B(C6F5)3 as C6F5 transfer agent in zirconium chemistry: Borole sandwich and borole-bridged triple-decker complexes

Article abstract of DOI:10.1021/om010348i

Treatment of Cp″Zr(C₆F₅)(OEt₂) {η⁵-(3-RC₄H₃BC₆F₅)} (1H, R = H; 1Me, R = Me; Cp″ = 1,3-C₅H₃ (SiMe₃)₂) in toluene with nitriles R′CN gives rise to the adducts Cp″Zr(C₆F₅)-(NCR′) {η⁵-(3-RC₄H₃BC₆F₅)} (2H, R = H, R′ = Me; 3H, R = H, R′ = tBu; 3Me, R = Me, R′ = tBu) in high yields. The reaction of 1H and 1Me with a 4-fold excess of tert-butylisocyanide in toluene at -20°C leads to the formation of Cp″Zr(C₆F₅)(CNtBu)₂ {η⁵-(3-RC₄H₃BC₆F₅)} (4H, R = H; 4Me, R = Me), while warming to room temperature results in the insertion of one molecule of isocyanide into the zirconium-C₆F₅ bond to give the η²-iminoacyl complexes Cp″Zr{η²-(C₆F₅CNtBu)}(CNtBu) {η⁵-(3-RC₄H₃ BC₆F₅)} (5H, R = H; 5Me, R = Me). The structures of 3H and 5H were confirmed by X-ray diffraction. The reaction of the diene complexes Cp^RZr(η³-crotyl)(η⁴-butadiene) (6a, Cp^R = C₅H₄SiMe₃; 6b, C₅H₄Me; 6c, Cp; 6d, Cp″) with B(C₆F₅)₃ in toluene solution at room temperature proceeds quantitatively with C-H activation, butene elimination, and C₆F₅ transfer to generate Cp^RZr(C₆F₅){η⁴-CH₂CHC HCHB(C₆F₅)₂} (7a-d). These boryldiene complexes are thermally unstable and smoothly rearrange to give the triple-decker complexes Zr₂(Cp^R)₂(C₆ F₅)₂ {μ-η⁵:η⁵- C₄H₄BCH₂-η³,κF-CHCHCHB (C₆F₅)₃} (8a-d). The formation of these complexes involves the complete transfer of all three C₆F₅ substituents of one B(C₆F₅)₃ molecule, as well as C-H activation and the loss of one C₆F₅ group as pentafluorobenzene. The triple-decker complexes feature a Zr₂ C₄B core, a zwitterionic structure, and an unusually strong Zr-F donor interaction. On activation with methylalumoxane (MAO), 8a-d polymerize ethene.

Full text of DOI:10.1021/om010348i

4080
Organometallics 2001, 20, 4080-4091
B(C6F 5)3 a s C6F 5 Tr a n sfer Agen t in Zir con iu m Ch em istr y:
Bor ole Sa n d w ich a n d Bor ole-Br id ged Tr ip le-Deck er
Com p lexes
Timothy J . Woodman,† Mark Thornton-Pett,‡ David L. Hughes,† and
Manfred Bochmann*,†
Wolfson Materials and Catalysis Centre, School of Chemical Sciences,
University of East Anglia, Norwich, U.K., NR4 7TJ , and School of Chemistry,
University of Leeds, Leeds, U.K., LS2 9J T
Received April 30, 2001
Treatment of Cp′′Zr(C6F5)(OEt2){η5-(3-RC4H3BC6F5)} (1H, R ) H; 1Me, R ) Me; Cp′′ )
1,3-C5H3(SiMe3)2) in toluene with nitriles R′CN gives rise to the adducts Cp′′Zr(C6F5)-
(NCR′){η5-(3-RC4H3BC6F5)} (2H, R ) H, R′ ) Me; 3H, R ) H, R′ ) tBu; 3Me, R ) Me, R′ )
tBu) in high yields. The reaction of 1H and 1Me with a 4-fold excess of tert-butylisocyanide
in toluene at -20 °C leads to the formation of Cp′′Zr(C6F5)(CNtBu)2{η5-(3-RC4H3BC6F5)}
(4H, R ) H; 4Me, R ) Me), while warming to room temperature results in the insertion of
one molecule of isocyanide into the zirconium-C6F5 bond to give the η2-iminoacyl complexes
Cp′′Zr{η2-(C6F5CNtBu)}(CNtBu){η5-(3-RC4H3BC6F5)} (5H, R ) H; 5Me, R ) Me). The
structures of 3H and 5H were confirmed by X-ray diffraction. The reaction of the diene
complexes CpRZr(η3-crotyl)(η4-butadiene) (6a , CpR ) C5H4SiMe3; 6b, C5H4Me; 6c, Cp; 6d ,
Cp′′) with B(C6F5)3 in toluene solution at room temperature proceeds quantitatively with
C-H activation, butene elimination, and C6F5 transfer to generate CpRZr(C6F5){η4-
CH2CHCHCHB(C6F5)2} (7a -d ). These boryldiene complexes are thermally unstable and
smoothly rearrange to give the triple-decker complexes Zr2(CpR)2(C6F5)2{µ-η5:η5-C4H4BCH2-
η3,κF-CHCHCHB(C6F5)3} (8a -d ). The formation of these complexes involves the complete
transfer of all three C6F5 substituents of one B(C6F5)3 molecule, as well as C-H activation
and the loss of one C6F5 group as pentafluorobenzene. The triple-decker complexes feature
a Zr2C4B core, a zwitterionic structure, and an unusually strong Zr-F donor interaction.
On activation with methylalumoxane (MAO), 8a -d polymerize ethene.
In tr od u ction
half-sandwich zirconium 1,3-diene complexes such as
Cp′′Zr(η3-crotyl)(η4-butadiene) and Cp′′Zr(η3-allyl)(η4-
isoprene) react with B(C6F5)3 to produce the borole
complexes Cp′′Zr(C6F5)(OEt2){η5-(3-RC4H3BC6F5)} (1H,
R ) H; 1Me, R ) Me) as the products of successive C-H
activation steps within the metal coordination sphere.4
This reaction seems to be specific to bulky cyclopenta-
dienyl ligands such as Cp′′. As reported in a preliminary
communication,5 we subsequently found that under
subtly different conditions 6d follows a different reaction
path, to give the zirconium triple-decker Zr2Cp′′2-
(C6F5)2{µ-η5:η5-C4H4BCH2-η3,κF-CHCHCHB(C6F5)3}, 8d,
featuring a novel ansa-borole-allyl ligand. We now
report the synthesis of related triple-decker complexes
with a variety of cyclopentadienyl ligands, as well as
some stoichiometric and catalytic reactions of these
borole complexes.
Early transition complexes of the borole dianion
[C4H4BR]2- have attracted attention as potential alkene
polymerization catalysts.1 Two general synthetic strate-
gies have been employed: the dehydrogenation of 2,5-
dihydro-1H-boroles with various transition metal com-
pounds2 and the reaction of metal halides with a
preformed borole dianion.3 We recently reported that
* Corresponding author. E-mail: m.bochmann@uea.ac.uk.
† University of East Anglia.
‡ University of Leeds.
(1) (a) Quan, R. W.; Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.;
Bercaw, J . E. J . Am. Chem. Soc. 1994, 116, 4489. (b) Pastor, A.; Kiely,
A. F.; Henling, L. M.; Day, M. W.; Bercaw, J . E. J . Organomet. Chem.
1997, 528, 65. (c) Bazan, G. C.; Donnelly, S. J .; Rodriguez, G. J . Am.
Chem. Soc. 1995, 117, 2671. (d) Bazan, G. C.; Rodriguez, G. Polyhedron
1995, 14, 93. (e) Sperry, C. K.; Cotter, W. D.; Lee, R. A.; Lachicotte, R.
J .; Bazan, G. C. J . Am. Chem. Soc. 1998, 120, 7791.
(2) (a) Herberich, G. E.; Hessner, B.; Boveleth, W.; Lu¨the, H.; Saive
R.; Zelenka, L. Angew. Chem., Int. Ed. Engl. 1983, 22, 1024. (b)
Herberich, G. E.; Negele, M.; Ohst, H. Chem. Ber. 1991, 124, 25. (c)
Herberich, G. E.; Carstensen, T.; Klaff, N.; Neuschu¨tz, M. Chem. Ber.
1992, 125, 1801. (d) Enders, M.; Pritzkow, H.; Siebert, W. Chem. Ber.
1992, 125, 1981. (e) Herberich, G. E.; Carstensen, T.; Englert, U. Chem.
Ber. 1992, 125, 2351. (f) Braunstein, P.; Englert, U.; Herberich, G. E.;
Neuschu¨tz, M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1010. (g)
Herberich, G. E.; Carstensen, T.; Koffer, D. P. J .; Klaff, N.; Boese, R.;
Hylakryspin, I.; Gleiter, R.; Stephan, M.; Meth, H.; Zenneck, U.
Organometallics 1994, 13, 619. (h) Herberich, G. E.; Eckenrath, H. J .;
Englert, U. Organometallics 1997, 16, 4292.
(3) (a) Herberich, G. E.; Hostalek, M.; Laven, R.; Boese, R. Angew.
Chem., Int. Ed. Engl. 1990, 29, 317. (b) Herberich, G. E.; Englert, U.;
Hostalek, M.; Laven, R. Chem. Ber. 1991, 124, 17. (c) Herberich, G.
E.; Eigendorf, U.; Englert, U. Chem. Ber. 1993, 126, 1397. (d)
Herberich, G. E.; Marx, H. W.; Wagner, L. T. Chem. Ber. 1994, 127,
2135. (e) Herberich, G. E.; Wagner, T.; Marx, H. J . J . Organomet.
Chem. 1995, 502, 67.
(4) J ime´nez Pindado, G.; Lancaster, S. J .; Thornton-Pett, M.; Boch-
mann, M. J . Am. Chem. Soc. 1998, 120, 6816.
(5) Woodman, T. J .; Thornton-Pett, M.; Bochmann, M. Chem.
Commun. 2001, 329.
10.1021/om010348i CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/10/2001

