Low-Coordinate Monomeric Zinc Hydride Complexes with Encapsulating Dipyrromethene Ligands and Reactivity with B(C6F5)3

Article abstract of DOI:10.1002/zaac.201900179

The dipyrromethene (DPM) ligand is the key to isolation of monomeric Zn hydride complexes with tricoordinate zinc centers. A range of ^RDPM ligands with various substituents in the pole position (1,9-positions) were prepared: R = tBu, adamantyl

Full text of DOI:10.1002/zaac.201900179

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201900179
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Low-Coordinate Monomeric Zinc Hydride Complexes with
Encapsulating Dipyrromethene Ligands and Reactivity with B(C6F5)3
Gerd Ballmann,[a] Johannes Martin,[a] Jens Langer,[a] Christian Färber,[a] and Sjoerd Harder*[a]
Dedicated to Professor Manfred Scheer on the Occasion of his 65th Birthday
Abstract. The dipyrromethene (DPM) ligand is the key to isolation of ZnH. For ligands with the larger Mes* and Anth substituents, (RDPM)
monomeric Zn hydride complexes with tricoordinate zinc centers. A ZnEt was converted to (RDPM)ZnOSiPh3, which after reaction with
range of RDPM ligands with various substituents in the pole position PhSiH3 gave the hydrides. While Zn hydride complexes with R = tBu
(1,9-positions) were prepared: R = tBu, adamantyl (Ad), mesityl or Ad are dimeric, all complexes with aryl-substituents are monomeric.
(Mes), 2,6-diisopropylphenyl (DIPP), 2,4,6-triphenylphenyl (Mes*), or The aryl groups span a cavity around the metal, blocking dimerization
1
9-anthracenyl (Anth). Reaction of the ligands with Et2Zn gave a series and causing a high-field shift of the H NMR signals due to the ASIS
of (RDPM)ZnEt complexes, which were converted with I2 to the corre-
effect. Attempted abstraction of the hydride with B(C6F5)3 led to
sponding (RDPM)ZnI compounds. The latter reacted by salt metathesis cleavage of the B-C6F5 bond.
with KN(iPr)HBH3 to the series of Zn hydride complexes (RDPM)
vented by addition of bulky, strongly coordinating, NHC li-
gands which led to structural characterization of a sub unit of
(ZnH2)ϱ (III).[8]
Introduction
In contrast to the high reactivity and rich reduction chemis-
try of hydrides from the s- and p-block, the development of
ZnH2 chemistry always lagged behind. Although already pre-
pared in 1951 by Schlesinger,[1] its poor solubility in organic
solvents and especially its very low thermal stability precluded
major applications. A convenient route to ZnH2 has been re-
ported by van der Kerk,[2] who converted Et2Zn with LiAlH4
to obtain a white powder that at room temperature already
turned grey on account of decomposition into its elements. The
latter problem is clearly related to the more noble character of
Zn which, combined with the low stability of hydride (H2 +
2e– i 2 H– E0 = –2.23 V),[3] is easily reduced. The recognition
that heteroleptic RZnH complexes are much more stable initi-
ated great interest in this compound class.[4,5] Especially bulky
R groups were found to preserve Zn hydride complexes by
blocking redox decomposition (e.g. I).[6] Also use of multiden-
tate ligands led to isolation of a large variety of stable Zn
hydride complexes among which the scorpionate complex
II.[7] Although the solid-state structure of ZnH2 is currently
still unknown, Okuda and co-workers recently demonstrated
that decomposition of this labile metal hydride can be pre-
We and others contributed to Zn hydride chemistry by intro-
ducing its first β-diketiminate complexes which especially for
bulky ligands led to unusual low-coordinate Zn hydride com-
plexes (IV).[9] In solution, however, even complex IV shows
strong tendency to aggregate: dissolved in toluene it is in a
monomer-dimer equilibrium. We recently found that Zn hy-
dride complexes seem to become less stable with increasing
cluster size: the coupled β-diketiminate Zn hydride complex V
decomposes at 80 °C, i.e. at a significantly lower temperature
than IV (150 °C).[10] For stability it is crucial that short H···H
distances and therefore H–Zn–H bridges are avoided. This ex-
plains the generally high stability of monomeric Zn hydride
complexes.
Monomeric zinc hydrides or complexes with terminal Zn–
H functionalities are of interest as model systems for zinc en-
zymes,[7,11] or as precursors in material chemistry.[12] Well-
defined Zn hydride complexes also found their way in the field
of catalysis.[13] Being generally more covalent than early main
group metal hydride catalysts, their mild reactivity has clear
advantages for functional group tolerance. Several groups have
found that cationic Zn hydride complexes show a very versa-
tile reactivity in catalysis.[14] The high reactivity of cationic
species may be explained by an increased Lewis acidity of the
metal center.
* Prof. Dr. S. Harder
E-Mail: sjoerd.harder@fau.de
[a] Inorganic and Organometallic Chemistry
Friedrich-Alexander-Universität Erlangen-Nürnberg
Egerlandstraße 1
91058 Erlangen, Germany
It is for this reason that we became interested in low-coordi-
nate Zn hydride complexes, in which the metal center should
be considerably more Lewis-acidic than in complexes with
higher coordination numbers. We recently introduced a “true”
tricoordinate Zn hydride complex (VI) which, in contrast to
the β-diketiminate complex IV, is also in solution mono-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201900179 or from the au-
thor.
© 2019 The Authors. Published by Wiley-VCH Verlag GmbH &
Co. KGaA. · This is an open access article under the terms of the
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meric.[15] The key to control mononuclearity is the dipyrrome- ligands with DIPP[15] and 9-anthracenyl[16] substituents have
thene ligand which we abbreviate in here as DIPPDPM (DIPP been introduced by us and are orange and red, respectively.
= 2, 6-diisopropylphenyl). Although this ligand has close simi- For the synthesis of Zn hydride complexes we chose a path-
larity to β-diketiminate ligands, there are two main differences. way previously introduced for the preparation of complex IV
First of all, the bulky aryl substituents in the pole positions (Scheme 1).[9b] The first step is the conversion of the ligands
(1,9-positions) are arranged differently, resulting in a defined to (RDPM)ZnEt (2-R) complexes which can be simply
cavity for the metal center. We could show in a previous publi- achieved in quantitative yields by reaction of the ligand with
cation that even highly labile heteroleptic Ba complexes can Et2Zn in benzene at 60 °C but for increased purity the com-
be stabilized effectively by the dipyrromethene ligand.[16] Sec- plexes have been recrystallized from toluene at –20 °C. The
ondly, electron density calculations suggest that the central latter alkylzinc complexes react smoothly with I2 to give a
backbone carbon in dipyrromethene is much less negatively series of (RDPM)ZnI (3-R) complexes in quantitative yields.
charged compared to that in β-diketiminate ligands.[15] There- Complexes were recrystallized from yields varying from 48%
fore, the DPM ligands may be more inert and more appropriate to 95% (lower recrystallization yields are generally due to high
spectator ligands.
solubility). Starting from the iodide complexes, the Zn hy-
We introduce here a comprehensive series of (RDPM)ZnH drides (4-R) are accessible by salt metathesis with KN(iPr)
complexes and evaluate the influence of the ligand substituent HBH3. For this particular step the yields are generally lower.
R on complex nuclearity and the metal coordination number.
