Macrocyclic Complexes Derived from Four cis-L2Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries

Article abstract of DOI:10.1002/chem.202100305

The dialkyl malonate derived 1,3-diphosphines R₂C(CH₂PPh₂)₂ (R=a, Me; b, Et; c, n-Bu; d, n-Dec; e, Bn; f, p-tolCH₂) are combined with (p-tol₃P)₂PtCl₂ or trans-(p-tol₃P)₂Pt((C≡C)₂H)₂ to give the chelates cis-(R₂C(CH₂PPh₂)₂)PtCl₂ (2 a–f, 94–69 %) or cis-(R₂C(CH₂PPh₂)₂)Pt((C≡C)₂H)₂ (3 a–f, 97–54 %). Complexes 3 a–d are also available from 2 a–d and excess 1,3-butadiyne in the presence of CuI (cat.) and excess HNEt₂ (87–65 %). Under similar conditions, 2 and 3 react to give the title compounds [(R₂C(CH₂PPh₂)₂)[Pt(C≡C)₂]₄ (4 a–f; 89–14 % (64 % avg)), from which ammonium salts such as the co-product [H₂NEt₂]⁺ Cl^? are challenging to remove. Crystal structures of 4 a,b show skew rhombus as opposed to square Pt₄ geometries. The NMR and IR properties of 4 a–f are similar to those of mono- or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono-platinum or Pt(C≡C)₂Pt species, the UV-visible spectra show much more intense and red-shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt₄C₁₆ cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt₃C₁₂ and Pt₅C₂₀ homologs and selected equilibria are explored computationally.

Full text of DOI:10.1002/chem.202100305

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Chemistry—A European Journal
Macrocyclic Complexes Derived from Four cis-L2Pt Corners
and Four Butadiynediyl Linkers; Syntheses, Electronic
Structures, and Square versus Skew Rhombus Geometries
Brenna K. Collins+,[a] Melissa Clough Mastry+,[a, b] Andreas Ehnbom+,[a] Nattamai Bhuvanesh,[a]
Michael B. Hall,*[a] and John A. Gladysz*[a]
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Abstract: The dialkyl malonate derived 1,3-diphosphines R2C
(CH2PPh2)2 (R=a, Me; b, Et; c, n-Bu; d, n-Dec; e, Bn; f, p-tolCH2)
metries. The NMR and IR properties of 4a–f are similar to
those of mono- or diplatinum model compounds. However,
are combined with (p-tol3P)2PtCl2 or trans-(p-tol3P)2Pt((C� cyclic voltammetry gives only irreversible oxidations. As
C)2H)2 to give the chelates cis-(R2C(CH2PPh2)2)PtCl2 (2a–f, 94–
69%) or cis-(R2C(CH2PPh2)2)Pt((C�C)2H)2 (3a–f, 97–54%). Com-
plexes 3a–d are also available from 2a–d and excess 1,3-
butadiyne in the presence of CuI (cat.) and excess HNEt2 (87–
65%). Under similar conditions, 2 and 3 react to give the title
compounds [(R2C(CH2PPh2)2)[PKt(C�C)2K]4 (4a–f; 89–14% (64%
avg)), from which ammonium salts such as the co-product
[H2NEt2]+ ClÀ are challenging to remove. Crystal structures of
4a,b show skew rhombus as opposed to square Pt4 geo-
compared to mono-platinum or Pt(C�C)2Pt species, the UV-
visible spectra show much more intense and red-shifted
bands. Time dependent DFT calculations define the transi-
tions and principal orbitals involved. Electrostatic potential
surface maps reveal strongly negative Pt4C16 cores that likely
facilitate ammonium cation binding. Analogous electronic
properties of Pt3C12 and Pt5C20 homologs and selected
equilibria are explored computationally.
Introduction
25 years. Of particular interest have been adducts in which the
polygon edges are polyynediyl moieties, À (C�C)nÀ , such as in
the “triangle” I and “square” II in Scheme 1.[2–6] Although there
are many reasons to pursue such species, one of the more
obvious would be to attempt the extrusion of the corners, or
appropriate subunits thereof, to afford a molecule often called
“cyclocarbon” (III).[7] This consists of a circle of sp hybridized
carbon atoms, and the polyyne valence isomer shown in
Scheme 1 is widely viewed as more stable than the cumulated
form, except at smaller ring sizes.[7] The compound with n=9,
cyclo[18]carbon or C18, has recently been generated on a NaCl/
Cu(111) surface by CO extrusion from a “triangle” with cyclo-
butenedione corners (I-ix).[8]
Macrocycles that approximate the shapes of polygons[1] have
been at the forefront of many lines of research over the last
Some corner units that have been incorporated into I and II
are illustrated in Scheme 1 (i-xxi). These include several
platinum(II) fragments (xx-xxi) that have been applied in
“square” systems II.[5] These complexes, which were reported
some time ago by Youngs, Bruce, and Anderson, are separately
depicted in Scheme 2 (IV-i’ through IV-iv’). However, the
transcript has since remained silent with regard to higher
homologs[9] or follow-up studies.
We have had an ongoing interest in platinum alkynyl
complexes, including diplatinum polyynediyl species Pt(C�C)nPt
where n is as high as 14.[10–13] Thus, it was natural that the
preceding topics should eventually capture our attention. Given
the number of reactions that effect efficient reductive elimi-
nations of sp2 or sp hybridized hydrocarbyl groups from
platinum(II),[14] species of the type IV constitute attractive
precursors to cyclocarbons III. Furthermore, longer À (C�C)nÀ
segments would afford cyclocarbons with diminished ring
strain. That derived via extrusion of the corner units of II or IV,
C16, was viewed as likely to be quite reactive and problematic to
isolate.
Scheme 1. Some previously characterized polygon shaped molecules with
butadiynediyl or -(C�C)2- edges.[6]
[a] B. K. Collins,+ Dr. M. Clough Mastry,+ A. Ehnbom,+ Dr. N. Bhuvanesh,
Prof. Dr. M. B. Hall, Prof. Dr. J. A. Gladysz
Department of Chemistry
Texas A&M University
P.O. Box 30012, College Station, Texas 77842-3012 (USA)
E-mail: mbhall@tamu.edu
However, our initial efforts at synthesizing higher homologs
of the Pt4C16 complexes IV unearthed a number of complica-
tions, one being solubility. In an effort to regroup, we decided
to revisit the syntheses of cyclic tetraplatinum complexes with
C4 edges, but with building blocks that would be better
platforms for extended systems. Furthermore, the electronic
structure and redox properties of IV had never been inves-
tigated, outside of one early computational effort.[5b] Accord-
gladysz@mail.chem.tamu.edu
[b] Dr. M. Clough Mastry+
This author has previously published as Melissa Clough.
Present address:
BASF Refinery Catalysts
25 Middlesex-Essex Tpk., Iselin, NJ 08830 (USA)
[+] These authors contributed equally to this work.
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/chem.202100305
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solubilities of the preceding Pt4C16 systems or homologs with longer
À (C�C)nÀ segments. As summarized in Scheme 3, those studied
included the previously reported 1,3-diphosphines Me2C(CH2PPh2)2
(1a),[15] Et2C(CH2PPh2)2 (1b),[15] and Bn2C(CH2PPh2)2 (1e),[16] and the
new diphosphines n-Bu2C(CH2PPh2)2 (1c), n-Dec2C(CH2PPh2)2 (1d),
and (p-tolCH2)2C(CH2PPh2)2 (1f).
The new ligands were synthesized as depicted in Scheme 3.
In the case of 1c, the corresponding 1,3-diol was commercially
available. A mesylation/substitution sequence gave 1c in 76%
overall yield. For 1d and 1f, it was necessary to start from
diethyl malonate.[17] The requisite dialkylated malonates were
obtained by standard protocols and reduced to the 1,3-diols
(93–98%). Procedures analogous to those used for 1c then
delivered 1d and 1f (83–48%). The literature syntheses of the
previously reported diphosphines were conceptually
similar.[16,18]
All diphosphines were air stable white solids although 1c,d
had tendencies to oil. They readily oxidized in solution. All new
compounds in Scheme 3 were characterized by NMR and IR
spectroscopy, mass spectrometry, and microanalyses, as sum-
marized in the experimental section. The 31P{1H} NMR chemical
shifts of the diphosphines are collected in Table 1. The PCH2C
13C{1H} NMR signals were components of non-first-order spin
systems and coupling constants were assigned by simulations
as described elsewhere.[19]
Scheme 2. Previously reported Pt4C16 complexes with four like corners.
ingly, we report below the syntheses of six new Pt4C16 adducts,
their detailed physical characterization, and DFT data that
provide insight into various conformational, electronic, and
spectroscopic properties, as well as potential equilibria.
Monoplatinum complexes
Attention was turned to the preparation of suitable platinum
precursors for accessing the target molecules. Per the earlier
syntheses in Scheme 2, the dichloride complexes cis-(R2C
(CH2PPh2)2)PtCl2 (2) and bis(butadiynyl) complexes cis-(R2C
(CH2PPh2)2)Pt((C�C)2H)2 (3) were sought. As shown in Scheme 4,
the former could be isolated in 69–94% yields (average 83%)
from reactions of the 1,3-diphosphines 1a–f with cis/trans
Results
Diphosphine syntheses
[20]
It was thought that geminally disubstituted bis(diphenylphosphino)-
propane chelate ligands would likely enhance the lipophilicities and
mixtures of (p-tol3P)2PtCl2 in CH2Cl2. Complexes 2a–f were air
stable white solids of generally modest solubilities. Nonetheless,
Scheme 3. The 1,3-diphosphine ligands used in this study, and syntheses of those not previously reported (1c,d,f).
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were treated with excess 1,3-butadiyne in the presence of CuI
Table 1.
(catalyst) and HNEt2 (cosolvent and base for the HCl generated).
These represent the standard Sonogashira/Hagihara conditions[21]
that have often been used to construct platinumÀ alkynyl bonds,
as also applied in Scheme 2 above. As shown in Scheme 4,
chromatographic workups gave 3a–d as air stable tan or light
yellow solids in 65–87% yields (average 73%).
Alternatively, (p-tol3P)2PtCl2 was similarly treated with 1,3-
butadiyne (route B). Following published procedures, the bis
(butadiynyl) complex trans-(p-tol3P)2Pt((C�C)2H)2 was isolated in
47–78% yields.[12b,19] This adduct was combined with the 1,3-
diphosphines 1a–f to give the target complexes 3a–f in 54–
97% (average 82%) yields. Overall, the two routes were judged
comparable in terms of ease and yields.
Complexes 3a–f were characterized analogously to the
dichlorides 2a–f. They were more soluble in common solvents
such as CH2Cl2 or CHCl3. However, solutions (non-degassed)
generally showed significant decomposition after several days.
The 1JPPt values (2200–2300 Hz; Table 1) were much smaller than
those of 2a–f (3300–3400 Hz).
Complex
31P{1H} NMR (1JPPt (Hz))
1a
1b
1c
1d
1e
1f
2a
2b
2c
À 26.2
À 26.2
À 25.8
À 25.8
À 26.3
À 26.1
À 1.3 (3431)
À 2.5 (3429)
À 2.6 (3419)
À 2.6 (3417)
À 2.0 (3376)
À 2.0 (3386)
À 4.9 (2224)
À 5.6 (2257)
À 6.4 (2225)
À 6.6 (2221)
À 4.8 (2192)
À 3.3 (2196)
À 6.1 (2219)
À 7.7 (2243)
À 8.5 (2247)
À 8.6 (2240)
À 4.8 (2192)
À 4.6 (2172)
2d
2e
2f
3a[a]
3b
3c
3d
3e
3f
4a[b]
4b[b]
4c[b]
4d
4e
4f
The 13C{1H} NMR signals of the sp hybridized carbon atoms
are summarized in Table 2. The chemical shift trends follow
those of related platinum mono(butadiynyl) complexes re-
ported earlier.[10a,b] However, the PtC� signals are now doublets
of doublets due to coupling to inequivalent cis and trans
phosphorus atoms (2JCP). For reference, the PtC� signal of the
precursor trans-(p-tol3P)2Pt((C�C)2H)2 is a triplet due to coupling
to two homotopic cis phosphorus atoms (CDCl3, 102.7 ppm,
[a] Data for trans-(p-tol3P)2Pt((C�C)2H)2:[12b] 17.0 ppm, 1JPPt 2527 Hz. [b] Data
in CD2Cl2: 4a, À 5.5 to À 5.7 (2200–2195); 4b, À 7.0 to À 7.4 (2230–2196); 4c,
À 7.7 (2254).
NMR spectra (1H, 13C{1H}, 31P{1H}) could be recorded without
difficulty in CDCl3 or CD2Cl2. The NMR, IR, and microanalytical
data are summarized in the experimental section and Table 1.
Two routes to the bis(1,3-butadiynyl) complexes 3a–f were
investigated (A, B). In route A, the dichloride complexes 2a–d
2
2
2JCP =15.3 Hz).[22] The JCP value is similar to the smaller JCP
values in Table 2 (18.2–22.1 Hz), which are thereby assigned to
2
the cis phosphorus atoms. The much larger JCP values (145.6–
149.0 Hz) must therefore be associated with the trans
Scheme 4. Syntheses of monoplatinum complexes.
