N^py) with Li[N(SiMe₃)₂] in the

presence of the donor L.^34,48We have attempted to obtain

analogous hydrazide(1-)-chloride complexes of the type

Zr(NHNR₂)Cl(Me₂Calix) (R ) Ph or Me) starting from

ZrCl₂(Me₂Calix) and 1 equiv of LiNHNR₂. In each case a

mixture containing the bis(hydrazido(1-)) species (4 or 5)

was ultimately obtained. In the reaction of ZrCl₂(Me₂Calix)

Reactions of LiNHNPh₂and LiNHNMe₂with

ZrCl₂(Me₂Calix) have also been carried out using analogous

methods (eq 3). In each of these cases the bis(hydrazido-

(1-)) compounds Zr(NHNR₂)₂(Me₂Calix) (R ) Ph (4) or Me

(5)) were obtained as the only products. The NMR spectra

were again consistent with C_2vsymmetric species and the

IR spectra showed characteristic ν(N-H) bands. Heating

these compounds either in the presence or in the absence of

a base (e.g., DMAP) failed to promote elimination of

H₂NNR₂to afford terminal hydrazide(2-) derivatives. We

note that in the corresponding imido chemistry, reaction of

ZrCl₂(Me₂Calix) with LiNH^tBu or LiNHPh gave bis(amido)

(48) Herrmann, H.; Wadepohl, H.; Gade, L. H. Dalton Trans. 2008, 2111.

Inorganic Chemistry, Vol. 47, No. 24, 2008 12051

Clulow et al.

and associated parameters are comparable to those reported

previously for titanium calix[4]arene complexes.^46,53-55

There are no signiﬁcant differences between the three

structures in these regards.

The principal structural interest in 1-3 is the TidNNRR′

functional group and how the bond parameters change with

the N_ꢀsubstituents. Several structural reports of terminal

TidNNPh₂groups have now appeared (seven ex-

amples).^18-20The TidN_Rdistances span the range 1.718(2)-

1.751(1) Å (avg. 1.737 Å) and the N_R-N_ꢀdistances span

the range 1.353(2)-1.369(3) Å (avg. 1.362 Å). The mono(phe-

nyl) hydrazide Ti{NN(H)Ph}(dmpa)(^tBubipy) has also been

structurally characterized (TidN_R1.712(4), N_R-N_ꢀ1.350(5)

Å).²⁵There have been three structural reports of terminal

Ti)NNMe₂groups: Ti(NNMe₂)(dpma)(^tBubipy) (TidN_R

1.708(3), N_R-N_ꢀ1.388(4) Å),²³Cp*Ti(NNMe₂)-

{MeC(NⁱPr)₂} (TidN_R1.723(2), N_R-N_ꢀ1.386(2) Å),¹⁹and

Ti(NNMe₂)(dap){^tBuNCHCHC(ⁿBu)NNMe₂}(TidN_R1.709(3),

N_R-N_ꢀ1.403(4)Å;dap)2-(dimethylaminomethyl)pyrrolyl).²⁴

Within these groups of compounds there appears to be no

discernible trend in TidN_Rdistances, while the TidN_R-N_ꢀ

angles are all approximately linear (range ca. 160-178°).

However, the large variation in supporting ligand set could

easily lead to signiﬁcant differences in individual TidN_R

values, masking any effects of the N_ꢀsubstituents. Within

the NNR₂units themselves the N_R-N_ꢀdistances for the

NNPh₂and NN(H)Ph species appear to be shorter than for

the NNMe₂systems. The N_ꢀfor the two NNPh₂species are

effectively planar (sums of angles subtended at N_ꢀca.

357-360°), whereas for the NNMe₂compounds the N_ꢀis

highly pyramidalized with sums of angles at N_ꢀin the range

ca. 334-337°.⁵⁶

The homologous series 1-3 provides the ﬁrst systematic

comparison of the bond parameters of phenyl, alkyl and

mixed aryl/alkyl N_ꢀ-substituted hydrazides within the same

supporting ligand framework. The TidNNRR′ linkages are

all effectively linear and the range of values for TidN_R-N_ꢀ

is 170.4(4) to 177.3(2)°. The N_ꢀatom (N(2)) for 3 is

pyramidalized (sum of angles 338(2)°), whereas in 1 and 2

it is planar (sum of angles 360(1)°). As suggested by Odom,²⁵

this appears to be due to conjugation between N_ꢀand the

phenyl rings. In 2 the N_ꢀ-Me and N_ꢀ-Ph distances are

1.450(5) and 1.397(4) Å, respectively, and the Ph ring is

effectively coplanar with Ti(1)-N(1)-N(2) to within 1 to 2

degrees. The N_ꢀ-Ph distances in 1 are slightly longer since

the phenyl rings are more twisted out of coplanarity by ca.

10-20° for steric reasons.

Figure 2. Displacement ellipsoid plot (20% probability) of

Ti(NNMe₂)(Me₂Calix) (3). H atoms and toluene molecules of crystallization

are omitted for clarity.

Table 1. Selected Bond Distances (Å) and Angles (°) for

Ti(NNPh₂)(Me₂Calix) (1), Ti{NN(Me)Ph}(Me₂Calix) (2), and

Ti(NNMe₂)(Me₂Calix) (3)

1

2

3

Ti(1)-N(1)

1.717(2)

1.352(3)

1.418(3)

1.422(3)

2.142(2)

2.144(2)

1.849(2)

1.885(2)

1.727(3)

1.344(2)

1.450(5)

1.397(4)

2.150(2)

2.155(2)

1.874(2)

1.857(2)

1.729(4)

1.373(6)

1.448(10)

1.421(9)

2.166(3)

2.147(3)

1.883(3)

1.861(3)

N(1)-N(2)

N(2)-C(1)

N(2)-C(2)/C(7)^a

Ti(1)-O(1)

Ti(1)-O(2)

Ti(1)-O(3)

Ti(1)-O(4)

Ti(1)-N(1)-N(2)

N(1)-N(2)-C(2)/C(7)^a

C(1)-N(2)-C(2)/C(7)^a

O(1)-Ti(1)-O(2)

O(3)-Ti(1)-O(4)

177.3(2)

175.8(3)

170.4(4)

116.6(2)

118.4(2)

125.0(2)

165.3(6)

134.1(8)

118.1(3)

120.5(3)

121.4(3)

164.2(8)

131.9(1)

111.5(6)

113.9(5)

112.5(6)

162.5(1)

125.9(2)

^aC(2) for Ti{NN(Me)Ph}(Me₂Calix) (2) and Ti(NNMe₂)(Me₂Calix) (3);

C(7) for Ti(NNPh₂)(Me₂Calix) (1).

1

with LiNHNPh₂, minor H NMR resonances indicating C_s

symmetry were tentatively assigned to

a

species

Zr(NHNPh₂)Cl(Me₂Calix), but these disappeared over several

hours with an increase in the intensity of those for the starting

ZrCl₂(Me₂Calix) and the bis(hydrazide(1-)) 4.

Structural Investigations. As mentioned, the X-ray

structures of Ti(NNRR′)(Me₂Calix) (R ) Ph, R′ ) Ph (1)

or Me (2); R ) R′ ) Me (3)) have all been determined.

Views of the complexes are given in Figures 1 and 2, and

key distances and angles are compared in Table 1.

All three compounds contain a 5-coordinate titanium center

possessing an approximately trigonal bipyramidal geometry.

The hydrazido N_Ratom and the two Me₂Calix anionic

phenolate O donors occupy the equatorial sites and the ether

O-donors the apical positions. An analogous geometry was

found for Ti(N^tBu)(Me₂Calix)⁴⁶and for Group 4 imido

bis(phenolate) complexes Ti(NR)(OAr)₂(L)₂in general.^49-52

The Ti-O distances for the Ti(Me₂Calix) fragments in 1-3

The TidN_Rdistances all lie in the range expected for

titanium-nitrogen multiple bonds and are comparable to

those previously found (see above). They can be compared

(52) Collier, P. E.; Blake, A. J.; Mountford, P. J. Chem. Soc., Dalton Trans.

1997, 2911.

(53) Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, &31.

(54) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. Chem. Inf. Comput.

Sci. 1996, 36, 746 The United Kingdom Chemical Database Service.

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Chem. Soc. 1985, 107, 8087.

(49) Hill, J. E.; Proﬁlet, R. D.; Fanwick, P. E.; Rothwell, I. P. Angew.

Chem., Int. Ed. Engl. 1990, 29, 664.

(50) Proﬁlet, R. D.; Zambrano, C. H.; Fanwick, P. E.; Nash, J. J.; Rothwell,

I. P. Inorg. Chem. 1990, 29, 4362.

(51) Zambrano, C. H.; Proﬁlet, R. D.; Hill, J. E.; Fanwick, P. E.; Rothwell,

I. P. Polyhedron 1993, 12, 689.

(56) The N_ꢀ-bound H for Ti{NN(H)Ph}(dmpa)(^tBubipy) was not located,

but the N_R-N_ꢀ-Ph angle (123.2(4)°) is indicative of a trigonal planar

geometry.

12052 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

to the ranges found for titanium imido complexes: TidN^tBu

range ca. 1.66 - 1.74 Å (mean ca. 1.70 Å); TidNAr range

ca. 1.69-1.76 Å (mean ca. 1.72 Å).^53,54The TidN^tBu

distance in Ti(N^tBu)(Me₂Calix) is 1.706(2) Å.⁴⁶The N_R-N_ꢀ

distances in 1 (1.352(3) Å) and 3 (1.373(6) Å) appear a little

shorter than in previous complexes with TidNNPh₂and

TidNNMe₂groups.

18

DFT calculations for Ti(NNPh₂){HC(Me₂pz)₃}Cl₂and

other compounds^20,25have suggested that NNR₂groups

bound to titanium are best considered as “hydrazide(2-)”

ligands, [N-NR₂]^2-, as opposed to neutral isodiazenes

(:NdNR₂), which is more typically the case for later

transition metals.^57-60Calculations have also suggested that

[N-NH₂]^2-should possess a long N_R-N_ꢀbond (1.57 Å) and

highly pyramidal N_ꢀ, while singlet isodiazene (:NdNH₂) is

predicted to be planar with a N_R-N_ꢀdistance of 1.23 Å.⁶¹

Based on the structural data compounds 1-3 are clearly

hydrazide(2-) species with the inherent tendency for N_ꢀ

pyramidalization suppressed by conjugation with the phenyl

group(s).