We presume that the intermediate Zn amidoborane com-
In order to boost the reactivity of these complexes, we also plexes, (RDPM)ZnN(iPr)HBH3, are highly labile and after β-
discuss attempts to isolate cationic complexes by abstraction hydride elimination give (RDPM)ZnH and [N(iPr)HBH2]n.
of the hydride using the strong Lewis acid B(C6F5)3.
Due to the low solubility of (AnthDPM)ZnI and (Mes*DPM)
ZnI, the Zn hydride complexes of these ligands were not easily
accessible via the salt metathesis route. In these cases the eth-
ylzinc intermediates were first reacted with Ph3SiOH to give
(RDPM)ZnOSiPh3 (5-R), which reacted in a second step with
PhSiH3 to give the hydrides. This route has previously been
shown successful by the groups of Williams and Okuda.[19]
Like the related (RDPM)BF2 complexes (BODIPY),[20] all Zn
hydride complexes are highly colored and fluorescent crystal-
line products. While alkyl-, Mes- and DIPP-substituted Zn hy-
dride complexes are orange the Mes* and Anth-substituted
complexes are red. The melting/decomposition points of the
Zn hydride complexes are all relatively high and vary from
187–281 °C. The highest stabilities have been found for the
Mes* and Anth-substituted Zn hydride complexes, i.e. the
complexes with the most shielded Zn-H units.
Crystal Structures
The Zn hydride complexes (4-R) as well as the Zn ethyl (2-
R) and Zn iodide (3-R) intermediates along the path have been
characterized by single-crystal X-ray diffraction (Figure 1, Fig-
ure 2, and Table 1). Whereas all the Zn ethyl complexes are
monomeric, some of the iodides and hydrides form loosely
bound dimers in the solid state. In these dimers, the H– or I–
anions bridge asymmetrically: bonds within the N2Zn plane
are considerably shorter than those perpendicular on this plane.
The tendency to form dimers increases from Zn ethyl (never
dimer) Ͼ iodide (dimer for R = tBu) Ͼ hydride (dimer for R
= tBu and Ad). All complexes with aryl-substituted ligands are
monomeric, whereas ligands with bulky alkyl substituents tend
to form dimeric complexes. This is due to the fact that tBu or
Results and Discussion
Syntheses
All dipyrromethene ligands were prepared by the general adamantyl substituents restrict the space for metal coordina-
route developed by Betley and co-workers (Scheme 1) and are tion. Consequently, for the alkyl-substituted DPM ligands, the
strongly colored compounds. The tBu and adamantyl (Ad) sub- Zn atom is always situated 0.8–1.0 Å out of the NCCCN plane.
stituted ligands are yellow-brown powders.[17] The mesityl Since aryl substituents extend mainly in two dimensions, they
(Mes)[18] and 2,4,6-triphenyl-phenyl (Mes*)[17] substituted li- are less bulky and allow for binding of the Zn metal in or
gands are bright yellow and red, respectively. Dipyrromethene close to the NCCCN plane, thus providing substantially better
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Scheme 1. Syntheses of dipyrromethene ligands (1-R) and the Zn hydride complexes (4-R). Yields relate to crystallized products.
Figure 1. Crystal structures of dipyrromethene Zn hydride complexes; for clarity only the hydride H is shown and the mesityl group in the
backbone has been reduced to its Cipso. (a) [(tBuDPM)ZnH]2, (b) [(AdDPM)ZnH]2, (c) (MesDPM)ZnH, (d) (DIPPDPM)ZnH,[15] (e) (Mes*DPM)
ZnH, and (f) (AnthDPM)ZnH.
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distances to DPM ligands are in general longer than those to
comparable BDI ligands. This has been related to the some-
what lower negative charge on the N atoms in DMP ligands
compared to those in BDI.
It was anticipated that the extended 2,4,6-triphenyl-phenyl
substituents (Mes*) would span a large cavity for the metal
center. However, the crystal structures with the Mes*DPM li-
gand all show cavities that to a certain extent collapsed. The
NC4 rings and the attached aryl rings in (Mes*DPM)ZnH (Fig-
ure 1e) are not perpendicular to each other but angles of
60.8(1)° and 69.4(1)° are found. This is likely attributed to C–
H···π interactions between the Mes* substituents.
Within the series of monomeric (RDPM)ZnEt complexes,
there is hardly any influence of the substituent R on the Zn
coordination arrangement. The Zn–N bonds vary from
1.977(1) Å to 2.000(1) Å, the Zn–C distances are in the narrow
range of 1.953(2)–1.974(3) Å and the N–Zn–N’ angles have
values between 93.21(7)° and 94.54(6)°. Similar observations
are made within the series of monomeric (RDPM)ZnI and
(RDPM)ZnH complexes. This means that the substitution
pattern is irrelevant to Zn coordination but at most changes
the size and form of the ligand’s cavity and determines the
aggregation state.
Data in Table 1 also clearly show that the ligand bite angles,
N–Zn–N’, in Zn iodide complexes are somewhat larger than
those in the Zn ethyl or hydride complexes. These larger bite
angles are directly related to the shorter Zn–N bonds in the
iodide series. The latter is due to the fact that the iodide ligand
is much softer and weakly coordinating than ethyl or hydride
ligands, thus strengthening the Zn–N bonds and increasing the
bite angles.
Solution Studies
All Zn hydride complexes are soluble in C6D6 except for
(
AnthDPM)ZnH·(THF), which was dissolved in [D8]THF. Dif-
fusion-Ordered-Spectroscopy (DOSY) shows that most com-
plexes are monomeric in benzene (Table S19, Supporting In-
formation). This includes the loosely bound dimer [(AdDPM)
ZnH]2 but not [(tBuDPM)ZnH]2 which is in a dimer-monomer
equilibrium. Not surprisingly, complex (AnthDPM)ZnH·(THF)
in [D8]THF was also found to be monomeric.
Figure 2. Crystal structures of the dipyrromethene Zn iodide com-
plexes: (a) (AdDPM)ZnI (3-Ad) and (b) (DIPPDPM)ZnI (3-DIPP).[15]
shielding of the metal. This is nicely illustrated by comparison
The Zn–Et and Zn–H chemical shifts deserve special atten-
of the structures of (AdDPM)ZnI and (DIPPDPM)ZnI (Figure 2). tion. The H NMR shifts for the Et groups lie in a very broad
For the adamantyl-substituted ligand the Zn and I centers range (Table 1). The Zn–CH2 chemical shifts vary from +1.11
strongly bend out-of-plane due to space limitation. Very short to –1.95 ppm while the CH3 groups are scattered between
C–H···Zn agostic interactions (striped lines in Figure 1a; 2.382 +1.66 to –1.01 ppm. The same holds for the Zn-H signals
and 2.435 Å) illustrate the enormous steric pressure in which can be found in the range of +5.75 to +2.57 ppm. The
1
(
AdDPM)ZnI. Similar out-of-plane bonding and short agostic large variance in these values can be related to the ASIS effect
interactions are found in the dimeric complexes. In contrast, (Aromatic-Solvent-Induced-Shift)[21] in which nuclei posi-
the ligand with DIPP-substituents enables in-plane bonding of tioned above an aromatic ring experience a strong upfield shift.