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Table 2. 13C{1H} NMR data for 3a–3f and 4a–4f (δ, ppm; CDCl3 unless noted).
Complex
PtC�C (2JCP (Hz)[a])
PtC�C (J (Hz))[b]
C�C
�CH
3a
3b
3c
3d
3e
3f
95.4 (146.6, 18.2)
95.7 (149.0, 20.0)
96.1 (148.0, 19.2)
95.8 (147.2, 19.0)
96.1 (145.6, 22.1)
96.3 (146.4, 19.4)
91.8 (141.1, 21.1)
91.8 (148.2, 10.6)[c]
91.4 (144.9, 19.9)
93.2 (137.3, 29.6)[c]
92.3 (135.6, 16.8)[c]
91.3 (146.1, 20.1)
92.5 (149.0, 19.1)
88.4 (149.6, 18.1)
91.9 (18.4)
91.7 (17.8)
91.6 (18.2)
91.5 (17.9)
92.8 (18.1)
92.7 (18.4)
96.9 (16.9)
96.7 (18.9)[c]
96.8 (21.0)
96.7 (23.2)[c]
96.5 (17.3)[c]
96.5 (15.1)
97.6 (19.9)
97.5 (16.9)
71.7
71.8
72.0
71.8
71.8
71.9
–
–
–
–
–
61.6
61.3
61.2
61.1
61.9
61.9
–
–
–
–
–
4a
4b
4c
4d
4e
4f
–
–
–
–
–
–
[a] The smaller value is derived from the cis phosphorus atom, as established in the text. [b] Multiplet, including triplet with apparent J value indicated. For
more detailed analyses of NMR spectra of complexes related to 3a–f, including simulations.[19] [c] These data are from a spectrum recorded in CD2Cl2.
phosphorus atoms. For the PtC�C signals, only one coupling is
resolved (3JCP =17.8–18.4 Hz), and assigned to the trans
phosphorus atom.
geminal dimethyl groups (Scheme 2),[5b] and a comparative
table is provided in the Supporting Information.
Single crystals of the solvate 3a·CH2Cl2 could be grown. X-
ray data were collected and the structure refined as summar-
ized in Table 3 and the experimental section. Thermal ellipsoid
plots are shown in Figure 1. The metrical parameters are very
similar to those of the analogous compound lacking the
Syntheses of tetraplatinum complexes
Next, the Pt4C16 complexes [(R2C(CH2PPh2)2)[PKt(C�C)2K]4 (4) were
sought. As depicted in Scheme 5, equimolar quantities of 2 and
3
were reacted under Sonogashira/Hagihara coupling
Table 3. General crystallographic data.
[a]
Complex
3a·CH2Cl2
4a[a]
4b·2CH2Cl2
4b·3.44DMSO[b]
empirical formula
formula weight
temperature [K]
diffractometer
wavelength [Å]
crystal system
space group
unit cell dimensions:
a [Å]
C38H34Cl2P2Pt
818.58
110(2)
Bruker GADDS
1.54178
orthorhombic
Pbca
C132H111P8Pt4
2725.33
110(2)
Bruker GADDS
1.54178
C142H140 Cl4P8Pt4
3016.45
110(2)
Bruker GADDS
1.54178
C164.9H210.6O12.4P8Pt4S12.4
3818.51
110.0
Bruker QUEST
0.71073
triclinic
triclinic
triclinic
̄
̄
̄
P1
P1
P1
17.3247(11)
16.4634(11)
24.0781(16)
90
90
90
6867.6(8)
8
13.9731(6)
19.3822(8)
32.3857(13)
90.232(2)
100.137(2)
94.743(2)
8603.0(6)
2
21.4521(12)
22.7781(15)
25.5864(15)
101.570(3)
106.404(3)
111.935(3)
10446.6(11)
2
0.959
6.173
19.9523(10)
20.5839(10)
24.8550(12)
113.118(2)
107.319(2)
93.375(2)
8781.1(8)
2
1.444
3.451
b [Å]
c [Å]
°
α [ ]
°
β [ ]
°
γ [ ]
V [Å3]
Z
1calc [Mg/mÀ 3
]
1.583
10.144
1.052
6.895
μ [mmÀ 1
]
F(000)
3232
2670
2984
3861
crystal size [mm3]
0.08×0.07×0.02
3.67 to 60.00
À 18, 19; À 18, 18; À 27,27
96875
0.10 × 0.09 × 0.04
2.29 to 60.00
À 15, 14; À 21, 21; À 36, 36
73407
0.04×0.03×0.03
1.917 to 60.50
À 24, 24; À 26, 26; À 29, 29
146971
0.162×0.149×0.024
1.80 to 24.73
À 23, 23; À 24, 24; À 29, 29
229989
°
Θ limit [ ]
index range (h, k, l)
reflections collected
independent reflections
completeness to Θ
max. and min. transmission
data/restraints/parameters
goodness-of-fit on F2
5095 [R(int)=0.0911]
99.9
0.4623 and 0.2365
5095/0/390
24343 [R(int)=0.0486]
95.3
0.7519 and 0.6310
24343/0/1297
0.960
31113 [R(int)=0.0765]
93.3
0.4623 and 0.3237
31113/434/1431
1.069
29975 [R(int)=0.0580]
99.7
0.3306 and 0.2328
29975/121/1540
1.027
0.969
R indices (final) [I>2σ(I)]
R1 =0.0232, wR1 =0.0493
R2 =0.0320, wR2 =0.0503
0.674 and À 0.843
R1 =0.0396, wR1 =0.0996
R2 =0.0505, wR2 =0.1030
2.538 and À 1.109
R1 =0.0716, wR1 =0.1895
R2 =0.1083, wR2 =0.2153
6.546 and À 2.016
R1 =0.0417, wR1 =0.0983
R2 =0.0503, wR2 =0.1027
3.812 and À 1.941
R indices (all data)
largest diff. peak and hole [eÅÀ 3
]
[a] Some or all of the solvent molecules associated with these structures were removed using protocols described in the experimental section. Hence, the
formula weight and density are underestimated. [b] The empirical formula includes nine DMSO molecules that were masked; see experimental section.
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Figure 1. Thermal ellipsoid plots (50% probability level) of the crystal structure of 3a·CH2Cl2 with the solvate molecule omitted. Bond lengths (Å) and angles
°
( ) associated with platinum or the butadiynyl ligands: Pt1À C4 1.998(4), Pt1À C8 2.004(4), PtÀ P2 2.2912(10), PtÀ P3 2.2870(9), C4�C5 1.212(5), C5À C6 1.387(5),
C6�C7 1.178(5), C8�C9 1.211(5), C9À C10 1.376(6), C10�C11 1.188(5), P2À Pt1À P3 96.06(3), Pt1À C4À C5 174.2(3), Pt1À C8À C9 175.6(3), C4À C5À C6 175.1(4),
C5À C6À C7 179.8(6), C8À C9À C10 178.2(4), C9À C10À C11 178.9(4).
conditions.[21] In contrast to the similar platinumÀ carbon bond
CuI. In no case were ions diagnostic of other macrocycle cores
observed (Pt3C12, Pt5C20, Pt6C24, etc.).
forming reactions involving 1,3-butadiyne in Scheme 4, those in
°
Scheme 5 required elevated temperatures (55 C) and extended
time periods (48–72 h) to go to completion.
The Pt4C16 complexes 4a–f were isolated as air stable and
usually tan solids in 89–14% yields. Although these species
could be “completely characterized”, including three crystal
structures, analytically pure samples could not be obtained. As
detailed in the experimental section, all complexes were
admixed with 1–2 equiv. of an ammonium salt, as established
Physical characterization of tetraplatinum complexes
The NMR properties of 4a–f generally paralleled those of 3a–f.
As summarized in Table 1, the 31P{1H} NMR chemical shifts and
1JPPt values were quite similar. However, the 13C{1H} NMR
chemical shifts of the PtC�C signals (Table 2) flip-flopped, with
Cα downfield of Cβ, as could be unambiguously inferred from
by H and 13C{1H} NMR. In many cases, this was [H2NEt2]+ ClÀ ,
1
n
the standard coproduct of the Sonogashira/Hagihara
conditions.[21] In other cases, this was the protonated tertiary
amine [HNEt3]+ ClÀ , as samples remained at the origin in silica
gel thin layer chromatography unless HNEt2 or NEt3 was added
to the eluting solvent (e.g., 5% in CH2Cl2). All attempts to
remove these materials by washings[23] or heating under
vacuum were unsuccessful.
These observations were reproduced by several coworkers
over the course of several years. Microanalyses showed
appropriate levels of chlorine, but the presence of lesser
amounts of iodine (from the CuI catalyst) was not excluded. The
formula weight of the ammonium salt was factored into all
yield calculations. Typical NMR spectra, which show minor
impurities, are included in the Supporting Information. Similar
observations were reported by Bruce and Anderson with their
Pt4C16 complexes in Scheme 2.[5b,c] Insight regarding this
phenomenon is provided by DFT calculations below.
Mass spectrometry represents another probe of composi-
tion, and the ESI+ traces of 4a,b showed strong ions
corresponding to [4+HNEt2]+ (40–25%). MALDI+ experiments
involving various matrices never showed amine derived
adducts. However, ions of the composition [4+H]+, [4+K]+ or
[4+Cu]+ could be detected. Since copper was not present in
the matrices employed, the last ion must originate from the
the JCP values. The IR spectra exhibited a single νC�C band
(2150–2191 cmÀ 1), always within 8 cmÀ 1 of that found for 3a–f.
To our knowledge, no UV-visible or cyclic voltammetry data
for the previously synthesized Pt4C16 systems in Scheme 2 have
been reported. Accordingly, UV-visible spectra of 4a,b were
recorded in CH2Cl2. These are depicted in Figure 2, together
with spectra of the precursor cis bis(butadiynyl) complexes 3a,b
and the diplatinum butadiynediyl or PtC4Pt complex trans,trans-
(C6F5)(p-tol3P)2Pt(C�C)2Pt(Pp-tol3)2(C6F5) (5). The Pt4C16 systems
exhibit much more intense and red-shifted absorptions, indicat-
ing chromophoric units fundamentally different from those in
related Pt((C�C)2H)2 or Pt(C�C)2Pt species. This is further treated
computationally below.
Cyclic voltammograms of the PtC4Pt complex 5 in CH2Cl2
under standard conditions exhibit a partially reversible one
electron oxidation.[10a,13b] However, parallel experiments with
4a,b show multistage oxidations (0.8–1.2 V) that are essentially
irreversible.
After some effort, single crystals of a solvate of 4a were
obtained from DMSO/EtOAc. X-ray data were collected and the
structure refined as summarized in Table 3 and the experimen-
tal section. Numerous DMSO molecules were present, most of
which were disordered. In a standard protocol they were
removed using the programs SQUEEZE and PLATON. Further
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Figure 2. UV-visible spectra of the Pt4C16 complexes 4a,b·([H2NEt2]+ ClÀ )n,
the precursor Pt(C4H)2 species 3a,b, and the PtC4Pt species 5 (3.0×10À 5 M in
CH2Cl2). λmax (nm) [ɛ (MÀ 1 cmÀ 1)]: 4a, 266 [564,000], 327 [602,000], 350
[454,000]; 4b, 266 [639,000], 330 [635,000], 351 [525,000]; 3a, 268 [130,000],
277 [138,000], 304 [166,000]; 3b, 268 [128,000], 277 [136,000], 304 [165,000];
5, 330 [17,500], 350 [13,600]. The ɛ values for 4a,b are calculated including
the formula weight of the [H2NEt2]+ ClÀ present (see text and experimental
section).
The perspectives in Figure 3 obscure an important structural
feature. Namely, the Pt4C16 units are not planar, but rather
puckered, reminiscent of cyclobutane. This trait is highlighted
in the hinge like partial structures in Table 5. Two platinum
atoms with a 1,3 relationship define the pivot pin of a hinge
(Pt1, Pt3), and the other two the distal termini of the leaves of a
hinge (Pt2, Pt4).
As further illustrated in the inset in Table 5, the distance
between the former pair is always greater than that between
the latter (4a, 10.144 Å vs. 9.735 Å; 4b·2CH2Cl2, 10.710 Å vs.
10.582 Å; 4b·3.44DMSO 10.745 Å vs. 10.434 Å). The greater
distance between Pt2 and Pt4 in 4b·2CH2Cl2 or 4b·3.44DMSO
vs. 4a indicates a lower degree of puckering.
Scheme 5. Syntheses of Pt4C16 complexes that are admixed with 1–2 equiv.
of ammonium salts (see text).
details are provided in the experimental section. The molecular
structure of 4a is depicted in Figure 3 (top), and key metrical
parameters are summarized in Table 4.
Crystals of 4b could be grown from CH2Cl2/(toluene/Et2O).
