Ti=NR vs Ti-R′ functional group selectivity in titanium imido alkyl cations from an experimental perspective

6096

Organometallics 2008, 27, 6096–6110

TidNR vs Ti-R′ Functional Group Selectivity in Titanium Imido

Alkyl Cations from an Experimental Perspective

Paul D. Bolton,^†Marta Feliz,^‡Andrew R. Cowley,^†Eric Clot,*^,‡and Philip Mountford*^,†

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

Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1, cc 1501, Place Euge`ne

Bataillon, F-34095 Montpellier Cedex 5, France

ReceiVed July 26, 2008

A study of the reactions of the titanium imido methyl cation [Ti(N^tBu)(Me₃[9]aneN₃)X]⁺(5⁺, X )

Me) and key analogues (6⁺, X ) CH₂SiMe₃; 7⁺, X ) Cl) with a range of unsaturated substrates provides

a comprehensive evaluation of reaction site selectivity in transition-metal cations which contain both

TidNR and Ti-R′ functional groups as potential sites for 2π + 2π cycloaddition and migratory insertion,

respectively. Cations 5⁺and 6⁺reacted with MeCN to form Ti-R′ insertion products. Insertion reactions

were also exclusively observed in their reactions with N,N′-disubstituted carbodiimides or tert-butyl

isocyanate. In contrast, reaction of the chloride cation 7⁺with diisopropylcarbodiimide or tert-butyl

i

t

isocyanate afforded the unusual σ adducts [Ti(N^tBu)(Me₃[9]aneN₃)(L)Cl]⁺(L ) PrNCNⁱPr, BuNCO),

which slowly underwent 2π + 2π cycloaddition. Reaction of 5⁺with the internal alkynes PhCCR (R )

Ph, SiMe₃) also showed exclusive preference for insertion into the Ti-Me bond. In contrast, reaction

with terminal alkynes RCCH (R ) Ph, SiMe₃) yielded only the azametallacyclic products via 2π + 2π

cycloaddition reactions. The chloride cation 7⁺also underwent a 2π + 2π cycloaddition with PhCCH

but was unreactive toward PhCCPh, ethylene, styrene, or 1-hexene.

been widely studied for over 20 years.^6-17Imido ligands have

become an established feature of the ligand landscape for many

Introduction

This paper, in conjunction with the accompanying DFT study,

presents a detailed account of the ligand reaction site preferences

of the titanium imido alkyl cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺

(R ) Me, CH₂SiMe₃) with a range of different unsaturated

substrates. The development of transition-metal complexes for

particular applications evidently requires a sound knowledge

of the properties and reaction characteristics of the supporting

ligand or ligand sets. It may also be the case that a ligand

potentially susceptible to attack by an external reagent could

appear to be inert when an alternative ligand or functional group

offers an alternative kinetically or thermodynamically favored

reactive site.¹This has been a fundamental issue in organome-

tallic chemistry for decades. For example, while hydride attacks

the cyclopentadienyl ring in [Co(η⁵-C₅H₅)₂]⁺and the arene ring

in [Re(η⁶-C₆H₅Me)₂]⁺,^2,3in the non-homoleptic cation [Fe(η⁵-

C₅H₅)(η⁶-C₆H₆)]⁺it is only the six-membered ring that is

attacked.⁴Ligand substitution can also alter the expected reaction

outcomes: on reaction of [Fe(η⁵-C₅H₅)(η⁶-C₆Me₆)]⁺with hy-

dride the permethylated benzene is unreactive and now only

the cyclopentadienyl ring is substituted.⁵This signals a change

from kinetic to thermodynamic control.¹

transition metals, and the six-electron -donor imido dianion is

isolobal with cyclopentadienide.^18-21In a signiﬁcant portion

of its chemistry the MdNR bond is inert to common substrates

and the imido ligand plays a “supporting” role. One prominent

example of this aspect is the Schrock oleﬁn metathesis catalyst

family M(NR)(CHR′)(OR′′)₂(M ) Mo, W) widely exploited

in organic and inorganic applications^22-25and comprehensively

studied computationally.^26-31The 2π + 2π cycloaddition

reaction site selectivity of ethylene for the ModCH₂bond in

(6) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV. 1980, 31, 123.

(7) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-

Interscience: New York, 1988.

(8) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.

(9) Mountford, P. Chem. Commun. 1997, 2127.

(10) Romao, C. C.; Ku¨hn, F. E.; Herrmann, W. A. Chem. ReV. 1997,

97, 3197.

(11) Cundari, T. R. Chem. ReV. 2000, 100, 807.

(12) Sharp, P. R. Dalton Trans. 2000, 2647.

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

(14) Eikey, R. A.; Abu-Omar, M. M. Coord. Chem. ReV. 2003, 243,

83.

(15) Leung, W.-H. Eur. J. Inorg. Chem. 2003, 583.

(16) Giesbrecht, G. R.; Gordon, J. C. Dalton Trans. 2004, 2387.

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

(18) Williams, D. S.; Schoﬁeld, M. H.; Anhaus, J. T.; Schrock, R. R.

J. Am. Chem. Soc. 1990, 112, 6728.

Transition-metal imido compounds (L)MdNR (typically R

) alkyl, aryl and L ) a supporting ligand or ligand set) have

(19) Glueck, D. S.; Green, J. C.; Michelman, R. I.; Wright, I. N.

Organometallics 1992, 11, 4221.

(20) Dyer, P. W.; Gibson, V. C.; Howard, J. A. K.; Whittle, B.; Wilson,

C. J. Chem. Soc., Chem. Commun 1992, 1666.

(21) Gibson, V. C. J. Chem. Soc., Dalton Trans. 1994, 1607.

(22) Schrock, R. R. Acc. Chem. Res. 1990, 23, 158.

(23) Schrock, R. R. Pure Appl. Chem. 1994, 66, 1447.

(24) Schrock, R. R. Dalton Trans. 2001, 2541.

(25) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42,

4592.

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

philip.mountford@chem.ox.ac.uk (P.M.); clot@univ-montp2.fr (E.C.).

^†University of Oxford.

^‡Institut Charles Gerhardt.

(1) Davies, S. G.; Green, M. L. H.; Mingos, D. M. P. Tetrahedron 1978,

34, 3047.

(2) Green, M. L. H.; Pratt, L.; Wilkinson, G. J. Chem. Soc. 1959, 3753.

(3) Jones, D.; Pratt, L.; Wilkinson, G. J. Chem. Soc. 1962, 4458.

(4) Nesmeyanov, A. N.; Vol’Kenau, N. A. IzV. Akad. Nauk SSSR, Ser.

Khim. 1975, 1151.

(5) Khand, I. U.; Pauson, P. L.; Watts, W. E. J. Chem. Soc. C 1969,

2024.

(26) Rappe´, A. K.; Goddard, W. A. J. Am. Chem. Soc. 1982, 104, 448.

(27) Wu, Y.-D.; Peng, Z.-H. J. Am. Chem. Soc. 1997, 119, 8043.

(28) Wu, Y.-D.; Peng, Z.-H. Inorg. Chim. Acta 2003, 345, 241.

10.1021/om800709f CCC: $40.75

2008 American Chemical Society

Publication on Web 10/29/2008

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6097

this type of system was explained by Ziegler in terms of both

kinetic and thermodynamic preferences.³²Notwithstanding the

“supporting” role of the imido ligands in the Schrock metathesis

catalysts, in a signiﬁcant number of other compounds (especially

for the group 4 metals) coupling reactions of the MdNR

functional group with unsaturated organic and other substrates

is found to be facile.^8,9,13,17,33

set, R ) initiating alkyl group or polymeryl chain).^48-50

Furthermore, the chemistry of early-transition-metal alkyl cations

in general is well-understood. However, although a number of

cationic imido compounds, without an additional metal-alkyl

bond, have been reported,^51-57only a handful of previous

studies have looked at the question of reaction site selectivity

in imido compounds (neutral or cationic) that also feature a

metal-alkyl bond.^58-61

The ﬁrst well-deﬁned experimental observation was by

Legzdins, who found that neutral Cp*W(NTol)₂CH₂SiMe₃(Tol

) p-tolyl) reacted with p-tolyl isocyanate to form exclusively

a 2π + 2π cycloaddition product via reaction of the imido ligand

with the metal-alkyl bond left intact.⁵⁸In contrast, Arnold and

Bergman recently reported that Ta(N^tBu)(CH₂Ph)₃gave exclu-

sively alkyl group insertion products with diisopropylcarbodi-

imide and 2,6-dimethylphenyl isocyanide.⁶¹

Gibson reported that the bis(imido)chromium systems

Cr(NR)₂X₂(R ) alkyl, aryl; X ) Cl, CH₂Ph) formed moderately

active oleﬁn polymerization catalysts with suitable activators

and described limited in situ spectroscopic evidence for the

benzyl cation [Cr(N^tBu)₂(CH₂Ph)]⁺and a PMe₃adduct.⁶²No

reactivity studies were reported. Jensen and Børve reported DFT

studies of the reaction of the model cation [Cr(NH)₂Me]⁺with

C₂H₄and found that, although insertion of C₂H₄into the Cr-Me

bond was thermodynamically favored, cycloaddition to CrdNH

was kinetically the much preferred route.^63,64However, no

experimental probes of this system have been reported and the

computational predictions have remained untested. In a previous

attempt to address this question of reaction site selectivity in

imido alkyl cations, we studied the reactions of [W(NPh){MeC(2-

C₅H₄N)(CH₂NSiMe₃)₂}Me]⁺with polar substrates such as CO₂

and certain heterocumulenes.^59,60In contrast to Jensen and

Børve’s predictions,^63,64DFT calculations for the tungsten cation

suggested that cycloaddition to WdNPh was both kinetically

and thermodynamically disfaVored relative to insertion into

W-Me. Unfortunately the diamide-pyridine ligand set in this

case is noninnocent, and attempts to test experimentally the DFT

predictions gave exclusively insertion into the W-N_amidebonds

of the supporting ligand itself. Finally, Arnold and Bergman⁶¹

found that the ill-deﬁned and insoluble species

Since the early 90s the development of non-cyclopentadienyl

(“post-metallocene”) Ziegler-type oleﬁn polymerization catalysts

has been a topic of enormous academic and commercial

signiﬁcance.^34-41Imido “supporting” ligands have been widely

exploited in this regard, and a large number of compounds have

been assessed for their activity.⁴²The most active and also most

systematically studied class of imido-supported Ziegler catalyst

is of the type Ti(NR)(fac-N₃)Cl₂, where fac-N₃represents a

neutral tridentate N₃-donor ligand such as Me₃[9]aneN₃(1,4,7-

trimethyltriazacyclononane, 1-R^43-45) and HC(Me₂pz)₃(2-R^46,47).

In both of these catalyst families, structure-activity relationship

studies using high-throughput screening techniques found that

bulky imido N substituents “R” were prerequisites for high

t

catalytic productivities (e.g., R ) ^tBu, adamantyl, CMe₂CH₂Bu,

t

2-C₆H₄Bu, 2-C₆H₄CF₃), especially at the commercially relevant

high operating temperatures that these catalysts tolerate.

The active species in early-transition-metal Ziegler catalysts

are alkyl cations [(L)MR]⁺(L ) supporting ligand or ligand

(29) Goumans, T. P. M.; Ehlers, A. W.; Lammertsma, K. Organome-

tallics 2005, 24, 3200.

(30) Solans-Monfort, X.; Clot, E.; Cope´ret, C.; Eisenstein, O. J. Am.

Chem. Soc. 2005, 127, 14015.

(31) Poater, A.; Solans-Monfort, X.; Clot, E.; Cope´ret, C.; Eisenstein,

O. J. Am. Chem. Soc. 2007, 129, 8207.

(32) Monteyne, K.; Ziegler, T. Organometallics 1998, 17, 5901.

(33) Gade, L. H.; Mountford, P Coord. Chem. ReV. 2001, 65, 216–217.

(34) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Way-

mouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.

(35) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255.

(36) Kaminsky, W. J. Chem. Soc., Dalton Trans. 1998, 1413.

(37) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem. ReV. 2000,

100, 1253.

(48) Jordan, R. F. AdV. Organomet. Chem. 1991, 32, 325.

(49) Grubbs, R. H.; Coates, G. W. Acc. Chem. Res. 1996, 29, 85.

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

(51) Herrmann, W. A.; Baratta, W.; Herdtweck, E. J. Organomet. Chem.

1997, 541, 445.

(52) Witte, P. T.; Meetsma, A.; Hessen, B.; Budzelaar, P. H. M. J. Am.

Chem. Soc. 1997, 119, 10561.

(53) Blake, R. E.; Antonelli, D. M.; Henling, L. M.; Schaefer, W. P.;

Hardcastle, K. I.; Bercaw, J. E. Organometallics 1998, 17, 718.

(54) Humphries, M. J.; Douthwaite, R. E.; Green, M. L. H. Dalton Trans.

2000, 2952.

(55) Gardner, J. D.; Robson, D. A.; Rees, L. H.; Mountford, P. Inorg.

Chem. 2001, 40, 820.

(56) Basuli, F.; Clark, R. L.; Bailey, B. C.; Brown, D.; Huffman, J. C.;

Mindiola, D. J. Chem. Commun. 2005, 2250–2252.

(57) Basuli, F.; Aneetha, H.; Huffman, J. C.; Mindiola, D. J. J. Am.

Chem. Soc. 2005, 127, 17992.

(58) Legzdins, P.; Phillips, E. C.; Rettig, S. J.; Trotter, J.; Veltheer, J. E.;

Yee, V. C. Organometallics 1992, 11, 3104.

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

Mountford, P. Organometallics 2004, 23, 4444.

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

Mountford, P. Organometallics 2005, 24, 2368.

(38) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100,

1169.

(39) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283.

(40) Mitani, M.; Saito, J.; Ishii, S.; Nakayama, Y.; Makio, H.; Mat-

sukawa, N.; Matsui, S.; Mohri, J.; Furuyama, R.; Terao, H.; Bando, H.;

Fujita, T. Chem. Rec 2004, 4, 137.

(41) Stephan, D. W. Organometallics 2005, 24, 2548.

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

(43) Adams, N.; Arts, H. J.; Bolton, P. D.; Cowell, D.; Dubberley, S. R.;

Friederichs, N.; Grant, C.; Kranenburg, M.; Sealey, A. J.; Wang, B.; Wilson,

P. J.; Cowley, A. R.; Mountford, P.; Schro¨der, M. Chem. Commun. 2004,

434.

(44) Adams, N.; Arts, H. J.; Bolton, P. D.; Cowell, D.; Dubberley, S. R.;

Friederichs, N.; Grant, C. M.; Kranenburg, M.; Sealey, A. J.; Wang, B.;

Wilson, P. J.; Zuideveld, M. A.; Blake, A. J.; Schro¨der, M.; Mountford, P.

Organometallics 2006, 25, 3888.

(45) Bolton, P. D.; Adams, N.; Clot, E.; Cowley, A. R.; Wilson, P. J.;

Schro¨der, M.; Mountford, P. Organometallics 2006, 25, 5549.

(46) Bigmore, H. R.; Dubberley, S. R.; Kranenburg, M.; Lawrence, S. C.;

Sealey, A. J.; Selby, J. D.; Zuideveld, M.; Cowley, A. R.; Mountford, P.

Chem. Commun. 2006, 436.

(61) Anderson, L. L.; Schmidt, J. A. R.; Arnold, J.; Bergman, R. G.

Organometallics 2006, 25, 3394.