the Zn–I unit (Figure 2b). The DIPP-plane makes a nearly per- Consequently, the Zn–H moieties in complexes with alkyl-sub-
pendicular angle of 87.26(7)° with the NC4 ring. Both DIPP- stituted ligands do not experience any ASIS effect and feature
substituents form a cavity around the metal center which fits the highest chemical shifts (5.45–5.75 ppm). With increasing
the Zn-I unit but there is no Zn–aryl contact: the shortest encapsulation, the hydride resonances shift to lower ppm val-
Zn···C distances measure 3.325(2)–3.419(2) Å. As we men- ues. It is noteworthy that the Zn–H shift for (DIPPDPM)ZnH
tioned previously,[15] it should also be noted that the Zn–N (δ =3.78 ppm)][15] is substantially lower than that for the β-
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Table 1. Selected geometric parameter for the crystal structures (average bond lengths in Å and angles in °) and 1H NMR chemical shifts (ppm).
a)
(RDPM)ZnEt
Aggregation
Zn–N
Zn–Et
N–Zn–N’
NCCCN/Zn
δ Et /ppm
R = tBu
R = Ad
R = Mes
R = DIPP [15]
R = Mes*
R = Anth
monomer
monomer
monomer
monomer
monomer
monomer
1.990(2)
1.993(1)
1.991(2)
1.989(2)
1.977(1)
2.000(2)
1.974(3)
1.969(3)
1.973(2)
1.965(2)
1.953(2)
1.965(2)
93.21(7)
93.86(5)
94.07(6)
93.40(6)
94.21(5)
94.54(6)
0.839(1)
0.869(1)
0.219(1)
0.033(1)
0.003(1)
0.040(1)
1.60 / 0.97
1.66 / 1.11
0.64 / –0.20
0.46 / –0.31
0.86 / 0.16
–1.01 /
–1.95
a)
(RDPM)ZnI
Aggregation
dimer
Zn–N
Zn–I
N–Zn–N’
95.42(8)
NCCCN/Zn
0.883(1)
R = tBu
1.983(2)
2.5928(4) /
b)
2.8483(4)
2.4655(5)
2.4478(5)
2.4428(4)
2.4655(6)
R = Ad
R = Mes
R = DIPP [15]
R = Mes*
monomer
monomer
monomer
monomer
1.939(2)
1.940(2)
1.945(2)
1.941(2)
96.22(8)
98.09(7)
98.37(8)
97.46(9)
0.799(1)
0.027(1)
0.151(1)
0.010(1)
a)
(RDPM)ZnH
Aggregation
Zn–N
Zn–Et
N–Zn–N’
NCCCN/Zn
δ H /ppm
b)
b)
R = tBu
R = Ad
R = Mes
R = DIPP[15]
R = Mes*
dimer
dimer
monomer
monomer
monomer
monomer
1.976(2)
1.973(2)
1.973(2)
1.973(1)
1.970(2)
2.025(2)
1.50(4) / 2.00(4)
1.46(3) / 1.99(3)
1.51(3)
1.49(3)
1.43(3)
93.28(9)
96.41(6)
95.1(1)
93.68(5)
92.33(7)
93.27(6)
0.980(1)
0.889(1)
0.013(1)
0.101(1)
0.155(1)
0.046(1)
5.45
5.73
3.96
3.78
4.03
2.57
c)
R = Anth
1.55(3)
a) Defined as the distance between the least-squares-plane NCCCN and the Zn atom in Å. b) Asymmetric bridging. The shorter bond length
lies in the N2Zn plane while the longer bond length is perpendicular to this plane. c) The arrangement for the THF adduct (AnthDPM)ZnH·(THF)
is given. The Zn–O distance is 2.127(2) Å.
diketiminate complex (DIPPBDI)ZnH (δ = 4.39 ppm).][9b] This of the reaction products by X-ray diffraction led us to propose
can be attributed to the more pronounced encapsulation of the the reactivity as shown in Scheme 2.
Zn–H unit in the diypyrromethene ligand.
Instead of hydride abstraction, a cleavage of the B–C6F5
As we reported earlier, the angles between the DIPP-planes bond by Zn-H occurred. Reaction of a second equivalent of
[23]
in DIPPDPM [46.7(1)°] and those in DIPPBDI [126.4(1)°] are the Zn hydride complex with the Piers borane HB(C6F5)2
–
quite different.[15] The highest upfield shift, i.e. largest ASIS gave the salt with H2B(C6F5)2 anion. Cleavage of the B–C
effect, was found for the anthracenyl-substituted Zn hydride bond in B(C6F5)3 is relatively rare and generally observed for
complex: (AnthDPM)ZnH·(THF). The 1H NMR chemical shifts species with highly Lewis acidic metal centers (e.g. Ti4+ or
for the Zn-Et groups follow the same order and also (AnthDPM) Al3+).[24] We presume that the low coordination number of Zn
ZnEt features unusually low chemical shifts for the Et group.
in the Zn hydride complexes presented here makes the Zn cen-
ters also unusually Lewis acidic, explaining why attempted
isolation of cationic dipyrromethene Zn complexes resulted in
B–C6F5 bond cleavage.
Attempted Conversion to Cationic Complexes
Cationic Zn hydride complexes show increased activity in
catalysis.[4,14] There is also growing awareness that Zn hydride
Conclusions
[22]
complexes in combination with either BPh3[14c] or B(C6F5)3
generate efficient catalysts for CO2 hydrosilylation.
Monomeric low-coordinate Zn hydride complexes are ac-
In order to isolate cationic Zn complexes, (DIPPDPM)ZnH in cessible by use of dipyrromethene ligands. It is essential that
C6D6 was reacted with B(C6F5)3 at room temperature. Within the substituents in the pole positions are aryl groups. Alkyl
minutes full conversion into two new species in a 1/1 ratio was substituents restrict the space available for metal coordination,
observed (Figure S37) but surprisingly only 0.5 equivalent of which results in a shift of the metal out of the NCCCN plane.
B(C6F5)3 had been consumed. Both products dissolve well in Consequently, Zn hydride complexes with alkyl-substituted di-
hexane and crystallization at low temperature gave a few crys- pyrromethene ligands crystallize as dimeric entities with four-
tals which were identified as (DIPPDPM)ZnC6F5 (Figure 3a). coordinate Zn centers. These dimers are, however, loosely
Although we did not manage to obtain good quality crystals bound. This is indicated by asymmetric bridging of the hydride
of the second species, a similar experiment with (MesDPM) ligands with two short and two long Zn–H bonds of circa 1.5
ZnH gave after reaction with B(C6F5)3 crystals of (MesDPM) and 2.0 Å, respectively, and is also in agreement with mono-
Zn[H2B(C6F5)2] (Figure 3b). Although both species could not mer-dimer equilibria in solution.
be obtained pure, the stoichiometry of the reaction combined
The Zn hydride complexes with aryl-substituted dipyrrome-
with NMR analysis of the raw reaction mixtures (Figures S36 thene ligands are truly monomeric and feature tricoordinate
and S37, Supporting Information) and identification of some Zn centers, in the solid state as well as in solution. The aryl
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of the hydride ligand with B(C6F5)3 led to an unexpected
cleavage of the B-C6F5 bond and formation of (DPM)ZnC6F5
and (DPM)Zn[H2B(C6F5)2] complexes. This reactivity is likely
related to the high Lewis acidity of tricoordinate Zn centers.
Experimental Section
General Experimental Procedures: All experiments were carried out
in dry glassware in a N2 atmosphere using standard Schlenk techniques
and freshly dried and degassed solvents (all solvents were dried with
a column except for THF, which was dried with Na and redistilled).
Starting materials and research chemicals were obtained from commer-
cial suppliers, where appropriate and used without further purification.
