Synthesis and reactivity of titanium hydrazido complexes supported by diamido-ether ligands

Article

pubs.acs.org/Organometallics

Synthesis and Reactivity of Titanium Hydrazido Complexes

Supported by Diamido-Ether Ligands

Junjuda Unruangsri, Hannah Morgan, Andrew D. Schwarz, A. Daniel Schoﬁeld, and Philip Mountford*

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

S

* Supporting Information

ABSTRACT: The synthesis and reactivity of titanium

diphenyl hydrazido(2−) complexes supported by the

diamido-ether ligands O(2-C₆H₄NSiMe₃)₂(N₂^ArO) and O-

(CH₂CH₂NSiMe₃)₂(N₂O) are described. Reaction of

Li₂N₂^ArO or Li₂N₂O with Ti(NNPh₂)Cl₂(py)₃aﬀorded

Ti(N₂^ArO)(NNPh₂)(py)₂(14) or Ti(N₂O)(NNPh₂)(py)_2t

(15) with κ³-mer-bound diamido-ether ligands. Reaction with Bu-bipy (4,4′-di-tert-butyl-2,2′-bipyridyl) or bipy (2,2′-bipyridyl)

gave a switch to κ³-fac-coordination. Reaction of 15 with Ar′NCO (Ar′ = 2,6-C₆H₃Pr₂) gave Ti{O(CH₂CH₂NSiMe₃)-

i

(CH₂CH₂NC(O)N(SiMe₃)Ar′)}-{N(NPh₂)C(O)N(Ar′)}, in which the substrate has inserted into a Ti−N_amidebond of N₂O as

well as adding to the TiN_αmultiple bond. With Ar′NCS the [2+2] cycloaddition product Ti(N₂O){N(NPh₂)C(NAr′)S}(py)

was obtained, and with Ar′NCSe a mixture was formed including Ti₂(N₂O)₂(μ-Se)₂. Both 14 and 15 reacted with Ar^FxCN (Ar^Fx

= C₆H₃F₂or C₆F₅) to give TiN_αbond insertion products of the type Ti(L){NC(Ar^Fx)NNPh₂}(py)₂(L = N₂^ArO or N₂O)

containing hydrazonamide ligands. Reaction of 14 with XylNC (Xyl = 2,6-C₆H₃Me₂) gave only the isonitrile σ-adduct

t

Ti(N₂^ArO)(NNPh₂)(py)(CNXyl), whereas 15 underwent N_α−N_βbond reductive cleavage with BuNC or XylNC forming

Ti(N₂O)(NPh₂)(NCN^tBu) or Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NCN(SiMe₃)Xyl)}(NPh₂)(NCNXyl) (27). Both contain

metalated carbodiimide ligands, but in 27 an additional reaction of XylNC with the Ti−N_amidebond of N₂O has taken place.

Compound 15 also reacted with a number of internal alkynes RCCR′ (R = R′ = Me or Ph; R = Me, R′ = aryl) to give N_α−N_β

bond reductive cleavage products of the type Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(R)C(R′)NSiMe₃}(NPh₂), again involving a

reaction of a Ti−N_amidebond.

atom, cycloaddition to (or insertion into) the TiN_αbond,

INTRODUCTION

■

and also cleavage of (or insertion into) the N_α−N_β

The stoichiometric and catalytic chemistry of group 4 alkyl and

bond.^{7a−u,w−ac,8}

aryl imido complexes (L)MN−R (M = Ti, Zr, Hf; R = alkyl

Of the various types of supporting ligands used in group 4

hydrazido chemistry, one of the most eﬀective with regard to

or aryl; L = supporting ligand (set)) has been extensively

studied for over 20 years, as summarized in a series of reviews.¹

promoting new chemistry of the MN−NR₂functional group

The polar and unsaturated MN multiple bond (a σ²π⁴triple

bond in most cases²) can undergo a range of reactions with

both saturated and unsaturated substrates. In contrast, the

chemistry of group 4 dialkyl or diaryl hydrazido(2−)

compounds (L)MN-NR₂, ﬁrst reported by Wiberg (M =

Ti)³and Bergman (M = Zr),⁴was initially fairly slow to

develop, as has also been the case for their alkylidene hydrazido

(i.e., (L)MN−NCRR′)⁵and alkoxy imido (i.e., (L)M

N−OR)⁶counterparts. Nonetheless, in the past decade in

particular, a wide range of titanium⁷and zirconium and

hafnium⁸hydrazido complexes have been isolated or generated

in situ, and the small-molecule reaction chemistry of the M

N−NR₂functional group has been explored. In addition to

hydrohydrazination and related catalytic transformations

involving alkynes and allenes,^{7d−i,k,n,s,aa,ab,9}stoichiometric

reactions with a large number of substrates including CO,

has been the diamido-pyridine ligands (2-NC₅H₄)CMe-

( C H ₂N S i M e ₂R ) ₂( R

= )

M e ( N ₂N ^{p y}o r ^tB u

(N₂*N^py))^{7p,q,t,w,8a,c−g,i−m}or the closely related diamido-

amine ligand MeN(CH₂CH₂NR)₂(R = SiMe₃(N₂N^Me) or

ⁱPr)^{7m,p,t,u,w,ab}illustrated by way of example for complexes 1−4

in Figure 1. As shown by structural and DFT studies,^7pthe π-

donor N_amideatoms of N₂N^Me- and N₂N^py-type ligands tend to

destabilize the MN_αmultiple bond (again a σ²π⁴triple bond

in most cases^5f,7j,l,p,x). This, together with the relatively open

coordination sphere provided by these ligands, leads to a more

reactive MN−NR₂moiety and access to a range of reaction

products. Thus treatment of 3 with Ar′NCE (E = O, S, Se)

gives well-deﬁned TiN_α[2+2] cycloaddition products 5.^7t,w

However, with Ar^FxCN (Ar^Fx= C₆F₅or 2,6-C₆H₃F₂) the

corresponding cycloaddition products are not stable and the

TiN_αbond net insertion products 6 result.^7t,wAll of the

compounds 1−3 react with isonitriles to undergo N_α−N_βbond

t

isonitriles, nitriles, BuCP, alkynes, allenes and heteroallenes

(e.g., CO₂, CS₂, isocyanates, and their congeners), organic

azides, silanes and halosilanes, boranes, alkyl halides, and

Brønsted acids have been reported. These reactions lead to a

range of outcomes including addition to either the N_αor N_β

Received: April 11, 2013

Published: May 10, 2013

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Figure 1. Examples of group 4 hydrazido complexes supported by diamido-amine ligands (1−4) and selected reaction products with isocyanates,

nitriles, isonitriles, and alkynes. The atoms of the original MNNR₂group are shown in red, and those of the substrate are in blue.

cleavage and net N_αatom transfer to form a metalated

carbodiimide ligand (e.g., 7 and 8).^7t,w,8aFurthermore, with

alkynes a range of reaction products (9−11) can be isolated

depending upon the alkyne, metal, and supporting li-

gand.^{7m,q,t,8h,l,m}

use of these diamido-ether ligands as platforms for the synthesis

of titanium hydrazido complexes and their subsequent reactivity

with a representative range of small unsaturated molecules.

RESULTS AND DISCUSSION

■

Use of more sterically demanding versions of N₂N^Me

(Me₃SiN(CH₂CH₂NSiMe₃)₂or MeN(CH₂CH₂CH₂N-

SiMe₃)₂)^7por the four-coordinate version (2-NC₅H₄)CH₂N-

Synthesis of New Diphenyl Hydrazido Complexes

Supported by Diamido-Ether Ligands. The lithiated ligand

Li₂N₂^ArO was synthesized according to literature methods.¹¹

The new protio-ligand H₂N₂O (12) was synthesized starting

from O(CH₂CH₂NH₂)₂,¹²which was then silylated using

Me₃SiCl and Et₃N to form 12 as a colorless oil in 75% yield.

Lithiation using BuLi in hexanes on a multigram scale aﬀorded

Li₂N₂O (13) in 87% isolated yield as a colorless crystalline

solid. Diﬀraction-quality crystals of 13 were grown from a

pentane solution at RT. The molecular structure is shown in

Figure 3, and metric details are provided in the Supporting

Information.

7p

(CH₂NSiMe₃)₂tends to close down this reactivity or lead to

mixtures of reaction products.¹⁰In contrast, we very recently

showed that changing the N_amidesubstituent “R” from −SiMe₃

in 3 to −ⁱPr in 4 gave a change in reactivity from 1,2-

diamination catalysis^7m,t(via intermediates of the type 10) to

hydrohydrazination catalysis via an unprecedented titanium

acetylide/vinyl hydrazido(1−) resting state and intermediate.^7ab

Given the range of diﬀerent MN-NR₂group reactivity as a

function of supporting ligand sets (and the success of diamido-

amine-type ligands in general), we thought it would be of

interest to replace the neutral pyridyl or amine N-donors in the

N₂N^pyor N₂N^Meligands to (even) less sterically demanding

and weaker O-donor ether groups. We therefore modiﬁed the

N₂N^Meligand by introducing an oxygen in place of NMe to give

O(CH₂CH₂NSiMe₃)₂(referred to as “N₂O” hereafter). We also

used a diaryl version of this ligand, namely, O(2-C₆H₄NSiMe₃)₂

(“N₂^ArO”) reported previously by Schrock et al. in the

development of new group 4 oleﬁn polymerization catalysts.¹¹

Figure 2 shows the protio forms of the diamido-ether ligands

used and their abbreviations. In this contribution we report the

Compound 13 is dimeric in the solid state, consisting of two

crystallographically distinct Li₂N₂O moieties linked through

bridging Li atoms (Li(2) and Li(4)), resulting in an unusual

open cage-like structure. The Li−O and Li−N_amidedistances lie

within the expected ranges,¹³but analogous lithiated diamido-

amine ligands have ladder-like structures with the N_amideand Li

atoms in an approximately coplanar arrangement with the

N_aminedonors bound to only one Li atom.¹⁴In 13 the O donors

are able to bridge two Li atoms, therefore leading to a diﬀerent

structural motif. This ﬂexibility of the N₂O ligands in 13

compared to their N₂N^Meand related analogues is also

manifested in the structural and reaction chemistry of the

hydrazido complexes described later on. Interestingly, while

structurally characterized lithiated diamido-amine and mono-

amido-ether compounds are well established,¹³only one

example of a lithiated polyamine-ether has been reported

previously.¹⁵The H, ¹³C, and Li spectra of 13 at RT and at

−80 °C in toluene-d₈are consistent with a highly ﬂuxional

complex in solution, showing only one type of Li environment

(δ = 1.9 ppm) and apparent C_2vsymmetry at all temperatures.

1

7

Figure 2. Protio forms of the diamido-ether ligands used and their

abbreviations.

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ously^11,17that N₂^ArO can adopt either a fac or mer coordination

geometry, and its analogue N₂O appears to have the same

ﬂexibility. To explore this aspect further, we found that addition

t

of Bu-bipy (4,4′-di-tert-butyl-2,2′-bipyridyl) to 14, or bipy

(2,2′-bipyridyl) to 15, gave Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16)

or Ti(N₂^ArO)(NNPh₂)(bipy) (17), respectively, in 50% and

62% isolated yield. When followed on the NMR tube scale in

C₆D₆, the reactions were quantitative as expected. Compounds

1

16 and 17 exist as single isomers in solution, and the H and

¹³C NMR spectra are consistent with the C_s-symmetric

structures illustrated in Scheme 1, which were conﬁrmed by

X-ray crystallography (vide infra). The compounds each

contain a κ³-fac-bound diamido-ether ligand and are analogous

to the previously reported hydrazido and alkoxyimido

complexes of N₂N^Me, namely, Ti(N₂N^Me)(NNPh₂)(bipy) and

Ti(N₂N^Me)(NO^tBu)(bipy) (with NNPh₂or NO^tBu trans to

NMe), formed in a similar way from Ti(N₂N^Me)(NNPh₂)(py)^7t

or Ti(N₂N^Me)(NO^tBu)(py).^6b

Figure 3. Displacement ellipsoid plot (20% probability) of Li₂N₂O

(13). H atoms are omitted for clarity. See Figure S1 of the Supporting

Information for further details.

The solid-state structures of Ti(N₂^ArO)(NNPh₂)(py)₂(14)

and Ti(N₂O)(NNPh₂)(py)₂(15) are shown in Figure 4, and

those of Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16) and Ti(N₂^ArO)-

(NNPh₂)(bipy) (17) are given in Figure 5. Selected bond

distances and angles are listed in Table 1. Compound 15

crystallizes with three crystallographically independent mole-

cules in the asymmetric unit, but there are no chemically

signiﬁcant diﬀerences between the metric parameters and only

one set of values are listed in Table 1 (see Table S1 of the

Supporting Information for full details).

Complexes 14 and 15 have an approximately octahedral

titanium center, with the diamido-ether ligand coordinated

meridonally and the two pyridine ligands positioned mutually

trans. The Ti−N_pybond lengths are typical of neutral nitrogen

σ-only interactions with titanium.¹³The Ti(1)−N(1) bond

lengths of 1.739(3) and 1.736(4) Å for 14 and 15, with

approximately linear Ti(1)−N(1)−N(2) angles of 176.1(2)°

and 170.0(3)° suggest a formal TiN_αtriple bond as

expected.^7pThe N(1)−N(2) bond distances of 1.373(4) and

1.379(5) Å are within the usual range for group 4 hydrazides

and somewhat shorter compared to the N−N bond distance of

Ph₂NNH₂(1.418(2) Å),^7oconsistent with some residual

We have previously found that diamido-amine-supported

titanium diphenyl hydrazido complexes such as 1, 2, and 3

(Figure 1) can be conveniently prepared from Ti(NNPh₂)-

Cl₂(py)₃.^7p,abAs summarized in Scheme 1, reaction of Li₂N₂^ArO

or Li₂N₂O (13) with Ti(NNPh₂)Cl₂(py)₃in toluene at −40 or

−78 °C proceeds smoothly to yield Ti(N₂^ArO)(NNPh₂)(py)₂

(14) or Ti(N₂O)(NNPh₂)(py)₂(15) in 59% and 71% isolated

yield, respectively. The ¹H and ¹³C NMR spectra of 14 and 15

show resonances attributable to two chemically equivalent,

coordinated pyridine ligands, a NNPh₂moiety and a κ³-mer-

bound diamido-ether ligand. Each exists as the single isomer

illustrated in Scheme 1, possessing approximate C_2vsymmetry.

