Structural diversity in sterically demanding diiminophosphinato alkali metal complexes

Article abstract of DOI:10.1002/ejic.201402924

We have prepared the new aminophosphine Ph₂PNHMes 2 [Mes = mesityl (2,4,6-Me₃C₆H₂)], and the aminoiminophosphorane Ph₂P(=NMes)NHMes 4 (^MesLH), and obtained the new alkali metal complexes [(

Full text of DOI:10.1002/ejic.201402924

FULL PAPER
DOI:10.1002/ejic.201402924
Structural Diversity in Sterically Demanding
Diiminophosphinato Alkali Metal Complexes
Andrew L. Hawley[a] and Andreas Stasch*[a]
Keywords: Alkali metals / Chelates / Phosphanes / Ligand design / Steric hindrance
We have prepared the new aminophosphine Ph2PNHMes 2
[Mes = mesityl (2,4,6-Me3C6H2)], and the aminoiminophos-
phorane Ph2P(=NMes)NHMes 4 (MesLH), and obtained the
new alkali metal complexes [(DipLLi)2] 5 [DipL = Ph2P(NDip)2,
[
DipLNa(THF)2] 13, [{MesLNa(THF)}2] 14 and [MesLK] 16 by
deprotonation of their respective ligand precursors with stan-
dard strong alkali metal bases in various solvents. The crystal
structures of 2, 4–6, 7·8, 9–14, and 16 are reported. The dif-
ferent coordination modes in their solid-state structures are
discussed and generally compared to the solution behavior
of those species.
Dip = 2,6-iPr2C6H3], [(MesLLi)2] 6, [(DipL)(DipN2L)Li2] 7 [DipN2
Ph2P(NDip)(N3Dip)], [(DipN2L)2Li2] 8, DipLLi(THF)] 9,
DipLLi(THF)2] 10, [(DipLNa)2] 11, [(MesLNa)n] 12,
L
=
[
[
materials for salt metathesis chemistry,[7] plus we antici-
pated a rich structural chemistry owing to their flexible
properties especially in complexes with electropositive met-
als.
Introduction
N,NЈ-Chelating and sterically demanding ligands such as
β-diketiminates,[1] amidinates, guanidinates and related sys-
tems,[2] as well as diazabutadien(edi)ides and similar spe-
cies[3] have been employed for a wide variety of metal com-
plexes and chemical applications. This includes the stabili-
zation of an impressive array of unusual low-oxidation-state
complexes.[4] Related iminophosphorane-based ligands that
feature fragments with the general formula R3P=NRЈ (R,
RЈ = alkyl, aryl, silyl, amido and so forth) form related
ligand systems of similar overall geometry, plus they have
the additional advantage of central 31P nuclei for facile 31P
NMR spectroscopic studies.[5] These ligands have, however,
been employed for low-oxidation-state chemistry to a far
lesser extent than CN-based systems.
Scheme 1. Diiminophosphinato metal(I) dimers of Mg and Zn (Dip
= 2,6-iPr2C6H3).
Results and Discussion
We have previously used a sterically demanding diimino-
phosphinate ligand for the stabilization of low-oxidation-
state metal complexes and reported metal–metal-bonded di-
meric metal(I) complexes of magnesium[6] and zinc[7] (see
Scheme 1). These studies have also revealed different prop-
erties of the diiminophosphinates relative to related ligands
with CN-based backbones. In addition, diiminophosphinate
complexes have been prepared with metals from all parts of
the periodic table and some sterically demanding ones have
successfully been employed in heteroleptic transition-
metal[8] or lanthanoid[9] complexes for alkene oligomeriza-
tions and polymerizations. Here we report on the synthesis
of a new diiminophosphinate ligand and a series of alkali
metal complexes that are of interest as convenient starting
Compound Syntheses
The predominantly employed strategies for obtaining di-
iminophosphinates with a central phosphorane (PV) centre
and related species follow two main routes: a Staudinger
pathway that uses an organic azide to oxidize a PIII com-
pound, and the Kirsanov route, which substitutes P–X
bonds (X = Cl, Br) in a PV compound by using amines to
generate PV–N compounds.[5] The PV species in the latter
route can be obtained by adding Cl2 or Br2 to a suitable
PIII precursor. We have previously used a Staudinger-based
synthesis to obtain the ligand used for the stabilization of
the metal(I) dimers [(DipLM)2] (M = Mg, Zn; Scheme 1).[6,7]
Treating chlorodiphenylphosphine with one equivalent of
the lithiated aniline ArNH2 [Ar = Dip (2,6-iPr2C6H3) or
Mes (mesityl, 2,4,6-Me3C6H2)] afforded the aminophos-
phines (phosphinoamines)[10] Ph2PNHAr (Ar = Dip 1 or
Mes 2) as previously reported for 1,[11] in good yield (see
[a] School of Chemistry, Monash University,
PO Box 23, Melbourne, Victoria 3800, Australia
E-mail: Andreas.Stasch@monash.edu
http://monash.edu/science/about/schools/chemistry/staff/stasch/
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Scheme 2). Further reaction of 1 or 2 in a Staudinger reac- the dimeric metal(I) compounds was only achieved using
tion[12] with ArN3 (Ar = Dip or Mes) afforded the amino- a specialized β-diketiminato magnesium(I) dimer[4a,4c] as a
iminophosphoranes Ph2P(=NAr)NHAr (Ar = Dip 3[7] or reducing agent.[6,7]
Mes 4, respectively).
Scheme 3. Metallation of 3 and 4 and the alkali metal complexes
5, 6 and 9–16: (a) nBuLi, n-hexane and/or THF; (b) [Na{N(Si-
Me3)2}], toluene or n-hexane/THF; and (c) [K{N(SiMe3)2}], tolu-
ene.
Scheme 2. Synthesis of 1–4 and mesomeric forms for diiminophos-
phinate ligands: (a) LiNHAr (Ar = Dip or Mes), Et2O; (b) ArN3,
toluene.
The formation of the phosphazide[14] complexes
Deprotonation of the aminoiminophosphoranes 3 and 4 [(DipL)(DipN2L)Li2] 7 and [(DipN2L)2Li2] 8 can be explained
can conveniently be achieved with standard organometallic by an incomplete N2 elimination in the Staudinger reaction
or metal amide bases in a range of hydrocarbon or ether leading to 3 (see Scheme 4). Gas evolution in the synthesis
solvents. A series of group 1 complexes of related diimino- of 3 (and 4) is already evident at very low temperatures, but
phosphinates have been reported in the literature and were very minor impurities can be found in some preparations
obtained by similar routes.[7,13]
of 3, as judged by 31P{1H} NMR spectroscopy,
Metallation to the alkali metal complexes of DipL and which caused the formation of [(DipL)(DipN2L)Li2] 7 and
MesL here can both be achieved in situ for direct further [(DipN2L)2Li2] 8. These minor impurities do not easily con-
reactions, or the resulting complexes can be isolated and vert to 3 upon standing at room temperature over pro-
stored under inert conditions; see Scheme 3 for a simplified longed time or at elevated temperatures, although they do
synthesis and isolated complexes, and see below for struc- appear to slowly diminish after prolonged time at elevated
tural studies. Lithiation of 3 and 4 in hexane with n-butyl- temperatures. The impurities are only evident by several
lithium afforded the dimeric homoleptic complexes very small 31P{1H} NMR resonances +/–0.5 ppm around
[(DipLLi)2] 5 and [(MesLLi)2] 6, respectively, which can be the base of the singlet at δ = –13.5 ppm in CDCl3 and the
isolated as colourless, crystalline solids. In some cases in the concentrations are too low to extract information from
synthesis of 5, later crops afforded small amounts of the co- 1H NMR spectroscopy of those samples of 3. The phos-
crystallized byproducts [(DipL)(DipN2L)Li2] 7 and [(DipN2L)2 phazide intermediate A (see Scheme 4), for which several
Li2] 8 in a 1:1 ratio. Separation of these latter two com- E/Z isomers can be considered, is believed to undergo facile
pounds so far failed, and only co-crystallized material 7·8 N2 elimination to 3 by means of a cyclic intermediate. This
was obtained. We further isolated the THF adducts N2 elimination, however, is likely hindered in the phospha-
[
DipLLi(THF)] 9 and [DipLLi(THF)2] 10 from lithiations in zide tautomers B and C. Tautomer C carries a hydrogen
n-hexane/THF mixtures or by THF addition to the homo- atom on the N2 fragment that is to be eliminated, and tau-
leptic species [(DipLLi)2] 5. Sodium and potassium com- tomer B likely requires H migration before a bond can form
plexes of DipL and MesL can conveniently be prepared by between the P atom and the N-Dip moiety. Several E/Z
treating the aminoiminophosphoranes 3 and 4 with [M{N- isomers for all tautomers have to be considered, and the
(SiMe3)2}] (M = Na, K) to afford the solvent-free homolep- equilibria that exist between them in solution can prevent a
tic sodium complexes [(DipLNa)2] 11 or [(MesLNa)n] 12, the suitable cis-type isomer[15] of A from forming in significant
latter of undetermined structure, as well as their isolated quantities and eliminating N2. The stability of the isomers
THF adducts [DipLNa(THF)2] 13 or [{MesLNa(THF)}2] 14 might depend on the steric bulk of the attached aryl substit-
after THF addition, or the respective potassium complexes uents, and it is worth mentioning that stable phosphazide
[
DipLK] 15 and [MesLK] 16, respectively; the former was de- products as precursors for 3 and 4 have so far only been
scribed previously by us.[7] It is also worth noting that alkali forthcoming for Dip compounds (i.e., the synthesis of 7·8)
metal complexes such as [(DipLNa)2] 11 and [DipLK] 15 in our laboratories and not for Mes derivatives. Despite
were obtained as the main products of reduction reactions their low concentrations in later crops of DipLH 3, all iso-
of [(DipLMX)2] complexes (M = Mg, Zn; X = halide) using mers A–C are expected to be deprotonated to the new li-
sodium or potassium metal when targeting the aforemen- gand DipN2L–, which is shown in its dominant mesomeric
tioned metal(I) dimers [(DipLM)2]. The success of isolating form in Scheme 4. The high solubility of DipLH 3 even in
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Scheme 4. Staudinger reaction, phosphazide tautomers A–C, and ligand DipN2L–.