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4081
Sch em e 1
Resu lts a n d Discu ssion
the diethyl ether ligand readily dissociates in benzene
solution, the nitrile ligands remain coordinated. All
three complexes are chiral. As in the case of 1Me, the
methyl substituent on the borole ligand in 3Me leads
to the formation of two diastereomers in an approximate
ratio of 1:0.6 at room temperature. It is of note that this
ratio is very similar to that observed for 1Me at -50
°C; however, since the ether ligand in this complex
undergoes rapid exchange at room temperature, it
seems likely that any correlation is merely coincidental
and does not provide information concerning a possible
reaction mechanism. The 19F NMR spectra at room
temperature show two peaks for the ortho-F of the
zirconium-C6F5 ligand, indicative of hindered rotation.
By contrast, the borole-C6F5 group shows only one o-F
peak at this temperature. As with 1H and 1Me, the 11B
NMR spectra of the complexes show broad peaks around
δ 30-40, which are low-field shifted by some 10-20 ppm
compared to C6H5-substituted boroles,2a,c,e,g,h possibly a
reflection of the stronger electron-withdrawing charac-
teristics of the perfluorophenyl substituent, although it
should be noted that these examples are all d6 to d10
Reactivity of Bor ole Com plexes. Mixtures of mono-
nuclear borole complexes of type 1 with trimethyl-
aluminum show good activity as ethene polymerization
catalysts, and the formation of zirconium methyl species
following C6F5/CH3 exchange has been suggested.4 The
propensity of the Zr-C6F5 ligand to undergo exchange
with alkylating agents was therefore explored further,
in an effort to generate isolable 14-electron zirconium
alkyl complexes that might be suitable as single-
component catalysts for olefin polymerizations. While
SnMe4, Sn(allyl)4, and B(allyl)3 failed to react with 1H
and 1Me, Grignard reagents such as benzyl- and
allylmagnesium chloride led to a color change from dark
red to yellow-orange. These reactions were accompanied
by a change in the borole 11B NMR chemical shift from
δ 40 to 25, indicative of an exchange of the B-C6F5 as
well as the Zr-C6F5 substituents. With methyllithium
or ZnMe2 there was evidence for preferential methyl-
ation on zirconium to give yellow solids. However, none
of these reactions allowed the isolation of clean products.
In an effort to further elucidate the reactivity of the
Zr-C6F5 bond, the reactions of complexes 1 with nitriles
and isocyanides were examined. Treatment of toluene
solutions of 1H with acetonitrile and of 1H and 1Me
with pivalonitrile produces rapid color changes from red
to deep purple or blue. Removal of the volatiles from
these solutions and recrystallization from light petro-
leum or toluene provides Cp′′Zr(C6F5)(NCR′){η5-(3-
RC4H3BC6F5)} (2H, R ) H, R′ ) Me; 3H, R ) H, R′ )
tBu; 3Me, R ) Me, R′ ) tBu) as purple to blue solids
(Scheme 1). 1H and 13C NMR data for all new complexes
are collected in Table 1, and 19F NMR data (where
applicable) in Table 2. Unlike the ether adducts, where
(6) A reviewer suggested that a comparison of 11B NMR chemical
shifts with d0 complexes featuring “innocent” organic boron substitu-
ents such as B-Me might be more appropriate than with 1-phenylborole
complexes of d6-d10 metals. However, due to the lack of π-conjugation,
B-Me compounds tend to be found at lower field than related B-Ph
and even B-C6F5 compounds and represent an electronically different
environment. For complexes with methyl-substituted boroles and
boratabenzenes see for example: Grigsby, W. J .; Power, P. P. J . Am.
Chem. Soc. 1996, 118, 7981. Herberich, G. E.; Englert, U.; Schmitz,
A. Organometallics 1997, 16, 3751.
(7) (a) Durfee, D. L.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059. (b)
Singleton, E.; Oosthuizen, H. E. Adv. Organomet. Chem. 1983, 22, 209.
(c) Maitlis, P. M.; Espinet, P.; Russell, M. J . H. In Comprehensive
Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E.,
Eds.; Pergamon: London, 1982; Vol. 8, Chapter 38.4.

4082 Organometallics, Vol. 20, No. 19, 2001
Ta ble 1. 1H a n d 13C NMR Da ta for New Com p lexesa
1H NMR
Woodman et al.
13C NMR
complex
δ
assgnt
δ
assgnt
Cp′′Zr(C6F5)(NCMe)
{η5-C4H4BC6F5}, 2H
-0.02, 0.11 (s, 9 H each)
0.99 (s, 3 H)
SiMe3
NCMe
-0.90, -0.47
0.88
both SiMe3
NCMe
(C6D6, 1,2-difluorobenzene, 20 °C)
5.87 (m, 1 H)
6.07 (m, 1 H)
6.28 (m, 1 H)
6.31 (m, 1 H)
6.37 (t, 1 H, J ) 1.89)
6.43 (m, 1 H)
6.53 (m, 1 H)
-0.07, 0.12 (s, 9 H each)
0.67 (s, 9 H)
5.90 (m, 1 H)
o-C4H4B
o-C4H4B
m-C4H4B
4,5-Cp′′H
2-Cp′′H
4,5-Cp′′H
m-C4H4B
SiMe3
115.09
117.72
120.04
121.99
129.42
m-C4H4B
m-C4H4B
4,5-Cp′′
4,5-Cp′′
2-Cp′′
(o-C4H4B carbons not observed due to poor
solubility and broadening of B nucleus)
-0.59, 0.01
26.24
114.73
115.4 (v br)
119.01
119.81
119.9 (v br)
121.94
129.61
Cp′′Zr(C6F5)(NCtBu)
{η5-C4H4BC6F5}, 3H
(C6D6, 20 °C)
both SiMe3
NCtBu
4,5-Cp′′
o-C4H4B
m-C4H4B
2-Cp′′
o-C4H4B
m-C4H4B
4,5-Cp′′
NCtBu
m-C4H4B
o-C4H4B
m-C4H4B
4,5-Cp′′H
2-Cp′′H
6.18 (m, 1 H)
6.29 (m, 1 H)
6.31 (m, 2 H)
6.38 (m, 1 H)
6.51 (m, 1 H)
o-C4H4B
Cp′′Zr(C6F5)(NCtBu)
{η5-(3-MeC4H3BC6F5)}, 3Me
(CD2Cl2, 20 °C)
0.26, 0.41 (s, 9 H each)
1.74 (s, 9 H)
2.38 (s, 3 H)
5.45, 5.88 (m, 1 H each)
6.33 (m, 1 H)
6.49 (m, 1 H)
SiMe3
NCtBu
C4H3MeB
o-C4H3MeB
m-C4H3MeB
2-Cp′′H
-0.49, -0.08
20.00
27.40
110.19
120.28, 121.18
131.98
both SiMe3
NCtBu
C4H3MeB
m-C4H3MeB
4,5-Cp′′
(major isomer)
2-Cp′′
6.83, 6.87 (m, 1 H)
0.16, 0.47 (s, 9 H each)
1.59 (s, 9 H)
4,5-Cp′′H
SiMe3
NCtBu
(minor isomer)
-0.68, 0.13
19.33
both SiMe3
NCtBu
2.38 (s, 3 H)
5.40, 6.00 (m, 1 H each)
6.31 (s, 1 H)
C4H3MeB
o-C4H3MeB
m-C4H3MeB
2-Cp′′H
27.08
112.90
120.75
120.67, 130.26
C4H3MeB
2-Cp′′
m-C4H3MeB
4,5-Cp′′
6.51 (m, 1 H)
6.54, 6.96 (m, 1 H each)
0.18 (s, 18 H)
0.79 (s, 18 H)
5.20 (m, 2 H)
6.03 (m, 2 H)
4,5-Cp′′H
SiMe3
NCtBu
o-C4H4B
m-C4H4B
4,5-Cp′′H
2-Cp′′H
Cp′′Zr(C6F5)(CNtBu)2
{η5-C4H4BC6F5}, 4H
(toluene-d8, -20 °C)
0.74
28.31
100.21 (br)
108.45
114.97
SiMe3
NCtBu
o-C4H4B
m-C4H4B
4,5-Cp′′
6.06 (m, 2 H)
6.23 (m, 1 H)
123.44
2-Cp′′
Cp′′Zr(C6F5)(CNtBu)2-
{η5-(3-MeC4H3BC6F5)}, 4Me
(toluene-d8, -10 °C)
0.13, 0.23 (s, 9 H each)
0.83, 0.84 (s, 9 H each)
2.24 (s, 3 H)
4.96, 5.24 (m, 1H each)
5.72 (m, 1 H)
SiMe3
NCtBu
0.81, 0.90
20.00
28.47, 28.54
98.4 (v br), 105.6 (v br)
112.56
both SiMe3
C4H3BMe
both NCtBu
both o-C4H3MeB
4,5-Cp′′
C4H3MeB
o-C4H3MeB
4,5-Cp′′H
m-C4H3MeB
2-Cp′′H
5.74 (m, 1 H)
5.98 (m, 1 H)
114.24
117.10
m-C4H3MeB
2-Cp′′
6.40 (m, 1 H)
0.16, 0.20 (s, 9 H each)
0.84 (s, 9 H)
0.96 (s, 9 H)
4.49 (m, 1 H)
4.74 (m, 1 H)
5.71, 5.81 (m, 1 H each)
5.90 (m, 1 H)
6.04 (m, 1 H)
6.29 (m, 1 H)
4,5-Cp′′H
SiMe3
CNtBu
C(C6F5)NtBu
m-C4H4B
o-C4H4B
4,5-Cp′′H
2-Cp′′H
124.89
0.68, 0.96
28.94
4,5-Cp′′
both SiMe3
CNtBu
C(C6F5)NtBu
o-C4H4B
o-C4H4B
Cp′′Zr{η2-(C6F5CNtBu)}(CNtBu)-
{η5-C4H4BC6F5}, 5H
(C6D6, 20 °C)
29.01
96.3 (v br)
104.4 (v br)
106.43
111.35
111.79, 118.10
124.90
m-C4H4B
m-C4H4B
both 4,5-Cp′′
2-Cp′′
o-C4H4B
m-C4H4B
160.18
CNtBu
223.78
1.10, 1.20
20.98
28.68
28.97
102.9 (v br)
104.7 (v br)
106.98
113.33, 119.59
127.39
C(C6F5)NtBu
both SiMe3
C4H3MeB
CNtBu
Cp′′Zr{η2-(C6F5CNtBu)}(CNtBu)-
{η5-(3-MeC4H3BC6F5}, 5Me
(major isomer, toluene-d8, 20 °C)
0.17, 0.25 (s, 9 H each)
0.98 (s, 9 H)
1.00 (s, 9 H)
2.29 (s, 3 H)
4.18, 4.63 (m, 1 H each)
5.66 (m, 1 H)
5.84 (m, 1 H)
5.95 (m, 1 H)
5.98 (m, 1 H)
SiMe3
CNtBu
(C6F5)CN(tBu)
C4H3MeB
o-C4H3MeB
4,5-Cp′′H
2-Cp′′H
C(C6F5)NtBu
o-C4H3MeB
o-C4H3MeB
m-C4H3MeB
both 4,5-Cp′′
2-Cp′′
m-C4H3MeB
4,5-Cp′′H
162.05
221.95
CNtBu
(C6F5)CN(tBu)

