Bis(alkynyl) PTA and DAPTA complexes of Pt(II) and Pd(II)

Article abstract of DOI:10.1016/j.poly.2014.11.003

Platinum(II) and palladium(II) complexes containing two substituted alkynyl groups and two PTA or DAPTA ligands (PTA = 1,3,5-triaza-7-phosphaadamantane; DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) with the general formulas cis- or trans-M(PR₃)₂(CCR)₂ (PR₃ = PTA or DAPTA) were prepared by a ligand displacement reaction starting from M(CCR)₂(COD) precursors or by a metathesis reaction utilizing MCl₂(PR₃)₂ precursors in yields ranging from 68% to 89%. The substituted alkynyl groups employed were (CCR) (R = p-tolyl, o-pyridyl, m-pyridyl, m-C₆H₄NH₂, and CH₂Ph). The new complexes were characterized by multinuclear NMR and IR spectroscopy, MS and elemental analysis. The molecular structures of the complexes, cis-Pt(PTA)₂(CC-p-tol)₂ (cis-1), trans-Pt(PTA)₂(CC-o-py)₂ (trans-3), and trans-Pd(PTA)₂(CC-o-py)₂ (trans-4) were confirmed by single crystal X-ray crystallography.

Full text of DOI:10.1016/j.poly.2014.11.003

Polyhedron 87 (2015) 55–62
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Bis(alkynyl) PTA and DAPTA complexes of Pt(II) and Pd(II)
⇑
Janet Braddock-Wilking , Sitaram Acharya, Nigam P. Rath
Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Blvd., St. Louis, MO 63121, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Platinum(II) and palladium(II) complexes containing two substituted alkynyl groups and two PTA or
DAPTA ligands (PTA = 1,3,5-triaza-7-phosphaadamantane; DAPTA = 3,7-diacetyl-1,3,7-triaza-5-phosp-
habicyclo[3.3.1]nonane) with the general formulas cis- or trans-M(PR3)2(C„CR)2 (PR3 = PTA or DAPTA)
were prepared by a ligand displacement reaction starting from M(C„CR)2(COD) precursors or by a
metathesis reaction utilizing MCl2(PR3)2 precursors in yields ranging from 68% to 89%. The substituted
alkynyl groups employed were (C„CR) (R = p-tolyl, o-pyridyl, m-pyridyl, m-C6H4NH2, and CH2Ph). The
new complexes were characterized by multinuclear NMR and IR spectroscopy, MS and elemental
analysis. The molecular structures of the complexes, cis-Pt(PTA)2(C„C-p-tol)2 (cis-1), trans-Pt(PTA)2
(C„C-o-py)2 (trans-3), and trans-Pd(PTA)2(C„C-o-py)2 (trans-4) were confirmed by single crystal X-ray
crystallography.
Received 23 August 2014
Accepted 6 November 2014
Available online 14 November 2014
Keywords:
Platinum
Palladium
PTA
DAPTA
Alkynyl
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
r-bonded alkynyl complexes have attracted attention due to their
synthetic, catalytic, and materials applications [14].
Complexes containing the water soluble phosphine ligands,
1,3,5-triaza-7-phosphaadamantane (PTA) [1] and 3,7-diacetyl-1,3,
7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA) [2] coordinated
to transition metals have gained significant attention over the last
few decades. Transition-metal complexes containing either PTA or
DAPTA ligands have been reported for metals of groups 6–12 [3].
Metal-catalyzed reactions involving complexes with the PTA and
DAPTA ligands are known for a variety of processes including
hydrogenation [4], hydroformylation [4b], hydroamination [5],
Aza–Morita–Baylis–Hillman [6], Suzuki [7], and Sonogashira
couplings [8], and Baeyer–Villiger oxidation [9] reactions using
water as a solvent or an aqueous biphasic solvent system [10]. A
significant number of studies on the use of water soluble
transition-metal complexes containing the PTA and DAPTA ligands
for their medicinal and therapeutic applications are known with
numerous studies involving ruthenium systems [3,11]. Romerosa
and coworkers have investigated a number of Pt-PTA and DAPTA
complexes for their biological applications [12].