Diﬀraction-quality crystals of 14 and 15 were grown from

hexanes, and the solid-state structures (vide infra) conﬁrm

those shown in the scheme.

The κ³-mer coordination modes of the N₂^ArO and N₂O

ligands in 14 and 15 contrast with the κ³-fac coordination of the

diamido-amine ligands in 1, 2, and 3^7p,aband related imido¹⁶

and alkoxy-imido^6bcompounds. It has been shown previ-

Scheme 1. Synthesis of New Titanium Hydrazido Complexes Supported by Diamido-Ether Ligands

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Figure 4. Displacement ellipsoid plot (20% probability) of Ti(N₂^ArO)(NNPh₂)(py)₂(14) (left) and Ti(N₂O)(NNPh₂)(py)₂(15) (right). H atoms

are omitted for clarity.

Figure 5. Displacement ellipsoid plot (20% probability) of Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16) (left) and Ti(N₂O)(NNPh₂)(bipy) (17) (right). H

atoms are omitted for clarity.

multiple-bond character. The sum of angles subtended at N(2)

in both compounds is ca. 360°, indicating sp²hybridization and

conjugation of the N_βlone pair with the phenyl rings, a known

feature for diphenyl hydrazide ligands of the early transition

metals. These metric parameters for the TiNNPh₂ligands in

14 and 15 are similar to those found in other diamide-donor-

supported complexes such as 3.^7pThe Ti−N_amidebond

distances for 14 (Ti(1)−N(3 or 4) = 2.099(3) or 2.102(3)

Å) are slightly longer than those in 15 (2.081(4) or 2.054(3)

Å), and both are longer than in Ti(N₂N^Me)(NNPh₂)(py) (3)

(2.029(5) or 2.026(5) Å), reﬂecting the diﬀerent coordination

geometry and number in the diamido-ether complexes. Both

N_amideatoms are approximately trigonal planar, as indicated by

the sum of the angles subtended at N(3) and N(4) being ca.

360°. Finally we note that the Ti(1)−O(1) distances are within

the expected ranges.¹³The solid-state structures of the bipyridyl

complexes 16 and 17 also feature approximately octahedral

titanium centers but with the diamido-ether ligand κ³-fac

coordinated. The TiN_α, Ti−O, and Ti−N_amidebond lengths

are similar to those in 14 and 15 and are comparable to those in

Ti(N₂N^Me)(NNPh₂)(bipy).^7tThe similarity of the metric

parameters of bis(pyridine) and bipyridyl structures suggest

that both mer- and fac-coordination modes should be accessible

to the diamido-ether ligands in 14 and 15 during reaction

sequences.

Reaction with Isocyanates. As a starting point for

reactivity studies of 14 and 15, we chose to probe their

reactions with isocyanates and their heavier sulfur and selenium

congeners. Group 4 imido complexes have a well-established

chemistry with isocyanates and other heterocumulenes,^1b,c,e,18

and these reactions can lead to isolated [2+2] cycloaddition

products or cycloaddition−extrusion (net metathesis of M

NR with ECE′ (E and/or E′ = O, S, NR) or “double

insertion”, in which two heterocumulene moieties eﬀectively

insert into the MNR multiple bond. Group 4 hydrazides also

have an established and, in many ways, similar chemistry with

allenes and heterocumulenes both for titanium^{5f,7a,o,r,u,w,z}and

its heavier congeners.^8i−kBy way of example, Figure 1 shows

the reaction products (compounds of the type 5) of

Ti(N₂N^Me)(NNPh₂)(py) (3) with Ar′NCE (E = O, S, Se;

7w

i

Ar′ = 2,6-C₆H₃Pr₂). The bulky Ar′ group was necessary to

prevent unwanted side-reactions such as insertion into the Ti−

N_amidebonds, which is a known complication with diamide-

donor supporting ligand sets and these substrates for a number

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Table 1. Selected Bond Lengths (Å) and Angles (deg) for

Ti(N₂^ArO)(NNPh₂)(py)₂(14), Ti(N₂O)(NNPh₂)(py)₂(15),

Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16), and

Scheme 2. Reactions of Ti(N₂O)(NNPh₂)(py)₂(15) with

Ar′NCE (Ar′ = 2,6-C₆H₃Pr₂; E = O, S, or Se)

i

Ti(N₂O)(NNPh₂)(bipy) (17)

14

15

16

17

Ti(1)−N(1)

Ti(1)−N(3)

Ti(1)−N(4)

Ti(1)−N(5)

Ti(1)−N(6)

Ti(1)−O(1)

N(1)−N(2)

1.739(3)

2.099(3)

2.102(3)

2.276(3)

2.266(3)

2.180(2)

1.373(4)

176.1(2)

1.736(4)

2.081(4)

2.054(3)

2.315(4)

2.273(4)

2.217(3)

1.379(5)

178.0(3)

1.734(3)

2.073(3)

2.100(3)

2.259(3)

2.252(3)

2.221(3)

1.366(5)

169.0(3)

1.743(2)

2.039(2)

2.045(2)

2.278(2)

2.304(2)

2.297(2)

1.371(3)

170.86(16)

Ti(1)−N(1)−

N(2)

N(1)−Ti(1)−

107.20(12)

105.07(13)

100.52(12)

98.80(12)

178.55(11)

74.18(10)

73.54(10)

79.96(10)

80.75(10)

147.69(11)

160.65(11)

105.08(16)

103.56(16)

95.60(15)

96.26(16)

179.0(3)

106.25(15)

108.65(15)

95.75(15)

88.97(14)

171.41(14)

78.72(12)

76.32(12)

77.26(11)

84.08(11)

103.91(13)

71.30(12)

108.43(8)

102.51(8)

90.20(8)

95.11(8)

173.12(8)

77.76(7)

78.09(7)

87.29(6)

78.01(6)

106.25(8)

70.32(7)

N(3)

N(1)−Ti(1)−

N(4)

N(1)−Ti(1)−

N(5)

N(1)−Ti(1)−

N(6)

N(1)−Ti(1)−

O(1)

N(3)−Ti(1)−

75.12(13)

76.24(13)

84.65(12)

83.49(13)

151.3(2)

O(1)

N(4)−Ti(1)−

O(1)

N(5)−Ti(1)−

O(1)

N(6)−Ti(1)−

O(1)

N(3)−Ti(1)−

N(4)

N(5)−Ti(1)−

168.1(1)

group migration from the N_amideatom of the N₂O ligand to the

isocyanate-derived nitrogen. This overall type of sequence has

been observed for a number of imido complexes including

Ti(N₂N^py)(N^tBu)(py), M(N₂N^py)(N^tBu)Cl(py) (M = Nb or

Ta), and [W(N₂N^py)(NPh)Me]⁺, including direct observation

of the intermediate formed prior to SiMe₃group migration.¹⁹

The solution-state structure of 18 was unequivocally established

by 1D and 2D and NOE NMR spectroscopy, allowing the full

N(6)

of early transition metals.¹⁹Using these same Ar′NCE

substrates we found that complicated mixtures of unknown

products were formed with Ti(N₂^ArO)(NNPh₂)(py)₂(14)

when assessed on the NMR tube scale in C₆D₆, so no further

reactions were attempted with this complex. More success was

found with Ti(N₂O)(NNPh₂)(py)₂(15), as shown in Scheme

2.

1

assignment of the H and ¹³C NMR spectra. An IR band at

1658 cm⁻¹, absent in 15 and the intermediate 19 (vide infra),

was assigned to ν(CO) of the ureate moiety by comparison

with literature examples.^7a

Addition of 1 equiv of Ar′NCO to 15 on the NMR tube scale

in C₆D₆consumed all of the isocyanate to form a single new

product (18) but with half of the 15 remaining apparently

unreacted. Addition of a further equivalent of substrate gave

complete conversion to the new product along with 2 equiv of

free pyridine. The reaction was successfully scaled up using 2

equiv of Ar′NCO in benzene at RT to give Ti{O-

(CH₂CH₂NSiMe₃)(CH₂CH₂NC(O)N(SiMe₃)Ar′)}{N-

(NPh₂)C(O)N(Ar′)} (18, Scheme 2) in 46% isolated yield.

Single crystals were obtained but diﬀracted poorly (overall I/

σ(I) = 0.8 for the diﬀraction data) but could nonetheless be

used to establish the connectivity as shown in the scheme (see

also Figure S2 of the Supporting Information). The solid-state

structure conﬁrms that 2 equiv of Ar′NCO have been

incorporated. One Ar′NCO has evidently undergone a [2+2]

cycloaddition with the TiNNPh₂bond, forming a κ²N,N′-

coordinated ureato moiety, {N(NPh₂)C(O)N(Ar′)}, of the

type observed previously,^7aalthough κ²N,E-bound ureate-type

ligands (E = O, S, Se) are usually preferred on steric

grounds.^7r,wThe other Ar′NCO group has reacted with one

of the Ti−N_amidebonds followed by a 1,3-sigmatropic SiMe₃

The reaction between 15 and 1 equiv of Ar′NCO was

followed in CD₂Cl₂from −78 °C to ca. 0 °C, at which

temperature a reaction proceeded to consume all of the

Ar′NCO and also the 15, giving a C₁-symmetric species

assigned as the Ti−N_amideinsertion product Ti{O-

(CH₂CH₂NSiMe₃)(CH₂CH₂N(SiMe₃)C(O)NAr′)}(NNPh₂)

(19), shown in Scheme 2. Addition of a further equivalent of

Ar′NCO and warming to RT forms 18 as expected.

Interestingly, warming the solution of 19 to RT in the absence

of additional Ar′NCO gave half of an equivalent of starting

hydrazide 15 and also of 18. Thus the reaction of 15 with

Ar′NCO to form 19 appears to be reversible. It was

nonetheless possible to prepare 19 on the preparative scale

by using 1:1 stoichiometric quantities of 15 and Ar′NCO at

temperatures below 0 °C and then crystallizing at −78 °C. In

this manner 19 was isolated as an analytically pure solid in 61%

yield, which is stable for days at RT in the solid state.

Reaction of 15 with Ar′NCS proceeds smoothly at RT to

yield the [2+2] cycloaddition product Ti(N₂O){N(NPh₂)C-

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(NAr′)S}(py) (20) in 57% yield (Scheme 2). This complex is

the analogue of the diamido-amine complexes Ti(N₂N^Me){N-

(NPh₂)C(NAr′)E}(py)_n(5; E = O, n = 1; E = S or Se, n = 0)^7w

and Zr(N₂*N^py){N(NPh₂)C(NAr′)S}(py)_n(n = 0 or 1).^8kThe

molecular structure of 20 is shown in Figure 6 along with

Figure 7. Displacement ellipsoid plot (20% probability) of

Ti₂(N₂O)₂(μ-Se)₂(21). H atoms are omitted for clarity. Selected

bond lengths (Å) and angles (deg): Ti(1)−Se(1A) 2.460(1), Ti(1)−

Se(1) 2.429(1), Ti(1)−N(1) 1.902(7), Ti(1)−N(2) 1.924(6), Ti(1)−

O(1) 2.359(5), Se(1A)−Ti(1)−Se(1) 93.5(5), Ti(1A)−Se(1)−Ti(1)

86.5(5), Se(1)−Ti(1)−O(1) 176.7(2), N(1)−Ti(1)−N(2) 115.8(3).

Ar′NCNNPh₂,^7zwhich was observed among the reaction

products but not isolated.

Figure 6. Displacement ellipsoid plot (20% probability) of Ti(N₂O)-

{N(NPh₂)C(NAr′)S}(py) (20). H atoms are omitted for clarity.

Selected bond lengths (Å) and angles (deg): Ti(1)−S(1) 2.419(1),

Ti(1)−O(1) 2.240(2), Ti(1)−N(1) 2.051(3), Ti(1)−N(4) 1.954(3),

Ti(1)−N(5) 1.959(3), Ti(1)−N(6) 2.289(3), N(1)−N(2) 1.408(4),

S(1)−C(13) 1.777(3), N(1)−C(13) 1.360(5), N(3)−C(13)

1.280(4), N(4)−Ti(1)−N(5) 130.7(1), Ti(1)−S(1)−C(13) 81.6(1),

S(1)−Ti(1)−N(1) 66.9(8), S(1)−C(13)−N(1) 103.8(2).

Structurally authenticated titanium selenido-bridged dimers

are relatively rare, and 21 represents only the third example.²⁰

The metric parameters of the Ti₂Se₂core are similar to those

found in Ti₂(μ-Se)₂{Ar′NCH₂CH₂CH₂NAr′}₂, synthesized by

Piers et al. from Ti{Ar′NCH₂CH₂CH₂NAr′}Me₂and elemental

selenium.^20bThe Ti−Se bonds in 21 are slightly dissimilar in

length (Ti(1)−Se(1) = 2.429(1) Å, Ti(1)−Se(1A) = 2.460(1)

Å), which distorts the Ti₂Se₂core to some extent (Se(1A)−

Ti(1)−Se(1) = 93.5(5), Ti(1A)−Se(1)−Ti(1) = 86.5(5)°).