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4083
Ta ble 1 (Con tin u ed )
1H NMR
13C NMR
complex
δ
assgnt
δ
assgnt
Cp′Zr(C4H7)(C4H6), 6a
(C6D6, 20 °C)
-0.74 (dd, 1H, J ) 7.2, 10.9)
-0.45 (dd, 1H, J ) 7.2, 10.9)
0.22 (s, 9H)
0.94 (dd, 1H, J ) 3.2, 13.4)
1.29 (dd, 1H, J ) 3.5, 9.3)
1.38 (d, 3H, J ) 5.7)
1.79 (t, 1H, J ) 8.0)
1.98 (m, 1H)
dCH2 anti
dCH2 anti
SiMe3
CH2 of C4H7
CH2 of C4H7
CH3 of C4H7
)CH2 syn
CHMe
0.21
SiMe3
CH3 of C4H7
dCH2
18.51
46.30
49.88
50.19
74.16
111.65
112.14
dCH2
CH2 of C4H7
CHMe of C4H7
Cp′
dCH
2.14 (t, 1H, J ) 8.1)
5.41 (m, 1H)
)CH2 syn
dCH
112.23, 115.62, 116.59
126.59
Cp′
CH of C4H7
5.60 (m, 1H)
dCH
5.92, 5.99 (m, 1H each)
6.43 (m, 2H)
Cp′
Cp′
CpMeZr(C4H7)(C4H6), 6b
(C6D6, 20 °C)
-0.63 (dd, 1H, J ) 7.5, 11.2)
-0.36 (dd, 1H, J ) 7.7, 11.0)
0.94 (dd, 1H, J ) 3.2, 13.2)
1.37 (d, 3H, J ) 5.9)
1.41 (dd, 1H, J ) 3.4, 9.4)
1.73 (t, 1H, J ) 8.0)
1.99 (s, 3H)
2.00 (m obscured by other peaks,
1H)
2.13 (t, 1H, J ) 8.9)
5.44 (m, 1H)
dCH2 anti
dCH2 anti
CH2 of C4H7
CH3 of C4H7
CH2 of C4H7
dCH2 syn
Me of CpMe
15.71
18.72
46.51
49.76
50.61
74.90
Me of CpMe
CH3 of C4H7
dCH2
dCH2
CH2 of C4H7
CHMe
108.09, 108.30, 110.07,
110.70
112.76, 112.97
122.25
CpMe
CHMe
dCH2 syn
dCH
dCH
ipso CpMe
CH of C4H7
126.87
5.64 (m, 1H)
dCH
5.88 (m obscured by other peaks,
1H)
5.92 (m, 2H)
CH of C4H7
CpMe
6.11 (m, 2H)
CpMe
Cp′Zr(C6F5){η4-CH2CHCHCH-
B(C6F5)2}7a (toluene-d8, 20 °C)
-0.10 (s, 9H)
SiMe3
)CH2
)CH2
CHB
-1.19
SiMe3
dCH2
dCHB
Cp′
Cp′
Cp′
Cp′
dCH
dCH
0.19 (t, 1H, J ) 9.8)
2.45 (t, 1H, J ) 9.2)
2.89 (d, 1H, J ) 12.8)
5.91 (t obscured by Cp′ peak,
1H)
5.94 (m, 1H)
6.11 (m, 1H)
6.39 (q, 1H, J ) 9.6)
6.48 (m, 1H)
70.45
95.0 (v br)
114.86
118.43
119.52
121.58
126.89
134.54
dCH
Cp′H
Cp′H
dCH
Cp′H
6.64 (m, 1H)
Cp′H
CpMe Zr(C6F5){η4-CH2CHCHCH- 0.11 (t, 1H, J ) 10.9)
dCH2
Me of CpMe
dCH2
dCHB
H of CpMe
H of CpMe
dCH
1.59
71.46
Me of CpMe
dCH2
)CHB
CpMe
B(C6F5)2}, 7b (toluene-d8, 20 °C)
1.61 (s, 3H)
2.44 (t, 1H, J ) 9.4)
2.93 (d, 1H, J ) 12.8)
5.82 (m, 1H)
95.2 (v br)
112.70
113.93
114.17
114.53
126.50
135.08
CpMe
5.84 (m, 1H)
CpMe
5.91 (t obscured by CpMe, 1H)
5.95 (m, 1H)
CpMe
H of CpMe
H of CpMe
dCH
dCH2
dCH2
dCHB
dCH
H of Cp
dCH
SiMe3
SiMe3
dCH
dCH
6.28 (m, 1H)
6.39 (q, 1H, J ) 9.6)
-0.01 (t, 1H, J ) 10.8)
2.39 (t, 1H, J ) 9.7)
2.85 (d, 1H, J ) 12.8)
5.94 (t obscured by Cp)
6.00 (s, 5H)
6.31 (q, 1H, J ) 9.7)
-0.16 (s, 9H)
-0.10 (s, 9H)
1.48 (m, 1H)
1.86 (m, 1H)
2.90 (m, 1H)
3.33 (m, 1H)
4.83 (d obscured by borole and
Cp′ peaks, 1H)
4.88 (m, 1H)
4.93 (m, 1H)
5.33 (m, 2H)
CpZr(C6F5){η4-CH2CHCHCH-
B(C6F5)2}, 7c (C6D6, 20 °C)
71.00
dCH2
dCHB
Cp
dCH
dCH
95.8 (v br)
114.09
127.09
135.06
Zr2Cp′2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3},
8a (C6D6, 20 °C)
-1.46, -1.02
14.48
both SiMe3
BCH2CHCHCHB
BCH2CHCHCHB
BCH2CHCHCHB
BCH2CHCHCHB
m-C4H4B
BCH2CHCHCHB 77.65
BCH2CHCHCHB 107.88
BCH2CHCHCHB 131.69
m-C4H4B
98.64, 126.19
114.80, 118.20
BCH2CHCHCHB 113.55, 113.67,
o-C4H4B
o-C4H4B
Cp′H
Cp′H
116.60, 117.70,
118.67, 120.88,
126.42
all Cp′
5.60 (m, 1H)
Cp′H
5.72 (m, 1H)
6.09 (m, 1H)
BCH2CHCHCHB
Cp′H
6.40 (m, 1H)
Cp′H
6.52 (m, 1H)
Cp′H
6.88 (m, 1H)
Cp′H
7.12 (m, 1H)
7.36 (m, 1H)
o-C4H4B
m-C4H4B

4084 Organometallics, Vol. 20, No. 19, 2001
Woodman et al.
Ta ble 1 (Con tin u ed )
1H NMR
13C NMR
complex
δ
assgnt
δ
assgnt
Zr2CpMe2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3}, 8b
(C6D6/1,2-difluorobenzene, 25 °C)
1.49 (dd, 1 H, J ) 5.19, 12.58)
1.68, 1.76 (s, 3 H each)
1.91 (dd, 1 H, J ) 10.45, 12.64)
2.97 (m, 1 H)
3.90 (s, 1 H)
4.89 (d, 1 H, J ) 18.64)
5.05 (s, 1 H)
5.18 (tr, 2 H, J ) 2.95)
5.44 (q, 1 H, J ) 2.57)
5.64 (q, 1 H, J ) 2.33)
5.68 (dd, 1 H, J ) 8.22, 18.63)
6.00 (q, 1 H, J ) 2.39)
6.09 (q, 1 H, J ) 2.24)
6.30 (q, 1 H, J ) 2.33)
6.45 (q, 1 H, J ) 2.39)
7.58 (m, 1 H)
BCH2CHCHCHB
Me of CpMe
BCH2CHCHCHB
BCH2CHCHCHB
C4H4B
13.97, 15.03
14.40
79.52
101.07, 109.04
109.59, 111.17,
111.63, 112.55,
113.54, 114.85,
114.98, 117.89
132.78
both Me of CpMe
BCH2CHCHCHB
BCH2CHCHCHB
both C4H4B
BCH2CHCHCHB
C4H4B
H of CpMe
all CpMe
BCH2CHCHCHB
H of CpMe
H of CpMe
(other peak obscured by solvent)
BCH2CHCHCHB
H of CpMe
H of CpMe
H of CpMe
H of CpMe
C4H4B
(1 C4H4B obscured by 1,2-
difluorobenzene)
1.47 (dd, 1 H, J ) 5.43, 12.47)
1.85 (dd, 1 H, J ) 10.71, 12.76)
3.11 (m, 1 H)
Zr2Cp2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3} 8c
(C6D6/1,2-difluorobenzene, 25 °C)
BCH2CHCHCHB
BCH2CHCHCHB
BCH2CHCHCHB
C4H4B
BCH2CHCHCHB
C4H4B
14.41 (br)
78.03
99.84 (br)
109.16 (br)
110.56
BCH2CHCHCHB
BCH2CHCHCHB
C4H4B
C4H4B
Cp
3.78 (s, 1 H)
4.83 (d, 1 H, J ) 18.93)
5.08 (s, 1 H)
115.61
Cp
5.48 (s, 5 H)
5.69 (dd, 1 H, J ) 8.51, 18.93)
6.26 (s, 5 H)
Cp
124.62
128.12
132.51
BCH2CHCHCHB
C4H4B
BCH2CHCHCHB
BCH2CHCHCHB
Cp
7.51 (m, 1 H)
C4H4B
(1 C4H4B obscured by
1,2-difluorobenzene)
-0.38, -0.01, -0.08, 0.20 (s, 9H each)
1.51 (d, 2 H, J ) 8.04)
3.36 (q, 1 H, J ) 8.27)
3.91 (m, 1 H)
4.81 (d, 1 H, J ) 19.44)
4.98 (m, 1 H)
5.51 (m, 1 H)
Zr2Cp′′2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3} 8d
(C6D6, 20 °C)
SiMe3
-1.20, -0.84,
-0.69, -0.21
14.95
81.40
98.71
BCH2CHCHCHB
BCH2CHCHCHB
m-C4H4B
BCH2CHCHCHB
o-C4H4B
all SiMe3
BCH2CHCHCHB
BCH2CHCHCHB
m-C4H4B
both o-C4H4B
4,5-Cp′′H
105.72, 111.34
119.73
4,5-Cp′′H
5.81 (d, 1 H, J ) 6.46)
BCH2CHCHCHB
2-Cp′′H
4,5-Cp′′H
121.54
123.87
124.01, 124.78
126.64
BCH2CHCHCHB
BCH2CHCHCHB
4,5-Cp′′H
5.89 (m, 1 H)
6.03, 6.66 (m, 1 H each)
6.74 (m, 1 H)
2-Cp′′H
m-C4H4B
6.81 (m, 1 H)
7.08 (m, 1 H)
o-C4H4B
4,5-Cp′′H
127.69, 129.50
129.95
both 2-Cp′′H
4,5-Cp′′H
7.87 (m, 1 H)
o-C4H4B
a
All shifts are in ppm and J values are in Hz. 13C NMR signals for the C6F5 groups are not reported.
complexes and thus may exhibit different bonding
arrangements.6
Complexes 4H and 4Me are not thermally stable.
After 1 h at room temperature the signals associated
with these complexes are quantitatively replaced by a
new set of signals, corresponding to Cp′′Zr{C(NtBu)-
C6F5}(CNtBu){η5-(3-RC4H3BC6F5)} (5H, 5Me), as the
products of the migratory insertion of one molecule of
isocyanide into the zirconium-C6F5 bond. The com-
pounds are isolated as bright yellow crystals. The
iminoacyl ligand is η2-bonded, as confirmed by a crystal-
lographic study of 5H (see below). Such migratory
insertion reactions are common for organometallic
zirconium complexes;7 however we believe that this
represents the first crystallographically characterized
example involving an insertion into the rather stable
Zr-C6F5 bond. As with 1Me and 3Me, compound 5Me
exists as a pair of diastereomers, although in this case
the ratio is closer to 1:0.15. Because of the small amount
of the second isomer, only the major isomer was fully
characterized. There is no evidence for further inser-
tions, even in the presence of excess isocyanide and over
extended periods of time. As would be expected, the C6F5
group of the iminoacyl ligand shows no sign of hindered
Treatment of solutions of 1H and 1Me in toluene-d8
at -20 °C with 4 equiv of tert-butyl isocyanide leads to
a rapid color change from red to yellow. The products
in both cases are the bis-isocyanide adducts Cp′′Zr-
(C6F5)(CNtBu)2{η5-(3-RC4H3BC6F5)} (4H, 4Me). The
complexation of two isocyanide ligands is revealed by
the 1H NMR spectrum. For 4H a sharp singlet is
observed at δ 0.79 representing 18 protons, while for
4Me there are two singlets at δ 0.83 and 0.84 (ratio 1:1),
since the two isocyanide ligands are rendered inequiva-
lent by the presence of the borole-methyl substituent.
The o-F signals of the zirconium-C6F5 group in the 19F
NMR spectra are at very low field (δ -98.7 and -99.3
for 4H and δ -97.7 and -99.5 for 4Me) and clearly show
hindered rotation.
(8) Giannini, L.; Caselli, A.; Solari, E.; Floriani, C.; Chiesi-Villa, A.;
Rizzoli, C.; Re, N.; Sgamellotti, A. J . Am. Chem. Soc. 1997, 119, 9198.
(9) Brackemeyer, T.; Erker, G.; Fro¨hlich, R. Organometallics 1997,
16, 531.
(10) Schubart, M.; Mitchell, G.; Gade, L. H.; Kottke, T.; Scowen, I.
J .; McPartlin, M. Chem Commun. 1999, 233.