2. Experimental
General comments: All reactions were performed under an inert
atmosphere of argon using flame or oven dried glassware on a
dual-manifold Schlenk line unless otherwise indicated. The
following solvents were purchased from Fisher Chemical Co.,
distilled over appropriate drying agents under nitrogen prior to
use then stored over activated molecular sieves: acetone, chloro-
form, diethyl ether, ethanol, methanol, methylene chloride, and
pentane. Chloroform-d and dimethyl sulfoxide-d6 were purchased
from Cambridge Isotopes Inc. and dried over activated molecular
sieves before use. The complex, PtCl2(COD) was purchased from
Strem Chemical Co. and used as received. All other chemicals were
purchased from Sigma–Aldrich Chemical Co. and distilled prior to
use (phenylacetylene, 3-phenyl-1-propyne and 4-ethynyltoluene)
whereas 1,3,5-triaza-7-phosphaadamantane (PTA) was used as
received. The DAPTA ligand, 3,7-diacetyl-1,3,7-triaza-5-phosphab-
icyclo[3.3.1]nonane was prepared following a modified literature
procedure using acetone as the solvent instead of water and was
recrystallized from acetone/pentane [1d]. The following
compounds were prepared according to a literature (or modified)
procedure: cis-[PtCl2(PTA)2] [5a,15], cis-[PdCl2(PTA)2] [5b,11x,15a,
b,16], cis-[PtCl2(DAPTA)2] [11w], cis-[PdCl2(DAPTA)2] [11x].
Previously, we reported the synthesis of a series of platinum
and palladium PTA and DAPTA complexes with methyl, ethyl,
phenylethynyl and trimethylsilylethynyl substituents at the metal
center [13]. Herein, we describe the synthesis and characterization
of Pt and Pd-PTA and DAPTA complexes containing several different
aryl-alkynyl groups bound to the metal center. Late transition-metal
NMR spectra were recorded on a Bruker Avance-300 MHz or a
Bruker ARX-500 MHz instrument at ambient temperature. NMR
data were recorded at 300 MHz or 500 MHz, respectively for
⇑
Corresponding author. Tel.: +1 314 5166436; fax: +1 314 5166342.
E-mail address: wilkingj@umsl.edu (J. Braddock-Wilking).
http://dx.doi.org/10.1016/j.poly.2014.11.003
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

56
J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
1H, and 121 and 202 MHz for 31P. Unless otherwise stated, chloro-
form-d was used as the NMR solvent. Proton and phosphorus
chemical shifts (d) are reported relative to the residual protio
(7.24 ppm) solvent resonance and external H3PO4, (0 ppm),
respectively. Chemical shifts are reported in ppm and the coupling
constants in Hertz. Melting point determinations were obtained on
a Mel-Temp melting point apparatus and are uncorrected. Mass
spectral data were obtained in FAB mode with nitrobenzyl alcohol
(NBA) on a JEOL MStation-JMS700. Infrared spectra were recorded
on a Thermo-Nicolet Avatar 360-FT IR spectrometer. Elemental
analysis determinations were performed by Atlantic Microlabs,
Inc., Norcross, GA. The X-ray crystallographic data were collected
on a Bruker Apex II diffractometer equipped with a CCD area
detector.
and the resulting white residue was washed with diethyl ether
(3 Â 10 mL). The solid was dried in vacuo. Complex cis-1 was
obtained as an off-white solid (0.123 g, 89% yield), Mp
258–260 °C. 1H NMR (300 MHz): d = 7.26 (d, J = 7.9 Hz, 4H, ArH),
7.06 (d, J = 7.9 Hz, 4H, ArH), 4.60–4.44 (br m, 12H, NCH2N), 4.40
(br s, 12H, PCH2N), 2.32 (s, 6H, CH3), 1.57 (s, 2H, H2O). 31P{1H}
NMR (121 MHz): d = À70.3 (1JPtP = 2070 Hz). IR (
m
, cmÀ1): 2120
(C„C). HRMS (FAB): m/z calcd for C30H39N6P2Pt, 740.2360; Found:
740.2363 [(M+H)+]. Anal. Calc. for C30H38N6P2PtÁH2O: C, 47.55; H,
5.32. Found: C, 47.78; H, 5.11%.
The synthetic method described in Section 2.1.2. was used for
the synthesis of the following complexes (Sections 2.1.2.1–2.1.2.7.)
2.1.2.1. Synthesis of cis-[Pt{C2(o-py)}2(PTA)2] (cis-3). Reagents used:
[Pt{C2(o-py)}2(COD)] (0.100 g, 0.196 mmol) in dichloromethane
(25 mL) and PTA (0.061 g, 0.39 mmol) in methanol (25 mL). Reac-
tion time: 16 h. Complex cis-3 was obtained as a white solid
(0.115 g, 82% yield), Mp 279–281 °C. Complex cis-3 undergoes slow
isomerization on standing in solution. 1H NMR (300 MHz): d = 8.50
(d, J = 4.3 Hz, 2H, ArH), 7.57 (m, 2H, ArH), 7.31–7.23 (m, 2H, ArH,
overlapping with solvent), 7.08 (m, 2H, ArH), 4.53 (br s, 12H,
NCH2N), 4.40 (br s, 12H, PCH2N). 31P{1H} NMR (202 MHz):
2.1. Synthesis of the complexes
2.1.1. Synthesis of precursor complexes
2.1.1.1. Synthesis of [Pt{C2(p-tol)}2(COD)]. A representative synthe-
sis for the Pt(alkynyl)2(COD) precursor complexes is described in
the following modified procedure [17]. To a 100 mL three-necked
round-bottom flask equipped with a 25 mL addition funnel and a
magnetic stir bar was placed PtCl2(COD) (0.100 g, 0.267 mmol).