Diethylzinc,[25] K[(iPr)NHBH3],[26] tBuDPM-H,[17] AdDPM-H,[17]
MesDPM-H,[18] DIPPDPM-H,[15] Mes*DPM-H,[17] AnthDPM-H[16] and
(
DIPPDPM)ZnH[15] were synthesized following literature known pro-
cedures. NMR spectra were measured on Bruker Avance III HD
400 MHz and Bruker Avance III HD 600 MHz spectrometers. Chemi-
cal shifts (δ) are given in ppm (parts per million) values, coupling
constants (J) in Hz (Hertz). For describing signal multiplicities com-
mon abbreviations were used: s (singlet), d (doublet), t (triplet), q
(quartet), m (multiplet) and br (broad). Spectra were referenced due to
solvent residual signal. Elemental analysis was performed with a Hek-
atech Eurovector EA3000 analyzer. All crystal structures have been
measured on a SuperNova (Agilent) diffractometer with dual Cu and
Mo microfocus sources and an Atlas S2 detector.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK. Copies
of the data can be obtained free of charge on quoting the depository
numbers CCDC-1944426 for (tBuDPM)ZnEt, CCDC-1944427 for
Figure 3. (a) Crystal structure of (DIPPDPM)ZnC6F5. Selected bond
lengths /Å: Zn–N1 1.946(2), Zn–N2 1.956(2), Zn–C1 1.956(2). (b)
Crystal structure of (MesDPM)Zn[H2B(C6F5)2]. Selected bond lengths /
Å: Zn–N1 1.929(2), Zn–N2 1.938(2), Zn···B 2.221(2), Zn-H1 1.84(2),
Zn-H2 1.77(2).
(
(
(
tBuDPM)ZnI, CCDC-1944428 for (tBuDPM)ZnH, CCDC-1944429 for
AdDPM)ZnEt, CCDC-1944430 for (AdDPM)ZnI, CCDC-1944431 for
AdDPM)ZnH, CCDC-1944432 for (MesDPM)ZnEt, CCDC-1944433
for
( (
MesDPM)ZnI, CCDC-1944434 for MesDPM)ZnH, CCDC-
1944435 for (Mes*DPM)ZnEt, CCDC-1944436 for (Mes*DPM)ZnI,
CCDC-1944437 for (Mes*DPM)ZnH, CCDC-1944438 for (Mes*DPM)
ZnOSiPh3, CCDC-1944439 for (AnthDPM)ZnEt , CCDC-1944440 for
(
AnthDPM)ZnEt·(THF), CCDC-1944441 for (AnthDPM)ZnH·(THF),
CCDC-1944442 for
MesDPM)Zn[H2B(C6F5)2] (Fax: +44-1223-336-033; E-Mail: deposit-
(
DIPPDPM)ZnC6F5, and CCDC-1944443 for
(
@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk)
Synthesis of (tBuDPM)ZnEt (2-tBu): In a 25 mL Schlenk flask
tBuDPM-H (712 mg, 1.900 mmol) was dissolved in benzene (10 mL).
Neat Et2Zn (234 μL, 2.279 mmol, 1.2 equiv.) was added to the stirred
yellow solution resulting in a color change to orange. The reaction
mixture was heated to 60 °C overnight and the solvent was removed
in vacuo yielding an orange powder in quantitative yield. Recrystalli-
zation from n-hexane at –20 °C yielded orange crystalline blocks.
Yield: 782 mg (1.677 mmol; 88%). 1H NMR (600 MHz, C6D6,
25 °C): δ = 6.75 (s, 2 H, Mes-aryl-CH), 6.68 (d, J = 4.1 Hz, 2 H,
pyrrole-CH), 6.35 (d, J = 4.1 Hz, 2 H, pyrrole-CH), 2.18 [s, 3 H,
C6H2(CH3)3], 2.12 [s, 6 H, C6H2(CH3)3], 1.60 (t, J = 8.1 Hz, 3 H,
ZnCH2CH3), 1.41 (s, 18 H, tBu-CH3), 0.97 (q, J = 8.1 Hz, 2 H,
ZnCH2CH3) ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 173.0
(Carom), 145.5 (Carom), 139.1 (Carom), 137.2 (Carom), 137.0 (Carom),
136.1 (Carom), 132.4 (Carom), 128.1 (Carom), 115.5 (Carom), 34.1 (Caliph),
30.8 (Caliph), 21.5 (Caliph), 20.1 (Caliph), 12.3 (Caliph), 6.2 (Caliph) ppm.
C28H38N2Zn (466.23 g·mol–1): calcd. C 71.86, H 8.18, N 5.99; found:
Scheme 2. Reaction of (RDPM)ZnH complexes (R = DIPP or Mes)
with 0.5 equivalent of B(C6F5) gives a 1/1 mixture of (RDPM)ZnC6F5
and (RDPM)Zn[H2B(C6F5)2].
substituents span a cavity around the Zn metal and successfully
block dimerization. This is also evident from the 1H NMR
chemical shifts of the Zn-Et and Zn-H groups which are un-
usually shifted to higher field on account of the ASIS effect.
Attempted synthesis of cationic Zn complexes by abstraction C 71.44, H 8.14, N 5.53%.
Z. Anorg. Allg. Chem. 2019, 1–11
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
1
Synthesis of (tBuDPM)ZnI (3-tBu): In a 50 mL Schlenk flask
tBuDPM)ZnEt (413 mg, 0.886 mmol) was dissolved in benzene
Yield: 969 mg (1.35 mmol; 95%). H NMR (600 MHz, C6D6, 25 °C):
δ = 6.73 (s, 2 H, Mes-aryl-CH), 6.67 (br., 2 H, pyrrole-CH), 6.37 (br.,
(
(15 mL). A solution of elemental iodine (247 mg, 0.975 mmol, 2 H, pyrrole-CH), 2.31 (s, 12 H, Ad-α-CH2), 2.17 [s, 3 H,
1.1 equiv.) in n-heptane (10 mL) was added at room temperature. The
reaction mixture was stirred at room temperature overnight and the
solvent and excess of iodine were removed in vacuo yielding an orange
powder in quantitative yield. Trituration with pentane (2ϫ6 mL) and
recrystallization in a toluene/n-hexane mixture at –20 °C yielded crys-
C6H2(CH3)3], 2.02 [s, 12 H, C6H2(CH3)3], 2.00 (br., 6 H, Ad-CH),
1.86–1.84 (m, 6 H, Ad-CH), 1.62–1.60 (m, 6 H, Ad-CH) ppm. 13C{1H}
NMR (151 MHz, C6D6, 25 °C): δ = 173.9 (Carom), 145.5 (Carom), 139.0
(Carom), 137.6 (Carom), 137.0 (Carom), 135.5 (Carom), 133.4 (Carom),
128.2 (Carom), 115.8 (Carom), 42.2 (Caliph), 36.6 (Caliph), 36.6 (Caliph),
talline orange blocks. Yield: 380 mg (0.674 mmol; 76%). 1H NMR 29.0 (Caliph), 21.1 (Caliph), 19.9 (Caliph
) ppm. C38H45N2ZnI
(600 MHz, C6D6, 25 °C): δ = 6.72 (s, 2 H, Mes-aryl-CH), 6.62 (d, J (720.19 g·mol–1): calcd. C 63.21, H 6.28, N 3.88; found: C 63.15, H
= 4.0 Hz, 2 H, pyrrole-CH), 6.28 (br., 2 H, pyrrole-CH), 2.16 [s, 3 H, 6.35, N 3.82%.