The differences between the TidN_Rdistances for 1 or 2

and that for 3 (0.012(4) and 0.002(5) Å, respectively) are at

or below the limits of statistical signiﬁcance at the 3σ level.

Likewise there is no signiﬁcant difference between the

TidN_Ror N_R-N_ꢀdistances for 1 and 2. However, the

differences between N_R-N_ꢀdistances for 1 and 2 (both

possessing a planar N_ꢀ) and 3 are indicative of a lengthening

of this bond (∆N_R-N_ꢀ) 0.021(7) or 0.029(6) Å) upon

pyramidalization of N_ꢀ, and are consistent in this regard with

the literature data mentioned above.

Figure 3. Displacement ellipsoid plot (20% probability) of one of the two

independent molecules of Ph₂NNH₂in the asymmetric unit. C-bound H

atoms omitted for clarity. H atoms drawn as sphere of arbitrary radius.

perturb the geometric features. Interestingly, Ph₂NNH₂

contains a pyramidal N_R(sp³hybridized) atom and a trigonal

planar N_ꢀ(sp², sum of angles 357.9(4)°). The N_ꢀ-Ph

distances are within the range spanned by 1 and 2, consistent

with signiﬁcant conjugation. The N-N single bond in

Ph₂NNH₂(1.418(2) Å) is shorter than that in Me₂NNH₂

(1.436(2) Å). Furthermore, the difference between N_R-N_ꢀ

values in these two organic species (∆N_R-N_ꢀ) 0.018(3)

Å) is the same within error as that between 1 and 3 (∆N_R-N_ꢀ

) 0.021(7) Å) or 2 and 3 (∆N_R-N_ꢀ) 0.029(6) Å).

Therefore any discussions of differences between TidNNPh₂

and TidNNMe₂group N_R-N_ꢀbond lengths should take into

account variations in single bond radii on changing from sp²

to sp³hybridization for N_ꢀ. Depending upon individual cases,

these hybridization effects could make a major contribution

to observed bond length variations.

In general terms the N_R-N_ꢀdistances in 1-3 lie in

between those expected for NdN double (ca. 1.22-1.26 Å)

and N-N single (ca. 1.40-1.45 Å) bonds.^53,54,62Note that

these N-N single bond averages vary signiﬁcantly depending

on the formal hybridization of the nitrogen (N(sp²)-N(sp²)

< N(sp²)-N(sp³) < N(sp³)-N(sp³)). The experimental

N_R-N_ꢀdistance in Me₂NNH₂(both nitrogens formally sp³

hybridized) is 1.436(2) Å,⁶³and is clearly much longer than

the N_R-N_ꢀdistance in 3.

To make a better comparison between TidNNPh₂and

TidNNMe₂distances and those of the free hydrazines we

have determined the X-ray structure of Ph₂NNH₂. The

molecular strucuture is shown in Figure 3 and selected

distances and angles for the two crystallographically inde-

pendent molecules are given in Table 2. There are no

signiﬁcant differences between the two molecules and we

will refer to one set of values. Similarly, there are no

supramolecular (e.g., H-bonding) interactions which could

Reactivity Studies: Alkylating Agents. As mentioned in

the introduction, few reactivity studies of titanium hydrazides

have been reported. Encouraged by the success of Me₂Calix

as a supporting ligand platform in reactivity studies of

Ti(NR)(Me₂Calix) we screened the hydrazides 1-3 against

a range of substrates, starting with alkylating agents.

Odom has reported alkylation reactions of terminal hy-

drazides to form the corresponding hydrazidium complexes

[(L)TidNNR₂R′]⁺.^23,25Analogous reactions have been re-

ported for other transition metal hydrazides.⁶⁴We found that

none of 1-3 reacted with MeI at room temperature. In the

case of 1 and 2 no reaction occurred even after heating at

100 °C for 16 h. However, heating a sample of

Ti(NNMe₂)(Me₂Calix) (3) with an excess of MeI at 100 °C

for 20 min gave conversion to a new product 6 as a pale

1

orange solid. The H NMR spectrum of 6 featured three

resonances attributed to t-butyl groups of a calix[4]arene

ligand in a relative ratio of 9:9:18 H, along with four doublets

for the calix[4]arene methylene linkages between ca. 3.5 and

5.5 ppm. A singlet of relative intensity 9 H at 2.75 ppm was

(57) Stephan, G. C.; Sivasankar, C.; Studt, F.; Tuczek, F. Chem. Eur. J.

2008, 14, 644.

(58) Studt, F.; Tuczek, F. Angew. Chem., Int. Ed. 2005, 44, 5639.

(59) Mersmann, K.; Horn, K. H.; Bores, N.; Lehnert, N.; Studt, F.; Paulat,

F.; Peters, G.; Ivanovic-Burmazovic, I.; van Eldik, R.; Tuczek, F.

Inorg. Chem. 2005, 44, 3031.

(60) Lehnert, N.; Tuczek, F. Inorg. Chem. 1999, 38, 1671.

(61) Kahlal, S.; Saillard, J.-Y.; Hamon, J.-R.; Manzur, C.; Carrillo, D.

J. Chem. Soc., Dalton Trans. 1998, 1229.

(62) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.;

Taylor, R. J. Chem Soc. Perkin Trans. II 1987, S1.

(63) Litvinov, O. A.; Ermolaeva, L. V.; Zverev, V. V.; Naumov, V. A. J.

Struct. Chem. 1989, 30, 224.

+

consistent with a TidNNMe₃moiety, but the O-Me

resonance at 4.03 ppm integrated as only 3 H compared to

the other groups. Overall these and other data were not

consistent with the expected product of N_ꢀmethylation,

namely, [Ti(NNMe₃)(Me₂Calix)]I containing a C_2Vsymmetric

cation isoelectronic with Ti(N^tBu)(Me₂Calix). Compound 6

(64) Vale, M. G.; Schrock, R. R. Inorg. Chem. 1993, 32, 2767.

Inorganic Chemistry, Vol. 47, No. 24, 2008 12053

Clulow et al.

a

Table 2. Selected Bond Distances (Å) and Angles (°) for Ph₂NNH₂

N(1)-N(2)

1.418(2) [1.415(2)]

1.411(2) [1.406(2)]

1.401(2) [1.408(2)]

N(1)-H(1)

N(1)-H(2)

0.94(3) [0.97(3)]

0.97(3) [0.94(3)]

N(2)-C(1)

N(2)-C(7)

N(1)-N(2)-C(1)

N(1)-N(2)-C(7)

C(1)-N(2)-C(7)

114.19(13) [114.86(13)]

119.95(14) [119.61(14)]

123.71(13) [124.49(13)]

N(2)-N(1)-H(1)

N(2)-N(1)-H(2)

H(1)-N(1)-H(2)

106(2) [106.4(14)]

111(2) [112(2)]

114(2) [105(2)]

^aValues in brackets are for the other crystallographically independent molecule.

1

2

Scheme 1. Reactions Leading to Ti(NNMe₃)(Me₂Calix) (6) and

Proposed Mechanism for the Reaction with MeI

out with CD₃I the H and D spectra were consistent with

the formation of Ti{NN(Me₂)CD₃}(MeCalix) (6-d₃) and the

¹H NMR spectrum showed the formation of 1 equiv of

natural abundance MeI. Compound 6-d₃did not scramble

the CD₃label into the MeCalix over time in solution.

Furthermore, exposure of 6 to CD₃I did not lead to

2

incorporation of CD₃into the complex (as judged by H

NMR spectroscopy) showing that the formation of 6 from

the intermediate 7⁺(Scheme 1) is irreversible.

Further attempts to extend and probe this novel catalytic

demethylation of 6 were carried out. Reaction of 3 with 3

equiv of PhCH₂Br in C₆D₆gave (according to NMR data)

the corresponding zwitterion Ti{NN(Me₂)CH₂Ph}(MeCalix)

(8) after 16 h at 60 °C. Using a smaller excess of PhCH₂Br

led to a small amount of 6 also being formed, presumably

due to reaction of 3 with the eliminated MeBr. Unfortunately,

attempts to obtain a pure sample of 8 on the preparative scale

were unsuccessful, giving only mixtures of products. Reac-

tion of 3 with Me₂SO₄(1 equiv) on the NMR tube scale

immediately gave a new Me₂Calix-containing product, but

this was found to be the previously reported µ-oxo dimer

Ti₂(µ-O)₂(Me₂Calix)₂.⁴⁶

Reaction of 3 with MeOTf in C₆D₆was more successful

(Scheme 1), and a C_2Vsymmetric species, [Ti(NN-

Me₃)(Me₂Calix)][OTf] (7-OTf), was formed quantitatively.

Attempts to isolate 7-OTf on the preparative scale were

complicated by the ready formation of mixtures, among

which Ti₂(µ-O)₂(Me₂Calix)₂was again present, presumably

due to TidN/SdO metathesis side-reactions. However,

reaction of a concentrated solution of 3 with MeOTf in C₆H₆

gave a precipitate of pure 7-OTf (albeit in low yield) which

could be successfully characterized. Although the ¹⁹F NMR

spectrum of 7-OTf does not unambiguously eliminate OTf^-

anion coordination (free and coordinated OTf^-have very

is in fact the zwitterionic hydrazidium complex

Ti(NNMe₃)(MeCalix) containing a trianionic, monomethyl

calix[4]arene ligand.

Scheme 1 illustrates the proposed structure of 6 and a

likely mechanism for formation. Demethylation reactions of

Ti-bound Me₂Calix to form MeCalix have been reported

previously, for example, for TiCl₂(Me₂Calix)⁶⁵and

46

t

Ti(OAr)₂(Me₂Calix) (Ar ) p-Tol or 4-C₆H₄Bu). The

proposed intermediate [Ti(NNMe₃)(Me₂Calix)]⁺(7⁺) is not

observed under the reaction conditions but, as mentioned, is

isoelectronic with the previously reported t-butyl imide

Ti(N^tBu)(Me₂Calix). Scheme 1 also implies that the trans-

formation of 3 to 6 should not appear to consume MeI, and

several NMR tube scale reactions have been carried out to

probe this.

