Synthesis and exchange reactions of Ni-dimine-COD, acetylene and olefin complexes

Article abstract of DOI:10.1039/c001312a

The complexes MesDADNi(COD) (1), DippDADNi(COD) (2), DippDABNiCOD (3) and DippBIANNi(COD) (5) were readily prepared from Ni(COD)₂. The analogous reaction of the ligand MesBIAN afforded (MesBIAN)₂Ni (4). The related Ni alkyne complexes DADNi(PhCCPh) (6), DippDABNi(PhCCPh) (7) and DippBIANNi(PhCCPh) (8) are readily prepared by addition of alkyne to solutions of the COD species. The analogous reactions employing tBuDAD ligand with either Ni(COD)₂ alone or Ni(COD)₂ and PhCCPh led only to the known bis-ligand Ni complex, although tBuDADNi(MeCO₂CCCO ₂Me) (9) is readily prepared. In a similar fashion, the species DippDADNi(MeCO₂CCCO₂Me) (10), DippDABNi(Me ₃SiCCSiMe₃) (11), DippDABNi(MeCO₂CCCO ₂Me) (12) and DippBIANNi(MeCO₂CCCO₂Me) (13) were prepared. Reactions with olefins afforded DippDABNi(MeCO ₂CHCHCO₂Me) (14), DippDABNi(MeCO₂CHCHPh) (15). Employing isolated (3) or (15) in exchange reactions afforded (7), (11) (14) and (15). Similarly (6) served as a precursor to (10) while (11) reacts with PhCCPh to give (7). The solid state structures of (1), (3)-(7), (9), (11) and (15) are reported. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/c001312a

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Dalton
Transactions
An international journal of inorganic chemistry
www.rsc.org/dalton
Volume 39 | Number 25 | 7 July 2010 | Pages 5745–5924
ISSN 1477-9226
PAPER
Sgro and Stephan
HOT ARTICLE
Synthesis and exchange reactions of
Ni-dimine-COD, acetylene and olefin
complexes
Lotz et al.
Thiophene decorated with Fischer
carbene ligands
1477-9226(2010)39:25;1-4

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis and exchange reactions of Ni-dimine-COD, acetylene and
olefin complexes†
Michael J. Sgro and Douglas W. Stephan*
Received 21st January 2010, Accepted 17th March 2010
First published as an Advance Article on the web 6th April 2010
DOI: 10.1039/c001312a
The complexes MesDADNi(COD) (1), DippDADNi(COD) (2), DippDABNiCOD (3) and
DippBIANNi(COD) (5) were readily prepared from Ni(COD)2. The analogous reaction of the ligand
≡
MesBIAN afforded (MesBIAN)2Ni (4). The related Ni alkyne complexes DADNi(PhC CPh) (6),
≡
≡
DippDABNi(PhC CPh) (7) and DippBIANNi(PhC CPh) (8) are readily prepared by addition of
alkyne to solutions of the COD species. The analogous reactions employing tBuDAD ligand with either
≡
Ni(COD)2 alone or Ni(COD)2 and PhC CPh led only to the known bis-ligand Ni complex, although
≡
tBuDADNi(MeCO2C CCO2Me) (9) is readily prepared. In a similar fashion, the species
≡
≡
DippDADNi(MeCO2C CCO2Me) (10), DippDABNi(Me3SiC CSiMe3) (11), DippDABNi-
(MeCO2C CCO2Me) (12) and DippBIANNi(MeCO2C CCO2Me) (13) were prepared. Reactions with
≡
≡
=
=
olefins afforded DippDABNi(MeCO2CH CHCO2Me) (14), DippDABNi(MeCO2CH CHPh) (15).
Employing isolated (3) or (15) in exchange reactions afforded (7), (11) (14) and (15). Similarly (6) served
≡
as a precursor to (10) while (11) reacts with PhC CPh to give (7). The solid state structures of (1),
(3)–(7), (9), (11) and (15) are reported.
synthetic procedures to low valent Ni-dimine complexes. To this
Introduction
end, we report herein, the synthesis and characterization of Ni-
diimine complexes containing COD, alkyne and olefin ligands.
Ligand exchange reactions are examined and the general utility
and limitations of this approach are discussed.
Ni(II)-complexes containing diimine ligands have drawn consid-
erable attention as a result of the discovery of the Brookhart
polymerization catalysts.1-4 More recently such complexes have
also been shown to exhibit antimicrobial activity.5 Low valent
Ni-dimine complexes have drawn lesser attention, despite the
fact that it was in 1966 that Balch and Holm6 first studied ho-
moleptic bis-ligand Ni-diimine complexes. While these complexes
appear to be formally Ni(0) complexes, these and subsequent
authors7,8 have described the ability of these ligands to act as
electron acceptors and thus formally stabilize higher oxidation
states of homoleptic bis-ligand metal-diimine complexes. Several
formally Ni(0) diimine complexes have been described in the
literature over the years. For example, the Ni-dimine-alkyne
Experimental section
All reactions and manipulations of compounds described were
performed under an N2 atmosphere using Schlenk techniques,
or under an inert N2 atmosphere in a MBraun Labmaster
glove box. All glassware was dried overnight at 110 ◦C and
evacuated for 30 min prior to use. THF, CH2Cl2, Et2O, pentane
and hexane were obtained from Caledon Laboratories and dried
by dual-alumina columns of the Innovative Technology Inc.
Controlled Atmospheres Solvent Purification System. Solvents
complexes of the form (DippDAD)Ni(alkyne)9 (DippDAD =
10
=
((C6H3iPr2)N CH)2) have been reported to be intermediates
˚
were stored in the glove box over 4 A molecular sieves. Ni(COD)2
in the catalysis of the cyclotetramerization of propargylic alco-
was obtained from Strem Chemicals Inc. All of the reagents
from Aldrich Chemical Co. and Strem Chemical Inc. were
used without further purification. N,N¢-bis(2,6-diisopropyl-
hol using the precatalyst (DippDAD)Ni(COD).11,12 The related
=
dimeric Ni-diimine olefin complex ((DippDAD)Ni)2(CH2 CH-
(CO2Me)CH(CO2Me) CH2) has also been reported. More
recently, the synthesis and characterization of the related
species Ni(MesDAB)2, [Ni(MesDAB)(COD)] and Ni(MesDAB)-
13
=
=
phenyl)1,4-diazabutadiene (DippDAD = ((C6H3iPr2)N CH)2),
N,N¢-bis(2,4,6-trimethylphenyl)1,4-diazabutadiene (MesDAD =
=
((C6H2Me3)N CH)2),
acenaphthene (DippBIAN = ((C6H3iPr2)N C)2C10H6), N,N¢-
1,2-bis((2,6-diisopropylphenyl)imino)-
14
≡
=
(PhC CPh) (MesDAB = ((C6H2Me3)N CMe)2) was published.
The established catalytic activity of Ni-diimine complexes and
the ease of ligand preparation and variation prompted our interest.
In seeking to examine the potential of such species in other
catalytic applications where oxidative addition might initiate
reactions, we began with the development of general and versatile
=
=
bis(tert-butyl)1,4-diazabutadiene (t-BuDAD = (t-BuN CMe)2),
N,N¢-bis(2,6-diisopropylphenyl)2,3-butanediimine (DippDAB =
=
((C6H3iPr2)N CMe)2), and N,N¢-bis(2,4,6-trimethylphenyl)2,3-
2-6
=
butanediimine (MesDAB = ((C6H2Me3)N CMe)2).