X-ray data were similarly collected and treated. Of the many
solvent molecules present, two (both CH2Cl2) could be refined,
and the rest were removed via SQUEEZE and PLATON. The
molecular structure of 4b·2CH2Cl2 is also shown in Figure 3
(bottom). Interestingly, another solvate of 4b could be crystal-
lized from DMSO/EtOAc. Of the numerous DMSO molecules,
3.44 could be successfully modeled, and the rest were
“masked”. Since the structure of the Pt4C16 core was quite
similar to that in the previous structure, it is not depicted, but
metrical parameters are included in tables and graphics
below.[24]
Puckering is most simply quantified by the angle defined by
the planes of the two leaves. The planes were approximated by
those of the three component platinum atoms. As summarized
in Table 5, the angles in 4a, 4b·2CH2Cl2, and 4b·3.44DMSO
°
°
range from 111 to 138 . In contrast, crystal structures of the
previously reported complex IV-iii’ (two different solvates)
exhibit nearly planar Pt4C16 cores, as reflected by plane/plane
°
angles of 180–176 . Although this is consistent with essentially
square geometries, the Pt1À Pt3 and Pt2À Pt4 distances involving
opposite corners differ by 9–5% (ΔÅ 0.905 and 0.562).
In a quest for further insight, a 195Pt NMR spectrum of 4a
was recorded. Only a single signal was observed (À 3339 ppm,
1
CD2Cl2), coupled to 31P (t, JPtP =2215 Hz) with nearly the same J
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Table 4. Key crystallographic distances [Å] and angles [ ] for new Pt4C16
complexes.
[a]
4a
4b·2CH2Cl2
4b·3.44DMSO[a]
Pt1À C1
2.006(6)
1.998(7)
2.001(6)
2.010(6)
2.008(6)
2.009(6)
2.022(6)
1.998(6)
2.007(8)[b]
2.2825(15) 2.284(3)
2.2819(14) 2.266(3)
2.2810(15) 2.268(3)
2.2809(16) 2.279(3)
2.2771(15) 2.292(3)
2.2812(15) 2.267(4)
2.2770(14) 2.274(3)
2.2787(15) 2.276(3)
2.2800(2)[b] 2.276(9)[b]
2.019(11)
2.044(12)
2.007(10)
2.009(14)
2.051(13)
2.005(10)
2.011(10)
2.003(11)
2.019(18)[b]
2.006(6)
2.005(6)
1.986(5)
2.012(5)
2.018(6)
1.992(6)
2.026(7)
2.017(6)
2.008(13)[b]
2.2837(15)
2.2727(14)
2.2811(13)
2.2839(14)
2.2713(15)
2.2873(14)
2.2669(16)
2.2603(18)
2.276(9)[b]
1.209(8)
1.384(8)
1.210(8)
1.205(8)
1.383(8)
1.203(8)
1.200(9)
1.388(10)
1.180(9)
1.192(8)
1.386(9)
1.191(8)
1.199(10)[b]
86.2(2)
Pt1À C16
Pt2À C4
Pt2À C5
Pt3À C8
Pt3À C9
Pt4À C12
Pt4À C13
Avg PtÀ C
Pt1À P1
Pt1À P2
Pt2À P3
Pt2À P4
Pt3À P5
Pt3À P6
Pt4À P7
Pt4À P8
Avg PtÀ P
C1�C2
1.231(9)
1.377(9)
1.212(9)
1.192(8)
1.408(9)
1.187(8)
1.208(8)
1.376(9)
1.180(8)
1.218(8)
1.372(9)
1.220(9)
1.203(14)
1.383(15)
1.199(14)
1.151(16)
1.383(17)
1.216(15)
1.218(14)
1.347(15)
1.237(14)
1.195(15)
1.402(17)
1.167(15)
C2À C3
C3�C4
C5�C6
C6À C7
C7�C8
C9�C10
C10À C11
C11�C12
C13�C14
C14À C15
C15�C16
Avg C�C
C16À Pt1À C1
C4À Pt2À C5
C8À Pt3À C9
C12À Pt4À C13
Avg CÀ PtÀ C
Pt1À C1À C2
C1À C2À C3
C2À C3À C4
C3À C4À Pt2
Pt2À C5À C6
C5À C6À C7
C6À C7À C8
C7À C8À Pt3
Pt3À C9À C10
C9À C10À C11
C10À C11À C12
C11À C12À Pt4
Pt4À C13À C14
C13À C14À C15
C14À C15À C16
C15À C16À Pt1
Pt1À Pt2À Pt3 vs.
Pt1À Pt4À Pt3[c]
Pt1À Pt2
1.206(17)[b] 1.198(17)[b]
86.1(2)
88.6(2)
86.5(2)
88.2(4)
88.1(4)
87.8(4)
87.1(4)
87.5(2)
86.6(2)
88.3(2)
89.87(17)
87.5(16)[b]
176.3(5)
176.8(7)
179.7(6)
179.6(5)
178.6(5)
178.3(7)
178.0(7)
177.1(6)
175.2(6)
175.7(8)
179.2(8)
176.9(7)
175.8(6)
177.9(8)
179.2(8)
175.5(6)
135
87.4(12)[b]
176.5(5)
177.4(7)
177.9(6)
176.6(5)
179.4(6)
177.9(7)
177.0(8)
173.6(5)
174.7(5)
177.7(7)
179.6(8)
174.1(5)
176.9(5)
177.9(7)
177.6(7)
177.0(5)
111
87.8(5)[b]
174.7(10)
179.2(16)
175.3(15)
177.4(10)
172.2(11)
176.3(13)
173.9(11)
172.9(9)
178.2(10)
178.3(12)
178.1(13)
175.6(9)
175.7(11)
175.9(14)
177.7(13)
170.2(11)
138
Figure 3. Thermal ellipsoid plots (50% probability) of the molecular
structures of the Pt4C16 complexes 4a (top) and 4b·2CH2Cl2 (bottom).
Solvate molecules have been omitted.
value as measured from the 31P NMR spectrum (2200 Hz). Thus,
there must be a low energy pathway by which the platinum
corners in puckered conformations can exchange, or a planar
ground state conformation in solution. These issues helped
prompt the computational investigation in the following
section.
7.812
7.789
7.785
7.772
10.144
9.735
7.798
7.786
7.813
7.790
10.710
10.582
7.790
7.784
7.817
7.773
10.745
10.434
Pt1À Pt4
Pt2À Pt3
Pt3À Pt4
Pt1À Pt3
Pt2À Pt4
[a] The atom numbers for 4b·2CH2Cl2 and 4b·3.44DMSO have been
changed from those in the CIF files to facilitate comparisons with 4a. [b]
This represents the standard deviation of the averaged values. [c] plane/
plane angle.
Computations: Conformational and constitutional equilibria
Insight was sought regarding a number of properties of the
Pt4C16 complexes. The first concerned structure. Earlier compu-
tational investigations have nicely modeled features associated
with linear Pt(C�C)nPt segments,[25] so the edge units were not
of particular concern. However, a rationale for the variable
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Table 5. Views of the puckered hinge like Pt4C16 cores of 4a (middle) and 4b (bottom), and plane/plane angles ( ) and platinumÀ platinum distances (Å) in
these and related complexes.
Complex
Pt1À Pt2À Pt3 vs. Pt1À Pt4À Pt3
Pt1À Pt2
Pt1À Pt4
Pt2À Pt3
Pt3À Pt4
Pt1À Pt3
Pt2À Pt4
4a[a]
111
138
135
180
176
125
7.812
7.798
7.790
7.811
7.779
7.775
7.789
7.786
7.784
7.829
7.789
7.776
7.785
7.813
7.817
7.829
7.726
7.776
7.772
7.790
7.773
7.811
7.782
7.775
10.144
10.710
10.745
11.502
11.265
10.726
9.735
[a]
4b·2CH2Cl2
10.582
10.434
10.597
10.703
9.972
4b·3.44DMSO[a]
IV-iii’[b]
IV-iii’[b]
IV-iv’[c]
[a] These complexes contain additional solvent molecules that could not be refined; see text. [b] These data are for two different solvates of IV-iii’.[5b] [c] These
data correspond to a solvate.[5b]
planar (~square) and puckered (skew rhombus) Pt4C16 con-
formations exhibited by the six structures in Table 5 was
desired.
modest barrier calculated (ca. 14 kcal/mol) is consistent with
the 195Pt NMR data for 4a.
Two types of byproducts can be conceptualized from
Schemes 2 and 5. For one, the pairwise Sonogashira/Hagihara
condensations would be allowed to further propagate prior to
ring closure. This leads to higher homologs such as Pt6C24 or
Pt8C32 species, all with even numbers of platinum atoms. For
the other, there would be a redistribution mechanism that
enables macrocycles with both even and odd numbers of
platinum atoms to form. In supramolecular and self-assembly
phenomena, equilibria between three- and four-sided polygon
like species are quite common.[27]
Accordingly, analogous DFT techniques were applied to
obtain the structures and energies of the corresponding Pt3C12
(7’a) and Pt5C20 (8’a) complexes, further properties of which
were sought for various purposes below. Unsurprisingly, these
were found to exhibit triangular and half chair geometries, as
shown in Figure 5 (bottom) or (in a larger format) Figure S1. The
latter featured four approximately coplanar platinum atoms
(average/maximum deviation from the least squares plane:
0.565/0.650 Å), with the fifth “headrest” atom significantly
displaced from the plane (5.681 Å). It was then a simple matter
to calculate the energies associated with the isodesmic
equilibria depicted in Figure 5 (top).
Although the authors have considerable computational
resources available that have sufficed for many types of large
molecules,[26] due to the four platinum atoms in 4a it proved
necessary to study a model compound in which the PPh groups
were replaced by PMe groups (denoted 4’a). Accordingly, a
number of DFT conditions (functional, basis sets, solvents, etc.)
were applied to the planar and puckered forms of 4’a from
their fully optimized structures in the CAMÀ B3LYP/6-311G(d)
level of theory in the gas phase. Subsequent frequency analyses
confirmed that both were local minima. The angle between the
°
“hinge leaves” of the latter was 142 (Pt1À Pt3 10.370 Å, Pt2À Pt4
10.339 Å). However, as shown in Figure 4 (bottom), comparable
energy ranges were found, viewed over all of the theoretical
models employed.
This suggests that crystal packing forces may also play roles
in the structures in Table 5, as further supported in the
discussion section. Transition states were also probed, but in
order to realize a converged structure, it was necessary to
replace all phosphine ligands by PH3 (4“). This exhibited the
intuitively expected intermediate geometry with the imaginary
vibration displacing two diagonal corners upwards, with the
other two moving downwards (Figure 4, top). For this stripped
down model, the puckered conformation was very slightly
more stable, but the value (À 0.3 kcal/mol) was well within the
range viewed as ”experimental error“ for DFT calculations. The
That on the left shows the conversion of 3·4’a to 4·7’a to
be endergonic, with a ΔGgas of 8.4 kcal/mol. Such equilibria are
favored entropically, and in some cases the rigidity of the edge
units and/or ring strain in the smaller macrocycle play
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Figure 4. Limiting geometries of the model compounds 4’a (PMe in place of PPh of 4a) and 4“ (2PH3 in place of each diphosphine of 4a), and the intervening
transition state for the latter.
Figure 5. ΔGgas values, computed at the CAMÀ B3LYP/6-311G(d) level of theory, associated with hypothetical isodesmic equilibria involving 4’a, 7’a, and 8’a
(top), and the corresponding structures (bottom).
important roles.[27d] Alternatively, the disproportionation of
2·4’a to a 1:1 mixture of 7’a and 8’a can be considered.
Apropos to the presumably reduced strain in 8’a vs. 7’a, this
equilibrium is less endergonic, with a ΔGgas of 6.0 kcal/mol.
Computations: Electronic and electrostatic properties
Special electronic properties are associated with a host of fully
conjugated cyclic unsaturated compounds, and often analogs
in which the conjugation is seemingly interrupted. Thus,
simulated UV-visible data were sought. Towards this end, TD-
DFT calculations were set up for 4’a and the corresponding
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monoplatinum bis(butadiynyl) complex 3’a. The computed
spectra are shown in Figure 6 (middle) and a full list of
electronic transitions is provided in Table S3. Figure 6 is clearly
in good qualitative agreement with the experimental spectra in
Figure 2.[28] Note the marked red shifts and enhanced intensities
for 4’a as compared to 3’a.
The Pt4C16 complex 4’a exhibits three particularly strong
absorptions at λ >300 nm, one of which (320 nm) presents
itself as a shoulder of a band at 310 nm. For the absorption at
348 nm, there are two underlying transitions with very close
energies. The longest wavelength band at 378 nm is not visible
under normal experimental conditions due to its low intensity.
All of these are predominantly ligand-to-metal charge transfer
(LMCT) absorptions, with electron density transferred from the
butadiyne segments to platinum based 6p-type orbitals. The
principal orbitals contributing to one of the transitions
represented in the 348 nm band are depicted in Figure 7. The
378 nm transition has mainly HOMO/LUMO character. These
orbitals are illustrated in Figure 7, and others are collected in
Figure S5.