aliphatic solvents such as n-hexane or n-pentane means that and related aminophosphines.[10] Two crystal structures for
recrystallizations have to be performed from concentrated the aminoiminophosphorane Ph2P(=NMes)NHMes 4 were
solutions, thereby potentially resulting in impure material, determined (Figure 1, compound 4Ј middle and 4ЈЈ right)
and that repeated recrystallizations lead to a significant loss that show similar bond lengths around the PV centre be-
in yield. In contrast, MesLH 4 shows a lower solubility in tween them, including one short P=N bond (ca. 1.55 Å)
hydrocarbon solvents, a higher tendency to crystallize and and a longer P–N single bond (average ca. 1.67 Å), and are
is readily isolated from the respective reaction mixture in comparable to one polymorph determined for
better yields than with 3. Prolonged heating of 7·8 (e.g., Ph2P(=NDip)NHDip 3.[7] The packing and orientation of
90 °C for one day in deuterated benzene) does not lead to the substituents around the tetrahedral P centre are dissimi-
any significant N2 elimination and formation of 5, though lar for the monoclinic (4Ј) and the triclinic (4ЈЈ) polymorph,
some minor changes to the heated mixture have been ob- which is also reflected in the significantly different N–P–N
served by NMR spectroscopy. This stability is likely caused angles (4Ј larger by 13°), C–P–C angles (4ЈЈ larger by 4°)
by the inability of the DipN2Li unit to form the required P– and a larger N···N separation for 4Ј by approximately 0.2 Å.
N contact in a four-membered ring transition state in the The differences in the geometries of 4Ј and 4ЈЈ cannot be
correct geometry,[15] as represented in Scheme 4, owing to expressed as simple explicit isomers, such as E/Z isomers.
The molecular structures of [(DipLLi)2]·C6H14 (5·C6H14)
coordination of the nitrogen atoms to the Li cations (see
below for the structure of 7·8).
and [(MesLLi)2]·C6H6 (6·C6H6) are shown in Figure 2. Ow-
ing to the different steric profiles of the ligands, the dimeric
units show different Li coordination between them. In
5·C6H14, the two Li positions are disordered and the minor
Structural Studies
Structural representations of the new compounds re- Li positions (not shown in Figure 2) adopt a very similar
ported in this paper are shown in Figures 1–8 and selected coordination geometry between the two diiminophos-
metrical parameters are summarized in Table 1, whilst crys- phinate ligands relative to the main Li positions. Li1 acts
tallographic data is given in Table 2. The overall molecular as a bridge between two N–C(Dip) bonds of different diim-
structure of Ph2PNHMes 2 (Figure 1, left), including metri- inophosphinate ligands and shows a short contact to one
cal parameters, resembles that of the Dip derivative 1[11] isopropyl group with a Li1···H(methine) interaction of ap-
Figure 1. Molecular structures of compound 2 (left), 4Ј (middle) and 4ЈЈ (right) (30% probability thermal ellipsoids). Hydrogen atoms
except for H1 are omitted for clarity.
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Table 1. Selected bond lengths [Å] and angles [°].
Compound
P–N
2
4 (4Ј)
4 (4ЈЈ)
5·C6H14
6·C6H6
7·8·C6H14
9
P1–N1 1.701(2) P1–N1 1.6768(10) P1–N1 1.6567(15)
P1–N2 1.5451(10) P1–N2 1.5460(11)
P1–N1 1.5961(14)
P1–N2 1.6116(14)
P2–N3 1.5901(14)
P2–N4 1.6109(15)
P1–N1 1.5870(12)
P1–N2 1.6146(12)
P1–N2 1.595(3)
P1–N1 1.617(3)
P2–N3 1.584(3)
P2–N4 1.664(3)
P3–N7 1.580(3)
P3–N8 1.661(3)
P4–N11 1.580(4)
P4–N12 1.645(4)
N1–Li2 1.970(6)
N1–Li1 2.339(6)
Li1–N2 1.927(6)
Li1–N6 2.061(6)
Li1–N4 2.182(6)
Li1–N5 2.537(6)
Li2–N3 1.938(6)
Li2–N4 2.209(6)
Li3–N7 1.959(7)
Li3–N14 2.059(7)
Li3–N12 2.117(7)
Li3–N8 2.226(7)
Li3–N13 2.524(7)
Li3–Li4 2.663(10)
Li4–N11 1.935(8)
Li4–N10 2.020(9)
Li4–N8 2.159(8)
Li4–N12 2.206(8)
Li4–N9 2.528(8)
–
P1–N1 1.5917(14)
P1–N2 1.5898(13)
P2–N4 1.5836(14)
P2–N3 1.6028(14)
M–N
–
–
–
N1–Li2A 1.925(9)
N1–Li1 1.933(5)
Li1–N4 1.950(5)
N2–Li1A 1.963(9)
N2–Li2 1.971(4)
N2–Li2A 2.423(9)
Li2–N3 1.943(4)
Li2–N4 2.406(5)
N3–Li1A 1.953(9)
N4–Li2A 1.963(9)
N1–Li1 1.967(3)
Li1–N4 1.998(3)
Li1–N2 2.073(3)
N2–Li2 2.002(3)
Li2–N3 1.951(3)
Li2–N4 2.119(3)
N1–Li1 1.968(3)
Li1–N2 1.962(3)
Li2–N3 1.970(3)
Li2–N4 2.010(3)
M–O
–
–
–
–
–
–
–
–
Li1–O1A 1.835(12)
(63% part)
Li1–O1 1.95(2)
(37% part)
O2–Li2 1.859(3)
M···C
Li1–C13 2.443(5)
Li contacts to ipso-C Li2–C13 2.585(7)
no short intra- or
intermolecular
Li···C contacts
found
Li1–C61 2.478(5)
(ipso-N4)
Li1–C62 2.478(5)
(ortho-N4)
Li1–C52 2.701(3)
Li2–C22 2.518(3)
Li1–C67 2.691(5)
(methine-N4, with
H67 contact: 2.070)
Li1A–C25 2.620(5)
(ipso-N2)
Li1A–C49 2.430(5)
(ipso-N3)
Li1A–C31 2.688(5)
(methine-N2, with
H31 contact: 2.015)
N1···N2 2.570
N···N/N–N
–
N1···N2 2.803
N1···N2 2.593
N1···N2 2.495
N1···N2 2.518
N4–N5 1.356(4)
N5–N6 1.278(4)
N8–N9 1.362(4)
N9–N10 1.264(4)
N12–N13 1.316(5)
N13–N14 1.231(5)
N1···N2 2.534
N1···N2 2.479
N3···N4 2.517
N3···N4 2.552
N3···N4 2.512
N4···N6 2.178
N7···N8 2.516
N8···N10 2.165
N11···N12 2.500
N12···N14 2.099
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Table 1. (Continued)
Compound
N–P–N
2
4 (4Ј)
4 (4ЈЈ)
5·C6H14
6·C6H6
7·8·C6H14
9
–
N2–P1–N1
120.87(5)
N2–P1–N1
108.09(6)
N1–P1–N2 106.49(7)
N1–P1–N2 102.37(6) N2–P1–N1
104.30(14)
N2–P1–N1
102.38(7)
N3–P2–N4 105.75(7)
N3–P2–N4 103.46(6) N3–P2–N4
101.31(13)
N4–P2–N3
104.38(7)
N7–P3–N8
101.83(15)
N11–P4–N12
101.76(18)
C–P–C
C7–P1–C1
101.30(10)
C1–P1–C7
108.19(5)
C7–P1–C1
103.55(6)
C7–P1–C1 101.72(7)
C7–P1–C1 103.53(7) C7–P1–C1
103.10(16)
C7–P1–C1
101.91(8)
C43–P2–C37 100.85(7) C37–P2–C31
101.92(6)
C43–P2–C37
104.65(15)
C47–P2–C41
100.69(7)
C79–P3–C73
106.11(17)
C115–P4–C109
102.4(2)
N–M–N
–
–
–
N1–Li1–N4 139.1(3)
N3–Li2–N2 139.6(3)
N1–Li1–N2
76.20(10)
N2–Li1–N1 72.2(2) N2–Li1–N1
78.20(12)
N3–Li2–N4 74.2(2) N3–Li2–N4
78.45(11)
N3–Li2–N4 70.96(15)
N2–Li2–N4 137.7(2)
N7–Li3–N8 73.6(2)
N11–Li4–N12
74.0(3)
N3–Li2–P1 135.2(2)
N3–Li1A–N2 139.5(5)
N1–Li2A–N4 138.7(5)
N1–Li2A–N2 71.4(3)
N4–Li2A–N2 137.1(5)
M···M
–
–
–
Li1···Li2 2.739
Li1A···Li2A 2.746
(65:35 parts for two
Li)
Li1···Li2 2.478(3)
Li1···Li2 2.607(8)
Li3··Li4 2.663(10)
–
proximately 2.07 Å. Related coordination of two Li cations of the steric influences of the involved Dip groups. The N–
between two sterically demanding ligands of similar overall N and P–N bond lengths in the DipN2L ligand suggest a
structure has been observed for amidinates and guanidin- dominant charge distribution as drawn for the ligand in
ates that bear N-Dip substituents.[16] Each Li cation in com- Scheme 4 with an N=N double bond.