NMR samples were prepared in the glove box, capped and
sealed with parafilm. C6D6 was purchased from the Cambridge
Isotope Laboratories and was dried over Na/benzophenone,
Department of Chemistry, University of Toronto, 80 St. George St. Toronto,
Ontario, Canada M5S 3H6. E-mail: dstephan@chem.utoronto.ca; Tel: 416-
946-3294
† CCDC reference numbers 762663–762671. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c001312a
1
distilled, degassed and stored under N2 in a glove box. H and
13C NMR spectra were recorded on Varian Mercury or INOVA
400 MHz spectrometers and internally referenced to deuterated
5786 | Dalton Trans., 2010, 39, 5786–5794
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benzene (d = 7.16 ppm (1H), 128.06 ppm (13C)) relative to Me4Si.
Combustion analyses were performed in house employing a Perkin
Elmer 2400 Series II CHNS Analyzer.15 UV-Visible spectra were
collected as 10-6 M solutions on a Perkin Elmer Lambda 12 UV-
Visible spectrometer. e quoted in mol-1 cm-1.
slurry of Ni(COD)2 and Et2O (200 mg, 0.728 mmol; 2 mL). No
immediate change was observed. A catalytic amount of 1-chloro-2-
fluorobenzene (10 mg, 0.073 mmol) was then added to the solution.
The solution quickly turned black, and within 5 min was deep
purple. The reaction mixture was allowed to stir for 8 h before
the solvent was removed in vacuo giving a purple solid. The crude
product was dissolved in a minimal amount of hexane and stored
in a -35 ◦C freezer. A purple solid precipitated from the mixture
and was isolated by filtration over a fine porosity filter frit. The
remaining solution was stored in the freezer and the above was
repeated. The product was obtained as a purple solid in 76% yield
(314 mg, 0.551 mmol). 1H NMR (C6D6): 7.29 (m, 6H, Ar-H), 3.99
(s, 4H, COD-CH), 3.17 (sept, 4H, 3JH-H = 6.80 Hz, CHMe2), 2.33
(m, 4H, COD-CH2), 1.39 (d, 12H, 3JH-H = 6.80 Hz, CHMe2), 1.02
(d, 12H, 3JH-H = 6.80 Hz, CHMe2), 0.39 (s, 6H, N=CMe), 0.29 (s,
4H, COD-CH2), 13C (C6D6): 151.91 (DAB-N=C), 146.76 (Ar-i-C),
139.15 (Ar-o-C), 124.98 (Ar-p-C), 123.45 (Ar-m-C), 86.56(COD-
CH), 30.35 (COD-CH2), 27.78 (CHMe2), 25.04 (CHMe2), 23.97
(CHMe2), 21.42 (DABN=CMe), Anal. Calc. for C36H52N2Ni: C,
75.64; H, 9.18; N, 4.90. Found: C, 74.47; H, 9.21; N, 4.98,15 UV-Vis:
lmax (e)/nm 288 (10100), 520 (3600).
Synthesis of MesDADNi(COD) (1), DippDADNi(COD) (2),16
DippBIANNi(COD) (5)
These compounds were prepared in a similar fashion and thus
only one preparation is detailed. MesDAD was dissolved in THF
(213 mg, 0.728 mmol; 2 mL) giving a light yellow solution that
was combined with a light yellow slurry of Ni(COD)2 and THF
(200 mg, 0.728 mmol; 2 mL). The solution immediately changed
from yellow to orange and finally to brown over the course of
minutes. The solution was allowed to stir overnight before the
solvent was removed in-vacuo leaving a brown solid. The solids
were dissolved in a minimal amount of hexane and were placed
in a -35 ◦C freezer to precipitate the purified product. The
precipitated product was filtered on a fine porosity filter frit and
the remaining solution was cooled again for further precipitation.
MesDADNiCOD was obtained as a brown solid in 95% yield
1
(317.0 mg, 0.691 mmol). H NMR (C6D6): 7.84 (s, 2H, DAD-
Synthesis of (MesBIAN)2Ni (4)
=
N CH), 7.04 (s, 4H, Ar-H), 3.90 (s, 4H, COD-CH), 2.52 (m, 4H,
COD-CH2), 2.38 (s, 6H Ar-p-Me), 2.31 (s, 12H, Ar-o-Me), 1.53 (m,
4H, COD-CH2) 13C NMR (C6D6): 154.20 (DAB-CH), 140.78 (Ar-
i-C), 133.06 (Ar-m-C), 128.75 (Ar-o-CH), 128.06 (Ar-p-C), 87.74
(COD-CH), 30.61 (COD-CH2), 21.01 (Ar-p-Me), 18.00 (Ar-o-Me)
Anal. Calc. for C28H36N2Ni: C, 73.21; H, 7.90; N, 6.10. Found: C,
72.37; H, 7.84;15 N, 6.16 UV-Vis: lmax (e)/nm 276 (20700), 472
MesBIAN was dissolved in THF (606 mg, 1.456 mmol; 2 mL)
giving an orange solution that was added to a light yellow slurry
of Ni(COD)2 and THF (200 mg, 0.728 mmol; 2 mL). Over the
course of 5 min the solution changed from orange to deep purple-
brown. The reaction mixture was allowed to stir overnight before
the solvent was removed in vacuo giving a purple-brown solid. The
crude product was dissolved in a minimal amount of hexane and
stored in a -35 ◦C freezer. A purple-brown solid precipitated from
the mixture and was isolated by filtration over a fine porosity filter
frit. The remaining solution was stored in the freezer and the above
was repeated. The product was obtained as a purple solid in 72%
1
(10600). (2):1 brown solid, 79% yield (314 mg, 0.578 mmol). H
NMR (C6D6): 7.91 (s, 2H, DAD-CH), 7.29 (t, 2H, 3JH-H = 7.40 Hz,
Ar-p-CH), 7.25 (d, 4H, 3JH-H = 7.40 Hz, Ar-m-CH), 3.92 (s, 4H,
3
COD-CH), 3.34 (sept, 4H, JH-H = 6.80 Hz, CHMe2), 2.42 (m,
4H, COD-CH2), 1.42 (br s, 4H, COD-CH2), 1.39 (d, 12H, 3JH-H
=
6.80 Hz, CHMe2), 1.10 (d, 12H, JH-H = 6.80 Hz, CHMe2) 13C
NMR (C6D6): 154.02 (DAB-CH), 141.48 (Ar-i-C), 139.63 (Ar-
o-C), 125.43 (Ar-m-C), 123.00(Ar-p-C), 88.66 (COD-CH), 30.50
(COD-CH2), 27.84 (CHMe2), 26.39 (CHMe2), 22.89 (CHMe2),
Anal. Calc. for C34H48N2Ni: C, 75.13; H, 8.91; N, 5.16. Found:
C, 74.64; H, 9.10; N, 5.32 UV-Vis: lmax (e)/nm 275 (15900), 479
3
yield (466 mg, 0.523 mmol). 1H NMR (C6D6): 7.80 (d, 4H, 3JH-H
=
8.15 Hz, BIAN-o-Ar-H), 6.80 (s, 8H, mes-m-Ar-H), 6.75 (d, 4H,
3
3JH-H = 8.15 Hz, BIAN-p-Ar-H), 6.46 (t, 4H, JH-H = 8.15 Hz,