In order to support certain generalizations (below), the TD-
DFT calculations were extended to the Pt3C12 and Pt5C20
complexes 7’a and 8’a (Figure 5). As can be gleaned from
Figure 6, the triplatinum complex 7’a exhibits fewer intense
bands than 4’a, with one of them markedly blue shifted to
266 nm. Two transitions contribute to each. In contrast, the
pentaplatinum complex 8’a exhibits slightly more bands than
4’a in the 300–380 nm region, generally of somewhat greater
intensities. However, the difference between 8’a and 4’a is not
as dramatic as that between 4’a and 7’a, suggesting that
geometric constraints may be beginning to limit the extent of
conjugation. For both 7’a and 8’a, the principal orbitals
involved for representative transitions are depicted in Figure 6,
and more extensive sets are provided in Figures S4 and S6.
Finally, electrostatic potential surface maps were computed
for 4’a, 7’a, and 8’a, as illustrated in Figure 8. Importantly, these
revealed a significant negative surface charge surrounding the
PtnC4n cores. This would naturally support the binding of
positively charged species near the centers of the macrocycles.
Indeed, the ammonium cations [H2NEt2]+ and [HNEt3]+ have
pronounced positive surface potentials, thus creating a “perfect
storm” for adduct formation. In accord with the ease of
purification of 3a–f from the byproduct [H2NEt2]+ ClÀ , no
pronounced negative surface potential is found for 3’a.
Figure 6. Computed UV-visible spectra (top, 7’a; middle, 3’a and 4’a;
bottom 8’a) and orbitals that are dominant contributors to selected
transitions.
Figure 7. The HOMO and LUMO of 4’a.
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Figure 8. Electrostatic potential surface maps of 7’a, 4’a, 8’a, and other relevant species.
Discussion
unsuccessful. As noted in Scheme 2, Bruce worked around this
problem by switching to platinum bis(triflate) building blocks
that could condense with bis(butadiynyl complexes using non-
nitrogenous anionic bases.[5b]
Syntheses and adducts of title complexes
This work has significantly expanded the availability of macro-
cyclic polygon like Pt4C16 complexes that feature identical
platinum(II) corners and butadiynediyl edges, and established
comparable energies for skew rhombus[1] and “square” geo-
metries. To our knowledge, such species are unknown with
other metals or polyynediyl linkers. However, some mixed
Pt2Pt’2C16 complexes with unlike platinum corners have been
reported.[5b,c] Otherwise the closest relatives would be the
tetragermanium or tetrasilicon adducts II-xvi or II-xix in
Scheme 1.[3a,d] Of course, platinum corners are ubiquitous in a
host of fascinating polygon like structures that stem from self-
assembly processes.[29,30]
The isolation of the title complexes 4a–f is severely
complicated by their high affinities for ammonium cation
byproducts derived from the Sonogashira/Hagihara coupling
reactions employed. Challenging crystallizations aside,[24] we
were unable to develop practical purification protocols that
removed these species. Our experiences parallel those of other
research groups. Bruce could isolate 1:1 adducts of IV-ii’, IV-iii’,
or IV-iv’ (Scheme 2) and [H2NEt2]+ TfO-, as evidenced by NMR
and IR spectroscopy, ions of the composition IV·[H2NEt2]+ in ESI
mass spectra, and microanalyses.[5b] When HNCy2 or HN(i-Pr)2
were used in place of HNEt2 with IV-ii’, mass spectra of the
partially characterized products gave analogous ions. Anderson
reported comparable data for IV-iv’ and [H2NEt2]+ ClÀ .[5c]
However, efforts to remove the ammonium ions were largely
The electrostatic potential surface maps in Figure 8 provide
insight regarding these purification issues. We had not antici-
pated such a pronounced concentration of negative charge
around the Pt4C16 core, although it was discovered later that
Nakamura had reported similar computational results for the
“triangle” I-iv (Scheme 1; R=OCH3) and the higher tris
(octatetraynediyl) homolog.[2g] There is no significant charge
concentration in complexes that model the corner environ-
ments, i.e., the bis(butadiynyl) complex 3’a in Figure 8, or in
diplatinum complexes with Pt(C�C)nPt units. These have
frequently been synthesized by Sonogashira/Hagihara method-
ologies without any subsequent purification difficulties. In any
case, the nature of the supramolecular bonding interactions
between the Pt4C16 complexes and the ammonium cations
awaits further study, for which crystal structures would be
helpful.
In phenomena that may be conceptually related, Lang[31]
has demonstrated that a variety of cis bis(alkynyl) or bis
(polyynyl) complexes can chelate to coinage metal fragments.
This affords “tweezer” complexes with two π-C�C linkages, as
exemplified by the titanium and platinum complexes 10–13 in
Figure 9. Similar species, such as the platinum complexes 14
and 15, have been characterized by Bruce.[5b] Bruce has also
obtained excellent evidence for adducts of IV-iii’ (Scheme 2)
-
with [Cu(NCMe)2]+ BF4- (two equiv/IV-iii’) and [Ag(NCMe)2]+ BF4
(four equiv/IV-iii’). These remain to be structurally characterized.
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Figure 9. Previously reported “tweezer” complexes.
Additional structural and electronic features
262, 270 (sh), 278 nm, and 295 nm. There are no additional or
shifted bands as the number of (C�C)2 edges are varied. Rather,
only the molar extinction coefficients increase, as would be
expected from an increasing number of non-interacting Ge-
(C�C)2Ge units. A parallel situation is found with the related
silicon compound II-xix and higher homologs.[3a]
Hence, the platinum corners in the title compounds provide
unique vectors for conjugation, creating an extended chromo-
phore with no counterpart in Scheme 1. The TD-DFT compu-
tations suggest that that Pt3C12 and Pt5C20 analogs behave
similarly. However, this should be extrapolated to higher
homologs with caution, as progressively greater deviations
from planarity would be expected, interfering with conjugation.
The only other transition metal containing species in Scheme 1
are I-xii and II-xii, which are technically carbocyclic but feature
dicobalt substituents at each corner.[4b] Here only a slight red
shift in the lowest energy band is apparent (370 vs. 381 nm)
with increased macrocycle size, as well as with trailing shoulders
(445/546 vs. 453/560 nm).
In all four new crystal structures herein, the six membered
diphosphine chelate rings are not planar, but adopt half chair
conformations. This is most easily visualized for 3a·CH2Cl2 in
Figure 1, which has only one such chelate. The five atom
CH2À PÀ PtÀ PÀ CH2 moiety is essentially planar, with the max-
imum/average deviation from the least squares plane being
0.096/0.060 Å. In contrast, the quaternary C(CH3)2 or “headrest”
carbon atom sits 0.689 Å above this plane.
The same analysis can be applied to 4a, 4b·2CH2Cl2, and
4b·3.44DMSO.
The
average
deviations
from
the
CH2À PÀ PtÀ PÀ CH2 least squares plane (taken over four chelate
rings) are 0.101 Å, 0.028 Å, and 0.033 Å, respectively. The
distances of the four quaternary carbon atoms in 4a from this
plane (0.594–0.640 Å) are comparable to that in 3a. However,
the corresponding distances in 4b·2CH2Cl2, and 4b·3.44DMSO,
which feature larger geminal diethyl groups, are somewhat
greater (0.716–0.816 Å and 0.787–0.813 Å).
Interestingly, one other series of “squares” in Scheme 1, the
carbocycles II-xvii, have also been observed to exist in both
puckered (R=H, CH2OAc) and planar (R=CH2OH) conforma- Conclusion
tions in the crystalline state.[3c] This could be correlated with
slight differences in solid state UV-visible spectra, and was
attributed to crystal packing forces associated with hydrogen
bonding interactions. DFT calculations (R=CH2OH) indicated an
energy difference (ΔG, gas phase) of 1.92 kcal/mol favoring the
puckered form. Contrasting puckered vs. planar geometries
have also been found for two related macrocyclic tetraplatinum
alkynyl species, one of which was accessed via self-assembly.[30]
For each adduct, the equilibrium has been studied by DFT, and
analyzed in terms of electronic, mechanical, and electronic
strain.[30b]
This study has added to the platinum building blocks that can
be used to prepare macrocycles comprised of four platinum
corners and butadiynediyl edges. The new Pt4C16 systems
crystallize with puckered or skew rhombus conformations,[1] but
DFT calculations and other data suggest that planar or
puckered geometries are local minima differing only slightly in
energy. Thus, packing forces become important determinants
of solid state conformation.
These adducts are challenging to isolate in pure form. This
is attributed to the highly negative electrostatic potentials
surrounding the macrocycle cores, providing binding sites for
cationic byproducts (ammonium cations, Cu+). The Pt4C16
systems feature highly delocalized electronic structures, as
reflected by intense UV-visible bands that have no counterparts
in monoplatinum or diplatinum model compounds, and further
characterized by time dependent DFT calculations that define
the underlying transitions and orbitals involved. The longer
wavelength absorptions have dominant LMCT character. The
same holds for related Pt3C12 and Pt5C20 complexes, as assayed
A
wealth of data involving the electronic transitions
responsible for the bands in Figures 2 and 6 can be found in
the Supporting Information (Table S3 and Figures S3–S6). We
are not aware of other TD-DFT studies for any of the
compounds represented in Scheme 1. However, in some cases
the UV-visible data alone are instructive. For example, the
tetragermanium species II-xvi as well as each higher homolog
through the octagermanium species [Ph2Ge(C�C)2]8 has been
characterized.[3d] All of these compounds exhibit λmax near 248,
Chem. Eur. J. 2021, 27, 1–20
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Chemistry—A European Journal
(m), 2862 (m), 1435 (s), 1102 (s), 995 (m), 817 (m), 748 (s), 725 (s),
694 (s). MS:[37] MALDI+ (matrix DCTB+1% TFA), 754 ([2c – Cl]+,
100%).
by DFT. Equilibria involving conversions of Pt4C16 systems to
Pt3C12 analogs or a 1:1 Pt3C12/Pt5C20 mixture are endergonic.
This work provides a much improved foundation for the
pursuit of higher homologs with longer polynediyl segments
(e.g. Pt4C24 or Pt4C32 species).[9] Efforts directed at these targets,
as well as other novel carbon rich platinum complexes, will be
reported in due course.
(n-Dec2C(CH2PPh2)2)PtCl2 (2d): A Schlenk flask was charged with
cis/trans-(p-tol3P)2PtCl2 (2.135 g, 2.440 mmol),[20] 1d (1.689 g,
2.437 mmol), and CH2Cl2 (40 mL) with stirring. After 2 d, the solvent
was removed by rotary evaporation. The residue was washed with
Et2O (50 mL), water (50 mL), and hexanes (100 mL), and dried by oil
pump vacuum to give 2d as a white solid (2.198 g, 2.292 mmol,
°
°
94%), which yellowed at 190 C and liquefied at 235 C. Anal. Calcd.
for C47H66Cl2P2Pt (958.96): C, 58.87; H, 6.94; Found: C, 58.90; H, 6.81.
NMR (δ (ppm)): H (CDCl3) 8.03–7.86 (m, 8H, o to P), 7.53–7.42 (m,
Experimental Section
1
(Me2C(CH2PPh2)2)PtCl2 (2a): A Schlenk flask was charged with cis/
trans-(p-tol3P)2PtCl2 (1.003 g, 1.15 mmol),[20] Me2C(CH2PPh2)2 (1a;[15]
0.615 g, 1.40 mmol), and CH2Cl2 (20 mL) with stirring. After 24 h, the
solvent was removed by rotary evaporation. The residue was
washed with Et2O (100 mL), EtOH (100 mL), and hexanes (100 mL),
and dried by oil pump vacuum to give 2a as a white solid (0.705 g,
2
12H, m and p to P), 2.37 (d, JHP =8.3 Hz, 4H, PCH2), 1.34–0.55 (m,
42H, (CH2)9CH3); 13C{1H} (CD2Cl2) 134.2 (virtual t,[33] 2JCP =4.4 Hz, o to
P), 131.1 (s, p to P), 129.7 (m, J=70.4 Hz, J=7.3 Hz, i to P),[34] 128.4
(virtual t,[33] 3JCP =5.1 Hz, m to P), 40.8 (s, CH2), 40.3 (t, JCP =7.3 Hz,
2
C(CH2)4), 35.8 (t, JCP =20.6 Hz, PCH2),[35] 31.8 (s, CH2), 29.4 (s, CH2),
1
29.3 (s, CH2), 29.2 (s, CH2), 29.1 (s, CH2), 22.6 (s, CH2), 22.4 (s, CH2),
°
21.3 (s, CH2), 14.1 (s, CH3); 31P{1H} (CDCl3) À 2.6 (s, JPPt =3417 Hz).[36]
1
0.998 mmol, 87%), which slightly darkened at 250 C and blackened
°
IR (cmÀ 1, powder film): 2942 (s), 2854 (s), 1458 (w), 1435 (s), 1103 (s),
840 (m), 817 (m), 748 (s), 725 (s), 694 (s). MS:[37] MALDI+ (matrix
DCTB+1% TFA), 922 ([2d – Cl]+, 100%).
at 375 C. Anal. Calcd. for C29H30Cl2P2Pt (706.08): C, 49.30; H, 4.28;
Found: C, 47.84; H, 4.34.[32] NMR (δ (ppm), CD2Cl2): H 7.92–7.79 (m,
1
2
8H, o to P), 7.50–7.37 (m, 12H, m and p to P), 2.31 (d, JHP =9.7 Hz,
4H, PCH2), 0.55 (s, 6H, CH3); 13C{1H} 134.7 (virtual t,[33] 2JCP =5.6 Hz, o
to P), 131.9 (s, p to P), 129.3 (m, J=73.7 Hz, J=7.0 Hz, i to P),[34]
(Bn2C(CH2PPh2)2)PtCl2 (2e): A Schlenk flask was charged with cis/
trans-(p-tol3P)2PtCl2 (0.251 g, 0.287 mmol),[20] Bn2C(CH2PPh2)2 (1e;[16]
0.247 g, 0.417 mmol), and CH2Cl2 (20 mL) with stirring. After 18 h,
the solvent was removed by rotary evaporation. The residue was
washed with Et2O (700 mL) and hexanes (200 mL), and dried by oil
pump vacuum to give 2e as a white powder (0.183 g, 0.213 mmol,
129.0 (virtual t,[33] 3 CP =5.6 Hz, m to P), 35.4 (s, C(CH3)2), 32.3 (t, 1JCP
J =
8.7 Hz, PCH2),[35] 30.0 (s, CH3); 31P{1H} À 1.3 (s, 1JPPt =3431 Hz).[36] IR
(cmÀ 1, powder film): 2954 (w), 1481 (m), 1435 (s), 1103 (s), 840 (s),
802 (s), 748 (s), 694 (s). MS:[37] MALDI+ (matrix DCTB), 670 ([2aÀ Cl]+,
60%).