Reaction with Organic Nitriles. The reactions of organic

nitriles with transition metal imides (L)MNR are almost

unknown and give rise to dimeric complexes of the type

(L)₂Ti₂{μ-NC(R′)(NR)}₂.²¹This is in contrast to the position

for metal nitrides,²²alkylidenes,²³and alkylidynes.²⁴We found

recently that Ti(N₂N^py)(NNPh₂)(py) (1) reacts with MeCN to

give an analogous dimeric species, whereas Ti(N₂N^Me)-

(NNPh₂)(py) (3) gave mixtures with this substrate or

PhCN.^7wHowever, reaction of both 1 and 3 with ﬂuorinated

benzonitriles Ar^FxCN (Ar^Fx= Ar^F2(2,6-C₆H₃F₂) or Ar^F5

(C₆F₅)) gave unexpected TiN_αinsertion products such as

Ti(N₂N^Me){NC(Ar^Fx)NNPh₂}(py) (6, Figure 1), containing a

hydrazonamide ligand. DFT studies showed that this reaction

proceeds via a cycloaddition/reverse cycloaddition reaction

sequence. Mono- and dimetalated hydrazonamides have been

reported by sequential reaction of AlMe₃or dialkyl zincs with

Me₂NNH₂and MeCN, forming polynuclear clusters.²⁵Very

recently we found that the alkylidene hydrazido complex

Cp*Ti{MeC(NⁱPr)₂}(NNCPh₂) reacted with 2 equiv of ArCN

(Ar = Ph or Ar^F5) to form unusual “double insertion” products,

Cp*Ti{MeC(NⁱPr)₂}{N(NCPh₂)C(Ar)NC(Ar)N}.^5f

selected bond lengths and angles. The NMR spectra and other

data are fully consistent with the solid-state structure, and when

followed on the NMR tube scale, the reaction was quantitative.

Compound 20 contains a κ³-fac-coordinated N₂O ligand and a

κ²N,S-coordinated thioureato moiety as unambiguously estab-

lished by the solid-state structure. The main diﬀerence between

Ti(N₂N^Me){N(NPh₂)C(NAr′)S} and 20 is the presence of a

coordinated pyridine ligand, possibly suggesting a reduced

electron-donating capacity or steric proﬁle of the N₂O ligand

compared to N₂N^Me, although we note that Gade was able to

isolate Zr(N₂*N^py){N(NPh₂)C(NAr′)S}(py)_neither with or

without a coordinated pyridine ligand.^8kThe distances and

angles associated with the N(NPh₂)C(NAr′)S moiety in 20 are

comparable to those in the related complexes, and the

parameters associated with the titanium coordination center

are likewise analogous to those in the complex 5 in general and

the starting complex 15.

Whereas the thioureate complex 20 is stable for days in

solution at RT, reaction with Ar′NCSe yielded a mixture of

products from which the μ-selenido-bridged dimer

Ti₂(N₂O)₂(μ-Se)₂(21) was crystallized from Et₂O solution at

−30 °C as a few red, diﬀraction-quality crystals. The molecular

structure of 21 is shown in Figure 7 together with selected

bond lengths and angles. It was not possible to obtain a pure

sample of 21 because it crystallized among oily side-products

and could not be separated. The formation of the bridged

dimer is thought to occur via [2+2] cycloaddition of Ar′NCSe

to the TiNNPh₂bond (forming an intermediate analogous

to 20) and Ti(N₂N^Me){N(NPh₂)C(NAr′)Se}), followed by

retro-cycloaddition and extrusion of the organic product

Compounds 14 and 15 gave unknown mixtures with PhCN

but with Ar^F5CN or Ar^F2CN (for 15) clean and quantitative

(when followed by NMR in C₆D₆) conversion to the new

terminal hydrazonide complexes Ti(N₂^ArO){NC(Ar^F5)-

NNPh₂}(py)₂(22), Ti(N₂O){NC(Ar^F5)NNPh₂}(py)₂(23),

and Ti(N₂O){NC(Ar^F2)NNPh₂}(py)₂(24) within 2 to 3 h.

The reaction for 14 proceeded readily at RT (as was the case

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Figure 8. Displacement ellipsoid plot (20% probability) of Ti(N₂^ArO){NC(Ar^F5)NNPh₂}(py)₂(22) (left) Ti(N₂O){NC(Ar^F5)NNPh₂}(py)₂(23)

(right). H atoms are omitted for clarity.

with the diamido-amine complexes 1 and 3), whereas that with

15 required heating at 70 °C. The new compounds were

isolated in 47−52% yield on the preparative scale, and

diﬀraction-quality crystals of 22 and 23 were obtained. The

molecular structures are shown in Figure 8, and selected bond

lengths and angles are compared in Table 2. The solid-state

Scheme 3. Reactions of Ti(N₂^ArO)(NNPh₂)(py)₂(14) and

Ti(N₂O)(NNPh₂)(py)₂(15) with Ar^FxCN (Ar^Fx= 2,6-

C₆H₃F₂or C₆F₅)

Table 2. Selected Bond Lengths (Å) and Angles (deg) for

Ti(N₂^ArO){NC(Ar^F5)NNPh₂}(py)₂(22) and

Ti(N₂O){NC(Ar^F5)NNPh₂}(py)₂(23)

22

23

Ti(1)−N(1)

Ti(1)−N(4)

Ti(1)−N(5)

Ti(1)−N(6)

Ti(1)−N(7)

Ti(1)−O(1)

N(1)−C(1)

C(1)−C(2)

1.760(2)

2.059(2)

2.071(2)

2.237(2)

2.231(2)

2.222(2)

1.356(3)

1.514(4).

1.298(2)

1.432(3)

173.7(2)

173.72(9)

145.92(9)

103.84(9)

109.94(9)

169.60(8)

74.71(8)

89.69(8)

80.59(7)

121.2(2)

115.4(2)

123.4(2)

114.1(2)

1.774(2)

2.022(2)

2.029(2)

2.247(2)

2.288(2)

2.221(2)

1.342(3)

1.518(4)

1.304(3)

1.447(3)

170.0(2)

173.20(9)

149.61(9)

105.20(10)

105.19(9)

174.36(8)

74.68(8)

90.77(8)

84.53(8)

122.2(2)

115.9(2)

121.9(2)

113.5(2)

C(1)−N(2)

N(2)−N(3)

Ti(1)−N(1)−C(1)

O(1)−Ti(1)−N(1)

N(4)−Ti(1)−N(5)

N(1)−Ti(1)−N(4)

N(1)−Ti(1)−N(5)

N(6)−Ti(1)−N(7)

N(5)−Ti(1)−O(1)

N(6)−Ti(1)−O(1)

N(7)−Ti(1)−O(1)

N(1)−C(1)−N(2)

N(1)−C(1)−C(2)

N(2)−C(1)−C(2)

C(1)−N(2)−N(3)

Compounds 22 and 23 have an approximately octahedral

titanium center bonded to terminal hydrazonamido ligands.

Their overall geometries are very similar to those of their

hydrazido precursors 14 and 15 with κ³-mer coordination

modes of the N₂^ArO and N₂O ligands and mutually trans

pyridines. The Ti−N_pyand Ti−O distances in 22 and 23 are

not signiﬁcantly diﬀerent from those in 14 and 15. The N_amide

atoms of the N₂^ArO and N₂O ligands are trigonal planar,

implying sp²hybridization. The Ti(1)−N(1)−C(1) linkages

are approximately linear (Ti(1)−N(1)−C(1) = 173.7(2)° or

170.0(2)°), implying sp hybridization at the new N_αatom. The

Ti−N_αdistances in 22 and 23 (1.760(2) and 1.774(2) Å) are

signiﬁcantly longer than in their hydrazido analogues 14 and 15

(1.739(3) and 1.736(4) Å), suggesting reduced TiN_α

multiple-bond character (the Ti−N(1) bond lengths are

nonetheless still indicative of a formal TiN_αtriple bond).

The Ti−N_amidedistances in 22 and 23 (av 2.060(2) and

2.025(2) Å) are, in contrast, shorter than their counterparts in

structures and solution NMR and other data are consistent with

the structures illustrated in Scheme 3. No intermediate species

were observed when followed by NMR. It is assumed, based on

our previous studies,^7wthat the reactions proceed via [2+2]

cycloaddition reactions between TiNNPh₂and the nitrile

followed by reverse cycloaddition to give an overall net

insertion reaction of Ar^FxCN into TiN_α.

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14 and 15 (av 2.101(2) and 2.067(3) Å), indicating better

N_amide→ Ti π-donation. This would follow from the longer

TiN_αbonds. Analogous features were previously found for

the diamido-amine analogues 6 in comparison with their

hydrazido starting material 3 and can be attributed to the

electron-withdrawing nature of the −C(Ar^Fx)NNPh₂groups

bound to N_αin these hydrazonamido complexes. A degree of

multiple bonding is indicated by the N(1)−C(1) (1.356(3) and

1.342(3) Å) and N(2)−C(1) (1.298(2) and 1.304(3) Å) bond

lengths. The N(2)−C(1) formal double bond has the shorter

bond distance of the two, conﬁrming the valence bond

representations in Scheme 3.

with 1 equiv of ^tBu-bipy in C₆D₆immediately formed

Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16) and free XylNC and

pyridine, consistent with the proposed structure of 25. Finally,

t

preliminary studies of the reaction between 14 and BuNC on

the NMR tube scale immediately gave a similar spectrum to

that of 25, indicative of adduct formation, either at RT or on

heating. This reaction was not scaled up.

In contrast to the limited reactivity of 14, compound 15

undergoes N_α−N_βbond cleavage and new Ti−C and/or N−C

bond forming reactions with ^tBuNC and XylNC, as

summarized in Scheme 4. On the NMR tube scale no reaction

Overall, the geometries within the hydrazonamide fragments

are similar to those we reported previously for 6 and its

analogues. Close contacts are also observed between certain

carbons in the C₆F₅rings and those of the pyridine ligands or

one carbon of the NNPh₂rings (for 22 C(36)···C(4) =

3.474(5) Å, C(35)···C(3) = 3.376(4) Å, and C(2)···C(8) =

2.964(4) Å; for 23 C(47)···C(3) = 3.507(5) Å and C(2)···C(8)

= 2.948(4) Å). Such π-stacking-type interactions are well

known in general for ﬂuorinated aryl rings,²⁶including between

the N-substituents of titanium imido compounds,²⁷and were

observed in Ti(N₂N^Me){NC(Ar^F5)NNPh₂}(py).^7w

Scheme 4. Reactions of Ti(N₂O)(NNPh₂)(py)₂(15) with

Isonitriles

Reactions with Isonitriles. One of the distinctive types of

reaction of certain group 4 diphenyl- and alkylidene-hydrazido

complexes is their propensity to undergo reductive N_α−N_β

bond cleavage with oxidizable substrates. This was ﬁrst

observed by Bergman and Andersen for the reactions of

Cp₂Zr(NNPh₂)(DMAP)⁴or Cp*₂Ti{η²-NNC(H)Tol}^5cwith

CO, giving mixed diphenylamide/isocyanate or alkylidene

imido/isocyanate products Cp₂Zr(NPh₂)(NCO) and Cp*₂Ti-

(NCO){NC(H)Tol}, respectively. Subsequently, both Gade^8a

and then our group^7wfound that reactions of XylNC (Xyl =

2,6-C₆H₃Me₂) or BuNC with Ti(N₂N^py)(NNPh₂)(py) (1),

t

Zr(N₂*N^py)(NNPh₂)(py) (2), and Ti(N₂N^Me)(NNPh₂)(py)

(3) gave mixed diphenylamide-metalated carbodiimide com-

plexes such as 7 and 8 (Figure 1). Our DFT studies found that

the reactions for 1 and 3 (and most likely the other example

mentioned) proceed via RNC addition to MN_afollowed by

NR₂transfer to the metal and N_α−N_βbond cleavage.^7w

t

was observed at RT between a 1:1 mixture of 15 and BuNC.

However, after heating for three days at 70 °C a single new

product, Ti(N₂O)(NPh₂)(NCN^tBu) (26), was formed along

with 2 equiv of free pyridine. No further reaction was observed

when an excess of ^tBuNC was used, and no intermediates were

observed. The reaction was scaled up (Scheme 4) to give 26 in

46% isolated yield. The NMR and IR spectra for 26 (band for

ν(NCN^tBu)^7wat 2102 cm⁻¹) are indicative of a C_s-symmetric

complex possessing a fac-coordinated N₂O ligand (two types of

CH₂environment with diastereotopic hydrogens), a new

NCN^tBu ligand, and a NPh₂moiety, as illustrated in Scheme

4.^7wThe solid-state structure of 26 is shown in Figure 9, along

with selected bond distances and angles, and is consistent with

the spectroscopic and other analytical data.

Reaction of 14 with an excess of XylNC at RT in C₆D₆

resulted in quantitative substitution of one pyridine ligand and

formation of the XylNC σ-adduct Ti(N₂^ArO)(NNPh₂)(py)-

(CNXyl) (25). No further reaction was observed even upon

prolonged heating at 80 °C in C₆D₆. The scaled-up reaction (eq

1) aﬀorded 25 in 62% isolated yield as a crystalline, brown

Compound 26 contains a ﬁve-coordinated titanium center

possessing a trigonal bipyramidal geometry. In addition to the

fac-coordinated N₂O ligand (occupying one axial and two

equatorial sites) there is an equatorially positioned NPh₂group

and the expected metalated carbodiimide fragment, which is

positioned trans to the O donor of the diamido-ether ligand. An

analogous structure was found for Ti(N₂N^Me)(NPh₂)-

(NCNXyl), prepared from Ti(N₂N^Me)(NNPh₂)(py) (4) and

XylNC,^7walthough this compound formed much more readily

(3 h at RT), as were the diamido-pyridine complexes 7 and 8

(Figure 1). Interestingly, 8 has the NCNR ligand positioned in

the equatorial plane and NPh₂located axially,^8awhereas 7 exists

as two positional isomers in a ca. 3:2 ratio.^7wThe metric data

for 26 are comparable to those of Ti(N₂N^Me)(NPh₂)-

(NCNXyl). As mentioned, the N₂O ligand is fac coordinated

powder. The ¹H and ¹³C NMR spectra are consistent with a C_s-

symmetric octahedral complex in solution, with one bound

pyridine remaining. The assignment of 25 as an σ-adduct is

supported by its IR spectrum, which shows a band for ν(N

C) at 2159 cm⁻¹, which is higher than that for the free ligand (ν

= 2110 cm⁻¹). The increased ν(CN) compared to the

uncoordinated isonitrile is consistent with coordination to the

electron-deﬁcient titanium in 25.^5f,28In addition, reaction of 14

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Figure 10. Displacement ellipsoid plot (20% probability) of

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NCN(SiMe₃)Xyl)}(NPh₂)-

(NCNXyl) (27). H atoms are omitted for clarity. Selected bond

lengths (Å) and angles (deg): Ti(1)−N(1) 2.021(3), Ti(1)−N(2)

1.969(3), Ti(1)−N(3) 1.883(3), Ti(1)−N(4) 1.971(3), Ti(1)−C(23)

2.079(3), N(1)−C(32) 1.151(5), N(5)−C(32) 1.267(6), N(4)−

C(23) 1.291(5), N(4)−C(14) 1.463(5), N(6)−C(23) 1.349(5),

N(3)−Ti(1)−N(4) 99.9(1), Ti(1)−N(1)−C(32) 168.4(3), N(1)−

C(32)−N(5) 167.4(4), Ti(1)−N(4)−C(23) 76.0(2), Ti(1)−C(23)−

N(4) 66.9(2), N(4)−Ti(1)−C(23) 37.1(1).

