New group 4 organometallic and imido compounds of diamide-diamine and related dianionic O2N2-donor ligands

5586

Organometallics 2005, 24, 5586-5603

New Group 4 Organometallic and Imido Compounds of

Diamide-Diamine and Related Dianionic

O₂N₂-Donor Ligands

Michael E. G. Skinner, Thierry Toupance, David A. Cowhig, Ben R. Tyrrell, and

Philip Mountford*

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

Received July 27, 2005

New group 4 compounds supported by the tetradentate diamide-diamine ligand N₂NN′

are reported (N₂NN′ ) (2-C₅H₄N)CH₂N(CH₂CH₂NSiMe₃)₂) along with some comparative

studies with the new bis(alkoxide)-diamine ligand O₂NN′ (O₂NN′ ) (2-C₅H₄N)CH₂N(CH₂-

CMe₂O)₂). Reaction of the previously described ZrCl₂(N₂NN′) (1) with 2 equiv of MeLi or

PhCH₂MgCl gave ZrR₂(N₂NN′) (R ) Me (2) or CH₂Ph (3)). Reaction of 1 with 1 equiv of

RCH₂MgCl gave the monoalkyl analogues ZrCl(R)(N₂NN′) (R ) CH₂Ph (6) or CH₂SiMe₃(7)).

Reaction of Zr(CH₂R)₄(R ) SiMe₃or CMe₃) with H₂N₂NN′ in C₆D₆gave the corresponding

Zr(CH₂R)₂(N₂NN′), but these decomposed over several hours. Reaction of 1 with allylmag-

nesium chloride gave ZrCl{(2-NC₅(6-C₃H₅)H₄)CH₂N(CH₂CH₂NSiMe₃)₂}, in which the pyridyl

group has undergone nucleophilic attack. Reaction of 2 with BAr^F₃(Ar^F) C₆F₅) in benzene

led to the cyclometalated cation [Zr{(2-NC₅H₄)CH₂N(CH₂CH₂NSiMe₃)(CH₂CH₂NSiMe₂CH₂-

)}]⁺via SiMe₃group C-H activation, but in the presence of THF the methyl cation [ZrMe-

(THF)(N₂NN′)]⁺was formed. Reaction of 6 with BAr^Fgave the chloride cation [ZrCl(N₂-

3

NN′)]⁺. Reaction of Li₂N₂NN′ with Ti(NR)Cl₂(py)₃gave the five-coordinate imides Ti(NR)(N₂NN′)

t

i

(R ) Bu or Ar (15), Ar ) 2,6-C₆H₃Pr₂). Zirconium imides Zr(NAr)(N₂NN′) and Zr(N^tBu)-

(py)(N₂NN′) (18) were prepared by sequential reaction of 1 with LiCH₂SiMe₃(2 equiv) and

the appropriate amine and pyridine for the latter. Reaction of 1 with LiNH^tBu (2 equiv)

gave Zr(NH^tBu)₂(N₂NN′). Reaction of 18 with piperidine gave Zr(NH^tBu)(NC₅H₁₀)(N₂NN′)

(19) via N-H bond activation. For comparative purposes the group 5 imides M(N^tBu)Cl-

(N₂NN′) (M ) Nb (20) or Ta (21)) were prepared from Li₂N₂NN′ and the corresponding M(N^t-

Bu)Cl₃(py)₂. Reaction of 2-aminomethylpyridine with an excess of isobutylene oxide afforded

H₂O₂NN′ (22). Reaction of H₂O₂NN′ (1 or 2 equiv) with Ti(NMe₂)₄gave Ti(O₂NN′)₂, which

reacted with TiCl₄(THF)₂to form TiCl₂(O₂NN′). Reaction of H₂O₂NN′ with Zr(CH₂SiMe₃)₂-

Cl₂(Et₂O)₂, Zr(NMe₂)₄, or Zr(CH₂SiMe₃)₄gave ZrX₂(O₂NN′) (X ) Cl, NMe₂, or CH₂SiMe₃(27)).

Reaction of 27 with BAr^Fin the presence of THF formed [Zr(CH₂SiMe₃)(THF)(O₂NN′)]⁺,

3

but in the absence of a Lewis base the µ-alkoxide-bridged dimer [Zr₂(CH₂SiMe₃)₂(O₂NN′)₂]²⁺

was formed. The compounds 3, 6, 15, 19, 21, 22, and 27 were crystallographically

characterized.

Introduction

manipulation of ligand topology (macrocylic or podand/

open-chain), chirality, and coordination number, as well

as the “tunability” of the associated steric factors. Many

of the developments in the area have been in the context

of Ziegler-Natta olefin polymerization^2,6,7and the sto-

ichiometric and catalytic activation and transformation

of small organic molecules.^1a,b,f,j,lDiamide ligands, in

particular those incorporating one or two additional

Lewis base donors (e.g., N, O, or P), have been widely

studied in all of these contexts.^{1a,b,f,g,h,2,3}

The development of polydentate ligand frameworks

containing anionic nitrogen or oxygen donors has ac-

companied many of the advances in early transition

metal organometallic and related chemistry over the

past ca. 15 years.^1-9The success of these supporting

ligands can be attributed to the hard nature of the N

and O donor atoms, the diversity and relative ease of

* To whom correspondence should be addressed. E-mail:

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

With the aim of developing the chemistry of diamide-

donor ligand chemistry, we recently reported the syn-

thesis of the diamide-diamine protio ligands (2-C₅-

H₄N)CH₂N(CH₂CH₂N(H)R)₂(R ) SiMe₃(H₂N₂NN′),

(1) Some reviews of polydentate amide and other anionic N-donor

ligand chemistry: (a) Odom, A. L. Dalton Trans. 2005, 225. (b) Fryzuk,

M. D. Chem. Rec. 2003, 3, 2. (c) Schmidt, J. A. R.; Giesbrecht, G. R.;

Cui, C.; Arnold, J. Chem. Commun. 2003, 1025. (d) Kempe, R. Eur. J.

Inorg. Chem. 2003, 791. (e) Bourget-Merle, L.; Lappert, M. F.; Severn,

J. R. Chem. Rev. 2002, 102, 3031. (f) Gade, L. H.; Mountford, P. Coord.

Chem. Rev. 2001, 216-217, 65. (g) Gade, L. H. Chem. Commun. 2000,

173. (h) Kempe, R. Angew. Chem., Int. Ed. 2000, 39, 468. (i) Mountford,

P. Chem. Soc. Rev. 1998, 27, 105. (j) Cummins, C. C. Prog. Inorg. Chem.

1998, 47, 685. (k) McKnight, A. L.; Waymouth, R. M. Chem. Rev. 1998,

98, 2587. (l) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9. (m) Brand, H.;

Arnold, J. Coord. Chem. Rev. 1995, 140, 137. (n) Edelmann, F. T.

Coord. Chem. Rev. 1994, 137, 403. (o) Chisholm, M. C. Acc. Chem. Res.

1990, 23, 419.

t

SiMe₂Bu, or mesityl) and their corresponding lithiated

derivatives.^10a-cThese are precursors to new zirconium

(2) Reviews of olefin polymerization catalysis: (a) Gromada, J.;

Carpentier, J.-F.; Mortreaux, A. Coord. Chem. Rev. 2004, 248, 397.

(b) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283. (c)

Coates, G. W. J. Chem. Soc., Dalton Trans. 2002, 467. (d) Hou, Z.;

Wakatsuki, Y. Coord. Chem. Rev. 2002, 231, 1. (e) Bolton, P. D.;

Mountford, P. Adv. Synth. Catal. 2005, 347, 355.

Publication on Web 10/11/2005

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5587

Chart 1

and hafnium coordination compounds such as ZrCl₂(N₂-

NN′) (1, Chart 1),^10bas well as to a range of organome-

tallic and coordination complexes of the group 3^10d(e.g.,

Sc(CH₂SiMe₃)(N₂NN′), Chart 1) and lanthanide^10cmet-

als. However, apart from the simple dichloride and bis-

(dimethylamide) coordination compounds MX₂(N₂NN′)

(M ) Zr or Hf; X ) Cl or NMe₂), no other group 4

chemistry of N₂NN′ has been described. Therefore we

report here new group 4 organometallic and related

compounds containing N₂NN′, together with comple-

mentary comparative studies with a bis(alkoxide) ana-

logue. In one instance studies have extended to some

isoelectronic group 5 imido systems. Part of this work

has been communicated.^10a

(Chart 1) and its lithiated derivative Li₂N₂NN′ were

prepared according to methods previously described.^10b

Although six-coordinate zirconium and hafnium com-

pounds MX₂(N₂NN′) (X ) Cl or NMe₂) could be

prepared,^10bthe titanium congeners could not, and only

complex mixtures of products were obtained. In explor-

ing the group 4 organometallic chemistry of N₂NN′ we

therefore focused on zirconium, starting either from the

protio ligand H₂N₂NN′ or the readily prepared dichlo-

ride ZrCl₂(N₂NN′) (1).

Scheme 1 summarizes the reactions of 1 with MeLi

and Grignard reagents. Reaction with MeLi (2 equiv)

in benzene afforded the dimethyl compound ZrMe₂(N₂-

NN′) (2) as a white solid in 88% isolated yield. It was

necessary to add the lithiating reagent in two stages,

otherwise a mixture of products (containing 2 as a minor

component) was obtained. PhCH₂MgCl (2 equiv) could

be added in one portion, and after stirring at room

temperature for 18 h, Zr(CH₂Ph)₂(N₂NN′) (3) was

obtained as a yellow solid in 62% yield. The NMR data

Results and Discussion

Neutral and Cationic Group 4 Organometallic

Complexes of N₂NN′. The protio ligand H₂N₂NN′

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Commun. 2005, 3150. (b) Furuyama, R.; Saito, J.; Ishii, S.; Mitani,

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5588 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

Scheme 1. Synthesis of Zirconium Alkyl, Dialkyl,

and Allyl Complexes of N₂NN′

Figure 1. Displacement ellipsoid plot (25% probability)

of Zr(CH₂Ph)₂(N₂NN′) (3). H atoms omitted for clarity.

ride in 6 (i.e., cis to the pyridyl nitrogen, as confirmed

by X-ray crystallography for 6; see below).

Surprisingly, reaction of 1 with allyl Grignard gave

exclusive attack at the N₂NN′ pyridyl group 6 position,

forming ZrCl{(2-NC₅(6-C₃H₅)H₄)CH₂N(CH₂CH₂NSiMe₃)₂}

(9) as a yellow oil in 74% yield. Addition of a further

equivalent of Grignard in an attempt to substitute the

chloride ligand did not lead to an isolable product.

Metalation of pyridines in the 6-position has been

reported previously,¹¹but it is not clear why the pyridyl

group of 1 should be attacked only in the case of allyl

reagent and not with the other alkylating reagents used.

We have recently reported the successful use of C₃H₅-

MgCl in chloride substitution in a complex supported

by a related diamide-pyridine ligand.¹²The modified N₄

donor ligand in 9 is now a triamide-amine rather than

diamide-diamine.

The molecular structures of Zr(CH₂Ph)₂(N₂NN′) (3)

and ZrCl(CH₂Ph)(N₂NN′) (6) are shown in Figures 1 and

2, respectively. Selected bond distances and angles are

listed in Tables 1 and 2. The overall geometries (dis-

torted octahedral because of the constraining nature of

N₂NN′) of 3 and 6 are similar to the coordination

complexes ZrX₂(N₂NN′) (X ) Cl (1) and NMe₂), which

have been structurally characterized previously.^10bThe

Zr-N_N2NN′distances in 3 are intermediate between

those in ZrCl₂(N₂NN′) and Zr(NMe₂)₂(N₂NN′), with the

capping nitrogen (N(4)) showing the smallest variation

in Zr-N distance, presumably because it is the most

constrained by the ligand framework. The Zr-N_N2NN′

distances in 6 are all slightly shorter than the corre-

sponding ones in 3, as would be expected. Surprisingly

the Zr-Cl distance in 6 (2.458(2) Å) is shorter than the

corresponding bond length in 1 (2.4760(4) Å) despite the

presence of the good σ-donor benzyl group in the former.

for 2 and 3 are consistent with the C_ssymmetrical

products illustrated in Scheme 1, and 3 has been

structurally characterized (see below). Reaction of Zr-

(CH₂SiMe₃)₄or Zr(CH₂CMe₃)₄with H₂N₂NN′ in C₆D₆

gave quantitative conversion to Zr(CH₂R)₂(N₂NN′) (R

) SiMe₃(4) or CMe₃(5)) and the expected side-products

SiMe₄or CMe₄. The same organometallic products could

also be obtained on an NMR tube scale from 1 and

LiCH₂R (2 equiv). However, regardless of the method

of preparation, both complexes were unstable in solution

at room temperature, decomposing completely over 6 h

to a mixture of products (including free SiMe₄or CMe₄).

No attempt was made to isolate either compound on a

preparative scale. It is possible that excessive steric

crowding promotes alkane elimination and decomposi-

tion. It is not known whether the decomposition occurs

through attack at one of the SiMe₃C-H bonds (σ-bond

metathesis) or via R-C-H abstraction to form transient

and reactive alkylidenes.

The monoalkyl derivatives ZrCl(R)(N₂NN′) (R ) CH₂-

Ph (6) or CH₂SiMe₃(7)) were obtained in 87-97% yield

by reaction of 1 with 1 equiv of alkylating agent.

Compound 7 appears to be indefinitely stable at room

temperature, unlike the bis(trimethylsilylmethyl) ana-

logue 4. Reaction of ZrCl(CH₂Ph)(N₂NN′) (6) with

MeMgBr in benzene gave the mixed-alkyl product ZrMe-

(CH₂Ph)(N₂NN′) (8) in very good yield. An NOE (nuclear

Overhauser effect) experiment showed that the methyl

ligand lies in the position previously occupied by chlo-

(11) Armstrong, D. R.; Mulvey, R. E.; Barr, D.; Snaith, R.; Reed, D.

J. Organomet. Chem. 1988, 350, 191. Giam, C. S.; Stout, J. L. J. Chem.

Soc., Chem. Commun. 1969, 142. Gros, P.; Fort, Y.; Caubere, P. J.

Chem. Soc., Perkin Trans. 1997, 3071. Nakamura, N.; Yoshino, A.;

Takahashi, K. Bull. Chem. Soc. Jpn. 1994, 67, 26. Zhang, L.-H.; Tan,

Z. L. Tetrahedron Lett. 2000, 41, 3025.

(12) Ward, B. D.; Orde, G.; Clot, E.; Cowley, A. R.; Gade, L. H.;

Mountford, P. Organometallics 2004, 23, 4444.

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5589

Scheme 2. Synthesis of Cationic Zirconium

Complexes of N₂NN′ (anions omitted for clarity)

Figure 2. Displacement ellipsoid plot (25% probability)

of ZrCl(CH₂Ph)(N₂NN′) (6). H atoms omitted for clarity.

Table 1. Selected Bond Lengths (Å) and Angles

(deg) for Zr(CH₂Ph)₂(N₂NN′) (3)

Zr(1)-N(1)

Zr(1)-N(2)

Zr(1)-N(3)

2.111(2)

2.112(2)

2.479(2)

Zr(1)-N(4)

Zr(1)-C(17)

Zr(1)-C(24)

2.442(2)

2.342(3)

2.344(2)

N(1)-Zr(1)-N(2)

N(1)-Zr(1)-N(3)

N(2)-Zr(1)-N(3)

N(1)-Zr(1)-N(4)

N(2)-Zr(1)-N(4)

N(3)-Zr(1)-N(4)

N(1)-Zr(1)-C(17)

N(2)-Zr(1)-C(17)

Zr(1)-C(24)-C(25)

137.29(9)

99.82(8)

87.56(8)

71.84(8)

72.44(8)

67.77(7)

93.58(9)

89.62(9)

130.2(2)

N(3)-Zr(1)-C(17)

N(4)-Zr(1)-C(17)

N(1)-Zr(1)-C(24)

N(2)-Zr(1)-C(24)

N(3)-Zr(1)-C(24)

N(4)-Zr(1)-C(24)

C(17)-Zr(1)-C(24)

Zr(1)-C(17)-C(18)

163.04(9)

126.99(9)

99.54(9)

123.16(8)

80.51(8)

144.51(8)

87.09(9)

104.4(2)

Table 2. Selected Bond Lengths (Å) and Angles

Group 4 complexes of polydentate amide ligands are

important in the polymerization of olefins.^{2b,3a,f,h,l,n,y,z}Re-

grettably, attempts to polymerize ethylene (5 bar pres-

sure, toluene solvent) using ZrX₂(N₂NN′) (X ) Cl (1) or

(deg) for ZrCl(CH₂Ph)(N₂NN′) (6)

Zr(1)-Cl(1)

Zr(1)-N(1)

Zr(1)-N(2)

2.458(2)

2.104(5)

2.096(5)

Zr(1)-N(3)

Zr(1)-N(4)

Zr(1)-C(17)

2.465(6)

2.376(5)

2.319(6)

Me (2)) with methyl aluminoxane or (for 2) BAr^F(Ar^F

3

Cl(1)-Zr(1)-N(1)

Cl(1)-Zr(1)-N(2)

N(1)-Zr(1)-N(2)

Cl(1)-Zr(1)-N(3)

N(1)-Zr(1)-N(3)

N(2)-Zr(1)-N(3)

Cl(1)-Zr(1)-N(4)

N(1)-Zr(1)-N(4)

116.5(2)

102.1(1)

140.9(2)

79.0(2)

82.8(3)

99.5(3)

146.3(2)

72.7(2)

N(2)-Zr(1)-N(4)

N(3)-Zr(1)-N(4)

Cl(1)-Zr(1)-C(17)

N(1)-Zr(1)-C(17)

N(2)-Zr(1)-C(17)

N(3)-Zr(1)-C(17)

N(4)-Zr(1)-C(17)

Zr(1)-C(17)-C(18)

71.7(2)

69.9(3)

90.6(2)

92.1(3)

93.5(2)

164.7(3)

122.4(2)

104.5(4)

) C₆F₅) or [CPh₃][BAr^F₄] yielded no activity. Cation-

ic alkyl cations are accepted as being the active spe-

cies in group 4 olefin polymerization catalysts,^2b,14and

so we were interested to see if the N₂NN′ ligand could

be used for the stoichiometric generation of such species,

despite the lack of catalytic activity. Scheme 2 shows

the reactions of 2 or ZrCl(CH₂Ph)(N₂NN′) (6) with

BAr^F₃. Analogous NMR tube scale experiments were

carried out using [CPh₃][BAr^F₄] and yielded the same

cations.

The Zr-CH₂-C_ipsoangles for the benzyl ligands in 3

are substantially different. The angle subtended at C-

(17) (trans to pyridyl N) is very acute (104.4(2)°) in com-

parison to that subtended at C(24) (130.2(2)°). The cor-

responding angle at C(17) in 6 is 104.5(4)°, confirming

that this is not simply a consequence of intermolecular

packing forces, for example. The additional Zr‚‚‚C_ipso

interactions in these two compounds presumably help

reduce the electron deficiency at the formally 12 valence

electron Zr centers (ignoring any likely N(2pπ) f Zr-

(4dπ) donation from the trigonal planar sp²-hybridized

N_amideatoms). Such M‚‚‚C_ipsointeractions are well-

known in early transition metal chemistry.¹³It appears

that steric factors favor the formation of the Zr‚‚‚C_ipso

interaction approximately trans to pyridyl nitrogen as

opposed to the analogous position approximately trans

to the apical nitrogen N(4) since the amide SiMe₃

substituents are slightly oriented “up” toward this site.