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4085
Ta ble 2. 19F NMR Da ta for Bor yld ien e a n d Bor ole Com p ou n d s
complex
δ
assgnt
Cp′′Zr(C6F5)(NCMe){η5-C4H4BC6F5}, 2H
-113.3 (br s, 1 F), -121.1 (br s, 1 F), -131.5 (m, 2 F)
-157.2 (t, 1 F, J FF ) 19.8), -159.5 (t, 1 F, J FF ) 19.8)
-162.9 (br d, 2 F), -165.2 (m, 2 F)
-115.5 (br s, 1 F), -120.19 (br s, 1 F), -131.2 (d, 2 F, J FF ) 19.8)
-157.3 (t, 1 F, J FF ) 19.8), -159.8 (t, 1 F, J FF ) 19.8)
-163.4 (br s, 1 F), -163.8 (br s, 1 F) overlapping, -165.4 (m, 2 F)
-113.0 (d, 1 F, J FF ) 33.9), -119.1 (d, 1 F, J FF ) 31.1), -131.4 (m, 2F)
-157.06 (t, 1 F, J FF ) 19.8), -159.6 (t, 1 F, J FF ) 19.8)
-162.63 (br m, 2 F), -165.1 (m, 2 F)
o-F
(C6D6, 25 °C)
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
p-F
m-F
o-F
Cp′′Zr(C6F5)(NCtBu){η5-C4H4BC6F5}, 3H
(C6D6, 25 °C)
Cp′′Zr(C6F5)(NCtBu) {η5-(3-MeC4H3BC6F5)},
3Me (C6D6, 25 °C, major isomer)
(minor isomer)
-110.7 (s, 1 F), -120.0 (s, 1 F), -131.5 (m, 2 F)
-157.4 (t, 1 F, J FF ) 19.8), -159.9 (t, 1 F, J FF ) 19.8)
-163.2 (br m, 2 F), -165.8 (m, 2 F)
Cp′′Zr(C6F5)(CNtBu)2{η5-C4H4BC6F5}, 4H
(toluene-d8, -20 °C)
-98.7 (d, 1 F, J FF ) 31.1), -99.3 (d, 1 F, J FF ) 33.9), -128.7 (m, 2 F)
-160.1 (t, 1 F, J FF ) 19.8), -160.8 (t, 1 F, J FF ) 19.8)
-162.8 (m, 1 F), -164.2 (m, 1 F), -165.5 (m, 2 F)
-97.7 (br s, 1 F), -99.5 (br s, 1 F), -128.7 (d, 2 F, J FF ) 19.8)
-160.2 (t, 1 F, J FF ) 19.8), -161.23 (t, 1 F, J FF ) 19.8)
-162.9 (m, 1 F), -164.5 (m, 1 F), -165.57 (m, 2 F)
-128.4 (d, 2 F, J FF ) 19.8), -138.86 (br s, 2 F)
-157.3 (t, 1 F, J FF ) 24.0), -161.1 (t, 1 F, J FF ) 24.0)
-161.4 (v br, 2 F), -165.7 (m, 2 F)
-128.6 (m, 2 F), -138.4 (m, 2 F)
-157.8 (t, 1 F, J FF ) 19.8), -162.6 (t, 1 F, J FF ) 19.8)
-162.0 (v br, 2 F), -165.9 (m, 2 F)
-116.5 (m, 2 F), -130.4 (m, 2 F), -159.3 (s, 2 F)
-150.8 (t, 1 F, J FF ) 19.8), -152.1 (t, 1 F, J FF ) 19.8),
-154.3 (t, 1 F, J FF ) 19.8)
Cp′′Zr(C6F5)(CNtBu)2{η5-(3-MeC4H3BC6F5)},
4Me (toluene-d8, -20 °C)
Cp′′Zr{η2-(C6F5CNtBu)}(CNtBu){η5-C4H4BC6F5},
5Me (toluene-d8, -20 °C)
Cp′′Zr{η2-(C6F5CNtBu)}(CNtBu)
{η5-(3-MeC4H3BC6F5)}, 5Me
(major isomer, toluene-d8, 25 °C)
Cp′Zr(C6F5){η4-CH2CHCHCHB(C6F5)2}, 7a
(toluene-d8, 25 °C)
p-F
-160.6 (m, 2 F), -161.7 (m, 4 F)
-109.2 (br s, 1 F), -121.1 (br s, 1 F), -130.3 (s, 2 F),
-131.1 (s, 1 F), -172.4 (s, 1 F)
m-F
o-F
(toluene-d8, -60 °C)
-149.3 (m, 1 F), -150.7 (m, 1 F), -153.9 (m, 1 F)
-156.5 (m, 1 F), -161.6 (br m, 5 F)
p-F
m-F
o-F
CpMeZr(C6F5){η4-CH2CHCHCHB(C6F5)2}, 7b
(toluene-d8, 25 °C)
-118.0 (m, 2 F), -130.5 (m, 2 F), -159.6 (s, 2 F)
-151.1 (t, 1 F, J FF ) 19.8), -152.6 (t, 1 F, J FF ) 19.8),
-154.4 (t, 1 F, J FF ) 19.8)
p-F
-162.0 (m, 6 F)
m-F
o-F
(toluene-d8, -60 °C)
-115.7 (vbr s, 2 F), -130.8 (s, 2 F), -131.2 (d, 1 F, J FF ) 19.8),
-172.4 (d, 1 F, J FF ) 19.8)
-149.1 (t, 1 F, J FF ) 19.8), -150.9 (t, 1 F, J FF ) 19.8),
-153.8 (t, 1 F, J FF ) 19.8)
p-F
m-F
o-F
p-F
-159.4 (m, 1 F), -160.0 (m, 1 F), -161.0 (m, 4 F)
-117.1 (m, 2 F), -130.8 (m, 2 F), -159.3 (s, 2 F)
-150.8 (t, 1 F, J FF ) 19.8), -151.8 (t, 1 F, J FF ) 19.8),
-154.1 (t, 1 F, J FF ) 19.8)
CpZr(C6F5){η4-CH2CHCHCHB(C6F5)2}, 7c
(toluene-d8, 25 °C)
-161.6 (m, 2 F), -162.1 (m, 4 F)
m-F
o-F
(toluene-d8, -60 °C)
-115.6 (br s, 2 F), -130.9 (d, 2 F, J FF ) 16.9),
-131.4 (d, 1 F, J FF ) 16.9), -173.3 (d, 1 F, J FF ) 28.2)
-149.6 (t, 1 F, J FF ) 22.6), -151.1 (t, 1 F, J FF ) 22.6),
-153.6 (t, 1 F, J FF ) 19.8)
p-F
m-F
o-F
-156.5 (t, 1 F, J FF ) 22.6), -160.4 (br t, 1 F), -160.9 (m, 2 F)
-161.7 (m, 2 F)
-113.2 (br s, 1 F), -115.2 (vbr s, 1 F), -119.8 (br s, 1 F),
-120.7 (vbr s, 1 F), -126.5 (s, 1 F), -130.1 (br s, 2 F), -132.6 (br s, 2 F),
-222.9 (d, 1 F, J FF ) 33.9)
-151.8 (t, 1 F, J FF ) 19.8), -152.9 (t, 1 F, J FF ) 19.8),
-156.2 (t, 1 F, J FF ) 19.8), -157.9 (t, 1 F, J FF ) 19.8),
-158.4 (t, 1 F, J FF ) 19.8)
-161.5 (br m, 6 F), -164.2 (br s, 3 F), -164.5 (br m, 1 F)
-127.6 (br s, 2 F), -130.6 (vbr s, 3 F), -133.8 (br s, 4 F),
-218.3 (br s, 1 F)
Zr2Cp′2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3}, 8a
(C6D6, 20 °C)
p-F
m-F
o-F
Zr2CpMe2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3}, 8b
(C6D6/1,2-difluorobenzene, 25 °C)
-153.9 (m, 2 F), -158.2 (m, 1 F), 159.8 (m, 1 F)
-160.0 (m, 1 F)
p-F
m-F
o-F
-161.6 (br m, 5 F), -167.5 (br m, 5 F)
Zr2Cp2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3}, 8c
(C6D6/1,2-difluorobenzene, 25 °C)
-120.2 (vbr s, 4 F), -127.46 (br s, 1 F), -130.6 (br s, 2 F),
-133.8 (br s, 2 F)
-153.8 (m, 2 F), -157.8 (br s, 1 F), -159.5 (br s, 1 F),
-159.8 (br s, 1 F)
p-F
m-F
o-F
-161.4 (br s, 1 F), -161.8 (m, 4 F), -164.7 (br m, 5 F)
-108.2 (br s, 1 F), -112.8 (vbr s, 1 F), -119.9 (vbr s, 1 F),
-120.2 (br s, 1 F), -126.2 (s, 1 F), -130.0 (vbr s, 2 F),
-132.9 (br s, 2 F), -217.2 (m, 1 F)
-152.1 (t, 1 F, J FF ) 19.8), -152.5 (t, 1 F, J FF ) 19.8),
-157.1 (t, 1 F, J FF ) 19.8), -157.6 (t, 1 F, J FF ) 19.8),
-159.0 (t, 1 F, J FF ) 19.8)
Zr2Cp′′2(C6F5)2{µ-η5:η5-C4H4B-
CH2-η3,κF-CHCHCHB(C6F5)3}, 8d
(C6D6, 25 °C)
p-F
-160.2 (t, 1 F, J FF ) 19.8), -160.5 (m, 3 F), -161.5 (br s, 1 F)
-162.6 (m, 1 F), -164.2 (m, 2 F), -164.4 (m, 2 F)
m-F