Figure 9. Displacement ellipsoid plot (30% probability) of Ti(N₂O)-

(NPh₂)(NCN^tBu) (26). H atoms are omitted for clarity. Selected

bond lengths (Å) and angles (deg): Ti(1)−O(1) 2.188(1), Ti(1)−

N(1) 1.909(2), Ti(1)−N(2) 1.960(2), Ti(1)−N(4) 1.944(2), Ti(1)−

N(5) 1.954(2), N(1)−C(13) 1.210(2), N(3)−C(13) 1.213(2),

N(4)−Ti(1)−N(5) 122.3(7), Ti(1)−N(1)−C(13) 179.7(2), N(1)−

C(13)−N(3) 172.9(2).

and the O(1)−Ti(1)−N(1) linkage is almost linear. The

Ti(1)−N(4,5) bonds for the N₂O ligand in 26 (av 1.949(2) Å)

are shorter than in 15 (av 2.067(3) Å), reﬂecting the lower

coordination number of titanium and the absence of the

strongly π-donating NNPh₂ligand in the latter. The Ti(1)−

N(2) distance of 1.960 Å is comparable as expected, and all

three equatorially positioned N_amideatoms have a trigonal

planar geometry and sp²hybridization.

NCNXyl ligands, while a second has reacted with one of the

Ti−N_amidebonds to the N₂O ligand with concomitant SiMe₃

group migration to form a new metalated amidinyl functional

group. It is unclear in what order the two equivalents react, as

no intermediates were observed. The ¹³C NMR resonance for

the Ti-bound carbon (C(23) in Figure 10) was found at 203.9

ppm, which is characteristic for metal-bound η²-RCNCR₂

ligands.²⁹

The Ti(1)−N(1) distance (1.909(2) Å) for the NCN^tBu

group is somewhat shorter than those in Ti(N₂N^py)(NPh₂)-

(NCN^tBu) (1.973(6) Å) and Ti(N₂N^py)(NPh₂)(NCNXyl)

(1.970(3) Å), which probably reﬂects the weaker trans

inﬂuence of the axial O-donor for N₂O compared to the

pyridyl or tertiary amine donors in these previous complexes. A

number of metalated carbodiimides of the type (L)M-NCNR

have been structurally characterized.¹³The N(1)−C(13) and

C(13)−N(3) distances are within the usual ranges for these

other examples. Similar observations were made for Ti-

(N₂N^Me)(NPh₂)(NCNXyl) and Ti(N₂N^py)(NPh₂)(NCN^tBu)

As shown in Figure 10, compound 27 contains an

approximately square-based pyramidal Ti center with the

diphenylamido ligand occupying the apical site. The square

base is formed by N(1) of the metalated carbodiimide ligand

and the former N₂O ligand acting as a tridentate ligand that

binds though one silyl amide (N(3)) and one η²-N,C-bound

amidinyl functional group (N(4), C(23)). The ether oxygen

O(1) does not coordinate to the metal center, as evidenced by

the O(1)···Ti(1) distance of 3.576(3) Å. The Ti−N(1−4)

bond distances are within the range found for Ti−N single

bonds in general.¹³The Ti−NPh₂distance of 1.969(3) Å is the

same as in 26, whereas Ti−NCNXyl (2.021(3) Å) is longer

than in 26 (1.909(2) Å) or Ti(N₂N^py)(NPh₂)(NCNXyl)

(1.970(3) Å). The N(4)−C(23) distance of 1.291(5) Å in the

η²-C,N-bound amidinyl moiety is consistent with a formal

double bond and signiﬁcantly shorter than N(4)−C(14)

(1.463(5) Å) or N(6)−C(23) (1.349(5) Å), the latter showing

evidence of conjugation from the trigonal planar N(6). The

Ti(1)−N(4) and Ti(1)−C(23) distances of 2.021(3) and

2.079(3) Å indicate signiﬁcant bonding interactions with both

of these atoms in the amidinyl moiety.

t

As for the reaction with BuNC, no reaction occurred

between Ti(N₂O)(NNPh₂)(py)₂(15) and XylNC (1 equiv) at

RT in C₆D₆. Heating at 70 °C for 14 h consumed all of the

isonitrile but only half of the hydrazido complex, leading to a

single new product, 27 (no intermediates or other species were

observed). Addition of a further equivalent of XylNC gave

complete conversion of 15. The reaction was scaled up to give

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NCN(SiMe₃)Xyl)}(NPh₂)-

(NCNXyl) (27, Scheme 4) in 50% yield. Although the NMR

and IR data for 27 were consistent with new NPh₂and

NCNXyl (ν(NCNXyl) at 2129 cm⁻¹) groups being formed, the

NMR spectra showed a further set of xylyl group resonances,

along with two SiMe₃groups and four inequivalent CH₂

linkages with diastereotopic hydrogens. The data are consistent

with the structure proposed for 27 in Scheme 4, which is

supported by X-ray crystallography (Figure 10). Compound 27

is reminiscent of that of 18 (Scheme 2), formed from 15 and 2

equiv of Ar′NCO. Thus 1 equiv of XylNC has reductively

cleaved the N_a−N_bbond of 15, forming new NPh₂and

Reaction with Alkynes. As was described in the

Introduction, their stoichiometric and catalytic reactions with

alkynes has been one of the main focuses of interest in group 4

hydrazido compounds.^{4,7d−i,k,m,n,q,s,t,aa,ab,8h,l,m,9b}For the diami-

do-amine-supported complexes 1−3 the chemistry has been

particularly rich, aﬀording a variety of reaction products as

exempliﬁed by 9−11 (Figure 1).^{7m,q,t,8h,l,m}Under appropriate

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catalytic conditions these types of compounds are intermediates

in alkyne hydrohydrazination,^7ab1,2-diamination,^10bor indole

synthesis.^4,8l,mThe sensitivity of the reaction outcome of

titanium hydrazides to the particular diamide-donor ligand type

is exempliﬁed by the reactions of 1 (diamide-pyridine ligand)

and 3 (diamido-amine ligand type): with the former, [2+2]

cycloaddition products were obtained (cf. 9) for internal and

terminal alkynes; for the latter, only N_α−N_βinsertion products

could be isolated, and only for internal alkynes. Therefore we

were interested in exploring the reactions of Ti(N₂^ArO)-

(NNPh₂)(py)₂(14) and Ti(N₂O)(NNPh₂)(py)₂(15) with

various representative alkynes.

Unfortunately 14 did not react with terminal or internal

alkynes (TolCCH, MeCCMe, PhCCMe, (4-C₆H₄CF₃)CCMe,

or PhCCPh) at RT in benzene or toluene. Upon heating to 70

°C, these reactions yielded unknown mixtures of products. In

contrast, 15 did show interesting reactivity with internal alkynes

at elevated temperatures, although again no reaction occurred

at RT. This is in contrast to the reactions of 1 and 3 with the

same substrates that occur at RT or below.^7m,tThe reactions of

15 with the internal alkynes ArCCMe (Ar = Ph, 4-C₆H₄OMe,

or 4-C₆H₄CF₃), PhCCPh, and MeCCMe are summarized in

Scheme 5. The reactions were initially assessed on the NMR

4-C₆H₄CF₃(30); R = Ar = Ph (31)) or Ti{O-

(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)-C(Me)NSiMe₃)}-

(NPh₂) (two isomers: 32-exo and 32-endo) in ca. 40−80%

1

isolated yield. The H and ¹³C NMR spectra of 28−32 are

consistent with the C₁-symmetric complexes depicted in

Scheme 5. Each shows resonances for a new NPh₂moiety, a

ArCCR (R = Me or Ph) or MeCCMe moiety, inequivalent

SiMe₃groups, and four inequivalent CH₂groups with

diastereotopic hydrogens. These spectral features are reminis-

cent of those for the Ar′NCO- and XylNC-derived products 18

and 27 described above (Schemes 2 and 4). The solid-state

structures (vide infra) support those depicted in Scheme 5.

Overall, in compounds 28−32 the hydrazide ligand in 15 has

undergone reductive N_α−N_βbond cleavage to form a new Ti−

NPh₂moiety, presumably (based on our previous detailed

mechanistic studies^7t) via a [2+2] cycloaddition product of the

type Ti(N₂O){N(NPh₂)C(R)CR′}(py) (34, not observed).

However, rather than forming a N_α−N_βbond insertion species

such as Ti(N₂O){NC(R′)C(R)NPh₂}(py) (35, the analogue of

10 in Figure 1), the observed products show the net insertion

of a RCCR′N moiety into one of the N−SiMe₃bonds of the

N₂O ligand. In addition, in the case of the products 28−30

formed with the unsymmetrical alkynes ArCCMe, the

regiochemistry of this net insertion reaction is very speciﬁc

with the CMe carbon bound to the N₂O-derived N atom

(Scheme 5). We recently reported an analogous reaction of the

titanium alkoxyimido complex Ti(N₂N^Me)(NO^tBu)(py) with

PhCCMe to give Ti{MeN(CH₂CH₂NSiMe₃)(CH₂CH₂NC-

(Me)C(Ph)NSiMe₃)}(NPh₂) (36).^6aDFT calculations found

that 36 was formed via azirinyl intermediate Ti(N₂N^Me){NC-

(Me)C(Ph)}(O^tBu) (37) followed by attack by an N_imideatom

of the N₂N^Meligand on the azirine ligand and then a 1,3-

sigmatropic SiMe₃migration.^6aInterestingly, azirinyl inter-

mediates related to 37 also precede the N_α−N_βbond insertion

products 10 (Figure 1)^7tand C−H activation products such as

11 reported by Bergman⁴and Gade.^8lWe therefore propose

that the products 28−32 arise by a similar mechanism, namely,

via the [2+2] cycloaddition compound 34 and then an azirinyl

intermediate analogous to 37. The ﬁrst-formed cycloaddition

species 34 is also likely to be the source of the regioselectivity

with ArCCMe.^7q,t

Scheme 5. Reactions of Ti(N₂O)(NNPh₂)(py)₂(15) with

Alkynes

As mentioned, the product formed with MeCCMe exists as a

mixture of isomers denoted “32-exo” and “32-endo” in a 5:2

ratio according to NMR integration. They have very similar ¹H

and ¹³C NMR spectra and are believed to diﬀer only with

regard to the orientation of the alkyne-derived fragment, which

may be oriented “up” toward the Ti−NPh₂moiety (as found by

crystallography for 28 and 30) or “down”, away from it. The

isomers were assigned in solution through the use of NOE

spectroscopy. It was not possible to separate the isomeric

products 32-exo and 32-endo by fractional crystallization.

Diﬀraction-quality crystals of 28 and 30 were grown from

saturated hexanes solutions at RT. The molecular structures are

shown in Figure 11, and selected bond lengths and angles are

listed in Table 3. Each possesses a distorted square base

pyramidal geometry with the new NPh₂group in the axial

tube scale in C₆D₆at 80 °C. After 2 h quantitative conversion

to free pyridine and single products for ArCCMe or PhCCPh

were observed; in the case of MeCCMe two isomeric products

were formed, the relative proportion of which did not change

over time. The reactions were scaled up in toluene at 70 °C, to

give Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(R)C(Ar)-

NSiMe₃)}(NPh₂) (R = Me, Ar = Ph (28), 4-C₆H₄OMe (29),

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Figure 11. Displacement ellipsoid plot (20% probability) of Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(Ph)NSiMe₃}(NPh₂) (28) (left) and

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(C₆H₄CF₃)NSiMe₃}(NPh₂) (30) (right). H atoms are omitted for clarity.

geometry, and the C(1)−C(2) bond distances of 1.387(3) Å

(28) and 1.3938(15) Å (30) indicate signiﬁcant double-bond

character.