(62) Coles, M. P.; Dalby, C. I.; Gibson, V. C.; Little, I. R.; Marshall,

E. L.; Ribeiro da Costa, M. H.; Mastroianni, S. J. Organomet. Chem. 1999,

591, 78.

(63) Jensen, V. R.; Børve, K. J. Organometallics 2001, 20, 616.

(64) Jensen, V. R.; Børve, K. J. Chem. Commun. 2002, 542.

(47) Bigmore, H. R.; Zuideveld, M.; Kowalczyk, R. M.; Cowley, A. R.;

Kranenbrug, M.; McInnes, E. J. L.; Mountford, P. Inorg. Chem. 2006, 45,

6411.

6098 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

“[Ta(N^tBu)(CH₂Ph)₂][BAr^F]” could be generated in situ and

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

[Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)]⁺(8⁺)

4

intercepted by reaction with certain alkynes and alkenes. In these

reactions Ta-CH₂Ph bond insertion products were exclusively

formed. However, the poorly characterized nature of the highly

unsaturated “[Ta(N^tBu)(CH₂Ph)₂]⁺” (which could for example

contain unreactive Ta(µ-N^tBu)Ta bridging imido groups) limit

to some extent the insight attached to these results. Computa-

tional studies of this system have not been reported.

Ti(1)-N(1)

Ti(1)-N(2)

Ti(1)-N(3)

Ti(1)-N(4)

Ti(1)-N(5)

2.366(2)

2.329(2)

2.251(2)

1.755(2)

1.860(2)

Ti(1)-N(6)

N(4)-C(10)

N(5)-C(14)

N(6)-C(17)

2.227(2)

1.405(3)

1.296(4)

1.144(3)

Ti(1)-N(4)-C(10)

Ti(1)-N(6)-C(17)

168.43(19) Ti(1)-N(5)-C(14)

159.1(2)

N(5)-C(14)-C(16) 119.9(3)

170.93(19)

N(5)-C(14)-C(15) 123.5(3)

In pursuit of a better understanding of the catalyst families

Ti(NR)(fac-N₃)Cl₂,^43-46we recently reported that the thermally

stable alkyls Ti(N^tBu)(Me₃[9]aneN₃)R₂(3, R ) Me; 4, R )

CH₂SiMe₃) are cleanly and quantitatively converted to the well-

deﬁned cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺(5⁺, R ) Me; 6⁺,

and Jordan’s^48,70studies of the nitrile insertion reactions of group

4 metallocenium and cyclopentadienyl-dicarbollide⁷¹alkyls,

with which the cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺are isolobal.

In contrast, only one example is known of the cycloaddition

reactions of organonitriles with a transition-metal-imido link-

age.⁷²

R ) CH₂SiMe₃) by treatment with [CPh₃][BAr^F] (Ar^F

)

4

C₆F₅).^65,66The chloride cation [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺)

was also readily accessed from Ti(N^tBu)(Me₃[9]aneN₃)(Me)Cl.⁶⁶

The electronic structures of the alkyl cations 5⁺and 6⁺(isolobal

analogues of the metallocenium alkyls [Cp₂MR]⁺) have been

comprehensively studied using DFT and spectroscopic meth-

ods.⁶⁶The base-free alkyl cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺

therefore provide an excellent platform for stoichiometric

reactivity studies. For example, they underwent a range of well-

characterized reactions, including single and double C-H bond

activation processes and formation of a number of main -group

and transition-metal alkyl adducts.^45,66,67

Reaction of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3) with [CPh₃]-

[BAr^F] in CH₂Cl₂(generating 5⁺in situ⁶⁶) in the presence of

4

2 equiv of MeCN afforded the imido-ketimido species

[Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)][BAr^F] (8-BAr^F) in

4

77% isolated yield as a yellow crystalline solid (eq 1). The NMR

and IR data for 8⁺are consistent with the proposed structure,

which has been conﬁrmed by X-ray crystallography (Table 1,

Figure 1). The methyl groups of the NCMe₂ligand were

equivalent at room temperature, but cooling a sample to -60

°C resulted in decoalescence into two resonances of equal

intensity. This is consistent with the expected multiple-bond

character in the Ti-N_ketimidelinkage.⁶⁸The IR spectrum of

8-BAr^F₄showed the expected bands for coordinated MeCN and

a NCMe₂ligand. In a similar fashion, sequential reaction of

Ti(N^tBu)(Me₃[9]aneN₃)(CH₂SiMe₃)₂with [CPh₃][BAr^F] and 2

4

equiv of MeCN in CD₂Cl₂gave [Ti(N^tBu)(Me₃[9]ane-

N₃){NCMe(CH₂SiMe₃)}(NCMe)][BAr^F] (9-BAr^F) in 60%

4

isolated yield after ca. 1 h at room temperature. The IR and

NMR data for 9-BAr^F₄are analogous to those for 8-BAr^F. In

4

neither case was evidence for reaction at the TidN^tBu linkage

observed.

In this contribution we describe experimental studies of the

reactions of [Ti(N^tBu)(Me₃[9]aneN₃)X]⁺(5⁺-7⁺) with a series

of polar and nonpolar unsaturated organic substrates. In the

subsequent paper we report detailed complementary investiga-

tions using DFT. These combined studies provide for the ﬁrst

time a unique and comprehensive insight into the reaction site

selectivity in polymerization-active transition-metal cations

which contain both MdNR and M-R′ functional groups as

potential sites for 2π + 2π cycloaddition and migratory

insertion, respectively. A part of this work has been com-

municated.⁶⁵

Results and Discussion

The structure of the cation 8⁺is shown in Figure 1, and

selected distances and angles are given in Table 1. The cation

contains an approximately octahedral Ti center supported by a

fac-κ³-coordinated Me₃[9]aneN₃group along with MeCN,

Me₂CN, and Me₃CN ligands. This is the second structurally

authenticated compound containing both a terminal imido and

a ketimido ligand and is the ﬁrst for titanium. Uniquely, it

contains, at the same metal center, the full family of ligands

Reactions with MeCN. As a benchmark probe of the

migratory insertion aptitudes of the Ti-alkyl bonds in

[Ti(N^tBu)(Me₃[9]aneN₃)R]⁺(5⁺, R ) Me; 6⁺, CH₂SiMe₃) we

ﬁrst examined their reactions with MeCN (and also CD₃CN in

the case of 5⁺). MeCN and other organonitriles are well-known

to insert into the metal-alkyl bonds of main-group, transition-

metal and f-element organometallics to form ketimido prod-

ucts.⁶⁸Of particular relevance to our work are Bochmann’s⁶⁹

(65) Bolton, P. D.; Clot, E.; Cowley, A. R.; Mountford, P. Chem.

Commun. 2005, 3313.

(66) Bolton, P. D.; Clot, E.; Adams, N.; Dubberley, S. R.; Cowley, A. R.;

Mountford, P. Organometallics 2006, 25, 2806.

(67) Bolton, P. D.; Clot, E.; Cowley, A. R.; Mountford, P. J. Am. Chem.

Soc. 2006, 128, 15005.

(69) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B.; Motevalli, M.

Organometallics 1988, 7, 1148.

(70) Alelyunas, Y. W.; Jordan, R. F.; Echols, S. F.; Borkowsky, S. L.;

Bradley, P. K. Organometallics 1991, 10, 1406.

(71) Kreuder, C.; Jordan, R. F.; Zhang, H. Organometallics 1995, 14,

2993.

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

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

(68) Ferreira, M. J.; Martin, A. M. Coord. Chem. ReV. 2006, 250, 118,

and references therein.

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6099

having the formula NCMe_n, where n ) 1 (neutral ligand), 2

(monoanionic), 3 (dianionic).

As expected, the Ti-NCMe_ndistances in 8⁺increase with

decreasing bond order. The Ti-NCMe₂(1.860(2) Å) and

Ti-NCMe (2.227(2) Å) distances are within the previously

observed ranges for Ti-NCMe₂and Ti-NCMe bonds.^73,74

However, despite the formal positive charge of the complex,

the Ti-NCMe₃bond distance of 1.755(2) Å is considerably

longer than expected, on the basis of previous structural data,^73,74

and is attributed to the presence of the strongly σ- and

π-donating NCMe₂ligand. The orientation of the NCMe₂ligand

(methyl groups lying in the {Ti(1),N(2),N(3),N(5),N(6)} best-

ﬁt least-squares plane) is consistent with N(2p) f Ti(3d) π

donation also occurring in this plane to give a TidNdCMe₂

“heteroallene” moiety.⁶⁸The two π components of the formal

Ti-N_imidotriple bond therefore use the 3d_πorbitals lying

perpendicular to the {Ti(1),N(2),N(3),N(5),N(6)} plane.

Solutions of the ketimide [Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)-

(NCMe)][BAr^F] (8-BAr^F) are stable for several days at room

Figure 1. Displacement ellipsoid plot (15% probability) of [Ti-

(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)]⁺(8⁺). H atoms are omitted

for clarity.

4

temperature but over extended periods isomerize cleanly to the

corresponding ꢀ-diketiminate [Ti(N^tBu)(Me₃[9]aneN₃){N(H)-

CMeCHCMeN(H)}][BAr^F] (10-BAr^F) in 93% isolated yield

4

(eq 2). This compound has been structurally characterized (see

below), and the NMR spectra are consistent with this. In

1

particular, the H spectrum featured the expected resonances

for the N(H)CMeCHCMeN(H) ligand with a broad singlet of

relative integral 2 H at 6.41 ppm for the N-H protons and a

binomial triplet (⁴J ) 1.9 Hz) of integral 1 H at 4.92 ppm for

the C(Me)CHCMe methine proton, which couples to the two

equivalent N-H protons. These and the ¹³C data correspond

favorably with those for Bercaw’s scandocene derivative Cp*₂Sc-

{N(H)CArCHCArN(H)} (Ar ) 4-C₆H₄OMe). The IR spectrum

of 10-BAr^F₄featured a ν(N-H) band at 3329 cm^-1, which can

also be favorably compared with the band for the scandium

analogue.

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

(N^tBu)(Me₃[9]aneN₃){N(H)CMeCHCMeN(H)}]⁺(10⁺). Carbon-

bound H atoms and CH₂Cl₂of crystallization are omitted. H atoms

are drawn as spheres of arbitrary radius.

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

[Ti(N^tBu)(Me₃[9]aneN₃){N(H)CMeCHCMeN(H)}]⁺(10⁺)

Ti(1)-N(1)

Ti(1)-N(3)

Ti(1)-N(5)

N(5)-C(14)

C(14)-C(15)

N(5)-H(1)

2.393(2)

2.283(2)

2.022(3)

1.315(4)

1.392(6)

0.84(6)

Ti(1)-N(2)

Ti(1)-N(4)

Ti(1)-N(6)

N(6)-C(17)

C(15)-C(17)

N(6)-H(2)

2.293(2)

1.697(5)

2.011(4)

1.304(4)

1.409(6)

0.74(7)

While ꢀ-diketiminato (“nacnac”) ligands are of importance

in transition-metal and lanthanide chemistry,⁷⁵the vast majority

of these are substituted with alkyl or aryl groups on the nitrogen

atoms. Moreover, the rearrangement of a nitrile-ketimide

species to the corresponding ꢀ-diketiminate has not been

previously reported in group 4 chemistry. However, examples

of this process have been previously observed in the reactions

of neutral scandium⁷⁶and chromium⁷⁷cyclopendadienyl alkyls

and likely mechanisms have been discussed.⁷⁶

Ti(1)-N(4)-C(10)

Ti(1)-N(6)-C(17)

168.7(5)

132.0(3)

Ti(1)-N(5)-C(14)

N(5)-Ti(1)-N(6)

129.0(3)

85.95(14)

The cation [Ti(N^tBu)(Me₃[9]aneN₃)({N(H)CMeCHCMeN-

(H)})]⁺(10⁺) features an approximately octahedral titanium

center, with triazacyclononane, imido, and ꢀ-diketiminate

ligands (Figure 2 and Table 2).⁷⁸The Ti-N_imide-C angle of

168.7(5)° and the TidN_imidedistance of 1.697(5) Å are within

the expected ranges for a four-electron-donor tert-butylimido

ligand.^73,74It is interesting to compare the rather unexceptional

TidN_imidedistance in 10⁺with the signiﬁcantly longer distance

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

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

(74) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993, 8,

1–31.

(75) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. ReV. 2002,

102, 3031.

(76) Bercaw, J. E.; Davies, D. L.; Wolczanski, P. T. Organometallics

1986, 5, 443.

(77) Richeson, D. S.; Mitchell, J. F.; Theopold, K. H. Organometallics

1989, 8, 2570.

(78) The tert-butyl group is disordered. We refer here to the major

orientation.

6100 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

Scheme 1. Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺(5⁺, R

in the ketimide isomer 8⁺. The N-bound H atoms were located

in a Fourier difference map and positionally and isotropically

reﬁned.

t

) Me; 6⁺, R ) CH₂SiMe₃) with carbodiimides and BuNCO

There are only two previous examples of crystallographically

characterized complexes containing a N(H)CMeCHCMeN(H)

ligand: one for platinum(4+)⁷⁹and one for zirconium(4+).⁸⁰

Although no other titanium complexes of N(H)CMeCHC-

MeN(H) are known, numerous crystallographically characterized

examples of the more common N-alkyl- and N-aryl-substituted

homologues have been described. For 41 reported examples the

mean Ti-N distance is 2.046 Å, with values ranging from 1.934

to 2.237 Å.^73,74The values of 2.022(3) and 2.011(4) Å for 10⁺

are within this range and are very close to the mean value. The

bond lengths and angles of the ꢀ-diketiminato ligand are in

agreement with previous observations. A cationic titanium imido

“nacnac” complex was reported recently by Mindiola and co-

workers.⁵⁷

Reactions with Isocyanates and Carbodiimides. In contrast

to the situation for organonitriles, 2π + 2π cycloaddition

reactions between titanium imido complexes and isocyanates

and carbodiimides (to form ureate and guanidinate complexes,

respectively) are very well established.^81-86However, as shown

in Scheme 1, reaction of [Ti(N^tBu)(Me₃[9]aneN₃)Me]⁺(5⁺)

with diisopropylcarbodiimide, di-p-tolylcarbodiimide, or tert-

butyl isocyanate gave exclusively in each case the corresponding

Ti-Me migratory insertion product: namely, the amidinates

[Ti(N^tBu)(Me₃[9]aneN₃){MeC(NR)₂}]⁺(11⁺, R ) ⁱPr; 12⁺, R

) Tol) and the amidate [Ti(N^tBu)(Me₃[9]aneN₃){OC(Me)-

N^tBu}]⁺(13⁺). The corresponding reaction between [Ti-

(N^tBu)(Me₃[9]aneN₃)CH₂SiMe₃]⁺(6⁺) and diisopropylcarbo-

Ti(1)-N(4) bond in 14⁺and the different alkyl substituents at

C(5) of the amidinate ligands. The Ti-N_imidodistances are again

signiﬁcantly shorter in 11⁺and 14⁺than in the ketimido cation

8⁺. A number of titanium complexes containing both amidinate

and terminal imido ligands have been reported previously.^86-91

Of particular relevance are the neutral half-sandwich acetamidi-

nate complexes Cp*Ti(NR){MeC(NⁱPr)₂} (R ) ^tBu, 2,6-

C₆H₃Me₂), the isoelectronic and isolobal analogues of 11⁺and

14⁺.^86,89

diimide

afforded

[Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C-

(NⁱPr)₂}]⁺(14⁺). All four reactions were quantitative on the

NMR-tube scale, demonstrating a clear preference for migratory

insertion into the Ti-alkyl bonds rather than cycloaddition to

TidN_imide

,

even in the case of [Ti(N^tBu)(Me₃[9]-

aneN₃)CH₂SiMe₃]⁺(6⁺), in which the steric factors associated

with the Ti-CH₂SiMe₃and TidNCMe₃linkages are very

similar.