When the reaction between 3 and MeI was followed by

¹H NMR spectroscopy the resonance for MeI did not

diminish. Treating 3 with 0.12 equiv of MeI also led to

quantitative conversion to 6, again without decrease in

intensity of the MeI resonance. When the reaction was carried

(65) Zanotti-Gerosa, A.; Solari, E.; Giannini, L.; Floriani, C.; Re, N.; Chiesi-

Villa, A.; Rizzoli, C. Inorg. Chim. Acta 1998, 270, 298.

12054 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

trimethyl calix[4]arene ligand in a partial cone conformation.

The Me₃Calix ligand is formed by O-methylation of the

Me₂Calix moiety in Ti(NNMe₂)(Me₂Calix) (3) or

[Ti(NNMe₃)(Me₂Calix)][OTf] (7-OTf). 9-OTf is the ﬁrst

structurally characterized example of a metal complex of

Me₃Calix although the protio-form of the ligand itself has

previously been the subject of an X-ray diffraction study.⁶⁹

The titanium coordination sphere is completed by a mono-

dentate OTf ligand and a trimethyl hydrazidium ligand. The

additional [OTf]^-anion makes no signiﬁcant contact to the

9⁺cation.

Figure 4. Displacement ellipsoid plot (20% probability) of

[Ti(NNMe₃)(Me₃Calix)(OTf)][OTf] (9-OTf). H atoms, [OTf]^-anion, and

benzene molecules of crystallization are omitted for clarity.

Table 3. Selected Bond Distances (Å) and Angles (°) for

[Ti(NNMe₃)(Me₃Calix)(OTf)]⁺(9⁺)

Ti(1)-O(1)

2.135(3)

2.139(3)

2.301(2)

1.794(3)

1.424(3)

99.93(13)

100.09(13)

172.94(13)

108.7(3)

Ti(1)-O(5)

2.079(3)

1.705(3)

1.418(4)

1.486(3)

1.432(3)

102.47(14)

94.89(13)

165.6(3)

110.1(3)

The compound 9-OTf is the second structurally character-

ized example of a Group 4 alkyl hydrazidium complex, the

other being [Ti(dpma)(NNMe₃)(^tBubipy)]I²³(examples from

the later metals are better established^53,54). The TidN_Rand

N_R-N_ꢀdistances of 1.705(3) and 1.418(4) Å in 9⁺are the

same within error to those in this previous example. The

TidN_Rdistance in 9⁺is shorter than in 3 (1.729(4) Å) while

the N_R-N_ꢀdistance is longer (1.373(6) Å in 3). Although

there are signiﬁcant changes in the supporting ligand set

between neutral, 5-coordinate Ti(NNMe₂)(Me₂Calix) (3) and

cationic [Ti(NNMe₃)(Me₃Calix)(OTf)]⁺(9⁺) which could in

principle perturb the bonding parameters of the Ti)NNMe₃

group, we note that analogous variations in TidN_Rand

N_R-N_ꢀdistances were found by Odom on going from neutral

Ti(dpma)(NNMe₂)(^tBubipy) to cationic [Ti(dpma)(NNMe₃)-

(^tBubipy)]⁺(both complexes being 6-coordinate). There are

several likely origins for the relative shortening and length-

ening of the TidN_Rand N_R-N_ꢀdistances between

(L)TidNNMe₂and (L′)TidNNMe₃⁺species, including loss

of any residual N_R-N_ꢀmultiple bond character and elec-

trostatic repulsion between N_Rand the formally cationic N_ꢀ.

Reactivity Studies: Unsaturated Substrates. As men-

tioned, 5-coordinate, macrocycle-supported titanium hy-

drazido complexes have been shown to undergo successful

[2 + 2] cycloaddition reactions with TolNCO and CO₂,¹⁷

and also TidNNR₂/CdO metathesis reactions with certain

aldehydes.³⁵In order to try to develop the underexplored

chemistry of the TidNNR₂functional group we have

screened the reactions of 1-3 with a range of unsaturated

substrates including CO₂, CS₂, alkyl- and aryl-isocyanates,

nitriles, isonitriles and internal and terminal alkynes under

a range of conditions. Regrettably almost all of these

reactions gave either rather complex mixtures or (particularly

Ti(1)-O(2)

Ti(1)-N(1)

Ti(1)-O(3)

N(1)-N(2)

Ti(1)-O(4)

S(1)-O(5)

S(1)-O(6)

S(1)-O(7)

N(1)-Ti(1)-O(1)

N(1)-Ti(1)-O(2)

N(1)-Ti(1)-O(3)

N(1)-N(2)-C(1)

N(1)-N(2)-C(3)

N(1)-Ti(1)-O(4)

N(1)-Ti(1)-O(5)

Ti(1)-N(1)-N(2)

N(1)-N(2)-C(2)

108.9(3)

similar ¹⁹F shifts^66,67), its infrared spectrum is consistent with

a free OTf^-anion as indicated by strong, broad bands

between 1260 and 1295 cm^-1.⁶⁸Attempts to observe 7⁺by

electrospray mass spectrometry were unsuccessful.

The compound 7-OTf is the triﬂate analogue of the

proposed intermediate (7-I, Scheme 1) in the reaction of 3

with MeI to form Ti(NNMe₃)(Me₂Calix) (6). Consistent with

this mechanism, we found that heating an NMR sample of

n

7-OTf with Bu₄NI for 60 min gave clean conversion to 6

and free MeI.

During our attempts to isolate 7-OTf, a few diffraction-

quality crystals of the new compound 9-OTf were obtained.

These contain the cation [Ti(NNMe₃)(Me₃Calix)(OTf)]⁺(9⁺)

and a noncoordinated [OTf]^-anion. The molecular structure

of 9⁺is shown in Figure 4 and selected distances and angles

are listed in Table 3. 9-OTf is the product of the reaction of

3 with 2 equiv of MeOTf. Attempts to isolate pure 9-OTf

on a preparative scale were unsuccessful, and a mixture of

products were formed when the reaction between isolated

7-OTf and MeOTf was followed by NMR.

The 9⁺cation contains an approximately octahedral

titanium center coordinated to a formally monoanionic

(66) Male, N. A. H.; Skinner, M. E. G.; Bylikin, S. Y.; Wilson, P. J.;

Mountford, P.; Schro¨der, M. Inorg. Chem. 2000, 39, 5483.

(67) Yi, X.-Y.; Williams, I. D.; Leung, W.-H. J. Organomet. Chem. 2006,

691, 1315.

(68) Liu, S.-Y.; Maunder, G. H.; Sella, A.; Stevenson, M.; Tocher, D. A.

Inorg. Chem. 1996, 35, 76.

(69) Grootenhuis, P. D. J.; Kollman, P. A.; Groenen, L. C.; van Hummel,

G. J.; Ugozzoli, F.; reetti, G. D. J. Am. Chem. Soc. 1990, 112, 4165.

Inorganic Chemistry, Vol. 47, No. 24, 2008 12055

Clulow et al.

in the case of 1 and 2) no reaction under forcing conditions.

In two instances, however, reasonably well-deﬁned reactions

were observed.

Figure 5. Displacement ellipsoid plot (20% probability) of

Ti{^tBuNC(NNMe₃)O}(MeCalix) (10). H atoms and benzene molecules of

crystallization are omitted for clarity.

Reaction of Ti(NNMe₂)(Me₂Calix) (3) with benzaldehyde

gave quantitative conversion by ¹H NMR to benzaldehyde-

dimethylhydrazone (mixture of isomers⁷⁰) at room temper-

ature after 16 h (eq 4). However, complex mixtures were

observed with acetophenone upon heating (no reaction

occurred at room temperature) and no reaction occurred with

benzophenone. No reaction occurred between 1 and benzal-

dehyde at room temperature and upon heating a complex

mixture was formed. The side-product of the reaction of 3

with PhCHO was Ti₂(µ-O)₂(Me₂Calix)_2.The metathesis

reaction in eq 4 probably proceeds via a [2 + 2] cycload-

dition reaction and intermediate Ti{OC(H)PhNNMe₂}-

(Me₂Calix) (3-PhCHO-int). Adducts of this type have been

observed previously in titanium imido chemistry.⁷¹Under

these reaction conditions, no Me₂Calix demethylation prod-

ucts were observed.

Table 4. Selected Bond Distances (Å) and Angles (°) for

Ti{^tBuNC(NNMe₃)O}(MeCalix) (10)

Ti(1)-O(1)

2.326(3)

1.907(3)

1.839(3)

1.815(3)

2.054(3)

2.019(4)

105.3(2)

167.4(1)

65.0(2)

N(3)-C(5)

C(4)-N(1)

C(4)-O(5)

C(4)-N(3)

N(1)-N(2)

1.462(7)

1.318(7)

1.330(6)

1.359(6)

1.477(6)

Ti(1)-O(2)

Ti(1)-O(3)

Ti(1)-O(4)

Ti(1)-O(5)

Ti(1)-N(3)

O(3)-Ti(1)-O(4)

O(1)-Ti(1)-O(2)

N(3)-Ti(1)-O(5)

C(4)-N(3)-C(5)

N(1)-C(4)-O(5)

N(1)-C(4)-N(3)

C(4)-N(1)-N(2)

127.9(4)

123.0(5)

113.5(4)

123.5(4)

solution. The molecular structure is shown in Figure 5 and

important bond distances and angles are presented in Table

4.

Reactions of 3 with arylisocyanates at room temperature

Compound 10 is another zwitterionic species containing

a demethylated MeCalix ligand. The Ti(MeCalix) fragment

is coordinated to a κ(N,O)-bound ^tBuNC(NNMe₃)O ligand.

The latter features an exocyclic NNMe₃⁺group, presumably

formed by demethylation of Me₂Calix by the TidNNMe₂

at some stage of the reaction (see below). Note that the

assignment of the N(1) and N(3) substituents as NMe₃⁺and

the isoelectronic CMe₃(as shown in Figure 5) is consistent

gave immediate formation of complex mixtures. However,

t

reaction with BuNCO at 70 °C gave modest yields of

Ti{N^tBuC(NNMe₃)O}(MeCalix) (10) (eq 5). Diffraction-

quality crystals of 10 were obtained from a saturated benzene

(70) Petroski, R. J. Synth. Commun. 2006, 36, 1727.

(71) Guiducci, A. E.; Boyd, C. L.; Mountford, P. Organometallics 2006,

25, 1167.