4086 Organometallics, Vol. 20, No. 19, 2001
Woodman et al.
lengths of 2.362 (4) and 2.364(4) Å are longer than the
corresponding bond distance in [Cp3Zr(CtNCMe3)]-
[MeB(C6F5)3]9 of 2.313(3) Å, but shorter than those
observed in [MeSi{SiMe2N(p-tol)}3Zr(CNCMe3)3][Co-
(CO)4] at 2.431(7), 2.448(7), and 2.440(7) Å.10 As ex-
pected, the Zr-CtN- unit is linear (173.63(16)° and
175.8(4)°). The CtN bond lengths are 1.150(5) and
1.140(5) Å, showing essentially no difference from the
CtN distance in the free isonitrile.11 Bonding to the
borole-carbon atoms is tighter than to Cp′′, with an
average Zr-C(borole) distance of 2.480 Å as compared
with 2.547 Å for Zr-Cp′′, while the Zr-B(1) distance is
significantly longer, 2.664(5) Å (molecule 1).
Tr ip le-Deck er Com p lexes. The reactions of the
diene complexes CpRZr(η3-crotyl)(η4-butadiene) (6a , CpR
) C5H4SiMe3; 6b, C5H4Me; 6c, Cp; 6d , Cp′′) with
B(C6F5)3 in toluene were studied by NMR spectroscopy.
Addition at room temperature generates the boryldiene
complexes CpRZr(C6F5){η4-κF-CH2CHCHCHB(C6F5)2}
(7a -d ) in quantitative yield (Scheme 2). Presumably
the reaction pathway involves a zwitterionic bis(allyl)
intermediate, as described for the complexes CpRZr(η3-
allyl)(η4-isoprene) (CpR ) Cp, CpMe, Cp′, Cp′′, and
Ind).12,13 The reaction proceeds with C-H activation and
the elimination of butene, with the simultaneous trans-
fer of a C6F5 group from boron to the metal center. We
have previously reported that the Cp′′ complex Cp′′Zr-
(C6F5){η4-κF-CH2CHCHCHB(C6F5)2} (7d ) exists in solu-
tion as a mixture of three isomers, two of which feature
the diene ligand in prone (endo) and supine (exo)
orientation with regard to the cyclopentadienyl ring,
while in the third the diene is roughly perpendicular to
the ring.13 No such isomerism is detected in 7a -c.
However, these complexes do show fluxionality of the
C6F5 ligands, as shown by variable-temperature 19F
NMR spectroscopy. At -60 °C in toluene-d8, the o-F
atoms of the Zr-C6F5 ring of 7a are observed at relatively
high frequencies, δ -109.2 and -120.8, thus indicating
hindered rotation, presumably due to a steric interaction
with the cyclopentadienyl ring. The o-F atoms of one of
the boryl-C6F5 rings are also inequivalent, with reso-
nances at δ -131.0 and -172.3. The high-field shift of
the latter is consistent with coordination to zirconium.12
By contrast, the second boryl-C6F5 ring rotates freely
at this temperature, as shown by single o-F resonance
at δ -130.3. Warming the solution from -60 °C to 20
°C results in the broadening, coalescence, and sharpen-
ing of the o-F signals. The signals for the Zr-C6F5 ligand
coalesce at -20 °C and eventually form one sharp peak
at δ -115.6. The process is slower for the coordinated
B-C6F5 substituent, where coalescence occurs at 0 °C.
Further warming to 20 °C gives a sharp peak at δ
-159.3. This fluxionality could not be studied at higher
temperatures due the thermal instability of the complex.
7b and 7c exhibit very similar 19F NMR spectra across
the range of temperatures investigated.
F igu r e 1. Molecular structure of Cp′′Zr(C6F5)(CNtBu){η5-
C4H4BC6F5}, 3H, showing the atomic numbering scheme.
Ellipsoids are drawn at 40% probability.
Ta ble 3. Selected Dista n ces (Å) a n d An gles (d eg)
for 3H
Zr-C(11)
Zr-C(13)
Zr-C(15)
Zr-B(31)
Zr-C(33)
Zr-C(35)
N(4)-C(41)
2.523(3)
2.550(3)
2.500(3)
2.626(3)
2.433(3)
2.485(3)
1.140(4)
Zr-C(12)
Zr-C(14)
Zr-C(21)
Zr-C(32)
Zr-C(34)
Zr-N(4)
2.521(3)
2.521(3)
2.350(3)
2.501(3)
2.405(3)
2.301(2)
1.481(4)
C(41)-C(42)
C(41)-Zr-N(4)
N(4)-Zr-C(21)
177.7(2) N(4)-C(41)-C(42)
179.5(3)
109.73(9) C(32)-B(31)-C(311) 129.6(3)
C(35)-B(31)-C(311) 127.4(3) C(35)-B(31)-C(32) 103.0(2)
rotation at room temperature, with a single o-F signal
in the 19F NMR spectrum at ca. δ -138. The 13C NMR
resonances of the iminoacyl carbon atoms are found at
δ 223.78 and 221.95 for 5H and 5Me, repectively.7
Crystals of 3H suitable for single-crystal X-ray dif-
fraction were obtained from benzene-d6 at room tem-
perature. The molecular structure of 3H is depicted in
Figure 1. Important bond lengths and angles are col-
lected in Table 3. The structural details are closely
similar to those found in 1H; for example the Zr-C
distances to the C4H4BC6F5 ligand (average 2.456 Å) are
almost identical to those in 1H (average 2.455 Å).4 As
in the structure of 1H,4 the B-C(aryl) bond distance
(1.590(4) Å) in the C4H4BC6F5 ligand of 3H is typical of
a single bond and indicates little π-bonding contribution.
Single crystals of 5H suitable for X-ray diffraction
were obtained from light petroleum at -20 °C. The
asymmetric unit comprises two independent molecules,
one of which is depicted in Figure 2. The two independ-
ent molecules differ principally in the relative orienta-
tion of the tert-butyl group of the coordinated isonitrile
ligands. Important bond lengths and angles are collected
in Table 4. The structure confirms the η2-bonding of the
iminoacyl ligand, with an “N-inside” orientation and
Zr-N distances for the two molecules of 2.279(4) and
2.266(4) Å and Zr-C distances of 2.252(4) and 2.264(4)
Å. These are slightly longer than the corresponding
parameters in, for example, the η2-iminoacyl complex
{p-tBu-calix[4](OMe)O3}Zr(tBuNdCPh) [Zr-N ) 2.180(3)
Å; Zr-C ) 2.260(3) Å].8 The Zr-C(isocyanide) bond
Over the course of 48 h the signals associated with
the boryl-diene complexes 7 are gradually replaced by
those of a new type of product, identified as the triple-
(11) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
G. A.; Taylor, R. J . Chem. Soc., Perkin Trans. 1987, S1.
(12) Corradi, M. M.; J ime´nez Pindado, G. J .; Sarsfield, M. J .;
Thornton-Pett, M.; Bochmann, M. Organometallics 2000, 19, 1150.
(13) J ime´nez Pindado, G.; Thornton-Pett, M.; Bochmann, M. J .
Chem. Soc., Dalton Trans. 1997, 3115.