Table 3. Selected Bond Lengths (Å) and Angles (deg) for

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(Ph)NSiMe₃}-

(NPh₂) (28) and

We have previously reported that reactions of Ti(NNPh₂)-

(N₂N^Me)(py) (3) with terminal alkynes form unidentiﬁed

mixtures of products.^7tIn contrast, Ti(NNPh₂)(N₂N^py)(py)

(1) reacted cleanly with both internal and terminal alkynes to

form metallacyclobutene products.^7q,tUnfortunately, although

the reactions of 15 with terminal alkynes such as TolCCH

proceeded without heating at RT in toluene over 16 h, a

complex mixture of products was formed. In the case of

TolCCH a small number of red, diﬀraction-quality crystals

identiﬁed as Ti(NPh₂){O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(H)-

C(Tol)NSiMe₃)} (33, Scheme 5) were isolated from a hexanes

solution at 0 °C. The molecular structure of 33 is given in

Figure S3 of the Supporting Information along with selected

bond lengths and angles. Interestingly the alkyne-derived

HCCTol moiety in 33 is oriented “down” away from the

Ti−NPh₂moiety in the manner proposed for 32-endo (vide

supra).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(C₆H₄CF₃)-

NSiMe₃}(NPh₂) (30)

28

30

Ti(1)−N(1)

Ti(1)−N(2)

Ti(1)−N(3)

Ti(1)−N(4)

Ti(1)−O(1)

N(1)−C(1)

C(1)−C(2)

C(1)−C(3)

1.9499(18)

2.0297(19)

1.9485(18)

1.9562(18)

2.2347(16)

1.422(3)

1.9381(9)

2.0006(10)

1.9601(10)

1.9542(10)

2.2537(9)

1.4130(14)

1.3938(15)

1.4788(15)

1.3715(15)

132.95(4)

104.48(4)

71.00(4)

1.387(3)

1.492(3)

N(3)−C(2)

1.371(3)

O(1)−Ti(1)−N(1)

O(1)−Ti(1)−N(2)

O(1)−Ti(1)−N(3)

O(1)−Ti(1)−N(4)

N(1)−Ti(1)−N(2)

N(1)−Ti(1)−N(3)

N(1)−Ti(1)−N(4)

N(2)−Ti(1)−N(3)

N(2)−Ti(1)−N(4)

N(3)−Ti(1)−N(4)

N(1)−C(1)−C(2)

N(1)−C(1)−C(3)

N(3)−C(2)−C(1)

129.54(7)

105.49(7)

70.28(7)

75.55(7)

75.23(4)

123.11(8)

83.70(7)

120.41(4)

83.95(4)

CONCLUSIONS

■

104.59(8)

105.33(8)

101.63(8)

140.87(8)

117.14(18)

118.91(18)

114.05(19)

104.76(4)

104.79(4)

103.75(4)

140.06(4)

117.76(10)

119.11(9)

113.79(10)

In this contribution we have reported the synthesis and

reactivity of two new titanium diphenyl hydrazido(2−)

complexes supported by two diﬀerent diamido-ether ligands,

N₂^ArO and N₂O. As expected from previous literature for

N₂^ArO,¹¹these ligands exhibit a larger degree of ﬂexibility with

respect to mer- or fac-coordination than is the case for the

previously employed diamido-amines (e.g., N₂N^Meand related)

in this area. This is exempliﬁed by Ti(L)(NNPh₂)(py)₂(L =

N₂^ArO (14) and N₂O (15)) or Ti(L){NC(Ar^Fx)NNPh₂}(py)₂

(22−24) with mer-bound diamido-ether ligands, but Ti(N₂O)-

(NNPh₂)(bipy) (17), Ti(N₂O){N(NPh₂)C(NAr′)S}(py)

(20), or Ti(N₂O)(NPh₂)(NCN^tBu) (26) with fac-coordinated

ones. In general, the reactions with Ar′NCE, Ar^FxCN, and RNC

follow the recently established reactivity patterns in terms of

leading to [2+2] cycloaddition to TiN_αwith Ar′NCE,

insertion into TiN_αwith Ar^FxCN, and reductive N_α−N_β

bond cleavage with isonitriles. However, there are several

diﬀerence between the reactions of 14 and 15: although both

position and Ti(1) lying 0.66−0.68 Å out of the plane formed

by N(1), N(3), N(4), and O(1). As mentioned, the MeCCAr

moiety is folded “up” toward the NPh₂ligand. Overall the

structures are reminiscent of that for Ti{O(CH₂CH₂NSiMe₃)-

(CH₂CH₂NCN(SiMe₃)Xyl)}(NPh₂)(NCNXyl) (27, Figure

10), except that in 28 and 30 O(1) is coordinated to the

metal (Ti(1)−O(1) = 2.2347(16) and 2.2537(9) Å). The Ti−

NPh₂bond distances (2.0297(19) and 2.0006(10) Å) are

consistent with formal single bonds but are a little longer than

the other three Ti−N(1,3,4) distances (range 1.9381(9)−

1.9601(10) Å). Both C(1) and C(2) have a trigonal planar

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give insertion reactions with Ar^FxCN, with RNC the N₂^ArO-

supported system forms only the σ-adduct Ti(N₂^ArO)-

(NNPh₂)(py)(CNXyl), and with alkynes no reaction took

place for 14. The reasons for these diﬀerence are not clear. The

reactions of 15 are more like those of its diamido-amine-

supported counterparts Ti(L)(NNPh₂)(py) (L = N₂N^py(1) or

N₂N^Me(3)), but with three of the four classes of substrate

studied there are clear complications arising from competing or

alternative reactions of the Ti−N_amidebond of N₂O. This is

most clearly seen in the reactions with alkynes (Scheme 5),

which give exclusively Ti−N_amidebond activation products, and

also with Ar′NCO, which forms 18, and with XylNC to give 27.

It seems that, in general, the greater ﬂexibility of the N₂O ligand

opens up these other pathways. It would be interesting in the

future to use alternative diamido-ether ligands with diﬀerent

(87%). Diﬀraction-quality crystals were grown from a concentrated

1

pentane solution at RT. H NMR (C₆D₆, 299.9 MHz): δ 3.24 (4H, t,

3

³J = 4.9 Hz, OCH₂), 3.07 (4H, t, J = 4.9 Hz, NCH₂), 0.16 (18H, s,

SiMe₃) ppm. ¹³C{¹H} NMR (C₆D₆, 75.4 MHz): δ 77.9 (NCH₂), 45.6

7

(OCH₂), 1.9 (SiMe₃) ppm. Li NMR (toluene-d₈, 117 MHz): 1.9

(NLi) ppm. IR (NaCl plates, Nujol mull, cm⁻¹): 1570 (m), 1419 (w),

1358 (w), 1345 (m), 1271 (w), 1242 (s), 1084 (s), 1052 (s), 1022 (s),

952 (s), 913 (w), 823 (s), 763 (m), 734 (s), 668 (m), 618 (m). Anal.

Found (calcd for C₁₀H₂₆N₂OSi₂Li₂): C, 46.43 (46.13); H, 10.21

(10.06); N, 10.76 (10.20).

Ti(N₂^ArO)(NNPh₂)(py)₂(14). To a mixture of Li₂N₂^ArO (0.23 g, 0.63

mmol) and Ti(NNPh₂)Cl₂(py)₃(0.32 g, 0.63 mmol) cooled to −40

°C was added cold toluene (20 mL, −40 °C). The stirred green-brown

suspension was allowed to warm to RT and stirred for a further hour,

resulting in a dark brown solution. The volatiles were removed under

reduced pressure, and the dark brown solid was extracted into toluene

(2 × 15 mL) and ﬁltered. The volatiles were removed under reduced

pressure. The residue was washed with hexanes (2 × 5 mL), and the

supernatant was removed by ﬁltration. The solid was dried in vacuo to

yield the product as a dark brown powder. Yield: 0.27 g (59%).

Diﬀraction-quality crystals were grown from a saturated hexanes

solution at 4 °C. ¹H NMR (C₆D₆, 499.9 MHz, 293 K): δ 9.12 (4H, d,

³J = 5 Hz, o-C₆H₅N), 7.23 (4H, app. d, app. ³J = 7.2 Hz, o-C₆H₅), 7.08

N_amidesubstituents to try to block these deleterious alternatives.

EXPERIMENTAL SECTION

General Methods and Instrumentation. All manipulations were

■

carried out using standard Schlenk line or drybox techniques under an

atmosphere of argon or dinitrogen. Solvents were degassed by

sparging with dinitrogen and dried by passing through a column of the

appropriate drying agent. Toluene was reﬂuxed over sodium and

distilled. Deuterated solvents were dried over potassium (C₆D₆),

sodium (toluene-d₈), or P₂O₅(CDCl₃·CD₂Cl₂), distilled under

reduced pressure, and stored under dinitrogen in Teﬂon valve

ampules. NMR samples were prepared under dinitrogen in 5 mm

Wilmad 507-PP tubes ﬁtted with J. Young Teﬂon valves. ¹H and

¹³C{¹H} NMR spectra were recorded on Varian Mercury-VX 300 and

Varian Unity Plus 500 spectrometers at ambient temperature unless

stated otherwise, referenced internally to residual protio-solvent (¹H)

or solvent (¹³C) resonances, and are reported relative to

tetramethylsilane (δ = 0 ppm). ¹⁹F spectra were referenced externally

3

(4H, app. t, app. J = 7 Hz, m-C₆H₅), 6.95 (2H, dd, J = 7 Hz, p-

C₆H₄O), 6.86−6.89 (4H, overlapping m, p-C₆H₅and o-C₆H₄O), 6.71

− 6.76 (4H, overlapping m, p-C₆H₅N and m-C₆H₄O), 6.52 (4H, m, m-

C₆H₅N), 6.20 (2H, m, o-C₆H₄N), 0.46 (18H, s, SiMe₃) ppm. ¹³C{¹H}

NMR (C₆D₆, 125.7 MHz, 293 K): 152.4 (o-C₆H₅N), 150.1 (ipso-

C₆H₄O), 147.0 (m-C₆H₅N), 145.2 (ipso-C₆H₄N), 137.4 (p-C₆H₅N),

128.6 (m-C₆H₅), 123.9 (m-C₆H₄O), 123.0 (m-C₆H₅N), 122.0 (o-

C₆H₅), 119.1 (p-C₆H₄O), 114.3(o-C₆H₄N), 112.1 (o-C₆H₄O), 2.7

(SiMe₃) ppm. IR (NaCl plates, Nujol mull, cm⁻¹): 1603 (m), 1597

(m), 1586 (w), 1576 (w), 1559 (w), 1493 (m), 1475 (s), 1444 (s),

1317 (w), 1279 (s), 1240 (s), 1212 (w), 1189 (m), 1169 (w), 1158

(w), 1111 (w), 1068 (w), 1040 (w), 1011 (w), 928 (s), 875 (w), 842

(m), 779 (w), 751 (m), 736 (m), 724 (w), 694 (s), 669 (w), 637 (w),

629 (w), 581 (w), 484 (br, m), 402 (w). Anal. Found (calcd for

C₂₂H₃₅N₃OSi₂Ti·C₅H₅N): C, 64.35 (64.50); H, 6.45 (6.34); N, 10.88

(10.75).

7

2

to CFCl₃. Li spectra were referenced externally to LiCl, and the H

NMR spectrum was referenced to the natural abundance deuterium

resonance of the protio solvent (C₆H₆). Assignments were conﬁrmed

using two-dimensional ¹H−¹H and ¹³C−¹H NMR correlation

experiments. Chemical shifts are quoted in δ (ppm) and coupling

constants in Hz. IR spectra were recorded on a Nicolet Magna 560

E.S.P. FTIR spectrometer. Samples were prepared in a drybox as Nujol

mulls between NaCl plates, and the data are quoted in wavenumbers

(cm⁻¹). Elemental analyses were carried out by the Elemental Analysis

Service at the London Metropolitan University or Elemental

Microanalysis Ltd., Devon.

Ti(N₂^ArO)(NNPh₂)(^tBu-bipy) (16). To a stirred solution of Ti-

(N₂^ArO)(NNPh₂)(py)₂(14) (0.29 g, 0.40 mmol) in toluene (20 mL)

t

was added a solution of Bu-bipy (0.11 g, 0.40 mmol) in toluene (10

mL) at RT. An immediate change of color from dark brown to dark

green was observed. After stirring for 1 h, the volatiles were removed

under reduced pressure. The residue was triturated in hexanes (2 × 10

mL), and the supernatant was removed by ﬁltration. The resulting

solid was dried in vacuo to yield the product as a dark green powder.

Yield: 0.17 g (50%). Diﬀraction-quality crystals were grown from a

Starting Materials. O(CH₂CH₂NH₂)₂,¹²Ti(NNPh₂)Cl₂(py)₃,^7p

(4-C₆H₄OMe)CCMe,³⁰(4-C₆H₄CF₃)CCMe,³⁰Ar′NCSe,^7wand

Li₂N₂^ArO¹¹were synthesized according to literature procedures.

Other reagents were purchased from Sigma-Aldrich or Alfa-Aesar

and used without further puriﬁcation.

1

saturated toluene/hexanes solution at 4 °C. H NMR (C₆D₆, 499.9

3

MHz, 293 K): δ 9.35 (2H, d, J = 6 Hz, 6-(4,4′-tert-butyl)C₅H₃N)₂),

7.48 (2H, d, ⁴J = 1.5 Hz, 3-((4,4′-tert-butyl)C₅H₃N)₂), 7.32 (2H, dd, ³J

4

3

4

= 7.3 Hz, J = 1.5 Hz, o-C₆H₄O), 7.03 (4H, dd, J = 7.0 Hz, J = 1.5

Hz, o-C₆H₅), 6.97 (2H, m, m-C₆H₄O), 6.92 (4H, m, m-C₆H₅), 6.84

(2H, dd, ³J = 6.8 Hz, ⁴J = 1.5 Hz, o-C₆H₄N), 6.82 (2H, dd, ⁴J = 1.5 Hz,

³J = 6.8 Hz, 5-(4,4′-tert-butyl)C₅H₃N)₂), 6.69 (2H, m, p-C₆H₅), 6.26

(2H, m, p-C₆H₄O), 0.85 (18H, s, (4,4′-CMe₃C₅H₃N)₂), 0.80 (18H, s,

SiMe₃) ppm. ¹³C{¹H} NMR (C₆D₆, 125.7 MHz, 293 K): 162.5 (4-

(4,4′-tert-butyl)C₅H₃N)₂), 152.7 (2-(4,4′-tert-butyl)C₅H₃N)₂), 152.2

(6-(4,4′-tert-butyl)C₅H₃N)₂), 151.3 (ipso-C₆H₄O), 150.3 (ipso-

C₆H₄N), 146.8 (ipso-C₆H₅), 128.5 (m-C₆H₅), 125.5 (m-C₆H₄O),

122.3 (5-(4,4′-tert-butyl)C₅H₃N)₂), 121.7 (p-C₆H₅), 119.9 (o-C₆H₅),

119.8 (o-C₆H₄O), 119.5 (o-C₆H₄N), 116.9 (3-(4,4′-tert-butyl)

C₅H₃N)₂), 114.9 (p-C₆H₄O), 34.6 (4,4′-CMe₃C₅H₃N)₂), 29.8 (4,4′-

CMe₃C₅H₃N)₂), 4.1 (SiMe₃) ppm. IR (NaCl plates, Nujol mull,

cm⁻¹): 1617 (w), 1594 (w), 1586 (w), 1489 (m), 1482 (m), 1403 (w),

1304 (w), 1281 (w), 1247 (m), 1151 (w), 1101 (w), 946 (w), 914

(w), 845 (m), 736 (m), 698 (w), 623 (w), 488 (br, s). EI-MS: m/z

=572 [Ti(N₂O)(NNPh₂)]⁺(5%), 269 [^tBu-bipy]⁺(14%), 73 [SiMe₃]⁺

(46%). Anal. Found (calcd for C₄₈H₆₀N₆OSi₂Ti·0.75(C₇H₈)): C, 70.18

(70.27); H, 7.26 (7.31); N, 9.00 (9.23).