Reaction of 2 in benzene with BAr^Fgave [Zr{(2-

3

NC₅H₄)CH₂N(CH₂CH₂NSiMe₃)(CH₂CH₂NSiMe₂CH₂-

)}][MeBAr^F] (10-MeBAr^F) as a white solid in 60% yield.

3

The cation 10⁺was unambiguously identified by NMR

spectroscopy (see the Experimental Section) as the C-H

bond activation product illustrated in Scheme 2 in which

one of the SiMe₃groups of N₂NN′ has been metalated.

This presumably occurs via a σ-bond metathesis reac-

tion with the Zr-Me group of the transient [ZrMe(N₂-

NN′)]⁺cation 11⁺(Scheme 2), which is isoelectronic with

the structurally characterized scandium alkyl Sc(CH₂-

SiMe₃)(N₂NN′) (Chart 1) reported by us previously.^10d

Evidence for the postulated intermediate five-coordinate

cation 11⁺was obtained by reacting 2 with BAr^F₃in the

presence of an excess of THF, which afforded [ZrMe-

(13) Elschenbroich, C.; Salzer, A. Organometallics: a concise intro-

duction, 2nd ed.; VCH: Weinheim, 1992.

(14) Bochmann, M. J. Organomet. Chem. 2004, 689, 3982.

5590 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

Chart 2

Scheme 3. Synthesis of Group 4 imido and

Bis(amide) Complexes of N₂NN′

(THF)(N₂NN′)][MeBAr^F] (12-MeBAr^F) in quantitative

3

yield (Scheme 2). Cation 12⁺is stable for days at room

temperature in CD₂Cl₂solution.

When the reaction between 2 and BAr^F₃was followed

by NMR (C₆D₆), an additional singlet was observed at

ca. 0.8 ppm, which is assigned to CH₄, the expected side-

product of σ-bond metathesis. The cyclometalated cation

10⁺is also formed in the reaction of Zr(CH₂Ph)₂(N₂NN′)

with BAr^F₃(NMR tube scale reaction) along with 1 equiv

of toluene and the anion [PhCH₂BAr^F₃]^-. This reaction

presumably occurs via a transient mono(benzyl) cation

[Zr(CH₂Ph)(N₂NN′)]⁺. The [RBAr^F]^-(R ) Me or PhCH₂)

3

anions appear to be noncoordinating according to the

¹H and ¹⁹F NMR spectra.^3y,15The intramolecular C-H

bond activation leading to 10⁺is well precedented in

the chemistry of polydentate silylamido ligands, includ-

ing cationic alkyl zirconium derivatives.^3y,16Such reac-

tions have previously been identified as catalyst deac-

tivation pathways,¹⁷although stable zirconium alkyl

cations can be formed with silylated polyamide ligands

by careful choice of ligand backbone.^3aThe ready forma-

tion of the four-membered zirconocyclic ring in 10⁺

accounts for the lack of catalytic activity of 2. Exposure

of CD₂Cl₂solutions of 10⁺to ethylene (1 atm) gave only

a slow consumption (several days) of the cation and the

formation a small quantity of white precipitate (pre-

sumably polyethylene). Attempted scale-up of this reac-

tion, however, afforded no isolable polymer.

form chloride-bridged dimers. The N₂NN′-supported

dimers I possess no plane of symmetry, and the N₂NN′

SiMe₃groups occupy chemically inequivalent sites. The

NMR spectrum of 13-PhCH₂BAr^Fin CD₂Cl₂at 20 °C

3

indicated C_ssymmetry for the N₂NN′ cation resonances

(e.g., equivalent SiMe₃groups). This is consistent with

the monomeric structure illustrated for 13⁺in Scheme

2 or a dimeric, dicationic compound with C_ssymmetry.

Cooling a sample of 13-PhCH₂BAr^Fin CD₂Cl₂to -90

A chloride analogue of 11⁺was prepared by the

reaction of ZrCl(CH₂Ph)(N₂NN′) (6) with BAr^F₃, which

gave [ZrCl(N₂NN′)][PhCH₂BAr^F₃] (13-PhCH₂BAr^F₃) as

3

°C led to broadening of the ¹H NMR (500 MHz) N₂NN′

resonances, while those for the anion remained sharp.

Unfortunately a well-defined low-temperature limiting

spectrum could not be obtained. It is therefore possible

that 13⁺may be dimeric in solution, at least at low

temperature, but even at -90 °C is rather fluxional.

This lability is attributable to repulsive effects of the

positively charged Zr centers.

1

a white solid. The H and ¹⁹F NMR spectra are consis-

-

tent with a noncoordinating [PhCH₂BAr^F

]

3

anion. It

was not possible to obtain diffraction-quality crystals

of 13-PhCH₂BAr^F₃. We recently^10c,18found than the

isoelectronic yttrium and samarium complexes M₂(µ-

Cl)₂(N₂NN′)₂exist as chloride-bridged dimers in the

solid state with the structures illustrated in Chart 2.

Likewise, the related diamide-amine compounds Zr₂Cl₂-

(µ-Cl)₂{RN(CH₂CH₂SiMe₃)₂}₂(II, R ) SiMe₃^3xor Me^3a)

Imido Complexes of N₂NN′. There is a rich and

diverse chemistry associated with early transition metal

imido compounds supported by the tridentate diamide-

amine ligands Me₃SiN(CH₂CH₂SiMe₃)₂and (2-C₅H₄N)-

C(Me)(CH₂NSiMe₃)₂

Scheme 3 summarizes the synthesis of titanium and

zirconium terminal imido and related compounds using

N₂NN′.

(15) Lee, C. H.; La, Y.-H.; Park, J. W. Organometallics 2000, 19,

344. Pflug, J.; Bertuleit, A.; Kehr, G.; Fro¨hlich, R.; Erker, G. Organo-

metallics 1999, 18, 3818. Pindado, G. J.; Thornton-Pett, M.; Hurst-

house, M. B.; Coles, S. J.; Bochmann, M. J. Chem. Soc., Dalton Trans.

1999, 1663.

(16) Morton, C.; Munslow, I. J.; Sanders, C. J.; Alcock, N. W.; Scott,

P. Organometallics 1999, 18, 4608. Boaretto, R.; Roussel, P.; Alcock,

N. W.; Kingsley, A. J.; Munslow, I. J.; Sanders, C. J.; Scott, P. J.

Organomet. Chem. 1999, 591, 174.

(17) Schrock, R. R.; Liang, L.-C.; Baumann, R.; Davis, W. M. J.

Organomet. Chem. 1999, 591, 163.

(18) Hillier, A. C.; Bonnet, F.; Dubberley, S. R.; Cowley, A. R.;

Mountford, P. Manuscript in preparation.

and their analogues.^1a

1f,3b,d,12,19

(19) (a) Pugh, S. M.; Tro¨sch, D. J. M.; Skinner, M. E. G.; Gade, L.

H.; Mountford, P. Organometallics 2001, 20, 3531. (b) Pugh, S. M.;

Blake, A. J.; Gade, L. H.; Mountford, P. Inorg. Chem. 2001, 40, 3992.

(c) Pugh, S. M.; Clark, H. S. C.; Love, J. B.; Blake, A. J.; Cloke, F. G.

N.; Mountford, P. Inorg. Chem. 2000, 39, 2001.

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5591

NAr bonds in the Cambridge Structural Database²²is

1.697(7)-1.756(5) Å (av 1.727 Å for 20 examples). The

long TidNAr bond in 15 is attributed to steric repulsions

between the Ar and SiMe₃groups.

Titanium and zirconium imido complexes M(NR)(py)-

19c

(N₂N′) (N₂N′ ) Me₃SiN(CH₂CH₂SiMe₃)₂

or (2-C₅-

H₄N)C(Me)(CH₂NSiMe₃)₂²³) related to 15 have been

structurally characterized previously. In these trigonal

bipyramidal complexes the imido and amido ligands all

occupy the equatorial coordination sites while the

neutral donors lie in the axial positions. An analogous

geometry was found for the tantalum tert-butyl imido

complex Ta(N^tBu)Me{(2-C₅H₄N)C(Me)(CH₂NSiMe₃)₂}.

However, the isoelectronic phenyl imido cation [W(N-

Ph)Me{(2-C₅H₄N)C(Me)(CH₂NSiMe₃)₂}]⁺had a trigonal

pyramidal geometry with equatorial amido groups but

an axial imido ligand.¹²DFT calculations on model

complexes M(NR)(X){HC(2-C₅H₄N)(CH₂SiH₃)₂} showed

an unambiguous electronic preference for the imido

ligand to occupy the axial sites (thereby allowing for

optimal π-donation from the amido and imido nitro-

gens).¹²However, inclusion of significant steric bulk on

the N atoms was shown to invert the site preference.

The geometry found for 15 is therefore the electronically

preferred one, i.e., with an axial imido ligand. However,

this is clearly associated with unfavorable steric repul-

sion, which cannot be relieved due to the enforcing

nature of the tetradentate N₂NN′ ligand.

Figure 3. Displacement ellipsoid plot (25% probability)

of Ti(NAr)(N₂NN′) (15). H atoms omitted for clarity. Atoms

carrying the suffix ‘A’ are related to their counterparts by

3

the symmetry operator [x, y, /₂- z].

Table 3. Selected Bond Lengths (Å) and Angles

(deg) for Ti(NAr)(N₂NN′) (15)^a

Ti(1)-N(1)

Ti(1)-N(2)

1.769(2)

1.992(1)

Ti(1)-N(3)

Ti(1)-N(4)

2.291(2)

2.227(2)

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

108.35(4) N(1)-Ti(1)-N(4)

92.13(7)

N(2)-Ti(1)-N(2A) 112.67(8) N(2)-Ti(1)-N(4) 116.38(4)

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

N(2)-Ti(1)-N(3)

163.77(7) N(3)-Ti(1)-N(4)

79.94(4) Ti(1)-N(1)-C(1)

71.64(6)

164.9(1)

Zirconium imido complexes of N₂NN′ have also been

prepared (Scheme 3). Reaction of Li₂N₂NN′ with the

^aAtoms carrying the suffix ‘A’ are related to their counterparts

3

24

by the symmetry operator [x, y,

/ - z].

2

imido synthon Zr₂(µ-NAr)₂Cl₄(THF)₄in a manner

analogous to that used for 14 and 15 gave a complex

mixture of products. However, reaction of in situ gener-

ated Zr(CH₂SiMe₃)₂(N₂NN′) (4) with ArNH₂(1 equiv)

afforded the target imido compound Zr(NAr)(N₂NN′)

(16) as an orange, sparingly soluble solid in low yield.

The corresponding NMR tube scale reaction in C₆D₆

identified SiMe₄as the expected side-product. Weakly

diffracting crystals of 16 were found to have a unit cell

very similar to that of 15, but the diffraction data were

too weak for a satisfactory refinement to be carried out.

Nonetheless, on the basis of the available data it is likely

that 16 has the five-coordinate monomeric structure

shown in Scheme 3.

We have shown previously²⁰that the readily prepared

compounds Ti(NR)Cl₂(py)₃are useful reagents in the

21

synthesis of new titanium imido compounds. Reaction

of Ti(N^tBu)Cl₂(py)₃or Ti(NAr)Cl₂(py)₃(Ar ) 2,6-C₆H₃-

i

Pr₂) with Li₂N₂NN′ in benzene gave the five-coordinate

imido complexes Ti(NR)(N₂NN′) (R ) ^tBu (14) or Ar (15))

in ca. 60% isolated yield. The NMR spectra were

consistent with the C_ssymmetric structures illustrated

in Scheme 3 and confirmed by X-ray diffraction for 15

as shown in Figure 3. Selected bond distances and

angles are listed in Table 3.

Molecules of 15 lie across crystallographic mirror

planes that pass through the atoms Ti(1), N(1), N(3),

and N(4). Disorder associated with the methylene

linkages about N(3) was satisfactorily modeled. The

geometry at Ti(1) is distorted trigonal bipyramidal with

N(1) and N(3) occupying the apical positions. The Ti-

(1)-N(1)-C(1) angle of 164.9(1)° is typical for a formally

“linear” imido group with N(1) being formally sp hybrid-

ized and, in principle, capable of acting as a four-

electron donor. The bonding in related diamide-donor

supported trigonal bipyramidal imido complexes has

been analyzed in detail recently, as discussed below.¹²

The Ti-N_amineand Ti-N_amidedistances are within the

usual ranges for such linkages,²²whereas Ti(1)-N(1)

is rather long at 1.769(2) Å. The range for terminal Tid

Attempts to prepare a tert-butyl imido compound by

reaction of ZrCl₂(N₂NN′) 1 with 2 equiv of LiNH^tBu gave

the six-coordinate bis(tert-butyl amide) complex 17 in

t

49% yield. The compound does not eliminate BuNH₂

on heating at 70 °C for extended periods in C₆D₆either

on its own or in the presence of pyridine. Reaction of

t

ZrMe₂(N₂NN′) (2) with BuNH₂(1 equiv) in C₆D₆in a

manner akin to that employed for 16 gave only 17 (ca.

30% yield based on 2, the remainder remaining unre-

acted) after 24 h. The corresponding reaction of in situ

generated 4 also failed to produce an imido complex.

Analogous results have been found previously in the

reactions of zirconium dichloride or dialkyl compounds

with less sterically demanding lithiated amides or

(20) Mountford, P. Chem. Commun. 1997, 2127 (Feature article

review). Hazari, N.; Mountford, P. Acc. Chem. Res., in press.

(21) Blake, A. J.; Collier, P. E.; Dunn, S. C.; Li, W.-S.; Mountford,

P.; Shishkin, O. V. J. Chem. Soc., Dalton Trans. 1997, 1549.

(22) Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, 1

& 31. Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. Chem. Inf.

Comput. Sci. 1996, 36, 746.

(23) Blake, A. J.; Collier, P. E.; Gade, L. H.; Mountford, P.; Pugh,

S. M.; Schubart, M.; Skinner, M. E. G.; Tro¨sch, D. J. M. Inorg. Chem.

2001, 40, 870.

(24) Arney, D. J.; Bruck, M. A.; Huber, S. R.; Wigley, D. E. Inorg.

Chem. 1992, 31, 3749. Dubberley, S. R.; Evans, S. E.; Boyd, C. L.;

Mountford, P. Dalton Trans. 2005, 1448.

5592 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

Table 4. Selected Bond Lengths (Å) and Angles

(deg) for Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19)

Zr(1)-N(1)

Zr(1)-N(2)

Zr(1)-N(3)

2.160(1)

2.168(1)

2.520(2)

Zr(1)-N(4)

Zr(1)-N(5)

Zr(1)-N(6)

2.452(1)

2.075(2)

2.091(2)

N(1)-Zr(1)-N(2)

N(1)-Zr(1)-N(3)

N(2)-Zr(1)-N(3)

N(1)-Zr(1)-N(4)

N(2)-Zr(1)-N(4)

N(3)-Zr(1)-N(4)

N(1)-Zr(1)-N(5)

N(2)-Zr(1)-N(5)

141.83(6)

84.02(5)

88.59(5)

73.40(5)

69.18(5)

67.63(5)

112.04(6)

104.17(6)

N(3)-Zr(1)-N(5)

N(4)-Zr(1)-N(5)

N(1)-Zr(1)-N(6)

N(2)-Zr(1)-N(6)

N(3)-Zr(1)-N(6)

N(4)-Zr(1)-N(6)

N(5)-Zr(1)-N(6)

83.45(6)

150.14(6)

90.53(6)

94.20(6)

174.01(6)

108.45(6)

100.96(7)

substituents at the trigonal planar (sp²hybridized)

atoms N(5) and N(6) can be rationalized in terms of

maximizing N(2p_π) f Zr(4d_π) donation.^10b

Figure 4. Displacement ellipsoid plot (25% probability)

of Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19). C-bound H atoms omit-

ted for clarity. H atom bound to N(5) drawn as a sphere of

arbitrary radius.

primary amines.²⁵However, when the reaction between

4 and ^tBuNH₂(1 equiv) was carried out in the presence

of pyridine, the dark red, six-coordinate imido complex

Zr(N^tBu)(py)(N₂NN′) (18) was obtained in 73% yield.

The C_ssymmetrical structure proposed for 18 in Scheme

3 is based on the available NMR data (e.g., equivalent

SiMe₃groups). The presence of coordinated pyridine is

also clearly indicated by the NMR data, and NOE

experiments established the relative arrangements of

the N^tBu, N₂NN′, and pyridine ligands.

Although the use of pyridine in 18 allows access to

this terminal imido compound, it still reacts readily with

primary amines to form tetrakis(amido) derivatives.

Thus addition of ^tBuNH₂(1 equiv) to a C₆D₆solution of

18 quantitatively afforded 17 and free pyridine. This

type of reaction has been seen previously for zirconium

imido compounds.^25a,26An analogous reaction between

18 and piperidine gave the mixed amide complex Zr-

(NH^tBu)(NC₅H₁₀)(N₂NN′) (19) as the single isomer

illustrated in Scheme 3 and confirmed by X-ray crystal-

lography (see below). Compound 19 was made on a

preparative scale in 52% yield from the “one-pot”

reaction of in situ generated 4 with ^tBuNH₂, piperidine,

and pyridine.

The molecular structure of 19 is shown in Figure 4,

and selected bond distances and angles are listed in

Table 4. The overall geometry is analogous to that found

for ZrX₂(N₂NN′) (X ) Cl, NMe₂,^10bCH₂Ph (3, Figure 1),

and ZrCl(CH₂Ph)(N₂NN′) (6, Figure 2)). The N-H atom

of the ^tBuNH ligand was found from a Fourier difference

map and positionally and isotropically refined. The Zr-

(1)-N(1) and Zr(1)-N(2) distances are experimentally

identical to the corresponding distances in Zr(NMe₂)₂(N₂-

NN′).^10bZr(1)-N(5) is marginally shorter than Zr(1)-

N(6) (∆ ) 0.016(3) Å), and both of these distances are

shorter than those to N(1) and N(2). The trends in Zr-

N_amidedistances is the same as in Zr(NMe₂)₂(N₂NN′).

As proposed previously,^10bthe relative orientation of the

We have previously reported^19bthe synthesis and sol-

id-state structures of the group 5 diamide-donor sup-

ported imido compounds M(NR)Cl{(2-C₅H₄N)C(Me)(CH₂-

t

NSiMe₃)₂} (M ) Nb or Ta; R ) Bu or Ar), which were

prepared from Li₂[(2-C₅H₄N)C(Me)(CH₂NSiMe₃)₂] and

the appropriate imido reagent M(NR)Cl₃(py)₂.²⁷In

contrast, reaction between Li₂[Me₃SiN(CH₂CH₂NSiMe₃)₂]

and Nb(N^tBu)Cl₃(py)₂gave a mixture of diamide-amine

ligand degradation and ill-defined dimeric imido com-

pounds. For the purposes of comparison with these

previous studies and the new N₂NN′-supported imido

chemistry described in Scheme 3 we carried out the

reactions summarized in eq 1.