12056 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

Scheme 2. Two Possible Mechanisms for the Formation of Ti{^tBuNC(NNMe₃)O}(MeCalix) (10) from Ti(NNMe₂)(Me₂Calix) (3)

with the computed displacment parameters for N(2) and C(5).

The solution NMR spectra and other data (2D NOESY) for

10 are consistent with the X-ray structure.

t

The BuNC(NNMe₃)O moiety (or its homologues) in 10

has not been strucurally authenticated before. It is related to

well-known ureate ligands RNC(O)NR′ (which can be

κ(N,O) or κ(N,N’)-bound), formed, for example, by cycload-

dition of carbodiimides to MdO bonds or isocyanate addition

to MdNR bonds.^12,14,17A related and structurally authen-

t

ticated precedent for the BuNC(NNMe₃)O ligand in 10 is

the κ(N,O)-Me₂NC(NNMe₂)O moiety in Si{Me₂-

NC(NNMe₂)O}₂Ph₂.⁷²A closely related (isoelectronic) ex-

ample from titanium ureate chemistry is Ti{κ(N,O)-

bond of a hydrazidium complex appears to be a new reaction

type. Typically hydrazidium complexes undergo reductive

cleavage of the N_R-N_ꢀbond.^8,9Although the reaction in eq

6 is far from well-behaved, it does suggest that early metal

^tBuNC(N^tBu)O}(Me₄taa) formed from ^tBuNCO and

17

t

Ti(N^tBu)(Me₄taa). The BuNC(NNMe₃)O ligand in 10 is

the N_ꢀ-methylated homologue of the TolNC(O)NNPh₂

moiety formed when Ti(NNPh₂)(Me₄taa) reacts with TolNCO

to give Ti{TolNC(O)NNPh₂}(Me₄taa).¹⁷

+

hydrazidium complexes (L)MdNNR₃could have MdN_R

bond coupling chemistry with unsaturated substrates of the

type well-established for the isoelectronic imides (L)MdNCR₃.

Scheme 2 outlines two potential mechanisms for the

formation of 10 from 3. The upper pathway proceeds via an

Compound 10 could also be formally viewed as the

product of the net insertion of ^tBuNCO into the TidNNMe₃

+

bond of Ti(NNMe₃)(MeCalix) (6). To test this experimentally

we carried out the reaction of 6 with ^tBuNCO on the NMR

t

initial [2 + 2] cycloaddition with BuNCO which is well-

1

tube scale. After 1 h the H NMR spectrum showed 70%

established in imido chemistry and observed previously for

the reaction of Ti(NNPh₂)(Me₄taa) with TolNCO or CO₂.

Formation of PhCH(NNMe₂) from 3 and PhCHO (eq 4)

probably also proceeds via a [2 + 2] cycloaddition species

(3-PhCHO-int). Migration of a Me₂Calix O-methyl group

to the N_ꢀof intermediate 10-int would generate 10-K(N,N)

conversion of 6 to 10 along with minor unknown products

(eq 6). This formal insertion of a substrate into the TidN_R

(72) Kalikhman, I.; Gostevskii, B.; Botoshansky, M.; Kaftory, M.; Tessier,

C. A.; Panzner, M. J.; Youngs, W. J.; Kost, D. Organometallics 2006,

25, 1252.

Inorganic Chemistry, Vol. 47, No. 24, 2008 12057

Clulow et al.

Table 5. X-ray Data Collection and Processing Parameters for Ti(NNPh₂)(Me₂Calix)·Et₂O (1·Et₂O), Ti{NN(Me)Ph}(Me₂Calix)·2(C₇H₈) (2·2(C₇H₈)),

Ti(NNMe₂)(Me₂Calix)·1.75(C₇H₈) (3·1.75(C₇H₈)), Ph₂NNH₂, [Ti(NNMe₃)(Me₃Calix)(OTf)][OTf] (9-OTf·1.75(C₆H₆)) and

Ti{^tBuNC(NNMe₃)O}(MeCalix) (10·3(C₆H₆))

1·Et₂O

2·2(C₇H₈)

3·1.75(C₇H₈)

empirical formula

fw

temp/K

wavelength/Å

space group

a/Å

C₅₈H₆₈N₂O₄Ti·C₄H₁₀O

979.21

150

0.71073

P2₁/n

13.45820(10)

21.6566(3)

19.2699(3)

90

103.8770(6)

90

5452.46(12)

4

1.193

C₅₃H₆₆N₂O₄Ti·2(C₇H₈)

1027.30

150

0.71073

P2₁/a

20.9438(3)

13.0864(2)

23.3105(5)

90

111.6514(6)

90

C₄₈H₆₄N₂O₄Ti·1.75(C₇H₈)

942.19

150

0.71073

j

P1

12.8906(2)

13.5333(2)

18.6807(3)

74.0201(5)

80.0566(5)

62.9365(6)

2785.63(8)

2

b/Å

c/Å

R/deg

ꢀ/deg

γ/deg

V/Å³

5938.15(18)

4

1.149

Z

d (calcd)/Mg·m^-3

abs coeff/mm^-1

R indices^a

1.123

0.207

0.192

0.199

R₁) 0.0497^b

R_w) 0.0424^b

0.0593^b

0.0628^b

0.0881^b

0.0899^b

Ph₂NNH₂

9-OTf·1.75(C₆H₆)

10·3(C₆H₆)

empirical formula

fw

temp/K

wavelength/Å

space group

a/Å

C₁₂H₁₂N₂

184.24

150

C₅₂H₇₀F₆N₂O₁₀S₂Ti·1.75(C₆H₆)

C₅₃H₇₃N₃O₅Ti·3(C₆H₆)

1114.42

150

0.71073

P2₁/c

13.0664(3)

23.5233(6)

23.6745(7)

90

93.0525(11)

90

1245.85

150

0.71073

P2₁/n

15.998(3)

25.675(6)

16.425(3)

90

108.1990(10)

90

6409(2)

4

j

P1

9.5104(2)

11.1230(2)

11.6530(3)

116.1926(11)

112.4355(12)

94.348(2)

977.05(4)

4

b/Å

c/Å

R/deg

ꢀ/deg

γ/deg

V/Å³

7266.4(3)

4

1.019

Z

d (calcd)/Mg·m^-3

abs coeff/mm^-1

R indices^a

1.252

1.291

0.076

0.272

0.163

R₁) 0.0443^b

R₁) 0.0677^c

R₁) 0.0888^c

R_w) 0.0522^b

wR₂) 0.1885^d

wR₂) 0.2808^d

^aR₁) Σ|F_o| - |F_c|/Σ|F_o|; R_w) ꢀ{Σw (|F_o| - |F_c|)²/Σw|F_o|²}; wR₂) ꢀ{Σw (F_o- F_c)²/Σw(F_o)²}. ^bI > 3σ(I). ^cI > 2σ(I). ^dAll data.

2

an isomer of the ﬁnal product 10. Demethylation of the

Me₂Calix of 10-int is precedented by the Me-X elimination

reactions of TiX₂(Me₂Calix) (X ) Cl or OAr),^46,65but in

the present case dissociation of a side-product “Me-X” cannot

occur. Rearrangment of 10-K(N,N) to the κ(N,O)-coordinated

isomer 10 results in a less sterically crowded metal center.

A related rearrangment has been observed previously in the

reactionofTi(O)(Me₄taa)withTolNCNToltoformTi{κ(N,N’)-

TolNC(O)NTol}(Me₄taa) via a κ(N,O)-coordinated interme-

diate. It has previously been found by DFT that κ(N,N’)-

coordination of ureate ligands can be favored electronically,⁷¹

but that steric factors can favor κ(N,O)-coordination.^17,71

Interestingly, 10 can in principle exist as one of two κ(N,O)-

coordinated isomers, namely, with the N^tBu bound to Ti (as

found) or with NNMe₃⁺bound. We proposed that the likely

better sigma donor ability of N^tBu compared to NNMe₃⁺is

responsible for the observed structure.

As shown in eq 6, compound 10 could in principle also

be formed from a ﬁrst-formed hydrazidium zwitterion 6,

suggesting that an alternative mechanism for the conversion

of 3 to 10 might involve initial rearrangement of 3-6

(Scheme 2). However, we have found no evidence for the

isomerization of pure 3 to 6, even after 18 h at 100 °C.

Addition of a strong base such as DMAP likewise does not

promote O-Me migration via a potential 6-coordinate inter-

mediate Ti(NNMe₂)(DMAP)(Me₂Calix) which could be a

model for an initial adduct Ti(NNMe₂)(σ-^tBuNCO)-

(Me₂Calix).

Conclusions

Reactions of TiCl₂(Me₂Calix) with lithiated hydrazides

give high-yielding dehydrohalogenative routes to terminal

titanium hydrazides. Unfortunately, the larger radius of

zirconium prevented this methodology being extended to the

heavier congener. The X-ray structures of the series of

compounds Ti{NNRR′}(Me₂Calix) (1-3) show, by structural

comparisons with titanium imido complexes and the free

hydrazines Me₂NNH₂and Ph₂NNH₂, that (i) the NNR₂

ligands are best viewed as hydrazide(2-) groups, (ii) a

signiﬁcant contribution to N_R-N_ꢀbond length variations in

these and other Group 4 systems may arise from the change

in hybridization at N_ꢀ, and (iii) the planarity of N_ꢀis

attributed to conjugation with one or both phenyl rings. This

conjugation (possibly along with steric constraints) appears

to limit the reactions of the TidNNR₂functional groups

except in the case of Ti(NNMe₂)(Me₂Calix) (3).

However, few well-deﬁned reaction products could be

obtained for this system and possible reasons include (i) the

limitations of a rigid tetradentate ligand environment, (ii)

an absence of strongly π-donating (labilizing) coligands (in

12058 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

comparison with recent diamide-amine supported systems),¹⁹

(iii) facile calix[4]arene O-Me bond cleavage side-reactions

and (iv) apparently facile formation of TidO groups (leading

to Ti(µ-O)₂Ti moieties) via cycloaddition/extrusion pathways

(for example in the reaction of 3 with PhCHO, Me₂SO₄or

MeOTf). Despite the widespread use of calixarenes in

organometallic, coordination and metal-ligand multiple bond

chemistry, the dimethyl ethers are insufﬁciently robust to

act as a platform to develop the chemistry of the TidNNR₂

functional group.

and pyridine were dried over freshly ground CaH₂and distilled

before use. Lithiated hydrazines were prepared by reaction of 1

equiv of ⁿBuLi with the corresponding 1,1-disubstituted hydrazine

in hexanes at -78 °C. Other organic reagents were obtained

commercially, dried over CaH₂or P₂O₅, distilled under reduced

pressure and stored in Young’s Teﬂon valve ampoules.