plex 6·C6H6 coordinates to one diiminophosphinate in an
In the crystal structure of [DipLLi(THF)] 9, two indepen-
N,NЈ-chelating fashion whilst only coordinating to one ni- dent molecules are found; the THF ligands of both mol-
trogen centre of the second ligand and further results in ecules are disordered and only the main contributions are
relatively short Li···C(ipso-Dip) contacts (see Table 1). This shown in Figure 4. The first molecule (9Ј; Figure 4, left)
yields a folded cis-ladder motif of three fused four-mem- shows a distorted three-coordinate Li centre that is N,NЈ-
bered rings with a central N2Li2 diamond at its base.
chelated to the diiminophosphinate ligand and shows coor-
The byproduct [(DipL)(DipN2L)Li2]·[(DipN2L)2Li2]·C6H14 dination to one disordered terminal THF molecule with a
(7·8·C6H14) shows the full independent molecules P1···Li1–O1/O1A angle of approximately 160–167°. In the
[(DipL)(DipN2L)Li2] 7 and [(DipN2L)2Li2] 8 in the asymmetric second molecule (9ЈЈ; Figure 4, middle), the THF ligand is
unit (see Figure 3). In 7, Li1 is N,NЈ-chelated by the diim- significantly displaced from both the least-squares NPNLi
inophosphinate of P1 and N,NЈ-chelated by the phospha- plane and a plane orthogonal to that bisecting the P···Li
zido N3 chain of the DipN2L ligand of P2. Li2 is coordinated vector, which results in a very distorted three-coordinate Li
in a similar fashion to the Li cations in 6 as it is N,NЈ- environment with a P2···Li2–O2 angle of 141.3°. This is
chelated by the DipN2L ligand of P2 and only coordinated likely caused by packing effects and two molecules of 9ЈЈ
to N1 of the DipL ligand, plus it has a relatively short are arranged in a dimeric aggregate although they show no
Li···C(ipso-Dip) contact. In [(DipN2L)2Li2] 8, each Li centre significant intermolecular contacts between them. The crys-
is bridged between the two DipN2L ligands by being N,NЈ- tal structure of [DipLLi(THF)2] 10 (Figure 4, right) re-
chelated to an NPN fragment and N,NЈ-chelated to the N3 sembles a typical four-coordinate structural type with an
chain of the second ligand.[17] The four-coordinate Li envi- N,NЈ-chelating diiminophosphinate, as has been found for
ronments are not in a distorted tetrahedral geometry but most previously described related diiminophosphinato lith-
rather tend towards planar coordination, likely on account ium complexes.[13] The Li–N bonds in 10 are, as expected,
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Table 1. (continued).
Compound 10
11·4C6H6
11
13
14·0.5C6H6
16 (16Ј)
16 (16ЈЈ)
P–N
P1–N1
P1–N1 1.5875(12) P1–N1 1.593(3) P1–N1 1.584(3)
P1–N1 1.5872(18)
P1–N1 1.5775(14)
P1–N1 1.5735(14)
1.5836(12)
P1–N2
P1–N2 1.5923(12) P1–N2 1.590(3) P1–N2 1.579(3)
P1–N2 1.5978(18)
P1–N2 1.5982(14)
P1–N2 1.5945(15)
1.5955(12)
P2–N3 1.5997(17)
P2–N4 1.6077(17)
M–N
N1–Li1 2.089(3) Na1–N1
2.4837(13)
Li1–N2 2.039(3) Na1–N2
2.3308(13)
Na1–N1
2.455(4)
Na1–N2
2.292(4)
Na1–N1 2.362(3),
Na1–N2 2.423(4)
Na1–N2Ј 2.3272(19) K1–N1 2.7348(14)
K1–N1 2.7171(17)
Na1–N1 2.3456(19) K1–N2Ј 2.7211(13) K1–N2Ј 2.7197(15)
Na2–N3 2.331(2)
Na2–N4Ј 2.4047(19)
Na2–N4 2.684(2)
N2–Na1Ј 2.3272(19)
N4–Na2Ј 2.4047(19)
M–O
O1–Li1 1.975(3)
Li1–O2 1.976(3)
–
–
Na1–O1 2.256(4)
Na1–O2 2.259(7)
Na1–O2A 2.528(11)
–
Na1–O1 2.273(2)
Na2–O2 2.3029(19)
–
–
M···C
–
Na1–C17Ј
2.8657(17)
Na1–C16Ј
2.8770(17)
Na1–C15Ј
2.8901(17)
Na1–C15Ј
2.756(5)
Na1–C16Ј
2.780(5)
Na1–C14Ј
2.817(5)
Na1–C13 2.887(2)
K1–C13(ipso-N1)
3.041
K1–C18(ortho-N1) K1–C18(ortho-
K1–C13(ipso-N1)
3.136
C21–Na1Ј 2.980(4)
3.343
(methyl group, short- K1–C21(methyl-
est contact H21C,
2.489; H21B 2.618)
C22–Na1Ј 2.994(2)
N1) 3.374
K1–C21(methyl-
N1) 3.473
N1) 3.616
Na1–C18Ј
2.9094(15)
Na1–C14Ј
2.9132(15)
Na1–C13Ј
2.9176(15)
Na1···Ccentroid
2.534
Na1–C17Ј
2.877(5)
Na1–C13Ј
2.879(4)
Na1–C18Ј
2.943(5)
Na1···Ccentroid
2.474
(shortest H21B
2.987)
K1–C22(ipso-N2)
3.468
(shortest H21B
2.774)
K1–C22(ipso-N2)
3.384
Na2–C56Ј 2.819(2)
Na2–C62 2.878(8)
3.100
(methyl group, short- K1–C24(meta-N2)
est contact H62C,
2.379; H62B 2.546)
K1–C23(ortho-N2) K1–C23(ortho-
N2) 3.132
K1–C24(meta-N2)
3.228
3.221
K1–C22(ipso-N2Ј)
K1–C22(ipso-N2Ј)
3.428
3.518
N···N/N–N N1···N2 2.510
N1···N2 2.541
N1···N2 2.542
N1···N2 2.566
N1···N2 2.697
N1···N2 2.609
N1···N2 2.710
N1···N2 2.691
N–P–N
N1–P1–N2
104.26(6)
N1–P1–N2
106.08(6)
N2–P1–N1
106.00(18)
N2–P1–N1 108.42(18) N1–P1–N2 115.72(9) N1–P1–N2
N1–P1–N2
116.33(8)
117.15(7)
N3–P2–N4 108.86(9)
C–P–C
C7–P1–C1
100.05(6)
C7–P1–C1
101.25(7)
C7–P1–C1
101.91(19)
C7–P1–C1 100.28(17) C1–P1–C7 102.28(9) C7–P1–C1
C7–P1–C1
101.42(8)
101.04(7)
C35–P2–C41
103.55(9)
N–M–N
N2–Li1–N1
74.88(10)
N2–Na1–N1
63.61(4)
N2–Na1–N1
64.66(12)
N1–Na1–N2 64.84(12) N(2Ј)1–Na1–N1
N(2Ј)1-K1–N1
115.43(4)
N1–K1–N(2Ј)1
110.19(5)
140.03(7)
N3–Na2–N(4Ј)2
150.75(7)
M···M
–
Na1···Na1Ј 4.307 Na1···Na1Ј
–
Na1···Na1Ј 3.894
–
–
4.061(4)
Na2···Na2Ј 3.238
longer than those of molecules of 9 owing to the higher geometries in both molecules are essentially identical and
coordination sphere of the Li ion in 10.