Reaction of Li₂N₂NN′ with M(N^tBu)Cl₃(py)₂in ben-

zene followed by crystallization from pentane afforded

the six-coordinate imido complexes M(N^tBu)Cl(N₂NN′)

(M ) Nb (20) or Ta (21)) as yellow or brown solids in

ca. 30% isolated yield (eq 1). The low isolated yield is

attributed to the rather high solubility of these com-

pounds in pentane since the NMR tube scale reactions

(C₆D₆) were quantitative. The NMR spectra for the two

compounds were virtually identical and support the C₁

symmetrical structures illustrated in eq 1 (e.g., in-

equivalent SiMe₃groups and 10 independent multiplet

resonances (each of relative integration 1 H for the

methylene hydrogens). The solid-state structure of 21

is shown in Figure 5, and selected bond distances and

angles are listed in Table 5. There are two crystallo-

graphically independent molecules of 21 in the asym-

metric unit but no substantial differences between them.

The structure of 21 in the solid state agrees with that

assigned on the basis of the solution NMR data. The

geometry at Ta(1) is approximately octahedral, and the

metal-ligand distances are within previously reported

ranges.²²It is of particular interest to compare this

structure with that of Ta(N^tBu)Cl{(2-C₅H₄N)C(Me)(CH₂-

NSiMe₃)₂},^19bin which the imide and amide donors are

(25) (a) Nikonov, G. I.; Blake, A. J.; Mountford, P. Inorg. Chem. 1997,

36, 1107. (b) Dubberley, S. R.; Friedrich, A.; Willman, D. A.; Mountford,

P.; Radius, U. Chem. Eur. J. 2003, 9, 3634.

(26) Walsh, P. J.; Baranger, A. M.; Bergman, R. G. J. Am. Chem.

Soc. 1992, 114, 1708.

(27) Sundermeyer, J.; Putterlik, J.; Foth, M.; Field, J. S.; Ramesar,

N. Chem. Ber. 1994, 127, 1201.

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5593

(CH₂R)₂(N₂NN′) (R ) SiMe₃(4) or CMe₃(5)) may also

stem from increased crowding in these silylamido

systems. To test these ideas, we have developed a bis-

(alkoxide) analogue of N₂NN′, namely, O₂NN′ (O₂NN′

) (2-C₅H₄N)CH₂N(CH₂CMe₂O)₂), in which the NSiMe₃

group is replaced by O. Polydentate ligands with two

anionic oxygen donors are extremely well established

in early transition metal chemistry,^4-6,8as are the

related phenoxide-imine ligands (monoanionic N,O do-

nors).⁷Interestingly, although dianionic O₂N₂donor

atom ligands with phenoxide groups are very well

established in group 4,^5-6,8the corresponding bis-

(alkoxide)-diamine systems are underdeveloped (triden-

tate O₂N donor bis(alkoxide)-monoamine ligand systems

are, however, better known⁹).

Figure 5. Displacement ellipsoid plot (25% probability)

of one of the two crystallographically independent mol-

ecules of Ta(N^tBu)Cl(N₂NN′) (21). H atoms omitted for

clarity.

Table 5. Selected Bond Lengths (Å) and Angles

(deg) for Ta(N^tBu)Cl(N₂NN′) (21)^a

Our initial efforts focused on the known²⁸protio

ligand (2-C₅H₄N)CH₂N(CH₂CH₂OH)₂used previously in

vanadium^28aand nickel chemistry.^28bHowever, reaction

of this with a number of titanium and zirconium

precursors of the type MX₂R₂(X or R ) alkyl, halide, or

NMe₂) gave rather insoluble and intractable products.

Reasoning that the O atoms in (2-C₅H₄N)CH₂N(CH₂-

CH₂OH)₂are too sterically unprotected, we moved our

attention to the new ligand system O₂NN′, in which a

gem-dimethyl group is positioned next to each O (mak-

ing the ligand a little like a bis(tert-butoxide) system).

The protio ligand H₂O₂NN′ (22) was prepared from

2-aminomethyl pyridine and isobutylene oxide in the

presence of a catalytic quantity of ethanol (eq 2) and

isolated as a white powder in ca. 50% yield after column

chromatography and high-vacuum sublimation.

H₂O₂NN′ (22) was structurally characterized. The

molecular structure is shown in Figure 6, and selected

intra- and intermolecular distances are listed in Table

6. The associated distances and angles are within the

usual ranges.²²The O-bound H atoms were located from

Fourier difference maps and positionally refined. Mol-

ecules of H₂O₂NN′ form eight-membered intramolecular

hydrogen-bonded rings (via O(1)-H(1)‚‚‚O(2)), and each

H₂O₂NN′ is part of a supramolecular chain motif

propagating along the crystallographic b axis via hy-

drogen bonds between O(1) of one molecule and H(2) of

its neighbor. Neither N atom is involved in a supramo-

lecular interaction. The ¹H NMR spectrum of H₂O₂NN′

in CD₂Cl₂at 20 °C showed (in addition to pyridyl and

OH signals) resonances for a single methyl group

environment (relative integral 12 H) and two methylene

environments (2 and 4 H for (2-C₅H₄N)CH₂N and

N(CH₂Me₂OH)₂, respectively), indicating that no in-

tramolecular order is maintained (at least on the NMR

time scale) at this temperature. Cooling to -90 °C led

to significant broadening of the N(CH₂Me₂OH)₂meth-

Ta(1)-Cl(1)

Ta(1)-N(1)

Ta(1)-N(2)

Ta(1)-N(3)

Ta(1)-N(4)

Ta(1)-N(5)

2.5500(9)

2.055(3)

2.029(3)

2.274(3)

2.363(3)

1.783(3)

[2.515(1)]

[2.055(3)]

[2.034(3)]

[2.309(3)]

[2.379(3)]

[1.791(3)]

Cl(1)-Ta(1)-N(1)

Cl(1)-Ta(1)-N(2)

N(1)-Ta(1)-N(2)

Cl(1)-Ta(1)-N(3)

N(1)-Ta(1)-N(3)

N(2)-Ta(1)-N(3)

Cl(1)-Ta(1)-N(4)

N(1)-Ta(1)-N(4)

N(2)-Ta(1)-N(4)

N(3)-Ta(1)-N(4)

Cl(1)-Ta(1)-N(5)

N(1)-Ta(1)-N(5)

N(2)-Ta(1)-N(5)

N(3)-Ta(1)-N(5)

N(4)-Ta(1)-N(5)

Ta(1)-N(5)-C(17)

153.77(9)

[153.48(9)]

[90.4(1)]

[103.6(1)]

[75.09(8)]

[81.2(1)]

[146.9(1)]

[83.03(8)]

[77.9(1)]

[78.4(1)]

[70.5(1)]

[93.4(1)]

[103.7(1)]

[106.9(1)]

[103.6(1)]

[173.7(1)]

[165.0(3)]

88.88(9)

104.0(1)

75.30(8)

82.0(1)

147.5(1)

82.17(8)

78.4(1)

78.2(1)

71.7(1)

93.8(1)

103.3(1)

108.4(1)

101.0(1)

172.3(1)

165.5(3)

^aValues in brackets are for the other crystallographically

independent molecule in the asymmetric unit.

also all cis to one another. The Ta-Cl, Ta-N_amine, and

Ta-Cl distances in 21 and Ta(N^tBu)Cl{(2-C₅H₄N)C(Me)-

(CH₂NSiMe₃)₂} are very similar. In contrast, the Tad

N^tBu distances in 21 (1.783(3) and 1.791(3) Å) are

somewhat shorter than in the previous compound

(1.822(4) Å). It is not clear why 20 and 21 adopt

nonsymmetrical structures while all the zirconium

compounds [Zr(A)(B)(N₂NN′)]ⁿ⁺described above with

two different coligands A and B (i.e., 6, 7, 8, 12⁺, 19,

and (especially) 18) have C_ssymmetry.

Group 4 Complexes of O₂NN′. In a previous paper^10b

on the zirconium and hafnium complexes MX₂(N₂NN′)

(X ) Cl or NMe₂) we described how we had been unable

to prepare six-coordinate titanium analogues TiX₂(N₂-

NN′). This was tentatively attributed to the possible

difficulties in placing six ligands around Ti at the

shorter metal-ligand bond lengths required for this 3d

metal. The instability of the zirconium complexes Zr-

(28) (a) Crans, D. C.; Keramidas, A. D.; Amin, S. S.; Anderson, O.

P.; Miller, S. M. J. Chem. Soc., Dalton. Trans. 1997, 2799. (b)

Saalfrank, R. W.; Bernt, I.; Hampel, F. Chem. Eur. J. 2001, 7, 2770.

5594 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

Scheme 4. Synthesis of Group 4 Dichloride,

Bis(amide), and Dialkyl Complexes of O₂NN′

Figure 6. Displacement ellipsoid plot (25% probability)

of H₂O₂NN′ (22). C-bound H atoms omitted for clarity. H

atoms bound to O drawn as spheres of arbitrary radius.

Table 6. Selected Bond Lengths (Å) and Angles

(deg) for H₂O₂NN′ (22)^a

N(1)-C(2)

N(1)-C(9)

N(2)-C(14)

O(1)-H(1)

O(2)-C(3)

O(2)-H(2)

1.469(2)

1.470(2)

1.347(2)

0.88(2)

1.440(2)

0.88(2)

N(1)-C(4)

N(2)-C(10)

O(1)-C(1)

O(1)‚‚‚H(2A)

O(2)‚‚‚H(1)

1.473(2)

1.339(2)

1.438(2)

1.88(2)

1.83(2)

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

C(4)-N(1)-C(9)

C(1)-O(1)-H(1)

114.2(1)

110.5(1)

C(2)-N(1)-C(9)

111.9(1)

C(10)-N(2)-C(14) 117.39(13)

atoms and CMe₂methyl groups of each are also in-

equivalent. The shifts of the pyridyl group are rather

similar to those in H₂O₂NN′ itself, suggesting that it is

not coordinated. The structure proposed for 23 is

analogous to that found by X-ray diffraction for the

homologous bis(alkoxide)-methylamine complex Ti{MeN-

(CH₂CH₂O)₂}₂, isolated from the reaction of amorphous

R-titanic acid with MeN(CH₂CH₂OH)₂.⁹ⁱ

109.0(12) C(1)-O(1)-H(2A) 128.7(6)

110.4(13)

O(1B)‚‚‚H(2)-O(2) 169(2)

H(1)-O(1)-H(2A) 102.5(14) C(3)-O(2)-H(2)

O(1)-H(1)‚‚‚O(2) 167(2)

^aAtoms carrying the suffixes ‘A’ and ‘B’ are related to their

counterparts by the symmetry operator [³/₂- x, y + ¹/₂,

/ - z]

2

3

and [³/₂- x, y - ¹/₂,

/ - z], respectively.

2

3

ylene signal and splitting of the N(CH₂Me₂OH)₂methyl

resonance to two broad resonances, each of relative

integral 6 H. This is consistent with a greater degree of

ordering of the intramolecular H bonding at low tem-

perature.

Attempts to prepare Li₂O₂NN′ or other alkali metal

bis(alkoxide) salts by reaction of H₂O₂NN′ with BuLi,

MeLi, NaH, or KH gave decomposition products, and

so all complexation reactions needed to take place using

only the protio ligand. The synthesis and proposed

structures of the new neutral organometallic and coor-

dination complexes of O₂NN′ are shown in Scheme 4.

Reaction of Ti(NMe₂)₄with H₂O₂NN′ (1 equiv) gave

ca. 50% conversion to the white homoleptic compound

Ti(O₂NN′)₂(23) with ca. 50% of the Ti(NMe₂)₄remaining

unreacted. The preference for formation of 23 over the

desired product Ti(NMe₂)₂(O₂NN′) persisted regardless

of the method of addition, solvent, or reaction conditions.

Reaction of Ti(NMe₂)₄with H₂O₂NN′ (2 equiv) gave 23

in ca. 80% isolated yield. Compound 23 is fluxional at

room temperature, giving rise to broad NMR spectra.

On cooling to -80 °C, a sharp, low-temperature limit

¹H spectrum was obtained which is consistent with the

C₂symmetric structure (equivalent O₂NN′ ligands)

illustrated in Scheme 4. The two CH₂CMe₂O “arms” of

each ligand are inequivalent, and the methylene H

The redistribution reaction between 23 and TiCl₄-

(THF)₂in benzene gave the sparingly soluble dichloride

complex TiCl₂(O₂NN′) (24) as a white solid in 90%

isolated yield. The NMR spectrum of 24 shows C_s

symmetry with equivalent “arms” (featuring diastereo-

topic CH₂and CMe₂groups as expected). The EI mass

spectrum of 24 showed a parent ion with the appropri-

ate isotope distribution. The zirconium analogue of 24

was prepared in a similar way to that used for ZrCl₂(N₂-

NN′) (1), namely, by reaction of the protio ligand with

ZrCl₂(CH₂SiMe₃)₂(Et₂O)₂.²⁹The compound ZrCl₂(O₂NN′)

(25) was isolated in 52% yield, and the NMR and other

data were analogous to those of 24. Protonolysis routes

were also used for the synthesis of Zr(NMe₂)₂(O₂NN′)

(26) and Zr(CH₂SiMe₃)₂(O₂NN′) (27) from Zr(NMe₂)₄and

Zr(CH₂SiMe₃)₄, respectively. The expected side products

SiMe₄and HNMe₂were identified in NMR tube scale

experiments. In contrast to Zr(CH₂SiMe₃)₂(N₂NN′) (4),

which decomposes at room temperature over several

hours, the dialkyl compound 27 appears to be indefi-

nitely stable in solution at room temperature and has

been crystallographically characterized. The molecular

structure is shown in Figure 7, and selected bond

n

(29) Brand, H.; Capriotti, J. A.; Arnold, J. Organometallics 1994,

13, 4469.

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5595

Scheme 5. Synthesis of Cationic Zirconium

Complexes of O₂NN′ (anions omitted for clarity)

Figure 7. Displacement ellipsoid plot (30% probability)

of one of the two crystallographically independent mol-

ecules of Zr(CH₂SiMe₃)₂(O₂NN′) (27). H atoms omitted for

clarity.

Table 7. Selected Bond Lengths (Å) and Angles

(deg) for Zr(CH₂SiMe₃)₂(O₂NN′) (27)^a

Zr(1)-N(1)

Zr(1)-N(2)

Zr(1)-O(1)

Zr(1)-O(2)

Zr(1)-C(15)

Zr(1)-C(19)

2.482(3)

2.514(3)

1.983(3)

1.985(3)

2.261(4)

2.295(4)

[2.479(3)]

[2.516(3)]

[1.981(3)]

[1.978(3)]

[2.271(4)]

[2.293(4)]

attributed to several factors, including the bulkier

nature of N₂NN′ vs O₂NN′ and SiMe₃vs Ph and the

presence of the additional Zr‚‚‚C_ipsointeraction in 3. In

contrast to 3, there are no acute Zr-CH₂-R angles

(range 120.9(2)-125.8(2)°) in 27.

N(1)-Zr(1)-N(2)

N(1)-Zr(1)-O(1)

N(2)-Zr(1)-O(1)

N(1)-Zr(1)-O(2)

N(2)-Zr(1)-O(2)

O(1)-Zr(1)-O(2)

N(1)-Zr(1)-C(15)

N(2)-Zr(1)-C(15)

O(1)-Zr(1)-C(15)

O(2)-Zr(1)-C(15)

N(1)-Zr(1)-C(19)

N(2)-Zr(1)-C(19)

O(1)-Zr(1)-C(19)

O(2)-Zr(1)-C(19)

C(15)-Zr(1)-C(19)

Zr(1)-C(15)-Si(1)

Zr(1)-C(19)-Si(2)

Zr(1)-O(1)-C(1)

Zr(1)-O(2)-C(3)

68.30(11)

[68.3(1)]

Scheme 5 summarizes the reactions of 27 with BAr^F

3

72.03(11)

85.66(11)

71.98(11)

85.49(11)

143.69(11)

154.25(13)

85.96(13)

106.95(13)

107.44(13)

106.69(13)

174.77(14)

91.35(14)

94.45(14)

99.03(15)

124.0(2)

[72.22(11)]

[81.95(11)]

[72.01(11)]

[88.60(11)]

[144.00(11)]

[154.70(13)]

[86.77(13)]

[109.61(13)]

[104.39(13)]

[102.76(14)]

[170.52(14)]

[92.45(14)]

[91.53(14)]

[102.37(16)]

[120.9(2)]

to form alkyl zirconium cations. In the presence of THF,

dichloromethane solutions of 27 react with BAr^Fto

3

form [Zr(CH₂SiMe₃)(THF)(O₂NN′)][Me₃SiCH₂BAr^F] (28-

3

Me₃SiCH₂BAr^F₃) in 87% isolated yield. The NMR data

-

for the [Me₃SiCH₂BAr^F

]

3

anion show that it is nonco-

ordinating. The [Zr(CH₂SiMe₃)(THF)(O₂NN′)]⁺cation

(28⁺) is proposed to have the C_ssymmetrical structure

illustrated in Scheme 5. The relative positions of the

CH₂SiMe₃, THF, and pyridyl groups were determined

by NOE experiments. The base-stabilized cation 28⁺is

analogous to [ZrMe(THF)(O₂NN′)]⁺(12⁺, Scheme 2) and

to previously described bis(phenolate)-diamine monoalkyl

cations, for example, [Zr(CH₂Ph)(THF){(2-C₅H₄N)CH₂N-

(2-O-3,5-C₆H₂R₂)₂}]⁺.^8j

124.7(2)

[125.8(2)]

130.5(2)

[130.7(2)]

129.9(2)

[129.7(2)]

Reaction of 27 with BAr^F₃in dichloromethane in the

^aThe values in brackets are for the other crystallographically

independent molecule in the asymmetric unit.

absence of THF gave the compound 29-Me₃SiCH₂BAr^F

3

as a white solid in 90% yield. In addition to resonances

-

distances and angles are listed in Table 7. There are

two crystallographically independent molecules of 27 in

the asymmetric unit with no substantial differences

between them.