Ti(NNPh₂)(Me₂Calix) (1). Method (a), from Ti(NNPh₂)Cl₂(py)₃:

A solution of Na₂[Me₂Calix] (0.750 g, 1.04 mmol) in benzene (40

mL) was added to a solution of Ti(NNPh₂)Cl₂(py)₃(1.120 g, 2.08

mmol) in benzene (40 mL) at 0 °C. The solution was allowed to

warm to rt and stirred for 16 h, resulting in a dark brown slurry.

Volatiles were removed under reduced pressure, and the brown solid

remaining was extracted into diethylether (2 × 15 mL) and ﬁltered.

Volatiles were removed under reduced pressure yielding a brown

solid which was washed with hexane (3 × 10 mL). The brown

solid product was dried in vacuo. Yield: 0.416 g (35%). Method

(b), from TiCl₂(Me₂Calix): A solution of LiNHNPh₂(0.719 g, 3.78

mmol) in benzene (100 mL) was added to a solution of

TiCl₂(Me₂Calix) (1.500 g, 1.89 mmol) in benzene (60 mL) at rt.

The solution was heated at 60 °C and stirred for 16 h, resulting in

a dark brown solution. Volatiles were removed under reduced

pressure, and the brown solid remaining was extracted into benzene

(2 × 30 mL) and ﬁltered. Volatiles were removed under reduced

pressure yielding a brown solid which was washed with hexane (1

× 20 mL). The brown solid product was dried in vacuo. Yield:

1.550 g (91%). ¹H NMR (C₆D₆, 299.9 MHz, 293 K): δ 8.04 (4 H,

Nonetheless, we have been able to observe the ﬁrst

catalytic demethylation of a Me₂Calix ligand leading to the

unusual zwitterionic hydrazidium derivative Ti(NNMe₃)-

t

(MeCalix) (6) and its reaction with BuNCO leading to

overall insertion into the TidN_Rbond (formation of 10). This

is a departure from the previously observed chemistry of such

species (for both Group 4 and Group 6) which focused on

N_R-N_ꢀcleavage reaction, but is of the type expected for a

+

terminal imido species (TidN-NMe₃being isoelectronic

with TidN-CMe₃, for example). Furthermore,

Ti{^tBuNC(NNMe₃)O}(MeCalix) (10) provides the ﬁrst struc-

turally authenticated example of any Group 4 hydrazidium

cycloaddition product.

3

t

d, J ) 7.6 Hz, o-NC₆H₅), 7.31 (4 H, s, OC₆H₂Bu), 7.24 (4 H,

Experimental Section

app. t, app. ³J ) 8.5 and 7.4 Hz, m-NC₆H₅), 6.87 (2 H, t, ³J ) 7.3

t

Hz, p-NC₆H₅), 6.83 (4 H, s, MeOC₆H₂Bu), 4.74 (4 H, d, ²J ) 12.3

General Methods and Instrumentation. All manipulations were

carried out under an inert atmosphere of argon or dinitrogen using

standard Schlenk-line or drybox techniques. Solvents were degassed

by sparging with dinitrogen and dried by passing through a column

of activated alumina.⁷³Deuterated solvents were dried over sodium

(C₆D₆) or P₂O₅(CDCl₃and CD₂Cl₂), distilled under reduced

pressure and stored under dinitrogen in Young’s Teﬂon valve

ampoules. Solution NMR samples were prepared under a dinitrogen

atmosphere in a drybox, in 5 mm Wilmad NMR tubes possessing

Young’s Teﬂon valves. ¹H and ¹³C-{¹H} NMR spectra were

recorded on a Varian Mercury 300 or a Varian Unity Plus 500

spectrometer at ambient temperature. The ¹H and ¹³C spectra were

initially referenced to either residual solvent (¹H) or (¹³C) resonances

and are reported relative to tetramethylsilane (δ ) 0 ppm). ¹⁹F

spectra were referenced externally to CFCl₃. Chemical shifts are

quoted in δ (ppm) and coupling constants (J) in Hz. Where

Hz, ArCH₂Ar proximal to OMe), 4.06 (6 H, s, OMe), 3.33 (4 H, d,

t

²J ) 12.3 Hz, ArCH₂Ar distal to OMe), 1.50 (18 H, s, OC₆H₂Bu),

t

0.69 (18 H, s, MeOC₆H₂Bu). ¹³C-{¹H} NMR (C₆D₆, 75.4 MHz,

t

293 K): δ 160.0 (i-OC₆H₂Bu), 150.6 (i-MeOC₆H₂Bu), 149.1 (p-

t

MeOC₆H₂Bu), 146.6 (i-NC₆H₅), 140.6 (p-OC₆H₂Bu), 132.8 (o-

MeOC₆H₂Bu), 129.3 (m-NC₆H₅and o-OC₆H₂Bu), 127.0 (m-

t

MeOC₆H₂Bu), 125.0 (m-OC₆H₂Bu), 122.5 (p-NC₆H₅), 117.5 (o-

NC₆H₅), 72.1 (OMe), 34.2 (OC₆H₂CMe₃), 33.6 (ArCH₂Ar and

MeOC₆H₂CMe₃), 31.9 (OC₆H₂CMe₃), 30.6 (MeOC₆H₂CMe₃). IR

(KBr plates, Nujol mull, cm^-1): ν 1592 (s), 1544 (m), 1479 (s),

1392 (m), 1362 (m), 1330 (s), 1308 (s), 1274 (s), 1211 (m), 1185

(m), 1166 (m), 1121 (m), 1091 (m), 1028 (w), 1004 (m), 942 (w),

913 (m), 873 (m), 858 (m), 848 (m), 796 (m), 779 (w), 748 (m),

697 (m), 680 (w), 627 (m), 567 (s). EI-MS: m/z 904 [M]⁺(100%),

707 [M-NNPh₂Me]⁺(38%), 197 [NNPh₂Me]⁺(17%). Anal. found

(calcd. for C₅₈H₆₈N₂O₄Ti): C 76.84 (76.97), H 7.60 (7.57), N 3.12

(3.10) %.

1

necessary, H and ¹³C experiments were assisted by H-¹H and

¹H-¹³C correlation experiments. IR spectra were recorded on a

Nicolet Magna 560 ESP FTIR spectrometer. Samples were prepared

in a drybox as Nujol mulls between NaCl plates. IR data are quoted

as wavenumbers (cm^-1) within the range 4000-400 cm^-1. Mass

spectra were recorded by the departmental service and elemental

analyses were carried out by the Elemental Analysis Service at the

London Metropolitan University.

Ti{NN(Me)Ph}(Me₂Calix) (2). A slurry of LiNHNMePh (0.500

g, 3.90 mmol) in benzene (80 mL) was added to a solution of

TiCl₂(Me₂Calix) (1.549 g, 1.95 mmol) in benzene (50 mL). The

solution was heated at 60 °C and stirred for 16 h, resulting in a

dark brown solution. Volatiles were removed under reduced

pressure, the remaining brown solid was extracted into benzene (2

× 25 mL) and ﬁltered. Volatiles were removed under reduced

pressure yielding a brown solid which was washed with hexane (1

× 20 mL). The brown solid was dried in vacuo. Yield: 1.449 g

Starting Materials. Na₂[Me₂Calix],⁷⁴Ti(NNPh₂)Cl₂(py)₃,²⁰

TiCl₂(Me₂Calix) and ZrCl₂(Me₂Calix)⁴⁶were prepared according

to literature procedures. 1,1-Diphenylhydrazine was obtained from

Sigma-Aldrich as the hydrogen chloride salt, from which the free

hydrazine was obtained by basiﬁcation, drying and removal of

residual solvent, followed by distillation under inert atmospheric

conditions. 1,1-Dimethylhydrazine and 1-methyl-1-phenylhydrazine

3

(88%). ¹H NMR (C₆D₆, 299.9 MHz, 293 K): δ 7.70 (2 H, d, J )

7.9 Hz, o-NC₆H₅), 7.34 (2 H, app. t, ³J ) 7.9 and 7.2 Hz, m-NC₆H₅),

t

7.33 (4 H, s, OC₆H₂Bu), 6.85 (4 H, s, MeOC₆H₂Bu), 6.81 (1 H,

3

2

t, J ) 7.2 Hz, p-NC₆H₅), 4.80 (4 H, d, J ) 12.3 Hz, ArCH₂Ar

proximal to OMe), 4.06 (6 H, s, OMe), 3.44 (3 H, s, NMe), 3.37

(73) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;

Timmers, F. J. Organometallics 1996, 15, 1518.

(74) Dubberley, S. R.; Blake, A. J.; Mountford, P. Dalton Trans. 2003,

2418.

2

(4 H, d, J ) 12.3 Hz, ArCH₂Ar distal to OMe), 1.51 (18 H, s,

t

OC₆H₂Bu), 0.70 (18 H, s, MeOC₆H₂Bu). ¹³C-{¹H} NMR (C₆D₆,

t

75.4 MHz, 293 K): δ 159.7 (i-OC₆H₂Bu), 150.2 (i-MeOC₆H₂Bu),

Inorganic Chemistry, Vol. 47, No. 24, 2008 12059

Clulow et al.

t

148.6 (p-MeOC₆H₂Bu), 148.2 (i-NC₆H₅), 140.0 (p-OC₆H₂Bu),

(m), 1214 (m), 1169 (m), 1118 (m), 1090 (m), 1063 (w), 1029

(w), 991 (m), 935 (w), 873 (m), 856 (m), 792 (m), 746 (m), 732

(m), 691 (m), 665 (m), 641 (m). Anal. found (calcd. for

C₇₀H₈₀N₄O₄Zr): C 74.15 (74.23), H 7.08 (7.12), N 4.91 (4.95) %.

