Substitution matters: Isolating phosphorus diiminopyridine complexes

Article abstract of DOI:10.1039/c1dt11111f

The direct reactions of PI₃ with -H or -C₆H ₅ substituted diiminopyridine ligands yield the N,N′, N′′-chelated P(i) cations. The analogous chemistry with the ubiquitous -CH₃ substituted derivative produces a com

Full text of DOI:10.1039/c1dt11111f

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2011, 40, 11976
www.rsc.org/dalton
PAPER
Substitution matters: isolating phosphorus diiminopyridine complexes†
Caleb D. Martin and Paul J. Ragogna*
Received 13th June 2011, Accepted 31st August 2011
DOI: 10.1039/c1dt11111f
The direct reactions of PI3 with –H or –C6H5 substituted diiminopyridine ligands yield the N,N¢,N¢¢-
chelated P(I) cations. The analogous chemistry with the ubiquitous –CH3 substituted derivative
produces a complex mixture of products underscoring the importance of the substitution on the
-
a-carbon atom. The I3 counteranion of the compounds could be easily exchanged with the more
2-
robust B12Cl12 dianion. Reactions of PCl3 and PBr3 with –CH3 and –C6H5 substituted ligands led to
indiscernible mixtures or no reaction. However, heating PBr3 with the –H derivative in the presence of a
halide trap produced the corresponding phosphorus(I) cation as the bromide salt. These species
represent the first phosphorus diiminopyridine complexes reported.
Introduction
Recent years have shown a surge of interest in probing the
reactivity of a-diimine ligands with the main group elements. The
1,4-diaza-1,3-butadiene (RDAB) system has been widely explored,
while studies with the diiminopyridine ligand (RDIMPY, Fig. 1,
Fig. 1 The RDIMPY ligands (1–3), known main group RDIMPY
complexes (centre) and the enamine tautomer of 1 (1¢).
1: R = CH3; 2: R = H; 3: R = C6H5) have been mostly restricted
to the heavy group 13–15 elements (n ≥ 3), which preferentially
form complexes with the p-block centres in low oxidation states.1–8
For example, the redox reaction of AsI3 with 1 yields an As(I)
species, in contrast to the analogous transformation with RDAB
which produces an As(III) cation.4 For RDAB, RDIMPY and
also the related b-diketiminate ligands there is evidence that the
substitution on both the a-carbon and imine nitrogen atoms can
be highly influential in the outcome of the reaction. Hydrogen
atoms on the carbon are often found to be acidic and prone
to halogenation,9–11 whereas the methyl substituted derivative
can react as the enamine tautomer (e.g. for RDIMPY 1¢).12–16
Despite the vast amounts of P–N chemistry in the literature,
phosphorus surprisingly lacks an RDIMPY complex. Although
not observed with arsenic, we surmised that the related enamine
chemistry could proceed with phosphorus. This reactivity is unable
to occur with the less common –H and –C6H5 ligands (2 and
3) and should provide a P(I) species via redox reaction.‡ In
this context, we exploit the reactions of RDIMPY ligands with
varying substitution on the a-carbon (1–3) with the phosphorus
trihalides (PCl3, PBr3 and PI3) with the aim of synthesizing the
first phosphorus diiminopyridine complex.
Results and discussion
Synthesis
A solution of 1 in CH2Cl2 was added to PI3 in the same solvent and
stirred for 20 min at room temperature, resulting in a colour change
1
from yellow to red. A 31P{ H} NMR spectrum of an aliquot of
the reaction mixture revealed a complex mixture of phosphorus
containing products (Fig. 2). The analogous transformations were
performed with 2 and 3, also generating red solutions (Scheme 1).
Department of Chemistry, The University of Western Ontario, 1151 Rich-
mond St., London, ON, Canada. E-mail: pragogna@uwo.ca; Fax: +1-519-
661-3022; Tel: +1-519-661-2166
† Electronic supplementary information (ESI) available. CCDC reference
numbers 817021–817024. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt11111f
‡ SciFinder search results (Feb. 21, 2011) indicate that 1 is the most widely
used: 1: 331 references; 2: 30 references; 3: 14 references (all examples have
2,6-diisopropylphenyl substitution at N).