BIAN-m-Ar-H), 2.53 (s, 24H, mes-o-Me), 2.41 (s, 12H, mes-p-
Me), 13C (C6D6): 154.87 (BIAN-N C), 143.39 (Ar-C), 142.40 (Ar-
=
C), 134.92 (Ar-C), 134.00 (Ar-C), 131.38 (Ar-C), 129.59 (Ar-C),
129.12 (Ar-C), 127.52 (Ar-C), 121.76 (Ar-C), 115.32 (Ar-C), 21.18
(CHMe2), 18.76 (CHMe2) Anal. Calc. for C60H56N4Ni: C, 80.80;
H, 6.33; N, 6.29. Found: C, 79.62; H, 6.44; N, 6.21,15 UV-Vis: lmax
(e)/nm 268 (27600), 326 (17600), 555 (16700), 884 (12300),
1
(7900). (5): brown solid, 77% yield (373 mg, 0.559 mmol). H
3
NMR (C6D6): 7.49 (d, 2H, JH-H = 8.15 Hz, Ar-H), 7.43 (t, 2H,
3JH-H = 7.45 Hz, Ar-H), 7.35(d, 4H, 3JH-H = 7.45 Hz, Ar-H), 6.69
3
3
(t, 2H, JH-H = 7.45 Hz, Ar-H), 6.47 (d, 2H, JH-H = 6.97 Hz,
3
Ar-H), 4.20 (s, 4H, COD-CH), 3.71 (sept, 4H, JH-H = 6.72 Hz,
CHMe2), 2.54 (br s, 4H, COD-CH2), 1.43 (d, 12H, 3JH-H = 6.72 Hz,
CHMe2), 1.40 (s, 4H, COD-CH2), 0.93 (d, 12H, 3JH-H = 6.72 Hz,
≡
Synthesis of DippDADNi(PhC CPh) (6),
CHMe2), 13C (C6D6): 152.00 (N C), 151.89 (Ar-i-C), 138.75 (Ar-
≡
≡
DippDABNi(PhC CPh) (7), DippBIANNi(PhC CPh) (8)
=
C), 137.30 (Ar-C), 133.24 (Ar-C), 132.39 (Ar-C), 129.09 (Ar-C),
125.88 (Ar-C), 124.08 (Ar-C), 124.00 (Ar-C), 119.24 (Ar-C), 88.98
(COD-CH), 30.20 (COD-CH2), 28.24 (CHMe2), 25.43 (CHMe2),
24.07 (CHMe2), Anal. Calc. for C44H52N2Ni: C, 79.15; H, 7.86; N,
4.20. Found: C, 77.82; H, 7.93; N, 4.18,15 UV-Vis: lmax (e)/nm 277
(16200), 440 (6700), 541 (6400).
These compounds were prepared in a similar fashion and thus
only one preparation is detailed. DippDAD was dissolved in THF
(274 mg, 0.728 mmol; 2 mL) giving a bright yellow solution that
was added to a yellow slurry of Ni(COD)2 and THF (200 mg,
0.728 mmol; 2 mL). The colour immediately changed to brown,
≡
then a clear colorless solution of PhC CPh in THF (130 mg,
0.728 mmol; 2 mL) was added. The solution immediately changed
from yellow to a deep blue. The reaction was allowed to stir
overnight giving a deep blue mixture. The volatiles were removed
in vacuo giving a blue solid. The crude product was washed with
Synthesis of DippDABNi(COD) (3)
DippDAB was dissolved in Et2O (294 mg, 0.728 mmol; 2 mL)
giving a light yellow solution that was added to a light yellow
This journal is
The Royal Society of Chemistry 2010
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pentane, the blue eluent was removed and the precipitate was
C, 51.52; H, 6.95; N, 7.11, UV-Vis: lmax (e)/nm 246 (11200), 382
dried to a blue solid. The product was obtained in 79% yield
(600), 657 (6400) (10): blue solid, 91% yield (384 mg,0.665 mmol).
1
1
=
=
(354 mg, mmol). H NMR (C6D6) 9.08 (s, 2H, N CH), 7.49 (t,
H NMR (C6D6): 8.23 (s, 2H, DAD-N CH), 7.25 (m, 6H, DAD-
3
3
3
2H, JH-H = 7.60 Hz, Ar-H), 7.42 (d, 4H, JH-H = 7.20 Hz, Ar-
Ar-H), 3.32 (sept, 4H, JH-H = 6.80 Hz, CHMe2), 3.12 (s, 6H,
3
3
3
H), 7.36 (d, 4H, JH-H = 7.60 Hz, Ar-H), 7.04 (t, 4H, JH-H
=
=
O-Me), 1.37 (d, 12H, JH-H = 6.80 Hz, CHMe2), 1.07 (d, 12H,
3
7.20 Hz, Ar-H), 6.98 (m, 2H, Ar-H), 3.46 (sept, 4H, JH-H
3JH-H = 6.80 Hz, CHMe2), 13C (C6D6): 159.29 (DAD-N=CH),
155.04 (DAD-Ar-i-C), 151.36, 139.26 (Ar-C), 126.54 (Ar-C),
123.23 (Alkyne-C), 117.67 (Ar-C), 51.11 (O-Me), 28.77 (CHMe2),
24.30 (CHMe2), 22.87 (CHMe2), Anal. Calc. for C32H42N2O4Ni:
C, 66.57; H, 7.33; N, 4.85. Found: C, 65.19; H, 7.35; N, 4.59,15
UV-Vis: lmax (e)/nm 378 (2200), 644 (6700).
3
6.80 Hz, CHMe2), 1.19 (d, 12H, JH-H = 6.80 Hz, CHMe2), 1.09
3
13
=
(d, 12H, JH-H = 6.80 Hz, CHMe2). C (C6D6) 155.72 (N CH),
≡
152.95 (Ar-i-C), 138.39 (Ar-C), 130.15 (C C), 127.96 (Ar-C),
127.33 (Ar-C), 126.21 (Ar-C), 123.77 (Ar-C), 118.83 (Ar-C),
28.56 (CHMe2), 24.24 (CHMe2), 22.83 (CHMe2) Anal. Calc. for
C28H36N2Ni: C, 78.30; H, 7.56; N, 4.57. Found: C, 76.99; H, 7.64;
N, 4.85,15 UV-Vis: lmax (e)/nm 261 (19600), 300 (7700), 370 (3100),
661 (5500) (7): green solid, 80% yield (375 mg, mmol). 1H NMR
≡
DippDABNi(Me3SiC CSiMe3) (11)
(C6D6) 7.46 (t, 2H, 3JH-H = 7.60 Hz, Ar-H), 7.36 (d, 4H, 3JH-H
=
7.60 Hz, Ar-H), 7.13 (m, 4H, Ar-H), 7.01 (m, 6H, Ar-H), 3.19
DippDAB was dissolved in THF (294 mg, 0.728 mmol; 2 mL)
giving a bright yellow solution that was added to a yellow
slurry of Ni(COD)2 and THF (200 mg, 0.728 mmol; 2 mL). A
3
3
(sept, 4H, JH-H = 6.80 Hz, Ar- CHMe2), 1.22 (d, 12H, JH-H
=
3
6.80 Hz, CHMe2), 1.09 (d, 12H, JH-H = 6.80 Hz, CHMe2), -
13
=
=
≡
0.03 (s, 6H, N CMe); C (C6D6): 158.74 (N C), 152.05 (Ar-i-
clear colourless solution of Me3SiC CSiMe3 in THF (128 mg,
≡
C), 138.44 (Ar-C), 129.81(C C), 129.43 (Ar-C), 126.38 (Ar-C),
125.82 (Ar-C), 124.16 (Ar-C), 123.97 (Ar-C), 28.72 (CHMe2),
0.728 mmol; 2 mL) was then added. The solution slowly changed
from yellow to pale orange. After 1 night of stirring the solution
was black, but on continued stirring for 3 more days, a deep blue
solution was obtained. The volatiles were removed in vacuo giving
a dark blue solid. The crude product was washed with pentane,
the purple eluent was removed and the precipitate was dried to a
blue solid. The product was then dissolved in a minimal amount
of diethyl ether and stored in the freezer to precipitate the blue
product. The precipitated product was filtered on a fine porosity
filter frit and the remaining solution was cooled again for further
precipitation. The product was obtained in 73% yield (336 mg,
=
23.38 (CHMe2), 23.31 (CHMe2), 19.91(DAB-N CMe). Anal.