Zr(NHNMe₂)₂(Me₂Calix) (5). A solution of LiNHNMe₂(0.158

g, 2.39 mmol) in benzene (40 mL) was added to a slurry of

ZrCl₂(Me₂Calix) in benzene (40 mL). The mixture was heated at

60 °C and stirred for 1 h, yielding a cloudy beige solution. Volatiles

were removed under reduced pressure, the product was extracted

into benzene (2 × 40 mL) and ﬁltered. Volatiles were removed

under reduced pressure, yielding the title product as a beige solid

t

132.4 (m-MeOC₆H₂Bu), 129.1 (m-NC₆H₅), 128.9 (m-OC₆H₂Bu),

t

126.6 (m-MeOC₆H₂Bu), 142.4 (m-OC₆H₂Bu), 118.6 (p-NC₆H₅),

110.1 (m-NC₆H₅), 71.7 (OMe), 41.7 (NMe), 33.9 (ArCH₂Ar), 33.4

and 33.4 (overlapping MeOC₆H₂CMe₃and OC₆H₂CMe₃), 31.9

(OC₆H₂CMe₃), 30.3 (MeOC₆H₂CMe₃). IR (KBr plates, Nujol mull,

cm^-1): ν 1593 (m), 1466 (s), 1363 (m), 1332 (s), 1319 (s), 1278

(w), 1261 (w), 1210 (m), 1165 (w), 1120 (m), 1093 (m), 1012 (m),

935 (w), 914 (w), 873 (m), 859 (m), 844 (w), 807 (m), 796 (m),

750 (w), 692 (w). EI-MS: m/z 842 [M]⁺(100%), 135 [NNPhMe₂]⁺

(5%), 121 [NPhMe₂]⁺(17%). Anal. found (calcd. for

C₅₃H₆₆N₂O₄Ti): C 75.59 (75.51), H 7.86 (7.89), N 3.29 (3.32) %.

Ti(NNMe₂)(Me₂Calix) (3). A solution of LiNHNMe₂(0.483 g,

7.31 mmol) in benzene (20 mL) was added to a solution of

TiCl₂(Me₂Calix) (2.900 g, 3.65 mmol) in benzene (100 mL). The

reaction mixture was heated at 60 °C and stirred for 16 h, resulting

in a brown solution. Volatiles were removed under reduced pressure,

and the remaining brown solid was extracted into diethylether (4

× 25 mL) and ﬁltered. Volatiles were removed under reduced

pressure yielding a light brown solid that was dried in vacuo. Yield:

2.136 g (75%). ¹H NMR (C₆D₆, 299.9 MHz, 293 K): δ 7.33 (4 H,

1

that was dried in vacuo. Yield: 0.601 g (60%). H NMR (C₆D₆,

t

299.9 MHz, 293 K): δ 7.38 (4 H, s, OC₆H₂Bu), 6.98 (4 H, s,

t

2

MeOC₆H₂Bu), 4.53 (4 H, d, J ) 11.7 Hz, ArCH₂Ar proximal to

2

OMe), 3.65 (6 H, s, OMe), 3.39 (4 H, d, J ) 12 Hz, ArCH₂Ar

distal to OMe), 3.20 (2 H, s, NHNMe₂), 2.67 (12 H, s, NHNMe₂),

t

1.53 (18 H, s, OC₆H₂Bu), 0.83 (18 H, s, MeOC₆H₂Bu). ¹³C-{¹H}

t

NMR (C₆D₆, 75.4 MHz, 293 K): δ 160.2 (i-OC₆H₂Bu), 154.4 (i-

MeO₆H₂Bu), 147.7 (p-MeOC₆H₂Bu), 138.1 (p-OC₆H₂Bu), 132.3

(o-OC₆H₂Bu), 130.5 (o-MeOC₆H₂Bu), 126.4 (m-OC₆H₂Bu), 124.7

(m-MeOC₆H₂Bu), 66.3 (OMe), 52.6 (NHNMe₂), 34.6 (ArCH₂Ar),

t

s, OC₆H₂Bu), 6.86 (4 H, s, MeOC₆H₂Bu), 4.80 (4 H, d, ²J ) 12.4

Hz, ArCH₂Ar proximal to OMe), 4.32 (6 H, s, OMe), 3.37 (4 H, d,

²J ) 12.4 Hz, ArCH₂Ar distal to OMe), 2.82 (6 H, s, NMe₂), 1.51

34.2 (OC₆H₂CMe₃), 33.7 (MeOC₆H₂CMe₃), 32.4 (OC₆H₂CMe₃),

30.8 (MeOC₆H₂CMe₃). IR (KBr plates, Nujol mull, cm^-1): ν 3583

(w, ν(N-H)), 2814 (m), 1603 (w), 1481 (s), 1392 (m), 1362 (m),

1334 (s), 1321 (s), 1285 (m), 1262 (m), 1215 (s), 1167 (m), 1123

(m), 1097 (m), 1015 (s), 982 (m), 943 (w), 926 (m), 916 (m), 870

(m), 847 (s), 797 (m), 787 (m), 760 (w), 702 (w), 666 (m). EI-MS:

m/z 208 [Zr(NHNMe₂)₂]⁺(50%). Anal. found (calcd. for

C₅₀H₇₂N₄O₄Zr): C 67.86 (67.91), H 8.19 (8.21), N 6.25 (6.34) %.

t

(18 H, s, OC₆H₂Bu), 0.71 (18 H, s, MeOC₆H₂Bu). ¹³C-{¹H} NMR

t

(C₆D₆, 75.4 MHz, 293 K): δ 160.1 (i-OC₆H₂Bu), 150.6 (i-

MeOC₆H₂Bu), 148.8 (p-MeOC₆H₂Bu), 139.9 (p-OC₆H₂Bu), 132.8

(o-MeOC₆H₂Bu), 129.2 (o-OC₆H₂Bu), 126.8 (m-MeOC₆H₂Bu),

124.7 (m-OC₆H₂Bu), 72.5 (OMe), 49.0 (NMe₂), 34.2

t

(OC₆H₂CMe₃), 33.7 (overlapping MeOC₆H₂CMe₃and ArCH₂Ar),

32.3 (OC₆H₂CMe₃), 30.5 (MeOC₆H₂CMe₃). IR (KBr plates, Nujol

mull, cm^-1): ν 1599 (m), 1480 (s), 1392 (m), 1361 (s), 1319 (s),

1212 (s), 1166 (m), 1119 (s), 1093 (m), 1002 (s), 937 (m), 921

(m), 891 (m), 871 (s), 856 (m), 810 (m), 796 (s), 782 (m), 758

(m), 709 (w), 677 (s), 637 (w), 608 (m), 565 (s). EI-MS: m/z 121

[TiNNMe₃]⁺(16%), 105 [TiNNMe₂]⁺(8%), 58 [NNMe₂]⁺(31%).

Anal. found (calcd. for C₄₈H₆₄N₂O₄Ti): C 73.84 (73.83), H 8.24

(8.26), N 3.58 (3.59) %.

NMR Tube Scale Reaction of Ti(NNMe₂)(Me₂Calix) (3) with

PhCHO. Benzaldehyde (2.6 µL, 0.026 mmol) was added to a

solution of Ti(NNMe₂)(Me₂Calix) (0.020 g, 0.026 mmol) in C₆D₆

(0.75 mL). After 16 h at rt the ¹H NMR spectrum showed

quantitative conversion to [Ti(µ-O)(Me₂Calix)]₂in addition to a

mixture of the geometrical isomers of benzaldehyde-dimethylhy-

drazone.⁷⁰

Ti(NNMe₃)(MeCalix) (6). MeI (71.7 µL, 1.150 mmol) was added

to a solution of Ti(NNMe₂)(Me₂Calix) (0.300 g, 0.384 mmol) in

benzene (20 mL). The solution was heated at 100 °C for 20 min

and the volatiles were removed under reduced pressure. The

remaining orange solid was washed with pentane (1 × 10 mL)

leaving a pale orange solid that was dried in vacuo. Yield: 0.126

Zr(NHNPh₂)₂(Me₂Calix) (4). A solution of LiNHNPh₂(0.227

g, 1.19 mmol) in benzene (50 mL) was added to a slurry of

ZrCl₂(Me₂Calix) (0.500 g, 0.60 mmol) in benzene (50 mL). The

mixture was heated at 60 °C and stirred for 1 h, yielding a turbid

yellow solution. Volatiles were removed under reduced pressure,

and the product was extracted into benzene (2 × 40 mL) and

ﬁltered. The volatiles were removed under reduced pressure, and

the product was extracted into hexane (2 × 5 mL) and ﬁltered.

Repeated crystallizations from this saturated hexane solution at -30

°C yielded the title product as a beige solid that was dried in vacuo.

Yield: 0.118 g (21%). ¹H NMR (C₆H₆, 299.9 MHz, 293 K): δ 7.34

1

4

g, (42%). H NMR (C₆D₆, 299.9 MHz, 293 K): δ 7.44 (2 H, d, J

t

) 2.3 Hz, MeOAr-OC₆H₂Bu-ArO proximal to ArO), 7.36 (2 H,

t

d, ⁴J ) 2.3 Hz, MeOAr-OC₆H₂Bu-ArO proximal to MeOAr), 7.02

t

(4 H, s, overlapping MeOC₆H₂Bu and OAr-OC₆H₂Bu-ArO), 5.21

(2 H, d, J ) 11.8 Hz, OAr-CH₂-ArO proximal to OMe), 4.64 (2

H, d, J ) 11.8 Hz, MeOAr-CH₂-ArO proximal to OMe), 4.03 (3

2

H, s, OMe), 3.48 (2 H, d, J ) 11.8 Hz, OAr-CH₂-ArO distal to

3

t

OMe), 3.45 (2 H, d, ²J ) 11.8 Hz, MeOAr-CH₂-ArO distal to OMe),

(8 H, d, J ) 7.4 Hz, o-NHNPh₂), 7.24 (4 H, s, OC₆H₂Bu), 7.13

3

t

(8 H, app. t, J ) 7.2 and 7.4 Hz, m-NHNPh₂), 6.88 (4 H, t, J )