1
Fig. 2 Stacked in situ 31P{ H} NMR spectra of reactions of PI3 with the
RDIMPY ligands. From top to bottom: 1, 2 and 3.
11976 | Dalton Trans., 2011, 40, 11976–11980
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
Scheme 1 Synthetic route to the P(I) DIMPY complexes 2P[I3], 3P[I3]
and 2P[B12Cl12].
Fig. 4 Solid-state structure of the cation in 3P[I3]. Thermal ellipsoids
are drawn to the 50% probability level. Anion, hydrogen atoms and
˚
isopropyl groups are removed for clarity. Salient bond lengths (A); other
corresponding asymmetric unit follows in brackets: P(1)–N(1) 1.934(6)
[1.936(6)], P(1)–N(2) 1.722(8) [1.714(9)], C(1)–N(1) 1.311(9) [1.333(10)].
1
The in situ 31P{ H} NMR spectra obtained for the latter
two reactions displayed a dominant resonance, shifted to high
field relative to PI3 (2: d= 169 ppm; 3: d= 154 ppm cf. PI3 d=
174 ppm). Red solids were precipitated from the reaction mixture
by adding n-pentane, washed with Et2O and dried in vacuo. The
corresponding 1H NMR spectra of the redissolved solids indicated
the presence of a single DIMPY containing product. The spectrum
obtained from the reaction with 2 had the resonance for the
protons on the a-carbon atom split into a doublet, with coupling
is speculated that this is due to uncontrollable reactivity with the
enamine tautomer (1¢).§
Complex 2P[I3] was reacted with 1.5 stoichiometric equivalents
of Na2[B12Cl2] at room temperature for 12 h to yield the anion
exchange product with the more robust B12Cl12 dianion. Cen-
trifuging the reaction mixture, precipitating the orange product
with n-pentane from the supernatant and drying in vacuo gave the
3
1
salt in 65% yield. The 31P{ H} and 1H NMR spectra were similar
consistent with typical JH-P values and was shifted downfield
1
to 2P[I3] and a single peak in the 11B{ H} NMR spectrum (d =
suggesting the successful incorporation of phosphorus into the
ligand framework (Dd= 0.90 ppm, 3JH-P = 5.6 Hz).17,18 Diagnostic
features in both spectra were downfield shifts of the protons at the
3 and 5 positions on the pyridine rings (2: Dd = 0.71 ppm 3: Dd =
1.12 ppm)17,19 consistent with the coordination of the ligand to a
cationic centre.
-12.7 ppm) confirmed the presence of B12Cl122-. X-ray diffraction
experiments on orange crystals grown by vapour diffusion of Et2O
into CH2Cl2 confirmed the identity of 2P[B12Cl12] as the cationic
2-
phosphorus HDIMPY complex in a 2 : 1 ratio with a B12Cl12
counteranion (Fig. 5).
X-ray diffraction analyses of single crystals of both compounds
grown by vapour diffusion of n-pentane into CHCl3 confirmed
the identity of the redox products 2P[I3] and 3P[I3] as P(I) cations
sequesteredintheRDIMPYligand withI3- counteranions isolated
in 81% and 77% yields, respectively (Fig. 3 and 4). Given the
plethora of unidentifiable products in the 31P NMR spectrum for
the attempted synthesis of 1P[I3] the reaction was not pursued. It
Fig. 5 Solid-state structure of the cation in 2P[B12Cl12]. Thermal ellipsoids
are drawn to the 50% probability level. Anions, solvates, hydrogen atoms
˚
and isopropyl groups are removed for clarity. Salient bond lengths (A)
2P[B12Cl12]: P(1)–N(1) 1.808(2), P(1)–N(2) 1.730(2), P(1)–N(3) 2.177(2),
C(1)–N(1) 1.320(3), N(3)–C(7) 1.284(3).
Examining the analogous chemistry of PCl3 with 2 or 3 in the
presence of the halide trap cyclohexene20,21 to aid the redox reaction
in targeting the P(I) complex did not result in any reaction based on
Fig. 3 Solid-state structure of the cation in 2P[I3]·CHCl3. Thermal
ellipsoids are drawn to the 50% probability level. Anions, sol-
vates, hydrogen atoms and isopropyl groups are removed for clar-
˚
ity. Salient bond lengths (A) 2P[I3]·CHCl3: P(1)–N(1) 1.877(7),
P(1)–N(2) 1.722(6), P(1)–N(3) 1.975(8), N(1)–C(1) 1.303(11), N(3)–C(7)
1.316(11).