Absolute ethanol (30 mL) was added to the flask and the resulting
suspension was stirred for 5 min. Triethylamine (0.080 g,
0.80 mmol) was then added to the suspension followed by the
dropwise addition of 4-ethynyltoluene (0.307 g, 2.67 mmol) over
5 min with stirring. Additional absolute ethanol (5 mL) was added
and the solution was stirred over 16 h and a white precipitate
gradually formed. The resulting mixture was filtered using a
sintered glass frit. The white solid obtained was washed with
methanol (3 Â 5 mL) and dried in a vacuum desiccator for 6 h. The
solid was dissolved in a minimal amount of CH2Cl2 and filtered.
The filtrate containing the product was evaporated and the resultant
precipitate was washed with 5 mL of diethyl ether and dried in
vacuo. The product was obtained as a white solid (0.121 g, 85%
yield). 1H NMR (300 MHz): d = 7.31–7.22 (d, 4H), 7.06–6.97
(d, 2H), 5.65 (br, JPtH = 44 Hz, 4H), 2.53 (br, 8H), 2.27 (s, 6H).
2.1.1.1.1. [Pt{C2(o-py)}2(COD)] [17a]. Reagents used: PtCl2(COD)
(0.100 g, 0.267 mmol, triethylamine (0.080 g, 0.80 mmol), and
2-ethynylpyridine (0.275 g, 2.67 mmol). The product was obtained
as an off-white solid (0.107 g, 79% yield). 1H NMR (300 MHz,
CDCl3): d = 8.47 (m, 2H), 7.52 (dt, J = 7.7 Hz, 1.8 Hz, 2H), 7.37
(m, 2H), 7.07–7.02 (m, 2H), 5.77 (br, JPtH = 45 Hz, 4H), 2.55 (br, 8H).
d = À70.5 (1JPtP = 2069 Hz). IR (
HRMS (FAB): m/z calcd for
m
, cmÀ1): 2108 (C„C), 1605 (C@N).
C26H33N8P2Pt, 714.1950; Found:
714.1923 [(M+H)+]. Anal. Calc. for C26H32N8P2Pt: C, 43.76; H, 4.52.
Found: C, 43.25; H, 4.84%.
2.1.2.2. Synthesis of cis-[Pt{C2(m-py)}2(PTA)2] (cis-5). Reagents used:
[Pt{C2(m-py)}2(COD)] (0.100 g, 0.196 mmol) in dichloromethane
(25 mL) and PTA (0.061 g, 0.39 mmol) in methanol (25 mL).
Reaction time: 16 h. Complex (cis-5) was obtained as a white solid
(0.120 g, 86% yield), Mp 294 °C (dec). 1H NMR (300 MHz): d = 8.67
(br s, 2H, ArH), 8.38 (m, 2H, ArH), 7.68 (m, 2H, ArH), 7.18–7.11 (m,
2H, ArH), 4.62–4.44 (br m, 12H, NCH2N), 4.32 (br s, 12H, PCH2N).
31P{1H} NMR (121 MHz): d = À71.5 (1JPtP = 2075 Hz). IR (
m
, cmÀ1):
2112 (C„C), 1613 (C@N). HRMS (FAB): m/z calcd for C26H33N8P2Pt,
714.1951; Found: 714.1952 [(M+H)+]. Anal. Calc. for C26H32N8P2Pt:
C, 43.76; H, 4.52. Found: C, 43.49; H, 4.62%.
2.1.2.3. Synthesis of cis-[Pt{C2(m-C6H4NH2)}2(PTA)2] (cis-7). Reagents
used: [Pt{C2(m-C6H4NH2)}2(COD)] (0.080 g, 0.15 mmol) in dichloro-
methane (25 mL) and PTA (0.047 g, 0.30 mmol) in methanol
(25 mL). Reaction time: 12 h. Complex cis-7 was obtained as an
off-white solid (0.086 g, 78% yield), Mp 257–259 °C. 1H NMR
(300 MHz, DMSO-d6): d = 6.90 (m, 2H, ArH), 6.52 (br s, 2H, ArH),
6.48–6.35 (m, 4H, ArH), 5.01 (br m, 4H, NH2), 4.52–4.37 (br m,
12H, NCH2N), 4.26 (br m, 12H, PCH2N). 31P{1H} NMR (202 MHz,
2.1.1.1.2. [Pt{C2(m-py)}2(COD)].