only slight differences in the Na···arene coordination have
Two similar crystal structures of [(DipLNa)2] 11 been found, plus a difference in the Na···Na separation by
(11·4C6H6, and 11) were obtained (Figure 5) and both con- approximately 0.25 Å.
tain half a dimeric molecule in the asymmetric unit. The
The THF adduct [DipLNa(THF)2] 13 (Figure 6) shows
Na ions are N,NЈ-chelated in a slightly asymmetric fashion the same overall molecular structure to [DipLLi(THF)2] 10
[the Na–N bond lengths differ by ca. 0.16 Å (mean) in each with an N,NЈ-chelating diiminophosphinate and parts of
molecule] and the molecule dimerizes by means of an ap- the molecule are only poorly ordered.
proximate Na···η6-Dip–arene interaction,[18] with a mean
The molecular structure of the THF adduct
Na···centroid distance of 2.50 Å, to the second ligand. The [{MesLNa(THF)}2]·0.5C6H6 (14·0.5C6H6) comprises two in-
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Figure 2. Molecular structure of complexes 5·C6H14 (left) and 6·C6H6 (right) (30% probability thermal ellipsoids). Only the main Li
positions in 5·C6H14 are shown (65% part). Hydrogen atoms and solvent molecules are omitted for clarity.
Figure 3. Molecular structure of compound 7·8·C6H14: 7 (left) and 8 (right) (30% probability thermal ellipsoids). Hydrogen atoms and
solvent molecules are omitted for clarity.
dependent half molecules in the asymmetric unit with dif- ecules carries a terminal THF ligand and shows one short
ferent Na-diiminophosphinate coordination modes. In 14Ј contact to one ortho-methyl group from a mesityl group. In
(Figure 7, left), the diiminophosphinate bridges the two Na 14Ј, this interaction is formed by means of the mesityl
ions in a 1κN,2κNЈ-mode, whereas in the other molecule group bound to the nitrogen atom not directly bound to
(14ЈЈ; Figure 7, right) the diiminophosphinate both chelates the Na centre in question, and in 14ЈЈ, it is the mesityl
one Na ion and bridges the second Na centre in a group bound to the nitrogen atom with the longer Na···N
1κN;1:2κNЈ mode. In addition, each Na ion in both mol- chelation contact. This coordination could also be regarded
Figure 4. Molecular structure of two independent molecules of 9 (9Ј, left; 9ЈЈ, middle) and 10 (right) (30% probability thermal ellipsoids).
Only the main THF contributions are shown for the disordered THF ligands. Hydrogen atoms have been omitted for clarity.
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Figure 5. Molecular structure of compound 11·4C6H6 (left) and 11 (right) (30% probability thermal ellipsoids) in two different views.
Hydrogen atoms and solvent molecules have been omitted for clarity.
similar overall structure to that found for 14ЈЈ had been
identified for a rubidium complex.[13f]
The crystal structures of two related polymorphs of
[
MesLK] 16 have been determined; these show a very similar
overall geometry and metrical parameters between them
(see Table 2). Polymorphs 16Ј and 16ЈЈ (Figure 8) crys-
tallized in the monoclinic and triclinic crystal systems,
respectively. Both polymorphs form one-dimensional poly-
meric chains, mainly through 1κN,2κNЈ interactions plus
various short K···arene interactions[18] in the solid state.
For comparison, the molecular structure of [DipLK] 15
has previously been described.[7] Complex 15 also forms
one-dimensional chains in the solid state as determined for
16, though the coordination in the former and sterically
more demanding complex is exclusively achieved by means
of K···arene interactions (see Figure 9) with no K···N con-
tacts.
Figure 6. Molecular structure of [DipLNa(THF)2] 13 (30% prob-
ability thermal ellipsoids). Only the main part of the disordered
THF molecule on O2 is shown. Hydrogen atoms are omitted for
clarity.
Across the investigated alkali metal complexes, the diim-
inophosphinates DipL– and MesL– show a large range of pos-
as an N,CH3-chelation in 14Ј, and an N,NЈ,CH3-chelation sible N···N separations and are able to accommodate metal
in 14ЈЈ. Several different structure modes for diiminophos- ions with a range of ionic radii. The N···N separation ran-
phinato alkali metal complexes that bear N-bound trimeth- ges from approximately 2.48 Å in the Li complex 9 up to
ylsilyl groups and additional THF ligands have previously approximately 2.71 Å in the potassium complex 16 and ap-
been described that show a wide variety of geometries. A proximately 2.79 Å as previously found for 15;[7] and they
Figure 7. Two independent molecules in the molecular structure of 14·0.5C6H6; molecule 14Ј (left) and molecule 14ЈЈ (right) (30% prob-
ability thermal ellipsoids). Hydrogen atoms and solvent molecules have been omitted for clarity.
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pling constants, which disappear in a 31P-decoupled 1H
7
NMR spectrum as found for 12. The JP,H couplings are
slightly larger than 5JP,H ones and comparable to those pre-
viously found for some aromatic phosphorus com-
pounds.[20] The lithium complexes [(DipLLi)2] 5, [(MesLLi)2]
6 and [DipLLi(THF)] 9 show a singlet in their respective
31P{1H} NMR spectra at around δ = –3 to –8 ppm, and
7
a singlet or dominating singlet in their Li NMR spectra.
Dissolved isolated crystals of [DipLLi(THF)2] 10 in deuter-
ated benzene, however, show somewhat resolved 31P–7Li
coupling at room temperature with a broadened doublet (J
= 7.2 Hz) in its 7Li NMR spectrum and an unresolved mul-
tiplet in its 31P{1H} NMR spectrum.
Conclusion
We have presented the synthesis of the new aminophos-
phine Ph2PNHMes 2, aminoiminophosphorane MesLH 4
and a series of Li, Na and K complexes of the diiminophos-
phinates DipL– and MesL–. Structural studies show that
N,NЈ-chelation is the dominant structural feature, but vari-
ous bridging coordination modes and additional interac-
tions have been observed and include C–H···M and
arene···M contacts; these resulted in a variety of different
overall structures and some polymorphism. Ligands DipL–
and MesL show a wide range of N···N separations in the
characterized complexes that help accommodate metal ions
of various sizes. This study provides further evidence that
the tetrahedral PV centres behave in a more flexible manner
than related CN-based ligand backbones. The structural di-
versity in the characterized complexes and their symmetric
solution behaviour suggests that very small energetic
changes are required for their interconversion, and some of
the crystal structures can be considered snapshots of solu-
tion behaviour.
Figure 8. Excerpts of the 1D polymers of two polymorphs of
[
MesLK] 16: 16Ј (top) and 16ЈЈ (bottom) (30% probability thermal
ellipsoids). Hydrogen atoms have been omitted for clarity.
Figure 9. The polymeric chain of [DipLK] 15.
can be as short as approximately 2.44 Å as found for DipL
complexes of divalent Zn.[7] Even shorter respective dis-
tances have been found for other diiminophosphinate li-
gands with small transition-metal ions (approximately
down to 2.37–2.38 Å).[19]
Despite their different geometries in the solid state, the
solution structures of the alkali metal complexes of DipL
and MesL are highly symmetric on the NMR spectroscopic
timescale owing to low energy barriers for these ionic com-
plexes. This is observed for complexes in neat deuterated
benzene, with the addition of various amounts of THF or
as dissolved THF solvates. As an example, only one doublet
and one septet are found for the isopropyl resonances in
DipL complexes plus the corresponding 13C{1H} NMR
Experimental Section
General Considerations: All manipulations were carried out using
standard Schlenk and glovebox techniques under an atmosphere
of high-purity dinitrogen. Benzene, toluene, tetrahydrofuran and
hexane were dried and distilled from molten potassium, and Et2O
was dried and distilled from Na/K alloy. 1H, 7Li, 7Li{1H}, 13C{1H}
and 31P{1H} NMR spectra were recorded with a Bruker DPX 300
or Bruker Avance 400 spectrometer in deuterated benzene and were
referenced to the residual 1H or 13C{1H} resonances of the solvent
spectroscopic resonances, and a comparable number of res- used, or external aqueous LiCl or H3PO4 solutions, respectively. IR
onances for the related MesL complexes. This is in line with
spectra were recorded with a Perkin–Elmer RXI FTIR spectrome-
ter as Nujol mulls between NaCl plates or on neat solids (or pro-
tected with a thin layer of nujol) with an Agilent Cary 630 ATR
FTIR spectrometer. Melting points were determined in sealed glass
capillaries under dinitrogen and are uncorrected. Elemental analy-
ses were performed by the Elemental Analysis Service at London
Metropolitan University or by the Microanalytical Laboratory at
low-temperature studies on the highly soluble heteroleptic
[
DipLZnEt] complex,[7] which starts showing resonance
splitting only below –70 °C. In contrast, the aminoimino-
phosphorane Ph2P(=NMes)NHMes 4 shows, like its Dip
congener 3,[7] two sets of resonances for the two different
7
5
N-aryl substituents. Small JP,H and JP,H couplings were
the Department of Chemistry, University of Otago. The com-
resolved in the H NMR spectra for some MesL complexes
1
[21]
pounds Ph2P(=NDip)NHDip, DipLH 3[7] and MesN3
were re-
and show a splitting of para- and ortho-mesityl methyl pro-
ported previously. All other reagents were used as received from
tons through long-range P–H-couplings with small cou- commercial sources.