§ Although this chemistry could be harnessed for other main group
examples in previous studies,12–14 this was not the case for this system.
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 11976–11980 | 11977
©

View Article Online
Table 1 X-ray details for 2P[I3]·CHCl3, 2P[B12Cl12], 2P[Br]·CH2Cl2 and 3P[I3]
Compound
2P[I3]·CHCl3
2P[B12Cl12]
2P[Br]·CH2Cl2
3P[I3]
Empirical formula
FW/g mol-1
C32H40Cl3I3N3P
984.69
Monoclinic
P21
11.690(2)
12.287(2)
13.601(2)
90
93.493(4)
90
1950.0(5)
2
1.677
0.71073
150(2)
0.0500
0.1399
1.056
C31H39B6Cl6N3P
762.18
Monoclinic
C2/c
18.3065(6)
17.4020(6)
25.0012(9)
90
92.7560(10)
90
7955.4(5)
8
1.273
0.71073
150(2)
0.0416
C32H39BrCl2N3P
647.44
Monoclinic
P21/c
17.049(3)
13.120(3)
17.259(4)
90
119.39(3)
90
3363.6(12)
4
1.278
0.71073
150(2)
0.0606
C43H47B2I3N3P
1017.51
Monoclinic
P2/c
24.522(2)
8.6258(8)
21.669(2)
90
113.291(2)
90
4210.0(7)
4
1.605
0.71073
150(2)
0.0707
0.1703
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
Dc (mg m-3)
˚
radiation, l/A
T/K
R1[I > 2sI]a
wR2(F2)a
0.0936
1.051
0.2018
1.070
GOF (S)a
1.149
ꢀ
ꢀ
a R1(F[I > 2(I)]) = ꢀ|Fo| - |Fc |ꢀ/ |Fo|; wR2(F2 [all data]) = [w(Fo - Fc2)2]1/2; S(all data) = [w(Fo - Fc2)2/(n - p)]1/2 (n = no. of data; p = no. of
2
2
parameters varied; w = 1/[s (Fo2) + (aP)2 + bP] where P = (Fo + 2Fc2)/3 and a and b are constants suggested by the refinement program.
2
2
1
in situ 31P{ H} NMR spectroscopy, even at reflux temperatures in
toluene. A new phosphorus signal (d = 166 ppm) slowly appeared
in the reaction of phosphorus tribromide with 2 and 6 stoichiomet-
ric equivalents of cyclohexene at room temperature. Conversion
to one peak was observed upon reaction at 40 ◦C for 3 days
(Scheme 2). Heating the sample above 40 ◦C led to decomposition.
The compound could be isolated as orange crystals in 28% yield
which were subjected to X-ray diffraction analysis revealing a P(I)
cation within the HDIMPY framework and a bromide counteran-
ion (2P[Br]). In all cases, the attempted transformation with PBr3,
cyclohexene and 3 resulted in no reaction, even when refluxing
in toluene. Reactions of PBr3 or PCl3 with 1 and cyclohexene
1
produced mixtures that by 31P{ H} NMR spectroscopic analysis
showed no indication of clean formation of a P(I) salt. X-ray
details for 2P[I3]·CHCl3, 2P[B12Cl12], 2P[Br]·CH2Cl2 and 3P[I3]
Fig. 6 Solid-state structures of the cation in 2P[Br]·CH2Cl2. Thermal
ellipsoids are drawn to the 50% probability level. Anions, solvates,
hydrogen atoms and isopropyl groups are removed for clarity. Salient bond
can be found in Table 1.