Reagents used: PtCl2(COD)
(0.100 g, 0.267 mmol), triethylamine (0.080 g, 0.80 mmol), and
3-ethynylpyridine (0.275 g, 2.67 mmol). The product was obtained
as an off-white solid (0.110 g, 81% yield). 1H NMR (300 MHz,
CDCl3): d = 8.63 (d, J = 1.3 Hz, 2H), 8.40 (dd, J = 4.8 Hz, 1.6 Hz, 2H),
7.67 (dt, J = 8.0 Hz, 1.8 Hz, 2H), 7.17–7.11 (m, 2H), 5.75 (br,
JPtH = 43 Hz, 4H), 2.62 (br, 8H).
DMSO-d6): d = À70.5 (1JPtP = 2065 Hz). IR (
m
, cmÀ1): 2095 (C„C),
1593 (NH2). Anal. Calc. for C28H36N8P2Pt: C, 45.34; H, 4.89. Found:
C, 45.11; H, 4.99%.
2.1.1.1.3. [Pt{C2(m-C6H4NH2)}2(COD)]. Reagents used: PtCl2(COD)
(0.100 g, 0.267 mmol), triethylamine (0.080 g, 0.80 mmol), and
3-ethynylaniline (0.309 g, 2.67 mmol). The product was obtained
as an off-white solid (0.111 g, 78% yield). 1H NMR (300 MHz):
d = 7.03 (t, J = 7.8 Hz, 2H), 6.83 (m, 2H), 6.76 (m, 2H), 6.52 (m,
2H), 5.68 (br, JPtH = 45.0 Hz, 4H), 3.58 (br, 4H, NH2), 2.57 (br, 8H).
2.1.2.4. Synthesis of cis-[Pt{C2(p-tol)}2(DAPTA)2] (cis-10). Reagents
used: [Pt{C2(p-tol)}2(COD)] (0.100 g, 0.187 mmol) in dichlorometh-
ane (25 mL) and DAPTA (0.086 g, 0.38 mmol) in methanol (25 mL).
Reaction time: 16 h. Complex cis-10 was obtained as an off-white
solid (0.130 g, 79% yield), Mp 261–263 °C. 1H NMR (500 MHz,
DMSO-d6): d = 7.29 (d, J = 6.8, 4H, ArH), 7.07 (d, J = 6.8, 4H, ArH),
5.70 (br m, 2H, PCH2N), 5.59 (d, J = 12.9 Hz, 2H, NCH2N), 5.00
(d, J = 12.9 Hz, 2H, NCH2N), 4.83 (br m, 2H, PCH2N), 4.57 (d,
J = 12.9 Hz, 2H, NCH2N), 4.17 (d, J = 14.3 Hz, 2H, PCH2N), 4.03
(br m, 2H, NCH2N and 4H, PCH2N), 3.62 (br m, 2H, PCH2N), 3.28
(s, 4H, 2H2O), 2.26 (s, 6H, CH3), 1.96 and 1.86 (s, 12H, COCH3).
31P{1H} NMR (121 MHz, DMSO-d6): d = À41.5 (1JPtP = 2152 Hz). IR
2.1.2. Synthesis of cis-[Pt{C2(p-tol)}2(PTA)2] (cis-1), method 1
A
solution of Pt{C2(p-tol)}2(COD) (0.100 g, 0.187 mmol) in
dichloromethane (25 mL) was placed in a 100 mL round-bottom
flask equipped with a 25 mL addition funnel and a magnetic stir
bar. A solution of PTA (0.058 g, 0.38 mmol) in methanol (25 mL)
was added dropwise with stirring over 10 min. The reaction
solution was stirred for 12 h at room temperature. The reaction
mixture was then evaporated to dryness on a rotary evaporator
(m
, cmÀ1): 2140 (C„C), 1642 (C@O). Anal. Calc. for C36H46N6O4P2
PtÁ2H2O: C, 47.01; H, 5.48. Found: C, 47.16; H, 5.34%.

J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
57
2.1.2.5. Synthesis of trans-[Pt{C2(o-py)}2(DAPTA)2] (trans-12). Reagents
used: [Pt{C2(o-py)}2(COD)] (0.070 g, 0.14 mmol) in dichloromethane
(25 mL) and DAPTA (0.063 g, 0.28 mmol) in methanol (25 mL).
Reaction time: 16 h. Complex trans-12 was obtained as an off-white
solid (0.098 g, 83% yield). See Section 2.1.3.11 for characterization
data for trans-12.
2.1.3.2. Synthesis of trans-[Pt{C2(o-py)}2(PTA)2] (trans-3). Reagents
used: cis-PtCl2(PTA)2 (0.080 g, 0.14 mmol), triethylamine (0.041 g,
0.41 mmol), and 2-ethynylpyridine (0.071 g, 0.69 mmol), in
25 mL of absolute ethanol. Reaction time: 16 h. Complex trans-3
was obtained as a white solid (0.079 g, 81% yield), Mp 304–
306 °C. X-ray quality crystals of trans-3 were obtained by layering
of methanol to a CHCl3 solution of trans-3 at a lower temperature
(below 0 °C). 1H NMR (500 MHz): d 8.50 (d, 2H, ArH), 7.55 (m, 2H,
ArH), 7.31–7.25 (m, 2H, ArH, overlapping with solvent), 7.08
(m, 2H, ArH), 4.53 (br s, 12H, NCH2N), 4.41 (br s, 12H, PCH2N).