Calc. for C42H50N2Ni: C, 78.62; H, 7.86; N, 4.31. Found: C, 78.16;
H, 8.04; N, 4.47, UV-Vis: lmax (e)/nm 267 (19800), 301 (8300),
411 (1600), 683 (6400) (8) brown-green solid, 72% yield (387 mg,
1
0.524 mmol). H NMR (C6D6) 7.68 (d, 2H,3JH-H = 8.20 Hz, Ar-
3
3
H), 7.62 (t, 2H, JH-H = 7.70 Hz, Ar-H), 7.49 (t, 8H, JH-H
=
7.20 Hz, Ar-H), 7.09 (m, 6H, Ar-H), 7.00 (d, 2H, 3JH-H = 7.20 Hz,
Ar-H), 6.61 (t, 4H, 3JH-H = 7.70 Hz, Ar-H), 3.82 (sept, 4H, 3JH-H
=
6.80 Hz, CHMe2), 1.33 (d, 12H, 3JH-H = 6.80 Hz, CHMe2), 1.00 (d,
12H, 3JH-H = 6.80 Hz, CHMe2), 13C (C6D6) 161.40 (N=C), 152.66
(Ar-i-C), 138.48 (Ar-C), 135.60 (Ar-C), 135.51 (Ar-C), 134.27
1
3
531 mmol). H NMR (C6D6): 7.41 (t, 2H, JH-H = 8.30 Hz, Ar-
H), 7.33 (d, 4H, 3JH-H = 8.30 Hz, Ar-H), 2.94 (sept, 4H, 3JH-H
=
3
≡
(Ar-C), 130.12 (C C), 128.64 (Ar-C), 127.20 (Ar-C), 127.18 (Ar-
6.90 Hz, CHMe2), 1.41(d, 12H, JH-H = 6.90 Hz, CHMe2), 1.04
3
C), 126.47 (Ar-C), 125.67 (Ar-C), 124.43 (Ar-C), 119.71 (Ar-C),
116.82 (Ar-C), 29.10 (CHMe2), 23.75 (CHMe2), 23.24 (CHMe2),
Anal. Calc. for C50H50N2Ni: C, 81.41; H, 6.83; N, 3.79. Found:
C, 78.76; H, 7.12; N, 3.94,15 UV-Vis: lmax (e)/nm 264 (35300), 332
(10400), 390 (3400), 533 (5700), 789 (8900).
(d, 12H, JH-H = 6.90 Hz, CHMe2), 0.08 (s, 18H, Me3Si), -1.03
(s, 6H, N CMe), 13C (C6D6) 157.96 (DAB-N=C), 154.53 (DAB-
=
Ar-i-C), 150.02 (Ar-C), 137.45 (Alkyne-C), 125.75 (Ar-C), 123.94
(Ar-C), 28.57 (CHMe2), 23.93 (CHMe2), 23.36 (CHMe2), 21.83
=
=
(DAB-N CMe), 0.95 (N CMe), Anal. Calc. for C36H58N2Si2Ni:
C, 68.24; H, 9.23; N, 4.42. Found: C, 67.98; H, 9.23; N, 4.49,
UV-Vis: lmax (e)/nm 265 (18300), 673 (6800).
≡
Synthesis of tBuDADNi(MeCO2C CCO2Me) (9),
≡
DippDADNi(MeCO2C CCO2Me) (10)
These compounds were prepared in a similar fashion and thus
only one preparation is detailed. tBuDAD was dissolved in
THF (124 mg, 0.728 mmol; 2 mL) giving a clear colourless
solution that was added to a yellow slurry of Ni(COD)2 and
THF (200 mg, 0.728 mmol; 2 mL). A clear colourless solution
≡
Synthesis of DippDABNi(MeCO2C CCO2Me) (12)
A solution of 11 was dissolved in THF giving a blue solution. A
≡
clear colourless solution of MeCO2C CCO2Me in THF was then
added giving no immediate change. The solution was allowed to
stir for 1 day remaining blue. The solvent was removed in vacuo
giving a blue solid. NMR of the crude product shows conversion
to the DMADC complex, free ligand and one additional product
identified as the cyclized DMADC ligand. The cyclized product
could not be separated from complex 12. 1H NMR (C6D6) 7.23 (m,
6H, DAB-Ar–H), 3.11 (sept, 4H, 3JH-H = 6.80 Hz, CHMe2), 3.11
≡
of MeCO2C CCO2Me in THF (103 mg, 0.728 mmol; 2 mL) was
then added. The solution changed immediately to deep-blue. The
reaction mixture was allowed to stir overnight giving a deep blue
solution. The volatiles were removed in vacuo giving a purple-blue
solid. The crude product was washed with pentanes, and a purple
solution was decanted. The resulting blue product was washed
2 more times before the precipitate was dried. The product was
3
(s, 6H, O-Me), 1.43 (d, 12H, JH-H = 6.80 Hz, CHMe2), 1.06 (d,
1
12H, 3JH-H = 6.80 Hz, CHMe2), 0.39 (s, 6H, N CMe) 13C (C6D6)
=
obtained in 78% yield (210 mg, 0.570 mmol). H NMR (C6D6):
=
=
7.45 (s, 2H, DAD-N CH), 3.54 (s, 6H, O-Me), 1.58 (s, 18H, DAB-
165.42 (DAB-N C), 162.70 (DAB-Ar-i-C), 147.97 (Ar-C), 138.94
13
=
=
N CCMe3), C (C6D6): 163.93 (DAD-N C), 150.00 (C(O)O),
123.83 (Alkyne-C), 62.56 (CMe3), 51.12 (O-Me), 30.32 (CMe3),
Anal. Calc. for C16H26N2O4Ni: C, 52.07; H, 7.10; N, 7.59. Found:
(Ar-C), 134.51 (Ar-C), 126.24 (Ar-C), 122.63 (Alkyne-C), 50.99
(O-Me), 29.07 (CHMe2), 23.69 (CHMe2), 23.45 (CHMe2), 18.69
=
(DAB-N CMe)
5788 | Dalton Trans., 2010, 39, 5786–5794
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3
≡
DippBIANNi(MeCO2C CCO2Me) (13)
3JH-H = 6.90 Hz, DAB-p-Ar-H), 6.79 (t, 1H, JH-H = 6.9 Hz,
olefin-p-Ar-H), 6.63 (t, 2H, 3JH-H = 6.90 Hz, olefin-m-Ar-H), 6.28
A sample of 8 was dissolved in THF (100 mg, 0.136 mmol;
2 mL) giving a blue solution. A clear colourless solution of
MeCO2C CCO2Me in THF (19.3 mg, 0.136 mmol; 2 mL) was
(d, 2H,3JH-H = 6.90 Hz, olefin-o-Ar-H), 4.21 (sept, 1H,3JH-H
=
6.20 Hz, CHMe2), 4,12 (sept, 1H, 3JH-H = 6.20 Hz, CHMe2), 3.47
≡
3
(d, 1H), 3.02 (s, 3H, O-Me), 2.57 (sept, 1H, JH-H = 6.20 Hz,
then added giving no immediate change. After 5 min of stirring
the solution turned brown and was allowed to continue stirring
for 1 day. The solvent was removed in vacuo giving a brown solid.