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Me]⁺(5⁺) with Internal

Alkynes RCCPh (R ) Ph, SiMe₃). Alkynes also present a

fundamental problem in site selectivity, being well-known to

insert into cationic metal-alkyl bonds (forming σ-vinyl

products)^48,92-96and also to undergo cycloaddition reactions

withgroup4MdNRbondsingeneral,formingazametallacyclobu-

tenes.^{13,17,57,97-103}This is a key step in the group 4 hydroami-

The spectroscopic and other analytical data for all four

insertion products are consistent with the solid-state structures

(see below) and those proposed in Scheme 1. In particular, the

¹H-¹³C HMBC spectra show clear correlations between the

migrated alkyl groups and the quaternary carbons of the newly

formed RC(NR′)₂and OC(Me)N^tBu ligands. The diisopropyl-

carbodiimide insertion products 11-BAr^F₄and 14-BAr^F₄have

been crystallographically authenticated. The molecular structures

of cations 11⁺and 14⁺are shown in Figure 3, and selected

distances and angles are given in Table 3. The metric data all

lie within previously reported ranges for titanium and the ligands

under consideration.^73,74There are no signiﬁcant differences

between the two structures, other than a somewhat longer

(87) Hagadorn, J. R.; Arnold, J. J. Am. Chem. Soc. 1996, 118, 893.

(88) Stewart, P. J.; Blake, A. J.; Mountford, P. Inorg. Chem. 1997, 36,

3616.

(89) Stewart, P. J.; Blake, A. J.; Mountford, P. Organometallics 1998,

17, 3271.

(90) Hagadorn, J. R.; Arnold, J. Organometallics 1998, 17, 1355.

(91) Boyd, C. L.; Clot, E.; Guiducci, A. E.; Mountford, P. Organome-

tallics 2005, 24, 2347.

(79) Brawner, S. A.; Lin, I. J. B.; Kim, J.-H. Inorg. Chem. 1978, 17,

1304.

(80) Franceschini, P. L.; Morstein, M.; Berke, H.; Schmalle, H. W. Inorg.

Chem. 2003, 42, 7273.

(81) Blake, A. J.; McInnes, J. M.; Mountford, P.; Nikonov, G. I.;

Swallow, D.; Watkin, D. J. J. Chem. Soc., Dalton Trans. 1999, 379.

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

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

(92) Eisch, J. J.; Piotrowski, A. M.; Brownstein, S. K.; Gabe, E. J.; Lee,

F. L. J. Am. Chem. Soc. 1985, 107, 7219.

(93) Horton, A. D.; Orpen, A. G. Organometallics 1991, 10, 3910.

(94) Horton, A. D.; de With, J. Organometallics 1997, 16, 5424.

(95) Thorn, M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P. J.

Organomet. Chem. 1999, 591, 148.

(96) Cabrera, L.; Hollink, E.; Stewart, J. C.; Wei, P.; Stephan, D. W.

Organometallics 2005, 24, 1091.

(83) Hanna, T. E.; Keresztes, I.; Lobkovsky, E.; Bernskoetter, W. H.;

Chirik, P. J. Organometallics 2004, 23, 3448.

(84) Ong, T.; Yap, G. P. A.; Richeson, D. A. J. Am. Chem. Soc. 2003,

125, 8100.

(85) Ong, T.; Yap, G. P. A.; Richeson, D. A. Chem. Commun. 2003,

2612.

(97) McGrane, P. L.; Jensen, M.; Livinghouse, T. J. Am. Chem. Soc.

1992, 114, 5459.

(98) McGrane, P. L.; Livinghouse, T. J. Am. Chem. Soc. 1993, 115,

11485.

(99) Bennett, J. L.; Wolczanski, P. T. J. Am. Chem. Soc. 1997, 119,

10696.

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

25, 1167.

(100) Polse, J. L.; Andersen, R. A.; Bergman, R. G. J. Am. Chem. Soc.

1998, 120, 13405.

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6101

Figure 3. Displacement ellipsoid plots (20% probability) of (a) [Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}]⁺(11⁺) and (b)

[Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}]⁺(14⁺). H atoms are omitted for clarity.

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

[Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}]⁺(11⁺) and

[Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}]⁺(14⁺)

from the methyl group protons to the two vinylic carbons and

also to the ipso carbon of one of the phenyl groups. A number

of neutral and cationic group 4 vinyl complexes of the type

L_nMC(R)dCRR′ have been structurally authenticated,^92,93,109

and the ¹³C chemical shifts of the vinylic carbons of 192.2

(Ti-CdC) and 133.7 (CdC(Ph)Me) ppm compare favorably

with the corresponding shifts in the analogous group 4 metal-

locenium cations.⁹³

param

11⁺

14⁺

Ti(1)-N(1)

Ti(1)-N(2)

Ti(1)-N(3)

Ti(1)-N(4)

Ti(1)-N(5)

Ti(1)-N(6)

N(2)-C(5)

N(3)-C(5)

1.718(2)

2.102(2)

2.120(2)

2.465(2)

2.286(2)

2.270(2)

1.337(3)

1.344(3)

1.7085(18)

2.1083(17)

2.1276(16)

2.5252(18)

2.2787(17)

2.2968(17)

1.343(3)

1.341(3)

Ti(1)-N(1)-C(1)

N(2)-C(5)-N(3)

175.7(2)

113.0(2)

177.77(15)

113.92(17)

nation of alkynes by transition metals.^104,105Furthermore, in

the case of terminal alkynes, there is the possibility of C-H

bond activation by attack at either the MdNR^53,100,106or

M-alkyl bonds.¹⁰⁷

The reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Me]⁺(5⁺) with

selected internal alkynes are summarized in eq 3.¹⁰⁸With

PhCCPhthemigratoryinsertionproduct[Ti(N^tBu)(Me₃[9]aneN₃)-

{PhCC(Ph)Me}][BAr^F] (15-BAr^F) was formed in 69% iso-

Reaction of 5⁺with the unsymmetrical internal alkyne

Me₃SiCCPh afforded exclusively [Ti(N^tBu)(Me₃[9]aneN₃)-

{Me₃SiCC(Ph)Me}][BAr^F] (16-BAr^F) in 78% isolated yield

4

lated yield. Although broad at room temperature, at -40 °C

4

1

the H and ¹³C NMR data of 15⁺showed that this complex

(quantitative when followed by NMR in CD₂Cl₂). The C₁

1

symmetrical cation 16⁺has H and ¹³C NMR features similar

possesses C₁symmetry, as indicated for example by three

singlets at 3.21, 3.08, and 2.19 ppm for the macrocycle methyl

groups in the ¹H spectrum. The presence of a C(Ph)dC(Ph)Me

group was conﬁrmed by the observation of long-range couplings

to those of 15⁺, and the connectivity within the Me₃SiCC(Ph)Me

1

fragment was conclusively established by H-¹³C correlation

experiments. A single ²⁹Si NMR resonance was seen at -16.8

ppm. No evidence was found for an alternative isomer in which

the titanium methyl group had migrated to the carbon bearing

the SiMe₃substituent. Although we have not been able to obtain

diffraction-quality crystals of either product, on the basis of the

NMR data and DFT calculations described below, 15⁺and 16⁺

are unequivocally assigned approximately trigonal-bipyramidal

geometries at titanium.

(101) Ward, B. D.; Maisse-Francois, A.; Mountford, P.; Gade, L. H.

Chem. Commun. 2004, 704.

(102) Wang, H.; Chan, H.; Xie, Z. Organometallics 2005, 24, 3772.

(103) Zhao, G.; Basuli, F.; Kilgore, U. J.; Fan, H.; Aneetha, H.; Huffman,

J. C.; Wu, G.; Mindiola, D. J. J. Am. Chem. Soc. 2006, 128, 13575.

(104) Doye, S. Synlett 2004, 1653.

(105) Bytschkov, I.; Doye, S. Eur. J. Org. Chem. 2003, 935.

(106) Polse, J. L.; Kaplan, A. W.; ersen, R. A.; Bergman, R. G. J. Am.

Chem. Soc. 1998, 120, 6316.

The titanium centers in the ﬁve-coordinate 15⁺and 16⁺have

formal 14-valence-electron counts, thus raising the possibility

(107) Hessen, B.; Bol, J. E.; de Boer, J. L.; Meetsma, A.; Teuben, J. H.

J. Chem. Soc., Chem. Commun. 1989, 1276.

(108) Initial NMR-tube studies showed that reactions of 6⁺with internal

and terminal alkynes were not as clean, and so we focused our efforts on

the better behaved system 5⁺.

(109) Crowther, D. J.; Baenziger, N. C.; Jordan, R. F. J. Am. Chem.

Soc. 1991, 113, 1455.

6102 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

Figure 4. Potential agostic interactions in [Ti(N^tBu)(Me₃-

[9]aneN₃){RCC(Ph)Me}]⁺(R ) Ph, SiMe₃), the ꢀ-Si-C agostic

structure of [Cp₂Ti{Me₃SiCC(Ph)Me}]⁺, and a γ-C-H agostic

isomer.⁹²

Figure 5. DFT minimized alternative isomers of [Ti-

(N^tBu)(Me₃[9]aneN₃){Me₃SiCC(Ph)Me}]⁺(16a⁺, 16b⁺) and

[Cp₂Ti{Me₃SiCC(Ph)Me}]⁺(17⁺, 17a⁺). Computed ²⁹Si shifts and

electronic energies relative to the ꢀ-Si-C agostic isomer are given

in parentheses.

of agostic interactions. These could take the form of a γ-C-H

agostic bond from the migrated methyl group (Figure 4, 15a⁺

or 16a⁺), or (for 16⁺) a ꢀ-Si-C interaction, depicted as 16b⁺.

that the titanocenium system 17⁺has a strong preference for a

ꢀ-Si-C agostic structure (-38.4 kJ mol^-1more stable than the

γ-C-H agostic alternative 17a⁺) and that the observed ²⁹Si

resonance (-54.9 ppm) is consistent with this structure (cal-

culated -51.1 ppm). In contrast, 16⁺prefers slightly the γ-C-H

agostic structure (-4.6 kJ mol^-1), and again the observed ²⁹Si

resonance (-16.8 ppm) is consistent with this (calculated -16.0

ppm). The differences in structural preferences are attributed

to the higher electronegativity of titanium and greater ease of

deformation for the [Cp₂TiX]⁺fragment (X ) σ-donor ligand)

compared to the isolobal [Ti(N^tBu)(Me₃[9]aneN₃)X]⁺, as we

have described previously.⁶⁶

Indeed, 16-BAr^Fis related to Eisch’s landmark compound

4

[Cp₂Ti{Me₃SiCC(Ph)Me}][AlCl₄] (17-AlCl₄; cf. Figure 4), the

X-ray structure of which showed a pronounced ꢀ-Si-C agostic

interaction.⁹²Horton has reported analogous reactions of zir-

conocenium methyl cations with Me₃SiCCMe to give ꢀ-Si-C

agostic insertion products.⁹³The high-ﬁeld-shifted ²⁹Si reso-

nances (δ less than -50 ppm) in these were attributed to the

ꢀ-Si-C agostic interactions. Since no ²⁹Si data were reported

for 17⁺, we prepared it on the NMR-tube scale in order to make

a comparison with the data for 16⁺. The sequential reaction of

1

The magnitude of the experimental average J_CHvalue for

Cp₂TiMe₂with [CPh₃][BAr^F] and Me₃SiCCPh afforded 17⁺

4

the Me₃SiCC(Ph)Me methyl in 17⁺(not involved in a γ-C-H

agostic interaction) is 128 Hz, some ca. 4-5 Hz larger than

that in the γ-C-H agostic cations 15⁺(124 Hz) and 16⁺(123

Hz). Similar differences are also found in the average computed

¹J_CHvalues (15a⁺, 113.5 Hz; 16a⁺112.8 Hz; 17⁺, 117.2 Hz),¹¹²

although the absolute magnitudes are underestimated relative

to experiment by ca. 10%, as found previously.^66,67At ﬁrst sight

this suggests that the lower average ¹J_CHvalues in 15⁺and 16⁺

support the presence of γ-C-H agostic ground-state interac-

quantitatively and cleanly, and the ¹H and ¹³C NMR data were

fully consistent with the previously reported X-ray structure.

The ²⁹Si NMR resonance for 17⁺appeared at -54.9 ppm,

consistent with its solid-state geometry and the data reported

by Horton for the zirconocenium systems.⁹³

In contrast to the very upﬁeld ²⁹Si resonances for these

metallocenium systems, the corresponding shift for 16⁺appeared

at only -16.8 ppm. This is comparable to that of free

Me₃SiCCPh itself (δ -18.6 ppm) and organic vinyl-substituted

trimethylsilanes R(R′)CdC(R′′)SiMe₃(range δ -4.3 to -11.5

ppm).^110,111On the other hand, the shift for 16⁺is comparable

to that of [Ti(N^tBu)(Me₃[9]aneN₃)(CH₂SiMe₃)]⁺(6⁺; δ -15.9

ppm), which does contain a ꢀ-Si-C agostic bond.⁶⁶On the basis

of the ²⁹Si NMR data alone, the bonding situation in 16⁺is

somewhat ambiguous. However, we have recently shown how

the combination of DFT (NMR and geometry calculations) and

²⁹Si NMR spectroscopy is a powerful technique to identify

ꢀ-Si-C agostic interactions.⁶⁶To clarify the bonding situation,

models of 16a⁺, 16b⁺, 17⁺, and 17a⁺(Figure 4) were optimized

at the DFT (B3PW91) level and ²⁹Si chemical shifts computed

in the GIAO approximation with IGLO-II type basis sets (see

Computational Details). The DFT minimized structures are

represented in Figure 5 along with the computed ²⁹Si shifts and

the energies relative to the ꢀ-Si-C agostic isomers. It is clear

1

tions.^113-115However, the calculated average J_CHvalues for

the alternative isomers are not that dissimilar (16b⁺, 114.4 Hz;

17a⁺, 117.9 Hz),¹¹⁶with the titanocenium system 17a⁺still

having the higher calculated average ¹J_CHvalue even though it

is now the one with the γ-C-H interaction. Therefore, the ²⁹Si

NMR shifts allow a much better indication of the actual isomer

formed (namely γ-C-H vs. ꢀ-Si-C agostic) than the aVerage

¹J_CHvalues.¹¹⁷

(112) Individual C-H bond values: 15a⁺, 103.6 (H closest to Ti), 115.8,

121.0 Hz; 16a⁺, 95.9 (H closest to Ti), 119.5, 123.0 Hz; 17⁺, 115.7, 117.4,

118.5 Hz.

(113) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg. Chem.

1988, 36, 1.

(114) Clot, E.; Eisenstein, O. Struct. Bonding (Berlin) 2004, 113, 1.

(115) Scherer, W.; McGrady, G. S. Angew. Chem., Int. Ed. 2004, 43,

1782.

(116) Individual C-H bond values: 16b⁺, 109.5, 115.9, 117.7 Hz; 17a⁺,

86.9 (H closest to Ti), 133.2, 133.5 Hz.

(110) Liepio`, E.; Goldberg, Y.; Iovel, I.; Lukevics, E. J. Organomet.

Chem. 1987, 335, 301.

(111) Grignon-Dubois, M.; Laguerre, M. Organometallics 1988, 7, 1443.