Molecules of 27 have approximately octahedral metal

centers with Zr-N, -O, and -C distances within the

usual ranges.²²The overall coordination environment

is analogous to both the previously described bis-

(phenolate)-diamine complexes ZrX₂{(2-C₅H₄N)CH₂N-

for a noncoordinating [Me₃SiCH₂BAr^F

]

3

anion, the

NMR spectra showed the formation of a C₁symmetric

species “[Zr(CH₂SiMe₃)(O₂NN′)]⁺”. The methylene H

atoms of the alkyl ligand appear as a pair of mutually

coupled doublets, and the methyl groups and methylene

H atoms of O₂NN′ are all inequivalent. On the basis of

these data and selected NOE experiments it is proposed

that 29-Me₃SiCH₂BAr^Fcontains the bimetallic cation

3

[Zr₂(CH₂SiMe₃)₂(O₂NN′)₂]²⁺(Scheme 5). The dication

has six-coordinate Zr centers linked by bridging alkoxide

O atoms (each O₂NN′ has one bridging and one non-

bridging CH₂CMe₂O “arm”).

t

(2-O-3,5-C₆H₂R₂)₂} (X ) Cl, NMe₂, alkyl; R ) Bu or

Me)^8j,land Zr(CH₂Ph)₂(N₂NN′) (3). The formal replace-

ment of the CH₂NSiMe₃groups of N₂NN′ by -CMe₂O

in O₂NN′ has clearly provided for a more open metal

center. Surprisingly, the Zr-N_aminedistances in 3 are

both somewhat shorter than the corresponding values

in 27 despite the apparent greater crowding in the

former. The CH₂-Zr-CH₂angle in 27 (av 100.7°) is

more acute than that in 3 (87.09(9)°), which can be

Compounds with Zr₂(µ-O)₂cores are structurally well

established.²²The structure proposed for 29²⁺can, in

particular, be compared to recently reported^8cdimeric

neutral or dicationic complexes Sc₂Cl₂{(2-C₅H₄N)CH₂N(2-

O-3,5-C₆H₂Me₂)₂}₂(III, structurally characterized) and

[Ti₂Me₂{(2-C₅H₄N)CH₂N(2-O-3,5-C₆H₂R₂)₂}₂]²⁺(IV, R )

5596 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

¹H and ¹³C assignments were confirmed with the use of DEPT-

135 and two-dimensional ¹H-¹H and ¹³C-¹H NMR experi-

ments. ¹H and ¹³C spectra were referenced internally to

residual protio-solvent (¹H) or solvent (¹³C) resonances and are

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

¹¹B spectra were referenced externally to CFCl₃and BF₃‚Et₂O,

respectively. Chemical shifts are quoted in δ (ppm) and

coupling constants in hertz. Infrared spectra were prepared

as Nujol mulls and were recorded on Perkin-Elmer 1600 and

1710 series FTIR spectrometers; data are quoted in wavenum-

bers (cm^-1). Mass spectra were recorded by the mass spec-

trometry services of the University of Oxford Department of

Chemistry, and elemental analyses by the analytical services

of the University of Oxford Inorganic Chemistry Laboratory.

Literature Preparations and Other Starting Materi-

als. The compounds H₂N₂NN′,^10bLi₂N₂NN′,^10bZrCl₂(N₂NN′)

(1),^10bTi(NR)Cl₂(py)₃(R ) ^tBu or Ar),²¹Zr(CH₂SiMe₃)₄,³⁰

Zr(CH₂CMe₃)₄,³¹Zr(CH₂SiMe₃)₂Cl₂(Et₂O)₂,²⁹M(NMe₂)₄(M ) Ti

or Zr),³²TiCl₄(THF)₂,³³LiCH₂SiMe₃,³⁴and M(N^tBu)Cl₃(py)₂(M

) Nb or Ta)²⁷were prepared according to published methods.

Samples of BAr^F₃were provided by DSM Research. Pyridine,

^tBuNH₂, ArNH₂, and piperidine were dried over the appropri-

ate drying agents and distilled under reduced pressure. All

other compounds and reagents were purchased and used

without further purification.

t

Me or Bu). Whereas the titanium dication [Ti₂Me₂{(2-

C₅H₄N)CH₂N(2-O-3,5-C₆H₂R₂)₂}₂]²⁺is very fluxional on

the NMR time scale at room temperature (the fluxional

process being frozen out at -80 °C), the dizirconium

complex 29²⁺is not. This is attributed to the reduced

steric crowding about the µ-O atoms in the later (despite

the presence of the neighboring CMe₂units) and the

larger radius of Zr. The discandium complex III was

static on the NMR time scale at room temperature,

there being much less Coulombic repulsion between the

metal centers in this case.

Addition of ethylene (1 bar) to NMR tube samples of

29-Me₃SiCH₂BAr^F₃gave no polymerization activity (the

same observation was made^8cfor solutions of [Ti₂Me₂-

ZrMe₂(N₂NN′) (2). To a solution of ZrCl₂(N₂NN′) (1) (490

mg, 0.98 mmol) in benzene (20 mL) was added dropwise a

solution of MeLi (1.6 M in Et₂O, 0.62 mL, 0.98 mmol) in

benzene (5 mL). After stirring for 12 h another equivalent of

MeLi (1.6 M in Et₂O, 0.62 mL, 0.98 mmol), in benzene (5 mL),

was added dropwise. The mixture was stirred for a further 4

h, after which time the volatiles were removed under reduced

pressure, giving crude ZrMe₂(N₂NN′) (2) as a light brown solid.

This was extracted into pentane (3 × 15 mL) and filtered, and

the combined extracts were concentrated to 5 mL. Cooling the

solution to -30 °C produced 2 as a white solid, which was

washed with cold pentane and dried in vacuo. Yield: 397 mg

(88%).

t

{(2-C₅H₄N)CH₂N(2-O-3,5-C₆H₂Bu₂)₂}₂]²⁺), indicating that

in these O₂NN′-supported systems the formation of

alkoxide-bridged dimers is a potent catalyst deactivation

pathway. Unsurprisingly, in the light of this, none of

the compounds MX₂(O₂NN′) (M ) Ti or Zr; X ) Cl or

CH₂SiMe₃) showed any significant ethylene polymeri-

zation capability when activated with either methyl

aluminoxane or (for 27) BAr^F₃or [CPh₃][BAr^F] (toluene

4

solvent, 5 bar ethylene pressure, room temperature).

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.59 (1 H, d, J 5.0

3

Conclusions

Hz, 6-C₅H₄N), 6.77 (1 H, dd, J 8.0, 7.0 Hz, 4-C₅H₄N), 6.38 (1

H, dd, ³J 5.0, 7.0 Hz, 5-C₅H₄N), 6.31 (1 H, d, ³J 8.0 Hz,

3-C₅H₄N), 3.43 (2 H, m, NCH₂CH₂NSi), 3.29 (2 H, s, C₅H₄-

NCH₂), 3.09 (2 H, m, NCH₂CH₂NSi), 2.54 (2 H, m, NCH₂CH₂-

NSi), 2.09 (2 H, m, NCH₂CH₂NSi), 0.79 (2 H, s, ZrCH₃), 0.70

(2 H, s, ZrCH₃), 0.36 (18 H, s, Si(CH₃)₃). ¹³C{¹H} NMR (125.7

MHz, 293 K, C₆D₆): δ 158.5 (2-C₅H₄N), 150.1 (6-C₅H₄N), 137.8

(4-C₅H₄N), 122.9 (5-C₅H₄N), 121.8 (3-C₅H₄N), 58.3 (C₅H₄NCH₂),

57.9 (NCH₂CH₂NSi), 48.0 (NCH₂CH₂NSi), 41.8 (ZrCH₃), 36.4

(ZrCH₃), 1.3 (Si(CH₃)₃). IR (CsBr plates, Nujol): ν 1604 (m),

1572 (w), 1303 (w), 1280 (w), 1243 (s), 1154 (w), 1074 (s), 1035

(w), 1008 (w), 942 (m), 916 (m), 834 (s), 804 (m), 757 (m), 731

(w), 678 (w), 594 (w), 560 (w), 535 (w), 484 (w) cm^-1. EI-MS:

m/z 441 (28%), [M - CH₃]⁺; 425 (100%), [M - 2CH₃, H]⁺. Anal.

Found (calcd for C₁₈H₃₈N₄Si₂Zr): C, 46.0 (47.2); H, 8.1 (8.4);

N, 11.8 (12.2).

Zr(CH₂Ph)₂(N₂NN′) (3). To a yellow solution of ZrCl(CH₂-

Ph)(N₂NN′) (6) (204 mg, 0.37 mmol) in benzene (20 mL) cooled

to 5 °C was added PhCH₂MgCl (1.0 M in Et₂O, 368 µL, 0.37

mmol) in benzene (5 mL). The mixture was allowed to warm

to room temperature and stirred for 18 h, giving an opaque,

dark orange solution. The volatiles were removed under

reduced pressure, yielding an orange solid, which was tritu-

rated with pentane and dried in vacuo to afford pale yellow 3.

Yield: 140 mg (62%).

The N₂NN′ ligand provides a useful support for a

range of organometallic and imido complexes of certain

group 4 and 5 metals, except for when bulky alkyl

groups are involved. As seen in other silylamide-

supported systems, however, monoalkyl cations undergo

intramolecular cyclometalation via SiMe₃group C-H

bond activation. The new O₂NN′ ligand allows for the

syntheses of six-coordinate titanium dichloride and bis-

(dimethylamide) derivatives that were not accessible for

N₂NN′. Furthermore, bulkier dialkyl zirconium deriva-

tives are apparently more stable with the bis(alkoxide)-

diamine ligand. The formation of cationic µ-alkoxide-

bridged dimers probably accounts for (or at least

contributes to) the lack of any significant ethylene

polymerization activity with the O₂NN′-supported sys-

tems.

Experimental Section

General Methods and Instrumentation. All manipula-

tions were carried out using standard Schlenk line or drybox

techniques under an atmosphere of argon or of dinitrogen.

Protio- and deutero-solvents were predried over activated 4 Å

molecular sieves and were refluxed over the appropriate drying

agent, distilled, 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, ¹³C{¹H}, ¹³C, and ¹⁹F NMR spectra were recorded on Varian

Mercury-VX 300 and Varian Unity Plus 500 spectrometers.

(30) Collier, M. R.; Lappert, M. F. J. Chem. Soc., Dalton Trans. 1973,

445.

(31) Davidson, P. J.; Lappert, M. F.; Pearce, R. J. Organomet. Chem.

1973, 57, 269.

(32) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857.

(33) Manzer, L. E. Inorg. Synth. 1982, 21, 135.

(34) Tessier-Youngs, C.; Beachley, O. T. Inorg. Synth. 1986, 24, 95.

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5597

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.14 (1 H, d, J 5.5

yellow extract was filtered, and the volatiles were removed

under reduced pressure to give 6 as a yellow solid. Yield: 486

mg (87%).

Hz, 6-C₅H₄N), 7.35 (2 H, d, ³J 8.5 Hz, o-C₆H₅), 7.30 (2 H, t, ³J

7.5, 14 Hz, m-C₆H₅), 7.11 (2 H, t, J 8.5, 6 Hz, m-C₆H₅), 7.06

(2 H, d, J 7.5 Hz, o-C₆H₅), 6.85 (2 H, m, p-C₆H₅), 6.66 (1 H,

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 9.26 (1 H, d, J 5.0

dd, ³J 8.0, 7.5 Hz, 4-C₅H₄N), 6.23 (1 H, dd, ³J 5.5, 7.5 Hz,

5-C₅H₄N), 6.19 (1 H, d, ³J 8.0 Hz, 3-C₅H₄N), 3.28 (2 H, m,

NCH₂CH₂NSi), 3.15 (2 H, s, C₆H₅CH₂), 3.06 (2 H, s, C₆H₅CH₂),

2.94 (2 H, s, C₅H₄NCH₂), 2.91 (2 H, m, NCH₂CH₂NSi), 2.06 (2

H, m, NCH₂CH₂NSi), 1.76 (2 H, m, NCH₂CH₂NSi), 0.30 (18

Hs, Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, C₆D₆): δ 157.4

(2-C₅H₄N), 151.8 (i-C₆H₅), 151.4 (6-C₅H₄N), 150.4 (i-C₆H₅),

137.7 (4-C₅H₄N), 128.8 (o-C₆H₅), 127.0 (m-C₆H₅), 122.3 (5-

C₅H₄N), 122.2 (3-C₅H₄N), 120.6 (o-, m-C₆H₅), 118.6 (2 ×

overlapping p-C₆H₅), 73.1 (C₆H₅CH₂), 65.3 (C₆H₅CH₂), 58.1

(C₅H₄NCH₂), 56.7 (NCH₂CH₂NSi), 48.1 (NCH₂CH₂NSi), 2.0 (Si-

(CH₃)₃). IR (CsBr plates, Nujol): ν 1733 (w), 1605 (w), 1591

(m), 1572 (w), 1302 (w), 1259 (m), 1247 (m), 1206 (w), 1073

(w), 1017 (w), 942 (w), 902 (w), 835 (s), 802 (w), 746 (m), 725

(m), 697 (w), 678 (w), 670 (w), 447 (w) cm^-1. EI-MS: m/z 505

(25%), [M - 2CH₃, Si(CH₃)₃]⁺; 367 (7%), [M - Si(CH₃)₃,

CH₂C₆H₅, C₆H₅]⁺. Anal. Found (calcd for C₃₀H₄₆N₄Si₂Zr): C,

59.4 (59.1); H, 7.8 (7.6); N, 8.8 (9.2).

3

Hz, 6-C₅H₄N), 7.28 (4 H, m, o-, m-C₆H₅), 6.84 (1 H, t, J 6.5

Hz, p-C₆H₅), 6.72 (1 H, dd, ³J 7.5, 7.5 Hz, 4-C₅H₄N), 6.37 (1 H,

dd, ³J 5.0, 7.5 Hz, 5-C₅H₄N), 6.20 (1 H, d, ³J 7.5 Hz, 3-C₅H₄N),

3.33 (2 H, s, C₆H₅CH₂), 3.32 (2 H, m, NCH₂CH₂NSi), 3.03 (2

H, s, C₅H₄NCH₂), 2.90 (2 H, m, NCH₂CH₂NSi), 2.15 (2 H, m,

NCH₂CH₂NSi), 2.09 (2 H, m, NCH₂CH₂NSi), 0.32 (18 H, s, Si-

(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, C₆D₆): δ 157.5 (2-

C₅H₄N), 151.4 (i-C₆H₅), 150.5 (6-C₅H₄N), 138.4 (4-C₅H₄N),

129.3 (o-C₆H₅), 128.3 (m-C₆H₅), 122.9 (5-C₅H₄N), 121.5 (3-

C₅H₄N), 118.7 (p-C₆H₅), 64.7 (C₆H₅CH₂), 57.5 (C₅H₄NCH₂), 57.2

(NCH₂CH₂NSi), 48.7 (NCH₂CH₂NSi), 2.1 (Si(CH₃)₃). IR (CsBr

plates, Nujol): ν 1604 (m), 1589 (m), 1570 (w), 1300 (w), 1206

(m), 1175 (w), 1157 (w), 1083 (s), 1015 (m), 946 (s), 925 (w),

902 (s), 873 (w), 839 (s), 799 (m), 790 (m), 747 (m), 730 (w),

694 (m), 679 (w), 648 (w), 633 (w), 594 (m), 579 (m) cm^-1. EI-

MS: m/z 552 (5%), [M]⁺; 517 (21%), [M - Cl]⁺; 461 (35%), [M

- C₆H₅]⁺. Anal. Found (calcd for C₂₃H₃₉ClN₄Si₂Zr): C, 49.5

(49.8); H, 7.2 (7.1); N, 9.2 (10.1).

NMR Tube Scale Synthesis of Zr(CH₂SiMe₃)₂(N₂NN′)

(4). A solution of H₂N₂NN′ (18 mg, 0.053 mmol) in C₆D₆(ca.

0.75 mL) was added to a sample of Zr(CH₂SiMe₃)₄(20 mg,

0.045 mmol), resulting in the immediate formation of an

orange-red solution. The NMR data were consistent with the

quantitative formation of 4 and 2 equiv of SiMe₄. 4 subse-

quently decomposed to a complex mixture of products over 6

ZrCl(CH₂SiMe₃)(N₂NN′) (7). To a yellow solution of

ZrCl₂(N₂NN′) (1) (113 mg, 0.23 mmol) in benzene (10 mL) was

added dropwise a solution of ClMgCH₂SiMe₃(1.0 M in Et₂O,

215 µL, 0.22 mmol) in benzene (5 mL), resulting in the

immediate formation of a white precipitate. After stirring for

15 min the volatiles were removed under reduced pressure,

producing a yellow solid, which was washed with pentane (20

mL) before being extracted into benzene (3 × 20 mL). The

combined yellow extracts were filtered and the volatiles

removed under reduced pressure to afford 7 as a white solid.

Yield: 117 mg (97%).

1

3

h. H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.61 (1 H, d, J 5.5

3

Hz, 6-C₅H₄N), 6.87 (1 H, dd, J 8.0, 7.5 Hz, 4-C₅H₄N), 6.53 (1

H, dd, ³J 5.5, 7.5 Hz, 5-C₅H₄N), 6.48 (1 H, d, ³J 8.0 Hz,

3-C₅H₄N), 3.47 (2 H, s, C₅H₄NCH₂), 3.41 (2 H, m,NCH₂CH₂-

NSi), 3.33 (2 H, m,NCH₂CH₂NSi), 2.59 (2 H, m,NCH₂CH₂NSi),

2.39 (2 H, m,NCH₂CH₂NSi), 0.84 (2 H, s, CH₂Si(CH₃)₃), 0.58

(2 H, s, CH₂Si(CH₃)₃), 0.31 (18 H, s, NSi(CH₃)₃), 0.24 (9 H, s,

CH₂Si(CH₃)₃), 0.22 (9 H, s, CH₂Si(CH₃)₃). ¹³C{¹H} NMR (125.7

MHz, 293 K, C₆D₆): δ 156.5 (2-C₅H₄N), 150.6 (6-C₅H₄N), 137.3

(4-C₅H₄N), 123.1 (5-C₅H₄N), 122.7 (3-C₅H₄N), 57.1 (NCH₂CH₂-

NSi), 54.2 (CH₂Si(CH₃)₃), 54.2 (CH₂Si(CH₃)₃), 51.1 (C₅H₄NCH₂),

48.0 (NCH₂CH₂NSi), 2.5 (CH₂Si(CH₃)₃), 2.4 (CH₂Si(CH₃)₃), 0.5

( NSi(CH₃)₃).

3

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 9.16 (1 H, d, J 5.5

3

Hz, (6-C₅H₄N), 6.82 (1 H, dd, J 7.8, 7.8 Hz, (4-C₅H₄N), 6.44

(1 H, dd, ³J 5.5, 7.8 Hz, (5-C₅H₄N), 6.36 (1 H, d, ³J 7.8 Hz,

(3-C₅H₄N), 3.49 (2 H, m, NCH₂CH₂NSi), 3.29 (2 H, s, C₅H₄-

NCH₂), 3.09 (2 H, m, NCH₂CH₂NSi), 2.82 (2 H, m, NCH₂CH₂-

NSi), 2.23 (2 H, m, NCH₂CH₂NSi), 1.18 (2 H, s, CH₂Si(CH₃)₃),

0.39 (9 H, s, CH₂Si(CH₃)₃), 0.35 (18 H, s, NSi(CH₃)₃). ¹³C{¹H}

NMR (75.5 MHz, 293 K, C₆D₆): δ 157.0 (2-C₅H₄N), 150.8 (6-

C₅H₄N), 138.1 (4-C₅H₄N), 123.0 (5-C₅H₄N), 121.3 (3-C₅H₄N),

59.7 (C₅H₄NCH₂), 59.2 (NCH₂CH₂NSi), 53.0 (CH₂Si(CH₃)₃),

50.0 (NCH₂CH₂NSi), 4.0 (CH₂Si(CH₃)₃), 1.9 (NSi(CH₃)₃). IR

(CsBr plates, Nujol): ν 1644 (w), 1605 (s), 1572 (m), 1402 (w),

1350 (w), 1306 (m), 1283 (m), 1156 (m), 1137 (m), 1106 (w),

1083 (s), 1036 (m), 1013 (w), 988 (w), 965 (w), 946 (w), 899

(w), 801 (w), 727 (w), 627 (s), 645 (m), 632 (m), 596 (s), 562 (s),

507 (s), 485 (w), 445 (m), 425 (m) cm^-1. Anal. Found (calcd for

C₂₀H₄₃ClN₄Si₃Zr): C, 43.5 (43.6); H, 7.7 (7.9); N, 10.2 (10.2).

t

NMR Tube Scale Synthesis of Zr(CH₂Bu)₂(N₂NN′) (5).

t

A colorless solution of Zr(CH₂Bu)₄(22 mg, 0.059 mmol) in C₆D₆

(ca. 0.75 mL) was added to H₂N₂NN′ (20 mg, 0.059 mmol),

producing an immediate orange coloration. The NMR data

were consistent with the quantitative formation of 5 and 2

equiv of CMe₄. 5 subsequently decomposed to a complex

mixture of products over 6 h.