NMR of the crude product shows quantitative conversion to the
desired complex 13. The solid was washed with pentane and a
pale brown solution was decanted leaving a brown precipitate. The
solid was dried and obtained in 71% yield (68 mg, 0.097 mmol). 1H
NMR (C6D6) 7.39 (m, 8H, Ar–H), 6.97 (d, 2H, 3JH-H = 6.80 Hz,
3
CHMe2), 2.49 (s, 3H, O-Me), 2.25 (sept, 1H, JH-H = 6.20 Hz,
3
=
CHMe2), 2.06 (s, 3H, N CMe), 1.56 (d, 3H, JH-H = 6.20 Hz,
3
CHMe2), 1.51 (d, 3H, JH-H = 6.20 Hz, CHMe2), 1.26 (d, 3H,
3JH-H = 6.20 Hz, CHMe2), 1.22 (d, 3H, 3JH-H = 6.20 Hz, CHMe2),
3
1.03 (d, 3H, JH-H = 6.20 Hz, CHMe2), 0.94 (m, 6H, CHMe2)
3
=
0.86 (s, 3H, N CMe), 0.15 (d, 3H, JH-H = 6.20 Hz, CHMe2)
13
=
C (C6D6) 173.76 (C(O)O), 166.93 (DAB-N C), 164.62 (DAB-
=
N C), 147.87 (Ar-C), 145.71 (Ar-C), 140.31 (Ar-C), 139.77 (Ar-
Ar-H), 6.62 (t, 2H, 3JH-H = 7.30 Hz, Ar-H), 3.75 (sept, 4H, 3JH-H
=
=
C), 137.66 (Ar-C), 128.81 (Ar-C), 125.96 (Ar-C), 125.78 (Ar-C),
125.06 (Ar-C), 123.87 (Ar-C), 123.67 (Ar-C), 122.52 (Ar-C), 49.93
(O-Me), 47.73 (olefin-CH), 35.94 (olefin-CH), 29.33 (CHMe2),
29.31 (CHMe2), 28.56 (CHMe2), 28.51 (CHMe2), 24.56 (CHMe2),
24.38 (CHMe2), 24.35 (CHMe2), 24.30 (CHMe2), 23.09 (CHMe2),
22.77 (CHMe2), 22.63 (CHMe2), 21.97 (CHMe2), 20.29 (DAB-
N CMe), 20.24 (DAB-N CMe) Anal. Calc. for C38H50N2O2Ni:
C, 72.95; H, 8.06; N, 4.48. Found: C, 72.09; H, 8.16; N, 4.63,15
UV-Vis: lmax (e)/nm 235 (22800), 265 (22100), 318 (10400), 704
(5000).
3
6.70 Hz, CHMe2), 3.18 (s, 6H, O-Me), 1.52 (d, 12H, JH-H
6.70 Hz, CHMe2), 0.99 (d, 12H, JH-H = 6.70 Hz, CHMe2), 13C
(C6D6) 163.71 (C(O)O), 159.48 (BIAN-N=C), 148.31 (BIAN-Ar-
i-C), 139.64 (Ar-C), 133.09 (Ar-C), 131.26 (Alkyne-C), 129.51
(Ar-C), 126.85 (Ar-C), 124.00 (Ar-C), 121.61 (Ar-C), 117.70
(Ar-C), 51.16 (O-Me), 29.44 (CHMe2), 23.97 (CHMe2), 23.52
(CHMe2), Anal. Calc. for C42H46N2O4Ni: C, 71.91; H, 6.61; N,
3.99. Found: C, 69.30; H, 6.37; N, 3.48,15 UV-Vis: lmax (e)/nm 298
(11100), 318 (10200), 499 (4100), 761 (6800).
3
=
=
=
Synthesis of DippDABNi(MeCO2CH CHCO2Me) (14),
X-ray data collection and reduction
=
DippDABNi(MeCO2CH CHPh) (15)
Crystals were coated in Paratone-N oil in the glovebox, mounted
on a MiTegen Micromount and placed under an N2 stream, thus
maintaining a dry, O2-free environment for each crystal. The data
for crystals were collected on a Bruker Apex II diffractometer.
The data were collected at 150( 2) K for all crystals (Table 1).
The frames were integrated with the Bruker SAINT software
package17 using a narrow-frame algorithm. Data were corrected
for absorption effects using the empirical multi-scan method
(SADABS).18
DippDAB was dissolved in THF (294 mg, 0.728 mmol; 2 mL)
giving a clear yellow solution that was added to a yellow slurry
of Ni(COD)2 and THF (200 mg, 0.728 mmol; 2 mL). A clear
=
colourless solution of MeCO2CH CHCO2Me in THF (105 mg,
0.728 mmol; 2 mL) was then added. The solution changed
immediately to blue-green. The reaction mixture was allowed to
stir overnight giving a deep green-blue solution. The volatiles
were removed in vacuo yielding a purple and blue solid mixture.
The crude product was washed with pentanes, and a dark blue
solution was decanted off of a blue solid. The product was washed
2 more times before the precipitate was dried. The solids were
dissolved in a minimal amount of diethyl ether and were placed in a
-35 ◦C freezer to precipitate the purified product. The precipitated
product was filtered on a fine porosity filter frit and the remaining
solution was cooled again for further precipitation. The product
Structure solution and refinement
Non-hydrogen atomic scattering factors were taken from the
literature tabulations.19 The heavy atom positions were determined
using direct methods employing the SHELXTL direct methods
routine.20 The remaining non-hydrogen atoms were located from
successive difference Fourier map calculations. The refinements
were carried out by using full-matrix least squares techniques on F,
minimizing the function w (Fo - Fc)2 where the weight w is defined
as 4Fo2/2s (Fo2) and Fo and Fc are the observed and calculated
structure factor amplitudes, respectively. In the final cycles of each
refinement, all non-hydrogen atoms were assigned anisotropic
temperature factors in the absence of disorder or insufficient data.