C6H2(CH3)3], 2.03 [s, 6 H, C6H2(CH3)3], 1.48 (s, 18 H, tBu-CH3)
Synthesis of (AdDPM)ZnH (4-Ad): In a 50 mL Schlenk flask
ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 173.9 (Carom), 145.5
(
AdDPM)ZnI (650 mg, 0.903 mmol) was dissolved in benzene (20 mL)
(Carom), 139.0 (Carom), 137.6 (Carom), 136.9 (Carom), 135.4 (Carom),
133.6 (Carom), 128.1 (Carom), 116.3 (Carom), 34.3 (Caliph), 31.1 (Caliph),
21.1 (Caliph), 19.9 (Caliph) ppm. C26H33N2ZnI (564.10 g·mol–1): calcd.
C 55.19, H 5.88, N 4.95; found: C 55.74, H 5.53, N 4.82%.
and K[(iPr)NHBH3] (150 mg, 1.35 mmol, 1.5 equiv.) was added. The
milky orange suspension was stirred at room temperature overnight
and filtered to give an orange solution. Removal of solvent in vacuo
gave the crude product as orange solid. Recrystallization from a con-
centrated pentane solution at room temperature yielded crystalline
orange blocks. Yield: 380 mg (0.640 mmol; 71%). M.p.: 281 °C –
Synthesis of (tBuDPM)ZnH (4-tBu): In a 50 mL Schlenk flask
(
tBuDPM)ZnI (380 mg, 0.674 mmol) was dissolved in benzene (20 mL)
and K[(iPr)NHBH3] (112 mg, 1.009 mmol, 1.5 equiv.) was added. The 283 °C (dec.). 1H NMR (600 MHz, C6D6, 25 °C): δ = 6.80 (s, 2 H,
milky orange suspension was stirred at room temperature overnight
and filtered through a syringe filter to give an orange solution. Re-
moval of solvent in vacuo gave the crude product as orange solid.
Recrystallization in a concentrated pentane solution at –20 °C yielded
Mes-aryl-CH), 6.70 (d, J = 4.1 Hz, 2 H, pyrrole-CH), 6.38 (d, J =
4.1 Hz, 2 H, pyrrole-CH), 5.73 (s, 1 H, ZnH), 2.28 (s, 12 H, Ad-α-
CH2), 2.22 [s, 3 H, C6H2(CH3)3], 2.18 [s, 6 H, C6H2(CH3)3], 1.99 (br.,
6 H, Ad-CH), 1.83–1.81 (m, 6 H, Ad-CH), 1.65–1.63 (m, 6 H, Ad-
crystalline orange blocks. Yield: 213 mg (0.486 mmol; 72%). M.p.: CH) ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 173.2 (Carom),
187 °C – 192 °C (dec.) 1H NMR (600 MHz, C6D6, 25 °C): δ = 6.78 144.0 (Carom), 138.5 (Carom), 136.1 (Carom), 135.9 (Carom), 135.4
(s, 2 H, Mes-aryl-CH), 6.65 (d, J = 4.1 Hz, 2 H, pyrrole-CH), 6.34 (d,
(Carom), 131.5 (Carom), 126.9 (Carom), 114.5 (Carom), 41.7 (Caliph), 35.9
J = 4.1 Hz, 2 H, pyrrole-CH), 5.45 (s, 1 H, ZnH), 2.20 [s, 3 H, (Caliph), 35.6 (Caliph), 28.1 (Caliph), 20.0 (Caliph), 19.0 (Caliph) ppm.
C6H2(CH3)3], 2.16 [s, 6 H, C6H2(CH3)3], 1.48 (s, 18 H, tBu-CH3)
C38H46N2Zn (594.30 g·mol–1): calcd. C 76.56, H 7.78, N 4.70; found:
ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 174.0 (Carom), 145.3 C 76.04, H 8.01, N 4.55%.
(Carom), 139.7 (Carom), 137.3 (Carom), 137.1 (Carom), 136.3 (Carom),
Synthesis of (MesDPM)ZnEt (2-Mes): In a 50 mL Schlenk flask
132.8 (Carom), 128.2 (Carom), 116.0 (Carom), 34.8 (Caliph), 31.5 (Caliph),
21.2 (Caliph), 20.2 (Caliph) ppm. C26H34N2Zn (438.20 g·mol–1): calcd.
C 70.98, H 7.79, N 6.37; found: C 71.49, H 7.85, N 6.40%.
MesDPM-H (1.98 g, 3.97 mmol) was suspended in benzene (25 mL).
Neat Et2Zn (488 μL, 4.76 mmol, 1.2 equiv.) was added to the stirred
yellow ochre suspension resulting in a bright orange solution. The re-
action mixture was heated to 60 °C overnight and the solvent was
Synthesis of (AdDPM)ZnEt (2-Ad): In a 50 mL Schlenk flask
AdDPM-H (775 mg, 1.50 mmol) was dissolved in benzene (20 mL). removed in vacuo yielding an orange powder in quantitative yield.
Neat Et2Zn (185 μL, 1.801 mmol, 1.2 equiv.) was added to the stirred Recrystallization from benzene at room temperature yielded orange
yellow ochre solution resulting in a color change to orange. The reac-
tion mixture was heated to 60 °C overnight and the solvent was re-
crystalline blocks. Yield: 2.28 g (3.86 mmol; 97%). 1H NMR
(600 MHz, C6D6, 25 °C): δ = 6.86 (s, 2 H, Mes-aryl-CH), 6.79 (s, 4
moved in vacuo yielding an orange powder in quantitative yield. H, Mes-aryl-CH), 6.76 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 6.20 (d, J =
Recrystallization from n-hexane at –20 °C yielded orange crystalline 4.0 Hz, 2 H, pyrrole-CH), 2.29 [s, 6 H, C6H2(CH3)3], 2.24 [s, 3 H,
blocks. Yield: 859 mg (1.38 mmol; 92%). 1H NMR (600 MHz, C6D6,
C6H2(CH3)3], 2.19 [s, 12 H, C6H2(CH3)3], 2.10 [s, 6 H, C6H2(CH3)3],
25 °C): δ = 6.76 (s, 2 H, Mes-aryl-CH), 6.73 (d, J = 4.2 Hz, 2 H, 0.64 (t, J = 8.1 Hz, 3 H, ZnCH2CH3), –0.20 (q, J = 8.1 Hz, 2 H,
pyrrole-CH), 6.42 (d, J = 4.2 Hz, 2 H, pyrrole-CH), 2.19 [br., 15 H, ZnCH2CH3) ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 162.5
C6H2(CH3)3 and Ad-α-CH2], 2.13 [s, 6 H, C6H2(CH3)3], 1.97 (br., 6 (Carom), 146.1 (Carom), 140.0 (Carom), 138.0 (Carom), 137.5 (Carom),
H, Ad-CH), 1.77–1.73 (m, 6 H, Ad-CH), 1.68–1.63 (m, 9 H, Ad-CH
and ZnCH2CH3), 1.11 (q, J = 8.1 Hz, 2 H, ZnCH2CH3) ppm. 13C{1H}
137.0 (Carom), 136.9 (Carom), 135.9 (Carom), 133.4 (Carom), 132.2
(Carom), 128.7 (Carom), 128.2 (Carom), 119.6 (Carom), 21.2 (Caliph), 21.2
NMR (151 MHz, C6D6, 25 °C): δ = 173.0 (Carom), 145.4 (Carom), 139.0 (Caliph), 20.8 (Caliph), 20.2 (Caliph), 11.28 (Caliph), –0.3 (Caliph) ppm.