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.38 (1 H, d, J 4.0

3

Hz, 6-C₅H₄N), 6.94 (1 H, dd, J 6.0, 8.0 Hz, 4-C₅H₄N), 6.67 (1

ZrMe(CH₂Ph)(N₂NN′) (8). To a yellow solution of ZrCl-

(CH₂Ph)(N₂NN′) (6) (206 mg, 0.37 mmol) in benzene (20 mL)

cooled to 5 °C was added MeMgBr (1.4 M in toluene/thf, 265

µL, 0.37 mmol) in benzene (5 mL). The mixture was allowed

to warm to room temperature and stirred for 16 h to give an

opaque orange-brown solution. The volatiles were removed

under reduced pressure, yielding a light brown solid. The solid

was extracted into benzene (15 mL) and filtered to give an

orange solution. The volatiles were removed under reduced

pressure, yielding 8 as a yellow solid. Yield: 162 mg (82%).

H, dd, ³J 4.0, 8.0 Hz, 5-C₅H₄N), 6.58 (1 H, d, ³J 6.0 Hz,

3-C₅H₄N), 3.98 (2 H, s, C₅H₄NCH₂), 3.94 (2 H, m, NCH₂CH₂-

NSi), 3.33 (2 H, m, NCH₂CH₂NSi), 3.00 (2 H, m, NCH₂CH₂-

NSi), 2.57 (2 H, m, NCH₂CH₂NSi), 1.33 (2 H, s, CH₂C(CH₃)₃),

1.28 (2 H, s, CH₂C(CH₃)₃), 1.15 (18 Hs, C(CH₃)₃), 0.46 (18 Hs,

Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, C₆D₆): δ 153.8

(2-C₅H₄N), 150.0 (6-C₅H₄N), 136.1 (4-C₅H₄N), 125.4 (5-C₅H₄N),

122.5 (3-C₅H₄N), 83.8 (CH₂C(CH₃)₃), 77.4 (CH₂C(CH₃)₃), 56.7

(NCH₂CH₂NSi), 48.5 (NCH₂CH₂NSi), 48.1 (C₅H₄NCH₂), 34.3

(C(CH₃)₃), 32.2 (C(CH₃)₃), 23.2 (C(CH₃)₃), 20.0 (C(CH₃)₃), 0.13

(Si(CH₃)₃).

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.60 (1 H, d, J 5.5

3

Hz, 6-C₅H₄N), 7.35 (2 H, d, J 7.0 Hz, o-C₆H₅), 7.29 (2 H, dd,

3

³J 7.0, 7.5 Hz, m-C₆H₅), 6.84 (1 H, t, J 7.5 Hz, p-C₆H₅), 6.76

ZrCl(CH₂Ph)(N₂NN′) (6). To a solution of ZrCl₂(N₂NN′) (1)

(500 mg, 1.0 mmol) in benzene (30 mL) cooled to 5 °C was

added dropwise a solution of PhCH₂MgCl (1.0 M in Et₂O, 1.0

mL, 1.0 mmol) in benzene (5 mL). The mixture immediately

turned slightly orange and was allowed to warm to room

temperature before being stirred for a further 16 h. The

volatiles were removed under reduced pressure, and the

resulting yellow solid was extracted into benzene (60 mL). The

3

(1 H, dd, J 7.5, 7.5 Hz, 4-C₅H₄N), 6.37 (1 H, dd, J 5.5, 7.5

Hz, 5-C₅H₄N), 6.29 (1 H, d, ³J 7.5 Hz, 3-C₅H₄N), 3.29 (2 H, m,

NCH₂CH₂NSi), 3.21 (2 H, s, C₆H₅CH₂), 3.08 (2 H, s, C₅H₄-

NCH₂), 2.91 (2 H, m, NCH₂CH₂NSi), 2.10 (2 H, m, NCH₂CH₂-

NSi), 1.83 (2 H, m, NCH₂CH₂NSi), 0.73 (3 H, s, ZrCH₃), 0.32

(18 H, s, Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, C₆D₆):

δ 158.6 (2-C₅H₄N), 150.6 (6-C₅H₄N), 150.2 (i-C₆H₅), 138.0 (4-

5598 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

C₅H₄N), 128.6 (o-C₆H₅), 127.7 (m-C₆H₅), 122.8 (5-C₅H₄N), 121.9

(3-C₅H₄N), 118.2 (p-C₆H₅), 63.7 (C₆H₅CH₂), 58.0 (C₅H₄NCH₂),

57.0 (NCH₂CH₂NSi), 48.3 (NCH₂CH₂NSi), 44.5 (ZrCH₃), 1.8

(Si(CH₃)₃). IR (CsBr plates, Nujol): ν 1654 (m), 1604 (s), 1304

(m), 1280 (w), 1250 (s), 1209 (s), 1174 (w), 1159 (w), 1142 (w),

1112 (w), 1082 (m), 1072 (s), 1036 (w), 1025 (w), 1010 (w), 1000

(w), 943 (s), 906 (s), 835 (s), 779 (w), 764 (w), 747 (m), 730 (w),

697 (m), 675 (w), 633 (m), 593 (w), 584 (w), 561 (w), 541 (w),

520 (w), 452 (m) cm^-1. EI-MS: m/z 441 (20%), [M - CH₂C₆H₅⁺];

425 (96%), [M - CH₂C₆H₅, H, CH₃]⁺. Anal. Found (calcd for

C₂₄H₄₂N₄Si₂Zr): C, 53.7 (54.0); H, 7.8 (7.9); N, 10.2 (10.5).

ZrCl{(2-NC₅(6-C₃H₅)H₄)CH₂N(CH₂CH₂NSiMe₃)₂} (9). To

a yellow solution of ZrCl₂(N₂NN′) (1) (194 mg, 0.39 mmol) in

benzene (5 mL) was added dropwise a solution of ClMgCH₂-

CHCH₂(2.0 M in thf, 194 µL, 0.39 mmol) in benzene (3 mL).

After stirring for 75 min the mixture had become cloudy and

brown-orange in color. The volatiles were removed under

reduced pressure, and the resulting brown oil was extracted

into pentane (30 mL). The extract was filtered and the volatiles

were removed under reduced pressure to give analytically pure

9 as a yellow oil, which could not be crystallized. Yield: 145

mg (74%).

3.2 (SiCH₃), 0.8 (Si(CH₃)₃). ¹⁹F NMR (470.4 MHz, 293 K, CD₂-

3

Cl₂): δ -133.4 (6 F, d, J 21.4 Hz, o-C₆F₅), -165.2 (3 F, t, J

21.4 Hz, p-C₆F₅), -167.9 (6 F, dd, ³J 21.4 Hz, m-C₆F₅). ¹¹B NMR

(160.4 MHz, 293 K, CD₂Cl₂): δ -14.73 ([MeB(C₆F₅)₃]^-). IR

(CsBr plates, Nujol): ν 1641 (m), 1610 (m), 1510 (s), 1304 (w),

1260 (m), 1086 (s), 1054 (w), 1040 (w), 1018 (w), 995 (w), 979

(w), 966 (w), 952 (w), 936 (w), 922 (w), 876 (w), 840 (s), 766

(w), 748 (w), 724 (w), 685 (w), 660 (w), 647 (w), 619 (w), 604

(w), 588 (w), 570 (w), 541 (w), 522 (w), 474 (w), 430 (w) cm^-1

.

Anal. Found (calcd for C₃₅H₃₄BF₁₅N₄Si₂Zr): C, 44.7 (44.1); H,

4.0 (3.6); N, 5.7 (5.9); B, 1.1 (1.1).

[ZrMe(THF)(N₂NN′)][MeBAr^F₃] (12-MeBAr^F₃). To a col-

orless solution of ZrMe₂(N₂NN′) (2) (111 mg, 0.24 mmol) and

THF (ca. 0.5 mL) in benzene (5 mL) was added a solution of

BAr^F₃(124 mg, 24 mmol) in benzene (10 mL), resulting in the

immediate formation of an orange-brown solution. The mixture

was stirred for 15 min, after which time the volatiles were

removed under reduced pressure, yielding 12-MeBAr^Fas a

3

brown oil, which could not be crystallized. Yield: 247 mg (98%).

¹H NMR (300.0 MHz, 293 K, CD₂Cl₂): δ 8.84 (1 H, d, ³J 6.6

3

Hz, 6-C₅H₄N), 8.04 (1 H, dd, J 7.8, 7.5 Hz, 4-C₅H₄N), 7.55 (2

H, m, 3-C₅H₄N, 5-C₅H₄N), 4.31 (4 H, br s, 2,5-C₄H₈O), 4.13 (2

H, s, C₅H₄NCH₂), 3.76 (2 H, m, NCH₂CH₂NSi), 3.37 (4 H, m,

NCH₂CH₂NSi, NCH₂CH₂NSi), 2.85 (2 H, m, NCH₂CH₂NSi),

2.18 (3 H, br s, 3,4-C₄H₈O), 1.92 (1 H, br s, 3,4-C₄H₈O), 0.52 (3

H, s, ZrCH₃), 0.48 (3 H, br s, BCH₃), 0.0518 H, s, Si(CH₃)₃).

¹³C{¹H} NMR (75.5 MHz, 293 K, CD₂Cl₂): δ 159.4 (2-C₅H₄N),

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 6.06 (1 H, m, C₅H₄-

3

(CH₂CHCH₂)N), 6.02 (1 H, dd, J ) 5.4, 8.8 Hz, 4-C₅H₄(CH₂-

CHCH₂)N), 5.36 (1 H, m, ³J ) 8.8, 5.9 Hz, 5-C₅H₄(CH₂-

CHCH₂)N), 5.20 (1 H, m, C₅H₄(CH₂CHCH₂)N), 5.05 (1 H, m,

6-C₅H₄(CH₂CHCH₂)N), 4.98 (1 H, m, C₅H₄(CH₂CHCH₂)N), 4.79

(1 H, d, ³J ) 5.4 Hz, 3-C₅H₄(CH₂CHCH₂)N), 3.38 (2 H, m,

NCH₂CH₂NSi), 3.12 (1 H, d, ²J ) 13.2 Hz, C₅H₄(CH₂CHCH₂)-

1

151.4 (6-C₅H₄N), 148.7 (o-C₆F₅, J 228 Hz), 141.8 (4-C₅H₄N),

137.7 (p-C₆F₅, ¹J 238 Hz), 137.0 (m-C₆F₅, ¹J 238 Hz), 125.1

(5-C₅H₄N), 124.6 (3-C₅H₄N), 74.6 (2,5-C₄H₈O), 58.1 (NCH₂CH₂-

NSi), 56.5 (C₅H₄NCH₂), 49.4 (NCH₂CH₂NSi), 48.0 (3,4-C₄H₈O),

25.8 (ZrCH₃), 10.6 (BCH₃), 0.9 (Si(CH₃)₃). ¹⁹F NMR (282.3 MHz,

293 K, CD₂Cl₂): δ -133.6 (6 F, d, ³J 21.5 Hz, o-C₆F₅), -165.6

2

NCH₂), 2.85 (2 H, m, NCH₂CH₂NSi), 2.78 (1 H, d, J ) 13.2

Hz, C₅H₄(CH₂CHCH₂)NCH₂), 2.47 (3 H, m, NCH₂CH₂NSi,

C₅H₄(CH₂CHCH₂)N), 2.10 (3 H, m, NCH₂CH₂NSi, C₅H₄(CH₂-

CHCH₂)N), 0.33 (9 H, s, Si(CH₃)₃), 0.29 (9 H, s, Si(CH₃)₃). ¹³C-

{¹H} NMR (75.5 MHz, 293 K, C₆D₆): δ 148.1 (2-C₅H₄(CH₂-

CHCH₂)N), 136.4 (C₅H₄(CH₂CHCH₂)N), 123.2 (4-C₅H₄(CH₂-

CHCH₂)N), 118.9 (5-C₅H₄(CH₂CHCH₂)N), 117.5 (C₅H₄(CH₂CHC-

H₂)N), 95.5 (3-C₅H₄(CH₂CHCH₂)N), 60.1 (C₅H₄(CH₂CHCH₂)-

NCH₂), 60.1 (NCH₂CH₂NSi), 59.5 (NCH₂CH₂NSi), 58.0 (6-

C₅H₄(CH₂CHCH₂)N), 48.0 (NCH₂CH₂NSi), 47.7 (NCH₂CH₂NSi),

40.8 (C₅H₄(CH₂CHCH₂)N), 1.5 (Si(CH₃)₃), 1.3 (Si(CH₃)₃). IR

(CsBr plates): ν 3072 (w), 3036 (w), 2951 (s), 2900 (w), 2854

(m), 1634 (m), 1607 (m), 1560 (s), 1465 (w), 1445 (m), 1407

(m), 1374 (m), 1354 (w), 1308 (m), 1247 (s), 1201 (w), 1157

(w), 1122 (w), 1072 (m), 1022 (w), 992 (m), 916 (s), 869 (w),

836 (m), 807 (w), 758 (w), 747 (m), 706 (w), 680 (m), 624 (w),

599 (w), 570 (w), 450 (w) cm^-1. EI-MS: m/z 502 (15%) [M]⁺;

429 (29%) [M - Si(CH₃)₃]⁺. Anal. Found (calcd for C₁₉H₃₉ClN₄-

Si₂Zr): C, 46.3 (45.3); H, 7.0 (7.4); N, 11.3 (11.1).

3

(3 F, t, J 21.7 Hz, p-C₆F₅), -168.2 (6 F, m, J 21.7, 21.5 Hz,

m-C₆F₅). ¹¹B NMR (96.3 MHz, 293 K, CD₂Cl₂): δ -14.9

([MeBAr^F₃]^-). IR (CsBr plates, Nujol): ν 2613 (w), 2588 (w),

2538 (w), 2082 (w), 2006 (w), 1933 (w), 1871 (w), 1641 (s), 1611

(s), 1572 (m), 1554 (w), 1515 (m), 1505 (w), 1306 (m), 1261 (s),

1163 (m), 1142 (m), 1099 (s), 1044 (w), 898 (w), 802 (w), 780

(w), 687 (m), 661 (s), 647 (w), 602 (s), 568 (s), 529 (w), 459 (s),

436 (w), 423 (w) cm^-1. Anal. Found (calcd for C₄₀H₄₆BF₁₅N₄-

OSi₂Zr‚0.3C₆H₆): C, 46.9 (47.2); H, 4.8 (4.5); N, 5.1 (5.3).

[ZrCl(N₂NN′)][PhCH₂BAr^F₃] (13-PhCH₂BAr^F₃). To a yel-

low suspension of ZrCl(CH₂Ph)(N₂NN′) (6) (426 mg, 0.77 mmol)

in benzene (15 mL) cooled to 5 °C was added dropwise a

solution of BAr^F(393 mg, 0.77 mmol) in benzene (15 mL),

3

resulting immediately in a loss of color intensity of the solution.

The solution was stirred for 10 min, after which time the

volatiles were removed under reduced pressure from the

[Zr{(2-NC₅H₄)CH₂N(CH₂CH₂NSiMe₃)(CH₂CH₂NSiMe-

₂CH₂-)}][MeBAr^F₃] (10-MeBAr^F₃). To a solution of ZrMe₂(N₂-

NN′) (2) (187 mg, 0.41 mmol) in benzene (5 mL) was added

BAr^F₃in benzene (5 mL), resulting in the immediate formation

of a red oil. The oil was isolated, washed with benzene (3 × 5

mL), and dried in vacuo to afford 10-MeBAr^F₃as a white solid.

Yield: 235 mg (60%).

mixture (cooled to freezing), yielding 13-PhCH₂BAr^Fas a

3

white solid. Yield: 769 mg (94%).

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 9.19 (1 H, d, ³J 5.5

3

Hz, 6-C₅H₄N), 8.16 (1 H, dd, J 8.5, 7.5 Hz, 4-C₅H₄N), 7.66 (1

H, dd, ³J 8.5, 5.5 Hz, 5-C₅H₄N), 7.57 (1 H, d, ³J 7.5 Hz,

3

3-C₅H₄N), 6.97 (2 H, dd, J 7.0, 7.5 Hz, m-C₆H₅), 6.87 (1 H, t,

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 9.20 (1 H, d, ³J 6.0

³J 7.5 Hz, p-C₆H₅), 6.84 (2 H, d, ³J 7.0 Hz, o-C₆H₅), 4.20 (2 H,

s, C₅H₄NCH₂), 3.91 (2 H, m, NCH₂CH₂NSi), 3.60 (2 H, m,

NCH₂CH₂NSi), 3.50 (2 H, m, NCH₂CH₂NSi), 3.01 (2 H, m,

NCH₂CH₂NSi), 2.89 (2 H, br s, C₆H₅CH₂), 0.27 (18, H, s, Si-

(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, CD₂Cl₂): δ 159.2

3

Hz, 6-C₅H₄N), 8.24 (1 H, dd, J 8.0, 7.5 Hz, 4-C₅H₄N), 7.76 (1

H, dd, ³J 7.5, 6.0 Hz, 5-C₅H₄N), 7.69 (1 H, d, ³J 8.0 Hz,

3-C₅H₄N), 4.32 (2 H, s, C₅H₄NCH₂), 3.93 (1 H, m, NCH₂CH₂-

NSi), 3.79 (1 H, m, NCH₂CH₂NSi), 3.79 (1 H, m, NCH₂CH₂-

NSi), 3.61 (1 H, m, NCH₂CH₂NSi), 3.54 (1 H, m, NCH₂CH₂-

NSi), 3.32 (1 H, m, NCH₂CH₂NSi), 3.24 (1 H, m, NCH₂CH₂NSi),

3.02 (1 H, m, NCH₂CH₂NSi), 1.39 (1 H, d, ²J ) 15.5 Hz, ZrCH₂),

1.10 (1 H, d, ²J ) 15.5 Hz, ZrCH₂), 0.44 (3 H, br s, BCH₃),

0.43 (3 H, s, Si(CH₃)₂), 0.00 (3 H, s, Si(CH₃)₂), -0.02 (9 H, s,

Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, CD₂Cl₂): δ 159.3

1

(2-C₅H₄N), 152.4 (i-C₆H₅), 149.0 (6-C₅H₄N), 148.6 (o-C₆F₅, J

226 Hz), 144.3 (4-C₅H₄N), 138.0 (p-C₆F₅, ¹J 245 Hz), 136.8 (m-

C₆F₅, ¹J 237 Hz), 129.1 (o-C₆H₅), 127.2 (m-C₆H₅), 126.2

(5-C₅H₄N), 125.2 (3-C₅H₄N), 122.8 (p-C₆H₅), 60.2 (NCH₂CH₂-

NSi), 59.4 (C₅H₄NCH₂), 49.2 (NCH₂CH₂NSi), 32.0 (C₆H₅CH₂),

0.6 (Si(CH₃)₃). ¹⁹F NMR (282.3 MHz, 293 K, CD₂Cl₂): δ -131.5

(6 F, d, ³J 20.3 Hz, o-C₆F₅), -165.0 (3 F, t, ³J 20.0 Hz, p-C₆F₅),

-167.9 (6 F, m, ³J 20.3, 20.0 Hz, m-C₆F₅). ¹¹B NMR (160.4

MHz, 293 K, CD₂Cl₂): δ -10.51 ([PhCH₂B(C₆F₅)₃]^-). IR (CsBr

plates, Nujol): ν 1641 (w), 1612 (w), 1511 (m), 1307 (w), 1259

(m), 1213 (w), 1082 (m), 1026 (w), 982 (m), 930 (w), 894 (w),

1

(2-C₅H₄N), 152.5 (6-C₅H₄N), 148.7 (o-C₆F₅, J 234 Hz), 143.7

(4-C₅H₄N), 137.8 (p-C₆F₅, ¹J 248 Hz), 136.8 (m-C₆F₅, ¹J 264

Hz), 126.2 (5-C₅H₄N), 124.8 (3-C₅H₄N), 60.0 (NCH₂CH₂NSi),

59.5 (ZrCH₂), 58.7 (C₅H₄NCH₂), 56.1 (NCH₂CH₂NSi), 52.6

(NCH₂CH₂NSi), 45.0 (NCH₂CH₂NSi), 10.3 (BCH₃), 7.6 (SiCH₃),

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5599

840 (m), 800 (w), 755 (w), 723 (w), 704 (w), 681 (w), 651 (w),

634 (w), 606 (w), 570 (w), 550 (w), 528 (w) cm^-1. Anal. Found

(calcd for C₄₁H₃₉BClF₁₅N₄Si₂Zr): C, 46.0 (46.2); H, 3.8 (3.7);

N, 5.3 (5.3).

resulting brown solid was washed with CH₂Cl₂(3 × 5 mL),

giving 16 as an orange solid. Yield: 55 mg (27%).