2.1.2.6. Synthesis of cis-[Pt{C2(m-py)}2(DAPTA)2] (cis-13). Reagents
used: [Pt{C2(m-py)}2(COD)] (0.070 g, 0.14 mmol) in dichloromethane
(25 mL) and DAPTA (0.063 g, 0.28 mmol) in methanol (25 mL).
Reaction time: 16 h. Complex cis-13 was obtained as an off-white
solid (0.099 g, 84% yield). See Section 2.1.3.12 for characterization
data for cis-13
31P{1H} NMR (202 MHz): d = À64.3 (1JPtP = 2282 Hz). IR (
m
, cmÀ1):
2103 (C„C), 1617 (C@N). HRMS (FAB): m/z calcd for C26H33N8P2Pt,
714.1950; Found: 714.1937 [(M+H)+].
2.1.3.3. Synthesis of trans-[Pd{C2(o-py)}2(PTA)2] (trans-4). Reagents
used: cis-PdCl2(PTA)2 (0.080 g, 0.16 mmol), triethylamine
(0.049 g, 0.49 mmol), and 2-ethynylpyridine (0.084 g, 0.81 mmol),
in 25 mL of absolute ethanol. Reaction time: 12 h. Complex trans-
4 was obtained as a white solid (0.084 g, 83% yield), Mp 196 °C
(dec). Complex trans-4 was found to be unstable in solutions on
standing long at room temperature. X-ray quality crystals of
trans-4 were obtained by layering of methanol to a CHCl3 solution
of trans-4 at a lower temperature (below 0 °C). 1H NMR (500 MHz):
d = 8.49 (d, J = 4.3 Hz, 2H, ArH), 7.55 (m, 2H, ArH), 7.29 (d,
J = 7.8 Hz, 2H, ArH), 7.08 (m, 2H, ArH), 4.58–4.49 (br m, 12H,
NCH2N), 4.45 (br s, 12H, PCH2N). 31P{1H} NMR (121 MHz):
2.1.2.7. Synthesis of cis-[Pt{C2(m-C6H4NH2)}2(DAPTA)2] (cis-14). Reagents
used: [Pt{C2(m-C6H4NH2)}2(COD)] (0.075 g, 0.14 mmol) in dichloro-
methane (25 mL) and DAPTA (0.064 g, 0.28 mmol) in methanol
(25 mL). Reaction time: 16 h. Complex cis-14 was obtained as a yellow
solid (0.084 g, 68% yield), Mp 246-248 °C. 1H NMR (300 MHz,
DMSO-d6): d = 6.89 (t, J = 7.8 Hz, 2H, ArH), 6.63–6.51 (m, 4H, ArH),
6.39 (d, J = 8.0 Hz, 2H, ArH), 5.59 (d, J = 13.0 Hz, 2H, NCH2N and 2H,
PCH2N), 5.04–4.95 (m, 6H, 4H, ArNH2 and 2H, NCH2N), 4.84 (br m,
2H, PCH2N), 4.57 (d, J = 13.6 Hz, 2H, NCH2N), 4.19 (d, J = 15.1 Hz, 2H,
PCH2N), 4.08–3.96 (m, 2H, NCH2N and 4H, PCH2N)), 3.64 (br m, 2H,
PCH2N), 3.32 (s, 3H, 1.5 H2O), 1.97 and 1.90 (s, 12H, COCH3). 31P{1H}
NMR (121 MHz, DMSO-d6): d = À41.2 (1JPtP = 2141 Hz). IR (
m
, cmÀ1):
d = À56.1. IR (
m
, cmÀ1): 2120 (C„C), 1629 (C@N). HRMS (FAB): m/z
2103 (C„C), 1638 (C@O), 1589 (NH2). Anal. Calc. for C34H44N8O4P2
PtÁ1.5H2O: C, 44.74; H, 5.19. Found: C, 45.02; H, 5.08%.
calcd for C26H33N1806PdP2, 625.1338; Found: 625.1353 [(M+H)+]. Anal.
Calc. for C26H32N8PdP2: C, 49.97; H, 5.16. Found: C, 49.46; H, 5.32%.