In the latter cases atoms were treated isotropically. C–H atom
positions were calculated and allowed to ride on the carbon to
1
was obtained in an 86% yield (380 mg, 0.625 mmol). H NMR
(C6D6) 7.28 (d, 2H, 3JH-H = 7.70 Hz, Ar-H), 7.18 (t, 2H, 3JH-H
=
7.70 Hz, Ar-H), 7.11 (d, 2H, 3JH-H = 7.70 Hz, Ar-H), 4.12 (sept,
3
2H, JH-H = 6.80 Hz, CHMe2), 3.33 (s, 2H, olefin-CH) 3.00 (s,
3
6H, O-Me), 2.55 (sept, 2H, JH-H = 6.80 Hz, CHMe2), 1.57 (d,
3
3
6H, JH-H = 6.80 Hz, CHMe2), 1.41 (d, 6H, JH-H = 6.80 Hz,
3
CHMe2), 1.05 (d, 6H, JH-H = 6.80 Hz, CHMe2), 0.93 (d, 6H,
JH-H = 6.80 Hz, CHMe2), 0.36 (s, 6H, N CMe) 13C (C6D6)
3
=
174.29 (C(O)O), 166.80 (DAB-N=C), 146.25 (Ar-C), 141.02 (Ar-
C), 137.95 (Ar-C), 126.46 (Ar-C), 124.16 (Ar-C), 123.61 (Ar-C),
50.33 (O-Me), 38.20 (olefin-CH), 29.50 (CHMe2), 28.68 (CHMe2),
24.64 (CHMe2), 24.55 (CHMe2), 23.30 (CHMe2), 22.49 (CHMe2),
19.66 (DAB-N=CMe) Anal. Calc. for C34H48N2O4Ni: C, 67.21;
H, 7.97; N, 4.61. Found: Too hygroscopic for EA, UV-Vis: lmax
(e)/nm 292 (9600), 370 (1600), 701 (2700) (15) green solid, 81%
˚
which they are bonded assuming a C–H bond length of 0.95 A. H-
atom temperature factors were fixed at 1.10 times the isotropic
temperature factor of the C-atom to which they are bonded.
The H-atom contributions were calculated, but not refined. The
locations of the largest peaks in the final difference Fourier map
calculation as well as the magnitude of the residual electron
densities in each case were of no chemical significance.
yield (368 mg, 0.421 mmol).1H NMR (C6D6) 7.51 (d, 1H, 3JH-H
6.90 Hz, DAB-p-Ar-H), 7.37(m, 4H, DAB-m-Ar-H), 7.15 (d, 1H,
=
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Table 1 Crystallographic data
1
3
4
5
6
7
9
11
15
Formula
C28H36N2Ni C36H52N2Ni C72H80N4Ni1
C44H52N2Ni C40H48N2Ni C42H50N2Ni C16H26N2NiO4 C37H62N2NiSi2 C38H50N2NiO2
Formula wt
Cryst. syst.
Space grp
458.30
Triclinic
¯
P1
571.51
1060.11
667.59
615.51
Triclinic
¯
P1
641.55
369.10
649.78
625.51
Monoclinic
P21/c
Monoclinic Orthorhombic Triclinic
P21/c
Monoclinic Orthorhombic Monoclinic
P21/n
¯
P1
Ccca
Pbca
P21/c
˚
a/A
8.2740(3)
17.3270(9)
16.524(3)
11.5009(6)
17.8623(9)
18.3510(9)
99.293(2)
92.622(2)
99.846(2)
3655.2(3)
4
12.2811(5)
12.4920(5)
13.1402(5)
74.338(2)
75.174(2)
64.761(2)
1732.68(12) 3614.2(7)
2
150
10.7742(11) 15.5058(6)
13.0819(14) 12.0233(5)
22.3895(5)
9.7738(2)
18.2857(4)
90.00
109.887 (1)
90.00
3762.84(14)
4
150
14.6319(4)
9.4273(3)
25.7606(8)
90.00
94.676(2)
90.00
3541.57(18)
4
150
˚
b/A
10.5006(3) 10.2591(5)
23.805(4)
˚
c/A
15.2269(5) 19.7575(10) 14.728(3)
25.749(3)
90.00
95.216(5)
90.00
19.8419(7)
90.00
90.00
90.00
3699.1(2)
8
a (◦)
b (◦)
g (◦)
72.275(2)
87.470(2)
81.677(2)
1246.87(7) 3189.1(3)
2
90.00
114.763(2)
90.00
90.00
90.00
90.00
5793.2(16)
4
3
˚
V/A
Z
4
4
Temp (◦K)
150
150
150
150
150
150
d(calc) g cm-1 1.223
1.190
0.0407
0.634
19397
5614
362
1.215
0.0357
0.382
11917
2558
1.213
0.0409
0.563
40566
11362
1.180
0.0262
0.589
30569
6075
388
1.179
0.0332
0.567
32153
6360
416
1.326
0.0272
1.068
63962
3255
1.147
0.0245
0.605
27639
6619
1.173
0.0446
0.581
96854
6241
R(int)
0.0218
0.795
18907
4380
m/cm-1
Total Data
Data Used
Variables
R (>3s)
Rw
280
179
863
216
385
399
0.0332
0.0944
1.067
0.0486
0.1302
1.042
0.0314
0.0910
1.077
0.0398
0.1008
1.040
0.0492
0.1339
1.092
0.0282
0.0733
1.039
0.0197
0.0543
1.040
0.0329
0.0923
1.037
0.0432
0.1010
1.058
GOF
isolated yield when ether was used as the solvent and the product
crystallized at -35 ◦C. The crystallographic characterization of (3)
is shown in Fig. 2.
Results and discussion
Diimine-Ni(COD) complexes
A common starting point for the preparation of Ni(0) complexes
is Ni(COD)2. A straightforward combination of a diimine ligand
such as MesDAD or DippDAD with this Ni precursor affords
the complexes MesDADNi(COD) (1), DippDADNi(COD) (2)
as brown solids in 95% and 79% isolated yields respectively
(Scheme 1). It is noteworthy that a related preparation of (1)14
and (2)16 have been previously reported. Nonetheless, the 1H
and 13C NMR data for the present products were consistent
with the formulation and in the case of (1) the formulation was
unambiguously confirmed by X-ray crystallography (Fig. 1). The
species DippDABNiCOD (3) was prepared via the addition of
DippDAB to a slurry of Ni(COD)2 followed by the subsequent
addition of a catalytic amount of 1-chloro-2-fluorobenzene in a
similar manner to that used to prepare the MesDAB equivalent
(Scheme 1).14 While a previous report16 describes only trace
quantities of the complex could be detected, it was obtained in 76%
Fig. 2 POV-ray drawing of (3), hydrogen atoms have been omitted for
◦
˚
clarity. Selected bond distances (A) and angles ( ): Ni–N(1) 1.949(3),
Ni–N(2) 1.937(2), Ni–C(7) 2.050(3), Ni–C(8) 2.084(3), Ni–C(11) 2.072(3),
Ni–C(12) 2.084(3), N(2)–Ni–N(1) 80.94(10).