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4087
F igu r e 2. Structure of one of the two independent molecules in the unit cell of Cp′′Zr(η2-C6F5CNtBu)(η5-C4H4BC6F5), 5H,
showing the atomic numbering scheme. Ellipsoids are drawn at 40% probability.
Ta ble 4. Selected Dista n ces (Å) a n d An gles (d eg)
for 5H
removed completely, the complexes become much less
soluble, and 1,2-difluorobenzene had to be used to obtain
sufficiently concentrated solutions for NMR spectros-
copy on 8b and 8c.
molecule 1
molecule 2
Zr(1)-N(17)
2.279(4)
2.664(5)
2.252(4)
1.260(6)
2.527(4)
2.449(4)
2.430(5)
2.513(4)
2.555(5)
2.543(4)
2.562(4)
2.528(4)
2.548(4)
2.362(4)
1.150(5)
Zr(2)-N(43)
2.266(4)
2.687(5)
2.264(4)
1.264(6)
2.517(4)
2.429(5)
2.451(4)
2.547(4)
2.573(4)
2.539(4)
2.545(4)
2.540(4)
2.536(4)
2.364(4)
1.140(6)
The spectra of all four complexes are highly distinc-
tive. The 11B NMR spectra of 8a -d show sharp signals
at δ -12 to -13 for the butenyl-B(C6F5)3 borate and a
broad signal around δ 0-3 corresponding to the borole
ligand. The 19F NMR spectra for all three complexes
show a signal in the region δ -215 to -225, which is
indicative of the coordination of one of the ortho-F atoms
of the butenyl-B(C6F5)3 moiety to the metal center.
Erker and co-workers previously found a similar 19F
NMR chemical shift in the related complex Cp2Zr{η3-
CH2CHCHCH2B(C6F5)3} (δ -213.2).14 However, in that
case exchange of o-F atoms was slow only at -80 °C,
with a coalescence temperature well below 0 °C, indica-
tive of a rather weak Zr‚‚‚F interaction (∆Gq ) 8.1 kcal
mol-1), whereas 8a -d show well-resolved o-F signals
even at room temperature. Variable-temperature 19F
NMR spectroscopy on 8d shows that the signals for the
o-F broaden and eventually coalesce at 68 °C (∆Gq )
13.2 kcal mol-1),15 although the spectrum is further
complicated by the coalescence of the o-F signals for the
other two C6F5 groups of the B(C6F5)3 unit. Above this
temperature all three C6F5 groups are exchanging fast
enough to be indistinguishable on the NMR time scale.
Structural characterization of 8d 5 revealed an un-
usually short Zr-F distance of 2.355(3) Å when com-
pared to related species with Zr‚‚‚F coordination, for
example, [NEt4]2[{C5H4B(C6F5)3}Zr(µ-Cl)Cl2]2 [2.430(2)
Å],16 (C5Me5)Zr(C6F5){η4-C4H5B(C6F5)2} [2.4292(15) Å],17
and Cp2Zr{η3-C4H6B(C6F5)3}[2.423(3) Å].14 Since the
Zr(1)-B(1)
Zr(1)-C(18)
N(17)-C(18)
Zr(1)-C(2)
Zr(1)-C(3)
Zr(1)-C(4)
Zr(1)-C(5)
Zr(1)-C(12)
Zr(1)-C(13)
Zr(1)-C(14)
Zr(1)-C(15)
Zr(1)-C(16)
Zr(1)-C(25)
C(25)-N(26)
Zr(2)-B(27)
Zr(2)-C(44)
N(43)-C(44)
Zr(2)-C(28)
Zr(2)-C(29)
Zr(2)-C(30)
Zr(2)-C(31)
Zr(2)-C(38)
Zr(2)-C(39)
Zr(2)-C(40)
Zr(2)-C(41)
Zr(2)-C(42)
Zr(2)-C(51)
C(51)-N(52)
Zr(1)-N(17)-C(18) 72.7(3)
Zr(1)-C(18)-N(17) 75.0(3)
Zr(1)-N(17)-C(17) 154.5(3)
Zr(1)-C(18)-C(19) 154.2(3)
Zr(2)-N(43)-C(44) 73.7(3)
Zr(2)-C(44)-N(43) 73.9(3)
Zr(2)-N(43)-C(43) 154.0(3)
Zr(2)-C(44)-C(45) 155.8(3)
N(17)-Zr(1)-C(18) 32.23(14) N(43)-Zr(2)-C(44) 32.41(14)
N(17)-Zr(1)-C(25) 81.36(14) N(43)-Zr(2)-C(51) 82.24(16)
C(18)-Zr(1)-C(25) 113.63(16) C(44)-Zr(2)-C(51) 114.63(17)
Zr(1)-C(25)-N(26) 173.8(3)
C(25)-N(26)-C(26) 177.5(4)
Zr(2)-C(51)-N(52) 175.8(4)
C(51)-N(52)-C(52) 178.2(7)
decker complexes Zr2(CpR)2(C6F5)2{µ-η5:η5-C4H4BCH2-
η3,κF-CHCHCHB(C6F5)3} (8a -d ) (Scheme 3). The
conversion is essentially quantitative, with no evi-
dence for any other products, such as the mononuclear
borole complex 1H produced from Cp′′Zr(C6F5){η4-
CH2CHCHCHB(C6F5)2}.4 Compounds 8a -d were pre-
pared in one-pot reactions from the diene complexes
6a -d and B(C6F5)3 in toluene as red to orange solids in
good yields.
Compounds 8a and 8d show high solubility in most
hydrocarbon solvents and ether, while 8b and 8c are
less soluble. 8b was obtained pure by recrystallization
of the crude reaction product from benzene. A pure
sample of 8c was obtained by stirring an ether solution
for 1 h, during which time 8c precipitated as an orange
solid. It seems that the complexes retain toluene to some
degree after solvent removal. Once this toluene is
(14) (a) Temme, B.; Erker, G.; Karl, J .; Luftmann, H.; Fro¨hlich, R.;
Kotila, S. Angew. Chem. 1995, 107, 1867; Angew. Chem., Int. Ed. Engl.
1995, 34, 1755. (b) Karl, J .; Erker, G.; Fro¨hlich, R. J . Am. Chem. Soc.
1997, 119, 11165.
(15) ∆Gq was calculated as follows. ∆Gq ) 4.57 Tc(10.32 + log Tc
-
log kc) cal mol-1 where Tc ) coalescence temperature, kc ) π∆υ/x2,
∆υ ) peak separation in 19F NMR at Tc.
(16) Lancaster, S. J .; Thornton-Pett, M.; Dawson, D. M.; Bochmann,
M. Organometallics 1998, 17, 3829.

4088 Organometallics, Vol. 20, No. 19, 2001
Woodman et al.
Sch em e 2
Sch em e 3
NMR spectra for 8a -c are closely similar to those of
8d , similarly short interactions are probably present in
these complexes, but as yet no structural characteriza-
tion has been possible. Addition of a few drops of
pivalonitrile to a solution of 8d in toluene-d8 results in
the disappearance of the o-F resonance at δ -217, and
a broad doublet around δ -128 corresponding to the six
o-F atoms of the -B(C6F5)3 moiety suggests that all
three pentafluorophenyl groups are now equivalent.
The 1H NMR spectra of the ansa-butenylborole ligand
are closely similar in all four complexes. The four
protons of the C4H4B ring are found over a large
chemical shift range, from around δ 3 to nearly δ 8. The
butenyl protons exhibit a highly characteristic coupling
pattern.
The transformation of 6 into 8 is remarkable. Several
other triple-decker complexes featuring a central borole
ligand are known;18-21 however, compounds 8 are the
first examples for a group 4 metal. Whereas the forma-
tion of the mononuclear borole complex Cp′′Zr(C6F5)-
(OEt2){η5-(3-RC4H3BC6F5)} was specific to Cp′′, the
triple-decker complexes form readily for a variety of Cp
ligands. Apparently the sterically highly hindered Cp′′
ligand is needed for the formation of 1, while the triple-
decker compounds 8 are formed in high yield even with
unsubstituted cyclopentadienyl derivatives. There was
no evidence for the formation of mononuclear borole
complexes where CpR ) C5H4SiMe3 or C5H4Me.
The formation of 8 necessarily involves two molecules
of 7, which react with redistribution of the C6F5 sub-
stituents of the -B(C6F5)2 units in 7 to give a borole
and a borate. Scheme 4 depicts a plausible sequence
including an intermediate showing the required re-
arrangements involved in the formation of 8. One C6F5
substituent is lost as pentafluorobenzene following
activation of one terminal C-H bond of a boryldiene
ligand in the intermediate 7. During the course of this
sequence attack of a dienyl ligand on the B-C6F5 moiety
of a postulated borole intermediate can be envisaged,
with the result that one of the original B(C6F5)3 mol-
ecules loses all of its C6F5 substituents to form an alkyl-
substituted borole ring. Equally unexpected is the
transfer of the Zr-C6F5 ligand on the second zirconium
atom, either to the other Zr center or to the boryl-boron.
Evidently the zwitterionic structure 8 is favored over
its neutral isomer 8′, possibly because of efficient
stabilization of the former by the Zr‚‚‚o-F coordination.
Eth en e P olym er iza tion . In a previous communica-
tion4 we reported that solutions of the boryldiene
complex Cp′′Zr(C6F5){CH2C(Me)CHCHB(C6F5)2} in the
presence or absence of AlMe3 showed no catalytic
activity toward the polymerization of ethene. However,
after an induction period of ca. 10 min at 60 °C under
6 bar ethene pressure and in the presence of AlMe3 the
onset of polymerization was noted, and it was found that
the activity increased slowly with time. This behavior,
indicative of the slow buildup of a catalytically active
species, was rationalized as the formation of a mono-
nuclear borole-containing species, i.e., 1Me. Solutions
of 1Me with either AlMe3 or MAO in ratios from 1:15
to 1:40 indeed showed good catalytic activity without
an induction period. However, the facile isolation of the
triple-decker complexes 8 from the boryldiene complexes
7 led us to question the true identity of the active species
in the previous chemistry.
(17) J ime´nez Pindado, G.; Thornton-Pett, M.; Bowkamp, M.; Meets-
ma, A.; Hessen, B.; Bochmann, M. Angew. Chem. 1997, 109, 2457;
Angew. Chem., Int. Ed. Engl. 1997, 36, 2358.
(18) Herberich, G. E.; Hessner, B.; Saive, R. J . Organomet. Chem.
1987, 319, 9.
(19) Herberich, G. E.; Hengesbach, J .; Huttner, G.; Frank, A.;
Schubert, U. Chem. Ber. 1983, 116, 141.
(20) Herberich, G. E.; Hessner, B.; Howard, J . A. K.; Ko¨ffer, D. P.
J .; Saive, R. Angew. Chem., Int. Ed. Engl. 1986, 25, 165.
(21) Herberich, G. E.; Hengesbach, J .; Ko¨lle, U.; Huttner, G.; Frank,
A. Angew. Chem., Int. Ed. Engl. 1976, 15, 433.
Mixtures of 8d with AlMe3 (Al:Zr ) 30:1) at 25 and
60 °C under 1 bar ethene failed to produce any poly-
merization. An NMR experiment showed that mixtures
of 8d and AlMe3 in toluene-d8 do not react, in contrast