(Carom), 137.2 (Carom), 137.0 (Carom), 136.2 (Carom), 132.2 (Carom), C38H42N2Zn (590.26 g·mol–1): calcd. C 77.08, H 7.15, N 4.73; found:
128.0 (Carom), 115.1 (Carom), 42.7 (Caliph), 36.9 (Caliph), 36.4 (Caliph), C 76.75, H 7.13, N 4.64%.
29.1 (Caliph), 21.2 (Caliph), 20.1 (Caliph), 12.5 (Caliph) ppm. C40H50N2Zn
Synthesis of (MesDPM)ZnI (3-Mes): In a 50 mL Schlenk flask
(622.33 g·mol–1): calcd. C 76.96, H 8.07, N 4.49; found: C 77.00, H
(
MesDPM)ZnEt (400 mg, 0.677 mmol) was dissolved in benzene
8.09, N 4.08%.
(12 mL). A solution of elemental iodine (189 mg, 0.745 mmol,
1.1 equiv.) in n-heptane (10 mL) was added at room temperature. The
Synthesis of (AdDPM)ZnI (3-Ad): In a 50 mL Schlenk flask (AdDPM)
ZnEt (880 mg, 1.41 mmol) was dissolved in benzene (12 mL). A solu- reaction mixture was stirred at room temperature overnight and the
tion of elemental iodine (395 mg, 1.56 mmol, 1.1 equiv.) in n-heptane
(15 mL) was added at room temperature. The reaction mixture was
stirred at room temperature overnight and the solvent and excess of
iodine were removed in vacuo yielding an orange powder in quantita-
solvent and excess of iodine were removed in vacuo yielding an orange
powder in quantitative yield. Trituration with n-hexane (3ϫ3 mL) and
recrystallization in a toluene/n-hexane mixture at –20 °C yielded crys-
talline orange blocks. Yield: 409 mg (0.595 mmol; 88%). 1H NMR
tive yield. Trituration with n-hexane (2ϫ4 mL) and recrystallization in (400 MHz, C6D6, 25 °C): δ = 6.83 (s, 2 H, Mes-aryl-CH), 6.82 (s, 4
a toluene/pentane mixture at –20 °C yielded crystalline orange blocks. H, Mes-aryl-CH), 6.76 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 6.12 (d, J =
Z. Anorg. Allg. Chem. 2019, 1–11
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
4.1 Hz, 2 H, pyrrole-CH), 2.24 [s, 3 H, C6H2(CH3)3], 2.21 [s, 6 H, 2 H, Mes-aryl-CH), 6.12 (d, J = 4.1 Hz, 2 H, pyrrole-CH), 5.88 (d, J
C6H2(CH3)3], 2.16 [s, 12 H, C6H2(CH3)3], 2.11 [s, 6 H, C6H2(CH3)3] = 4.1 Hz, 2 H, pyrrole-CH), 2.18 (s, 3 H, C6H2(CH3)3), 1.92 (s, 6 H,
ppm. 13C{1H} NMR (101 MHz, C6D6, 25 °C): δ = 163.4 (Carom), 146.0 C6H2(CH3)3) ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 161.5
(Carom), 140.0 (Carom), 138.7 (Carom), 137.8 (Carom), 136.9 (Carom), (Carom), 145.2 (Carom), 143.3 (Carom), 142.8 (Carom), 142.0 (Carom),
136.9 (Carom), 135.3 (Carom), 133.1 (Carom), 131.7 (Carom), 129.0 141.1 (Carom), 139.6 (Carom), 137.5 (Carom), 136.6 (Carom), 135.1
(Carom), 127.9 (Carom), 120.4 (Carom), 21.3 (Caliph), 21.2 (Caliph), 20.9
(Carom), 131.6 (Carom), 131.4 (Carom), 130.4 (Carom), 129.1 (Carom),
(Caliph), 20.0 (Caliph) ppm. C36H37N2ZnI (688.13 g·mol–1): calcd. C 128.7 (Carom), 128.1 (Carom), 128.0 (Carom), 127.8 (Carom), 127.7
62.67, H 5.41, N 4.06; found: C 63.02, H 5.37, N 3.97%.
(Carom), 126.9 (Carom), 122.9 (Carom), 21.4 (Caliph), 19.8 (Caliph) ppm.
Several attempts to obtain satisfactory elemental analytical data were
without success. Although the C and N values are outside the range
viewed as establishing analytical purity, they are provided to illustrate
the best values obtained to date. C66H49N2IZn (1062.42 g·mol–1):
calcd. C 74.62, H 4.65, N 2.64; found: C 76.55, H 5.01, N 2.19%.
Due to the poor solubility of (Mes*DPM)ZnI, attempted synthesis of
Synthesis of (MesDPM)ZnH (4-Mes): In a 25 mL Schlenk flask
(
MesDPM)ZnI (256 mg, 0.372 mmol) was dissolved in benzene
(15 mL) and K[(iPr)NHBH3] (62.1 mg, 0.559 mmol, 1.5 equiv.) was
added. The milky orange suspension was stirred at room temperature
overnight and filtered through a syringe filter to give an orange solu-
tion. Removal of solvent in vacuo gave the crude product as orange
solid. Recrystallization from a concentrated toluene solution at –20 °C
yielded a first crop of crystalline orange blocks. Yield: 120 mg
(
Mes*DPM)ZnI via salt metathesis with K[(iPr)NHBH3] was not satis-
factory and an alternative pathway over intermediate (Mes*DPM)ZnO-
SiPh3 (5-Mes*) was chosen.
(0.213 mmol; 57%). M.p.: 243 °C
–
245 °C (dec.). 1H NMR
(600 MHz, C6D6, 25 °C): δ = 6.86 (s, 2 H, Mes-aryl-CH), 6.77 (s, 4
H, Mes-aryl-CH), 6.74 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 6.21 (d, J =
4.0 Hz, 2 H, pyrrole-CH), 3.96 (s, 1 H, ZnH), 2.28 [s, 6 H,
C6H2(CH3)3], 2.25 [s, 3 H, C6H2(CH3)3], 2.16 [s, 12 H, C6H2(CH3)3],
2.11 [s, 6 H, C6H2(CH3)3] ppm. 13C{1H} NMR (151 MHz, C6D6,
25 °C): δ = 162.6 (Carom), 146.1 (Carom), 139.9 (Carom), 138.0 (Carom),
137.6 (Carom), 136.9 (Carom), 136.9 (Carom), 135.7 (Carom), 132.9
(Carom), 132.3 (Carom), 128.6 (Carom), 128.4 (Carom), 119.8 (Carom), 21.2
(Caliph), 21.2 (Caliph), 20.9 (Caliph), 20.1 (Caliph) ppm. C36H38N2Zn
(562.23 g·mol–1): calcd. C 76.65, H 6.79, N 4.97; found: C 75.98, H
6.68, N 4.59%.