Further changes to the ligands were also found to modify the
products. The reaction of the ligand MesBIAN with Ni(COD)2
did not lead to the complex analogous to (1)–(3). In this
case, the isolated purple solid (4) showed no NMR evidence
of the COD ligand while the 1H and 13C NMR spectra and
elemental analyses were consistent with the formulation of (4)
as (MesBIAN)2Ni (Scheme 1). Use of the proper stoichiometry
afforded the isolation of (4) in 72% yield. This formulation was
also confirmed crystallographically (Fig. 3). The Ni atom displays
a distorted square planar geometry about the nickel center. In
contrast, use of the DippBIAN ligand afforded brown crystals of
(5) in 77% isolated yield (Scheme 1). This species was formulated as
Fig. 1 POV-ray drawing of (1), hydrogen atoms have been omitted for
clarity. Selected bond distances (A) and angles ( ): Ni–N(2) 1.9374(17),
Ni–N(1) 1.9392(16), Ni–C(21) 2.059(2), Ni–C(28) 2.061(2), Ni–C(25)
2.064(2), Ni–C(24) 2.068(2), C(21)–C(28) 1.389(3), C(25)–C(24) 1.378(3),
N(2)–Ni–N(1) 82.44(7).
◦
˚
5790 | Dalton Trans., 2010, 39, 5786–5794
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Fig. 4 POV-ray drawing of (5), hydrogen atoms have been omitted for
◦
˚
clarity. Selected bond distances (A) and angles ( ): Ni–N(1) 1.956(2),
Ni–N(2) 1.972(2), Ni–C(15) 2.066(3), Ni–C(14) 2.069(3), Ni–C(10)
2.079(3), Ni–C(11) 2.088(3), N(1)–Ni–N(2) 83.44(9).
Scheme 1 Synthesis of Ni(COD)-diimine complexes.
The solid state geometries of the Ni centers in (1), (3) and
(5) are pseudo-tetrahedral with the N2Ni plane approximately
orthogonal to the plane comprised of the olefinic carbons of
the COD ligand. The Ni–N bond distances were found to be
˚
˚
˚
˚
1.9374(17) A, 1.9392(16) A in (1), 1.949(3) A and 1.937(2) A in
(3) and 1.956(2) and 1.972(2), in (5). The Ni–N bond distances
in (1) and (3) are essentially the same as those reported for (Mes-
14
˚
˚
DAB)Ni(COD) (Ni–N: 1.942(8) A, 1.938(7) A). The longer Ni–
N bond distances in (5) are consistent with the poorer donor ability
of the BIAN ligand. In the case of (4) the complex is pseudo-square
˚
planar with Ni–N distances of 1.9592(13) A, significantly shorter
that the Ni–N distances in the above Ni(COD) complexes and
slightly longer than the Ni–N bond distances in ((C6F5)DAD)2Ni
˚
˚
˚
(1.9173(18) A, 1.9165(17) A) and ((C6F5)BIAN)2Ni (1.9399(15) A,
1.9370(15) A)21 The Ni–C distances for the COD ligand were found
˚
˚
˚
˚
to range from 2.059(2) to 2.068(2) A in (1), 2.050(3) A to 2.084(3) A
˚
˚
in (3) and 2.066(3) A to 2.088(3) A in (5). These compare with
the range: 2.075(10) A to 2.077(11) A) previously reported for
(MesDAB)Ni(COD).
14
˚
˚
Diimine-Ni-alkyne complexes
Related Ni alkyne complexes are readily prepared by addition
of alkyne to solutions of the COD species generated in situ.
Fig. 3 POV-ray drawing of (4), hydrogen atoms have been omitted for clar-
˚
ity. Crystallographic symmetry at Ni is -1. Selected bond distances (A) and
≡
Thus, addition of PhC CPh to a solution of (2) gave a deep
angles (◦): Ni–N(1) 1.9592(13), N(1)–Ni–N(1)¢ 105.17(8), N(1)–Ni–N(1)¢¢
blue solid that was isolated in 79% yield. 1H and 13C NMR
data were consistent with the replacement of the COD lig-
and by alkyne and thus the formulation of this product as
83.23(8).
DippBIANNi(COD) (5) based on NMR data and was confirmed
crystallographically (Fig. 4). The formation of (4) and (5), from
similar reaction mixtures can be attributed in part to the differing
steric demands of the ligands. Presumably the steric demands of
the DippBIAN ligand preclude the formation of the L2Ni product
analogous to (4). Nonetheless, the driving force for the formation
of (4) is not well understood.
≡
DippDADNi(PhC CPh) (6). In a completely analogous fash-
≡
ion the blue-green species DippDABNi(PhC CPh) (7) and the
≡
brownish green DippBIANNi(PhC CPh) (8) were obtained in
80% and 72% isolated yields, respectively. These species (6)–(8)
gave rise to 13C resonances at 130.15, 129.81 and 130.12 ppm
respectively, attributable to the alkyne carbons. In addition, the
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≡
structures of (6) and (7) were further confirmed crystallographi-
cally (Fig. 5, 6).
(Me3SiC CSiMe3) (11) in 73% yield, though it is noteworthy that
this reaction was significantly slower than the previous reactions
requiring several days to reach completion. The NMR data for
(9)–(11) were as expected and the structures of (9) and (11) were
confirmed crystallographically (Fig. 7, 8).
Fig. 5 POV-ray drawing of (6), hydrogen atoms have been omitted for
clarity. Ni–C(3) 1.852(3), Ni–C(4) 1.858(3), Ni–N(1) 1.919(2), Ni–N(2)
1.920(2), C(3)–C(4) 1.286(4), C(3)–Ni–C(4) 40.56(13), N(1)–Ni–N(2)
82.33(10), C(35)–C(3)–Ni 143.0(2), C(29)–C(4)–Ni 144.7(2).
Fig. 7 POV-ray drawing of (9), hydrogen atoms have been omitted for
clarity. Ni–C(12) 1.8597(13), Ni–C(11) 1.8642(13), Ni–N(2) 1.9345(12),
Ni–N(1) 1.9415(11), C(11)–C(12) 1.2934(19), C(12)–Ni–C(11) 40.65(6),
N(2)–Ni–N(1) 83.16(5), C(13)–C(11)–Ni 148.54(10), C(14)–C(12)–Ni
150.41(10).
Fig. 6 POV-ray drawing of (7), hydrogen atoms have been omitted for clar-
ity. Ni–C(2) 1.8534(14), Ni–C(1) 1.8535(14), Ni–N(2) 1.9168(12), Ni–N(1)
1.9178(12), C(2)–C(1) 1.294(2), C(2)–Ni–C(1) 40.86(6), N(2)–Ni–N(1)
81.42(5), C(8)–C(2)–Ni 146.24(11), C(7)–C(1)–Ni 147.24(11).
Fig. 8 POV-ray drawing of (11), hydrogen atoms have been omitted for
clarity. Ni–C(33) 1.8807(19), Ni–C(29) 1.8963(19), Ni–N(1) 1.9227(15),
Ni–N(2) 1.9311(15), C(29)–C(33) 1.288(3), C(33)–Ni–C(29) 39.89(8),
N(1)–Ni–N(2) 81.22(6), Si(1)–C(29)–Ni 145.20(11), Si(2)–C(33)–Ni
147.95(12).