˚
lengths (A) 2P[Br]: P(1)–N(1) 1.755(3), P(1)–N(2) 1.722(3), P(1)–N(3)
2.318(3), C(1)–N(1) 1.327(5), N(3)19–C(7) 1.285(4).
phosphorus diiminopyridine compound bearing hydrogen atoms
on the a-carbon atom and nitrogen atoms indicate that the
asymmetrical structure is the minimum on the potential energy
surface.23 These observations are likely a phenomenon observed
in the solid-state and gas-phase, as in solution NMR spectroscopic
studies only one peak is observed for the diagnostic protons on
the a-carbon, indicating an equilibrium position. In Schemes 1
and 2 the dative bonding models are drawn but in view of the
metrical parameters, the charge is likely delocalized throughout
the dication, resulting in a hybrid structure best represented as the
pyridinium/iminium salt.
Scheme 2 Synthetic route to 2P[Br].
X-Ray crystallography
The solid-state structures of 2P[I3], 2P[B12Cl12], 2P[Br] and 3P[I3]
revealed a T-shaped phosphorus(I) cation consistent with two
lone pairs and three bound nitrogen centres (AX3E2 electron
pair configuration; Fig. 3–6). The pyridine nitrogen occupies an
equatorial site while the two imine nitrogen atoms reside in axial
positions. For all four compounds, the anions are distant from
the cationic P(I) centres (greater than the sum of the van der
Conclusions
˚
˚
Waals radii; Rv.d.W. P–I = 4.05 A, Rv.d.W. P–Br = 3.85 A, Rv.d.W. P–
22
˚
Cl = 3.75 A). The Npyr–P bond in 3P[I3] lies on a site of
In summary, 2P[I3], 2P[B12Cl12], 2P[Br] and 3P[I3] represent
examples of uncommon P(I) salts.24 The RDIMPY complexes
differ from the analogous 1,4-diaza-1,3-butadiene (RDAB) species
symmetry while in all the complexes of 2, the two imine groups
are asymmetrical. Previously reported computational data on the
11978 | Dalton Trans., 2011, 40, 11976–11980
This journal is
The Royal Society of Chemistry 2011
©

View Article Online
as they do not undergo a charge transfer process with the ligand
to produce P(III) heterocycles.25,26 In addition these compounds
represent the first isolated phosphorus RDIMPY complexes, only
the second example for a non-metal, which was made possible by
utilizing the less common hydrogen and phenyl substituted ligands
rather than the methyl derivative.
and the solids washed with Et2O (3 ¥ 5 mL) and dried in vacuo.
Yield: 0.195 g, 77%; mp(decomp) 323–324 ◦C. 1H NMR (CDCl3,
d (ppm)) 8.65 (d, 2H, 3JH-H = 8.0 Hz), 8.21 (t, 1H, 3JH-H = 8.0 Hz),
3
7.53–7.47 (mult, 10H), 7.17 (t, 2H, JH-H = 7.6 Hz), 2.55 (septet,
3
3
4H, JH-H = 6.8), 1.10 (d, 12H, JH-H = 6.4 Hz), 0.89 (d, 12H,
3JH-H = 6.8 Hz); 13C{ H} NMR (CDCl3, d (ppm)) 155.6, 143.2,
1
2
136.9 (d, JC-P = 9 Hz), 133.1, 131.4, 131.3, 131.0, 129.4, 129.3,
128.2, 124.1 28.9, 26.9, 23.1; 31P{ H} NMR (CDCl3, d (ppm))
1
Experimental section
154; FT-IR (cm-1 (ranked intensity)) 700(5), 732(7), 766(9), 804(4),
1023(11), 1056(6), 1226(12), 1253(15), 1303(13), 1321(2), 1362(10),
1384(8), 1444(14), 1460(3), 2964(1); FT-Raman (cm-1 (ranked
intensity)) 117(1), 244(14), 402(13), 496(12), 1000(4), 1043(11),
1156(5), 1248(9), 1350(15), 1482(7), 1518(3), 1598(2), 2930(8),
2969(10), 3052(6); ESI-MS: m/z 636 ([3P]+). Elemental analysis:
Calc. for C43H47N3PI3 C 50.73, H 4.66, N 4.13%; Found C 50.70,
H 4.75, N, 4.06%.