Synthesis of (Mes*DPM)ZnOSiPh3 (5-Mes*): In a 25 mL Schlenk
flask (Mes*DPM)ZnEt (213 mg, 0.221 mmol) was suspended in benz-
ene (10 mL). Neat Ph3SiOH (61 mg, 0.221 mmol, 1.0 equiv.) was
added at room temperature in one portion. The reaction mixture was
heated at 60 °C overnight. Residual solvent was removed in vacuo and
the crude product was triturated with n-hexane (3ϫ10 mL) to give a
purple solid. Yield: 169 mg (0.131 mmol; 60%). Single crystals (red
blocks) suitable for X-ray analysis were obtained from a toluene/THF
mixture at -20 °C. The complex crystallized as its THF adduct:
1
(
Mes*DPM)ZnOSiPh3·(THF). H NMR (600 MHz, C6D6, 25 °C): δ =
7.49 (d, J = 6.8 Hz, 6 H, phenyl-CH), 7.38 (s, 4 H, Mes-aryl-CH),
7.34–7.24 (m, 12 H, phenyl-CH), 7.21–7.17 (m, 4 H, phenyl-CH),
7.14–7.09 (m, 15 H, phenyl-CH), 6.96 (t, J = 7.4 Hz, 3 H, phenyl-
CH), 6.89 (t, J = 7.4 Hz, 6 H, phenyl-CH), 6.74 (s, 2 H, Mes-aryl-
CH), 6.14 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 5.8 (d, J = 4.1 Hz, 2 H,
pyrrole-CH), 2.19 [s, 3 H, C6H2(CH3)3], 1.99 [s, 6 H, C6H2(CH3)3]
ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 161.3 (Carom), 142.8
(Carom), 142.2 (Carom), 141.8 (Carom), 141.5 (Carom), 140.7 (Carom),
140.6 (Carom), 140.6 (Carom), 136.6 (Carom), 135.9 (Carom), 131.9
(Carom), 131.8 (Carom), 130.0 (Carom), 129.0 (Carom), 128.8 (Carom),
128.6 (Carom), 128.5 (Carom), 128.1 (Carom), 128.0 (Carom), 127.8
(Carom), 127.6 (Carom), 127.5 (Carom), 127.0 (Carom), 123.2 (Carom), 21.2
(Caliph), 20.0 (Caliph) ppm. Several attempts to obtain satisfactory ele-
mental analytical data were without success. Although the C value is
outside the range viewed as establishing analytical purity, it is provided
to illustrate the best values obtained to date. C88H72O2N2SiZn
(1283.02 g·mol–1): calcd. C 82.38, H 5.66, N 2.18; found: C 80.40, H
5.95, N 1.70%.
Synthesis of (Mes*DPM)ZnEt (2-Mes*): In a 50 mL Schlenk flask
Mes*DPM-H (422 mg, 0.485 mmol) was suspended in benzene
(15 mL). Neat Et2Zn (69.5 μL, 0.678 mmol, 1.4 equiv.) was added to
the stirred red suspension resulting in a pink solution. The reaction
mixture was heated to 60 °C overnight and the solvent was removed
in vacuo yielding a pink powder in quantitative yield. Recrystallization
from toluene/n-hexane at –20 °C yielded red crystalline blocks. Yield:
1
397 mg (0.412 mmol; 85%). H NMR (600 MHz, C6D6, 25 °C): δ =
7.70 (s, 4 H, Mes-aryl-CH), 7.43 (d, J = 7.1 Hz, 4 H, phenyl-CH),
7.31 (d, J = 6.9 Hz, 8 H, phenyl-CH), 7.24–7.14 (m, 18 H, phenyl-
CH), 6.77 (s, 2 H, Mes-aryl-CH), 6.19 (d, J = 4.0 Hz, 2 H, pyrrole-
CH), 5.87 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 2.20 [s, 3 H, C6H2(CH3)3],
2.03 [s, 6 H, C6H2(CH3)3], 0.86 (t, J = 8.1 Hz, 3 H, ZnCH2CH3), 0.16
(q, J = 8.1 Hz, 2 H, ZnCH2CH3) ppm. 13C{1H} NMR (151 MHz,
C6D6, 25 °C): δ = 160.7 (Carom), 145.2 (Carom), 143.5 (Carom), 142.4
(Carom), 142.2 (Carom), 141.0 (Carom), 139.5 (Carom), 137.1 (Carom),
136.6 (Carom), 135.9 (Carom), 133.0 (Carom), 130.1 (Carom), 129.9 (Ca-
rom), 129.1 (Carom), 128.6 (Carom), 128.1 (Carom), 128.0 (Carom), 127.8
(Carom), 127.7 (Carom), 126.8 (Carom), 122.1 (Carom), 21.2 (Caliph), 19.9
(Caliph), 11.1 (Caliph), 2.4 (Caliph) ppm. C68H54N2Zn (964.57 g·mol–1):
calcd. C 84.67, H 5.64, N 2.90; found: C 84.46, H 5.61, N 2.88%.
Synthesis of (Mes*DPM)ZnH (4-Mes*): In a 25 mL Schlenk flask
(
Mes*DPM)ZnOSiPh3 (169 mg, 0.132 mmol) was suspended in benz-
ene (15 mL) and PhSiH3 (17.0 μL, 0.138 mmol, 1.05 equiv.) was
added in one portion. The pink reaction mixture was stirred at room
temperature overnight. Removal of solvent in vacuo and trituration
Synthesis of (Mes*DPM)ZnI (3-Mes*): In a 50 mL Schlenk flask
(
Mes*DPM)ZnEt (399 mg, 0.414 mmol) was suspended in benzene with n-hexane (2ϫ5 mL) yielded the crude product as pink solid.
(20 mL). A solution of elemental iodine (110 mg, 0.433 mmol, Recrystallization from a concentrated toluene solution at –20 °C
1.05 equiv.) in n-heptane (15 mL) was added at room temperature. The yielded crystalline red blocks. Yield: 48 mg (0.051 mmol; 39%). M.p.:
1
reaction mixture was heated at 60 °C overnight and the solvent and 185 °C – 190 °C (dec.). H NMR (600 MHz, C6D6, 25 °C): δ = 7.72
excess of iodine were removed in vacuo yielding a dark purple powder. (s, 4 H, Mes-aryl-CH), 7.44–7.40 (m, 4 H, phenyl-CH), 7.33–7.29 (m,
Trituration with n-hexane (2ϫ15 mL) yielded a purple solid. Yield:
8 H, phenyl-CH), 7.20–7.16 (m, 12 H, phenyl-CH), 7.16–7.12 (m, 6
370 mg (0.348 mmol; 84%). Single crystals (red blocks) suitable for H, phenyl-CH), 6.78 (s, 2 H, Mes-aryl-CH), 6.18 (d, J = 4.0 Hz, 2 H,
X-ray analysis were obtained upon heating a suspension of the crude pyrrole-CH), 5.87 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 4.03 (s, 1 H, ZnH),
product in boiling toluene. 1H NMR (600 MHz, C6D6, 25 °C): δ = 2.20 [s, 3 H, C6H2(CH3)3], 2.04 [s, 6 H, C6H2(CH3)3] ppm. 13C{1H}
7.70 (s, 4 H, Mes-aryl-CH), 7.46–7.42 (m, 12 H, phenyl-CH), 7.19– NMR (151 MHz, C6D6, 25 °C): δ = 160.5 (Carom), 144.9 (Carom), 143.6
7.16 (m, 6 H, phenyl-CH), 7.16–7.14 (m, 12 H, phenyl-CH), 6.73 (s, (Carom), 142.3 (Carom), 142.3 (Carom), 140.8 (Carom), 139.4 (Carom),
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
137.2 (Carom), 136.6 (Carom), 135.6 (Carom), 132.4 (Carom), 131.0 aryl-CH), 7.66 (d, J = 8.3 Hz, 4 H, Anth-aryl-CH), 7.15–7.08 (m, 8
(Carom), 130.3 (Carom), 129.0 (Carom), 128.3 (Carom), 128.1 (Carom), H, Anth-aryl-CH), 6.97–6.95 (m, 4 H, pyrrole-CH and Mes-aryl-CH),
128.0 (Carom), 127.8 (Carom), 127.7 (Carom), 126.8 (Carom), 121.9 6.56 (d, J = 4.0 Hz, 2 H, pyrrole-CH), 3.23–3.21 (m, 4 H, THF-CH2),
(Carom), 21.2 (Caliph), 19.7 (Caliph) ppm. C66H50N2Zn (936.52 g·mol–1): 2.57 (s, 1 H, ZnH), 2.50 [s, 6 H, C6H2(CH3)3], 2.32 [s, 3 H,
calcd. C 84.65, H 5.38, N 2.99; found: C 85.11, H 5.68, N 3.33%.