°
74%), which yellowed at 225 C. Anal. Calcd. for C41H38Cl2P2Pt
(858.68): C, 57.35; H, 4.46; Found: C, 57.45; H, 4.57. NMR (δ (ppm),
(Et2C(CH2PPh2)2)PtCl2 (2b): A Schlenk flask was charged with cis/
trans-(p-tol3P)2PtCl2 (1.127 g, 1.289 mmol),[20] Et2C(CH2PPh2)2 (2b;[15]
0.631 g, 1.346 mmol), and CH2Cl2 (30 mL) with stirring. After 24 h,
the solvent was removed by rotary evaporation. The residue was
washed with Et2O (110 mL), water (20 mL), and hexanes (90 mL),
and dried by oil pump vacuum to give 2b as a white solid (0.652 g,
1
CD2Cl2): H 7.65–7.20 (m, 30H, C6H5), 2.61 (s, 4H, CH2C6H5), 2.45 (d,
2JHP =7.9 Hz, 4H, PCH2); 13C{1H} 136.4 (s, i to CH2), 134.5 (virtual t,[33]
2JCP =4.6 Hz, o to P), 131.8 (s, p to P), 131.7 (s, m to CH2), 130.1 (m,
J=76.0 Hz, J=8.2 Hz, i to P),[34] 129.9 (s, o to CH2), 128.9 (virtual t,[33]
3JCP =4.0 Hz, m to P), 127.7 (s, p to CH2), 48.5 (t, 2JCP =6.4 Hz,
C(CH2)4), 42.7 (s, CH2C6H5), 31.3 (t, 1JCP =25.4 Hz, PCH2);[35] 31P{1H}
°
°
0.888 mmol, 69%), which yellowed at 230 C, browned at 305 C,
°
À 2.0 (s, JPPt =3376 Hz).[36] IR (ATR, cmÀ 1): 3024 (w), 2361 (s), 2160
1
and blackened at 355 C. Anal. Calcd. for C31H34Cl2P2Pt (734.54): C,
50.69; H, 4.67; Found: C, 49.38; H, 4.80.[32] NMR (δ (ppm), CDCl3): H
1
(m), 1435 (s), 1096 (s), 694 (s), 493 (s). MS:[37] MALDI+ (matrix DCTB),
822 ([2e – Cl]+, 100%).
7.86–7.98 (m, 8H, o to P), 7.39–7.50 (m, 12H, m and p to P), 2.35 (d,
2JHP =9.2 Hz, 4H, PCH2), 1.05 (q, 3JHH =6.9 Hz, 4H, CH2CH3), 0.29 (t,
3JHH =6.9 Hz, 6H, CH3); 13C{1H} 134.3 (virtual t,[33] 2JCP =4.9 Hz, o to P),
((p-tolCH2)2C(CH2PPh2)2)PtCl2 (2f): A Schlenk flask was charged
with cis/trans-(p-tol3P)2PtCl2 (0.522 g, 0.597 mmol),[20] 1f (0.518 g,
0.835 mmol), and CH2Cl2 (40 mL) with stirring. After 3 d, the solvent
was removed by rotary evaporation. The residue was washed with
Et2O (700 mL), and dried by oil pump vacuum to give 2f as a white
133.2 (s, p to P), 131.2 (m, J=75.3 Hz, J=7.2 Hz, i to P),[34] 128.5
(virtual t,[33] 2JCP =5.5 Hz, m to P), 50.1 (s, CH2CH3), 35.0 (t, JCP
=
1
2
23.4 Hz, PCH2),[35] 31.4 (t, JCP =6.3 Hz, C(CH2)4), 6.5 (s, CH3); 31P{1H}
À 2.5 (s, 1JPPt =3429 Hz).[36] IR (cmÀ 1, powder film): 1481 (w), 1435
(m), 1103 (m), 817 (w), 740 (m), 717 (w), 694 (s), 555 (m), 523 (m).
MS:[37] MALDI+ (matrix DCTB, THAP, or CHCA), 698 ([2b – Cl]+,
100%).
°
solid (0.451 g, 0.509 mmol, 85%), which yellowed at 275 C. Anal.
Calcd. for C43H42Cl2P2Pt (886.73): C, 58.24; H, 4.77; Found: C, 56.08; H,
4.77.[32] NMR (δ (ppm), CD2Cl2): H 7.62–7.55 (m, 8H, o to P), 7.49–
1
3
7.33 (m, 8H, m and p to P), 7.09 and 6.78 (2 d, JHH =8.0 Hz, 4H and
4H, C6H4), 2.56 (s, 4H, CH2C6H4), 2.42 (d, JHP =8.0 Hz, 4H, PCH2), 2.34
2
(n-Bu2C(CH2PPh2)2)PtCl2 (2c): A Schlenk flask was charged with cis/
trans-(p-tol3P)2PtCl2 (1.007 g, 1.151 mmol),[20] 1c (0.807 g,
1.54 mmol), and CH2Cl2 (30 mL) with stirring. After 2 d, the solvent
was removed by rotary evaporation. The residue was washed with
Et2O (110 mL), water (20 mL), and hexanes (90 mL), and dried by oil
pump vacuum to give 2c as a white solid (0.798 g, 1.01 mmol,
(s, 6H, CH3); 13C{1H} 136.9 (s, p to P), 133.9 (virtual t,[33] 2JCP =5.0 Hz, o
to P), 132.7 (s, m to CH2), 131.1 (s, i to CH2), 131.0 (s, o to CH2), 129.6
(m, J=70.1 Hz, J=6.9 Hz, i to P),[34] 129.1 (s, p to CH2), 128.3 (virtual
t,[33] 3JCP =6.2 Hz, m to P), 47.5 (t, 2JCP =6.0 Hz, C(CH2)4), 42.1 (s,
CH2C6H4), 30.3 (t, 1JCP =21.0 Hz, PCH2),[35] 20.7 (s, CH3); 31P{1H} À 2.0 (s,
1JPPt =3386 Hz).[36] IR (cmÀ 1, powder film): 3047 (w), 2361 (s), 1512
(w), 1435 (s), 794 (s), 733 (s), 602 (s). MS:[37] MALDI+ (matrix DCTB),
850 ([2f – Cl]+, 100%).
°
°
88%), which yellowed at 160 C, browned at 250 C, and liquefied at
°
295 C. Anal. Calcd. for C35H42Cl2P2Pt (790.65): C, 53.17; H, 5.35;
1
Found: C, 52.93; H, 5.31. NMR (δ (ppm)): H (CDCl3) 7.80–7.98 (m,
2
8H, o to P), 7.41–7.50 (m, 12H, m and p to P), 2.31 (d, JHP =9.0 Hz,
(Me2C(CH2PPh2)2)Pt((C�C)2H)2 (3a): A. A Schlenk flask was charged
with trans-(p-tol3P)2Pt((C�C)2H)2 (0.412 g, 0.456 mmol),[12b] 1a
(0.234 g, 0.531 mmol), and CH2Cl2 (20 mL) with stirring. After 48 h,
the solvent was removed and the residue was chromatographed on
a silica gel column (30×4.5 cm) eluted with 1:1 v/v CH2Cl2/hexanes.
The solvents were removed from the product containing fractions
by oil pump vacuum to give 3a as an off-white solid (0.316 g,
4H, PCH2), 0.82–0.98 (m, 4H, CH2CH2CH2CH3), 0.59–0.67 (m, 8H,
CH2CH2CH3), 0.52 (t, 3JHH =7.0 Hz, 6H, CH3); 13C{1H} (CD2Cl2) 133.9
(virtual t,[33] 2JCP =4.4 Hz, o to P), 130.8 (s, p to P), 129.0 (m, J=
71.3 Hz, J=6.0 Hz, i to P),[34] 127.9 (virtual t,[33] 3JCP =5.1 Hz, m to P),
1
2
40.5 (t, JCP =11.8 Hz, PCH2),[35] 39.8 (t, JCP =8.3 Hz, C(CH2)4), 28.0 (s,
CH2CH2CH2CH3), 24.1 (s, CH2CH2CH3), 22.1 (CH2CH3), 12.9 (s, CH3); 31P
1
{1H} (CDCl3) À 2.6 (s, JPPt =3419 Hz).[36] IR (cmÀ 1, powder film): 2931
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Chemistry—A European Journal
0.430 mmol, 94%). B. A Schlenk flask was charged with 2a (0.545 g,
0.771 mmol), CuI (0.0371 g, 0.195 mmol), and HNEt2 (30 mL) with
{1H} À 6.4 (s, 1JPPt =2225 Hz).[36] IR (cmÀ 1, powder film): 2931 (s), 2862
(s), 2152 (s, νC�C), 1435 (m), 1103 (m), 810 (m), 725 (s), 692 (s), 563
(s). MS:[37] MALDI+ (matrix DCTB+1% TFA), 856 ([3c+K]+, 100%).
°
stirring and cooled to À 42 C (CO2/acetonitrile). Then butadiyne
(1.773 g, 35.4 mmol in 44 mL THF)[38] was added. After 30 min, the
cold bath was removed. After 3 h, the solvents were removed and
the residue was chromatographed on a silica gel column (30×
4.5 cm) eluted with 1:1 v/v CH2Cl2/hexanes. The solvents were
removed from the product containing fractions by oil pump
vacuum to give 3a as an off-white solid (0.395 g, 0.538 mmol,
(n-Dec2C(CH2PPh2)2)Pt((C�C)2H)2 (3d): A. trans-(p-tol3P)2Pt((C�C)2H)2
(1.078 g, 1.195 mmol),[12b] 1d (0.830 g, 1.198 mmol), and CH2Cl2
(100 mL) were combined in a manner analogous to procedure A for
3a. An identical workup gave 3d as an off-white solid (0.631 g,
0.639 mmol, 54%). B. Complex 2d (0.633 g, 0.660 mmol), CuI
(0.0186 g, 0.0997 mmol), THF (50 mL), HNEt2 (50 mL), and butadiyne
(1.320 g, 26.37 mmol in 16 mL THF)[38] were combined in a manner
similar to procedure B for 3a (1 h with cold bath, then 4 more h).
An identical workup gave 3d as an off-white solid (0.426 g,
°
°
70%), which yellowed at 135 C and blackened at 165 C. Anal.