General procedures
All manipulations were performed under inert atmosphere in a
nitrogen filled MBraun Labmaster DP glove box or using standard
Schlenk techniques. All solvents were dried using an MBraun
Controlled Atmospheres Solvent Purification System and stored
˚
over 4 A molecular sieves in the glove box. Cyclohexene, PCl3
and PBr3 were purchased from Alfa Aesar and distilled prior to
use. Phosphorus(III) iodide was purchased from Aldrich and used
as received. The diiminopyridine ligands and Na2[B12Cl12] were
prepared according to literature procedures and dried in vacuo
overnight.5,17,19,27 Solvents for 1H NMR spectroscopy (CDCl3 and
CD2Cl2) were dried by stirring for 3 days over CaH2, distilled
2P[Br]: In an NMR tube, neat PBr3 (0.21 mL, 0.221 mmol)
was added to a CDCl3 (1 mL) solution of 2 (0.100 g, 0.221
mmol) and cyclohexene (0.134 mL, 1.33 mmol). The NMR
tube was agitated and placed in an oil bath at 40 ◦C for 3
d resulting in a deep red solution. To the mixture, CH2Cl2 (1
mL) and n-pentane (3 mL) were added sequentially and the
solution stored at -30 ◦C for an hour to produce orange crystals
of 2P[Br]. Yield: 0.035 g, 28%; mp(decomp) 141–143 ◦C. 1H
˚
prior to use and stored in the glove box over 4 A molecular
sieves. All NMR spectra were recorded on a Varian INOVA
400 MHz spectrometer (1H = 399.76 MHz, 13C = 100.52 MHz,
11B = 376.15 MHz) in CD3CN. X-Ray diffraction data were
collected on a Nonius Kappa-CCD area detector or Bruker Apex
3
NMR (CDCl3, d (ppm)) 9.87 (d, 2H, JH-P = 5.2 Hz), 9.57 (d,
3
3
2H, JH-H = 7.6 Hz), 8.27 (t, 1H, JH-H = 7.6 Hz), 7.41 (t, 2H,
3JH-H = 7.6 Hz), 7.28 (d, 4H, JH-H = 7.6 Hz), 2.36 (septet, 4H,
3
˚
II detector using Mo-Ka radiation (l = 0.71073 A). Crystals
3JH-H = 6.8), 1.13 (br, 24H); 13C{ H} NMR (CDCl3, d (ppm))
1
were selected under oil, mounted on MiTeGen micromounts then
immediately placed in a cold stream of N2. Structures were solved
by direct methods and refined using full matrix, least squares on
F2. Elemental analyses were performed by Laboratoire d’analyse
e´le´mentaire at Universite´ de Montre´al.
2
147.8, 142.2, 136.9 (d, JC-P = 10 Hz), 135.5, 132.1, 129.4, 127.7,
123.8, 28.8, 24.6; 31P{ H} NMR (CDCl3, d (ppm)) 166; FT-IR
1
(cm-1 (ranked intensity)) 471(15), 639(12), 723(2), 758(10), 804(6),
922(4), 1072(7), 1100(14), 1177(8), 1324(5), 1364(9), 1459(3),
1587(11), 2189(13), 2962(1). ESI-MS: m/z 484 ([2P]+).
2P[B12Cl12]: A slurry of Na2[B12Cl12] (0.213 g, 0.349 mmol)
in CH2Cl2 (5 mL) was added to a solution of 2P[I3] (0.200
g, 0.231 mmol) in CH2Cl2 (5 mL) and stirred for 12 h. The
resulting slurry was centrifuged and n-pentane (8 mL) was added
Synthesis
2P[I3]: A solution of 2 (0.150 g, 0.331 mmol) in CH2Cl2 (4 mL)
was added to a solution of PI3 (0.136 g, 0.331 mmol) in the same
solvent (4 mL) in the dark. The solution was stirred for 20 min
resulting in a deep red solution. Normal pentane (8 mL) was
added to precipitate a red powder. The supernatant was discarded
and the solids washed with Et2O (3 ¥ 5 mL) and dried in vacuo.
Yield: 0.231 g, 81%; mp(decomp) 254–256 ◦C. 1H NMR (CDCl3,
◦
to the supernatant and the solution stored at -30 C over night.
The supernatant was decanted and the resulting orange solids
dried in vacuo. Yield: 0.111 g, 65%; mp(decomp) 196–197 ◦C.