The analogous reactions employing tBuDAD ligand with either
≡
Ni(COD)2 alone or Ni(COD)2 and PhC CPh led only to the
bis-ligand Ni complex.22 However, combination of tBuDAD,
Employing
the
same
strategy
DippDABNi-
≡
≡
with Ni(COD)2 and MeCO2C CCO2Me in solution afforded
(MeCO2C CCO2Me) (12) was generated, although separation
of this product in pure form was plagued by contamination from
a by-product thought to arise from the cyclotrimerization of the
≡
the blue solid, tBuDADNi(MeCO2C CCO2Me) (9) in 78%
yield. In a similar fashion the purple-blue species DippDADNi-
≡
≡
(MeCO2C CCO2Me) (10) was obtained in 91% isolated
yield. The same strategy of mixing DippDAB, Ni(COD)2
acetylene. Similarly, reaction of (11) with MeCO2C CCO2Me
afforded (12), although it could be spectroscopically characterized,
≡
and Me3SiC CSiMe3 gave the blue product DippDABNi-
it could not be isolated in an analytically pure form. This
5792 | Dalton Trans., 2010, 39, 5786–5794
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latter strategy of acetylene exchange was used to prepare
≡
DippBIANNi(MeCO2C CCO2Me) (13) from (8) in 71% yield.
The structural studies of (6), (7), (9) and (11) displayed similar
geometries. In the (6), (7) and (9) the diimine and bound
alkyne are essentially coplanar with the angles between the
NiN2 and NiC2 planes of 0.3◦, 4.1◦ and 3.8◦. In contrast, the
corresponding interplane angle in (11) is 19.1◦. This observation
is presumably a result of the steric conflict between the SiMe3
and arene substituents on alkyne and diimine fragments. Binding
of the alkynes to Ni results in the “bend-back” of the alkynyl
substituents, resulting in Ni–C–C or Ni–C–Si angles ranging
from 143.0(2)◦ to 150.41(11)◦ consistent with partial reduction
≡
of the C C bond. This view is also consistent with the observed
˚
lengthening of the alkynyl C–C bonds to between 1.286(4) A
˚
and 1.2934(19) A. Ni–C bond distances are similar in (6) and
˚
˚
(7) ranging from 1.852(3) A to 1.858(3) A. In (9) where the
diimine is more sterically imposing on the alkyne binding site
and where the alkyne substituents are electron withdrawing, the
˚
˚
Ni–C are lengthened to 1.8597(13) A and 1.8642(13) A. Further
impact of steric demands are reflected in the Ni–C bond distances
˚
˚
in (11) (1.8807(19) A, 1.8963(19) A). The corresponding Ni–
N distances in (6), (7), (9) and (11) follow similar trends. The
˚
Ni–N distances in (6) and (7), are indistinguishable 1.918(2) A.
The Ni–N distances in (9) and (11) are slightly longer, averaging
˚
˚
1.9375(12) A and 1.9267(15) A, respectively. These Ni–C and
Ni–N distances are significantly longer than the Ni–N distances
≡
previously determined for (DippDAD)Ni(MeCO2C CCO2Me)
9
˚
˚
(Ni–N) 1.886(3) A, Ni–C 1.840(3) A).
Scheme 2 Synthesis of Ni-diimine alkyne and olefin complexes.
Diimine-Ni-olefin complexes
=
Addition of the olefin MeCO2CH CHCO2Me to in situ gen-
erated COD complexes, provided a strategy to DippDABNi-
=
(MeCO2CH CHCO2Me) (14). This approach afforded the blue
product (14) in 86% isolated yield. In a similar fashion, the green
=
species DippDABNi(MeCO2CH CHPh) (15) was isolated in 81%
yield. NMR data for these olefin complexes were consistent with
these formulations and in the case of (15) this was confirmed
by crystallography (Fig. 9). Similar to the alkyne complexes, the
geometry about Ni in (15) is planar, with Ni–N distances of
˚
˚
˚
1.9213(19) A and 1.9324(19) A. The Ni–C distances 1.945(2) A,
˚
and 1.958(2) A, are slightly longer than those in the alkyne
complexes below consistentwith the weaker donor abilityof alkene
versus alkyne.
Exchange reactions
The synthesis of the above Ni-dimine alkyne and olefin complexes
by in situ reactions with the COD complexes suggest that
ligand exchange reactions are facile. In this fashion, complete
conversion of (3) to (7), (11), (14) and (15) was observed upon
addition of the appropriate reagent (Scheme 2). In contrast,
Fig. 9 POV-ray drawing of (15), hydrogen atoms have been omitted
for clarity. Ni–N(1) 1.9213(19), Ni–N(2) 1.9324(19), Ni–C(3) 1.945(2),
Ni–C(4) 1.958(2), N(1)–Ni–N(2) 81.02(8), C(3)–Ni–C(4) 43.37(10).
≡
DippDABNi(MeCO2C CCO2Me) was generated, but could not
be isolated in a pure form. The alkyne complex (7) only reacts with
reactions conform to intuitive notions of alkyne and olefin ligand
donor abilities.
≡
MeCO2C CCO2Me, although, the product could not be isolated
cleanly. Nonetheless, (6) was converted to (10) and (11) reacts
The DippDAB complexes (3), (7), (11), (14) and (15) exhibit
similar although shifted absorptions in the visible spectrum
(Fig. 10) attributed to charge transfer transitions to the p* orbitals
of the diimine ligand. p–p* transitions are also observed in the UV
region. These assignments are in accord with recent experimental
≡
with PhC CPh to give (7). The olefin complex (15) afforded (7),
(11) and (14) via ligand exchange (Scheme 3). In contrast to (15),
≡
(14) reacts cleanly with PhC CPh to give (7). These exchange
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the development of applications of such species in new reactivity
and catalysis. These efforts are underway and will be reported in
due course.
Acknowledgements
Financial support from NSERC of Canada, the Ontario Centres
of Excellence and the LANXESS Corporation is gratefully
acknowledged. MJS is grateful for the award of an NSERC
graduate scholarship. DWS is grateful for the award of a Canada
Research Chair and a Killam Research Fellowship.
Notes and references
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Scheme 3 Exchange reactions of (DippDAB)Ni complexes.
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Fig. 10 Visible absorption spectra of (DippDAB)Ni complexes.
and DFT studies.14 The olefin complexes (14) and (15) exhibit
higher wavelength absorptions than the acetylene complexes, while
the COD complex (3) is considerable red-shifted exhibiting a lmax
at 520 nm.
16 H. Dieck, M. Svoboda and T. Greiser, Z. Naturforsch., B: Anorg. Chem.
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Conclusions
In conclusion, a series of diimine-Ni complexes of COD, alkynes
and olefins have been prepared and shown to undergo ligand
exchange reactions. The chemistry illustrates that COD and the
20 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008,
A64, 112–122.
21 M. M. Khusniyarov, K. Harms, O. Burghaus and J. Sundermeyer,
Eur. J. Inorg. Chem., 2006, 2985–2996.
=
alkene PhCH CHCO2Me, are readily displaced by more p-acidic
22 M. Svoboda, H. t. Dieck, C. Kru¨ger and Y.-H. Tsay, Z. Naturforsch.,
B: Anorg. Chem. Org. Chem., 1981, 36b, 814–822.
alkenes and alkynes. The ready access to these species now permits
5794 | Dalton Trans., 2010, 39, 5786–5794
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The Royal Society of Chemistry 2010
©