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 9.18 (1 H, d, ³J 5.0

3

Hz, 6-C₅H₄N), 8.00 (1 H, dd, J 7.5, 7.0 Hz, 4-C₅H₄N), 7.49 (1

H, d, ³J 7.5 Hz, 3-C₅H₄N), 7.45 (1 H, dd, ³J 5.0, 7.0 Hz,

5-C₅H₄N), 6.87 (2 H, d, ³J 7.5 Hz, m-C₆H₃), 6.46 (1 H, t, ³J 7.5

Hz, p-C₆H₃), 4.14 (2 H, s, C₅H₄NCH₂), 4.06 (2 H, m, ³J 6.8 Hz,

CH(CH₃)₂), 3.68 (2 H, m, NCH₂CH₂NSi), 3.41 (2 H, m,

NCH₂CH₂NSi), 3.18 (2 H, m, NCH₂CH₂NSi), 2.68 (2 H, m,

Ti(N^tBu)(N₂NN′) (14). To a solution of Li₂N₂NN′ (339 mg,

0.97 mmol) in benzene (30 mL) cooled to 5 °C was added a

solution of Ti(N^tBu)Cl₂(py)₃(368 mg, 0.83 mmol) in benzene

(20 mL). The mixture was allowed to warm to room temper-

ature and stirred for a further 90 min. The volatiles were

removed under reduced pressure, leaving an orange-red solid,

which was extracted into pentane (40 mL). The resulting red

solution was filtered and concentrated to 20 mL, at which point

the formation of a yellow crystalline solid began. The mixture

was cooled to -30 °C for 2 days, and the resulting yellow solid

was isolated and dried in vacuo affording 14. Yield: 232 mg

(61%).

3

NCH₂CH₂NSi), 1.08 (12 H, d, J 6.8 Hz, CH(CH₃)₂), 0.06 (18

H, s, Si(CH₃)₃). The compound was too insoluble to obtain ¹³

C

NMR data. IR (CsBr plates, Nujol): ν 1607 (m), 1580 (w), 1568

(w), 1416 (m), 1338 (m), 1277 (w), 1255 (w), 1241 (w), 1161

(w), 1139 (w), 1108 (w), 1098 (w), 1071 (m), 1053 (w), 1029

(w), 1000 (w), 926 (s), 869 (m), 836 (s), 797 (m), 754 (m), 724

(w), 680 (w), 649 (w), 635 (w), 624 (w), 606 (w), 587 (m), 543

(m), 454 (w), 430 (m) cm^-1. EI-MS: m/z 571 (18%), [M -

2CH₃]⁺; 557 (10%), [M - CH(CH₃)₂, H]⁺; 543 (20%), [M - CH₃,

CH(CH₃)₂]⁺; 515 (18%), [M - 2 CH(CH₃)₂]⁺. Anal. Found (calcd

for C₂₈H₄₉N₅Si₂Zr): C, 55.5 (55.8); H, 7.9 (8.2); N, 10.9 (11.6).

Zr(NH^tBu)₂(N₂NN′) (17). To a yellow solution of ZrCl₂(N₂-

NN′) (6) (219 mg, 0.44 mmol) in benzene (20 mL) was added

a colorless solution of LiNH^tBu in benzene (20 mL). The

mixture was stirred at room temperature for 6 h, after which

time the mixture attained an orange-red color and a small

amount of precipitate formed. After filtering, the solid was

washed with benzene (2 × 5 mL), and the volatiles of the

combined filtrates were removed under reduced pressure. The

resulting solid was triturated with pentane to give 17 as an

orange-red solid. Yield: 122 mg (49%).

3

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 9.68 (1 H, d, J 5.5

3

Hz, 6-C₅H₄N), 6.71 (1 H, dd, J 7.7, 7.7 Hz, 4-C₅H₄N), 6.42 (1

H, dd, ³J 5.5, 7.7 Hz, 5-C₅H₄N), 6.12 (1 H, d, ³J 7.7 Hz,

3-C₅H₄N), 3.64 (2 H, m, NCH₂CH₂NSi), 3.38 (2 H, m, NCH₂CH₂-

NSi), 2.97 (2 H, s, C₅H₄NCH₂), 2.47 (2 H, m, NCH₂CH₂NSi),

1.98 (2 H, m, NCH₂CH₂NSi), 1.69 (9 H, s, C(CH₃)₃), 0.69 (18

H, s, Si(CH₃)₃). ¹³C{¹H} NMR (75.5 MHz, 293 K, C₆D₆): δ 159.9

(2-C₅H₄N), 155.7 (6-C₅H₄N), 139.3 (4-C₅H₄N), 122.1 (5-C₅H₄N),

122.1 (3-C₅H₄N), 65.4 (C(CH₃)₃), 57.0 (C₅H₄NCH₂), 56.2 (NCH₂-

CH₂NSi), 49.1 (NCH₂CH₂NSi), 34.8 (C(CH₃)₃), 4.4 (Si(CH₃)₃).

IR (CsBr plates, Nujol): ν 1608 (m), 1571 (w), 1299 (w), 1235

(m), 1155 (w), 1096 (m), 1042 (w), 1018 (w), 937 (m), 836 (m),

757 (m), 682 (w), 592 (m), 552 (w), 531 (m), 457 (m) cm^-1. EI-

MS: m/z 455 (11%), [M]⁺; 440 (25%), [M - CH₃]⁺. Anal. Found

(calcd for C₂₀H₄₁N₅Si₂Ti): C, 52.5 (52.7); H, 8.9 (9.1); N, 15.0

(15.4).

3

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 8.89 (1 H, d, J 5.4

3

Hz, 6-C₅H₄N), 6.82 (1 H, dd, J 7.8, 7.5 Hz, 4-C₅H₄N), 6.49 (1

H, dd, ³J 5.4, 7.5 Hz, 5-C₅H₄N), 6.30 (1 H, d, ³J 7.8 Hz,

3-C₅H₄N), 5.22 (1 H, br s, NH), 4.22 (1 H, br s, NH), 3.67 (2 H,

m, NCH₂CH₂NSi), 3.27 (2 H, s, C₅H₄NCH₂), 3.17 (2 H, m,

NCH₂CH₂NSi), 3.09 (2 H, m, NCH₂CH₂NSi), 2.13 (2 H, m,

NCH₂CH₂NSi), 1.68 (9 H, s, C(CH₃)₃), 1.50 (9 H, s, C(CH₃)₃),

0.16 (18 H, s, Si(CH₃)₃). ¹³C{¹H} NMR (75.5 MHz, 293 K,

C₆D₆): δ 158.8 (2-C₅H₄N), 149.2 (6-C₅H₄N), 137.8 (4-C₅H₄N),

122.5 (5-C₅H₄N), 122.5 (3-C₅H₄N), 59.8 (C₅H₄NCH₂), 58.0

(NCH₂CH₂NSi), 54.7 (C(CH₃)₃), 54.4 (C(CH₃)₃), 46.2 (NCH₂CH₂-

NSi), 35.9 (C(CH₃)₃), 35.1 (C(CH₃)₃), 1.5 (Si(CH₃)₃). IR (CsBr

plates, Nujol): ν 1604 (m), 1572 (w), 1364 (m), 1307 (w), 1254

(w), 1240 (m), 1214 (m), 1154 (w), 1065 (m), 985 (w), 967 (w),

944 (w), 910 (m), 897 (m), 832 (s), 774 (w), 756 (m), 726 (w),

677 (w), 584 (w) cm^-1. EI-MS: m/z 523 (5%), [M - 3 CH₃, H]⁺;

497 (3%), [M - Si(CH₃)₃]⁺. A satisfactory elemental analysis

could not be obtained.

i

Ti(NAr)(N₂NN′) (15). To a mixture of solid Ti(N-2,6-C₆H₃-

Pr₂)Cl₂(py)₃(298 mg, 0.56 mmol) and Li₂N₂NN′ (197 mg, 0.56

mmol) cooled to -78 °C was added benzene (10 mL). The

mixture was allowed to warm to room temperature and stirred

for a further 12 h. The volatiles were removed under reduced

pressure, and the resulting orange solid was extracted into

CH₂Cl₂(ca. 30 mL). The orange solution was filtered, and the

volatiles were removed under reduced pressure to yield 15 as

a red-orange solid. Yield: 183 mg (58%).

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 9.23 (1 H, d, ³J 5.5

3

Hz, 6-C₅H₄N), 7.88 (1 H, dd, J 6.5, 7.5 Hz, 4-C₅H₄N), 7.38 (1

H, d, ³J 6.5 Hz, 3-C₅H₄N), 7.34 (1 H, dd, ³J 5.5, 7.5 Hz,

5-C₅H₄N), 7.00 (2 H, d, ³J 7.5 Hz, m-C₆H₃), 6.70 (1 H, t, ³J 7.5

3

Hz, p-C₆H₃), 4.12 (2 H, m, J 7.0 Hz, CH(CH₃)₂), 4.10 (2 H, s,

C₅H₄NCH₂), 3.77 (2 H, m, NCH₂CH₂NSi), 3.50 (2 H, m,

NCH₂CH₂NSi), 3.10 (2 H, m, NCH₂CH₂NSi), 2.69 (2 H, m,

Zr(N^tBu)(py)(N₂NN′) (18). To a yellow solution of ZrCl₂(N₂-

NN′) (1) (241 mg, 0.48 mmol) in benzene (10 mL) was added

2 equiv of LiCH₂SiMe₃(91 mg, 0.97 mmol) in benzene (5 mL).

The mixture was stirred for 5 min, after which time pyridine

3

NCH₂CH₂NSi), 1.15 (12 H, d, J 7.0 Hz, CH(CH₃)₂), 0.22 (18

H, s, Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K, CD₂Cl₂): δ

159.5 (2-C₅H₄N), 154.8 (6-C₅H₄N), 143.0 (o-C₆H₃), 140.6 (4-

C₅H₄N), 123.7 (5-C₅H₄N), 122.8 (3-C₅H₄N), 122.8 (m-C₆H₃),

117.6 (p-C₆H₃), 59.6 (NCH₂CH₂NSi), 59.5 (C₅H₄NCH₂), 48.3

(NCH₂CH₂NSi), 27.5 (CH(CH₃)₂), 24.9 (CH(CH₃)₂), 2.3 (Si-

(CH₃)₃). IR (CsBr plates, Nujol): ν 1608 (m), 1417 (m), 1328

(m), 1269 (m), 1241 (m), 1161 (w), 1141 (w), 1069 (w), 1032

(w), 1020 (w), 957 (w), 933 (s), 893 (w), 873 (m), 837 (s), 804

(m), 758 (m), 682 (w), 593 (w), 553 (w) cm^-1. EI-MS: m/z 559

(30%), [M]⁺; 544 (10%), [M - CH₃]⁺; 384 (65%), [M - NAr]⁺.

Anal. Found (calcd for C₂₈H₄₉N₅Si₂Ti): C, 59.8 (60.1); H, 8.4

(8.8); N, 12.2 (12.5).

t

(1 mL) and a solution of BuNH₂(31.8 mg, 0.43 mmol) in

benzene (5 mL) was added. The mixture was stirred for 6 h

before the volatiles were removed under reduced pressure,

yielding a dark red product, which was subsequently extracted

into pentane (2 × 15 mL). The red pentane solution was

filtered, concentrated to ca. 5 mL, and then cooled to -30 °C,

resulting in the formation of a dark red solid, which was

isolated and dried in vacuo, affording 18. Yield: 183 mg (73%).

3

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 9.86 (1 H, d, J 5.4

Hz, 6-C₅H₄N), 9.16 (2 H, br m, o-C₅H₅N), 6.91 (1 H, tt,

p-C₅H₅N), 6.81 (1 H, td, ³J 7.8, 7.8 Hz, 4-C₅H₄N), 6.72 (2 H, t,

m-C₅H₅N), 6.55 (1 H, t, ³J 5.4, 7.8 Hz, 5-C₅H₄N), 6.28 (1 H, d,

³J 7.8 Hz, 3-C₅H₄N), 3.33 (4 H, m, NCH₂CH₂NSi), 3.26 (2 H,

s, C₅H₄NCH₂), 2.55 (2 H, m, NCH₂CH₂NSi), 2.08 (2 H, m,

NCH₂CH₂NSi), 1.60 (9 H, s, C(CH₃)₃), 0.52 (18 H, s, Si(CH₃)₃).

¹³C{¹H} NMR (75.5 MHz, 293 K, C₆D₆): δ 159.1 (2-C₅H₄N),

155.4 (6-C₅H₄N), 152.2 (o-C₅H₅N), 138.2 (4-C₅H₄N), 137.1 (p-

C₅H₅N), 123.6 (m-C₅H₅N), 121.8 (5-C₅H₄N), 121.5 (3-C₅H₄N),

60.6 (C(CH₃)₃), 57.9 (C₅H₄NCH₂, NCH₂CH₂NSi), 46.9 (NCH₂-

Zr(NAr)(N₂NN′) (16). To a yellow solution of ZrCl₂(N₂NN′)

(1) (163 mg, 0.33 mmol) in benzene (10 mL) was added

dropwise a solution of LiCH₂SiMe₃(62 mg, 0.65 mmol) in

benzene (10 mL). After complete addition the resulting opaque

orange mixture was stirred for 5 min before being filtered. A

solution of ArNH₂(58 mg, 62 µL, 0.33 mmol) in benzene (5

mL) was added to the solution and the mixture stirred at room

temperature for 20 h to give a brown opaque mixture. The

volatiles were removed under reduced pressure, and the

5600 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

CH₂NSi), 36.0 (C(CH₃)₃), 3.8 (Si(CH₃)₃). IR (CsBr plates,

Nujol): ν 1603 (s), 1571 (m), 1341 (w), 1305 (m), 1341 (s), 1214

(w), 1153 (m), 1133 (w), 1085 (w), 1069 (w), 1049 (w), 1037

(w), 1019 (w), 1011 (w), 993 (w), 969 (w), 942 (w), 919 (w), 899

(w), 834 (s), 754 (m), 726 (w), 701 (m), 676 (m), 628 (m), 612

(w), 578 (w), 558 (m), 522 (w), 508 (w), 483 (w), 443 (m), 421

(w), 403 (w) cm^-1. EI-MS: m/z 576 (27%), [M]⁺; 505 (10%), [M

- NC(CH₃)₃]⁺. Anal. Found (calcd for C₂₅H₄₆N₆Si₂Zr): C, 51.8

(51.9); H, 8.4 (8.0); N, 14.9 (14.5).

463 (11%), [M - CH₃, C(CH₃)₃]⁺. Anal. Found (calcd for C₂₀H₄₁-

ClN₅NbSi₂): C, 44.4 (44.8); H, 7.3 (7.7); N, 12.7 (13.1).

Ta(N^tBu)Cl(N₂NN′) (21). To a green-yellow solution of Ta-

(N^tBu)Cl₃(py)₂(430 mg, 0.83 mmol) in benzene (20 mL) cooled

to 5 °C was added a solution of Li₂N₂NN′ (291 mg, 0.83 mmol)

in benzene (20 mL). The reaction was allowed to warm to room

temperature and stirred for a further 16 h, giving an orange-

brown opaque mixture. The volatiles were removed under

reduced pressure, and the resulting solid was extracted into

pentane. The solution was filtered and concentrated to ca. 5

mL, and upon cooling to -30 °C, a brown crystalline solid

formed. This was isolated and dried in vacuo to afford 21.

Yield: 150 mg (29%).

Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19). To a yellow solution of

ZrCl₂(N₂NN′) (1) (208 mg, 0.42 mmol) in benzene (5 mL) was

added a colorless solution of LiCH₂SiMe₃(65 mg, 0.83 mmol)

in benzene (5 mL), resulting in the formation of a precipitate

and an orange solution. The mixture was allowed to stir for

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 9.00 (1 H, d, J 5.0,

t

3

15 min before a solution of BuNH₂(30 mg, 0.42 mmol) and

Hz, 6-C₅H₄N), 6.71 (1 H, dd, J 8.0, 7.5 Hz, 4-C₅H₄N), 6.34 (1

H, dd, ³J 5.0, 7.5 Hz, 5-C₅H₄N), 6.26 (1 H, d, ³J 8.0 Hz,

piperidine (200 mg, 2.3 mmol) in pyridine (5 mL) was added

dropwise. After complete addition the solution darkened while

becoming clear. The solution was stirred for 4 h, after which

time the volatiles were removed under reduced pressure and

the resulting brown product was extracted into pentane (30

mL). After filtering, the red pentane solution was concentrated

to 5 mL and cooled to -30 °C, resulting in the formation of 19

as a red, crystalline solid. Yield: 127 mg (52%).