3
1H NMR (CD2Cl2, d (ppm)) 9.29 (d, 2H, JH-P = 5.2 Hz), 9.40
3
3
(d, 2H, JH-H = 8.0 Hz), 8.30 (t, 1H, JH-H = 8.0 Hz), 7.45 (t,
3
3
3
3
d (ppm)) 9.34 (d, 2H, JH-P = 5.6 Hz), 9.01 (d, 2H, JH-H = 8.0
Hz), 8.30 (t, 1H, JH-H = 8.0 Hz), 7.43 (t, 2H, JH-H = 7.6 Hz),
2H, JH-H = 8.0 Hz), 7.33 (d, 4H, JH-H = 8.4 Hz), 2.41 (septet,
3 1
4H, JH-H = 6.8), 1.13 (overlapping doublets, 24H); 11B{ H}
3
3
3
3
1
7.30 (d, 4H, JH-H = 7.6 Hz), 2.49 (septet, 4H, JH-H = 6.8), 1.15
(CD2Cl2, d (ppm)) -12.7; 13C{ H} NMR (CD2Cl2, d (ppm))
1
2
(overlapping doublets, 24H); 13C{ H} NMR (CDCl3, d (ppm))
149.6, 145.7, 140.1 (d, JC-P = 10 Hz), 138.7, 134.0, 132.9, 131.5,
2
1
146.3, 142.4, 136.9 (d, JC-P = 10 Hz), 135.6, 131.1, 129.6, 128.2,
127.2, 32.1, 27.8; 31P{ H} (CD2Cl2, d (ppm)) 169 ppm; FT-IR
124.0, 28.9, 24.9; 31P{ H} NMR (CDCl3, d (ppm)) 169; FT-IR
(cm-1 (ranked intensity)); 534(2), 714(10), 757(7), 802(6), 1031(1),
1168(9), 1256(13), 1324(5), 1364(8), 1460(4), 1499(14), 1604(11),
2868(15), 2962(3), 3067(13); FT-Raman (cm-1 (ranked intensity))
112(3), 141(2), 163(1), 299(4), 472(8), 1044(13), 1177(14), 1244(7),
1323(15), 1442(10), 1636(12), 1505(6), 1589(5), 2932(9), 2965(11).
*Peak at 163(1) corresponds to I2 impurity. ESI-MS: m/z 484
([2P]+), 1038(2P[B12Cl12] - H).
1
(cm-1 (ranked intensity)) 469(8), 736(5), 756(6), 778(12), 798(1),
1071(3), 1055(11), 1102(14), 1167(10), 1260(7), 1351(9), 1381(13),
1455(4), 2957(2), 2962(15); FT-Raman (cm-1 (ranked intensity))
87(10), 118(1), 479(13), 586(14), 710(8), 888(12), 1044(6), 1247(5),
1355(15), 1387(11), 1590(4), 2865(7), 2933(3), 2962(2), 3068(9);
ESI-MS: m/z 484 ([2P]+).
3P[I3]: A solution of 3 (0.150 g, 0.248 mmol) in CH2Cl2 (4 mL)
was added to a solution of PI3 (0.102 g, 0.248 mmol) in the same
solvent (4 mL) in the dark. The solution was stirred for 20 min
resulting in a deep red solution. Normal pentane (8 mL) was
added to precipitate a red powder. The supernatant was discarded
Acknowledgements
The authors are grateful for generous funding from the Nat-
ural Sciences and Engineering Council of Canada (NSERC),
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 11976–11980 | 11979
©

View Article Online
the Ontario Ministry of Research and Innovation, the Canada
Foundation for Innovation, The University of Western Ontario
and the “A Special International Research Experience” (ASPIRE)
travel award program. Professor Christopher A. Reed and his
students are thanked for their time and expertise in assisting in the
11 A. Hinchliffe, F. S. Mair, E. J. L. McInnes, R. G. Pritchard and J. E.
Warren, Dalton Trans., 2008, 222–233.
12 J. L. Dutton, C. D. Martin, M. J. Sgro, N. D. Jones and P. J. Ragogna,
Inorg. Chem., 2009, 48, 3239–3247.
13 G. Reeske and A. H. Cowley, Chem. Commun., 2006, 4856–4858.
14 L. Zheng, G. Reeske, J. A. Moore and A. H. Cowley, Chem. Commun.,
2006, 5060–5061.
2-
preparation of B12Cl12 salts.