C6H2(CH3)3], 1.16–1.14 (m, 4 H, THF-CH2) ppm. 13C{1H} NMR
(151 MHz, C6D6, 25 °C): δ = 160.2 (Carom), 147.0 (Carom), 140.9 (Ca-
rom), 137.7 (Carom), 137.1 (Carom), 136.1 (Carom), 132.1 (Carom), 131.7
(Carom), 131.6 (Carom), 130.7 (Carom), 128.7 (Carom), 128.1 (Carom),
128.0 (Carom), 127.0 (Carom), 126.1 (Carom), 125.2 (Carom), 122.3
(Carom), 67.9 (CTHF), 25.5 (CTHF), 21.4 (Caliph), 20.5 (Caliph) ppm.
C50H42N2OZn (752.28 g·mol–1): C 79.83, H 5.63, N 3.72%; found: C
79.84, H 5.75, N 3.39%.
Synthesis of (AnthDPM)ZnEt (2-Anth): In a 50 mL Schlenk flask
AnthDPM-H (503 mg, 0.818 mmol) was suspended in benzene (15 mL).
Neat Et2Zn (100 μL, 0.982 mmol, 1.2 equiv.) was added to the stirred
red suspension resulting in a pink solution. The reaction mixture was
heated to 60 °C overnight and the solvent was removed in vacuo yield-
ing a purple powder in quantitative yield. Recrystallization from tolu-
ene at –20 °C yielded red crystalline blocks. Yield: 521 mg
1
(0.736 mmol; 90%). H NMR (600 MHz, C6D6, 25 °C): δ = 8.11 (d,
Supporting Information (see footnote on the first page of this article):
Crystal structure data including ORTEP representations, selected 1D,
2D and DOSY NMR spectra.
J = 8.7 Hz, 4 H, Anth-aryl-CH), 8.07 (s, 2 H, Anth-aryl-CH), 7.69–
7.64 (m, 4 H, Anth-aryl-CH), 7.14–7.05 (m, 8 H, Anth-aryl-CH), 6.96
(d, J = 4.1 Hz, 2 H, pyrrole-CH), 6.96 (s, 2 H, Mes-aryl-CH), 6.56 (d,
J = 4.0 Hz, 2 H, pyrrole-CH), 5.88 [d, J = 4.1 Hz, 2 H, pyrrole-CH],
2.50 [s, 6 H, C6H2(CH3)3], 2.31 [s, 3 H, C6H2(CH3)3], –1.01 (t, J =
8.1 Hz, 3 H, ZnCH2CH3), –1.95 (q, J = 8.1 Hz, 2 H, ZnCH2CH3)
ppm. 13C{1H} NMR (151 MHz, C6D6, 25 °C): δ = 160.5 (Carom), 147.0 We greatly acknowledge Jochen Schmidt for NMR support and Chris-
(Carom), 141.0 (Carom), 137.8 (Carom), 137.1 (Carom), 135.8 (Carom), tina Wronna and Antigone Roth for numerous elemental analyses.
132.4 (Carom), 131.8 (Carom), 131.8 (Carom), 130.6 (Carom), 128.8
Acknowledgements
(Carom), 128.6 (Carom), 128.0 (Carom), 126.5 (Carom), 126.4 (Carom),
125.3 (Carom), 122.4 (Carom), 21.3 (Caliph), 20.6 (Caliph), 9.8 (Caliph),
–0.9 (Caliph) ppm. C48H38N2Zn (708.23 g·mol–1): calcd. C 81.40, H
Keywords: Hydride; Zinc; Dipyrromethene; B(C6F5)3
5.41, N 3.96; found: C 80.98, H 5.38, N 3.85%.
Synthesis of (AnthDPM)ZnOSiPh3 (5-Anth): In a 50 mL Schlenk
flask (AnthDPM)ZnEt (448 mg, 0.633 mmol) was dissolved in benzene
(20 mL). Neat Ph3SiOH (174 mg, 0.630 mmol, 1.0 equiv.) was added
at room temperature in one portion. The reaction mixture was heated
at 60 °C overnight. Residual solvent was removed in vacuo and the
crude product was triturated with n-hexane (2ϫ15 mL) to give a dark
purple solid. Yield: 479 mg (0.502 mmol; 79%). 1H NMR (600 MHz,
C6D6, 25 °C): δ = 8.37 (d, J = 8.8 Hz, 4 H, Anth-aryl-CH), 7.86 (s, 2
H, Anth-aryl-CH), 7.57 (d, J = 8.4 Hz, 4 H, Anth-aryl-CH), 7.27–7.20
(m, 4 H, Anth-aryl-CH), 7.16–7.12 (m, 6 H, phenyl-CH), 6.98 (t, J =
7.3 Hz, 3 H, phenyl-CH), 6.90 (s, 2 H, Mes-aryl-CH), 6.87 (d, J =
3.9 Hz, 2 H, pyrrole-CH), 6.68 (t, J = 7.4 Hz, 6 H, phenyl-CH), 6.57
(d, J = 4.0 Hz, 2 H, pyrrole-CH), 6.35 (d, J = 7.0 Hz, 6 H, Anth-aryl-
CH), 2.36 (s, 6 H, C6H2(CH3)3), 2.28 [s, 3 H, C6H2(CH3)3] ppm.
13C{1H} NMR (101 MHz, C6D6, 25 °C): δ = 160.0 (Carom), 146.2
(Carom), 141.9 (Carom), 140.3 (Carom), 137.9 (Carom), 137.1 (Carom),
135.6 (Carom), 134.6 (Carom), 133.0 (Carom), 131.8 (Carom), 131.4
(Carom), 129.7 (Carom), 128.8 (Carom), 128.0 (Carom), 127.8 (Carom),
127.2 (Carom), 126.9 (Carom), 125.7 (Carom), 125.2 (Carom), 123.9
(Carom), 21.3 (Caliph), 20.5 (Caliph) ppm. Several attempts to obtain sat-
isfactory elemental analytical data were without success. Although the
C, N and H values are outside the range viewed as establishing analyti-
cal purity, they are provided to illustrate the best values obtained to
date. C64H48N2OSiZn (954.27 g·mol–1): calcd. C 80.53, H 5.07, N
2.93; found: C 82.02, H 5.57, N 2.44%.
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1
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Z. Anorg. Allg. Chem. 2019, 1–11
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Z. Anorg. Allg. Chem. 2019, 1–11
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
G. Ballmann, J. Martin, J. Langer, C. Färber,
S. Harder* ....................................................................... 1–11
Low-Coordinate Monomeric Zinc Hydride Complexes with
Encapsulating Dipyrromethene Ligands and Reactivity with
B(C6F5)3
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