2

3-C₅H₄N), 4.64 (1 H, d, J 15.1 Hz, C₅H₄NCH₂), 3.86 (1 H, m,

NCH₂CH₂NSi), 3.80 (1 H, m, NCH₂CH₂NSi), 3.61 (1 H, m,

2

NCH₂CH₂NSi), 3.35 (1 H, m, NCH₂CH₂NSi), 2.90 (1 H, d, J

15.1 Hz, C₅H₄NCH₂), 2.80 (1 H, m, NCH₂CH₂NSi), 2.29 (1 H,

m, NCH₂CH₂NSi), 2.19 (1 H, m, NCH₂CH₂NSi), 1.99 (1 H, m,

NCH₂CH₂NSi), 1.74 (9 H, s, C(CH₃)₃), 0.59 (9 H, s, Si(CH₃)₃),

0.32 (9 H, s, Si(CH₃)₃). ¹³C{¹H} NMR (125.7 MHz, 293 K,

C₆D₆): δ 160.3 (2-C₅H₄N), 150.8 (6-C₅H₄N), 137.7 (4-C₅H₄N),

122.3 (5-C₅H₄N), 121.5 (3-C₅H₄N), 65.1 (C(CH₃)₃), 64.9 (C₅H₄N-

CH₂), 60.5 (NCH₂CH₂NSi), 59.8 (NCH₂CH₂NSi), 52.2 (NCH₂-

CH₂NSi), 49.1 (NCH₂CH₂NSi), 34.1 (C(CH₃)₃), 3.4 (Si(CH₃)₃),

3.2 (Si(CH₃)₃). IR (CsBr plates, Nujol): ν 1610 (s), 1571 (w),

1355 (m), 1294 (w), 1250 (m), 1212 (w), 1158 (m), 1141 (w),

1132 (w), 1110 (w), 1077 (m), 1055 (w), 1033 (m), 1023 (m),

936 (m), 868 (m), 839 (m), 789 (w), 760 (w), 726 (m), 686 (m),

650 (m), 634 (m), 589 (m), 551 (m), 527 (m), 470 (w) cm^-1. EI-

MS: m/z 623 (58%), [M]⁺; 608 (57%), [M - CH₃]⁺; 552 (11%),

[M - NC(CH₃)₃]⁺; 521 (95%), [M - N^tBu, 2 CH₃, H]⁺. Anal.

Found (calcd for C₂₀H₄₁ClN₅Si₂Ta): C, 38.4 (38.5); H, 6.6 (6.6);

N, 11.0 (11.2).

3

¹H NMR (300.1 MHz, 298 K, C₆D₆): δ 8.78 (1 H, d, J 5.1

3

Hz, 6-C₅H₄N), 6.75 (1 H, td, J 8.1, 8.2 Hz, 4-C₅H₄N), 6.41 (1

H, td, ³J 5.1, 8.2 Hz, 5-C₅H₄N), 6.22 (1 H, d, ³J 8.1 Hz,

3-C₅H₄N), 4.22 (1 H, br s, NH), 3.93 (4 H, br m, 2,6-NC₅H₁₀),

3.67 (2 H, m, NCH₂CH₂NSi), 3.20 (2 H, s, C₅H₄NCH₂), 3.11 (4

H, m, NCH₂CH₂NSi, NCH₂CH₂NSi), 2.09 (2 H, m, NCH₂CH₂-

NSi), 1.67 (6 H, br m, 3,4,5-NC₅H₁₀), 1.61 (9 H, s, C(CH₃)₃),

0.12 (18 H, s, Si(CH₃)₃). ¹³C{¹H} NMR data (75.5 MHz, 298 K,

C₆D₆): δ 158.9 (2-C₅H₄N), 149.2 (6-C₅H₄N), 137.7 (4-C₅H₄N),

122.6 (5-C₅H₄N), 122.4 (3-C₅H₄N), 59.3 (C₅H₄NCH₂), 57.4

(NCH₂CH₂NSi), 57.0 (2,6-NC₅H₁₀), 56.9 (NCH₂CH₂NSi), 44.8

(C(CH₃)₃), 35.8 (C(CH₃)₃), 31.0 (4-NC₅H₁₀), 27.0 (3,5-NC₅H₁₀),

2.4 (Si(CH₃)₃). IR (CsBr plates, Nujol): ν 1645 (w), 1604 (s),

1571 (m), 1422 (w), 1358 (m), 1305 (m), 1254 (w), 1239 (w),

1202 (m), 1167 (w), 1155 (w), 1148 (w), 1129 (w), 1093 (m),

1078 (w), 1063 (w), 1041 (w), 1027 (w), 1011 (w), 995 (m), 969

(m), 942 (w), 911 (w), 775 (m), 756 (w), 741 (w), 726 (w), 676

(m), 666 (m), 633 (w), 622 (s), 584 (m), 564 (s), 493 (s), 468

(w), 448 (m), 420 (w), 406 (m) cm^-1. EI-MS: m/z 582 (6%), [M]⁺;

510 (2%), [M - NH^tBu]⁺. Anal. Found (calcd for C₂₅H₅₂N₆Si₂-

Zr): C, 51.6 (51.4); H, 9.1 (9.0); N, 14.7 (14.4).

H₂O₂NN′ (22). 2-Aminomethylpyridine (5.0 g, 46.2 mmol)

was added dropwise to isobutylene oxide (9.84 g, 136.7 mmol)

with stirring in a thick-walled Teflon valve ampule. A catalytic

amount of ethanol (3 mL) was added to the resulting yellow

solution, which was frozen using liquid nitrogen and the

headspace evacuated. The solution was stirred at 75 °C for 5

days. The volatiles were removed under reduced pressure to

give a dark brown solid (13 g), which was purified in 5 g

portions by column chromatography on silica (250 g, elution

gradient CH₂Cl₂/EtOH, 100:0 to 95:5). Final purification was

achieved by sublimation (80-100 °C, 0.5-1 × 10^-6mbar) to

give 22 as a white powder. Yield: 5.50 g (47%).

Nb(N^tBu)Cl(N₂NN′) (20). To a yellow solution of Nb(N^t-

Bu)Cl₃(py)₂(326 mg, 0.71 mmol) in benzene (30 mL) was added

dropwise a solution of Li₂N₂NN′ (250 mg, 0.71 mmol) in

benzene (40 mL), immediately resulting in a darkening of the

coloration. The solution was stirred for 16 h, after which time

the volatiles were removed under reduced pressure, yielding

an orange-brown solid. The remaining solid was extracted into

pentane (40 mL), filtered, concentrated to ca. 10 mL, and

cooled to -80 °C to give 20 as a yellow solid. Yield: 114 mg

(30%).

¹H NMR (300.1 MHz, 183 K, CD₂Cl₂): δ 8.48 (1 H, d, ³J 4.0

Hz, 6-C₅H₄N), 7.66 (1 H, app.t, app.³J 9.0 Hz, 4-C₅H₄N), 7.37

3

(1 H, d, J 7.0 Hz, 3-C₅H₄N), 7.16 (1 H, app t, app.³J 6.0 Hz,

5-C₅H₄N), 6.53 (2 H, br s, NCH₂CMe₂OH), 3.95 (2 H, s,

NCH₂C₅H₄N), 2.65 (4 H, br s, NCH₂CMe₂OH), 1.16 (6 H, s,

NCH₂CMe₂OH (“b”)), 0.96 (6 H, s, NCH₂CMe₂OH (“a”)). ¹³C-

{¹H} NMR (75.5 MHz, 183 K, CD₂Cl₂): δ 159.0 (2-C₅H₄N),

147.8 (6-C₅H₄N), 135.9 (4-C₅H₄N), 121.7 (3-C₅H₄N), 121.2 (5-

C₅H₄N), 71.2 (NCH₂CMe₂OH), 67.5 (NCH₂CMe₂OH), 63.7

(NCH₂C₅H₄N), 27.2 (NCH₂CMe₂OH (“a”)), 26.3 (NCH₂CMe₂-

OH (“b”)). The arbitrary designations “a” and “b” refer to the

chemically distinct methyl groups. IR (KBr plates, Nujol): ν

3217 (br s), 1591 (w), 1568 (w), 1261 (w), 1200 (w), 1154 (w),

1126 (w), 1101 (m), 1084 (m), 1047 (w), 1023 (w), 995 (w), 972

(w), 935 (w), 907 (w), 855 (w), 800 (w), 766 (w), 723 (w), 645

(w), 622 (w), 583 (w), 488 (w) cm^-1. EI-MS: m/z 252 (23%),

[M]⁺; 192 (97%), [M - CMe₂OH]⁺; 162 (97), [M - CMe₂OH, -

2Me]⁺; 134 (68%), [M - 2CMe₂OH, + H]⁺; 92 (100%),

[CH₂C₅H₄N + H]⁺; 91 (80%), [CH₂C₅H₄N]⁺. Anal. Found (calcd

for C₁₄H₂₄N₂O): C, 66.6 (66.6); H, 9.7 (9.6); N, 11.2 (11.1).

Ti(O₂NN′)₂(23). To a stirred solution of Ti(NMe₂)₄(0.329

g, 1.47 mmol) in benzene (20 mL), cooled to 7 °C, was added

dropwise a solution of H₂O₂NN′ (22) (0.734 g, 2.93 mmol) in

3

¹H NMR (300.1 MHz, 293 K, C₆D₆): δ 8.86 (1 H, d, J 4.9

3

Hz, 6-C₅H₄N), 6.71 (1 H, dd, J 7.2, 8.2 Hz, 4-C₅H₄N), 6.34 (1

H, dd, ³J 4.9, 8.2 Hz, 5-C₅H₄N), 6.26 (1 H, d, ³J 7.2 Hz,

2

3-C₅H₄N), 4.73 (1 H, d, J 14.9 Hz, C₅H₄NCH₂), 3.70 (3 H, m,

2

NCH₂CH₂NSi), 3.12 (1 H, m, NCH₂CH₂NSi), 2.90 (1 H, d, J

14.9 Hz, C₅H₄NCH₂), 2.82 (1 H, m, NCH₂CH₂NSi), 2.30 (1 H,

m, NCH₂CH₂NSi), 2.12 (1 H, m, NCH₂CH₂NSi), 2.00 (1 H, m,

NCH₂CH₂NSi), 1.76 (9 H, s, C(CH₃)₃), 0.63 (9 H, s, Si(CH₃)₃),

0.37 (9 H, s, Si(CH₃)₃). ¹³C{¹H} NMR (75.5 MHz, 293 K,

C₆D₆): δ 159.9 (2-C₅H₄N), 150.5 (6-C₅H₄N), 137.3 (4-C₅H₄N),

122.0 (5-C₅H₄N), 121.3 (3-C₅H₄N), 66.5 (C(CH₃)₃), 64.5 (C₅H₄N-

CH₂), 59.9 (NCH₂CH₂NSi), 59.5 (NCH₂CH₂NSi), 53.2 (NCH₂-

CH₂NSi), 50.2 (NCH₂CH₂NSi), 32.6 (C(CH₃)₃), 3.0 (Si(CH₃)₃),

3.0 (Si(CH₃)₃). IR (CsBr plates, Nujol): ν 1606 (m), 1292 (w),

1243 (m), 1156 (w), 1113 (w), 1075 (m), 1018 (w), 930 (m), 864

(m), 837 (m), 776 (m), 724 (w), 685 (w), 592 (m), 549 (m), 442

(m) cm^-1. EI-MS: m/z 535 (32%), [M]⁺; 500 (7%), [M - Cl]⁺;

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5601

benzene (20 mL). The solution was allowed to warm to room

temperature and was stirred for 16 h. The volatiles were

removed under reduced pressure to give a highly soluble waxy

white solid, which was washed with pentane (25 mL) at 7 °C

and dried in vacuo to give Ti(O₂NN′)₂(23) as a free-flowing

white powder. Yield: 0.643 g (80%).

²J 12.7 Hz, NCH₂CMe₂), 2.44 (2 H, d, ²J 12.7 Hz, NCH₂CMe₂),

1.31 (6 H, s, CMe₂), 0.7 (6 H, s, CMe₂). The compound is too

soluble in C₆D₆and CD₂Cl₂to record ¹³C{¹H} NMR data. IR

(Nujol mull, KBr plates): ν 1608 (w), 1572 (w), 1296 (w), 1261

(w), 1207 (w), 1174 (m), 1158 (m), 1079 (m), 1059 (w), 1019

(m), 983 (m), 948 (w), 801 (w), 767 (w), 684 (w), 641 (w), 617

(w) cm^-1. Anal. Found (calcd for C₁₄H₂₂Cl₂N₂O₂Zr): C, 48.2

(48.8); H, 5.4 (5.4); N, 6.5 (6.8); Cl, 16.5, (17.2).

3

¹H NMR (300.1 MHz, 193 K, CD₂Cl₂): δ 8.50 (2 H, dd, J

5.5 Hz, ⁴J 2.0 Hz, 6-C₅H₄N), 7.69 (2 H, app td, app. ³J 7.5 Hz,

⁴J 2.0 Hz, 4-C₅H₄N), 7.29-7.20 (4 H, overlapping m, 3-,

5-C₅H₄N), 4.42 (2 H, d, ²J 14.5 Hz, NCH₂C₅H₄N), 3.99 (2 H, d,

²J 14.5 Hz, NCH₂C₅H₄N), 3.28 (2 H, d, ²J 14.0 Hz, NCH₂CMe₂O

Zr(NMe₂)₂(O₂NN′) (26). A solution of H₂O₂NN′ (22) (220

mg, 0.87 mmol) in benzene (20 mL) was added dropwise to

Zr(NMe₂)₄(233 mg, 0.87 mmol) in benzene (15 mL) with

stirring and cooling using an ice/water bath. This produced

an immediate darkening in color to give a bright orange

solution by the end of the addition. The solution was stirred

at room temperature for ca. 30 min, which produced no further

color change, and the volatiles were subsquently removed

under reduced pressure to leave a red solid, which was

recrystallized from pentane to give 26 as an orange solid.

Yield: 129 mg (34%).

2

(“a”)), 3.01 (2 H, d, J 13.0 Hz, NCH₂CMe₂O (“b”)), 2.60 (2 H,

d, ²J 13.0 Hz, NCH₂CMe₂O (“b”)), 2.53 (2 H, d, ²J 14.0 Hz,

NCH₂CMe₂O (“a”)), 1.61 (6 H, s, NCH₂CMe₂O), 1.32 (6 H, s,

NCH₂CMe₂O), 1.05 (12 H, overlapping 2 × s, NCH₂CMe₂O).

¹³C{¹H} NMR (75.5 MHz, 193 K, CD₂Cl₂): δ 156.1 (2-C₅H₄N),

148.4 (6-C₅H₄N), 135.4 (4-C₅H₄N), 125.0 (5-C₅H₄N), 121.8 (3-

C₅H₄N), 81.0 (NCH₂CMe₂O), 80.9 (NCH₂CMe₂O), 70.0 (NCH₂-

CMe₂O (“b”)), 64.8 (NCH₂C₅H₄N), 63.8 (NCH₂CMe₂O (“a”)),

31.0 (NCH₂CMe₂O), 29.9 (NCH₂CMe₂O), 29.5 (NCH₂CMe₂O),

27.6 (NCH₂CMe₂O). The arbitrary designations “a” and “b”

refer to the chemically distinct “arms”.

¹H NMR (500. MHz, 293 K, C₆D₆): δ 8.61 (1 H, d, ³J 5.5

3

Hz, 6-C₅H₄N), 6.82 (1 H, dd, J 8.4 Hz, J 7.7 Hz, 4-C₅H₄N),

3

6.46 (1 H, dd, J 7.7 Hz, J 5.5 Hz,5-C₅H₄N), 6.21 (1 H, d, J

8.4 Hz, 3-C₅H₄N), 3.74 (2 H, s, C₅H₄NCH₂), 3.68 (6 H, s, NMe₂

cis or trans to C₅H₄N), 3.40 (6 H, s, NMe₂trans or cis to

C₅H₄N), 2.89 (2 H, d, ²J ) 12.3 Hz, NCH₂CMe₂), 2.53 (2 H, d,

²J ) 12.3 Hz, NCH₂CMe₂), 1.32 (6 H, s, CMe₂), 0.79 (6 H, s,

CMe₂). ¹³C{¹H} NMR (75.5 MHz, 293 K, C₆D₆): δ 160.1 (2-

C₅H₄N), 151.3 (6-C₅H₄N), 137.7 (4-C₅H₄N), 122.7 (5-C₅H₄N),

119.9 (3-C₅H₄N), 79.5 (CMe₂), 76.2 (NCH₂CMe₂), 65.9 (C₅H₄N-

CH₂), 47.9 (NMe₂cis or trans to C₅H₄N), 43.9 (NMe₂trans or

cis to C₅H₄N), 32.6 (CMe₂), 29.0 (CMe₂). IR (CsBr plates,

Nujol): ν cm^-12746 (m), 1632 (w), 1602 (w), 1572 (w), 1300

(w), 1286 (w), 1261 (w), 1238 (w), 1221 (w), 1202 (w), 1182

(m), 1160 (m), 1129 (w), 1091 (m), 1051 (w), 1013 (w), 996 (m),

981 (m), 953 (m), 902 (w), 846 (w), 816 (w), 799 (w), 767 (m),

725 (m), 682 (w), 634 (w), 611 (w), 585 (w), 556 (m), 521 (w).

Anal. Found (calcd for C₁₈H₃₄N₄O₂Zr): C, 50.1 (50.3); H, 7.8

(8.0); N, 12.8 (13.0).

IR (KBr plates, Nujol): ν 1588 (w), 1572 (w), 1302 (w), 1262

(w), 1209 (w), 1156 (w), 1079 (w), 992 (w), 954 (w), 918 (w),

852 (w), 799 (w), 772 (w), 723 (w), 652 (w), 633 (w), 603 (w),

583 (w), 551 (w), 474 (w), 442 (w) cm^-1. EI-MS: m/z 490 (13%),

[M - CMe₂OH, + H]⁺; 398 (100%) [M - CMe₂OH, - CH₂C₅H₄N,

+ H]⁺; 298 (68%), [M - C₅H₄N(CH₂)N(CH₂CMe₂O)]⁺; 93 (76%),

[CH₂C₅H₄N + H]⁺; 92 (65%), [CH₂C₅H₄N]⁺. Anal. Found (calcd

for C₂₈H₄₄N₄O₄Ti): C, 61.0 (61.3); H, 8.1 (8.1); N, 10.2 (10.2).

TiCl₂(O₂NN′) (24). To a stirred slurry of TiCl₄(THF)₂(0.274

g, 8.20 mmol) in benzene (25 mL) cooled to 7 °C was added

dropwise a solution of Ti(O₂NN′)₂(23) (0.450 g, 8.20 mmol) in

benzene (20 mL). The solution was allowed to warm to room

temperature and was stirred for a further 3 h (on warming, a

yellow wax was formed and was triturated by the stirring).

The volatiles were removed under reduced pressure to give

the crude product as a white powder, which was washed with

pentane (60 mL) and dried in vacuo to give 24. Yield: 0.540 g

(90%).

Zr(CH₂SiMe₃)₂(O₂NN′) (27). A solution of H₂O₂NN′ (22)

(0.254 g, 1 mmol) in benzene (20 mL) was added dropwise to

Zr(CH₂SiMe₃)₄(0.441 g, 1 mmol) in benzene (20 mL) with

cooling using an ice/water bath. The mixture was allowed to

warm to room temperature and was stirred overnight. The

volatiles were subsequently removed under reduced pressure,

and the resulting solids were extracted into 80 mL of dry

pentane. The orange solution was filtered, concentrated to 60

mL, and cooled to -30 °C to give 27 as pale orange crystals.

Yield: 0.356 g (69%).