Calcd. for C37H32P2Pt (733.68): C, 60.57; H, 4.40; Found: C, 60.30; H,
1
4.63. NMR (δ (ppm), CDCl3): H 7.85–7.75 (m, 8H, o to P), 7.50–7.37
2
(m, 12H, m and p to P), 2.33 (d, JHP =10 Hz, 4H, PCH2), 1.64 (s, 2H,
°
0.432 mmol, 65%), which liquefied at 120 C and blackened at
�CH), 0.73 (s, 6H, CH3); 13C{1H} 133.9 (virtual t,[33] 2JCP =5.2 Hz, o to P),
°
140 C. Anal. Calcd. for C55H68P2Pt (986.16): C, 66.99; H, 6.95; Found:
C, 66.89; H, 7.02. NMR (δ (ppm)): H (CDCl3) 7.82–7.71 (m, 8H, o to
131.4 (s, p to P), 130.9 (m, J=68.8 Hz, J=8.2 Hz, i to P),[34] 128.5
1
(virtual t,[33] 2JCP =6.4 Hz, m to P), 95.4 (dd, 2JCP =146.6 Hz, JCP
=
2
P), 7.44–7.35 (m, 12H, m and p to P), 2.30 (d, 1JHP =9.1 Hz, 4H, PCH2),
1.55 (s, 2H, �CH), 1.21–0.87 (m, 46H, (CH2)9CH3); 13C{1H} (CD2Cl2)
134.0 (virtual t,[33] 2JCP =5.8 Hz, o to P), 131.4 (m, J=68.5 Hz, J=
9.0 Hz, i to P),[34] 130.7 (s, p to P), 128.3 (virtual t,[33] 3JCP =5.3 Hz, m
to P), 95.8 (dd, 2JCP =147.2 Hz, 2JCP =19.0 Hz, PtC�C), 91.5 (m, J=
17.9 Hz, PtC�C), 71.8 (s, C�CH), 61.1 (s, �CH), 41.1 (s, CH2), 40.5 (t,
2JCP =7.1 Hz, C(CH2)4), 34.6 (t, 1JCP =18.2 Hz, PCH2),[35] 31.8 (s, CH2),
29.5 (s, CH2), 29.4 (s, CH2), 29.2 (s, CH2), 29.1 (s, CH2), 22.6 (s, CH2),
18.2 Hz, PtC�C), 91.9 (m, J=18.4 Hz, PtC�C), 71.7 (s, C�CH), 61.6 (s,
1
2
�CH), 37.3 (t, JCP =18.9 Hz, PCH2),[35] 33.1 (t, JCP =8.3 Hz, C(CH2)4),
21.4 (s, CH3); 31P{1H} À 4.9 (s, 1JPPt =2224 Hz).[36] IR (cmÀ 1, powder
film): 3299 (s), 2960 (s), 2922 (s), 2146 (s, νC�C), 1918 (m). MS:[37]
MALDI+ (matrix THAP), 772 ([3a+K]+, 30%), 756 ([3a+Na]+,
100%), 734 ([3a+H]+, 90%).
(Et2C(CH2PPh2)2)Pt((C�C)2H)2 (3b): A. trans-(p-tol3P)2Pt((C�C)2H)2
(1.037 g, 1.149 mmol),[12b] 1b (0.535 g, 1.141 mmol), and CH2Cl2
(100 mL) were combined in a manner analogous to procedure A for
3a. An identical workup gave 3b as an off-white solid (0.609 g,
0.799 mmol, 70%). B. Complex 2b (0.306 g, 0.417 mmol), CuI
(0.0223 g, 0.117 mmol), HNEt2 (13 mL), and butadiyne (0.581 g,
11.60 mmol in 13.4 mL THF)[38] were combined in a manner
analogous to procedure B for 3a. An identical workup gave 3b as
an off-white solid (0.276 g, 0.362 mmol, 87%), which yellowed at
22.5 (s, CH2), 21.3 (s, CH2), 14.0 (s, CH3); 31P{1H} (CDCl3) À 6.6 (s, 1JPPt
=
2221 Hz).[36] IR (cmÀ 1, powder film): 3294 (m), 2924 (s), 2854 (s), 2152
(s, νC�C), 1458 (m), 1435 (s), 1103 (s), 825 (m), 810 (m), 725 (s), 695
(s). MS (MALDI+, matrix DCTB+1% TFA):[37] 1048 ([3d+Cu]+,
100%).
(Bn2C(CH2PPh2)2)Pt((C�C)2H)2
(3e).
trans-(p-tol3P)2Pt((C�C)2H)2
(0.202 g, 0.224 mmol),[12b] 1e (0.279 g, 0.471 mmol), and CH2Cl2
(20 mL) were combined in a manner analogous to procedure A for
3a. An identical workup gave 3e as an off-white solid (0.175 g,
°
°
°
114 C, darkened at 127 C, and blackened at 142 C. Anal. Calcd. for
C39H36P2Pt (761.73): C, 61.49; H, 4.76; Found: C, 61.19; H, 4.71. NMR
°
°
0.197 mmol, 88%), which yellowed at 124 C, blackened at 141 C
1
(δ (ppm), CDCl3): H 7.89–7.74 (m, 8H, o to P), 7.49–7.37 (m, 12H, m
°
and liquefied at 248 C. Anal. Calcd. for C49H40P2Pt (885.87): C, 66.43;
2
and p to P), 2.32 (d, JHP =7.0 Hz, 4H, PCH2), 1.63 (s, 2H, �CH), 1.14
1
H, 4.55; Found: C, 64.30; H, 4.84.[32] NMR (δ (ppm), CDCl3): H 7.47–
3
3
(q, JHH =7.4 Hz, 4H, CH2CH3), 0.33 (t, JHH =7.4 Hz, 6H, CH3); 13C{1H}
134.1 (virtual t,[33] 2JCP =6.0 Hz, o to P), 131.5 (m, J=68.3 Hz, J=
8.9 Hz, i to P),[34] 130.8 (s, p to P), 128.5 (virtual t,[33] 2JCP =5.5 Hz, m
to P), 95.7 (dd, 2JCP =149.0 Hz, 2JCP =20.0 Hz, PtC�C), 91.7 (m, J=
17.8 Hz, PtC�C), 71.8 (s, C�CH), 61.3 (s, �CH), 41.5 (s, CH2CH3), 33.8
1
7.90 (m, 30H, C6H5), 2.72 (s, 4H, CH2C6H5), 2.36 (d, JHP =6.6 Hz, 4H,
PCH2), 1.70 (s, 2H, �CH); 13C{1H} 136.4 (s, i to CH2), 133.7 (virtual t,[33]
2JCP =5.6 Hz, o to P), 131.7 (s, p to P), 130.9 (m, J=86.7 Hz, J=
10.2 Hz, i to P),[34] 130.8 (s, m to CH2), 129.6 (s, o to CH2), 128.6 (s, m
to P),[39] 127.2 (s, p to CH2), 96.1 (dd, JCP =145.6 Hz, JCP =22.1 Hz,
2
2
(t, JCP =18.8 Hz, PCH2),[35] 32.4 (t, JCP =8.6 Hz, C(CH2)4), 6.7 (s, CH3);
1
2
PtC�C), 92.8 (m, J=18.1 Hz, PtC�C), 71.8 (s, C�CH), 61.9 (s, �CH),
31P{1H} À 5.6 (s, JPPt =2257 Hz).[36] IR (cmÀ 1, powder film): 3047 (m),
1
2
1
48.9 (t, JCP =6.7 Hz, C(CH2)4), 42.7 (s, CH2C6H5), 28.9 (t, JCP =18.1 Hz,
PCH2);[35] 31P{1H} À 4.8 (s, 1JPPt =2192 Hz).[36] IR (cmÀ 1, powder film):
3294 (m), 2152 (s, νC�C), 2090 (w), 1485 (m), 1435 (s), 1095 (s), 810
(w), 740 (s), 694 (s). MS:[37] MALDI+ (matrix DCTB), 976 ([3e+Cu]+,
60%).
2962 (m), 2191 (m, νC�C), 1435 (s), 1381 (m), 1095 (s), 925 (m), 825
(m), 740 (s). MS:[37] MALDI+ (matrix CHCA), 784 ([3b+Na]+, 50%),
762 ([3b+H]+, 50%), 712 ([3b – (C�C)2H]+, 50%).
(n-Bu2C(CH2PPh2)2)Pt((C�C)2H)2 (3c): A. trans-(p-tol3P)2Pt((C�C)2H)2
(0.450 g, 0.499 mmol),[12b] 1c (0.268 g, 0.510 mmol), and CH2Cl2
(60 mL) were combined in a manner analogous to procedure A for
3a. An identical workup gave 3c as an off-white solid (0.394 g,
0.481 mmol, 97%). B. Complex 2c (0.497 g, 0.628 mmol), CuI
(0.0362 g, 0.190 mmol), HNEt2 (20 mL), and butadiyne (0.943 g,
((p-tolCH2)2C(CH2PPh2)2)Pt((C�C)2H)2 (3f): trans-(p-tol3P)2Pt((C�C)2H)2
(0.326 g, 0.361 mmol),[12b] 1f (0.430 g, 0.693 mmol), and CH2Cl2 (40 mL)
were combined in a manner analogous to procedure A for 3a. An
identical workup gave 3f as an off-white solid (0.286 g, 0.331 mmol,
°
°
87%), which yellowed at 124 C, blackened at 143 C and liquefied at
18.83 mmol in 22 mL THF)[38] were combined in
a manner
°
248 C. Anal. Calcd. for C51H44P2Pt (913.93): C, 67.02; H, 4.85; Found: C,
analogous to procedure B for 3a. An identical workup gave 3c as
an off-white solid (0.351 g, 0.429 mmol, 68%), which yellowed at
1
67.03; H, 4.90. NMR (δ (ppm), CDCl3): H 7.43–7.36 (m, 8H, o to P),
7.34–7.18 (m, 12H, m and p to P), 7.14 and 6.96 (2 d, 4H and 4H, 3JHH
=
°
°
129 C and blackened at 139 C. Anal. Calcd. for C43H44P2Pt (817.84):
C, 63.15; H, 5.42; Found: C, 63.17; H, 5.43. NMR (δ (ppm), CDCl3): H
7.3 Hz, C6H4), 2.68 (4H, s, CH2C6H4), 2.44–2.35 (m, 10H, CH3 and PCH2),
1
2
1.72 (s, 2H, �CH); 13C{1H} 137.0 (s, m to CH2), 133.8 (virtual t,[33] JCP
=
7.75–7.88 (m, 8H, o to P), 7.37–7.47 (m, 12H, m and p to P), 2.29 (d,
1JHP =7.2 Hz, 4H, PCH2), 1.56 (s, 2H, �CH), 1.05–0.95 (m, 4H,
6.2 Hz, o to P), 133.3 (s, p to P), 131.6 (s, i to CH2), 131.6, (m, J=69.9 Hz,
J=10.0 Hz, i to P),[34] 131.3 (s, o to CH2), 130.8 (s, p to CH2), 128.5
3
CH2CH2CH2CH3), 0.76–0.67 (m, 8H, CH2CH2CH3), 0.52 (t, JHH =7.3 Hz,
2
(virtual t,[33] 3JCP =5.0 Hz, m to P), 96.3 (dd, 2JCP =146.4 Hz, JCP
=
6H, CH3); 13C{1H} 134.1 (virtual t,[33] 2JCP =5.7 Hz, o to P), 130.9 (s, p to
19.4 Hz, PtC�C), 92.7 (m, J=18.4 Hz, PtC�C),[40] 71.9 (s, PtC�CC), 61.9 (s,
P), 129.2 (m, J=68.2 Hz, J=8.7 Hz, i to P),[34] 128.5 (virtual t,[33] JCP
=
3
2
�CH), 48.5 (t, 2JCP =6.1 Hz, C(CH2)4), 42.7 (s, CH2C6H4), 28.8 (t, JCP
=
2
2
5.4 Hz, m to P), 96.1 (dd, JCP =148.0 Hz, JCP =19.2 Hz, PtC�C), 91.6
19.7 Hz, PCH2),[35] 21.2 (s, CH3); 31P{1H} À 3.3 (s, 1JPPt =2196 Hz).[36] IR
(cmÀ 1, powder film): 3045 (w), 2908 (w), 2152 (s, νC�C), 1512 (w), 1481
(w), 1435 (s), 1095 (s), 802 (s), 799 (m), 740 (s), 686 (s). MS:[37] MALDI+
2
(m, J=18.2 Hz, PtC�C), 72.0 (s, C�CH), 61.2 (s, �CH), 40.6 (t, JCP
=
6.8 Hz, C(CH2)4), 34.9 (t, 1JCP =19.0 Hz, PCH2),[35] 24.7 (s,
CH2CH2CH2CH3), 22.7 (s, CH2CH2CH3), 22.1 (CH2CH3), 13.7 (s, CH3); 31P
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Chemistry—A European Journal
(matrix THAP), 952 ([3f+K]+, 30%), 936 ([3f+Na]+, 90%), 914 ([3f+
[(Et2C(CH2PPh2)2)[PKt(C�C)2K]4 (4b): A. A Schlenk flask was charged
with 2b (0.318 g, 0.433 mmol), 3b (0.331 g, 0.434 mmol), THF
(200 mL), HNEt2 (75 mL), and CuI (0.0165 g, 0.0866 mmol) with
H]+, 100%).