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4089
Sch em e 4
Ta ble 5. Eth en e P olym er iza tion s w ith Tr ip le-Deck er Com p lexes (8a -d )a
catalyst
precursor
polymer
yield [g]
productivity [103 g PE
activator
T [°C]
t [min]
Zr [µmol]
Al/Zr ratio
(mol M)-1 h-1 bar-1
]
Mw
Mw/Mn
8d
8d
8d
8d
8a
8a
8b
8b
8b
8c
8c
AlMe3
AlMe3
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
25
60
60
60
60
60
60
60
60
60
60
15
20
20
20
5
5
5
5
5
8.8
8.8
32.3
9.7
25
5
20
20
5
30
30
0
0
77.4
774
100
500
100
500
500
500
500
0.156
0.093
0.236
0.241
0.308
0.408
0.221
0.425
0.041
14.5
28.9
113
577
185
245
531
120
49.2
195 000
244 000
101 000
578 000
260 000
198 000
381 000
216 000
278 000
14
9.4
8.0
7.4
5.3
3.8
3.5
4.4
4.8
10
10
20
5
a
40 mL of toluene, ethene 1 bar.
to mixtures of 1Me and AlMe3, where Zr-C6F5/Me
exchange takes place readily.4 However, when 8d was
activated with MAO in Al:Zr ratios of 77:1: and 770:1,
some polymer was produced, although the activities
were modest ((1-2) × 104 g PE (mol Zr)-1 h-1 bar-1).
Polymerization results are collected in Table 5. Solu-
tions of the sterically less hindered compounds 8a and
8b, when activated with MAO, gave significantly higher
activities (up to ca. 6 × 105 g PE (mol M)-1 h-1 bar-1),
while the activity of 8c is slightly less. The molecular
weight distributions are quite broad, particularly so for
8a and 8d . This may be due in part to a lack of
premixing of the catalyst and activator and thus failure
to achieve uniform activation. It is also noted that the
molecular weights tend to increase with decreasing
catalyst concentration, a feature suggestive of mass
transport limitation under the low-pressure conditions
employed.
while nitriles and isocyanides readily form adducts. The
latter react further with insertion into the Zr-C6F5 bond
to give η2-iminoacyl compounds. A variation of the
synthetic route leading to 1 provides surprisingly simple
access to borole-bridged triple-decker complexes 8,
either by thermal decomposition of boryldiene complexes
7 or directly by treatment of the diene complexes 6 with
B(C6F5)3. Whereas the formation of 1 was observed only
in the case of bulky cyclopentadienyl ligands such as
1,3-C5H3(SiMe3)2, the formation of 8 proved to be quite
general and independent of the steric requirements of
the Cp ligands. The complexes are zwitterionic and
stabilized by remarkably strong Zr‚‚‚F interactions (ca.
13.2 kcal mol-1). Although B(C6F5)3 is a widely used and
generally very stable catalyst activator,22 the formation
of 8 underlines the very facile C6F5 transfer from
B(C6F5)3 to zirconium that is possible under certain
conditions. The chemistry of half-sandwich complexes
such as the zirconium diene compounds employed in this
study is in stark contrast to the behavior of bis-
Con clu sion
The Zr-C6F5 ligand in borole pentafluorophenyl com-
plexes of type 1 is reactive toward alkylating agents,
(22) Reviews: Luo, L.; Marks, T. J . Top. Catal. 1999, 7, 97. Chen,
E. Y. X.; Marks, T. J . Chem. Rev. 2000, 100, 1391.

4090 Organometallics, Vol. 20, No. 19, 2001
Woodman et al.
Gen er ation of Cp′′Zr (C6F5)(CNtBu )2{η5-C4H4BC6F5} (4H).
This compound was not isolated but characterized spectro-
scopically. To a solution of 1H (0.03 g, 0.04 mmol) in C7D8 (0.5
mL) at -20 °C was added tert-butylisocyanide (0.05 mL, 0.37
g, 0.44 mmol). The red solution rapidly became yellow and
contained 4H in essentially 100% yield. After 1 h at room
temperature the color had changed to golden, and the solution
contained 5H with only traces of 4H. 11B{1H} NMR (C6D6, 25
°C): δ 28.8.
(cyclopentadienyl)zirconium complexes, where such fac-
ile rearrangements are not observed. Since C6F5 transfer
reactions are usually associated with the deactivation
of B(C6F5)3-activated catalysts, the observed reaction
sequence may shed some light on the varied deactiva-
tion pathways that are possible in some catalytic
systems and may help to explain the differences in
stability and lifetime between half-sandwich and met-
allocene catalysts.
The triple-decker compounds 8, when activated with
MAO, polymerize ethene but react only slowly with
AlMe3. This is in contrast to the behavior of mono-
nuclear borole complexes 1, which were shown earlier
to possess good catalytic activity without an induction
period.4 It is concluded that the triple-decker complexes
described here are unlikely to be the source of the
polymerization activity seen previously. This conclusion
is further supported by the fact that Cp′′Zr(C6F5){CH2C-
(Me)CHCHB(C6F5)2} in toluene-d8 at 60 °C converts
exclusively into the mononuclear species 1Me, with no
sign for the formation of triple-deckers or any other
products.
Gen er a tion of Cp ′′Zr (C6F 5)(CNtBu )2{η5-(3-MeC4H3-
BC6F 5)} (4Me). This compound was not isolated but charac-
terized spectroscopically. To a solution of 1Me (0.03 g, 0.04
mmol) in C7D8 (0.5 mL) at -20 °C was added tert-butyliso-
cyanide (0.05 mL, 0.37 g, 0.44 mmol). The red-brown solution
rapidly became yellow. The NMR spectrum showed that
conversion to 4Me was essentially complete. After 1 h at room
temperature the color had changed to golden, and the solution
contained 5Me with only traces of 4Me. 11B{1H} NMR (C6D6,
25 °C): δ 25.5.
Cp ′′Zr {η2-(C6F 5CNtBu )}(CNtBu ){η5-C4H4BC6F 5} (5H). A
solution of 1H (1.11 g, 1.44 mmol) in toluene (50 mL) at -78
°C was treated with tert-butylisocyanide (0.50 mL, 0.37 g, 4.42
mmol). The initial purple-red solution rapidly became yellow-
orange. The reaction was allowed to reach room temperature
and stirred for 16 h, at which time the color was golden yellow.
Removal of volatiles left a yellow solid, which was extracted
into light petroleum (60 mL). Concentrating to ca. 15 mL and
cooling to -20 °C provided the title compound as a yellow
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were performed
under nitrogen using standard Schlenk techniques. Solvents
were distilled under nitrogen from sodium (toluene), sodium
benzophenone (diethyl ether, tetrahydrofuran), and sodium-
potassium alloy (light petroleum, bp 40-60 °C). Deuterated
solvents were stored over 4 Å molecular sieves and degassed
by several freeze-thaw cycles. The compounds CpZr(crotyl)-
(butadiene),23 Cp′′Zr(crotyl)(butadiene) (6d ),13 Cp′′Zr(C3H5)-
(isoprene),13 Cp′′Zr(C6F5)(OEt2){η5-C4H4BC6F5} (1H),4 and Cp′′Zr-
(C6F5)(OEt2){η5-(3-MeC4H3BC6F5)} (1Me)4 were prepared
according to published procedures. tert-Butylisocyanide and
pivalonitrile were used as purchased. NMR spectra were
recorded on a Bruker DPX300 spectrometer. 1H NMR spectra
are referenced to residual solvent protons, 19F (282.2 MHz) is
relative to CFCl3, and 11B (96.2 MHz) is relative to BF3‚OEt2.
Cp ′′Zr (C6F 5)(NCMe){η5-C4H4BC6F 5} (2H). A solution of
1H (0.58 g, 0.75 mmol) in toluene (40 mL) at 0 °C was treated
with acetonitrile (0.3 mL, 0.23 g, 5.70 mmol). The initial red
solution rapidly became deep purple. The reaction was left to
stir at room temperature for 30 min. Removal of the volatiles
in vacuo and subsequent washing of the residue with light
petroleum (2 × 10 mL) provided the title compound as a deep
crystalline solid, yield 0.96 g (77.2%). Anal. Calcd for C37H43
-
BF10N2Si2Zr‚0.5C6H14: C, 52.97; H, 5.56; N, 3.09. Found: C,
53.04; H, 5.49; N, 3.06. 11B{1H} NMR (C6D6, 25 °C): δ 26.8.
Single crystals were obtained from petroleum ether at -20 °C.
Cp ′′Zr (η2-C6F 5CNt Bu )(CNt Bu ){η5-(3-Me C4H 3BC6F 5)}
(5Me). Following the procedure given for 5H, the compound
was made from 1Me (0.250 g, 0.33 mmol) and tert-butyliso-
cyanide (0.5 mL, 0.37 g, 4.42 mmol) as a yellow microcrystal-
line solid. NMR showed the presence of a major and minor
diastereomer; only the major isomer was fully characterized.
Yield: 0.138 g (49.2%). Anal. Calcd for C38H45BF10N2ZrSi2: C,
51.99; H, 5.17; N, 3.19. Found: C, 52.42; H, 5.22; N, 3.11.
Cp′Zr (η3-C4H7)(η4-bu tadien e) (6a). The complex was made
following the procedure given for CpZr(C4H7)(C4H6).20 A solu-
tion of Cp′ZrCl3(dme) (4.31 g, 10.14 mmol) dissolved in
tetrahydrofuran (100 mL) at 0 °C was treated with a solution
of crotylmagnesium chloride (90 mL, 0.35 M in thf, 31.5 mmol).
The reaction was allowed to warm to room temperature and
stirred for 16 h. The color changed from pale yellow to deep
maroon over the course of the reaction, and there was some
evolution of gas. After removal of volatiles in vacuo the solid
residue was extracted with light petroleum (2 × 50 mL).
Concentration and cooling to -20 °C overnight afforded the
title compound as a red microcrystalline solid, yield 3.03 g
purple solid, yield 0.42 g (75.8%). Anal. Calcd for C32H34BF10
-
NSi2Zr: C, 47.15; H, 3.82; N, 1.90. Found: C, 47.26; H, 3.81;
N, 1.70. 11B{1H} NMR (C6D6, 25 °C): δ 32.2.
Cp ′′Zr (C6F 5)(NCtBu ){η5-C4H4BC6F 5} (3H). Following the
procedure given for 2H, compound 3H was made from 1H (1.03
g, 1.33 mmol) and pivalonitrile (0.4 mL, 0.30 g, 3.64 mmol) as
(88.5%). Anal. Calcd for
Found: C, 56.36; H, 7.27.
C16H26SiZr: C, 56.91; H, 7.76.
CpMeZr (η3-C4H7)(η4-bu tadien e) (6b). Following the method
described for 6a , 6b was prepared as a maroon solid in 77.6%
yield. Anal. Calcd for C14H20Zr: C, 60.16; H, 7.21. Found: C,
59.57; H, 7.01.
a deep purple solid, yield 0.79 g (75.8%). Anal. Calcd for C32H34
-
BF10NSi2Zr‚0.25C7H8: C, 50.43; H, 4.51; N, 1.74. Found: C,
50.20; H, 4.46; N, 1.56. 11B{1H} NMR (C6D6, 25 °C): δ 32.4.
Single crystals were obtained from benzene-d6 solution at room
temperature; they contained 1.5 molecules of benzene-d6 per
molecule of 3H.
Gen er a tion of Cp ′Zr (C6F 5){CH2CHCHCHB(C6F 5)2} (7a ).
To a solution of 6a (0.030 g, 0.089 mmol) in C7D8 (0.3 mL)
was added at room temperature a solution of B(C6F5)3 (0.045
g, 0.088 mmol) in C7D8 (0.3 mL). The color immediately became
dark red. The mixture contained 7a and butene. 11B{1H} NMR
(C7D8, 20 °C): δ 44.6 (vbr). After 48 h at room temperature
the solution contained mainly 8a .
Gen er a tion of Cp RZr (C6F 5){CH2CHCHCHB(C6F 5)2} (7b,
Cp R ) Cp Me; 7c, Cp R ) Cp ). Following the procedure for 7a ,
7b and 7c were similarly generated and characterized in
solution.
11B{1H} NMR (C7D8, 20 °C): 7b: δ 43.6 (vbr). 7c: δ 43.5
(vbr).
Cp ′′Zr (C6F 5)(NCtBu ){η5-(3-MeC4H3BC6F 5)} (3Me). Fol-
lowing the procedure given for 2H, the compound was made
from 1Me (0.430 g, 0.55 mmol) and pivalonitrile (0.10 mL, 0.05
g, 0.60 mmol) as a deep blue solid, yield 0.312 g (71.8%). Anal.
Calcd for
C33H36BF10NSi2Zr: C, 49.87; H, 4.57; N, 1.76.
Found: C, 49.48; H, 4.48; N, 1.62. 11B{1H} NMR (C6D6, 25
°C): δ 31.7.
(23) Blenkers, J .; de Liefde Meijer, H. J .; Teuben, H. J . Recl. Trav.
Chim. Pays-Bas 1980, 99, 216. Erker, G.; Berg, K.; Benn, R.; Schroth,
G. Chem. Ber. 1985, 118, 1383.