(117) The individual ¹J values for the γ-agostic Me groups are of course

very different from those for their nonagostic counterparts, but these values

are not available from the NMR experiments.

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6103

Scheme 2. Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺)

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Me]⁺(5⁺) with

Terminal Alkynes RCCH (R ) Ph, SiMe₃). The reactions of

[Ti(N^tBu)(Me₃[9]aneN₃)Me]⁺(5⁺) with terminal alkynes RCCH

(R ) SiMe₃, Ph) are shown in eq 4.¹⁰⁸These differ strikingly

from those with the internal alkynes RCCPh and the other

substrates discussed so far.

t

i

with BuNCO and PrNCNⁱPr

In each of these cases reaction takes place only at the

TidN^tBu bond to form exclusively the 2π + 2π cycloaddition

products [Ti{^tBuNC(H)CR}(Me₃[9]aneN₃)Me][BAr^F] (R )

4

SiMe₃(18-BAr^F), Ph (19-BAr^F)) in 55-64% isolated yield.

4

These compounds are most efﬁciently prepared at low temper-

ature in CH₂Cl₂and isolated at -78 °C by addition of hexanes.

On standing at room temperature in CD₂Cl₂they convert (t_1/2

) ca. 1 h) to the corresponding chloride cations [Ti{^tBu-

NC(H)CR}(Me₃[9]aneN₃)Cl]⁺, which are described in further

detail below.

group, and so, 7⁺is an ideal system for modeling the potential

reactivity of the TidN^tBu bond in [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺

in the absence of a competing insertion pathway.

The ¹H and ¹³C NMR data for the two cations are comparable

and fully consistent with the C₁-symmetric structures proposed.

The formation of the new N(^tBu)-C(H) bonds was unambigu-

ously conﬁrmed by long-range correlations between the azati-

tanacyclobutene C(H)dC hydrogen atoms and the CMe₃

quaternary atoms of the tert-butyl groups. The C(H)dC

hydrogen atoms in the new compounds appear at δ 11.38 and

11.07 ppm, respectively. These distinctive shifts are comparable

to those found previously for compounds containing a

t

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺with BuNCO

and ⁱPrNCNⁱPr. Addition of ^tBuNCO or ⁱPrNCNⁱPr (1 equiv)

to in situ generated [Ti(N^tBu)(Me₃[9]aneN₃)Cl][BAr^F] (7-

4

BAr^F) in CH₂Cl₂formed [Ti(N^tBu)(Me₃[9]aneN₃)Cl(OCN^t-

4

Bu)][BAr^F] (20-BAr^F) or [Ti(N^tBu)(Me₃[9]aneN₃)(ⁱPrN-

4

CNⁱPr)Cl][BAr^F] (21-BAr^F) in ca. 70% isolated yield (Scheme

4

2). The NMR spectra for the two compounds were sharp and

consistent with C₁symmetry. Both are unstable in solution,

forming mixtures of products after several hours. In contrast,

both the chloride cation 7⁺itself and its pyridine adduct

[Ti(N^tBu)(Me₃[9]aneN₃)Cl(py)]⁺are stable for days in CD₂Cl₂.

For 20⁺the major organic product was identiﬁed as di-tert-

butylcarbodiimide. For 21⁺an organic product could not be

identiﬁed.

1

TiN(R)C(H)dC(R′) ring.^101,102The H shifts for the Ti-Me

groups are -0.51 and -0.29 ppm, consistent with metal-bound

methyl ligands, whereas in the insertion products 15⁺and 16⁺

the migrated methyl groups appear at 2.12 and 1.82 ppm,

respectively. The ²⁹Si shift of -9.7 ppm in 18⁺is consistent

with the SiMe₃group being bound to a vinylic carbon^110,111

and implies that there is no ꢀ-Si-C agostic interaction with

the six-coordinate titanium center. Experimentally, the difference

in reactivity of 5⁺toward internal (insertion into Ti-Me) and

terminal (cycloaddition to TidN^tBu) alkynes appears to be

governed by steric considerations.

t

The formation of BuNCN^tBu is the expected outcome of a

TidN^tBu + ^tBuNCO 2π + 2π cycloaddition reaction followed

by extrusion, forming a “TidO” species and the carbodiimide

via the N,O-bound ureato intermediate [Ti{^tBuNC-

(N^tBu)O}(Me₃[9]aneN₃)Cl]⁺(20a⁺).¹⁷The decomposition of

21⁺could also proceed through the guanidato intermediate

[Ti{^tBuNC(NⁱPr)NⁱPr}(Me₃[9]aneN₃)Cl]⁺(21a⁺).

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺) with

Unsaturated Substrates. The reactions of the imido alkyl

cations 5⁺and 6⁺with the majority of the polar unsaturated

t

substrates investigated (MeCN, carbodiimides, BuNCO, Ph-

CCR) have shown migratory insertion as the preferred pathway.

However, this leaves open the question of whether ﬁve-

coordinate cations of the type [Ti(N^tBu)(Me₃[9]aneN₃)X]⁺could

in fact undergo cycloaddition reactions with these substrates at

the TidN^tBu bond in the absence of a competing Ti-alkyl

group. To address this question, we turned to the in situ

generated monochloride cation [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺

(7⁺), which is formed quantitatively by methide abstraction from

Ti(N^tBu)(Me₃[9]aneN₃)(Me)Cl.⁶⁶Furthermore, the steric re-

quirements of a chloride ligand are similar to those of a methyl

Owing to their instability in solution, we have been unable

to obtain diffraction-quality crystals of 20-BAr^F₄or 21-BAr^F.

4

6104 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

At ﬁrst sight the ¹H data and elemental analyses could be equally

Table 4. Key DFT Calculated and Experimentally Observed

Stretching Frequencies (ν) of Various Species¹²⁷

consistent with the cycloaddition products 20a⁺and 21a⁺

t

discussed above (especially since BuNCN^tBu is one of the

ν_calcd

ν_obsd

species

(cm^-1

2258

)

(cm^-1

)

t

ultimate products from the reaction with BuNCO). A further

^tBuNCO

2258

2357

potential isomer of 20⁺, namely the symmetrically bound N,N-

ureate complex [Ti{^tBuNC(O)N^tBu}(Me₃[9]aneN₃)Cl]⁺(20b⁺),

is inconsistent with the observation of two sets of tert-butyl

group resonances in the NMR spectra. Furthermore, 20b⁺is

[Ti(N^tBu)(Me₃[9]aneN₃)Cl(OCN^tBu)]⁺(20⁺)

MeNCO

2287

2409

2182

1682

1710

[Ti(NMe)(H₃[9]aneN₃)Cl(OCMe)]⁺(20-Oq⁺)

[Ti(NMe)(H₃[9]aneN₃)Cl{N(Me)CO}]⁺(20-Nq⁺)

[Ti{MeNC(NMe)O}(H₃[9]aneN₃)Cl]⁺(20a-q⁺)

[Ti{MeNC(O)NMe}(H₃[9]aneN₃)Cl]⁺(20b-q⁺)

t

not a viable intermediate for the formation of BuNCN^tBu.

The solution ¹³C{¹H} NMR and solid-state IR data for 20-

BAr^Fand 21-BAr^Fsupport their formulation as the unusual

4

were presented, and the complexes were assigned on the basis

of combustion analysis alone. Jain and Rivest reported a titanium

EtNCO σ adduct which featured a band at 1845 cm^-1, probably

indicative of an N-bound adduct.¹²⁶The increased σ-donor

properties of nitrogen versus oxygen account for the general

observation of N-bound isocyanate adducts in the literature.

Therefore, 20-BAr^F₄appears to be the ﬁrst documented example

of an O-bound isocyanate adduct.

σ adducts illustrated in Scheme 2. First the ¹³C NMR shifts of

the imido tert-butyl quaternary carbons (70.9 and 72.0, respec-

tively) are strongly indicative of terminal TidN^tBu groups,

which typically appear at ca. 70 ppm for the types of compound

described herein and at 72.2 ppm for [Ti(N^tBu)-

(Me₃[9]aneN₃)Cl(py)]⁺.⁶⁶It is well-established that heterocu-

mulene cycloaddition to TidN^tBu results in a ca. 10-15 ppm

upﬁeld shift of the quaternary resonance relative to that of the

starting imide.^81,86The corresponding resonance for the coor-

t

dinated BuNCO in 20⁺is observed at 59.2 ppm.

Second, the IR spectra of 20-BAr^Fand 21-BAr^Fshow

4

strong bands at 2357 and 2133 cm^-1, respectively, assigned to

the coordinated heterocumulenes which are shifted to higher

wavenumbers compared to the asymmetric stretches of the free

ligands (2258 and 2114 cm^-1, respectively). In contrast,

cycloaddition products of the type 20a⁺and 21a⁺exhibit

CdNR stretches in the 1620-1750 cm^-1region.^81,86In both

20-BAr^Fand 21-BAr^Fthere is a band around 1643 cm^-1

4

assigned to a mode of the [BAr^F]^-anion invariably present

4

(1641-1643 cm^-1) in all of the species described herein and

also, for example, in [Ti(N^tBu)(Me₃[9]aneN₃)Cl(py)]⁺.⁶⁶The

asymmetric stretch of coordinated carbodiimides has been

reported at 2126-2143 cm^-1in certain palladium σ adducts.¹¹⁸

In the case of 20⁺there is the additional possibility of linkage

isomerism associated with the σ-^tBuNCO ligand which may be

N or O coordinated. It has previously been reported that N

coordination of isocyanates results in a lowering of the

asymmetric stretching frequency compared to the free ligand,¹¹⁹

suggesting that 20⁺is an O-bound adduct, as illustrated in

Scheme 2. Consistent with this hypothesis, no NOE interaction

was observed between the isocyanate methyl protons and those

of the rest of the cation 20⁺.

There are few literature examples of σ adducts of carbodi-

imides and isocyanates, particularly for early transition metals.

Cotton et al. reported the neutral carbodiimide complexes

(RNCN^tBu)₂PdX₂(R ) Me, ^tBu; X ) Cl, Br),¹¹⁸and the X-ray

structure of (^tBuNCN^tBu)₂PdCl₂revealed two σ-bonded car-

bodiimide ligands.¹²⁰Isocyanate π adducts of Co,¹²¹Mo,¹²²and

Ni^123,124are known, but σ adducts are less common. Villa and

Powell have reported isocyanate N-bound σ adducts of Ni(II)

and Cu(II) on the basis of infrared spectroscopic data.¹¹⁹Several

isocyanate adducts of Zr, Mn, Fe, Co, Ni, Cu, and Zn have

been described in the patent literature,¹²⁵but no structural data

To further test our interpretation of 20⁺, we carried out DFT

calculations on selected compounds (Table 4) to obtain com-

puted stretching frequencies for various models of the potential

isomers. These are the O- and N-bound σ-adducts 20-Oq⁺and

20-Nq⁺and the N,O- and N,N-bound ureates 20a-q⁺and 20b-

q⁺. To improve computational efﬁciency for the model σ

adducts, we substituted Me₃[9]aneN₃by the H-substituted

homologue and the tert-butyl groups were replaced by methyl

groups. The computed asymmetric stretch in 20-Oq⁺lies to

higher frequency of free MeNCO, whereas that of the N-bound

isomer 20-Nq⁺appears at a lower frequency. In contrast, both

ureate complexes have ν(CdN) or ν(CdO) values in the ca.

1680-1710 cm^-1range, consistent with previous experimentally

observed values. The DFT results therefore support the structure

(118) Bycroft, B. M.; Cotton, J. D. J. Chem. Soc., Dalton Trans. 1973,

1867.

(119) Villa, J. F.; Powell, H. B. Inorg. Chim. Acta 1979, 32, 199.

(120) Anderson, R. A.; Einstein, F. W. B. Acta Crystallogr. 1978, B34,

271.

(121) Bianchini, C.; Meli, A.; Scapacci, G. Organometallics 1983, 2,

1834.

(122) Minzoni, F.; Pelizzi, C.; Predieri, G. J. Organomet. Chem. 1982,

231, C6.

proposed in Scheme

2

for [Ti(N^tBu)(Me₃[9]aneN₃)Cl-

(OCN^tBu)]⁺(20⁺).

(123) Hoberg, H.; Korff, J. J. Organomet. Chem. 1978, 150, C20.

(124) Mindiola, D. J.; Hillhouse, G. L. Chem. Commun. 2002, 1840.

(125) Wild, H. J. ICI Ltd. U.K., 1962.

(126) Jain, S. C.; Rivest, R. Can. J. Chem. 1965, 43, 787.

(127) Values in parentheses are corrected to V(obsd)/V(calcd) ) 0.9427

t

in accordance with the calculated and observed values for BuNCO.

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6105

Scheme 3. Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺) with

Alkynes

[9]aneN₃)Cl][MeBAr^F] (23-MeBAr^F), with NMR and other

3

data analogous to those of 22⁺and the methyl cation 19⁺. In

contrast, no reaction occurred between 7⁺and PhCCPh,

suggesting that this substrate is too sterically demanding to

couple with the TidN^tBu linkage. The corresponding reaction

with the less sterically encumbered MeCCMe gave a mixture

1

of unknown products when the reaction was followed by H

NMR spectroscopy.

Several examples of the reversible cycloaddition of alkynes

to MdNR linkages have been reported in the literature,^53,57and

we were interested to probe for this in the cycloaddition products

[Ti{^tBuNC(H)CR}(Me₃[9]aneN₃)Cl]⁺. Addition of pyridine (1

equiv) to an NMR-tube sample of 22⁺in CD₂Cl₂afforded no

reaction for at least 16 h. In contrast, [Ti{^tBuNC(H)-

CSiMe₃}(Me₃[9]aneN₃)Cl]⁺(23⁺) reacted immediately with

pyridine, giving free Me₃SiCCH and the known adduct

[Ti(N^tBu)(Me₃[9]aneN₃)Cl(py)]⁺.⁶⁶The difference in behavior

of 22⁺and 23⁺is attributed to the greater steric repulsion

associated with the SiMe₃substituent in the latter.

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺with Alkenes.

Activation of Ti(N^tBu)(Me₃[9]aneN₃)Cl₂with MAO^43,44or of

Ti(N^tBu)(Me₃[9]aneN₃)Me₂with [CPh₃][BAr^F]⁴⁵provides

4

highly productive ethylene polymerization catalysts. The cata-

lytically active species in these systems are proposed to be

monoalkyl cations of the type [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺, with

the imido group acting as spectator ligand. However, as

mentioned, Jensen and Børve have suggested^63,64that the

isolobal, catalytically active bis(imido)chromium cations

[Cr(NR′)₂R]⁺undergo ethylene addition at one of the CrdNR

bonds to provide a modiﬁed catalyst system during the polym-

erization process. In light of these results and the cycloaddition

reactions observed between RCCH and 5⁺and 7⁺, it was clearly

of relevance to probe the reactivity of the TidN^tBu bond in

complexes of the type [Ti(^tBuN)(Me₃[9]aneN₃)X]⁺toward

alkenes.

As a ﬁnal comparison, we carried out analogous calculations

on the model carbodiimide-derived products [Ti(NMe)(H₃[9]ane-

N₃)Cl(MeNCNMe)]⁺(21-q⁺, a model for 21⁺) and the corre-

sponding guanidinate cycloaddition product [Ti{MeNC-

(NMe)NMe}(H₃[9]aneN₃)Cl]⁺(21a-q⁺). The strong asymmetric

stretch of the coordinated MeNCNMe (2191 cm^-1) in 21-q⁺

appears at a frequency higher than that calculated for the free

carbodiimide (2157 cm^-1), whereas 21a-q⁺shows no signiﬁcant

absorption in this region and instead has a strong ν(CdN) band

at 1650 cm^-1. These data again support the assignment of 21⁺

as a σ-bound adduct (ν 2133 cm^-1; cf. 2114 cm^-1for free

ⁱPrNCNⁱPr).