H₂N₂O (12). A solution of O(CH₂CH₂NH₂)₂(8.14 g, 78.2 mmol)

and Et₃N (43.6 mL, 0.31 mol) in THF (30 mL) was cooled to 0 °C.

Me₃SiCl (21.8 mL, 0.17 mol) was added dropwise to the cooled

solution, a white precipitate immediately formed, and the reaction was

warmed to RT. After 3 h the slurry was ﬁltered and volatiles were

removed under reduced pressure. The product was extracted into

pentane (30 mL) and the solvent was removed in vacuo to give a

1

colorless oil. Yield: 14.5 g (75%). H NMR (CDCl₃, 299.9 MHz): δ

3.32 (4H, t, ³J = 5.7 Hz, OCH₂), 2.80 (4H, t, ³J = 5.7 Hz, NCH₂), 0.71

(2H, s, NH), −0.3 (18H, s, SiMe₃). ¹³C{¹H} NMR (CDCl₃, 75.4

MHz): δ 73.9 (NCH₂), 41.5 (OCH₂), 0.0 (SiMe₃). IR (NaCl plates,

Nujol mull, cm⁻¹): 2361 (s), 2336 (m), 1653 (s), 1456 (s), 1248 (s),

1115 (m), 949 (w), 836 (s), 668 (s). FI-MS: [M + H]⁺m/z =

249.1825 (calcd for C₁₀H₂₈N₂OSi₂: m/z = 249.1818).

Li₂N₂O (13). BuLi (23.5 mL, 37.7 mmol, 1.6 M in hexanes) was

added dropwise to a solution of 12 (4.45 g, 17.9 mmol) in hexanes (60

mL) at −78 °C. A white precipitate immediately formed, and the

solution was then warmed to RT. After 3 h the white solid was ﬁltered,

washed with pentane (3 × 5 mL), and dried in vacuo. Yield: 4.07 g

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Ti(N₂O)(NNPh₂)(py)₂(15). To a stirred mixture of Ti(NNPh₂)-

Cl₂(py)₃(2.07 g, 3.84 mmol) and Li₂N₂O (13) (1.00 g, 3.84 mmol),

cooled to −78 °C, was added cold toluene (60 mL, −78 °C). The

reaction was allowed to warm to RT, and the solution gradually

changed color from green to dark brown. After 1 h the volatiles were

removed in vacuo and the dark brown oily solid extracted into Et₂O (3

× 15 mL), which was then removed in vacuo. The product was

recrystallized from a concentrated hexanes solution at RT. Yield: 1.72g

(71%). Diﬀraction-quality crystals were grown from a saturated

hexanes solution at RT. ¹H NMR (C₆D₆, 299.9 MHz): δ 9.09 (4H, d,

³J = 4.8 Hz, o-py), 7.11 (4H, t, ³J = 8.6 Hz, o-NPh₂), 7.01 (2H, t, ³J =

then cooled to −78 °C. Hexanes (10 mL) were then added, and the

so-formed dark red solid was ﬁltered, washed with cold hexanes and

dried in vacuo at 0 °C. Yield: 0.30 g, (61%). ¹H NMR (CD₂Cl₂, 499.9

3

MHz, 0 °C): δ 7.84 (4H, dd, J = 6.3, 1.6 Hz, o-NPh₂), 7.75−7.59

3

(2H, m, p-NPh₂), 7.10−6.96 (5H, m, m-NPh₂, m-Ar′), 6.85 (1H, t, J

3

= 7.6 Hz, m-Ar′), 6.65 (1H, dd, J = 7.6, 1.4 Hz, p-Ar′), 4.41−4.11

(2H, m, OCH₂CH₂NSiMe₃, CH₂NC), 4.11−3.86 (2H, m,

OCH₂CH₂NC, OCH₂CH₂NSiMe₃), 3.86−3.62 (2H, m,

OCH₂CH₂NC, CH₂NSiMe₃), 3.20 (1H, dt, ³J = 6.8, 5.7 Hz,

3

CHMe₂), 3.09 (1H, dd, J = 13.4, 3.3 Hz, CH₂NSiMe₃), 2.98 (1H,

3

dt, J = 13.7, 6.8 Hz, CHMe₂), 2.91 (1H, d, J = 15.2 Hz, CH₂NC),

1.14 (3H, d, ³J = 6.8 Hz, MeC), 1.09 (3H, d, ³J = 6.9 Hz, MeC), 0.98

(3H, d, ³J = 6.9 Hz, MeC), 0.62 (3H, d, ³J = 6.9 Hz, MeC), 0.29 (9H,

s, CNSiMe₃), −0.46 (9H, s, CH₂NSiMe₃) ppm. ¹³C{¹H} NMR

(CD₂Cl₂, 125.7 MHz, 0 °C): δ 157.7 (NCO), 150.3 (o-NPh₂), 147.4

(i-Ar′), 141.3 (o-Ar′), 140.2 (o-Ar′), 138.2 (p-NPh₂), 136.0 (i-NPh₂),

124.3 (m-NPh₂), 122.9 (p-Ar′), 121.2 (m-Ar′), 120.7 (m-Ar′), 80.7

(OCH₂CH₂NSiMe₃), 77.8 (OCH₂CH₂NC), 47.6 (CH₂NSiMe₃), 42.5

(CH₂NC), 28.0 (CHMe₂), 27.4 (CHMe₂), 24.2 (MeC), 23.8 (MeC),

23.3 (MeC), 22.5 (MeC), 1.3 (NCSiMe₃), 0.3 (CH₂NSiMe₃) ppm. IR

(NaCl plates, Nujol mull, cm⁻¹): 1586 (m), 1566 (m), 1521 (w), 1491

(s), 1457 (s), 1339 (m), 1327 (m), 1247 (m), 1216 (w), 1153 (w),

1100 (w), 1069 (w), 1057 (w), 1043 (w), 1008 (w), 948 (w), 842 (s),

802 (w), 744 (m), 694 (m). EI-MS: m/z 679 (5%) [M]⁺, 496 (5%)

[M − NNPh₂]⁺, 91 (100%) [NPh]⁺. Anal. Found (calcd for

C₃₅H₅₃N₅O₂Si₂Ti): C, 61.48 (61.83); H, 7.53 (7.86); N, 10.35

(10.30).

7.6 Hz, p-py), 6.89 (2H, t, ³J = 7.1 Hz, p-NPh₂), 6.78−6.65 (8H, m, m-

NPh₂and m-py), 3.53 (4H, t, ³J = 5.4 Hz, OCH₂), 3.10 (4H, t, ³J = 5.4

Hz, NCH₂), 0.42 (18H, s, SiMe₃) ppm. ¹³C{¹H} NMR (C₆D₆, 75.4

MHz): δ 152.6 (o-py), 146.8 (i-NPh₂), 137.4 (p-py), 128.2 (p-NPh₂),

23.6 (m-py), 120.4 (m-NPh₂), 119.0 (o-NPh₂), 74.1 (NCH₂), 51.0

(OCH₂), 2.7 (SiMe₃) ppm. IR (NaCl plates, Nujol mull, cm⁻¹): 1597

(s), 1581 (s), 1559 (w), 1539 (w), 1506 (w), 1489 (s), 1442 (s), 1419

(w), 1351 (w), 1293 (m), 1276 (m), 1256 (m), 1242 (m) 1206 (m),

1183 (w), 1167 (m), 1150 (w), 1115 (m), 1068 (m), 1036 (m), 1024

(w), 1007 (w), 995 (w), 958 (s), 938 (m), 885 (w), 841 (s), 824 (s),

787 (m), 743 (s), 693 (s), 668 (m), 660 (w), 634 (s), 624 (m). EI-

MS: m/z = 168 (98%) [NPh₂]⁺, 73 (85%) [SiMe₃]⁺. Anal. Found

(calcd for C₂₇H₄₁N₅OSi₂Ti): C, 58.36 (58.36); H, 7.30 (7.44); N,

11.80 (12.60).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(O)N(SiMe₃)Ar′)}{N(NPh₂)C(O)N-

(Ar′)} (18). Ar′NCO (0.20 mL, 0.95 mmol) was added to a solution of

Ti(N₂O)(NNPh₂)(py)₂(15, 0.30 g, 0.47 mmol) in benzene (10 mL).

After 1 h the brown precipitate formed was ﬁltered, washed with

Ti(N₂O){N(NPh₂)C(NAr′)S}(py) (20). A solution of Ar′NCS (0.14 g,

0.63 mmol) in Et₂O (10 mL) was added to a solution of

Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63 mmol) in Et₂O (10 mL).

After 1 h the resulting suspension was ﬁltered and the red solid dried

in vacuo. Yield: 0.28 g (57%). Diﬀraction-quality crystals were grown

from a concentrated benzene solution, layered with hexanes. ¹H NMR

(CD₂Cl₂, 299.9 MHz): δ 8.81 (2H, d, ³J = 4.7 Hz, o-py), 7.81 (1H, dd,

³J = 10.6, 4.6 Hz, p-py), 7.49−7.35 (3H, m, o-NPh₂, m-py), 7.28−7.15

(4H, m, m-NPh₂), 7.01−6.78 (8H, m, p-Ar′, m-Ar′, p-NPh₂), 3.98

1

benzene (3 × 10 mL), and dried in vacuo. Yield: 0.19 g (46%). H

3

NMR (CD₂Cl₂, 299.9 MHz): δ 7.51 (4H, d, J = 7.5 Hz, o-NPh₂),

7.38−7.07 (7H, m, p-Ar′NCO, m-NPh₂, m-Ar′NCO), 7.03 (2H, t, ³J =

7.3 Hz, p-NPh₂), 6.93 (2H, d, ³J = 7.8 Hz, m-Ar′NSiMe₃), 6.70 (1H, t,

³J = 7.2 Hz, p-Ar′NSiMe₃), 4.22−4.06 (2H, m, OCH₂CH₂NSiMe₃),

3.69−3.33 (5H, m, CH₂NSiMe₃, OCH₂CH₂NCO, HCC₆H₃NSiMe₃),

3.29−3.01 (2H, m, HCC₆H₃NSiMe₃, HCC₆H₃NCO), 3.01−2.85 (1H,

m, HCC₆H₃NCO), 2.76 (1H, dt, ³J = 12.4, 6.1 Hz, CH₂NCO), 2.60−

3

(4H, t, J = 5.4 Hz, OCH₂), 3.76 (2H, dt, J = 12.0, 5.8 Hz, NCH₂),

3.22 (2H, dt, ³J = 13.1, 4.8 Hz, NCH₂), 3.08 (2H, dq, ³J = 13.7, 6.9 Hz,

CHMe₂), 1.18 (6H, d, ³J = 5.9 Hz, CHMe₂), 0.87 (6H, d, ³J = 5.9 Hz,

CHMe₂), −0.09 (18H, s, SiMe₃) ppm. ¹³C{¹H} NMR (CD₂Cl₂, 75.4

MHz): δ 150.6 (o-py), 147.4 (i-NPh₂), 145.0 (o-Ar′), 141.1 (i-Ar′),

128.7 (m-NPh₂), 124.4 (m-py), 122.4 (p-Ar′), 122.2 (p-NPh₂), 120.3

(m-Ar′), 119.0 (o-NPh₂), 77.7 (OCH₂), 53.6 (NCH₂), 28.1 (CHMe₂),

24.1 (CHMe₂), 23.3 (CHMe₂), 1.1 (SiMe₃) ppm. IR (NaCl plates,

Nujol mull, cm⁻¹): 1609 (s), 1578 (s), 1492 (s), 1332 (w), 1279 (w),

1246 (m), 1220 (w), 1164 (w), 1072 (w), 1053 (w), 1030 (w), 990

(w), 953 (w), 939 (m), 922 (m), 871 (m), 837 (s), 794 (m), 758 (m),

740 (s), 700 (m), 690 (m). EI-MS: m/z = 775 (2%) [M]⁺, 696 (3%)

[M − py]⁺, 169 (42%) [NPh₂]⁺. Anal. Found (calcd for

C₄₀H₅₈N₆OSSi₂Ti): C, 61.80 (61.99); H, 7.24 (7.54); N, 10.46

(10.84).