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Ph2PNHMes (2): n-Butyllithium (43.0 mL of a 1.62 m solution in
hexanes, 69.7 mmol) was slowly added to a solution of freshly dis-
tilled MesNH2 (10.0 mL, 9.62 g, 69.1 mmol) in diethyl ether
(60 mL) at –80 °C. The mixture was stirred for one hour with slow
warming to room temperature. The resulting white suspension was
cooled to –80 °C and a solution of Ph2PCl (12.0 mL, 14.7 g,
67.1 mmol) in Et2O (60 mL) was slowly added, then the mixture
was stirred overnight with slow warming to room temperature. The
mixture was filtered, the residue extracted again with diethyl ether
(50 mL), then the combined solution was concentrated under re-
duced pressure to approximately 90 mL and cooled to –30 °C to
afford a first crop of crystalline MesNHPPh2 2. Concentration of
the supernatant solution to approximately 40 mL and cooling to
–30 °C afforded a second crop of crystals. A third crop was ob-
tained after further concentration (to ca. 25 mL) and cooling. The
isolated solids were dried under vacuum, yield 15.0 g (70%); m.p.
96–100 °C (melts), decomposes at approximately 300 °C. C21H22NP
(319.39): calcd. C 78.97, H 6.94, N 4.39; found C 78.47, H 6.80, N
4.22. 1H NMR (C6D6, 300.1 MHz, 303 K): δ = 2.09 (s, 6 H, o-
CH3), 2.14 (s, 3 H, p-CH3), 3.55 (d, JP,H = 8.4 Hz, 1 H, NH), 6.74
(s, 2 H, m-ArH), 7.03–7.17 (m, 6 H, ArH), 7.42–7.53 ppm (m, 4 H,
ArH). 13C{1H} NMR (C6D6, 100.6 MHz, 300 K): δ = 19.1 (d, JP,C
= 6.1 Hz, o-CH3), 20.6 (p-CH3), 128.6 (d, JP,C = 6.3 Hz, Ar–C),
128.8 (Ar–C), 129.7 (d, JP,C = 1.2 Hz, ArC), 130.8 (d, JP,C = 3.5 Hz,
Ar–C), 131.5 (Ar–C), 131.7 (Ar–C), 140.7 (d, JP,C = 14.2 Hz, Ar–
C), 143.1 ppm (d, JP,C = 15.7 Hz, Ar–C). 31P{1H} NMR (C6D6,
for 30 min at room temperature and concentrated to approximately
3 mL to afford colourless crystalline [(DipLLi)2] 5. Storage of the
supernatant solution at 4 °C afforded a second crop. The isolated
material was dried under vacuum. Crystals of [(DipLLi)2]·C6H14,
5·C6H14, were obtained from a concentrated solution in n-hexane
at room temperature. A small crop of crystals of [(DipL)(DipN2L)-
Li2]·[(DipN2L)2Li2]·C6H14, 7·8·C6H14, was obtained from n-hexane
at 4 °C, from a late crop using DipLH 3 with some contamination
of DipN2LH present.
Data for [(DipLLi)2] (5): Yield 0.31 g (61%); it became slowly softer
above approximately 110 °C, slowly turning light brown above
130 °C, and brown at approximately 250 °C. 1H NMR (C6D6,
300.1 MHz, 303 K): δ = 0.96 [d, J = 6.8 Hz, 48 H, CH(CH3)2], 3.58
[sept, J = 6.8 Hz, 8 H, CH(CH3)2], 6.77–7.42 (m, 32 H, Ar–H)
ppm. 7Li NMR (C6D6, 155.5 MHz, 300 K): δ = –0.8 ppm (s).
13C{1H} NMR (C6D6, 75.5 MHz, 303 K): δ = 24.7 [CH(CH3)2],
29.1 [CH(CH3)2], 121.5 (d, JP,C = 3.0 Hz, Ar–C), 124.0 (d, JP,C
2.2 Hz, Ar–C), 127.8 (d, JP,C = 11.0 Hz, Ar–C), 129.9 (d, JP,C
2.6 Hz, Ar–C), 132.0 (d, JP,C = 8.0 Hz, Ar–C), 140.3 (d, JP,C
=
=
=
94.3 Hz, Ar–C), 145.0 (d, JP,C = 6.0 Hz, Ar–C), 145.6 (Ar–C) ppm.
31P{1H} NMR (C6D6, 121.5 MHz, 303 K): δ = –6.7 (s) ppm. IR
(nujol): ν = 1588 (w), 1460 (s), 1435 (s), 1377 (s), 1360 (m), 1350
˜
(m), 1331 (m), 1256 (m), 1191 (m), 1113 (s), 1046 (m), 1010 (m),
789 (m), 780 (m), 750 (m), 722 (m), 710 (m), 696 (s) cm–1.
Data for [(DipL)(DipN2L)Li2]·[(DipN2L)2Li2] (7·8): 1H NMR (C6D6,
300.1 MHz, 303 K): δ = 0.50 [d, J = 6.8 Hz, 6 H, CH(CH3)2], 0.76–
1.38 [m of overlapping d, 90 H, CH(CH3)2; overlapping sharp d
from 0.85–1.05; overlapping br. d from 1.06–1.38], 2.95 [sept, J =
6.8 Hz, 2 H, CH(CH3)2], 3.16 [sept, J = 6.8 Hz, 2 H, CH(CH3)2],
3.38–3.84 [m of overlapping sept, J = 6.8 Hz, 12 H, CH(CH3)2;
overlapping sharp sept from 3.38–3.62; overlapping br. sept from
3.56–3.84], 6.91–7.20 (m, 48 H, Ar–H), 7.50–7.70 (m, 16 H, Ar–H)
ppm. 31P{1H} NMR (C6D6, 121.5 MHz, 303 K): δ = 4.1, 19.4, 24.0
121.5 MHz, 303 K): δ = 34.7 (s) ppm. IR (solid, ATR): ν = 3271
˜
(br. m, NH) , 2910 (m), 2853 (m), 1478 (s), 1430 (s), 1363 (m), 1304
(w), 1245 (m), 1218 (s), 1156 (m), 1090 (m), 1066 (m), 1026 (m),
873 (m), 851 (s), 737 (s), 714 (m), 692 (s) cm–1.
Ph2P(=NMes)(NHMes) [MesLH (4)]: A slurry of Ph2PNHMes 2
(8.07 g, 25.3 mmol, 1.0 equiv.) in toluene (20 mL) was transferred
with a wide cannula to a solution of cooled (–80 °C) mesitylazide
(ca. 5.36 g, 33.3 mmol, 1.3 equiv.) in toluene (30 mL). The mixture
was stirred overnight while slowly warming to room temperature
with evolution of nitrogen gas. The mixture was stirred for one
hour at 60 °C, after which all volatiles were removed under reduced
pressure. The solid was recrystallized from hot (ca. 60 °C) n-hexane
(ca. 100 mL) to yield a white crystalline solid, MesLH 4. The super-
natant solution was concentrated to approximately 50 mL and
cooled to 4 °C to afford a second crop of crystals. Further fil-
tration, concentration and cooling to 4 °C yielded a third crop. The
combined solid was dried under vacuum, yield 12.4 g (92%); m.p.
194–195 °C (melts). C30H33N2P (452.58): calcd. C 79.62, H 7.35, N
(3s) ppm. IR (nujol): ν = 1588 (w), 1464 (s), 1435 (s), 1377 (s), 1360
˜
(m), 1331 (m), 1254 (m), 1199 (m), 1115 (s), 1098 (m), 1049 (m),
1012 (m), 997 (m), 778 (m), 764 (m), 758 (m), 745 (m), 720 (m),
710 (m), 694 (s) cm–1.