[(Me2C(CH2PPh2)2)[PKt(C�C)2K]4 (4a): A. A Schlenk flask was charged
with 2a (0.481 g, 0.692 mmol), 3a (0.503 g, 0.686 mmol), THF
(300 mL), HNEt2 (120 mL), and CuI (0.0259 g, 0.136 mmol) with
°
stirring and heated to 55 C. After 3 d, the precipitate was isolated
by filtration, washed with Et2O (500 mL) and hexanes (500 mL), and
dried by oil pump vacuum (rt, 20 h) to give 4b admixed with
1.0 equiv. [H2NEt2]+ ClÀ as a yellow solid (0.281 g, 0.0952 mmol,
°
stirring and heated to 55 C. After 3 d, the precipitate was isolated
by filtration, washed with Et2O (300 mL) and hexanes (300 mL), and
dried by oil pump vacuum (rt, 20 h) to give 4a admixed with
2.0 equiv. of [H2NEt2]+ ClÀ as a green solid (0.833 g, 0.282 mmol,
82% based upon the formula weight of 4a·([H2NEt2]+ ClÀ )2). The
1
44% based upon the formula weight of 4b·[H2NEt2]+ ClÀ ). The H
and 13C{1H} NMR spectra (see Supporting Information) did not show
1
detectable impurities. NMR (δ (ppm), CD2Cl2): H 7.73–7.60 (m, 32H,
3
3
m to P), 7.29 (t, JHH =7.4 Hz, 16H, p to P), 7.16 (t, JHH =7.6 Hz, 32H,
°
sample was kept under vacuum at 90 C (20 h), but was recovered
o to P), 3.47 (br s, 4H, [H2N(CH2CH3)2]+), 2.27 (d, JHP =9.0 Hz, 16H,
2
unchanged. The 1H and 13C{1H} NMR spectra (see Supporting
Information) showed minor impurities. Anal. Calcd. for
PCH2), 1.35 (t, 3JHH =7.2 Hz, 6H, [H2N(CH2CH3)2]+), 1.10 (q, JHH
=
3
7.3 Hz, 16H, CH2CH3), 0.25 (t, JHH =7.3 Hz, 24H, CH3); 13C{1H} 134.3
(virtual t,[33] 2JCP =4.9 Hz, o to P), 133.0 (m, J=58.2 Hz, J=8.2 Hz, i to
P), 130.5 (s, p to P), 128.3 (virtual t,[33] 3JCP =4.7 Hz, m to P), 96.7 (m,
J=23.2 Hz, PtC�C), 93.2 (dd, 2JCP =137.3 Hz, 2JCP =29.6 Hz, PtC�C),
45.1 (s, [H2N(CH2CH3)2]+), 41.8 (s, CH2CH3), 34.0 (t, 1JCP =17.9 Hz,
3
C
140H144Cl2N2P8Pt4 (2953.73): C, 56.93; H, 4.91; N, 0.95; Cl, 2.40;
Found: C, 53.31; H, 4.82; N, 0.96; Cl, 2.53.[32] NMR (δ (ppm), CD2Cl2):
1H 7.72–7.56 (m, 32H, m to P), 7.28 (t, 3JHH =7.3 Hz, 16H, p to P), 7.16
3
3
(t, JHH =7.1 Hz, 32H, o to P), 3.21 (q, JHH =7.4 Hz, 8H, [H2N(CH2CH3)
2]+), 2.32–2.21 (m, 16H, PCH2), 1.35 (t, 3JHH =7.2 Hz, 12H, [H2N
PCH2), 32.4 (t, JCP =6.5 Hz, C(CH2)4), 12.0 (s, [H2N(CH2CH3)2]+), 6.6 (s,
2
(CH2CH3)2]+), 0.65 (s, 24H, CH3); 13C{1H} 134.2 (virtual t,[33] JCP
=
2
CH3); 31P{1H} À 7.0 (s, 1JPPt =2230 Hz).[36] MS:[37] ESI+, 2920.8305 ([4b+
H2NEt2]+ (calc. 2919.8112), 25%), 1432.3775 ([4b+H+NH4]2+ (calc.
1432.3780), 100%).
5.2 Hz, o to P), 132.7 (m, J=68.8 Hz, J=8.4 Hz, i to P), 130.7 (s, p to
P), 128.4 (virtual t,[33] 3JCP =5.3 Hz, m to P), 96.7 (m, J=18.9 Hz,
2
2
PtC�C), 91.8 (dd, JCP =148.2 Hz, JCP =10.6 Hz, PtC�C), 43.9 (s, [H2N
(CH2CH3)2]+), 37.5 (t, 2JCP =16.6 Hz, C(CH2)4), 36.2 (s, CH3), 32.9 (t,
B. A Schlenk flask was charged with 2b (0.248 g, 0.337 mmol), 3b
(0.257 g, 0.337 mmol), THF (150 mL), HNEt2 (60 mL), and CuI
1
1JCP =7.3 Hz, PCH2), 12.0 (s, [H2N(CH2CH3)2]+); 31P{1H} À 5.5 (s, JPPt
=
2200 Hz);[36] 195Pt À 3339 (t, 1JPtP =2215 Hz). MS:[37] ESI+, 2807.7068
([4a+H2NEt2]+ (calc. 2807.6860), 40%), 1376.3172 ([4a+H+NH4]2+
(calc. 1376.3154), 100%); MALDI+ (matrix DCTB), 2797 ([4a+Cu]+,
100%), 2733 ([4a+H]+, 90%).
(0.0115 g, 0.0604 mmol) with stirring and heated to 55 C. After 3 d,
°
the solvents were removed by rotary evaporation, and water
(20 mL) was added. The mixture was extracted with CH2Cl2 (50 mL).
The extract was dried (MgSO4). The solvent was removed by rotary
evaporation. The residue was washed with THF (10 mL) and dried
by oil pump vacuum to give crude 4b as a tan solid (0.249 g,
B. A Schlenk flask was charged with 2a (0.292 g, 0.413 mmol), 3a
(0.304 g, 0.414 mmol), THF (150 mL), HNEt2 (60 mL), and CuI
°
°
0.0875 mmol, 52%), which yellowed at 140 C, browned at 174 C,
°
(0.0079 g, 0.041 mmol) with stirring and heated to 55 C. After 3 d,
1
°
°
blackened at 197 C, and liquefied at 263 C. In multiple runs, the H
NMR spectra showed some impurities and variable amounts of
[H2NEt2]+ ClÀ (up to ca. 1 equiv). The 31P{1H} NMR “purity” was
>96%. Thin layer chromatography was carried out using 0.0578 g
of sample as described for 4a. The tan band was worked up to give
4b admixed with 2.0 equiv. of [HNEt3]+ ClÀ (0.0173 g,
0.00554 mmol based upon the formula weight of 4b·([HNEt3]+
ClÀ )2; 0.0746 g, 0.0239 mmol or 14% after applying a 0.2492/0.0578
scale factor for the portion chromatographed). The 31P{1H} NMR
spectrum showed a single signal (>98% purity by this criterion).
the solvents were removed by rotary evaporation, and water
(150 mL) was added. The mixture was extracted with CH2Cl2 (3×
100 mL). The extracts were dried (MgSO4). The solvent was removed
by oil pump vacuum to give crude 4a as a cream colored solid
°
(0.500 g, ca. 0.183 mmol, ca. 89%), which darkened at 160 C and
1
°
blackened at 187 C. The H NMR spectrum showed some impurities
including [H2NEt2]+ ClÀ (ca. 0.5 equiv) but the 31P{1H} NMR “purity”
was >96%. Upon attempted thin layer chromatography, no
material moved from the origin (silica gel, alumina; CH2Cl2, CHCl3,
EtOAc, MeOH eluents). When a silica gel plate (loaded with
0.0371 g of sample) was eluted with 95:5 v/v CH2Cl2/NEt3, a faint
yellow band was evident. NMR analysis of a 95:5 v/v CH2Cl2/NEt3
extract showed a multitude of products. A slower moving tan band
was similarly extracted (no material desorbed with CH2Cl2 alone).
The solvent was removed by rotary evaporation and oil pump
vacuum to give a tan solid that a 1H NMR spectrum showed was 4a
admixed with 2.0 equiv. of [HNEt3]+ ClÀ (0.0177 g, 0.00589 mmol
based upon the formula weight of 4a·([HNEt3]+ ClÀ )2; 0.2386 g,
0.0793 mmol or 38% after applying a 0.5001/0.0371 scale factor for
the portion chromatographed). The 31P{1H} NMR spectrum showed
1
NMR (500 MHz, δ (ppm), CD2Cl2): H 7.66 (s, 32H, m to P), 7.28 (t,
3JHH =7.5 Hz, 16H, p to P), 7.14 (t, JHH =7.1 Hz, 32H, o to P), 2.98 (q,
3
3JHH =7.3 Hz, 12H, [HN(CH2CH3)3]+), 2.26 (d, JHP =8.8 Hz, 16H, PCH2),
2
1.27 (t, 3JHH =7.3 Hz, 18H, [HN(CH2CH3)3]+), 1.08 (m, 16H, CH2CH3),
0.23 (br s, 24H, CH3); 31P{1H} À 7.4 (s, 1JPPt =2196 Hz).[36] IR (cmÀ 1
,
powder film): 3047 (m), 2962 (w), 2191 (m, νC�C), 1435 (s), 1095 (s),
925 (m), 825 (m), 740 (s), 694 (s). MS:[37] MALDI+ (matrix DCTB), 2845
([4b+H]+, 100%).
[(n-Bu2C(CH2PPh2)2)PKt(C�C)2K]4 (4c): A. A Schlenk flask was charged
with 2c (0.413 g, 0.522 mmol), 3c (0.426 g, 0.521 mmol), THF
(260 mL), HNEt2 (100 mL), and CuI (0.030 g, 0.156 mmol) with
1
a single signal (>98% “purity”). NMR (δ (ppm), CD2Cl2): H 7.64 (s,
3
3
°
32H, m to P), 7.26 (t, JHH =7.2 Hz, 16H, p to P), 7.13 (t, JHH =7.2 Hz,
32H, o to P), 3.03 (q, 3JHH =7.3 Hz, 12H, [HN(CH2CH3)3]+), 2.26 (d,
stirring and heated to 55 C. After 5 d, the reaction was concen-
trated to ca. 15 mL and the solution was added to rapidly stirring
cold hexanes. The precipitate was isolated by filtration, washed
with H2O (400 mL), Et2O (600 mL) and hexanes (600 mL), and dried
by oil pump vacuum (rt, 20 h) to give 4c admixed with 1.5 equiv.
[H2NEt2]+ ClÀ as a tan solid (0.652 g, 0.202 mmol, 77% based upon
2JHP =8.6 Hz, 16H, PCH2), 1.33 (t, JHH =7.3 Hz, 18H, [HN(CH2CH3)3]+),
3
0.63 (s, 24H, CH3); 13C{1H} 134.4 (virtual t,[33] 2JCP =4.7 Hz, o to P),
133.0 (m, J=66.6 Hz, J=8.4 Hz, i to P), 130.5 (s, p to P), 128.4
(virtual t,[33] 3JCP =5.5 Hz, m to P), 97.0 (m, J=18.6 Hz, PtC�C), 92.6
(dd, JCP =147.7 Hz, JCP =21.0 Hz, PtC�C), 46.51 (s, [HN(CH2CH3)3]+),
the formula weight 4c·([H2NEt2]+ ClÀ )1.5), which blackened at
2
2
2
1
157 C, and liquefied at 181 C. The H and 13C{1H} NMR spectra (see
°
°
37.6 (t, JCP =17.8 Hz, C(CH2)4), 36.2 (s, CH3), 32.8 (s, PCH2), 9.03 (s,
[HN(CH2CH3)3]+); 31P{1H} À 5.7 (s, JPPt =2195 Hz).[36] IR (cmÀ 1, powder
Supporting Information) showed minor impurities. NMR (δ (ppm),
CD2Cl2): H 7.66 (t, JHH =8.5 Hz, 32H, m to P), 7.29 (t, JHH =7.3 Hz,
1
1
3
3
film): 3047 (w), 2955 (w), 2150 (w, νC�C), 1550 (m), 1433 (s), 1261 (w),
1150 (s), 833 (m), 806 (s). MS:[37] MALDI+ (matrix DCTB), 2733 ([4a+
H]+, 100%).