15 A. F. Gushwa, J. G. Karlin, R. A. Fleischer and A. F. Richards, J.
Organomet. Chem., 2006, 691, 5069–5073.
16 A. F. Gushwa and A. F. Richards, Eur. J. Inorg. Chem., 2008, 728–736.
17 G. J. P. Britovsek, M. Bruce, V. C. Gibson, B. S. Kimberley, P. J. Maddox,
S. Mastroianni, S. J. McTavish, C. Redshaw, G. A. Solan, S. Strmberg,
A. J. P. White and D. J. Williams, J. Am. Chem. Soc., 1999, 121, 8728–
8740.
18 X. Wang, J. Huang, S. Xiang, Y. Liu, J. Zhang, A. Eichhofer, D. Fenske,
S. Bai and C.-Y. Su, Chem. Commun., 2011, 47, 3849.
19 N. Kleigrewe, W. Steffen, T. Blomker, G. Kehr, R. Frolich, B. Wibbeling,
G. Erker, J.-C. Wasilke, G. Wu and G. C. Bazan, J. Am. Chem. Soc.,
2005, 127, 13955–13968.
Notes and references
1 T. Jurca, J. Lummiss, T. J. Burchell, S. I. Gorelsky and D. Richeson, J.
Am. Chem. Soc., 2009, 131, 4608–4609.
2 C. D. Martin, C. M. Le and P. J. Ragogna, J. Am. Chem. Soc., 2009,
131, 15126–15127.
3 J. Scott, S. Gambarotta, I. Korobkov, Q. Knijnenburg, B. de Bruin
and P. H. M. Budzelaar, J. Am. Chem. Soc., 2005, 127, 17204–
17206.
4 G. Reeske and A. H. Cowley, Chem. Commun., 2006, 1784–1786.
5 T. Jurca, K. Dawson, I. Mallov, T. Burchell, G. P. A. Yap and D.
Richeson, Dalton Trans., 2010, 39, 1266–1272.
6 K. Nomiya, K. Sekino, M. Ishikawa, A. Honda, M. Yokoyama, N. C.
Kasuga, H. Yokoyama, S. Nakano and K. Onodera, J. Inorg. Biochem.,
2004, 98, 601–615.
7 J. S. Casas, E. E. Castellano, J. Ellena, M. S. Garca-Tasende, A. Sanchez,
J. Sordo, E. M. Vazquez-Lopez and M. J. Vidarte, Z. Anorg. Allg.
Chem., 2003, 629, 261–267.
8 R. Pedrido, M. J. Romero, M. R. Bermejo, A. M. Gonzalez-Noya,
M. Maneiro, M. J. Rodriguez and G. Zaragoza, Dalton Trans., 2006,
5304–5314.
20 E. L. Norton, K. L. S. Szekely, J. W. Dube, P. G. Bomben and C. L. B.
Macdonald, Inorg. Chem., 2008, 47, 1196–1203.
21 J. L. Dutton, A. Sutrisno, R. W. Schurko and P. J. Ragogna, Dalton
Trans., 2008, 3470–3477.
22 L. Pauling, The Nature of the Chemical Bond, Cornell University Press,
Ithaca, 1960.
23 B. D. Ellis and C. L. B. Macdonald, Inorg. Chim. Acta, 2007, 360,
329–344.
24 B. D. Ellis and C. L. B. Macdonald, Coord. Chem. Rev., 2007, 251,
936–973.
25 G. Reeske, C. R. Hoberg, N. J. Hill and A. H. Cowley, J. Am. Chem.
Soc., 2006, 128, 2800–2801.
26 G. Reeske and A. H. Cowley, Inorg. Chem., 2007, 46, 1426–1430.
27 V. Geis, K. Guttsche, C. Knapp, H. Scherer and R. Uzun, Dalton Trans.,
2009, 2687–2694.
9 C. D. Martin and P. J. Ragogna, Inorg. Chem., 2010, 49, 4324–
4330.
10 F. S. Mair, R. Manning, R. G. Pritchard and J. E. Warren, Chem.
Commun., 2001, 1136–1137.
11980 | Dalton Trans., 2011, 40, 11976–11980
This journal is
The Royal Society of Chemistry 2011
©