Unfortunately, the high reactivity of the compounds

[Ti(N^tBu)(Me₃[9]aneN₃)R]⁺(R ) Me, CH₂SiMe₃) for ethylene

polymerization prohibited controlled probing of the reactivity

of the TidN^tBu bond. Stoichiometric reactions with styrene or

hexene also yielded mixtures containing alkene oligomers.

However, as established above, the chloride cation

[Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺) provides an alternative basis

for assessing the reactivity of the TidN^tBu linkage itself.

Reactions of 7⁺with ethylene, 1-hexene, and styrene were

carried out on the NMR-tube scale in CD₂Cl₂. In each case no

reaction was observed after 16 h, the resonances observed in

1

the H NMR spectra corresponding to 7⁺and the unreacted

alkene. It is therefore very likely that cationic catalyst systems

derived from Ti(N^tBu)(Me₃[9]aneN₃)Cl₂or Ti(N^tBu)(Me₃[9]-

aneN₃)Me₂do not undergo modiﬁcation of the TidNR bond

during the course of the polymerization process.

Reactions of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺with Alkynes.

Scheme 3 summarizes the reactions of 7⁺with PhCCPh,

PhCCH, and Me₃SiCCH.

Conclusions

As for the reactions with 5⁺, PhCCH reacted smoothly with

Our experimental study of the reactions of the three different

cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺(5⁺, R ) Me; 6⁺, R )

CH₂SiMe₃) and [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺) with a series

of polar and nonpolar unsaturated substrates has provided a

comprehensive evaluation of reaction site selectivity in catalyti-

cally active and well-deﬁned imido alkyl cations. Experimen-

tally, migratory insertion into the Ti-Me bond is almost

exclusively observed, except in the case of certain terminal

alkynes. The reactions of alkyl cations were supplemented by

parallel studies of the otherwise analogous chloride cation 7⁺,

allowing experimental evaluation of the intrinsic TidN^tBu bond

7-BAr^Fto form a cycloaddition product, namely [Ti-

4

{^tBuNC(H)CPh}(Me₃[9]aneN₃)Cl][BAr^F] (22-BAr^F), in 67%

4

yield. The NMR data for 22⁺are analogous to those of the

methyl analogue 18⁺formed from 5⁺. The presence of the

^tBuNC(H)CPh unit was conﬁrmed by a correlation between

the C(H)dC hydrogen atom (11.68 ppm) and the CMe₃carbon

atom (66.6 ppm) and an NOE interaction between this hydrogen

atom and those of the tert-butyl substituent.

The analogous reaction between Me₃SiCCH and 7-MeBAr^F

3

also gave a cycloaddition product, [Ti{^tBuNC(H)CSiMe₃}(Me₃-

6106 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

1276 (m), 1247 (s), 1209 (w), 1188 (w), 1154 (w), 1085 (s, br),

1061 (m), 1005 (s), 981 (s), 776 (s), 757 (m), 746 (w), 684 (m),

662 (m). Anal. Found (calcd for C₄₂H₃₉BF₂₀N₆Ti): C, 47.6 (47.3);

H, 3.8 (3.7); N, 7.5 (7.9).

reactivity in the absence of a competing Ti-alkyl group. A

unique O-bound isocyanate complex was also formed during

these studies, as well as further insights into the characteristics

of ꢀ-Si-C agostic interactions. In the following paper we report

extensive DFT studies which compliment the experimental work

and offer an interpretation of the kinetic and thermodynamic

factors underpinning these titanium imido alkyl and chloride

cations.

[Ti(N^tBu)(Me₃[9]aneN₃){NCMe(CH₂SiMe₃)}(NCMe)][BAr^F] (9-

4

BAr^F). To a solution of Ti(N^tBu)(Me₃[9]aneN₃)(CH₂SiMe₃)₂(4;

4

50 mg, 0.108 mmol) in CH₂Cl₂(2 mL) was added [Ph₃C][BAr^F]

4

(99 mg, 0.108 mmol) in CH₂Cl₂(2 mL). After 5 min MeCN (12.1

µL, 0.237 mmol) was added. The solution was heated to 40 °C for

15 min, during which time the solution changed from orange to

yellow. The solution was concentrated to approximately 1 mL, after

which pentane (2 mL) was added, resulting in a yellow oil. The

mother liquor was decanted away and the oil washed with pentane

(3 × 2 mL). When reduced pressure was applied to the oil, a yellow

powder was obtained. Yield: 74 mg (60%). ¹H NMR (CD₂Cl₂, 499.9

MHz, 293 K): 3.56 (1H, m, NCH₂), 3.41 (1H, m, NCH₂), 3.11

(3H, s, NMe), 3.09 (3H, s, NMe), 2.92-2.85 (3H, overlapping m,

NCH₂), 2.75-2.71 (2H, overlapping m, NCH₂), 2.67 (1H, m,

NCH₂), 2.60-2.45 (4H, overlapping m, NCH₂), 2.36 (3H, s,

NCMe), 2.18 (3H, s, NMe), 1.88 (3H, s, NCMe(CH₂SiMe₃)), 1.80

(2H, br. s, CH₂SiMe₃), 1.03 (9H, s, NCMe₃), 0.16 (9H, s, SiMe₃).

¹³C{¹H} NMR (CD₂Cl₂, 125.7 MHz, 293 K): 166.3

(NCMe(CH₂SiMe₃)), 149.2 (NCMe), 148.2 (br d, ¹J_C-F) 243 Hz,

Experimental Section

General Methods and Instrumentation. All manipulations were

carried out using standard Schlenk line or drybox techniques under

an atmosphere of argon or of dinitrogen. Protio and deuterio 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

1

2

Teﬂon valves. H, ¹³C{¹H}, ¹⁹F, ²⁹Si, and H NMR spectra were

recorded on Varian Mercury-VX 300, Varian Unity Plus 500, and

Bruker AV500 spectrometers. ¹H and ¹³C assignments were

conﬁrmed when necessary with the use of DEPT-135, DEPT-90,

1

and two-dimensional H-¹H and ¹³C-¹H NMR experiments. H

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 spectra were referenced externally

to CFCl₃. ²⁹Si spectra were referenced externally to tetramethyl-

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

in hertz. Infrared spectra were prepared as Nujol mulls between

NaCl plates and were recorded on Perkin-Elmer 1600 and 1710

series FTIR spectrometers. Infrared data are quoted in wavenumbers

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

service of Oxford University’s Department of Chemistry and

elemental analyses by the analytical services of the University of

Oxford Inorganic Chemistry Laboratory or by the Elemental

Analysis Service at the London Metropolitan University.

1

2-C₆F₅)_,138.3 (br d, J_C-F) 245 Hz, 4-C₆F₅), 136.3 (br d, J_C-F

) 245 Hz, 3-C₆F₅), 66.5 (NCMe₃), 56.8 (NCH₂), 56.4 (NCH₂),

55.6 (NCH₂), 54.8 (NCH₂), 54.7 (NCH₂), 53.9 (NCH₂), 53.3 (NMe),

51.7 (NMe), 47.4 (NMe), 34.5 (CH₂SiMe₃), 31.8 (NCMe₃), 28.5

(NCMe(CH₂SiMe₃)), 2.5 (NCMe), -0.7 (SiMe₃). ¹⁹F NMR

(CD₂Cl₂, 282.4 MHz, 293 K): -133.5 (d, ³J ) 10.6, 2-C₆F₅),

3

-164.0 (t, J ) 19.6 Hz, 4-C₆F₅), -167.9 (app t, app J ) 18.1

Hz, 3-C₆F₅). ²⁹Si NMR (HMQC ¹H-observed, 299.9 MHz, 293 K):

0.1 (CH₂SiMe₃). IR (NaCl plates, Nujol mull, cm^-1): 2313 (w),

2285 (w), 1667 (s), 1643 (m), 1514 (s), 1351 (w), 1275 (m), 1241

(s), 1206 (w), 1087 (s), 1005 (m), 980 (s), 841 (m), 775 (s), 757

(m), 726 (w), 684 (m), 662 (m). Anal. Found (calcd for

C₄₅H₄₇BF₂₀N₆SiTi): C, 47.4 (47.5); H, 4.2 (4.2); N, 6.8 (7.4).

Literature Preparations and Other Starting Materials. The

compounds Ti(N^tBu)(Me₃[9]aneN₃)R₂(3, R ) Me (3); 4, R )

CH₂SiMe₃) and Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) were prepared ac-

[Ti(N^tBu)(Me₃[9]aneN₃){N(H)CMeCHCMeN(H)})][BAr^F] (10-

4

BAr^F₄). [Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)][BAr^F₄] (8-

BAr^F₄; 20.0 mg, 0.019 mmol) was dissolved in CD₂Cl₂(0.75 mL).

The reaction was monitored by ¹H NMR spectroscopy. After 7

weeks the ¹H NMR spectrum corresponded to pure 10⁺. The

cording to published methods.^43,45The compounds BAr^Fand

3

[Ph₃C][BAr^F] (Ar^F) C₆F₅) were provided by DSM Research. All

4

other compounds and reagents were purchased and used without

further puriﬁcation.

volatiles were evaporated under reduced pressure to give 10-BAr^F

4

1

[Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)][BAr^F] (8-BAr^F). To

as an orange powder. Yield: 18.5 mg (93%). H NMR (CD₂Cl₂,

4

499.9 MHz, 293 K): 6.41 (2H, br s, NH), 4.92 (1H, t, ⁴J ) 1.9 Hz,

{N(H)C(Me)}₂CH), 3.78 (2H, m, CH₂), 3.18 (6H, s, NMe cis), 3.11

(2H, m, CH₂), 2.82 (2H, m, CH₂), 2.75 (2H, m, CH₂), 2.48 (2H,

m, CH₂), 2.35 (2H, m, CH₂), 2.17 (6H, s, N(H)CMe), 1.81 (3H, s,

NMe trans), 0.88 (9H, s, NCMe₃). ¹³C{¹H} NMR (C₆D₆, 125.7

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

in C₆H₅Cl (2 mL) was added [Ph₃C][BAr^F] (144 mg, 0.156 mmol)

4

in C₆H₅Cl (2 mL) to give a bright orange solution. After 5 min

MeCN (15.9 µL, 0.312 mmol) was added to give a yellow solution.

The solution was concentrated to approximately 1 mL, after which

pentane (4 mL) was added with stirring to give a yellow precipitate.

The precipitate was ﬁltered off, washed with pentane (3 × 2 mL),

and dried in vacuo. Yield: 128 mg (77%). Diffraction-quality single

crystals were obtained by careful layering of a CH₂Cl₂solution

1

MHz, 293 K): 170.1 (N(H)CMe), 148.5 (br d, J_C-F) 240 Hz,

1

2-C₆F₅), 138.6 (br d, J_C-F) 246 Hz, 4-C₆F₅), 136.6 (br d, J_C-F

) 246 Hz, 3-C₆F₅), 96.4 ({N(H)C(Me)}₂CH), 69.2 (NCMe₃), 56.3

(CH₂), 56.1 (CH₂), 53.0 (CH₂), 52.4 (NMe cis), 47.5 (NMe trans),

30.9 (NCMe₃), 28.2 (N(H)CMe). ¹⁹F NMR (CD₂Cl₂, 282.4 MHz,

1

with Me₃SiOSiMe₃. H NMR (CD₂Cl₂, 499.9 MHz, 293 K): 3.57

3

293 K): -133.5 (d, J ) 10.6, 2-C₆F₅), -164.0 (t, J ) 19.6 Hz,

4-C₆F₅), -167.9 (app t, app ³J ) 18.1 Hz, 3-C₆F₅). IR (NaCl plates,

Nujol mull, cm^-1): 3329 (w), 1643 (m), 1552 (m), 1514 (s), 1299

(m), 1276 (m), 1243 (m), 1087 (s), 980 (s), 847 (w), 775 (m), 757

(m), 684 (m), 662 (m). Anal. Found (calcd for C₄₂H₃₉BF₂₀N₆Ti):

C, 47.2 (47.3); H, 3.6 (3.7); N, 7.7 (7.9).

(1H, m, CH₂), 3.41 (1H, m, CH₂), 3.12 (3H, s, NMe), 3.10 (3H, s,

NMe), 2.92-2.85 (3H, overlapping m, CH₂), 2.75-2.71 (2H,

overlapping m, CH₂), 2.67 (1H, m, CH₂), 2.60-2.40 (4H, overlap-

ping m, CH₂), 2.38 (3H, s, NCMe), 2.17 (3H, s, NMe), 1.91 (6H,

s, NCMe₂), 1.01 (9H, s, NCMe₃). ¹³C{¹H} NMR (CD₂Cl₂, 125.7

1

MHz, 293 K): 164.7 (NCMe₂), 148.5 (br d, J_C-F) 243 Hz,

[Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}][BAr^F] (11-BAr^F). To

1

2-C₆F₅), 138.6 (br d, J_C-F) 245 Hz, 4-C₆F₅), 136.6 (br d, J_C-F

) 248 Hz, 3-C₆F₅), 125.7 (NCMe), 66.7 (NCMe₃), 57.1 (CH₂),

56.8 (CH₂), 55.8 (CH₂), 55.1 (CH₂), 55.0 (CH₂), 54.3 (CH₂), 53.7

(NMe), 52.0 (NMe), 47.6 (NMe), 32.0 (NCMe₃), 27.9 (NCMe₂),

2.8 (NCMe). ¹⁹F NMR (CD₂Cl₂, 282.4 MHz, 293 K): -133.1 (d,

³J ) 19.8 Hz, 2-C₆F₅), -165.1 (t, ³J ) 19.8 Hz, 4-C₆F₅), -167.7

4

a stirred solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 100 mg, 0.312

mmol) in C₆H₅Cl (5 mL) was added [Ph₃C][B(C₆F₅)₄] (288 mg,

0.312 mmol) in C₆H₅Cl (5 mL) to give a bright orange solution.

i

After 5 min PrNCNⁱPr (48.9 µL, 0.312 mmol) was added to give

a pink solution. After 1 h the dark orange solution was concentrated

to approximately 5 mL and then pentane (10 mL) was added slowly.

The supernatant was decanted away from the resulting purple oil,

3

(app t, app J ) 19.8 Hz, 3-C₆F₅). IR (NaCl plates, Nujol mull,

cm^-1): 2311 (w), 2281 (w), 1697 (s), 1643 (s), 1514 (s), 1349 (m),

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6107

which was dried in vacuo. The resulting pink powder was ﬁltered

off, washed with pentane (2 × 5 mL), and dried in vacuo. Yield:

199 mg (57%). Diffraction-quality single crystals were obtained

56.6 (CH₂), 55.4 (CH₂), 55.3 (CH₂), 55.1 (CH₂), 53.6 (CNCMe₃),

53.3 (CH₂), 52.7 (NMe), 51.3 (NMe), 47.5 (NMe), 31.7

(TidNCMe₃), 31.6 (CNCMe₃), 21.6 (CMe). ¹⁹F NMR (CD₂Cl₂,

282.1 MHz, 293 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t,

³J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, app ³J ) 18.1 Hz, 3-C₆F₅).