7.2 Hz, p-NHNPh₂), 6.80 (4 H, s, MeOC₆H₂Bu), 4.17 (4 H, d, J

2.75 (9 H, s, NNMe₃), 1.51 (18 H, s, MeOAr-OC₆H₂Bu-ArO), 0.91

t

2

t

(9 H, s, MeOC₆H₂Bu or OAr-OC₆H₂Bu-ArO), 0.82 (9 H, s,

t

MeOC₆H₂Bu or OAr-OC₆H₂Bu-ArO). ¹³C-{¹H} NMR (C₆D₆, 75.4

) 12.7 Hz, ArCH₂Ar proximal to OMe), 3.86 (6 H, s, OMe), 3.16

2

t

(4 H, d, J ) 12.7 Hz, ArCH₂Ar distal to OMe), 1.48 (18 H, s,

MHz, 293 K): δ 159.3 (i-MeOAr-OC₆H₂Bu-ArO), 155.0 (i-OAr-

OC₆H₂Bu-ArO), 150.7 (i-MeOC₆H₂Bu), 147.9 (p-MeOC₆H₂Bu or

p-OAr-OC₆H₂^tBu-ArO), 140.9 (p-MeOC₆H₂^tBu or p-OAr-OC₆H₂^tBu-

ArO), 140.7 (p-MeO-OC₆H₂Bu-ArO), 132.9 (o-MeO-C₆H₂Bu or

o-MeOAr-OC₆H₂Bu-ArO proximal to MeOAr), 131.7 (o-OAr-

OC₆H₂Bu-ArO or o-MeOAr-OC₆H₂Bu-ArO proximal to OAr),

129.3 (o-MeO-C₆H₂Bu or o-MeOAr-OC₆H₂Bu-ArO proximal to

MeOAr), 128.6 (o-OAr-OC₆H₂Bu-ArO or o-MeOAr-OC₆H₂Bu-

ArO proximal to OAr), 126.4 (m-MeOC₆H₂^tBu or m-OAr-OC₆H₂^tBu-

ArO), 125.0 (m-MeOC₆H₂Bu or m-OAr-OC₆H₂Bu-ArO), 124.9 (m-

t

OC₆H₂Bu), 0.71 (18 H, s, MeOC₆H₂Bu). ¹³C-{¹H} NMR (C₆D₆,

t

75.4 MHz, 293 K): δ 158.2 (i-OC₆H₂Bu), 153.7 (i-MeOC₆H₂Bu),

151.9 (i-NHNPh₂), 148.8 (p-MeOC₆H₂Bu), 141.0 (p-OC₆H₂Bu),

131.8 (o-MeOC₆H₂Bu), 130.6 (o-OC₆H₂Bu), 128.9 (m-NHNPh₂),

127.3 (m-MeOC₆H₂Bu), 124.5 (m-OC₆H₂Bu), 121.2 (p-NHNPh₂),

120.5 (o-NHNPh₂), 69.7 (OMe), 34.3 (OC₆H₂CMe₃), 33.7

(ArCH₂Ar and MeOC₆H₂CMe₃), 32.2 (OC₆H₂CMe₃), 30.6

(MeOC₆H₂CMe₃). IR (KBr plates, Nujol mull, cm^-1): ν 3583 (w,

ν(N-H)), 1587 (m), 1480 (s), 1464 (s), 1363 (m), 1320 (s), 1276

t

12060 Inorganic Chemistry, Vol. 47, No. 24, 2008

Synthesis of Group 4 Hydrazido Complexes

t

MeOAr-OC₆H₂Bu-ArO proximal to ArO), 123.4 (m-MeOAr-

cold pentane (3 × 20 mL) and dried in vacuo to give 7-OTf as a

t

1

OC₆H₂Bu-ArO proximal to MeOAr), 67.0 (OMe), 59.8 (NMe₃),

pale yellow powder. Yield: 0.08 g, (22%). H NMR (C₆D₆, 299.9

t

34.10 (MeO-OC₆H₂CMe₃-ArO), 33.9 (OAr-CH₂-ArO), 33.9 (OAr-

OC₆H₂CMe₃-ArO or MeOC₆H₂CMe₃), 33.4 (overlapping MeOAr-

CH₂-ArO and OAr-OC₆H₂CMe₃-ArO or MeOC₆H₂CMe₃), 31.9

(MeOAr-OC₆H₂CMe₃-ArO), 30.9 (MeOC₆H₂CMe₃or OAr-

OC₆H₂CMe₃-ArO), 30.5 (MeOC₆H₂CMe₃or OAr-OC₆H₂CMe₃-

ArO). IR (KBr plates, Nujol mull, cm^-1): ν 1595 (w), 1544 (w),

1465 (s), 1393 (m), 1361 (m), 1322 (s), 1310 (s), 1281 (m), 1260

(m), 1239 (m), 1207 (s), 1167 (w), 1124 (m), 1012 (m), 941 (w),

919 (m), 872 (m), 850 (m), 827 (m), 819 (m), 798 (s), 780 (w),

758 (m), 722 (w), 699 (w), 675 (w), 617 (m), 563 (s). Anal. found

(calcd. for C₄₈H₆₄N₂O₄Ti): C 73.84 (73.83), H 8.19 (8.26), N 3.56

(3.59) %.

NMR Tube Scale Synthesis of Ti(NNMe₂CD₃)(MeCalix)

(6-d₃). CD₃I (4.8 µL, 0.077 mmol) was added to a solution of

Ti(NNMe₂)(Me₂Calix) (0.020 g, 0.026 mmol) in C₆D₆(0.75 mL).

The mixture was heated at 100 °C for 20 min. The ¹H NMR

spectrum showed quantitative conversion to Ti(NNMe₂CD₃)-

(MeCalix) (8-d₃) with the concomitant evolution of one equivalent

of MeI.

²H NMR (C₆H₆, 76.7 MHz, 293 K): δ 2.59 (s, NCD₃).

NMR Tube Scale Reaction of Ti(NNMe₂)(Me₂Calix) with

0.12 equiv MeI. MeI (0.6 µL, 0.009 mmol) was added to a solution

of Ti(NNMe₂)(Me₂Calix) (0.050 g, 0.064 mmol) in C₆D₆. The

mixture was heated at 100 °C for 30 min. The ¹H NMR spectrum

revealed the quantitative conversion of 3 to 6 with MeI present in

the product mixture in the same proportions as at the start of the

reaction.

NMR Tube Scale Synthesis of Ti{NN(Me)₂CH₂Ph}(MeCalix)

(8). Benzyl bromide (9.1 µL, 0.077 mmol) was added to a solution

of Ti(NNMe₂)(Me₂Calix) (0.020 g, 0.026 mmol) in C₆D₆(0.75 mL).

The solution was heated at 60 °C for 16 h. The ¹H NMR spectrum

revealed quantitative conversion to Ti(NNMe₂Bz)(MeCalix) (8).

MHz, 293 K): δ 7.24 (4H, s, OC₆H₂Bu), 6.81 (4H, s,

t

2

MeOC₆H₂Bu), 4.56 (4H, d, J ) 12.7 Hz, ArCH₂Ar proximal to

2

OMe), 4.41 (6H, s, OMe), 3.50 (9H, s, NMe), 3.34 (4H, d, J )

12.7 Hz, ArCH₂Ar distal to OMe), 1.45 (18H, s, OC₆H₂Bu), 0.70

(18H, s, MeOC₆H₂Bu). ¹³C-{¹H} NMR (C₆D₆, 75.4 MHz, 293 K):

t

δ

160.0 (i-OC₆H₂Bu), 151.3 (i-MeOC₆H₂Bu), 149.6 (p-

t

MeOC₆H₂Bu), 142.7 (p-OC₆H₂Bu), 132.0 (o-MeOC₆H₂Bu), 129.5

t

(o-OC₆H₂Bu), 127.1 (m-MeOC₆H₂Bu), 124.8 (m-OC₆H₂Bu), 74.3

(OMe), 60.8 (NMe), 34.3 (OC₆H₂CMe₃), 33.7 (MeOC₆H₂CMe₃),

33.5 (Ar-CH₂-Ar), 32.0 (OC₆H₂CMe₃), 30.6 (MeOC₆H₂CMe₃). ¹⁹F-

{¹H} NMR (C₆D₆, 282.4 MHz, 293 K): δ -77.82 (CF₃). IR (NaCl

plates, Nujol mull, cm^-1): ν 1563 (w), 1506 (w), 1464 (s), 1394

(w), 1377 (m), 1364 (m), 1272 (s), 1258 (s), 1212 (m), 1164 (s),

1115 (w), 1092 (w), 1043 (m), 1032 (s), 993 (w), 941 (w), 932

(w), 874 (w), 862 (w), 796 (w), 756 (w), 722 (w), 665 (w), 641

(s), 573 (m). Anal. found (calcd. for C₅₀H₆₇F₃N₂O₇STi): C

63.45(63.55), H 7.10 (7.15), N 3.06 (2.96) %.

Reaction of [Ti(NNMe₃)(Me₂Calix)][OTf] (7-OTf) with ⁿBu₄NI.

Methyl triﬂate (2.9 µL, 0.026 mmol) was added to a solution of

Ti(NNMe₂)(Me₂Calix) (0.020 g, 0.026 mmol) to form a red solution

of [Ti(NNMe₃)(Me₂Calix)][OTf] (7-OTf) as above. Bu₄NI (0.009

g, 0.026 mmol) was added to this solution, leading to a color change

1

from red back to orange. After heating at 60 °C for 1 h the H

NMR spectrum showed the near-quantitative formation of

Ti(NNMe₃)(MeCalix) (6) along with MeI.