[(MesLLi)2] (6): A solution of n-butyllithium (2.0 mL of a 1.6 m
solution in hexanes, 1.11 equiv.) was added to a cooled (–70 °C)
solution MesLH 4 (1.31 g, 2.89 mmol, 1.0 equiv.) in toluene (30 mL)
and stirred overnight whilst allowing slow warming to room tem-
perature. The mixture was filtered, and the residual solid was dried
under vacuum. The supernatant solution was concentrated to
20 mL under reduced pressure before being cooled to –30 °C to
yield a second crop of crystalline solid. Further concentration to
approximately 8 mL and cooling afforded a third crop. Isolated
crops were dried under vacuum (yield 75%). Crystals of [(MesLLi)
2]·C6H6 (6·C6H6) were obtained by cooling a saturated solution in
benzene from 60 °C to room temperature. The 13C{1H} NMR spec-
troscopic data is given at 60 °C owing to the improved solubility.
The 1H NMR spectra at room temperature and 60 °C are essen-
tially identical, yield 1.00 g (75%); m.p. 130–132 °C (melts), de-
comp. Ͼ 310°. C60H64Li2N4P2 (917.02): calcd. C 78.59, H 7.03, N
1
6.19; found C 78.95, H 7.24, N 5.99. H NMR (C6D6, 400.2 MHz,
300 K): δ = 2.04 (s, 3 H, CH3), 2.11 (s, 12 H, CH3), 2.24 (s, 3 H,
CH3), 3.97 (br. d, JP,H ≈ 4 Hz, 1 H, NH), 6.62 (s, 2 H, m-ArH),
6.89 (s, 2 H, m-ArH), 6.95–7.06 (m, 6 H, ArH), 7.74–7.82 (m, 4 H,
ArH) ppm. 13C{1H} NMR (C6D6, 75.5 MHz, 303 K): δ = 20.6
(CH3), 20.8 (CH3), 21.0 (CH3), 21.3 (CH3), 127.1 (br., ArC), 128.2
(d, JP,C = 12.9 Hz, ArC), 129.1 (ArC), 129.7 (ArC), 131.0 (d, JP,C
= 2.8 Hz, ArC), 131.2 (br. d, JP,C ≈ 7.4 Hz, ArC), 132.2 (d, JP,C
=
9.5 Hz, ArC), 134.7 (ArC), 135.3 (ArC), 135.8 (ArC), 135.9 (d, JP,C
= 126.6 Hz, ArC), 144.5 (ArC) ppm. 31P{1H} NMR (C6D6,
121.5 MHz, 303 K): δ = –16.7 (s) ppm. IR (solid, ATR): ν = 3339
˜
1
6.11; found C 78.04, H 6.93, N 5.88. H NMR (C6D6, 300.1 MHz,
(m, NH) , 2918 (s), 2853 (s), 1478 (s), 1458 (m), 1449 (m), 1435 (s),
1375 (s), 1370 (s), 1340 (m), 1308 (m), 1290 (m), 1214 (s), 1150 (m),
1111 (s), 1057 (m), 1028 (m), 883 (m), 860 (m), 853 (s), 784 (m),
751 (s), 735 (m), 720 (m), 709 (m), 697 (s) cm–1.
Synthesis of [(DipLLi)2] (5) and [(DipL)(DipN2L)Li2]·[(DipN2L)2Li2]
(7·8): n-Butyllithium (0.64 mL of a 1.6 m solution in hexanes,
1.02 mmol) was slowly added to a solution of DipLH 3 (0.50 g,
0.932 mmol) in n-hexane (6 mL) at –20 °C. The mixture was stirred
303 K): δ = 2.07 (s, 24 H, o-CH3), 2.17 (d, JP,H = 2.1 Hz, 12 H, p-
CH3), 6.85 (s, 8 H, m-ArH), 6.85–7.15 (m, 12 H, ArH), 7.60–
7.69 ppm (m, 8 H, ArH). 7Li{1H} NMR (C6D6, 155.5 MHz,
300 K): δ = 2.9 (s and m) ppm. 13C{1H} NMR (C6D6, 75.5 MHz,
333 K): δ = 20.7 (d, JP,C = 0.8 Hz, CH3), 21.5 (CH3), 127.8 (ArC,
partially hidden by solvent resonance), 130.2 (d, JP,C = 1.8 Hz,
ArC), 131.5 (d, JP,C = 8.6 Hz, ArC), 134.2 (d, JP,C = 6.0 Hz, ArC),
139.9 (br. d, JP,C = 95.5 Hz, ArC), 144.5 (br., ArC) ppm. Two
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13C{1H} NMR spectroscopic resonances are missing despite a long
acquisition time and are either hidden underneath the strong sol-
vent signal or broadened into the baseline. 31P{1H} NMR (C6D6,
8 H, Ar–H), 7.37–7.48 (m, 8 H, Ar–H) ppm. 13C{1H} NMR (C6D6,
75.5 MHz, 338 K): δ = 24.2 [CH(CH3)], 28.5 [CH(CH3)], 120.0 (d,
JP,C = 2.9 Hz, ArC), 123.6 (d, JP,C = 2.0 Hz, ArC), 127.4 (d, JP,C
=
=
=
121.5 MHz, 303 K): δ = –3.0 (s) ppm. IR (solid, ATR): ν = 2919 10.9 Hz, ArC), 129.0 (d, JP,C = 2.6 Hz, ArC), 131.5 (d, JP,C
˜
(s), 2852 (s), 1474 (s), 1458 (m), 1448 (m), 1435 (s), 1370 (s), 1329
7.9 Hz, ArC), 141.3 (d, JP,C = 97.6 Hz, ArC), 144.4 (d, JP,C
(m), 1306 (m), 1285 (m), 1214 (s), 1151 (m), 1111 (s), 1058 (m), 6.0 Hz, ArC), 147.3 (d, coupling not resolved, ArC) ppm. 31P{1H}
1021 (m), 997 (m), 880 (m), 859 (m), 853 (s), 751 (m), 735 (m), 720 NMR (C6D6, 121.5 MHz, 298 K): δ = –14.6 (s) ppm. 31P{1H}
(m), 697 (s) cm–1.
NMR (C D , 121.5 MHz, 338 K): δ = –14.2 (s) ppm. IR (nujol): ν
˜
6 6
= 1586 (w), 1461 (s), 1377 (s), 1367 (s), 1327 (m), 1324 (s), 1273
(m), 1215 (m), 1112 (m), 1097 (m), 1050 (m), 1014 (m), 989 (m),
933 (m), 775 (m), 744 (m), 699 (m) cm–1.
Synthesis of [DipLLi(THF)] (9) and [DipLLi(THF)2] (10): Crops of
crystalline 9 and 10 were obtained by recrystallizing small quanti-
ties of [(DipLLi)2] 5 from n-hexane either with a few drops of THF
(9) or from an n-hexane/THF (ca. 8:1) mixture (10) at 4 °C. NMR
spectra of isolated colourless crystals of 9 and 10 are very similar
except for different THF-proton integration and 7Li/31P NMR
spectroscopic multiplicities.
[
MesLNa] (12) and [{MesLNa(THF)}2] (14): Toluene (30 mL) was
added to a mixture of MesLH 4 (0.97 g, 2.14 mmol, 1.0 equiv.) and
[Na{N(SiMe3)2}] (0.45 g, 2.46 mmol, 1.15 equiv.) at 0 °C and vig-
orously stirred overnight with gradual warming to room tempera-
ture. The formed precipitate was removed by filtration, washed
with n-hexane (15 mL) and dried under vacuum to afford 12 of a
yet undetermined structure (yield 71%). Compound 12 was only
poorly soluble in noncoordinating solvents and thus a few drops
of THF were added to acquire solution NMR spectroscopic data,
yield 0.72 g (71%); m.p. 313–317 °C (melts). C30H32N2NaP
(474.56): calcd. C 75.93, H 6.80, N 5.90; found C 75.78, H 6.68, N
5.79. 1H NMR [C6D6/THF (ca. 30:1, THF resonances are not
given), 300.1 MHz, 298 K]: δ = 2.24 (d, JP,H = 1.8 Hz, 24 H, o-
CH3), 2.29 (d, JP,H = 0.9 Hz, 12 H, p-CH3), 6.88 (s, 8 H, m-ArH),
7.02–7.16 (m, 12 H, ArH), 7.80–7.89 (m, 8 H, ArH) ppm. 13C{1H}
NMR [C6D6/THF (ca. 30:1, THF resonances are not given),
75.5 MHz, 298 K]: δ = 20.9 (d, JP,C = 1.2 Hz, CH3), 21.8 (d, JP,C
= 0.9 Hz, CH3), 126.3 (vbr., ArC), 127.3 (d, JP,C = 11.0 Hz, ArC),
1
Data for [DipLLi(THF)] (9): H NMR (C6D6, 400.2 MHz, 294 K):
δ = 1.03 (mc, 4 H, THF–CH2), 1.06 [d, J = 6.8 Hz, 24 H,
CH(CH3)2], 3.24 (mc, 4 H, THF–OCH2), 3.84 [sept, J = 6.8 Hz, 4
H, CH(CH3)2], 6.91–7.23 (m, 12 H, Ar–H), 7.51–7.57 (m, 4 H, Ar–
H) ppm. 7Li NMR (C6D6, 155.5 MHz, 294 K): δ = 1.78 ppm (s,
sharp). 13C{1H} NMR (C6D6, 100.6 MHz, 295 K): δ = 24.1
[CH(CH3)2], 25.2 (THF–CH2), 29.1 [CH(CH3)2], 68.8 (THF–
OCH2), 120.7 (d, JP,C = 3.1 Hz, Ar–C), 123.5 (d, JP,C = 2.0 Hz, Ar–
C), 127.5 (d, JP,C = 11.0 Hz, Ar–C), 129.5 (d, JP,C = 2.6 Hz, Ar–
C), 131.7 (d, JP,C = 8.0 Hz, Ar–C), 140.0 (d, JP,C = 93.4 Hz, Ar–
C), 144.4 (d, JP,C = 6.0 Hz, Ar–C), 146.3 (Ar–C) ppm. 31P{1H}
NMR (C D , 121.5 MHz, 303 K): δ = –7.7 (s) ppm. IR (nujol): ν
˜
6
6
= 1588 (w), 1461 (s), 1430 (s), 1378 (m), 1366 (s), 1321 (m), 1269
(s), 1230 (m), 1216 (m), 1111 (m), 1100 (m), 1050 (m), 1015 (m),
794 (m), 775 (m), 753 (m), 710 (m), 698 (s) cm–1.