2.40 (1H, m, CH₂NCO), 1.43 (3H, d, ³J

Me₂CHC₆H₃NSiMe₃), 1.28 (3H, d, ³J

=

6.7 Hz,

5.5 Hz,

= 3.5 Hz,

Me₂CHC₆H₃NSiMe₃), 1.26 (3H, d, ³J

3

Me₂CHC₆H₃₃NSiMe₃), 1.24 (3H, d, J = 4.7 Hz, Me₂CHC₆H₃NCO),

3

1.18 (3H, d, J = 6.8 Hz, Me₂CHC₆H₃NSiMe₃), 1.13 (3H, d, J = 7.0

Hz, Me₂CHC₆H₃NCO), 1.10 (3H, d, ³J = 6.8 Hz, Me₂CHC₆H₃NCO),

0.94 (3H, d, ³J = 6.8 Hz, Me₂CHC₆H₃NCO), 0.13 (9H, s,

Ar′NSiMe₃), −0.11 (9H, s, CH₂NSiMe₃) ppm. ¹³C{¹H} NMR

(CD₂Cl₂, 75.4 MHz): δ 169.1 (CO), 166.4 (CO), 148.2 (i-

Ar′NCO), 147.6 (i-Ar′NSiMe₃), 147.2 (o-Ar′NSiMe₃), 146.5 (o-

Ar′NCO), 145.1 (o-Ar′NSiMe₃), 143.6 (o-Ar′NCO), 134.7 (i-NPh₂),

128.9 (p-Ar′NCO), 125.3 (o-NPh₂), 124.2 (m-Ar′NCO), 123.4 (m-

NPh₂), 122.8 (p-NPh₂), 118.2 (p-Ar′NSiMe₃), 114.0 (m-Ar′NSiMe₃),

74.2 (OCH₂CH₂NSiMe₃), 72.4 (OCH₂CH₂NCO), 52.0

(CH₂NSiMe₃), 45.2 (CH₂NCO), 29.2 (HCC₆H₃NCO), 29.0

(HCC₆H₃NCO), 28.3 (HCC₆H₃NSiMe₃), 28.2 (HCC₆H₃NSiMe₃),

25.8 (Me₂CHC₆H₃NCO), 25.4 (Me₂CHC₆H₃NSiMe₃), 25.2

(Me₂CHC₆H₃NCO), 24.2 (Me₂CHC₆H₃NCO), 24.0

(Me₂CHC₆H₃NSiMe₃), 23.6 (Me₂CHC₆H₃NSiMe₃), 23.2

(Me₂CHC₆H₃NSiMe₃), 22.8 (Me₂CHC₆H₃NCO), 0.3 (Ar′NSiMe₃),

−0.2 (CH₂NSiMe₃) ppm. IR (NaCl plates, Nujol mull, cm⁻¹): 1684

(m), 1658 (s), 1636 (m), 1623 (m), 1617 (m), 1587 (s), 1576 (m),

1559 (m), 1554 (w), 1539 (m), 1517 (s), 1492 (s), 1457 (s), 1420 (s),

1362 (m), 1342 (m), 1331 (s), 1292 (s), 1254 (s), 1244 (m), 1197

(m), 1173 (m), 1068 (m), 1030 (m), 1006 (m), 938 (m), 925 (m),

902 (s), 840 (s), 792 (s), 769 (m), 748 (m), 740 (s), 725 (w), 699 (s),

679 (m), 668 (w), 641 (m), 590 (s). EI-MS: m/z =701 (5%) [M −

NNPh₂]⁺, 168 (100%) [NPh₂]⁺. Anal. Found (calcd for

C₄₈H₇₀N₆O₃Si₂Ti): C, 65.22 (65.28); H, 8.00 (7.99); N, 9.40 (9.52).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂N(SiMe₃)C(NAr′)O)}(NNPh₂) (19).

Ar′NCO (0.14 mL, 0.63 mmol) was added to a solution of

Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63 mmol) in CH₂Cl₂cooled

to −78 °C. The solution was allowed to warm to 0 °C over 2 h and

Ti(N₂^ArO){NC(Ar^F5)NNPh₂}(py)₂(22). To a stirred solution of

Ti(N₂^ArO)(NNPh₂)(py)₂(14, 0.28 g, 0.38 mmol) in toluene (20

mL) was added a solution of Ar^F5CN (48.4 μL, 0.38 mmol) in toluene

(10 mL) at RT, leading to an immediate change of color from dark

brown to bright orange. After stirring for 2 h, the volatiles were

removed under reduced pressure. The residue was washed with

hexanes (2 × 10 mL), and the resulting solid was dried in vacuo to give

22 as an orange powder. Yield: 0.17 g (52%). Diﬀraction-quality

1

crystals were grown from a saturated toluene/pentane solution. H

NMR (C₆D₆, 499.9 MHz, 293 K): δ 9.02 (4H, br, s, o-NC₅H₅), 7.18

(4H, d, ³J = 7.1 Hz, o-C₆H₅), 7.04−7.07 (6H, m, overlapping m-C₆H₅

and o-OC₆H₄), 6.82 (2H, m, p-C₆H₅), 6.64−6.67 (4H, m, overlapping

m, p-NC₅H₅and m-OC₆H₄), 6.60 (2H, m, o-NC₆H₄), 6.49 (4H, m, m-

NC₅H₅), 6.35 (2H, m, p-OC₆H₄), 0.43 (18H, s, SiMe₃) ppm. ¹³C{¹H}

NMR (C₆D₆, 125.7 MHz, 293 K): 151.1 (o-NC₅H₅), 149.7 (i-C₆H₅),

149.3 (i-OC₆H₄), 144.8 (i-NC₆H₄), 138.0 (p-NC₅H₅), 128.8 (m-

C₆H₅), 124.3 (m-OC₆H₄), 123.2 (m-NC₅H₅), 122.5 (p-C₆H₅), 121.8

(o-C₆H₅), 118.3 (o-NC₆H₄), 115.6 (p-OC₆H₄), 112.1 (o-OC₆H₄), 3.1

(SiMe₃) ppm. ¹⁹F NMR NMR (C₆D₆, 282.5 MHz, 293 K): −164.1 (o-

3103

dx.doi.org/10.1021/om400311w | Organometallics 2013, 32, 3091−3107

Organometallics

Article

C₆F₅), −158.0 (m-C₆F₅), −136.1 (p-C₆F₅) ppm. Resonances

corresponding to NC(C₆F₅)NNPh₂were not observed. IR (NaCl

plates, Nujol mull, cm⁻¹): 1603 (m), 1588 (w), 1517 (m), 1502 (m),

1493 (m), 1293 (w), 1280 (m), 1247 (m), 1189 (w), 1112 (w), 1042

(w), 1013 (w), 991 (w), 951 (w), 922 (w), 871 (w), 833 (m), 786

(w), 753 (m), 736 (w), 712 (w), 697 (w), 636 (w), 487 (br, s). EI-MS:

m/z = 241 [TiNC(C₆F₅)]⁺(25%), 192 [C₆F₅CN]⁺(29%), 169

[NPh₂]⁺(100%), 167 [C₆F₅]⁺(84%). Anal. Found (calcd for

C₄₇H₄₇N₇OSi₂Ti·0.4(C₇H₈)): C, 62.07 (62.19); H, 5.31 (5.26); N,

9.74 (10.19).

volatiles were removed under reduced pressure. The resultant dark red

oil was dissolved in a minimum volume of hexanes (5 mL) and cooled

to −78 °C. The solid formed was ﬁltered and dried in vacuo and then

dissolved in a minimum amount of pentane and cooled to −30 °C.

The red powder was again ﬁltered and then dried in vacuo. Yield: 0.16

g (46%). Diﬀraction-quality crystals were grown from a concentrated

1

hexanes solution at RT. H NMR (C₆D₆, 299.9 MHz): δ 7.25−7.02

(8H, m, o-NPh₂, m-NPh₂), 6.84 (2H, m, p-NPh₂), 3.53 (2H, m,

OCH₂), 3.22 (2H, m, NCH₂), 3.13−3.01 (4H, m, OCH₂, NCH₂),

1.25 (9H, s, CMe₃), 0.31 (18H, s, SiMe₃) ppm. ¹³C{¹H} NMR (C₆D₆,

75.4 MHz): δ 153.45 (i-NPh₂), 129.1 (o-NPh₂), 123.3 (m-NPh₂),

122.7 (p-NPh₂), 118.5 (NCN), 74.1 (OCH₂), 52.9 (NCH₂), 42.8

(CMe₃), 32.0 (CMe₃), 2.1 (SiMe₃) ppm. IR (NaCl plates, Nujol mull,

cm⁻¹): 2102 (s), 1592 (m), 1247 (m), 1172 (m), 1092 (w), 1077 (m),

1028 (w), 939 (m), 922 (m), 859 (s), 841 (s), 785 (m), 755 (m), 694

(m). EI-MS: m/z = 559 (5%) [M]⁺, 391 (100%) [M − NPh₂]⁺, 168

(62%) [NPh₂]⁺, 73 (67%) [SiMe₃]⁺. Anal. Found (calcd for

C₂₇H₄₅N₅OSi₂Ti): C, 58.04 (57.94); H, 8.00 (8.10); N, 12.38 (12.51).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NCN(SiMe₃)Xyl)}(NPh₂)(NCNXyl)

(27). A solution of XylNC (0.17 g, 1.26 mmol) in toluene (10 mL)

was added to a solution of Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63

mmol) in toluene (10 mL) and heated to 70 °C. After 16 h the

volatiles were removed under reduced pressure. The solid was

dissolved in pentane (5 mL) and cooled to −78 °C, giving 27 as a red

solid, which was ﬁltered and dried in vacuo. Yield: 0.23 g (50%).

Diﬀraction-quality crystals were grown from a concentrated hexanes

solution at RT. ¹H NMR (C₆D₆, 299.9 MHz): δ 7.33 (4H, d, ³J = 8.4

Hz, o-NPh₂), 7.30−7.12 (6H, m, m-NPh₂, m-XylNCN), 7.06−6.76

(6H, m, p-NPh₂, p-XylNCN, p-XylNSiMe₃, m-XylNSiMe₃), 3.94 (1H,

m, CH₂NSiMe₃), 3.78 (1H, m, OCH₂CH₂NSiMe₃), 3.60−3.49 (2H,

m, OCH₂CH₂NC), 3.42 (1H, m, CH₂NC), 3.15 (1H, d, ³J = 10.6 Hz,

OCH₂CH₂NSiMe₃), 2.88 (1H, d, ³J = 14.9 Hz, CH₂NC), 2.77 (6H, s,

Ti(N₂O){NC(Ar^F5)NNPh₂}(py)₂(23). Ar^F5CN (0.09 mL, 0.69 mmol)

was added to a solution of Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63

mmol) in toluene and heated to 70 °C. After 2 h the volatiles were

removed under reduced pressure to give a dark red, viscous oil. This

was dissolved in a minimum volume of hexanes at 40 °C and allowed

to cool slowly to form an orange solid, which was washed with pentane

and dried in vacuo. Yield: 0.25 g (47%). Diﬀraction-quality crystals

1

were grown from a saturated hexanes solution at 0 °C. H NMR

3

(C₆D₆, 299.9 MHz): δ 8.93 (2H, d, J = 3.1, o-py), 7.24 (4H, d, J =

3

7.8, o-NPh₂), 7.08 (4H, t, J = 7.9, m-NPh₂), 6.91 (1H, t, J = 7.6 p-

py), 6.80 (2H, t, ³J = 7.3, p-NPh₂), 6.61 (2H, m, m-py), 3.36 (4H, t, ³J

3

= 5.6, OCH₂), 3.13 (4H, t, J = 5.6, NCH₂), 0.41 (18H, s, SiMe₃)

ppm. ¹³C{¹H} NMR (C₆D₆, 75.4 MHz): δ 151.4 (o-py), 149.9 (i-

NPh₂), 136.7 (p-py), 128.7 (m-NPh₂), 123.5 (m-py), 122.1 (o-NPh₂),

122.0 (p-NPh₂) 73.9 (NCH₂), 52.3 (OCH₂), 2.4 (SiMe₃) ppm.

Selected ¹³C{¹⁹F} NMR (C₆D₆, 75.4 MHz): 157.6 (i-C₆F₅), 141.5 (m-

C₆F₅), 138.9 (p-C₆F₅), 135.5 (o-C₆F₅) ppm. ¹⁹F{¹H} NMR (C₆D₆,

470.4 MHz): −136.3 (o-C₆F₅), −160.4 (p-C₆F₅), −164.6 (m-C₆F₅)

ppm. IR (NaCl plates, Nujol mull, cm⁻¹): 1599 (m), 1587 (w), 1517

(s), 1351 (s), 1289 (w), 1268 (w), 1246 (m), 1236 (m), 1217 (w),

1207 (w), 1150 (w), 1106 (w), 1069 (m), 1039 (w), 1008 (w), 986

(m), 951 (m), 931 (m), 884 (w), 830 (s), 752 (s), 711 (w), 702 (s),

692 (m) 670 (m), 624 (m). EI-MS: m/z = 377 (5%) [NC(NNPh₂)-

C₆F₅]⁺, 193 (35%) [NCC₆F₅]⁺. Anal. Found (calcd for

C₂₉H₃₆F₅N₅OSi₂Ti): C, 56.47 (56.58); H, 5.59 (5.60); N, 11.22

(11.84).

3

MeC₆H₃NCN), 2.47 (1H, d, J = 12.4 Hz, CH₂NC), 2.13 (3H, s,

MeC₆H₃NSiMe₃), 1.70 (3H, s, MeC₆H₃NSiMe₃), 0.52 (9H, s,

SiMe₃NXyl), 0.38 (9H, s, SiMe₃NCH₂) ppm. ¹³C{¹H} NMR (C₆D₆,

75.4 MHz): δ 203.9 (TiCN), 152.3 (i-XylNSiMe₃), 142.5 (i-

XylNCN), 136.1 (o-XylNSiMe₃), 134.2 (o-XylNSiMe₃), 132.0 (o-

XylNCN), 129.5 (i-NPh₂), 129.3 (o-NPh₂), 129.0 (m-XylNCN), 128.4

(m-XylNSiMe₃), 127.4 (m-XylNSiMe₃), 123.6 (m-NPh₂), 122.7 (p-

NPh₂), 121.6 (p-XylNSiMe₃), 121.1 (p-XylNCN), 118.1 (NCN), 73.8

(OCH₂CH₂NSiMe₃), 68.9 (OCH₂CH₂NC), 52.3 (CH₂NSiMe₃), 51.2

(CH₂NC), 20.0 (MeC₆H₃NCN), 19.2 (MeC₆H₃NSiMe₃), 18.9

(MeC₆H₃NSiMe₃), 2.1 (SiMe₃NXyl), 0.4 (SiMe₃NCH₂) ppm. IR

(NaCl plates, Nujol mull, cm⁻¹): 2184 (w), 2129 (s), 1591 (m), 1485

(m), 1269 (m), 1189 (w), 1174 (w), 1134 (w), 1114 (w), 1080 (m),

1061 (w), 1029 (w), 1011 (w), 988 (w), 925 (w), 910 (w), 879 (w),

844 (s), 780 (m), 756 (s), 698 (m), 503 (s). EI-MS: m/z = 740 (2%)

[M]⁺, 607 (5%) [M − XylNC]⁺, 439 (90%) [M − XylNC-NPh₂]⁺,

169 (100%) [NPh₂]⁺. Anal. Found (calcd for C₄₀H₅₄N₆OSi₂Ti): C,

65.14 (65.02); H, 7.23 (7.37); N, 11.21 (11.37).