B(C6F5)3 as C6F5 Transfer Agent
Organometallics, Vol. 20, No. 19, 2001 4091
Zr 2Cp ′2(C6F 5)2{µ-η5:η5-C4H 4BCH 2-η3,KF -CH CH CH B-
(C6F 5)3} (8a ). A solution of 6a (0.98 g, 2.90 mmol) in toluene
(100 mL) at -78 °C was treated with a cold (-78 °C) solution
of B(C6F5)3 (1.53 g, 2.99 mmol) in toluene (100 mL). The
mixture immediately turned orange. Warming to room tem-
perature over 2 h gave a deep red solution. The volatiles were
removed in vacuo, and toluene (100 mL) was introduced. The
mixture was then stirred at room temperature for 2 days,
during which time an orange color developed. After removal
of the solvent the orange residue was extracted with light
petroleum (2 × 100 mL) and the filtrate concentrated and
cooled to -20 °C to afford the title compound as an orange
microcrystalline solid, yield 1.63 g (80.1%). Anal. Calcd for
C54H35B2F25Zr2Si2: C, 45.71; H, 2.49. Found: C, 45.13; H, 3.20.
11B{1H} NMR (C7D8, 20 °C): δ 1.5 (vbr) (C4H4B), -13.0
(-CHB(C6F5)3).
X-r a y Cr ysta llogr a p h y. 3H. A suitable crystal was coated
in an Nujol oil and mounted in a nitrogen stream at 140 K on
a Rigaku R-Axis II image plate diffractometer equipped with
a rotating anode X-ray source (Mo KR radiation) and graphite
monochromator. Using 4° oscillations, 46 exposures of 28 min
each were made. Data were processed using the DENZO/
SCALEPACK programs.23 The structure was determined by
the direct methods routines in the SHELXS program24 and
refined by full-matrix least-squares methods (on F2) in
SHELXL.25 The non-hydrogen atoms were refined with aniso-
tropic thermal parameters. Hydrogen atoms were constrained
to idealized positions. Crystal data of 3H: C32H34BF10NSi2Zr‚
1.5(C6D6), fw 898.0; monoclinic, P21/c; a ) 11.853(1) Å, b )
28.977(1) Å, c ) 12.983(3) Å; R ) 90°, â ) 106.25(1)°, γ ) 90°;
U ) 4281.1(11) Å3; Z ) 4; Dcalc )1.393 Mg/m3; µ ) 0.386 mm-1
;
F(000) ) 1836; 2.16° e θ e 25.50°; -14 e h e 14, -33 e k e
32, -15 e l e 15; 14 745 reflections collected, of which 7608
were independent [Rint ) 0.0310] and 5789 observed [I >2σ(I)];
data/parameters 7608/505; goodness of fit ) 1.039; final R
indices [I >2σ(I)] R1 ) 0.037, wR2 ) 0.090; R indices (all data)
R1 ) 0.054, wR2 ) 0.097.
Zr 2Cp Me 2(C6F 5)2{µ-η5:η5-C4H 4BCH 2-η3,KF -CH CH CH B-
(C6F 5)3} (8b). A solution of 6b (0.37 g, 1.33 mmol) in toluene
(50 mL) at -78 °C was treated with a solution of B(C6F5)3 (0.72
g, 1.41 mmol) in toluene (100 mL) also at -78 °C. On warming
to room temperature under a static vacuum over 2 h the
orange mixture turned deep red. The volatiles were removed
in vacuo, and toluene (100 mL) was introduced. The reaction
was now stirred at room temperature for 2 days, during which
time an orange color developed. The volatiles were removed
in vacuo, and the residue was extracted with ether (100 mL).
Removal of the volatiles in vacuo and washing with light
petroleum (2 × 40 mL) provided 8b, yield 0.67 g (77.3%). Anal.
Calcd for C50H23B2F25Zr2: C, 46.10; H, 1.78. Found: C, 46.51;
H, 2.06. 11B{1H} NMR (C7D8, 20 °C): δ 1.0 (vbr) (C4H4B), -13.1
(-CHB(C6F5)3).
5H. A suitable crystal was coated in inert perfluoropolyether
oil and mounted in a nitrogen stream at 150 K on a Nonius
Kappa CCD area-detector diffractometer. Data collection was
performed using Mo KR radiation (λ ) 0.71073 Å) with the
CCD detector placed 30 mm from the sample via a mixture of
1° φ and ω scans at different θ and κ settings using the
program COLLECT.26 The raw data were processed to produce
conventional data using the program DENZO-SMN.23 The
dataset was corrected for absorption using the program
SORTAV.27 The structure was solved by heavy-atom methods
using SHELXS-9724 and refined by full-matrix least-squares
refinement (on F2) using SHELXL-97.25 All non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were constrained to idealized positions.
Crystal data of 5H: C37H43BF10N2Si2Zr, fw 863.94; triclinic,
P1h; a ) 11.3671(2) Å, b ) 15.9864(3) Å, c ) 25.3180(5) Å; R )
Zr 2C p 2(C 6F 5)2{µ-η5:η5-C 4H 4B C H 2-η3,KF -C H C H C H B -
(C6F 5)3} (8c). Following the procedure for 8b, the compound
was made from 6c (1.24 g, 4.67 mmol) and B(C6F5)3 (2.43 g,
4.76 mmol) as an orange microcrystalline precipitate, yield 2.17
g (72.9%). Anal. Calcd for C48H19B2F25Zr2: C, 45.23; H, 1.50.
Found: C, 44.78; H, 1.81. 11B{1H} NMR (C7D8, 20 °C): δ 1.5
(vbr) (C4H4B), -13.0 (-CHB(C6F5)3).
79.6120(10)°, â ) 86.3340(10)°, γ ) 75.1260(10)°; U
)
;
Zr 2Cp ′′2(C6F 5)2{µ-η5:η5-C4H 4BCH 2-η3,KF -CH CH CH B-
(C6F 5)3} (8d ). A solution of Cp′′Zr(C4H7)(C4H6) (1.63 g, 3.98
mmol) in toluene (30 mL) at -78 °C was treated with a
solution of B(C6F5)3 (1.98 g, 3.87 mmol) also at -78 °C. The
reaction was maintained at this temperature for 30 min and
then was allowed to reach room temperature. The volatiles
were removed in vacuo, toluene (40 mL) was introduced, and
the reaction was stirred at 50 °C for 2 h. Removal of the solvent
in vacuo provided a brown foam, which was extracted with
diethyl ether (50 mL). Concentration of this red solution to
ca. 10 mL and cooling to -20 °C overnight provided 8d as red
crystals, yield 2.56 g (82.3%). Anal. Calcd for C60H51B2F25Si4-
Zr2: C, 46.10; H, 3.29. Found: C, 45.36; H, 3.28. 11B{1H} NMR
(C7D8, 20 °C): δ 3.0 (vbr) (C4H4B), -12.8 (-CHB(C6F5)3).
Gen er a l P r oced u r e for Eth en e P olym er iza tion . A
magnetically stirred 50 mL reactor was flame-dried in vacuo
prior to being charged with 40 mL of dry and degassed toluene.
The solvent was equilibrated at the desired polymerization
temperature and saturated with ethene (1 bar). Aliquots of a
toluene solution of the aluminum alkyl activator were injected,
followed by a solution of the zirconium complex in toluene.
The pressure was maintained at 1 bar throughout. The
reaction was terminated by the injection of 2 mL of methanol.
The polymer was precipitated with acidified methanol, washed
with methanol, and dried at 60-80 °C for 24 h.
4372.97(14) Å3; Z ) 4; Dcalc )1.312 Mg/m3; µ ) 0.375 mm-1
F(000) ) 1768; 3.43° e θ e 26°; -14 e h e 14, -19 e k e 19,
-27 e l e 31; 42 596 reflections collected, of which 16 775 were
independent [Rint ) 0.097] and 11 825 observed [I >2σ(I)]; data/
parameters 16775/979; goodness of fit ) 1.032; final R indices
[I >2σ(I)] R1 ) 0.0656, wR2 ) 0.1603; R indices (all data) R1
) 0.0962, wR2 ) 0.1765.
Ack n ow led gm en t. This work was supported by the
Engineering and Physical Sciences Research Council.
Su p p or tin g In for m a tion Ava ila ble: Full listing of crys-
tallographic details for 3H and 5H. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM010348I
(24) Otwinowski Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., J r., Sweet, R. M., Eds.; Academic Press: New York, 1996; Vol.
276, p 307.
(25) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(26) Sheldrick, G. M. SHELXL-97, Program for crystal structure
refinement; University of Go¨ttingen: Germany, 1997.
(27) Collect, data collection software; Nonius B.V.: Delft, The
Netherlands, 1999.
(28) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33