IR (NaCl plates, Nujol mull, cm^-1): 1643 (m), 1621 (m), 1514 (s),

1298 (w), 1275 (m), 1237 (w), 1209 (w), 1087 (s), 1004 (m), 979

(s), 909 (w), 775 (m), 756 (m), 724 (w), 684 (m), 662 (m). Anal.

Found (calcd for C₄₃H₄₂BF₂₀N₅OTi): C, 47.2 (47.7); H, 3.9 (3.9);

N, 6.0 (6.5).

1

by careful layering of a CH₂Cl₂solution with hexane. H NMR

3

(CD₂Cl₂, 299.9 MHz, 293 K): 4.02 (2H, app sept, app J ) 6.8

Hz, CHMe₂), 3.83 (2H, m, CH₂), 3.22 (6H, s, NMe cis), 3.19 (2H,

m, CH₂), 2.86 (4H, overlapping m, CH₂), 2.59 (2H, m, CH₂), 2.46

(2H, m, CH₂), 2.26 (3H, s, CMe), 2.10 (3H, s, NMe trans), 1.42

(6H, d, ³J ) 6.8 Hz, CHMe₂), 1.29 (6H, d, ³J ) 6.8 Hz, CHMe₂),

1.01 (9H, s, NCMe₃). ¹³C{¹H} NMR (CD₂Cl₂, 75.4 MHz, 293 K):

1

[Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}][BAr^F] (14-BAr^F).

167.2 (CMe), 148.5 (br d, J_C-F) 238 Hz, 2-C₆F₅), 138.6 (br d,

4

1

¹J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250 Hz, 3-C₆F₅),

To a stirred solution of Ti(N^tBu)(Me₃[9]aneN₃)(CH₂SiMe₃)₂(4; 100

i

mg, 0.215 mmol) in CH₂Cl₂(10 mL) was added PrNCNⁱPr (34

70.1 (NCMe₃), 57.2 (CH₂), 56.2 (CH₂), 54.4 (CH₂), 52.2 (NMe

cis), 49.8 (CHMe₂), 47.1 (NMe trans), 32.4 (NCMe₃), 25.5

(CHMe₂), 25.4 (CHMe₂), 14.3 (CMe). ¹⁹F NMR (CD₂Cl₂, 282.1

MHz, 293 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t, ³J )

µL, 0.215 mmol) followed by a solution of [Ph₃C][B(C₆F₅)₄] (198

mg, 0.215 mmol) in CH₂Cl₂(20 mL). After 1 h the dark orange

solution was concentrated to approximately 3 mL, and then pentane

(10 mL) was added dropwise. The supernatant was decanted away

from the resulting purple oil, which was redissolved in Et₂O (10

mL); then the solution was concentrated. A microcrystalline pink

solid formed on standing. This was ﬁltered off and dried in vacuo.

Yield: 78 mg (31%). Diffraction-quality single crystals were

3

20.4 Hz, 4-C₆F₅), -167.9 (app t, app J ) 18.1 Hz, 3-C₆F₅). IR

(NaCl plates, Nujol mull, cm^-1): 1643 (m), 1514 (s), 1277 (m),

1229 (w), 1208 (w), 1005 (m), 982 (s), 776 (m), 757 (m), 684 (m),

662 (m). ES⁺MS (MeCN): m/z 431.5 (2%) [M]⁺, 143.1 (100%)

[ⁱPrNHCMeNHⁱPr]⁺. Anal. Found (calcd for C₄₅H₄₇BF₂₀N₆Ti): C,

48.5 (48.7); H, 4.3 (4.3); N, 7.4 (7.6).

1

obtained by slow diffusion of pentane into a CH₂Cl₂solution. H

[Ti(N^tBu)(Me₃[9]aneN₃){MeC(NTol)₂}][BAr^F] (12-BAr^F). To

NMR (CD₂Cl₂, 499.9 MHz, 293 K): 3.96 (2H, app sept, app ³J )

6.6 Hz, CHMe₂), 3.86 (2H, m, NCH₂), 3.26 (6H, s, NMe cis), 3.18

(2H, m, NCH₂), 2.98 (2H, m, NCH₂), 2.86 (2H, m, NCH₂),

2.65-2.50 (4H, overlapping m, NCH₂), 2.25 (2H, s, CH₂SiMe₃),

2.12 (3H, s, NMe trans), 1.41 (6H, d, ³J ) 6.6 Hz, CHMe₂), 1.21

4

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

in C₆H₅Cl (2 mL) was added [Ph₃C][BAr^F] (144 mg, 0.156 mmol)

4

in C₆H₅Cl (2 mL) to give a bright orange solution. After 5 min

p-tolylcarbodiimide (35 mg, 0.156 mmol) was added to give a pink

solution. The solution was concentrated to approximately 1 mL,

and then pentane (4 mL) was added with stirring to give a pink

oil. The supernatant was decanted and the oil washed with pentane

(3 × 2 mL). When reduced pressure was applied to the oil, a pink

3

(6H, d, J ) 6.6 Hz, CHMe₂), 1.01 (9H, s, NCMe₃), 0.16 (9H, s,

SiMe₃). ¹³C{¹H} NMR (CD₂Cl₂, 75.4 MHz, 293 K): 168.5

1

(CCH₂SiMe₃), 148.5 (br d, J_C-F) 238 Hz, 2-C₆F₅), 138.6 (br d,

1

¹J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250 Hz, 3-C₆F₅),

1

powder was obtained. Yield: 108 mg (57%). H NMR (CD₂Cl₂,

70.8 (NCMe₃), 57.5 (NCH₂), 56.6 (NCH₂), 54.2 (NCH₂), 52.4 (NMe

cis), 50.4 (CHMe₂), 47.2 (NMe trans), 32.7 (NCMe₃), 26.4

(CHMe₂), 25.1 (CHMe₂), 17.1 (CH₂SiMe₃), -0.1 (SiMe₃). ¹⁹F NMR

3

299.9 MHz, 293 K): 7.22 (4H, d, J ) 8.1 Hz, 3-C₆H₄Me), 7.04

(4H, d, ³J ) 8.1 Hz, 2-C₆H₄Me), 3.92 (2H, m, CH₂), 3.23 (2H, m,

CH₂), 3.07 (6H, s, NMe cis), 2.80 (2H, m, CH₂), 2.65-2.53 (4H,

overlapping m, CH₂), 2.35 (6H, s, PhMe), 2.33 (2H, m, CH₂), 2.32

(3H, s, NMe trans), 2.05 (3H, s, N₂CMe), 1.17 (9H, s, NCMe₃).

¹³C{¹H} NMR (CD₂Cl₂, 75.4 MHz, 293 K): 166.2 (N₂CMe), 148.5

3

(CD₂Cl₂, 282.1 MHz, 293 K): -133.5 (d, J ) 10.6 Hz, 2-C₆F₅),

3

-164.0 (t, J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, app J ) 18.1

Hz, 3-C₆F₅). ²⁹Si NMR (HMQC ¹H-observed, CD₂Cl₂, 299.9 MHz,

293 K): 2.1 (CH₂SiMe₃). IR (NaCl plates, Nujol mull, cm^-1): 1642

(m), 1513 (s), 1204 (w), 979 (s), 775 (w), 757 (w), 683 (w), 663

(m). ES⁺MS (MeCN): m/z 503.6 (12%) [M]⁺, 215.2 (100%)

[ⁱPrNHC(CH₂SiMe₃)NHⁱPr]⁺, 172.2 (13%) [Me₃[9]aneN₃H]⁺. Anal.

Found (calcd for C₄₈H₅₅BF₂₀N₆SiTi): C, 48.9 (48.8); H, 4.8 (4.7);

N, 7.2 (7.1).

1

(br d, J_C-F) 238 Hz, 2-C₆F₅), 144.4 (1-C₆H₄Me), 138.6 (br d,

1

¹J_C-F) 247 Hz, 4-C₆F₅), 136.6 (br d, J_C-F) 250 Hz, 3-C₆F₅),

134.4 (4-C₆H₄Me), 130.5 (3-C₆H₄Me), 124.4 (2-C₆H₄Me), 70.6

(NCMe₃), 56.4 (CH₂), 56.3 (CH₂), 53.9 (CH₂), 51.6 (NMe cis),

47.3 (NMe trans), 32.5 (NCMe₃), 20.9 (PhMe), 14.6 (N₂CMe). ¹⁹

F

NMR (CD₂Cl₂, 282.1 MHz, 293 K): -133.5 (d, ³J ) 10.6 Hz,

[Ti(N^tBu)(Me₃[9]aneN₃){PhCC(Ph)Me}][BAr^F] (15-BAr^F). To

4

3

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

2-C₆F₅), -164.0 (t, J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, app J

) 18.1 Hz, 3-C₆F₅). IR (NaCl plates, Nujol mull, cm^-1): 1643 (m),

1513 (s), 1413 (s), 1275 (m), 1231 (m), 1087 (s), 1002 (m), 980

(s), 853 (w), 804 (w), 775 (m), 756 (m), 745 (w), 684 (m), 662

(m). Anal. Found (calcd for C₅₃H₄₇BF₂₀N₆Ti): C, 53.1 (52.8); H,

4.0 (3.9); N, 6.5 (7.0).

in C₆H₅Cl (2 mL) was added [Ph₃C][BAr^F] (144 mg, 0.156 mmol)

4

in C₆H₅Cl (2 mL) to give a bright orange solution. After 5 min

PhCCPh (28 mg, 0.156 mmol) was added. The reaction mixture

was stirred for 1 h, during which time it darkened in color. The

deep red solution was concentrated to approximately 1 mL, and

then pentane (4 mL) was added with stirring to give an orange-

brown oil. The supernatant was decanted and the oil washed with

pentane (3 × 2 mL). When reduced pressure was applied to the

oil, a dark orange powder was obtained. Yield: 125 mg (69%). ¹H

NMR (CD₂Cl₂, 499.9 MHz, 233 K): 7.40-7.00 (10H, overlapping

m, C₆H₅)_,4.05 (1H, m, CH₂), 3.99 (1H, m, CH₂), 3.35-2.95 (3H,

overlapping m, CH₂), 3.21 (3H, s, NMe), 3.08 (3H, s, NMe),

2.90-2.70 (4H, overlapping m, CH₂), 2.55-2.45 (3H, overlapping

m, CH₂), 2.19 (3H, s, NMe), 2.12 (3H, s, CMe(Ph)), 1.20 (9H, s,

NCMe₃). ¹³C{¹H} NMR (CD₂Cl₂, 125.7 MHz, 233 K): 192.2 (TiC),

[Ti(N^tBu)(Me₃[9]aneN₃){OC(Me)N^tBu}][BAr^F] (13-BAr^F). To

4

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

in C₆H₅Cl (2 mL) was added [Ph₃C][BAr^F] (144 mg, 0.156 mmol)

4

in C₆H₅Cl (2 mL) to give a bright orange solution. After 5 min

^tBuNCO (17.8 µL, 0.156 mmol) was added to give a red solution.

The solution was concentrated to approximately 1 mL, and then

pentane (4 mL) was added with stirring to give a red oil. The

supernatant was decanted and the oil washed with pentane (3 × 2

mL). When reduced pressure was applied to the oil, a pink powder

was obtained. Yield: 81 mg (48%). ¹H NMR (CD₂Cl₂, 299.9 MHz,

293 K): 4.21 (1H, m, CH₂), 3.68 (1H, m, CH₂), 3.37-2.95 (4H,

overlapping m, CH₂), 3.30 (3H, s, NMe), 3.08 (3H, s, NMe),

2.83-2.27 (6H, overlapping m, CH₂), 2.30 (3H, s, CMe), 2.04 (3H,

s, NMe), 1.51 (9H, s, CNCMe₃), 1.01 (9H, s, TidNCMe₃). ¹³C{¹H}

NMR (CD₂Cl₂, 75.4 MHz, 293 K): 175.5 (CMe), 148.5 (br d, ¹J_C-F

1

148.2 (br d, J_C-F) 243 Hz, 2-C₆F₅), 143.5 (1-C₆H₅), 142.4 (1-

C₆H₅), 138.3 (br d, ¹J_C-F) 245 Hz, 4-C₆F₅), 136.3 (br d, ¹J_C-F

)

245 Hz, 3-C₆F₅), 133.7 (CMe(Ph)), 130.0 (2 or 3-C₆H₅), 128.1 (2

or 3-C₆H₅), 127.8 (2 or 3-C₆H₅), 126.6 (2 or 3-C₆H₅), 125.9 (4-

C₆H₅), 125.4 (4-C₆H₅), 70.6 (NCMe₃), 55.3 (CH₂), 55.2 (CH₂), 54.5

(2 × CH₂), 54.3 (CH₂), 54.0 (CH₂), 52.9 (NMe), 52.4 (NMe), 48.6

(NMe), 31.1 (NCMe₃), 24.0 (CMe(Ph)). ¹⁹F NMR (CD₂Cl₂, 282.1

1

) 238 Hz, 2-C₆F₅), 138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7

1

(br d, J_C-F) 250 Hz, 3-C₆F₅), 70.0 (TidNCMe₃), 57.4 (CH₂),

6108 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

MHz, 233 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t, ³J )

20.4 Hz, 4-C₆F₅), -167.9 (app t, ³J ) 18.1 Hz, 3-C₆F₅). IR (NaCl

plates, Nujol mull, cm^-1): 1643 (s), 1593 (w), 1563 (w), 1514 (s),

1297 (m), 1275 (s), 1233 (s), 1210 (m), 1156 (w), 1086 (s), 1023

(m), 979 (s), 909 (w), 775 (s), 756 (s), 743 (s), 702 (s), 685 (s),

662 (s). Anal. Found (calcd for C₅₂H₄₃BF₂₀N₄Ti): C, 53.7 (53.7);

H, 4.0 (3.7); N, 4.5 (4.8).

overlapping m, CH₂), 2.87 (3H, s, NMe), 2.70-2.54 (3H, overlap-

ping m, CH₂), 2.51-2.38 (2H, overlapping m, CH₂), 1.84 (3H, s,

NMe), 1.57 (9H, s, NCMe₃), 0.19 (9H, s, SiMe₃), -0.51 (3H, s,

TiMe). ¹³C{¹H} NMR (CD₂Cl₂, 75.5 MHz, 213 K): 240.6 (TiC-

(SiMe₃)), 160.5 (CH(N^tBu)), 148.5 (br d, ¹J_C-F) 241 Hz, 2-C₆F₅),

1

138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250

Hz, 3-C₆F₅), 64.0 (NCMe₃), 56.1 (CH₂), 55.3 (CH₂), 55.2 (CH₂),

57.7 (CH₂), 56.8 (CH₂), 56.2 (CH₂), 52.4 (NMe), 50.7 (NMe), 50.1

(NMe), 38.6 (TiMe), 30.8 (NCMe₃), 0.0 (SiMe₃). ¹⁹F NMR

[Ti(N^tBu)(Me₃[9]aneN₃)(Me₃SiCCPhMe)][BAr^F] (16-BAr^F).

4

To a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156

mmol) and Me₃SiCCPh (30.7 µL, 0.156 mmol) in CH₂Cl₂(1 mL)

3

(CD₂Cl₂, 282.1 MHz, 213 K): -133.5 (d, J ) 10.6 Hz, 2-C₆F₅),

3

at -35 °C was added a solution of [Ph₃C][BAr^F] (144 mg, 0.156

-164.0 (t, J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, J ) 18.1 Hz,

3-C₆F₅). ²⁹Si NMR (HMQC ¹H-observed, CD₂Cl₂, 299.9 MHz, 213

K): -9.7 (SiMe₃). IR (NaCl plates, Nujol mull, cm^-1): 1643 (s),

1513 (s), 1412 (m), 1296 (m), 1275 (s), 1253 (m), 1201 (s), 1156

(w), 1085 (s), 978 (s), 893 (w), 851 (s), 837 (s), 775 (s), 756 (s),

684 (s), 662 (s). Anal. Found (calcd for C₄₃H₄₃BF₂₀N₄SiTi · C₆H₁₄):

C, 50.5 (50.4); H, 5.0 (4.9); N, 4.7 (4.8).