2.1.3. Synthesis of cis-[Pt{C2(p-tol)}2(PTA)2] (cis-1), method 2
In a 100 mL three-necked round-bottom flask equipped with a
25 mL addition funnel and a magnetic stir bar was placed cis-
PtCl2(PTA)2 (0.080 g, 0.14 mmol). Absolute ethanol (20 mL) was
added to the flask and the resulting suspension was stirred for
5 min. Triethylamine (0.041 g, 0.41 mmol) was added to the sus-
pension followed by the dropwise addition of 4-ethynyltoluene
(0.079 g, 0.69 mmol) over 5 min with stirring. Absolute ethanol
(5 mL) was added and the solution was stirred over ca. 72 h and
an off-white precipitate gradually formed. The resulting mixture
was filtered using a sintered glass frit. The off-white solid was
washed with methanol (3 Â 5 mL) and dried in a vacuum desicca-
tor for 6 h. The solid was dissolved in a minimal amount of CH2Cl2
and filtered. The filtrate containing cis-1 was evaporated and the
resulting precipitate was washed with 5 mL of diethyl ether and
dried in vacuo. Complex cis-1 was obtained as an off-white solid
(0.081 g, 80% yield). See Section 2.1.2 for characterization data
for cis-1.
2.1.3.4. Synthesis of trans-[Pt{C2(m-py)}2(PTA)2] (trans-5). Reagents
used: cis-PtCl2(PTA)2 (0.080 g, 0.14 mmol), triethylamine (0.041 g,
0.41 mmol), and 3-ethynylpyridine (0.071 g, 0.69 mmol) in abso-
lute ethanol (25 mL total). Reaction time: 16 h. Complex trans-5
was obtained as a white solid (0.082 g, 84% yield), Mp 319 °C
(dec). Complex trans-5 appears to undergo isomerization to give
cis-5 upon standing for long periods of time in CDCl3 and DMSO-
d6 solutions. 1H NMR (500 MHz): d = 8.62 (br s, 2H, ArH), 8.42
(m, 2H, ArH), 7.61 (m, 2H, ArH), 7.18 (m, 2H, ArH), 4.59–4.49 (br
m, 12H, NCH2N), 4.40 (br s, 12H, PCH2N). 31P{1H} NMR
(121 MHz): d = À65.3 (1JPtP = 2282 Hz). IR (
m
, cmÀ1): 2108 (C„C),
1609 (C@N). HRMS (FAB): m/z calcd for C26H33N8P2Pt, 714.1951;
Found: 714.1954 [(M+H)+].
2.1.3.5. Synthesis of trans-[Pd{C2(m-py)}2(PTA)2] (trans-6). Reagents
used: cis-PdCl2(PTA)2 (0.080 g, 0.16 mmol), triethylamine (0.049 g,
0.49 mmol), and 3-ethynylpyridine (0.084 g, 0.81 mmol), in abso-
lute ethanol (25 mL total). Reaction time: 12 h. Complex trans-6
was obtained as a white solid (0.080 g, 79% yield), Mp 212 °C
(dec). Complex trans-6 was found to be unstable in solution on
standing for long periods of time at room temperature. 1H NMR
(300 MHz): d = 8.63 (d, J = 1.4, 2H, ArH), 8.42 (dd, J = 4.8 and 1.4,
2H, ArH), 7.63 (dt, J = 7.8 and 1.9, 2H, ArH), 7.19 (m, 2H, ArH),
4.56 (br s, 12H, NCH2N), 4.43 (br s, 12H, PCH2N). 31P{1H} NMR
The synthetic method described in Section 2.1.3. was used for
the synthesis of the following complexes (Sections 2.1.3.1–
2.1.3.12)
2.1.3.1. Synthesis of trans-[Pd{C2(p-tol)}2(PTA)2] (trans-2). Reagents
used: cis-PdCl2(PTA)2 (0.080 g, 0.16 mmol), triethylamine
(0.049 g, 0.49 mmol), and 4-ethynyltoluene (0.094 g, 0.81 mmol)
in absolute ethanol (25 mL total). Complex trans-2 was obtained
as an off-white solid (0.086 g, 81% yield), Mp 219 °C (dec). Complex
trans-2 was found to be unstable in solution on standing for long
periods of time at room temperature. 1H NMR (300 MHz):
d = 7.26 (d, J = 7.9 Hz, 4H, ArH), 7.06 (d, J = 7.9 Hz, 4H, ArH), 4.55
(s, 12H, NCH2N), 4.44 (s, 12H, PCH2N), 2.33 (s, 6H, CH3). 31P{1H}
(121 MHz): d = À56.9. IR (
m
, cmÀ1): 2108 (C„C), 1630 (C@N).
HRMS (FAB): m/z calcd for
C26H33N8PdP2, 625.1338; Found:
625.1353 [(M+H)+]. Anal. Calc. for C26H32N8PdP2: C, 49.97; H,
5.16. Found: C, 49.78; H, 5.31%.
2.1.3.6. Synthesis of cis-[Pt{C2(m-C6H4NH2)}2(PTA)2] (cis-7). Reagents
used: cis-PtCl2(PTA)2 (0.080 g, 0.14 mmol), triethylamine (0.041 g,
0.41 mmol), and 3-ethynylpyridine (0.080 g, 0.69 mmol), in abso-
lute ethanol (25 mL total). Reaction time: ca. 76 h. Complex cis-7
was obtained as an off-white solid (0.072 g, 71% yield). See Section
2.1.2.3 for characterization data for cis-7.