Ti(N₂^ArO)(NNPh₂)(py)(CNXyl) (25). To a stirred solution of

Ti(N₂^ArO)(NNPh₂)(py)₂(14, 0.30 g, 0.40 mmol) in toluene (20

mL) was added a solution of XylNC (0.05 g, 0.40 mmol) in toluene

(10 mL) at RT, leading to an immediate change of color from dark

brown to yellow-brown. After stirring for 1 h, the volatiles were

removed under reduced pressure. The residue was washed with

hexanes (2 × 10 mL), and the resulting solid was dried in vacuo to give

1

25 as a brown powder. Yield: 0.20 g (62%). H NMR (C₆D₆, 499.9

MHz, 293 K): δ 9.16 (4H, br, s, o-NC₅H₅), 7.60 (4H, br, s, o-C₆H₅),

3

7.26 (4H, t, J = 7.3 Hz, m-C₆H₅), 7.14 (4H, br, s, overlapping m-

OC₆H₄and p-OC₆H₄), 7.01 (2H, t, ³J = 7.0 Hz, p-C₆H₅), 6.91 (2H, t,

³J = 6.9 Hz, o-OC₆H₄), 6.86 (1H, t, ³J = 6.9 Hz, p-NC₅H₅), 6.79 (1H,

3

t, J = 6.9 Hz, p-(2,6-C₆H₃Me₂CN)), 6.62−6.64 (4H, m, overlapping

m-(2,6-C₆H₃Me₂CN) and m-NC₅H₅), 6.41 (2H, br, t, o-NC₆H₄), 2.16

(6H, s, 2,6-C₆H₃Me₂CN), 0.60 (18H, s, SiMe₃) ppm. ¹³C{¹H} NMR

(C₆D₆, 125.7 MHz, 293 K): 151.8 (o-NC₅H₅), 150.1 (i-OC₆H₄), 146.4

(i-C₆H₅), 145.8 (i-NC₆H₄), 137.5 (p-NC₅H₅), 135.6 (o-(2,6-

C₆H₃Me₂CN)), 129.2 (p-(2,6-C₆H₃Me₂CN)), 128.7 (m-C₆H₅),

127.7 (m-(2,6-C₆H₃Me₂CN)), 125.5 (i-(2,6-C₆H₃Me₂CN)), 124.4

(o-OC₆H₄), 123.1 (m-NC₅H₅), 122.0 (p-C₆H₅), 120.1 (o-C₆H₅), 119.0

(p-OC₆H₄), 114.4 (o-NC₆H₄), 112.4 (m-OC₆H₄), 18.6 (2,6-

C₆H₃Me₂CN), 3.0 (SiMe₃) ppm. IR (NaCl plates, Nujol mull,

cm⁻¹): 2159 (m), 1595 (s), 1586 (s), 1570 (w), 1560 (w), 1506 (w),

1490 (s), 1476 (s), 1443 (s), 1317 (m), 1280 (s), 1244 (s), 1213 (s),

1185 (m), 1172 (w), 1160 (m), 1114 (m), 1069 (w), 1048 (w), 1041

(m), 1027 (w), 990 (w), 921 (s), 874 (w), 843 (s), 829 (s), 780 (m),

740 (m), 752 (s), 697 (s), 668 (w), 636 (m), 581 (m), 558 (m), 464

(br, s). EI-MS: m/z = 703 [M − py]⁺(5%), 572 [Ti(NNPh₂)(N₂O)]⁺

(5%), 390 [Ti(L)]⁺(5%), 344 [L]⁺(85%), 169 [NPh₂]⁺(82%), 131

[XylNC]⁺(75%). Anal. Found (calcd for C₄₄H₅₀N₆OSi₂Ti): C, 66.96

(67.50); H, 6.49 (6.44); N, 10.15 (10.73).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(Ph)NSiMe₃)}(NPh₂) (28).

PhCCMe (0.12 mL, 0.95 mmol) was added to a solution of

Ti(N₂O)(NNPh₂)(py)₂(15, 0.50 g, 0.79 mmol) in toluene (10 mL)

and heated to 70 °C. After 2 h the volatiles were removed under

reduced pressure, and the resultant dark brown, viscous oil was

dissolved in a minimum amount of hexanes (5 mL) at 40 °C. Upon

cooling to RT the brown crystalline powder that formed was ﬁltered

and dried in vacuo. Yield: 0.23 g (48%). Brown, diﬀraction-quality

needles were grown from a saturated hexanes solution at RT. ¹H NMR

(C₆D₆, 299.9 MHz): δ 7.65 (2H, d, ³J = 7.9, o-PhCC), 7.24 (2H, t, ³J =

3

7.6 Hz, m-PhCC), 7.06 (9H, m, J = 27.5 Hz, 17.0, 7.4, p-PhCC, o-

NPh₂, m-NPh₂), 6.80 (2H, t, ³J = 7.1 Hz, p-NPh₂), 3.90−2.78 (8H, m,

OCH₂, NCH₂), 1.51 (3H, s, MeCC), 0.27 (9H, s, CH₂NSiMe₃), 0.09

(9H, s, CNSiMe₃) ppm. ¹³C{¹H} NMR (C₆D₆, 75.4 MHz): δ 154.5 (i-

NPh₂), 140.9 (i-PhCC), 131.6 (o-PhCC), 128.7 (m-NPh₂), 127.9 (m-

PhCC), 126.5 (o-NPh₂), 124.6 (p-PhCC), 122.0 (MeCC), 121.6 (p-

NPh₂), 118.4 (PhCC), 76.1 (OCH₂CH₂NSiMe₃), 73.4

(OCH₂CH₂NC), 51.6 (CNCH₂), 51.0 (SiMe₃NCH₂), 14.8

(MeCC), 3.1 (CNSiMe₃), 1.2 (CH₂NSiMe₃) ppm. IR (NaCl plates,

Nujol mull, cm⁻¹): 1592 (m), 1581 (m), 1572 (m), 1560 (w), 1467

t

Ti(N₂O)(NPh₂)(NCN^tBu) (26). BuNC (0.71 mL, 0.63 mmol) was

added to a solution of Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63

mmol) in toluene (10 mL) and heated to 70 °C. After 72 h the

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Article

(s), 1422 (w), 1363 (s), 1323 (w), 1291 (w), 1243 (s), 1204 (w), 1193

(s), 1172 (m), 1152 (m), 1119 (w), 1107 (w), 1088 (s), 1051 (m),

1035 (m), 999 (w), 981 (m), 942 (s), 914 (m), 894 (s), 849 (s), 825

(s), 777 (m), 753 (s), 708 (m), 695 (s), 682 (w), 668 (w), 657 (w),

617 (w), 609 (m), 570 (s). EI-MS: m/z = 592 (30%) [M]⁺, 424 (70%)

[M − NPh₂]⁺, 169 (100%) [HNPh₂]⁺. Anal. Found (calcd for

C₃₁H₄₄N₄OSi₂Ti): C, 63.00 (62.81); H, 7.63 (7.48); N, 9.28 (9.45).

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Me)C(Me)NSiMe₃)}(NPh₂) (32).

MeCCMe (0.25 mL, 3.15 mmol) was added to a solution of

Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63 mmol) in toluene (10 mL)

and heated to 70 °C. After 3 h volatiles were removed under reduced

pressure. The resultant dark brown, viscous oil was dissolved in a

minimum amount of pentane (5 mL) and cooled to −78 °C. The

brown solid (32) that formed was ﬁltered and dried in vacuo. Yield:

0.26 g (78%). Anal. Found (calcd for C₂₆H₄₂N₄OSi₂Ti): C, 59.01

(58.85); H, 7.63 (7.98); N, 8.64 (8.37). IR (NaCl plates, Nujol mull,

cm⁻¹): 1596 (s), 1501 (w), 1288 (m), 1201 (m), 1175 (w), 876 (m),

753 (m), 700 (w). Compound 32 exists as a mixture of isomers

denoted “32-exo” and “32-endo” in a 5:2 ratio according to NMR

integration.

[SiMe₃]⁺. Anal. Found (calcd for C₃₆H₄₆N₄OSi₂Ti): C, 65.87 (66.03);

H, 6.93 (7.08); N, 8.58 (8.56).

X-ray Structure Determinations. X-ray data collection and

processing parameters are given in the Supporting Information.

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 an Enraf-

Nonius KappaCCD diﬀractometer. Absorption and decay corrections

were applied to the data, and equivalent reﬂections merged.³¹The

structures were solved with SIR92³²or SHELXS-97,³³and further

reﬁnements and all other crystallographic calculations were performed

using either the CRYSTALS program suite³⁴or SHELXL-97.³⁵Other

details of the structure solution and reﬁnements are given in the

Supporting Information (CIF data). 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 Center.

ASSOCIATED CONTENT

* Supporting Information

■

S

Data for 32-exo. ¹H NMR (C₆D₆, 499.9 MHz): δ 7.12−7.07 (4H,

Crystallographic data in CIF format and data collection and

processing parameters for the X-ray structure determinations;

further details of the X-ray structures of Li₂N₂O (13),

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(O)N(SiMe₃)Ar′)}{N-

(NPh₂)C(O)N(Ar′)} (18), and Ti{O(CH₂CH₂NSiMe₃)-

(CH₂CH₂NC(H)C(Tol)NSiMe₃)}(NPh₂) (33) and a listing

of selected bond distances for all three moleucles of 15 in the

asymmetric unit; additional experimental information (exper-

imental details for 17, 21, 24, 29, 30, 33). This information is

available free of charge via the Internet at http://pubs.acs.org.

3

m, i-NPh₂), 6.97 (2H, dd, J = 8.3, 0.9 Hz, p-NPh₂), 6.83−6.78 (4H,

3

m, o-NPh₂), 3.95 (1H, ddd, J = 13.3, 11.2, 3.5 Hz, CH₂NC), 3.76

3

(1H, td, J = 10.8, 3.7 Hz, OCH₂CH₂NSiMe₃), 3.40−3.29 (2H, m,

OCH₂CH₂NC), 3.18 (1H, ddd, ³J = 10.3, 3.4, 1.7 Hz,

OCH₂CH₂NSiMe₃), 2.87−2.77 (3H, m, CH₂NSiMe₃, CH₂NSiMe3),

2.24 (3H, s, MeCNSiMe₃), 2.06 (3H, s, MeCNCH₂), 0.01 (9H, s,

CH₂NSiMe₃), −0.10 (9H, s, MeCNSiMe₃) ppm. ¹³C{¹H} NMR

(C₆D₆, 125.7 MHz): δ 143.6 (i-NPh₂), 137.6 (CCNCH₂), 129.5 (o-

NPh₂), 123.4 (CCNSiMe₃), 121.3 (p-NPh₂), 121.1 (m-NPh₂), 76.1

(OCH₂CH₂NSiMe₃), 74.4 (OCH₂CH₂NC), 51.1 (CH₂NC), 41.9

(CH₂NSiMe₃), 23.3 (MeCNSiMe₃), 21.5 (MeCNCH₂), 1.2

(CH₂NSiMe₃), 1.1 (MeCNSiMe₃) ppm.

AUTHOR INFORMATION

Corresponding Author

*E-mail: philip.mountford@chem.ox.ac.uk.

■

1

Data for 32-endo. H NMR (C₆D₆, 499.9 MHz): δ 7.19−7.16

(4H, m, o-NPh₂), 6.99−6.94 (2H, m, p-NPh₂), 6.88−6.83 (4H, m, m-

NPh₂), 3.70−3.60 (1H, m, OCH₂CH₂NSiMe₃), 3.61−3.47 (2H, m,

CH₂NC, OCH₂CH₂NC), 3.40−3.28 (2H, m, CH₂NSiMe₃), 3.11−

2.97 (2H, m, OCH₂CH₂NSiMe₃, CH₂NC), 2.97−2.88 (1H, m,

OCH₂CH₂NC), 2.01 (3H, s, MeCNSiMe₃), 1.54 (3H, s, MeCNCH₂),

0.29 (9H, s, CH₂NSiMe₃), 0.22 (9H, s, MeCNSiMe₃) ppm. ¹³C{¹H}

NMR (C₆D₆, 125.7 MHz): δ 153.7 (i-NPh₂), 128.8 (o-NPh₂), 123.8

(p-NPh₂), 118.7 (CCNCH₂), 118.1 (m-NPh₂), 110.7 (CCNSiMe₃),

75.0 (OCH₂CH₂NSiMe₃), 72.1 (OCH₂CH₂NC), 51.7 (CH₂NC),

50.1 (CH₂NSiMe₃), 19.9 (MeCNSiMe₃), 13.6 (MeCNCH₂), 2.7

(CH₂NSiMe₃), 1.6 (MeCNSiMe₃) ppm.

Notes

The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

We thank the Royal Thai Government for a scholarship to J.U.

and Wolfson College, Oxford, for a Junior Research Fellowship

to A.D.S. We thank Dr. A. L. Thompson for advice with regard

to the crystallography.

Ti{O(CH₂CH₂NSiMe₃)(CH₂CH₂NC(Ph)C(Ph)NSiMe₃)}(NPh₂) (31). A

solution of PhCCPh (0.11 g, 0.63 mmol) in toluene (10 mL) was

added to a solution of Ti(N₂O)(NNPh₂)(py)₂(15, 0.40 g, 0.63

mmol) in toluene (10 mL) and heated to 70 °C. After 1.5 h the

volatiles were removed under reduced pressure. The resultant dark

brown oil was dissolved in a minimum amount of hexanes (5 mL) and

then cooled to −30 °C. The brown solid (31) that formed was ﬁltered

and dried in vacuo. Yield: 0.19 g (45%). ¹H NMR (C₆D₆, 499.9 MHz):

δ 7.55−7.46 (4H, m, o-CPh), 7.21 (4H, t, ³J = 7.8 Hz, o-NPh₂), 7.18−

7.12 (2H, m, p-NPh₂), 7.04−6.93 (4H, m, m-CPh), 6.93−6.78 (6H, m,

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Synthesis and reactivity of titanium hydrazido complexes supported by diamido-ether ligands

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