4

mmol) in CH₂Cl₂(1 mL). The resulting deep red solution was

immediately cooled to -78 °C, and then hexane (4 mL) was added

with stirring to give an orange oil. The supernatant was decanted

and the oil washed with hexane (3 × 2 mL). When reduced pressure

was applied to the oil, an orange powder was obtained which

1

contained 0.5 equiv of hexane per titanium by H NMR. Yield:

[Ti{^tBuNC(H)CPh}(Me₃[9]aneN₃)Me][BAr^F₄] (19-BAr^F₄). To

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

and PhCCH (17.1 µL, 0.156 mmol) in CH₂Cl₂(1 mL) at -35 °C

147 mg (78%). ¹H NMR (CD₂Cl₂, 299.9 MHz, 233 K): 7.31 (2H,

app t, app ³J ) 8.2 Hz, 3-C₆H₅), 7.24 (1H, t, ³J ) 7.3 Hz, 4-C₆H₅),

3

7.15 (2H, d, J ) 8.2 Hz, 2-C₆H₅), 4.10 (1H, m, CH₂), 3.84 (1H,

was added a solution of [Ph₃C][BAr^F] (144 mg, 0.156 mmol) in

m, CH₂), 3.40-2.74 (8H, overlapping m, CH₂), 3.15 (3H, s, NMe),

3.03 (3H, s, NMe), 2.68-2.44 (2H, overlapping m, CH₂), 2.44 (3H,

s, NMe), 1.82 (3H, s, CMe(Ph)), 1.13 (9H, s, NCMe₃), -0.14 (9H,

s, SiMe₃). ¹³C{¹H} NMR (CD₂Cl₂, 75.5 MHz, 233 K): 205.9 (TiC),

4

CH₂Cl₂(1 mL). The resulting deep red solution was immediately

cooled to -78 °C, and then hexane (4 mL) was added with stirring

to give an orange oil. The supernatant was decanted and the oil

washed with hexane (3 × 2 mL). When reduced pressure was

applied to the oil, an orange powder was obtained which contained

1 equiv of hexane per titanium by ¹H NMR. Yield: 117 mg (64%).

¹H NMR (CD₂Cl₂, 299.9 MHz, 213 K): 11.07 (1H, s, CH(N^tBu)),

1

148.5 (br d, J_C-F) 241 Hz, 2-C₆F₅), 147.4 (1-C₆H₅), 143.9

1

(CMe(Ph)), 138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d,

¹J_C-F) 250 Hz, 3-C₆F₅), 128.0 (3-C₆H₅), 127.1 (2-C₆H₅), 126.5

(4-C₆H₅), 70.3 (NCMe₃), 55.9 (CH₂), 55.3 (CH₂), 54.7 (CH₂), 54.2

(CH₂), 54.1 (2 × CH₂), 52.5 (NMe), 52.2 (NMe), 50.1 (NMe), 31.0

(NCMe₃), 21.3 (CMe(Ph)), 2.4 (SiMe₃). ¹⁹F NMR (CD₂Cl₂, 282.1

MHz, 233 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t, ³J )

20.4 Hz, 4-C₆F₅), -167.9 (app t, ³J ) 18.1 Hz, 3-C₆F₅). ²⁹Si NMR

(HMQC ¹H-observed, CD₂Cl₂, 299.9 MHz, 233 K): -16.8 (SiMe₃).

IR (NaCl plates, Nujol mull, cm^-1): 1643 (s), 1597 (w), 1514 (s),

1297 (w), 1275 (s), 1235 (m), 1087 (s), 980 (s), 853 (m), 775 (s),

757 (s), 726 (w), 703 (w), 684 (m), 662 (m). Anal. Found (calcd

for C₄₉H₄₇BF₂₀N₄SiTi · 0.5C₆H₁₄): C, 51.8 (52.0); H, 4.6 (4.5); N,

4.6 (4.7).

3

7.33 (2H, app t, app J ) 7.6 Hz, 3-C₆H₅), 7.22 (1H, t, J ) 7.4

Hz, 4-C₆H₅), 7.02 (2H, d, ³J ) 7.1 Hz, 2-C₆H₅), 3.70-2.20 (12H,

overlapping m, CH₂), 3.19 (3H, s, NMe), 3.04 (3H, s, NMe), 2.01

(3H, s, NMe), 1.57 (9H, s, NCMe₃), -0.29 (3H, s, TiMe). ¹³C{¹H}

NMR (CD₂Cl₂, 75.5 MHz, 213 K): 224.3 (TiC(Ph)), 158.4

(CH(N^tBu)), 148.5 (br d, ¹J_C-F) 241 Hz, 2-C₆F₅), 145.0 (1-C₆H₅),

1

138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250

Hz, 3-C₆F₅), 128.1 (3-C₆H₅), 127.6 (4-C₆H₅), 125.5 (2-C₆H₅), 63.7

(NCMe₃), 57.6 (CH₂), 57.0 (CH₂), 56.8 (CH₂), 56.7 (CH₂),

56.3(CH₂), 54.9 (CH₂), 51.6 (NMe), 50.8 (NMe), 50.3 (NMe), 39.9

(TiMe), 30.7 (NCMe₃). ¹⁹F NMR (CD₂Cl₂, 282.1 MHz, 213 K):

-133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t, ³J ) 20.4 Hz, 4-C₆F₅),

-167.9 (app t, ³J ) 18.1 Hz, 3-C₆F₅). IR (NaCl plates, Nujol mull,

cm^-1): 1643 (s), 1593 (m), 1514 (s), 1275 (s), 1199 (s), 1087 (s),

979 (s), 893 (w), 757 (s), 726 (w), 700 (m), 684 (s), 662 (s). Anal.

Found (calcd for C₄₆H₃₉BF₂₀N₄Ti · C₆H₁₄): C, 53.1 (53.3); H, 4.7

(4.6); N, 4.8 (4.8).

NMR-Tube-Scale Synthesis of [Cp₂Ti(Me₃SiCCPhMe)][BAr^F]

4

(17-BAr^F). To a solution of [Cp₂TiMe][BAr^F] {generated in situ

4

from Cp₂TiMe₂(7.8 mg, 0.038 mmol) and [Ph₃C][BAr^F] (35.0

4

mg, 0.038 mmol)} in C₆D₅Br (0.75 mL) was added Me₃SiCCPh

(7.4 µL, 0.038 mmol). After 10 min the ¹H NMR spectrum showed

quantitative conversion to 17-BAr^F

.

¹H NMR (C₆D₅Br, 299.9

4

MHz, 293 K): 7.15-6.90 (3- and 4-C₆H₅, obscured by side-product

[Ti(N^tBu)(Me₃[9]aneN₃)(^tBuNCO)Cl][BAr^F₄] (20-BAr^F₄). To

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) (50 mg, 0.147 mmol)

resonances), 6.73 (2H, d, ³J ) 6.5 Hz, 2-C₆H₅), 5.74 (10H, s, Cp),

1

1.26 (3H, s, J_C-H) 128 Hz, TiCCMe), -0.94 (9H, s, SiMe₃).

in CH₂Cl₂(1 mL) was added a solution of [Ph₃C][BAr^F] (135 mg,

¹³C{¹H} NMR (C₆D₅Br, 75.4 MHz, 293 K): 251.0 (TiC), 157.5

4

1

0.147 mmol) in CH₂Cl₂(1 mL). To the resulting orange solution

was added ^tBuNCO (16.8 µL, 0.147 mmol). Me₃SiOSiMe₃(4 mL)

was added with stirring to give a yellow solid, which was ﬁltered

off, washed with Me₃SiOSiMe₃(3 × 2 mL), and dried in vacuo.

The solid contained 0.5 equiv of Me₃SiOSiMe₃by ¹H NMR. Yield:

132 mg (76%). ¹H NMR (CD₂Cl₂, 499.9 MHz, 233 K): 3.76 (1H,

m, CH₂), 3.61 (1H, m, CH₂), 3.30-2.90 (5H, overlapping m, CH₂),

3.18 (3H, s, NMe), 3.13 (3H, s, NMe), 2.86-2.56 (3H, overlapping

m, CH₂), 2.45-2.35 (2H, overlapping m, CH₂), 2.22 (3H, s, NMe),

1.51 (9H, s, CdNCMe₃), 1.01 (9H, s, TidNCMe₃). ¹³C{¹H} NMR

(CD₂Cl₂, 75.5 MHz, 233 K): 148.5 (br d, ¹J_C-F) 241 Hz, 2-C₆F₅),

(TiCC), 148.8 (br d, J_C-F) 239 Hz, 2-C₆F₅), 142.3 (1-C₆H₅),

1

138.6 (br d, J_C-F) 251 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 246

Hz, 3-C₆F₅), 129.0 (3-C₆H₅), 128.1 (4-C₆H₅), 126.7 (2-C₆H₅), 115.3

(Cp), 29.9 (TiCCMe), 3.3 (SiMe₃). ¹⁹F NMR (C₆D₅Br, 282.1 MHz,

3

293 K): -131.8 (d, J ) 10.6 Hz, 2-C₆F₅), -161.8 (t, J ) 21.2

Hz, 4-C₆F₅), -165.8 (app t, app ³J ) 18.1 Hz, 3-C₆F₅). ²⁹Si NMR

(HMQC ¹H-observed, C₆D₅Br, 299.9 MHz, 293 K): -54.9 (SiMe₃).

[Ti{^tBuNC(H)CSiMe₃}(Me₃[9]aneN₃)Me][BAr^F] (18-BAr^F). To

4

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Me₂(3; 50 mg, 0.156 mmol)

and Me₃SiCCH (22 µL, 0.156 mmol) in CH₂Cl₂(1 mL) at -35 °C

was added a solution of [Ph₃C][BAr^F] (144 mg, 0.156 mmol) in

4

1

138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250

Hz, 3-C₆F₅), 70.9 (TidNCMe₃), 59.2 (CdNCMe₃), 56.4 (CH₂), 56.1

(CH₂), 55.6 (2 × CH₂), 53.3 (2 × CH₂), 53.1 (NMe), 52.3 (NMe),

46.7 (NMe), 30.1 (NCMe₃), 30.0 (NCMe₃). ¹⁹F NMR (CD₂Cl₂,

282.1 MHz, 293 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t,

CH₂Cl₂(1 mL). The resulting deep orange solution was immediately

cooled to -78 °C, then hexane (4 mL) was added with stirring to

give an orange oil. The supernatant was decanted and the oil washed

with hexane (3 × 2 mL). When reduced pressure was applied to

the oil, an orange powder was obtained which contained 1 equiv

of hexane per titanium by ¹H NMR. Yield: 100 mg (55%). ¹H NMR

(CD₂Cl₂, 299.9 MHz, 213 K): 11.38 (1H, s, CH(N^tBu)), 3.45-3.30

(2H, overlapping m, CH₂), 3.38 (3H, s, NMe), 3.24-2.87 (5H,

3

³J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, J ) 18.1 Hz, 3-C₆F₅). IR

(NaCl plates, Nujol mull, cm^-1): 2357 (s), 2258 (w), 1643 (m),

1514 (s), 1297 (w), 1276 (m), 1255 (w), 1238 (m), 1087 (s), 1063

TidNR Vs Ti-R′ Functional Group SelectiVity

Organometallics, Vol. 27, No. 23, 2008 6109

(m), 1000 (m), 980 (s), 846 (m), 827 (w), 775 (m), 756 (m), 684

(m), 662 (m). Anal. Found (calcd for C₄₂H₃₉BClF₂₀-

N₅OTi · 0.5C₆H₁₈OSi₂): C, 45.5 (45.6); H, 4.1 (4.1); N, 5.8 (5.9).

give a deep red solution. The volatiles were removed under reduced

pressure to initially yield an orange oil, but on prolonged pumping

23-MeBAr^Fwas obtained as an orange powder. Yield: 50 mg

3

(60%). ¹H NMR (CD₂Cl₂, 499.9 MHz, 293 K): 12.04 (1H, s,

CH(N^tBu)), 3.62-3.50 (2H, overlapping m, CH₂), 3.41 (1H, m,

CH₂), 3.38 (3H, s, NMe), 3.21-2.65 (9H overlapping m, CH₂),

2.94 (3H, s, NMe), 2.18 (3H, s, NMe), 1.62 (9H, s, NCMe₃), 0.44

(3H, br. s, BMe), 0.26 (9H, s, SiMe₃). ¹³C{¹H} NMR (CD₂Cl₂,

75.4 MHz, 293 K): 261.1 (TiC), 162.8 (CH(N^tBu)), 148.6 (br d,

[Ti(N^tBu)(Me₃[9]aneN₃)(ⁱPrNCNⁱPr)Cl][BAr^F₄] (21-BAr^F₄).

To a solution of Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) (50 mg, 0.147

mmol) in CH₂Cl₂(1 mL) was added a solution of [Ph₃C][BAr^F]

4

(135 mg, 0.147 mmol) in CH₂Cl₂(1 mL). To the resulting orange

solution was added ⁱPrNCNⁱPr (23.0 µL, 0.147 mmol).

Me₃SiOSiMe₃(4 mL) was added with stirring to give a yellow

solid, which was ﬁltered off, washed with Me₃SiOSiMe₃(3 × 2

mL), and dried in vacuo. The solid contained 0.5 equiv of

Me₃SiOSiMe₃by ¹H NMR. Yield: 130 mg (73%). ¹H NMR

(CD₂Cl₂, 499.9 MHz, 293 K): 4.33 (1H, sept., ³J ) 6.6 Hz,

1

¹J_C-F) 236 Hz, 2-C₆F₅), 137.7 (br d, J_C-F) 249 Hz, 4-C₆F₅),

136.6 (br d, ¹J_C-F) 246 Hz, 3-C₆F₅), 67.1 (NCMe₃), 58.3 (CH₂),

58.2 (CH₂), 57.9 (CH₂), 57.8 (CH₂), 57.4 (CH₂), 55.5 (CH₂), 53.8

(NMe), 53.6 (NMe), 51.3 (NMe), 31.3 (NCMe₃), 0.6 (SiMe₃). ¹⁹

F

NMR (CD₂Cl₂, 282.1 MHz, 293 K): -133.6 (d, ³J ) 21.2 Hz,

3

CHMe₂), 4.17 (1H, sept, J ) 6.6 Hz, CHMe₂), 3.82-3.72 (2H,

3

overlapping m, CH₂), 3.29 (3H, s, NMe), 3.28 (3H, s, NMe),

3.25-3.14 (2H, overlapping m, CH₂), 3.10 (1H, m, CH₂), 3.03-2.92

(2H, overlapping m, CH₂), 2.90-2.80 (2H, overlapping m, CH₂),

2.75 (1H, m, CH₂), 2.56-2.48 (2H, overlapping m, CH₂), 2.85 (3H,

s, NMe), 1.58 (3H, d, ³J ) 6.6 Hz, CHMe₂), 1.55 (3H, d, ³J ) 6.6

Hz, CHMe₂), 1.47 (3H, d, ³J ) 6.6 Hz, CHMe₂), 1.45 (3H, d, ³J )

6.6 Hz, CHMe₂), 1.15 (9H, s, NCMe₃). ¹³C{¹H} NMR (CD₂Cl₂,

2-C₆F₅), -165.4 (t, J ) 19.6 Hz, 4-C₆F₅), -168.1 (app t, J )

18.1 Hz, 3-C₆F₅). ²⁹Si NMR (HMQC ¹H-observed, CD₂Cl₂, 299.9

MHz, 293 K): -6.4 (SiMe₃). IR (NaCl plates, Nujol mull, cm^-1):

1641 (m), 1511 (s), 1297 (w), 1193 (m), 1157 (w), 1085 (s), 999

(m), 934 (m), 893 (w), 838 (m), 803 (m), 786 (m), 660 (w). Anal.