Ti{^tBuNC(NNMe₃)O}(MeCalix) (10). ^tBuNCO (87.7 µL, 0.768

mmol) was added to a solution of Ti(NNMe₂)(Me₂Calix) (0.500 g,

0.640 mmol) in benzene (30 mL). The solution was heated at 70

°C for 16 h and the volatiles were removed under reduced pressure

leaving an orange/brown solid. Washing with pentane (2 × 5 mL)

yielded an orange solid that was dried in vacuo. Yield: 0.162 g,

(29%). ¹H NMR (C₆D₆, 299.9 Hz, 293 K): δ 7.38 (2 H, d, ⁴J ) 2.4

1

t

4

The H NMR spectrum of 8 was assigned by analogy with the

Hz, MeOAr-OC₆H₂Bu-ArO proximal to ArO), 7.34 (2 H, d, J )

t

resonances of 6. Attempts to isolate 8 on a preparative scale were

unsuccessful. When a smaller excess of benzyl bromide is used in

this reaction, small amounts of Ti(NNMe₃)(MeCalix) (6) are also

observed. ¹H NMR (C₆D₆, 299.9 MHz, 293 K): δ 7.52 (1 H, d, ³J

) 7.9 Hz, p-NCH₂Ph), 7.35 (2 H, d, ⁴J ) 2.0 Hz, MeOAr-

2.4 Hz, MeOAr-OC₆H₂Bu-ArO proximal to MeOAr), 7.06 (2 H,

s, MeOC₆H₂Bu or OAr-OC₆H₂Bu-ArO), 7.03 (2 H, s, MeOC₆H₂Bu

or OAr-OC₆H₂Bu-ArO), 5.35 (2 H, d, J ) 12.6 Hz, OAr-CH₂-

ArO proximal to OMe), 4.70 (2 H, d, J ) 12.3 Hz, OAr-CH₂-

ArO distal to OMe), 3.81 (3 H, s, OMe), 3.54 (2 H, d, J ) 12.6

Hz, OAr-CH₂-ArO distal to OMe), 3.46 (2 H, d, J ) 12.3 Hz,

t

2

t

OC₆H₂Bu-ArO proximal to ArO), 7.28 (2 H, d, ⁴J ) 2.0 Hz,

2

t

MeOAr-OC₆H₂Bu-ArO proximal to MeOAr), 7.05 (2 H, app. t,

MeOAr-CH₂-ArO distal to OMe), 2.28 (9 H, s, NNMe₃), 1.85 (9

t

app. ³J ) 7.9 and 7.4 Hz, m-NCH₂Ph), 6.95 (2 H, s, MeOC₆H₂Bu

t

H, s, N^tBu), 1.46 (18 H, s, MeOAr-OC₆H₂Bu-ArO), 0.91 (9 H, s,

t

or OAr-OC₆H₂Bu-ArO), 6.91 (2 H, s, MeOC₆H₂Bu or OAr-

MeOC₆H₂Bu or OAr-OC₆H₂Bu-ArO), 0.85 (9 H, s, MeOC₆H₂Bu

t

OC₆H₂Bu-ArO), 6.90 (1 H, t, ³J ) 7.4 Hz, p-NCH₂Ph), 5.01 (2 H,

t

or OAr-OC₆H₂Bu-ArO). ¹³C-{¹H} NMR (C₆D₆, 75.4 MHz, 293

K): δ 172.0 (^tBuNC(NNMe₃)O), 162.9 (i-OAr-OC₆H₂Bu-ArO),

162.3 (i-MeOAr-OC₆H₂Bu-ArO), 154.1 (i-MeOC₆H₂Bu), 147.3 (p-

OAr-OC₆H₂Bu-ArO), 142.5 (p-MeOC₆H₂Bu), 141.6 (p-MeOAr-

OC₆H₂Bu-ArO), 133.3 (o-MeOC₆H₂Bu or o-MeOAr-OC₆H₂Bu-

ArOproximaltoMeOAr),133.2(o-OAr-OC₆H₂^tBu-ArOoro-MeOAr-

OC₆H₂Bu-ArO proximal to OAr), 131.1 (o-MeOC₆H₂Bu or

o-MeOAr-OC₆H₂Bu-ArO proximal to MeOAr), 127.0 (o-OAr-

OC₆H₂Bu-ArO or o-MeOAr-OC₆H₂Bu-ArO proximal to OAr),

2

t

d, J ) 12.6 Hz, OAr-CH₂-ArO proximal to OMe), 4.26 (2 H, s,

NCH₂Ph), 4.07 (2 H, d, ²J ) 12.1 Hz, MeOAr-CH₂-ArO proximal

to OMe), 3.46 (2 H, d, ²J ) 12.6 Hz, OAr-CH₂-ArO distal to OMe),

3.29 (3 H, s, OMe), 3.21 (2 H, d, ²J ) 12.1 Hz, MeOAr-CH₂-ArO

distal to OMe), 2.77 (6 H, s, NMe₂), 1.48 (18 H, s, MeOAr-

t

OC₆H₂Bu-ArO), 0.91 (9 H, s, MeOC₆H₂Bu or OAr-OC₆H₂Bu-

t

ArO), 0.77 (9 H, s, MeOC₆H₂Bu or OAr-OC₆H₂Bu-ArO).

NMR Tube Scale Reaction of Ti(NNMe₂)(Me₂Calix) (3) with

Me₂SO₄. Dimethyl sulfate (2.4 µL, 0.026 mmol) was added to a

solution of Ti(NNMe₂)(Me₂Calix) (0.020 g, 0.026 mmol) in C₆D₆

(0.75 mL). After 16 h a yellow precipitate had formed, and the ¹H

NMR spectra (taken in CD₂Cl₂and C₆D₆) showed that [Ti(µ-

O)(Me₂Calix)]₂had been formed as the major product.⁴⁶

Synthesis of [Ti(NNMe₃)(Me₂Calix)][OTf] (7-OTf). Methyl tri-

ﬂate (45 µL, 0.40 mmol) was added to

Ti(NNMe₂)(Me₂Calix) (0.300 g, 0.38 mmol) in benzene (20 mL).

The resultant red solution was stirred for 16 h, during which time

a pale orange solid formed. This was was ﬁltered, washed with

t

126.5 (m-MeOC₆H₂Bu), 125.4 (m-OAr-OC₆H₂Bu-ArO), 125.0 (m-

MeOAr-OC₆H₂Bu-ArO proximal to OAr), 123.6 (m-MeOAr-

OC₆H₂Bu-ArO proximal to MeOAr), 63.5 (OMe), 56.2 (NNMe₃),

t

55.1 (NCMe₃), 35.2 (OAr-CH₂-ArO), 34.7 (MeOAr-CH₂-ArO),

34.3 (MeOAr-OC₆H₂CMe₃-ArO), 33.7 (OAr-OC₆H₂CMe₃-ArO),

33.5 (MeOC₆H₂CMe₃), 32.1 (MeOAr-OC₆H₂CMe₃-ArO), 31.9

(MeOC₆H₂CMe₃), 31.4 (NCMe₃), 31.2 (OAr-OC₆H₂CMe₃-ArO).

IR (NaCl plates, Nujol mull, cm^-1): ν 1568 (w), 1519 (m), 1465

(s), 1392 (w), 1377 (s), 1362 (m), 1313 (w), 1278 (m), 1239 (w),

1209 (s), 1170 (w), 1124 (w), 1070 (w), 1014 (w), 937 (w), 920

a solution of

Inorganic Chemistry, Vol. 47, No. 24, 2008 12061

Clulow et al.

(w), 871 (w), 858 (w), 825 (w), 819 (s), 792 (m), 756 (w), 723

(w), 677 (m), 665 (m), 601 (s). Anal. found (calcd. for

C₅₃H₇₃N₃O₅Ti): C 72.36 (72.33), H 8.30 (8.36), 7.83 (7.77) %.

NMR Tube Scale Synthesis of Ti{^tBuNC(NNMe₃)O}(MeCalix)

(10) from Ti(NNMe₃)(MeCalix) (6) and ^tBuNCO. ^tBuNCO (2.9 µL,

0.026 mmol) was added to a solution of Ti(NNMe₃)(MeCalix)

(0.020 g, 0.026 mmol) in C₆D₆(0.75 mL). The mixture was heated

Coordinates and anisotropic thermal parameters of all non-hydrogen

atoms were reﬁned (see additional comments below). H atoms

bonded to C were placed geometrically while the N-H atoms for

Ph₂NNH₂were located from Fourier difference maps and reﬁned

isotropically. Further details of the reﬁnements are provided in the

CIF in Supporting Information. A full listing of atomic coordinates,

bond lengths and angles and displacement parameters for all the

structures have been deposited at the Cambridge Crystallographic

Data Centre. See Notice to Authors, Issue No. 1.

1

at 60 °C for 1 h. The H NMR spectrum showed formation of 10

in 70% yield.

Crystal Structure Determinations of Ti(NNPh₂)(Me₂-

Calix)·Et₂O

(1·Et₂O),

Ti{NN(Me)Ph}(Me₂Calix)·2(C₇H₈)

Acknowledgment. We thank the EPSRC and the Nufﬁeld

(2·2(C₇H₈)), Ti(NNMe₂)(Me₂Calix)·1.75(C₇H₈) (3·1.75(C₇H₈)),

Ph₂NNH₂, [Ti(NNMe₃)(Me₃Calix)(OTf)][OTf] (9-OTf·1.75(C₆H₆))

and Ti{^tBuNC(NNMe₃)O}(MeCalix) (10 ·3(C₆H₆)). Crystal data

collection and processing parameters are given in Table 5. Crystals

were mounted on glass ﬁbers using perﬂuoropolyether oil and

cooled rapidly in a stream of cold N₂using an Oxford Cryosystems

CRYOSTREAM unit. Diffraction data were measured using either

an Enraf-Nonius KappaCCD diffractometer. Intensity data were

processed using the DENZO-SMN package.⁷⁵The structures were

solved using the direct-methods program SIR92,⁷⁶which located

all non-hydrogen atoms. Subsequent full-matrix least-squares

reﬁnement was carried out using the CRYSTALS program suite.⁷⁷

Foundation for support.

Note Added after ASAP Publication. There was an error

in Scheme 2 in the version published ASAP November 11,

2008; the corrected version was published ASAP

November 18, 2008.

Supporting Information Available: X-ray crystallographic

data in CIF format for the structure determinations of Ti-

(NNPh₂)(Me₂Calix)·Et₂O (1·Et₂O), Ti{NN(Me)Ph}(Me₂Calix)·-

2(C₇H₈) (2·2(C₇H₈)), Ti(NNMe₂)(Me₂Calix) ·1.75(C₇H₈) (3·1.75-

(C₇H₈)), Ph₂NNH₂, [Ti(NNMe₃)(Me₃Calix)(OTf)][OTf] (9-OTf·

1.75(C₆H₆)), and Ti{^tBuNC(NNMe₃)O}(MeCalix) (10·3(C₆H₆)). This

information is available free of charge via the Internet at http://

pubs.acs.org.

(75) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data

Collected in Oscillation Mode; Academic Press: New York, 1997.

(76) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.; Burla,

M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.

(77) Betteridge, P. W.; Cooper, J. R.; Cooper, R. I.; Prout, K.; Watkin,

D. J. J. Appl. Crystallogr. 2003, 36, 1487.

IC801735C

12062 Inorganic Chemistry, Vol. 47, No. 24, 2008

Article Doi

Synthesis, structures and reactivity of group 4 hydrazido complexes supported by calix[4]arene ligands

DOI: 10.1021/ic801735c

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