128.8 (br., ArC), 129.3 (d, JP,C = 2.3 Hz, ArC), 131.6 (d, JP,C
=
8.3 Hz, ArC), 132.9 (br. d, JP,C = 6.6 Hz, ArC), 141.6 (d, vbr., JP,C
≈ 94 Hz, ArC), 148.0 (vbr., ArC) ppm. 31P{1H} NMR [C6D6/THF
(ca. 30:1), 121.5 MHz, 298 K]: δ = –14.6 (s) ppm. IR (solid, ATR):
Data for [DipLLi(THF)2] (10): 1H NMR (C6D6, 300.1 MHz, 303 K):
δ = 1.06 [d, J = 6.8 Hz, 24 H, CH(CH3)2], 1.27 (mc, 8 H, THF–
CH2), 3.44 (mc, 8 H, THF–OCH2), 3.84 [sept, J = 6.8 Hz, 4 H,
CH(CH3)2], 6.92–7.26 (m, 12 H, Ar–H), 7.50–7.62 (m, 4 H, Ar–H)
ppm. 7Li NMR (C6D6, 155.5 MHz, 300 K): δ = 1.72 ppm (br. d,
JP,Li = 7.2 Hz). 13C{1H} NMR (C6D6, 75.5 MHz, 303 K): δ = 24.2
[CH(CH3)2], 25.5 (THF-CH2), 29.0 [CH(CH3)2], 68.4 (THF–
OCH2), 120.7 (d, JP,C = 2.9 Hz, Ar–C), 123.5 (d, JP,C = 2.1 Hz, Ar–
C), 127.5 (d, JP,C = 10.9 Hz, Ar–C), 129.4 (d, JP,C = 2.6 Hz, Ar–
C), 131.7 (d, JP,C = 8.1 Hz, Ar–C), 140.1 (d, JP,C = 93.5 Hz, Ar–
C), 144.3 (d, JP,C = 6.0 Hz, Ar–C), 146.5 (Ar–C) ppm. 31P{1H}
ν = 2920 (m), 2853 (s), 1588 (w), 1472 (s), 1433 (m), 1418 (m), 1375
˜
(m), 1303 (s), 1247 (s), 1215 (m), 1164 (m), 1103 (s), 1029 (s), 979
(m), 942 (m), 851 (s), 821 (w), 763 (m), 749 (m), 698 (s), 658 (m)
cm–1.
Crystals of [{MesLNa(THF)}2]·0.5C6H6 (14·0.5C6H6) were ob-
tained by recrystallizing a small quantity of 12 from toluene/THF
(ca. 8:1) at –25 °C. This likely reflects more closely the composition
studied by the solution NMR spectroscopic experiments in deuter-
ated benzene/THF.
NMR (C D , 121.5 MHz, 303 K): δ = –7.8 (m) ppm. IR (nujol): ν
˜
6
6
= 1585 (w), 1462 (s), 1431 (s), 1377 (s), 1355 (m), 1324 (s), 1275
(s), 1215 (m), 1104 (s), 1072 (m), 1052 (s), 1017 (m), 993 (m), 903
(m), 765 (s), 750 (m), 710 (m), 699 (s) cm–1.
[
MesLK] (16): Toluene (30 mL) was added to a mixture of MesLH 4
(0.54 g, 1.10 mmol, 1.0 equiv.) and [K{N(SiMe3)2}] (0.26 g,
1.30 mmol, 1.18 equiv.) at 0 °C and vigorously stirred overnight
[(DipLNa)2] (11): Toluene (20 mL) was added to a mixture of DipLH with slow warming to room temperature. The precipitate was re-
3 (1.02 g, 1.90 mmol, 1.0 equiv.) and [Na{N(SiMe3)2}] (0.37 g, moved by filtration, washed with n-hexane (10 mL) and dried under
2.00 mmol, 1.05 equiv.) at 0 °C and vigorously stirred overnight vacuum. A small second crop was isolated after concentration of
with slow warming to room temperature. The formed precipitate
of 11 was removed by filtration, washed with n-hexane (10 mL) and
dried under vacuum. The supernatant solution was concentrated
to approximately 8 mL under reduced pressure and cooled to 4 °C
to afford a second crop of 11 in 72% yield. Crystals of [(DipLNa)
2] 11 were obtained from a toluene/n-hexane mixture and crystals
of [(DipLNa)2]·4C6H6 (11·4C6H6) were obtained from warm benz-
ene, yield 0.77 g (72%); m.p. 170–172 °C (melts), 247–250 °C (de-
comp). The NMR spectra were recorded and are given at elevated
temperatures owing to the poor solubility in aromatic solvents at
room temperature. No significant differences between spectra re-
corded at 25 or 65 °C were found. 1H NMR (C6D6, 300.1 MHz,
the supernatant solution and cooling to 4 °C, yield 0.38 g (70%);
m.p. 178–180 °C (melts), 216–218 °C (decomp.). C30H32KN2P
(490.67): calcd. C 73.44, H 6.57, N 5.71; found C 73.36, H 6.46, N
5.81. The compound was only poorly soluble in hydrocarbon sol-
vents and the 1H NMR spectrum was recorded at elevated tempera-
tures. Alternatively, the addition of small quantities of coordinating
solvents such as THF enhanced the solubility significantly. 1H
NMR (C6D6, 300.1 MHz, 333 K): δ = 2.14 (s, 6 H, p-CH3), 2.24
(s, 12 H, o-CH3), 6.72 (s, 4 H, m-ArH), 6.99–7.15 (m, 4 H, Ar–H),
1
8.02–8.18 (br. m, 6 H, Ar–H) ppm. H NMR [C6D6/THF (ca. 5:1,
THF resonances not given), 300.1 MHz, 298 K]: δ = 2.16 (s, 6 H,
p-CH3), 2.40 (s, 12 H, o-CH3), 6.78 (s, 4 H, m-ArH), 7.02–7.17 (m,
338 K): δ = 0.98 [d, J = 6.9 Hz, 48 H, CH(CH3)2], 3.71 [sept, J = 4 H, Ar–H), 8.21–8.34 (br. m, 6 H, Ar–H) ppm. 13C{1H} NMR
6.9 Hz, 8 H, CH(CH3)2], 6.93–7.05 (m, 16 H, Ar–H), 7.10–7.16 (m, [C6D6/THF (ca. 5:1, THF resonances not given), 75.5 MHz,
Eur. J. Inorg. Chem. 2015, 258–270
268
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FULL PAPER
Table 2. Crystallographic data.