16H,
p to P), 7.22–7.10 (m, 32H, o to P), 3.14 (br s, 6H,
[H2N(CH2CH3)2]+), 2.29 (d, 2JHP =8.7 Hz, 16H, PCH2), 1.27 (br s, 9H,
[H2N(CH2CH3)2]+), 0.95 (d, 3JHH =6.5 Hz, 16H, CH2CH2CH2CH3), 0.67
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Chemistry—A European Journal
1
(m, 32H, CH2CH2CH3), 0.54 (t, 3JHH =6.7 Hz, 24H, CH3); 13C{1H} 134.2 (s,
[H2NEt2]+ ClÀ was not quantified. NMR (δ (ppm), CDCl3): H 7.32–
3
o to P), 132.7 (m, J=58.6 Hz, J=8.0 Hz, i to P), 130.3 (s, p to P),
7.27 (m, 32H, m to P), 7.15–7.06 (m, 16H, p to P), 7.03 (d, JHH
7.2 Hz, 16H, C6H4), 6.96–6.93 (m, 32H, o to P), 6.84 (d, JHH =7.2 Hz,
16H, C6H4), 2.56 (s, 16H, CH2C6H4), 2.35 (s, 24H, CH3), 2.27 (d, JHP =
=
2
3
128.1 (s, m to P), 96.5 (m, J=17.3 Hz, PtC�C), 92.3 (dd, JCP
=
135.6 Hz, 2JCP =16.8 Hz, PtC�C) 44.4 (s, [H2N(CH2CH3)2]+), 41.2 (s,
CH2CH2CH2CH3), 40.5 (s, C(CH2)4), 34.5 (t, 1JCP =17.0 Hz, PCH2), 24.7 (s,
CH2CH2CH3), 22.8 (s, CH2CH3), 13.6 (s, CH3), 12.0 (s, [H2N(CH2CH3)2]+),
2
7.6 Hz, 16H, PCH2); 13C{1H} 136.6 (s, p to CH2), 133.5 (virtual t,[33]
2JCP =7.2 Hz, o to P), 133.5 (s, m to CH2), 132.4 (m, J=70.2 Hz, J=
7.9 Hz, i to P),[34] 131.3 (s, i to CH2), 129.0 (s, o to CH2), 128.9 (s, p to
P), 128.2 (virtual t,[33] 2JCP =5.2 Hz, m to P), 97.5 (m, J=16.9 Hz,
PtC�C),[40] 88.4 (dd, 2JCP =149.6 Hz, 2JCP =18.1 Hz, PtC�C), 43.5 (t,
2JCP =8.9 Hz, C(CH2)4), 42.2 (s, CH2C6H4), 29.7 (t, 1JCP =18.7 Hz,
PCH2),[35] 21.1 (s, CH3); 31P{1H} À 4.6 (s, 1JPPt =2172 Hz).[36] IR (ATR,
cmÀ 1): 2963 (m), 2360 (m), 2160 (w, νC�C), 2029 (m, νC�C), 1558 (m),
1257 (s), 1095 (s), 1018 (s), 802 (s), 694 (s). MS:[37] MALDI+ (matrix
THAP), 3515 ([4f+Cu]+, 100%).
1
31P{1H} À 7.7 (s, JPPt =2254 Hz).[36] IR (cmÀ 1, powder film): 2931 (m),
2862 (m), 2160 (m, νC�C), 2098 (m, νC�C), 1620 (m), 1435 (s), 1095 (s),
995 (m), 810 (m), 725 (s).
[(n-Dec2C(CH2PPh2)2)[PKt(C�C)2K]4 (4d). A Schlenk flask was charged
with 2d (0.398 g, 0.416 mmol), 3d (0.407 g, 0.413 mmol), CuI
(0.0117 g, 0.116 mmol), HNEt2 (60 mL), and THF (200 mL) with
°
stirring and heated to 55 C. After 2 d, the solvents were removed
by rotary evaporation, and water (20 mL) was added. The mixture
was extracted with CH2Cl2 (3×30 mL). The extracts were dried
(MgSO4). The solvent was removed by oil pump vacuum to give 4d
°
Crystallography. A. A CH2Cl2 solution of 3a was stored at 3 C. After
3 d, green plates were obtained. Data were collected as outlined in
Table 3. Cell parameters were obtained from 180 data frames taken
as a tan solid (0.263 g, 0.0699 mmol, 33%), which darkened at
1
125 C and liquefied at 135 C. The H NMR and 31P{1H} NMR spectra
showed minor impurities and ca. 1 equiv. of [H2NEt]+ ClÀ . NMR (δ
(ppm), CDCl3): 1H 7.72–7.65 (m, 32H, m to P), 7.20–7.14 (m, 16H, p to
at widths of 0.5 . Integrated intensity information for each
°
°
°
reflection was obtained by reduction of the data frames with the
program APEX2.[41] Data were corrected for Lorentz and polarization
factors, and using SADABS[42] for absorption and crystal decay
effects. The structure was solved by direct methods using SHELXTL
(SHELXS).[43] All non-hydrogen atoms were refined with anisotropic
thermal parameters. The hydrogen atoms were placed in idealized
positions, and refined using a riding model. The parameters were
refined by weighted least squares refinement on F2 to
convergence.[43] B.[24] A DMSO solution of 4a was layered with
P), 7.10–7.03 (m, 32H,
o
to P), 3.76 (q, 3JHH =7.0 Hz, 4H,
[H2N(CH2CH3)2]+), 2.23 (d, 1JHP =7.0 Hz, 16H, PCH2), 1.33–0.50 (m,
168H and 6H, (CH2)9CH3) and [H2N(CH2CH3)2]+); 13C{1H} 134.1 (virtual
t,[33] 2JCP =5.6 Hz, o to P), 132.6 (m, J=69.0 Hz, J=8.7 Hz, i to P),[34]
130.0 (s, p to P), 128.0 (virtual t,[33] 3JCP =5.3 Hz, m to P), 96.5 (m, J=
15.1 Hz, PtC�C),[40] 91.3 (dd, 2JCP =146.1 Hz, 2JCP =20.1 Hz, PtC�C),
49.5 (s, [H2N(CH2CH3)2]+), 41.0 (s, CH2), 40.5 (t, JCP =6.8 Hz, C(CH2)4),
2
35.2 (t, 1JCP =19.9 Hz, PCH2),[35] 31.9 (s, CH2), 29.6 (s, CH2), 29.5 (s,
EtOAc at 3 C. After 7 d, yellow-brown crystals were obtained. Data
°
CH2), 29.3 (s, CH2), 29.2 (s, CH2), 22.7 (s, CH2), 22.6 (s, CH2), 21.5 (s,
were collected as outlined in Table 3. Data were treated as in A
(with integrated intensity information via the program
SAINTplus).[44] Approximately 14–16 DMSO molecules per asymmet-
ric unit were found from the Fourier difference map. Most of the
these were disordered, and all were SQUEEZE’d using PLATON.[45]
The absence of additional symmetry and twin components were
verified using PLATON. The hydrogen atoms were placed in
1
CH2), 14.1 (s, CH3), 12.4 (s, [H2N(CH2CH3)2]+); 31P{1H} À 8.6 (s, JPPt
=
2240 Hz).[36] IR (cmÀ 1, powder film): 2924 (s), 2854 (s), 2160 (m, νC�C),
1458 (m), 1435 (s), 1257 (s), 1095 (s), 1018 (s), 802 (s), 725 (s), 694
(s). MS:[37] MALDI+ (matrix DCTB, THAP, or CHCA), 3804 ([4d+Cu]+,
100%), 3742 ([4d+H]+, 30%).
[(Bn2C(CH2PPh2)2)[PKt(C�C)2K]4 (4e): A Schlenk flask was charged
with 2e (0.0513 g, 0.0597 mmol), 3e (0.0529 g, 0.0597 mmol), CuI
(0.0040 g, 0.021 mmol), HNEt2 (10 mL), and THF (25 mL) with stirring
idealized positions, and refined using
a riding model. The
parameters were refined by weighted least squares refinement on
F2 to convergence.[42] C.[24] A CH2Cl2 solution of 4b was layered with
°
and heated to 55 C. After 2 d, the solvents were removed by rotary
°
toluene and Et2O and stored at 3 C. After 8 d, colorless multi-
evaporation, and water (30 mL) was added. The mixture was
extracted with CH2Cl2 (3×20 mL). The extracts were dried (MgSO4).
The solvent was removed by rotary evaporation to give 4e as a tan
faceted crystals were obtained. Data were collected as outlined in
Table 3. Several molecules of CH2Cl2 and other possible solvents
were found, amounting to 1606 electrons per asymmetric unit. Two
CH2Cl2 molecules were modeled successfully, and the remaining
disordered molecules were removed using the same procedure as
in B. The structure solution and refinement were carried out
analogously. D.[24] EtOAc vapor was allowed to slowly diffuse into a
DMSO solution of 4b. After ca. 1 month, brown blocks were
obtained. Data were collected as outlined in Table 3. The structure
was solved and refined along the lines of B and C. Several DMSO
molecules were located and could be modeled successfully, refining
to a total occupancy of 3.44. Nine additional DMSO molecules could
not be modeled, and were MASKed using OLEX2.[46]
°
solid (0.0809 g, 0.0242 mmol, 81%), which darkened at 169 C and
1
blackened at 190 C. The H NMR and 31P{1H} NMR spectra showed
°
lower purity levels than 4a–d; the [H2NEt2]+ ClÀ was not quantified.
1
NMR (δ (ppm), CDCl3): H 7.36–7.16 (m, 64H, o and m to P), 7.14–
7.10 (m, 16H, o to CH2), 7.08–7.03 (m, 8H, p to CH2), 6.99–6.90 (m,
1
32H, p to P and m to CH2), 2.57 (s, 16H, CH2C6H5), 2.27 (d, JHP
=
=
2
6.9 Hz, 16H, PCH2); 13C{1H} 136.4 (s, i to CH2), 133.7 (virtual t,[33] JCP
6.8 Hz, o to P), 132.1 (m, J=68.9 Hz, J=19.4 Hz, i to P),[34] 131.2 (s, p
2
to P), 130.2 (s, m to CH2), 128.9 (s, o to CH2), 128.8 (virtual t,[33] JCP
=
5.4 Hz, m to P), 127.2 (s, p to CH2), 97.6 (m, J=19.9 Hz, PtC�C),[40]
2
2
2
92.5 (dd, JCP =149.0 Hz, JCP =19.1 Hz, PtC�C), 43.4 (t, JCP =7.9 Hz,
C(CH2)4), 29.5 (t, 1JCP =17.0 Hz, PCH2),[35] 14.3 (s, CH2C6H5); 31P{1H}
À 4.8 (s, 1JPPt =2192 Hz).[36] IR (cmÀ 1, powder film): 2963 (w), 2160 (w,
νC�C), 2013 (w, νC�C), 1381 (w), 918 (s), 794 (s).
Deposition numbers 2056508 (for 3a·CH2Cl2), 2057356 (for 4a),
2057355 (for 4b·2CH2Cl2), and 2055357 (for 4b·3.44DMSO) contain
the supplementary crystallographic data for this paper. These data
are provided free of charge by the joint Cambridge Crystallographic
Data Centre and Fachinformationszentrum Karlsruhe Access Struc-
tures service.
[((p-tolCH2)2C(CH2PPh2)2)PKt(C�C)2K]4 (4f):
A Schlenk flask was
charged with 2f (0.0586 g, 0.0661 mmol), 3f (0.0613 g,
0.0671 mmol), CuI (0.0022 g, 0.012 mmol), HNEt2 (10 mL), and THF
°
(25 mL) with stirring and heated to 55 C. After 2 d, the solvents
were removed by rotary evaporation, and water (30 mL) was added.
The mixture was extracted with CH2Cl2 (20 mL). The extract was
dried (MgSO4). The solvent was removed by rotary evaporation to
Acknowledgements
give 4f as a tan solid (0.0629 g, 0.0182 mmol, 55%), which
1
darkened at 161 C and blackened at 179 C. The H NMR and 31P
°
°
The authors thank the US National Science Foundation (CHE-
1153085, CHE-1566601 and CHE-1900549) for financial support,
{1H} NMR spectra showed lower purity levels than 4a–d; the
Chem. Eur. J. 2021, 27, 1–20
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17
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These are not the final page numbers!

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doi.org/10.1002/chem.202100305
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[9] A few higher homologs of I and II with octatetraynediyl linkers have
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the Laboratory for Molecular Simulation and Texas A&M High
Performance Research Computing Facility for computational
resources, and Dr. Hashem Amini and Prof. Frank Sottile for
helpful discussions.
Conflict of Interest
The authors declare no conflict of interest.
Keywords: molecular polygons
·
platinum
·
polyyne
·
Sonogashira-Hagihara coupling · UV/Vis spectroscopy
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[23] The complexes 4a–f or their ammonium salt adducts were soluble in
CHCl3, CH2Cl2, and DMSO, but insoluble in hexane. Those with shorter
geminal substituents were insoluble in diethyl ether (4a–c), but those
with more lipophilic substituents were soluble (4d–f). Complex 4c was
soluble in ethyl acetate and slightly soluble in toluene, but 4a,b were
not.
[24] The crystals used for the three structure determinations of 4a,b took
periods of one week to one month to grow from samples that
contained [H2NEt2]+, and were not obtained in preparatively useful
quantities. Rather, data were collected on the most promising looking
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Chemistry—A European Journal
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[36] This coupling represents
a
satellite (d, 195Pt=33.8%), and is not
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[37] m/z, most intense peak of isotope envelope (relative intensity).
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[34] This signal is part of a complex spin system and the coupling constants
were assigned by a simulation.[19]
Manuscript received: January 25, 2021
Version of record online: ■■■, ■■■■
Chem. Eur. J. 2021, 27, 1–20
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FULL PAPER
B. K. Collins, Dr. M. Clough Mastry, A.
Ehnbom, Dr. N. Bhuvanesh,
Prof. Dr. M. B. Hall*, Prof. Dr. J. A.
Gladysz*
1 – 20
Macrocyclic Complexes Derived from
Four cis-L2Pt Corners and Four Buta-
diynediyl Linkers; Syntheses, Elec-
tronic Structures, and Square versus
Skew Rhombus Geometries
Complexes with cyclic Pt4C16 cores
comprised of platinum(II) corners and
butadiynediyl edges were synthe-
sized, and their geometric and elec-
tronic structures as well as spectro-
scopic and redox properties closely
examined.