Found (calcd for C₃₇H₄₃BClF₁₅N₄SiTi): C, 45.0 (46.7); H, 5.8 (4.6);

N, 5.7 (5.9).

1

125.8 MHz, 293 K): 148.2 (br d, J_C-F) 243 Hz, 2-C₆F₅)_,138.3

NMR-Tube-Scale Reaction of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺)

with Ethylene. A solution of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺)

(generated in situ from Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) (7.0 mg,

1

(br d, J_C-F) 245 Hz, 4-C₆F₅), 136.3 (br d, J_C-F) 245 Hz,

3-C₆F₅), 72.0 (NCMe₃), 57.9 (CH₂), 57.8 (CHMe₂), 57.3 (CH₂),

56.7 (CH₂), 56.4 (CH₂), 55.2 (CH₂), 54.7 (CH₂), 54.5 (NMe), 53.0

(NMe), 52.1 (CHMe₂), 48.4 (NMe), 31.3 (NCMe₃), 24.3 (CHMe₂),

24.1 (CHMe₂), 23.7 (CHMe₂), 23.5 (CHMe₂). ¹⁹F NMR (CD₂Cl₂,

282.1 MHz, 293 K): -133.5 (d, ³J ) 10.6 Hz, 2-C₆F₅), -164.0 (t,

0.021 mmol) and BAr^F(10.5 mg, 0.021 mmol)) in CD₂Cl₂(0.75

3

mL) was degassed by three freeze-pump-thaw cycles, and the

headspace of the NMR tube was evacuated. The sample was then

exposed to ethylene at 1.2 bar. A ¹H NMR spectrum recorded after

3

³J ) 20.4 Hz, 4-C₆F₅), -167.9 (app t, J ) 18.1 Hz, 3-C₆F₅). IR

10 min showed resonances for 7-MeBAr^Fand a singlet at 5.40

(NaCl plates, Nujol mull, cm^-1): 2133 (s), 1643 (m), 1611 (w),

1514 (s), 1298 (w), 1276 (m), 1256 (m), 1233 (m), 1087 (s), 1001

(s), 980 (s), 892 (w), 847 (m), 775 (m), 756 (m), 726 (w), 684 (m),

662 (m). Anal. Found (calcd for C₄₄H₄₄BClF₂₀N₆Ti · 0.5C₆H₁₈OSi₂):

C, 46.5 (46.6); H, 4.3 (4.4); N, 6.9 (6.9).

3

ppm corresponding to ethylene. This was essentially unchanged

after 16 h.

NMR-Tube-Scale Reaction of [Ti(N^tBu)(Me₃[9]aneN₃)Cl]⁺(7⁺)

with 1-Hexene and Styrene. To a solution of [Ti(N^tBu)-

(Me₃[9]aneN₃)Cl]⁺(7⁺) (generated in situ from Ti(N^tBu)-

(Me₃[9]aneN₃)Cl(Me) (7.0 mg, 0.021 mmol) and BAr^F₃(10.5 mg,

0.021 mmol)) in CD₂Cl₂(0.75 mL) was added 1-hexene (2.5 µL,

0.021 mmol). A ¹H NMR spectrum recorded after 10 min showed

resonances for 7-MeBAr^F₃and 1-hexene. This was unchanged after

16 h. An analogous result was obtained with styrene.

[Ti{^tBuNC(H)CPh}(Me₃[9]aneN₃)Cl][BAr^F₄] (22-BAr^F₄). To

a solution of Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) (50 mg, 0.147 mmol)

in CH₂Cl₂(1 mL) was added a solution of [Ph₃C][BAr^F] (135 mg,

4

0.147 mmol) in CH₂Cl₂(1 mL). To the resulting orange solution

was added PhCCH (16.1 µL, 0.147 mmol) to give a deep red

solution. Hexane (4 mL) was added with stirring to give a red-

brown oil. The supernatant was decanted and the oil washed with

hexane (3 × 2 mL). When reduced pressure was applied to the oil,

Crystal Structure Determination of [Ti(N^tBu)(Me₃[9]aneN₃)-

(NCMe₂)(NCMe)][BAr^F] (8-BAr^F), [Ti(N^tBu)(Me₃[9]aneN₃)-

4

1

an orange powder was obtained. Yield: 109 mg (67%). H NMR

{N(H)CMeCHCMeN(H)})][BAr^F] · CH₂Cl₂(10-BAr^F₄· CH₂Cl₂),

4

(CD₂Cl₂, 499.9 MHz, 293 K): 11.68 (1H, s, CH(N^tBu)), 7.41 (2H,

[Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}][BAr^F] (11-BAr^F), and

4

app t, app ³J ) 7.8 Hz, 3-C₆H₅), 7.31 (1H, t, ³J ) 7.5 Hz, 4-C₆H₅),

[Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}][BAr^F] (14-BAr^F).

4

3

7.06 (2H, d, J ) 8.2 Hz, 2-C₆H₅), 3.70 (1H, m, CH₂), 3.48 (1H,

Crystal data collection and processing parameters are given in Table

5. Crystals were mounted on a glass ﬁber using perﬂuoropolyether

oil and cooled rapidly to 150 K under a stream of cold N₂using an

Oxford Cryosystems CRYOSTREAM unit. Diffraction data were

measured using an Enraf-Nonius KappaCCD diffractometer. In-

tensity data were processed using the DENZO-SMN package.¹²⁸

The structures were solved using the direct-methods program

SIR92,¹²⁹which located all non-hydrogen atoms. Subsequent full-

matrix least-squares reﬁnement was carried out using the CRYS-

TALS program suite.¹³⁰Coordinates and anisotropic thermal

parameters of all non-hydrogen atoms were reﬁned. Hydrogen atoms

were positioned geometrically. Further details are given in the CIF

data (Supporting Information). Full listings of atomic coordinates,

bond lengths and angles, and displacement parameters have been

deposited at the Cambridge Crystallographic Data Centre.

m, CH₂), 3.20-3.10 (3H, overlapping m, CH₂), 3.13 (3H, s, NMe),

3.09 (3H, s, NMe), 2.99-2.86 (4H, overlapping m, CH₂), 2.83-2.71

(3H, overlapping m, CH₂), 2.38 (3H, s, NMe), 1.62 (9H, s, NCMe₃).

¹³C{¹H} NMR (CD₂Cl₂, 75.5 MHz, 293 K): 238.1 (TiC), 161.8

(CH(N^tBu)), 148.5 (br d, ¹J_C-F) 241 Hz, 2-C₆F₅), 145.4 (1-C₆H₅),

1

138.6 (br d, J_C-F) 247 Hz, 4-C₆F₅), 136.7 (br d, J_C-F) 250

Hz, 3-C₆F₅), 129.0 (3-C₆H₅), 127.9 (4-C₆H₅), 126.2 (2-C₆H₅), 66.6

(NCMe₃), 58.4 (CH₂), 58.2 (CH₂), 57.7 (CH₂), 57.6 (CH₂), 57.5

(CH₂), 55.9 (CH₂), 53.8 (NMe), 52.7 (NMe), 51.4 (NMe), 31.3

3

(NCMe₃). ¹⁹F NMR (CD₂Cl₂, 282.1 MHz, 293 K): -133.5 (d, J

) 10.6 Hz, 2-C₆F₅), -164.0 (t, ³J ) 20.4 Hz, 4-C₆F₅), -167.9

(app t, ³J ) 18.1 Hz, 3-C₆F₅). IR (NaCl plates, Nujol mull, cm^-1):

1643 (m), 1514 (s), 1275 (m), 1195 (w), 1156 (w), 1087 (s), 997

(m), 979 (s), 787 (m), 775 (m), 725 (w), 700 (w), 684 (m), 662

(m). Anal. Found (calcd for C₄₅H₃₆BClF₂₀N₄Ti): C, 48.8 (48.8);

H, 3.3 (3.3); N, 4.9 (5.1).

[Ti{^tBuNC(H)CSiMe₃}(Me₃[9]aneN₃)Cl][MeBAr^F₃] (23-Me-

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

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

(129) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.;

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

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

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

BAr^F). To a solution of Ti(N^tBu)(Me₃[9]aneN₃)Cl(Me) (30 mg,

3

0.088 mmol) in CH₂Cl₂(0.5 mL) was added a solution of BAr^F

3

(45 mg, 0.088 mmol) in CH₂Cl₂(0.5 mL). To the resulting light

orange solution was added Me₃SiCCH (12.4 µL, 0.088 mmol) to

6110 Organometallics, Vol. 27, No. 23, 2008

Bolton et al.

Table 5. X-ray Data Collection and Processing Parameters for [Ti(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)][BAr^F₄] (8-BAr^F₄),

[Ti(N^tBu)(Me₃[9]aneN₃){N(H)CMeCHCMeN(H)}][BAr^F₄] · CH₂Cl₂(10-BAr^F₄· CH₂Cl₂), [Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}][BAr^F₄] (11-BAr^F₄),

and [Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}][BAr^F₄] (14-BAr^F

)

4

8-BAr^F

10-BAr^F₄· CH₂Cl₂

11-BAr^F

14-BAr^F

4

empirical formula

C

₄₂H₃₉BF₂₀N₆Ti

C

₄₃H₄₁BCl₂F₂₀N₆Ti

C₄₅H₄₇BF₂₀N₆Ti

C₄₈H₅₅BF₂₀N₆SiTi

fw

temp/K

1066.48

150

1151.42

150

1110.58

150

1182.76

150

wavelength/Å

space group

0.710 73

P1

0.710 73

P1

0.710 73

P2₁/n

0.710 73

P1

j

a/Å

b/Å

c/Å

11.6237(2)

12.7345(3)

17.5683(4)

110.7643(8)

100.4617(9)

102.2640(10)

2280.25(9)

2

12.3574(2)

14.2186(2)

14.5834(2)

86.5110(6)

85.6190(6)

74.5440(7)

2460.30(6)

2

19.1070(2)

13.2045(2)

20.4267(3)

90

113.4938(7)

90

4726.40(11)

4

1.561

11.9619(2)

12.7619(2)

17.9840(2)

75.5723(5)

80.1952(5)

86.9238(5)

2619.78(7)

2

R/deg

ꢀ/deg

γ/deg

V/Å³

Z

d(calcd)/Mg m^-3

abs coeff/mm^-1

R indices (I > 3σ(I))^a

R1

1.553

0.309

1.554

0.398

1.499

0.299

0.301

0.0513

0.0660

0.0506

0.0632

0.0414

0.0485

0.0402

0.0476

wR2

^aR1 ) ∑||F_o| - |F_c||/∑|F_o|; wR2 ) [∑w(|F_o| - |F_c|)²/∑w|F_o|²]^1/2

.

Computational Details. All the calculations have been per-

formed with the Gaussian03 package¹³¹at the B3PW91 level.^132,133

The titanium atom was represented by the relativistic effective core

potential (RECP) from the Stuttgart group (12 valence electrons)

and its associated basis set,¹³⁴augmented by an f polarization

function (R ) 0.869).¹³⁵The silicon atom was represented by RECP

from the Stuttgart group and the associated basis set,¹³⁶augmented

by a d polarization function.¹³⁷The remaining atoms (C, H, N, O)

were represented by a 6-31G(d,p) basis set.¹³⁸Full optimizations

of geometry without any constraint were performed, followed by

analytical computation of the Hessian matrix to conﬁrm the nature

of the located extrema as minima on the potential energy surface.

NMR chemical shift and J_CHcoupling constants were computed

using the GIAO method^139,140at the B3PW91 level. For the NMR

parameters, all-electron calculations were considered where the basis

set for Ti was the TZP basis set of Ahlrichs¹⁴¹and all the other

atoms were described with the IGLO-II basis set.¹⁴²

Acknowledgment. We thank the EPSRC (P.D.B.), CNRS

(E.C.), Egide and the British Council (E.C. and P.M.), and

the MESR and the Spanish Ministerio de Educacio´n y

Ciencia (M.F.) for support and Dr. C. L. Boyd for some

preliminary experiments.

Supporting Information Available: CIF ﬁles giving X-ray

crystallographic data for the structure determinations of [Ti-

(N^tBu)(Me₃[9]aneN₃)(NCMe₂)(NCMe)][BAr^F]( 8-BAr^F),[Ti(N^tBu)-

4

(Me₃[9]aneN₃){N(H)CMeCHCMeN(H)})][BAr^F₄] · CH₂Cl₂(10-

BAr^F₄· CH₂Cl₂), [Ti(N^tBu)(Me₃[9]aneN₃){MeC(NⁱPr)₂}][BAr^F]

4

(131) Pople, J. A. Gaussian 03, Revision C.02; Gaussian, Inc., Wall-

ingford, CT, 2004.

(132) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.

(133) Perdew, J. P.; Wang, Y. Phys. ReV. B 1992, 45, 13244.

(134) Andrae, D.; Haussermann, U.; Dolg, M.; Stoll, H.; Preuss, H.

Theor. Chim. Acta 1990, 77, 123.

(135) Ehlers, A. W.; Bohme, M.; Dapprich, S.; Gobbi, A.; Hollwarth,

A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.

Chem. Phys. Lett. 1993, 208, 111.

(136) Bergner, A.; Dolg, M.; Kuchle, W.; Stoll, H.; Preuss, H. Mol.

Phys. 1993, 30, 1431.

(11-BAr^F₄), and [Ti(N^tBu)(Me₃[9]aneN₃){Me₃SiCH₂C(NⁱPr)₂}]-

[BAr^F] (14-BAr^F₄) and text and tables giving the complete

4

reference for Gaussian 03 and DFT computed Cartesian coordinates

for the optimized molecules and their electronic energies. This

material is available free of charge via the Internet at http://pubs.

acs.org.

OM800709F

(137) Hollwarth, A.; Bohme, H.; Dapprich, S.; Ehlers, A. W.; Gobbi,

A.; Jonas, V.; Kohler, K. F.; Stagmann, R.; Veldkamp, A.; Frenking, G.

Chem. Phys. Lett. 1993, 203, 237.

(138) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213.

(139) Lee, A. M.; Handy, N. C.; Colwell, S. M. J. Chem. Phys. 1995,

103, 10095.

(141) Scha¨fer, A.; Huber, C.; Ahlrichs, R. J. Chem. Phys. Lett. 1994,

100, 5829.

(142) Kutzelnigg, W.; Fleischer, U.; Schindler, M. The IGLO-Method:

Ab Initio Calculation and Interpretation of NMR Chemical Shifts and

Magnetic Susceptibilities; Springer-Verlag: Heidelberg, Germany, 1990; Vol.

23.

(140) Ditchﬁled, R. J. Chem. Phys. Lett. 1972, 56, 5688.

Article Doi

Ti=NR vs Ti-R′ functional group selectivity in titanium imido alkyl cations from an experimental perspective

DOI: 10.1021/om800709f

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om800709f

Full text of DOI:10.1021/om800709f

Products guided by the article

R&D Labs maybe for 1079390-87-6

Relevant to this article

Hot Product