2
4 (4Ј)
4 (4ЈЈ)
5·C6H14
6·C6H6
7·8·C6H14
9
Chemical formula
Formula mass
Crystal system
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C21H22NP
319.37
C30H33N2P
452.55
C30H33N2P
452.55
triclinic
C78H102Li2N4P2 C66H70Li2N4P2
C150H190Li4N14P4 C40H52LiN2OP
1171.46
triclinic
995.08
triclinic
2340.80
monoclinic
25.9411(6)
23.3546(6)
23.5675(6)
90.00
103.907(3)
90.00
13859.7(6)
123(2)
614.75
triclinic
monoclinic
15.3831(17)
4.6094(4)
25.954(2)
90.00
106.986(9)
90.00
1760.0(3)
123(2)
monoclinic
12.0581(4)
15.5786(6)
13.3339(4)
90.00
91.628(3)
90.00
2503.74(15)
123(2)
11.200(2)
11.300(2)
11.660(2)
117.51(3)
97.15(3)
101.01(3)
1245.8(4)
100(2)
12.295(3)
12.854(3)
23.374(5)
89.36(3)
82.22(3)
69.34(3)
3422.0(12)
100(2)
11.770(2)
13.440(3)
17.440(4)
82.36(3)
88.38(3)
84.59(3)
2721.8(10)
100(2)
15.424(3)
15.518(3)
16.428(3)
105.28(3)
95.67(3)
102.52(3)
3651.7(13)
173(2)
γ [°]
Unit-cell volume [Å3]
T [K]
¯
P1
2
¯
¯
¯
P1
Space group
Z
P21/c
4
P21/n
4
P1
P1
P21/c
2
2
4
4
Radiation type
Mo-Kα
0.156
10449
Mo-Kα
0.130
26133
synchrotron
0.131
23397
6956
synchrotron
0.109
60775
17002
synchrotron
0.125
65818
12084
Mo-Kα
0.109
55289
Mo-Kα
0.107
32538
μ [mm–1]
No. of reflections measured
No. of independent reflections 3110
7294
24378
17602
Completeness (to θ) [%]
Rint
99.8 (at 25.00°)
0.0663
0.0553
99.9 (at 30.00°) 98.2 (at 25.00°) 99.7 (at 25.00°) 99.4 (at 27.22°)
99.8 (at 25.00°)
0.0325
0.0792
0.2103
0.1161
0.2425
1.035
1.210, –0.847
99.7 (at 28.00°)
0.0274
0.0484
0.1148
0.0789
0.1305
1.032
0.0281
0.0510
0.0851
0.0382
Final R1 values [IϾ2σ(I)]
0.0398
0.0464
0.0535
0.0419
Final wR(F2) values [IϾ2σ(I)] 0.1360
0.1023
0.1178
0.1327
0.1059
Final R1 values (all data)
0.0706
0.0532
0.0507
0.0648
0.0457
Final wR(F2) values (all data) 0.1494
0.1122
0.1211
0.1436
0.1087
GoF on F2
1.054
1.029
1.045
1.070
1.061
Largest diff. peak, hole [eÅ–3] 0.596, –0.427
0.411, –0.293
0.369, –0.568
0.943, –0.537
0.256, –0.434
0.265, –0.292
Table 2. (continued)
10
11·4C6H6
11
13
14·0.5C6H6
16 (16Ј)
16 (16ЈЈ)
Chemical formula
Formula mass
Crystal system
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C44H60LiN2O2P
686.85
C96H112N4Na2P2 C72H88N4Na2P2 C44H60N2NaO2P C71H83N4Na2O2P2 C30H32KN2P
C30H32KN2P
490.65
1429.82
monoclinic
11.0370(2)
18.8288(4)
20.3086(4)
90.00
98.047(2)
90.00
4178.84(14)
123(2)
1117.38
triclinic
702.90
monoclinic
17.749(4)
11.828(2)
20.096(4)
90.00
102.80(3)
90.00
4114.1(14)
123(2)
Cc
1132.33
triclinic
490.65
monoclinic
17.060(3)
11.798(2)
20.701(4)
90.00
105.32(3)
90.00
4018.5(14)
100(2)
monoclinic
14.1174(6)
11.8508(5)
15.7569(6)
90.00
102.398(4)
90.00
2574.69(18)
123(2)
monoclinic
27.755(6)
11.800(2)
18.924(4)
90.00
124.47(3)
90.00
5109.9(18)
100(2)
10.2911(5)
10.5892(4)
15.3253(7)
88.799(4)
81.499(4)
73.415(4)
1582.61(12)
123(2)
10.325(2)
14.873(3)
20.320(4)
84.38(3)
87.57(3)
83.70(3)
3085.1(11)
100(2)
γ [°]
Unit-cell volume [Å3]
T [K]
¯
¯
Space group
Cc
P21/n
P1
P1
P21/n
C2/c
Z
4
2
1
4
2
4
8
Radiation type
synchrotron
0.106
33442
Mo-Kα
0.110
19402
Mo-Kα
0.127
13624
7621
Mo-Kα
0.114
12962
synchrotron
0.134
37119
18092
Mo-Kα
0.290
17747
synchrotron
0.292
39912
μ [mm–1]
No. of reflections measured
No. of independent reflec-
tions
9809
9091
6087
5609
5640
Completeness (to θ) [%]
Rint
Final R1 values [IϾ2σ(I)]
Final wR(F2) values
[IϾ2σ(I)]
99.1 (at 25.00°)
0.0507
0.0363
99.7 (at 27.00°) 99.6 (at 28.00°) 99.9 (at 25.00°) 91.9 (at 25.00°)
99.9 (at 27.00°)
0.0317
0.0366
99.6 (at 27.13°)
0.0604
0.0418
0.0232
0.0426
0.0957
0.0282
0.1015
0.2484
0.0379
0.0568
0.1353
0.1096
0.0765
0.2016
0.0897
0.0886
0.1027
Final R1 values (all data)
0.0377
0.0607
0.1044
1.033
0.366, –0.361
0.1109
0.2529
1.135
1.243, –0.414
0.0707
0.1504
1.023
0.345, –0.282
0.0979
0.2189
1.016
0.954, –0.626
0.0484
0.0954
1.039
0.403, –0.253
0.0474
0.1059
1.065
0.405, –0.497
Final wR(F2) values (all data) 0.0914
GoF on F2
Largest diff. peak, hole [eÅ–3] 0.391, –0.251
1.065
298 K]: δ = 20.7 (CH3), 22.1 (CH3), 127.5 (Ar–C), 127.5 (d, JP,C
=
ppm. IR (solid, ATR): ν = 2952 (m), 2920 (s), 2853 (s), 1458 (s),
˜
11.5 Hz, ArC), 128.6 (d, JP,C = 11.9 Hz, ArC), 129.3 (Ar–C), 131.9
(d, JP,C = 8.6 Hz, ArC) ppm. Note: Three ArC resonances are miss-
ing. Two downfield ArC resonances are believed to be broadened
into the baseline (compare with the very broad resonances found
for 12) and one is believed to the hidden by the strong solvent
1431 (m), 1421 (m), 1376 (m), 1325 (m), 1304 (m), 1285 (m), 1263
(s), 1164 (m), 1103 (m), 1041 (m), 983 (m), 857 (m), 840 (m), 761
(m), 746 (m), 711 (s), 699 (s) cm–1.
X-ray Crystallography: Suitable crystals were mounted in silicone
resonance. 31P{1H} NMR (C6D6, 121.5 MHz, 333 K): δ = –17.5 (s) oil and were either measured with an Oxford Xcalibur Gemini Ul-
Eur. J. Inorg. Chem. 2015, 258–270
269
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[5] A. Steiner, S. Zacchini, P. I. Richards, Coord. Chem. Rev. 2002,
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MX1 or MX2 beamlines (4ЈЈ, 5·C6H14, 6·C6H6, 10, 14·0.5C6H6 and
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fined anisotropically. Semiempirical (multiscan) absorption correc-
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ture of 14·0.5C6H6 is due to the experimental setup at the synchro-
tron and only one Φ scan could be collected. In 5·C6H14, the two
Li atoms are disordered and were modelled and refined with two
positions each to 65 and 35% parts. In 7·8·C6H14, one isopropyl
group of 8 is disordered and was modelled using two positions for
each carbon atom (55% part for C103–105 and 45% part for C157–
C159) and refined using geometry restraints. The lattice n-hexane
molecule in the same structure is disordered and was modelled with
two positions for each carbon atom (two 50% parts) using geome-
try restraints. In 9, two isopropyl groups are disordered and were
modelled and refined with two positions for C19–C21 (84 and 16%
parts) and C71–C73 (48 and 52% parts) using geometry restraints.
Two coordinated THF molecules are disordered and were modelled
and refined with two positions for O1 and C37–C40 (37 and 63%
parts) and C78–C80 (63 and 37% parts) using geometry restraints.
In 13, one coordinated THF molecule is severely disordered and
was modelled with two positions for each atom and refined using
geometry restraints. Selected bond lengths and angles of all crystal
structures are collected in Table 1 and refinement details are sum-
marized in Table 2.
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CCDC-1025687 (2), -1025688 (4Ј), -1025689 (4ЈЈ), -1025690
(5·C6H14), -1025691 (6·C6H6), -1025692 (7·8·C6H14), -1025693 (9),
-1025694 (10), -1025695 (11·4C6H6), -1025696 (11), -1025697 (13),
-1025698 (14·0.5C6H6), -1025699 (16Ј), and -1025700 (16ЈЈ) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
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Received: September 26, 2014
Published Online: December 11, 2014
Eur. J. Inorg. Chem. 2015, 258–270
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