NMR (121 MHz): d = À56.9. IR (
m
, cmÀ1): 2104 (C„C). HRMS
(FAB): m/z calcd for C30H38N6P1206Pd, 650.1666; Found: 650.1638
(M+); m/z calcd for C30H37N6108PdP2, 651.1594; Found: 651.1600
[(MÀH)+]. Anal. Calc. for C30H38N6PdP2: C, 55.35; H, 5.88. Found:
C, 54.74; H, 5.87%.

58
J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
2.1.3.7. Synthesis of trans-[Pd{C2(m-C6H4NH2)}2(PTA)2] (trans-
8). Reagents used: cis-PdCl2(PTA)2 (0.080 g, 0.16 mmol), triethyl-
amine (0.049 g, 0.49 mmol), and 3-ethynylaniline (0.094 g,
0.81 mmol), in absolute ethanol (25 mL total). Reaction time: 16 h.
Complex trans-8 was obtained as an off-white solid (0.078 g, 74%
yield), Mp 204 °C (dec). Complex trans-8 was found to be unstable
in solution on standing for long periods of time at room temperature.
1H NMR (500 MHz): d = 7.03 (m, 2H, ArH), 6.78 (m, 2H, ArH), 6.69 (br,
2H, ArH), 6.54 (m, 2H, ArH), 4.55 (br s, 12H, NCH2N), 4.42 (br s, 12H,
PCH2N), 3.60 (br, 4H, NH2). 31P{1H} NMR (121 MHz): d = À56.9. IR
(br m, 4H, PCH2N and 2H, NCH2N), 3.73 (br m, 2H, PCH2N), 2.05 and
1.96 (s, 12H, COCH3). 31P{1H} NMR (121 MHz): d = À41.5 (1JPtP = 2441
Hz). IR (m
, cmÀ1): 2120 (C„C), 1642 (C@O). HRMS (FAB): m/z calcd for
C
C
32H41N8O4P2Pt, 858.2373; Found: 858.2375 [(M+H)+]. Anal. Calc. for
32H40N8O4P2Pt: C, 44.81; H, 4.70. Found: C, 44.74; H, 4.99%.
2.1.3.12. Synthesis of cis-[Pt{C2(m-py)}2(DAPTA)2] (cis-13). Reagents
used: cis-PtCl2(DAPTA)2 (0.080 g, 0.11 mmol), triethylamine
(0.034 g, 0.33 mmol), and of 3-ethynylpyridine (0.057 g, 0.55 mmol)
in absolute ethanol (25 mL total). Reaction time: ca. 48 h. Complex
cis-13 was obtained as an off-white solid (0.076 g, 80% yield), Mp
226–228 °C. 1H NMR (300 MHz): d = 8.71 (br s, 2H, ArH), 8.42 (m,
2H, ArH), 7.79 (m, 2H, ArH), 7.22–7.17 (m, 2H, ArH), 5.84 (br m, 2H,
NCH2N and 2H, PCH2N), 5.03 (d, J = 14.7 Hz, 2H, NCH2N), 4.85 (br
m, 2H, PCH2N), 4.65 (d, J = 13.9 Hz, 2H, NCH2N), 4.34–4.22 (br m,
2H, PCH2N), 4.15–3.91 (m, 4H, PCH2N and 2H, NCH2N), 3.55 (br m,
2H, PCH2N), 2.12 (s, 6H, COCH3), 2.06 and 2.05 (s, 12H, COCH3), 1.65
(br s, 2H, H2O). 31P{1H} NMR (121 MHz): d = À45.0 (1JPtP = 2124 Hz)
(m
, cmÀ1): 2099 (C„C), 1597 (NH2). Anal. Calc. for C28H36N8PdP2: C,
51.50; H, 5.56. Found: C, 51.05; H, 5.52%.
2.1.3.8. Synthesis of trans-Pt(C2Bz)2(PTA)2 (trans-9). Reagents used:
PtCl2(DAPTA)2 (0.080 g, 0.14 mmol), triethylamine (0.041 g,
0.41 mmol), and 3-phenyl-1-propyne (0.080 g, 0.69 mmol), in
absolute ethanol (25 mL total). Reaction time: 36 h. Complex
trans-9 was obtained as a white solid (0.079 g, 78% yield), Mp
244–246 °C. 1H NMR (300 MHz): d = 7.40–7.34 (m, 4H, ArH),
7.33–7.26 (m, 4H, ArH), 7.21–7.14 (m, 2H, ArH), 4.47–4.21 (br m,
12H, NCH2N), 4.20 (br s, 12H, PCH2N), 3.71 (br m, CH2Ph), 1.61
(br s, 2H, H2O). 31P{1H} NMR (202 MHz): d = À64.4 (1JPtP = 2335
and À45.2 (1JPtP = 2123 Hz) (approximate ratio = 1:1). IR (
m
, cmÀ1):
2123 (C„C), 1625 (C@O). HRMS (FAB): m/z calcd for C32H41N8O4P2Pt,
858.2373; Found: 858.2399 [(M+H)+]. Anal. Calc. for C32H40N8O4P2
PtÁH2O: C, 43.89; H, 4.83. Found: C, 44.17; H, 4.80%.