¹H NMR (300.1 MHz, 293 K, pyridine-d₅): δ 9.37 (1 H, d,

³J 6.0 Hz, 6-C₅H₄N), 7.80 (1 H, dd, ³J 7.5 Hz, ³J 6.9 Hz,

3

4-C₅H₄N), 7.38 (1 H, d, J 7.5 Hz, 3-C₅H₄N), 7.24 (1 H, dd, J

3

7.0 Hz, J 6.0 Hz, 5-C₅H₄N), 4.89 (2 H, s, NCH₂C₅H₄N), 3.78

2

(2 H, d, J 12.0 Hz, NCH₂CMe₂O), 3.51 (2 H, d, J 12.0 Hz,

NCH₂CMe₂O), 1.48 (6 H, s, NCH₂CMe₂O), 1.03 (6 H, s,

NCH₂CMe₂O). ¹³C{¹H} NMR (75.5 MHz, 293 K, pyridine-d₅):

δ 159.6 (2-C₅H₄N), 140.7 (6-C₅H₄N), 129.2 (4-C₅H₄N), 124.8

(5-C₅H₄N), 122.6 (3-C₅H₄N), 90.7 (NCH₂CMe₂O), 78.6 (NCH₂-

CMe₂O), 68.4 (NCH₂C₅H₄N), 29.7 (NCH₂CMe₂O), 28.8 (NCH₂C-

Me₂O). IR (CsBr plates, Nujol): ν 1608 (w), 1573 (w), 1291 (w),

1262 (w), 1225 (w), 1207 (w), 1173 (w), 1151 (m), 1092 (w),

1079 (w), 1061 (w), 1022 (w), 975 (m), 946 (m), 906 (w), 830

(w), 803 (w), 786 (w), 765 (w), 721 (w), 686 (w), 656 (m), 611

(m), 528 (w), 503 (w), 468 (w), 413 (m) cm^-1. EI-MS: m/z 368

(1%), [M]⁺; 333 (3%), [M - Cl]⁺. Anal. Found (calcd for C₁₄H₂₂-

Cl₂N₂O₂Ti): C, 45.8 (45.6); H, 6.2 (6.0); N, 7.4 (7.6).

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 8.59 (1 H, d, J 5.3

Hz, 6-C₅H₄N), 6.83 (1 H, ddd, ³J 7.6, 8.0 Hz, ⁴J 1.7 Hz,

4-C₅H₄N), 6.42 (1 H, dd, ³J 5.3, 7.6 Hz, 5-C₅H₄N), 6.19 (1 H, d,

³J 8.0 Hz, 3-C₅H₄N), 3.60 (2 H, s, NC₅H₄NCH₂), 2.43 (2 H, Part

A of an AB system, ²J 12.8 Hz, NCH₂CMe₂), 2.37 (2 H, Part B

of an AB system, ²J 12.8 Hz, NCH₂CMe₂), 1.24 (6 H, s, CMe₂),

0.70 (6 H, s, CMe₂), 0.55 (9 H, s, CH₂SiMe₃cis to pyridyl group),

0.55 (2 H, s, CH₂SiMe₃trans to pyridyl group), 0.44 (9 H, s,

CH₂SiMe₃trans to pyridyl group), 0.26 (2 H, s, CH₂SiMe₃cis

to pyridyl group). ¹³C{¹H} NMR (75.5 MHz, 293 K, C₆D₆): δ

160.3 (2-C₅H₄N), 150.2 (6-C₅H₄N), 138.1 (4-C₅H₄N), 122.4 (5-

C₅H₄N), 120.3 (3-C₅H₄N), 80.8 (CMe₂), 76.5 (NCH₂CMe₂), 66.7

(NC₅H₄NCH₂), 47.6 (CH₂SiMe₃trans to pyridyl group), 45.0

(CH₂SiMe₃cis to pyridyl group), 32.4 (CMe₂), 29.1 (CMe₂), 4.6

(CH₂SiMe₃cis to pyridyl group), 4.2 (CH₂SiMe₃trans to pyridyl

group). IR (Nujol mull): ν 1604 (w), 1574 (w), 1302 (w), 1287

(w), 1249 (w), 1238 (w), 1204 (w), 1185 (m), 1089 (w), 1060

(w), 1002 (w), 950 (w), 872 (m), 853 (m), 824 (w), 763 (m), 741

(w), 677 (w), 637 (w) cm^-1. MS-EI: m/z 499 (5%), [M - CH₃]⁺;

427 (100%), [M - CH₂SiMe₃]⁺. Anal. Found (calcd for

C₂₂H₄₄N₂O₂Si₂Zr): C, 50.4; (51.2); H, 8.8 (8.6); N, 5.4 (5.4).

[Zr(CH₂SiMe₃)(THF)(O₂NN′)][Me₃SiCH₂BAr^F₃] (28-Me₃-

ZrCl₂(O₂NN′) (25). A solution of H₂O₂NN′ (22) (0.36 g, 1.4

mmol) in benzene (15 mL) was added dropwise to ZrCl₂(CH₂-

SiMe₃)₂(Et₂O)₂(0.70 g, 1.4 mmol) in benzene (20 mL) with

cooling using an ice/water bath. The mixture was allowed to

warm to room temperature and stirred overnight. A white

precipitate progressively appeared. The volatiles were removed

under reduced pressure, and the resulting powder was ex-

tracted into 60 mL of dichloromethane. Filtration and evapo-

ration of the solvent gave 25 as a white powder. Yield: 0.30 g

(52%).

3

¹H NMR (500.0 MHz, 293 K, C₆D₆): δ 9.12 (1 H, d, J 6.0

Hz, 6-C₅H₄N), 6.68 (1 H, ddd, ³J 7.2 and 8.1 Hz, ⁴J 1.7 Hz,

4-C₅H₄N), 6.17 (1 H, dd, ³J 4.9, 7.2 Hz, 5-C₅H₄N), 6.09 (1 H, d,

³J 8.1 Hz, 3-C₅H₄N), 3.68 (2 H, s, NC₅H₄NCH₂), 3.05 (2 H, d,

SiCH₂BAr^F₃). A solution of BAr^F(0.070 g, 0.136 mmol) in

3

5602 Organometallics, Vol. 24, No. 23, 2005

Skinner et al.

Table 8. X-ray Data Collection and Processing Parameters for Zr(CH₂Ph)₂(N₂NN′) (3), ZrCl(CH₂Ph)(N₂NN′)

(6), Ti(NAr)(N₂NN′) (15), Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19), Ta(N^tBu)Cl(N₂NN′) (21), H₂O₂NN′ (22), and

Zr(CH₂SiMe₃)₂(O₂NN′) (27)

3

6

15

empirical formula

fw

C

₃₀H₄₆N₄Si₂Zr

C₂₃H₃₉ClN₄Si₂Zr

554.44

175

C₂₈H₄₉N₅Si₂Ti

559.8

610.12

150

temp/K

170

wavelength/Å

space group

a/Å

0.71073

P2₁/n

0.71073

P4₂/n

0.71073

Pbcm

13.296(1)

17.017(1)

14.262(1)

90

25.584(1)

8.459(1)

90

9.8632(4)

18.413(1)

17.507(1)

90

b/Å

c/Å

R/deg

â/deg

94.792(5)

90

γ/deg

V/Å³

3215.6(8)

4

5536.0(9)

8

3179.4(8)

4

Z

d(calcd)/Mg‚m^-3

abs coeff/mm^-1

R indices R₁, R_w

[I > 3σ(I)]^a

1.26

0.43

1.33

0.59

1.17

0.36

R₁) 0.0564

R_w) 0.0424

R₁) 0.0692

R_w) 0.0647

R₁) 0.0574

R_w) 0.0434

19

21

22

27

empirical formula

fw

C

₂₅H₅₂N₆Si₂Zr

C₂₀H₄₁ClN₅Si₂Ta

624.16

175

C₁₄H₂₄N₂O₂

252.36

C₂₂H₄₄N₂O₂Si₂Zr

5115.99

584.12

150

temp/K

150

wavelength/Å

space group

a/Å

0.71073

P2₁/n

0.71073

P2₁/n

0.71073

P2₁/n

0.71073

P1h

9.586(1)

16.247(1)

20.632(2)

90

12.828(1)

14.178(2)

31.148(3)

90

14.8201(5

6.2365(2)

16.7248(7)

90

11.0613(2)

13.2371(2)

20.4745(4)

107.2552(8)

95.4488(8)

95.4178(9)

2826.21(9)

4

b/Å

c/Å

R/deg

â/deg

103.30(1)

90

100.19(3)

90

107.934(2)

90

γ/deg

V/Å³

3127(1)

4

5576(1)

8

1470.7(1)

4

Z

d(calcd)/Mg‚m^-3

abs coeff/mm^-1

R indices R₁, R_w

[I > 3σ(I)]^a

1.24

0.44

1.49

4.09

1.14

0.076

1.21

0.49

R₁) 0.0355

R_w) 0.0349

R₁) 0.0253

R_w) 0.0260

R₁) 0.0246

R_w) 0.0293

R₁) 0.0385

R_w) 0.0400

2

^aR₁) ∑||F_o| - |F_c||/∑|F_o|; R_w) x{∑w(|F_o| - |F_c|)²/∑(w|F_o| }.

CH₂Cl₂(3 mL) was added at room temperature to Zr(CH₂-

SiMe₃)₂(O₂NN′) (27) (0.071 g, 0.138 mmol) in CH₂Cl₂(4 mL)

in the presence of THF (12 µL, 0.139 mmol). After 90 min at

room temperature, the volatiles were removed under reduced

an ice/water bath. The mixture was allowed to warm to room

temperature, and the stirring was continued for a further 30

min. The volatiles were removed under reduced pressure to

yield a colorless oily compound, which was triturated with

Et₂O. The compound 29 was obtained as a white powder after

removal of the volatiles under reduced pressure. Yield: 0.11

g (90%).

pressure to yield 28-Me₃SiCH₂BAr^Fas a white powder.

3

Yield: 0.13 g (87%).

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 8.94 (1 H, d, ³J 5.2

Hz, 6-C₅H₄N), 8.11 (1 H, ddd, ³J 7.6, 8.0 Hz, ⁴J 1.7 Hz,

4-C₅H₄N), 7.62 (1 H, dd, ³J 5.2, 7.6 Hz, 5-C₅H₄N), 6.19 (1 H, d,

³J 8.0 Hz, 3-C₅H₄N), 4.41 (2 H, s, NC₅H₄NCH₂), 4.38 (4 H, br

¹H NMR (500.0 MHz, 293 K, CD₂Cl₂): δ 8.86 (1 H, d, ³J 5.2

Hz, 6-C₅H₄N), 8.31 (1 H, ddd, ³J 7.5, 8.1 Hz, ⁴J 1.5 Hz,

4-C₅H₄N), 7.90 (1 H, dd, ³J 5.2, 7.5 Hz, 5-C₅H₄N), 7.77 (1 H, d,

2

m, O(CH₂CH₂)₂), 3.22 (2 H, part A of an AB system, J 13.7

³J 8.1 Hz, 3-C₅H₄N), 4.94 (2 H, d, J 16.4 Hz, NC₅H₄NCH₂),

2

Hz, NCH₂CMe₂), 3.12 (2 H, part B of an AB system, J 13.7

4.35 (2 H, d, J 16.4 Hz, NC₅H₄NCH₂), 3.85 (2 H, d, J 14.4

Hz, NCH₂CMe₂), 3.58 (2 H, d, ²J 14.4 Hz, NCH₂CMe₂), 3.07 (2

H, d, ²J 14.3 Hz, NCH₂CMe₂), 2.73 (2 H, d, ²J 14.3 Hz, NCH₂-

CMe₂), 1.84 (6 H, s, CMe₂), 1.70 (6 H, s, CMe₂), 1.49 (6 H, s,

CMe₂), 1.41 (6 H, s, CMe₂), 0.87 (2 H, part A of an AB system,

Hz, NCH₂CMe₂), 2.10 (4 H, br m, O(CH₂CH₂)₂), 1.33 (6 H, s,

CMe₂), 1.05 (6 H, s, CMe₂), 0.51 (2 H, br s, BCH₂SiMe₃), 0.31

(2 H, s, CH₂SiMe₃cis to pyridyl group), -0.08 (9 H, s, CH₂-

SiMe₃cis to pyridyl group), -0.39 (s, 2 H, BCH₂SiMe₃). ¹³C-

{¹H} NMR (125.7 MHz, 293 K, CD₂Cl₂): δ 159.6 (2-C₅H₄N),

151.5 (6-C₅H₄N), 148.7 (¹J 232 Hz, o-C₆F₅), 142.4 (4-C₅H₄N),

137.9 (¹J 243 Hz, p-C₆F₅), 136.7 (¹J 268 Hz, m-C₆F₅), 128.9

(v br, BC), 125.1 (5-C₅H₄N), 124.1 (3-C₅H₄N), 82.6 (CMe₂), 75.6

(O(CH₂CH₂)₂), 73.9 (NCH₂CMe₂), 64.3 (NC₅H₄NCH₂), 48.0

(CH₂SiMe₃cis to pyridyl group), 32.7 (CMe₂), 30.4 (CMe₂), 25.7

(O(CH₂CH₂)₂), 9.0 (v br, BCH₂SiMe₃), 2.7 (CH₂SiMe₃cis to

pyridyl group), 1.1 (CH₂SiMe₃trans to pyridyl group). ¹⁹F NMR

(282 MHz, CD₂Cl₂, 293 K): δ -132.17 (6 F, d, ³J 19.8 Hz,

o-C₆F₅), -165.25 (3 F, t, ³J 20.2 Hz, p-C₆F₅), -167.91 (6 F, m,

m-C₆F₅). IR (Nujol mull, KBr plates): ν 1638 (m), 1612 (m),

1572 (w), 1559 (w), 1542 (w), 1510 (s), 1175 (m), 1127 (vw),

1079 (s), 861 (w), 827 (m), 782 (m), 767 (w), 670 (w), 627 (w)

cm^-1. Anal. Found (calcd for C₄₄H₅₂BF₁₅N₂O₃Si₂Zr‚0.6CH₂-

Cl₂): C 46.2 (46.5), H 5.0 (4.7), N 2.6 (2.4).

²J 11.7 Hz, CH₂SiMe₃), 0.80 (2 H, part B of an AB system, J

2

11.7 Hz,CH₂SiMe₃), 0.51 (2 H, br s, BCH₂SiMe₃), -0.31 and

-0.36 (2 × 9 H, 2 × s, CH₂SiMe₃and BCH₂SiMe₃). ¹³C{¹H}

NMR (125.7 MHz, 293 K, CD₂Cl₂): δ 155.9 (2-C₅H₄N), 148.9

(6-C₅H₄N), 148.5 (d, ¹J 242 Hz, o-C₆F₅), 144.1 (4-C₅H₄N), 138.6

1

(d, J 245 Hz, p-C₆F₅), 136.6 (d, J 234 Hz, m-C₆F₅), 126.2 (3-

C₅H₄N), 126.1 (5-C₅H₄N), 88.1 (CMe₂), 87.0 (CMe₂), 75.2

(NCH₂CMe₂), 69.1 (NCH₂CMe₂), 67.4 (CH₂SiMe₃), 63.5 (NC₅-

H₄NCH₂), 33.0 (CMe₂), 32.9 (CMe₂), 31.8 (CMe₂), 29.8 (CMe₂),

15.4 (BCH₂SiMe₃), 1.6 (CH₂SiMe₃), 1.1 (CH₂SiMe₃). ¹⁹F NMR

(282 MHz, 293 K, CD₂Cl₂): δ -132.10 (6 F, d, ³J, o-C₆F₅),

-165.06 (3 F, t, ³J 20.6 Hz, p-C₆F₅), -167.74 (6 F, m, m-C₆F₅).

IR (Nujol mull): ν 1646 (m), 1614 (m), 1571 (w), 1559 (w), 1542

(w), 1510 (s), 1305 (vw), 1128 (vw), 1079 (s), 910 (w), 848 (w),

828 (m), 768 (m), 687 (w), 644 (w), 625 (w) cm^-1. Anal. Found

(calcd for C₄₀H₄₄BF₁₅N₂O₂Si₂Zr): C, 46.9 (46.8); H, 4.8 (4.3);

N, 2.8 (2.7).%.

[Zr₂(CH₂SiMe₃)₂(O₂NN′)₂][Me₃SiCH₂BAr^F₃]₂(29-Me₃Si-

CH₂BAr^F₃). A solution of BAr^F(0.099 g, 0.193 mmol) in

3

benzene (15 mL) was added to Zr(CH₂SiMe₃)₂(O₂NN′) (27)

(0.100 g, 0.193 mmol) in benzene (15 mL) with cooling using

Crystal Structure Determinations of Zr(CH₂Ph)₂-

(N₂NN′) (3), ZrCl(CH₂Ph)(N₂NN′) (6), Ti(NAr)(N₂NN′) (15),

Group 4 Organometallic and Imido Compounds

Organometallics, Vol. 24, No. 23, 2005 5603

Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19), Ta(N^tBu)Cl(N₂NN′) (21),

H₂O₂NN′ (22), and Zr(CH₂SiMe₃)₂(O₂NN′) (27). Crystal data

collection and processing parameters are given in Table 8.

Crystals were mounted on a glass fiber using perfluoropoly-

ether oil and cooled rapidly in a stream of cold N₂. Diffraction

data were measured using an Enraf-Nonius DIP2000 or

KappaCCD diffractometer. Intensity data were processed

using the DENZO-SMN package.³⁵The structures were solved

using the direct-methods program SIR92,³⁶which located all

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

refinement was carried out using the CRYSTALS program

suite.³⁷Coordinates and anisotropic thermal parameters of all

non-hydrogen atoms were refined. Hydrogen atoms were

positioned geometrically with the exception of H(1) in 19 and

the O-bound atoms in 22, which were located from Fourier

difference maps and positionally refined. Minor disorder in 6

and 15 was satisfactorily modeled. Weighting schemes were

applied as appropriate. Full listings of atomic coordinates,

bond lengths and angles, and displacement parameters have

been deposited at the Cambridge Crystallographic Data Cen-

ter. See Notice to Authors, Issue No. 1.

Acknowledgment. We thank the EPSRC, Lever-

hulme Trust, and European Commision (Marie Curie

Fellowship) for support of this work. We thank Dr. A.

C. Hillier for the low-temperature NMR spectra for 13-

PhCH₂BAr^Fand DSM Research for samples of BAr^F

.

3

Supporting Information Available: X-ray crystallo-

graphic files in CIF format for the structure determinations

of Zr(CH₂Ph)₂(N₂NN′) (3), ZrCl(CH₂Ph)(N₂NN′) (6), Ti(NAr)-

(N₂NN′) (15), Zr(NH^tBu)(NC₅H₁₀)(N₂NN′) (19), Ta(N^tBu)Cl(N₂-

NN′) (21), H₂O₂NN′ (22), and Zr(CH₂SiMe₃)₂(O₂NN′) (27). This

material is available free of charge via the Internet at

http://pubs.acs.org.

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

Collected in Oscillation Mode, Methods in Enzymology; Academic

Press: New York, 1997.

(36) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.;

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

435.

OM0506365

(37) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P.

W.; Cooper, R. I. CRYSTALS, issue 11; Chemical Crystallography

Laboratory: Oxford, U.K., 2001.

Article Doi

New group 4 organometallic and imido compounds of diamide-diamine and related dianionic O2N2-donor ligands

DOI: 10.1021/om0506365

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