Hz). IR (
30H38N6P2PtNa, 762.2180; Found: 762.2188 [(M+Na)+]. Anal. Calc.
m
, cmÀ1): 2116 (C„C). HRMS (FAB+NaI): m/z calcd for
C
for C30H38N6P2PtÁH2O: C, 47.55; H, 5.32. Found: C, 47.38; H, 5.19%.
The reaction was found to be incomplete after 12 h and the for-
mation of a mixture of trans-9 and an unassigned product were
observed in approximately 1:1 ratio. 31P{1H} NMR (202 MHz):
d = À64.4 (1JPtP = 2335 Hz, trans-9), À61.2 (1JPtP = 2376 Hz, unas-
signed). Complex trans-9 appears to undergo slow conversion to
the unassigned product (20:1 ratio, respectively) upon standing
in CDCl3 solution for a few days.
2.1.4. X-ray structure determination of complexes cis-1, trans-3, and
trans-4
Crystals of cis-1, trans-3, and trans-4 were obtained by layering
CH3OH over a CHCl3 (CH2Cl2 for cis-1) solution containing the com-
plex at low temperature (below 0 °C). Crystals of appropriate
dimensions were mounted on MiTeGen cryoloops in random orien-
tations. Preliminary examination and data collection were per-
formed using a Bruker X8 Kappa Apex II Charge Coupled Device
(CCD) Detector system single crystal X-ray diffractometer
equipped with an Oxford Cryostream LT device. All data were col-
2.1.3.9. Synthesis of cis-[Pt{C2(p-tol)}2(DAPTA)2] (cis-10). Reagents
used: cis-PtCl2(DAPTA)2 (0.080 g, 0.11 mmol), triethylamine
(0.034 g, 0.33 mmol), and 4-ethynyltoluene (0.064 g, 0.55 mmol)
in absolute ethanol (25 mL total). Reaction time: ca. 65 h. Complex
cis-10 was obtained as an off-white solid (0.073 g, 75% yield). See
Section 2.1.3.4 for characterization data for cis-10.
lected using graphite monochromated Mo
K
radiation
(k = 0.71073 Å) from a fine focus sealed tube X-ray source. The
crystallographic data were collected at 100(2) K for all three of
the complexes. Preliminary unit cell constants were determined
with a set of 36 narrow frame scans. Typical data sets consist of
combinations of
- and / scan frames with typical scan width of
2.1.3.10. Synthesis of trans-[Pd{C2(p-tol)}2(DAPTA)2] (trans-11). Reagents
used: cis-PdCl2(DAPTA)2 (0.070 g, 0.11 mmol), triethylamine
(0.034 g, 0.34 mmol), and 4-ethynyltoluene (0.063 g, 0.55 mmol)
in absolute ethanol (25 mL). Reaction time: ca. 18 h. Complex
trans-11 was obtained as a yellow solid (0.070 g, 80% yield), Mp
228 °C (dec). Complex trans-11 was found to be unstable in solu-
tion upon standing for long periods of time at room temperature.
1H NMR (300 MHz): d = 7.26 (d, 4H, overlapping with solvent,
ArH), 7.08 (d, J = 8.0 Hz, 4H, ArH), 5.80–5.90 (m, 2H, NCH2N and
2H, PCH2N), 5.00 (d, J = 14.7 Hz, 2H, NCH2N), 4.87 (br m, 2H,
PCH2N), 4.64 (d, J = 13.4 Hz, 2H, NCH2N), 4.40 (br m, 2H, PCH2N),
4.11–4.00 (m, 2H, NCH2N and 4H, PCH2N), 3.84 (br m, 2H, PCH2N),
2.32 (s, 6H, CH3), 2.12 and 2.08 (s, 12H, COCH3). 31P{1H} NMR
0.5° and counting time of 15–30 s/frame at a crystal to detector
distance of 4.0 cm. The collected frames were integrated using an
orientation matrix determined from the narrow frame scans. Apex
II and SAINT software packages [18] were used for data collection
and data integration. Analysis of the integrated data did not show
any decay. Final cell constants were determined by global refine-
ment of xyz centroids from the complete data set. Collected data
were corrected for systematic errors using SADABS [18] based on
the Laue symmetry using equivalent reflections.
Crystal data and intensity data collection parameters for cis-1,
trans-3, and trans-4 are listed in Table 1. Structure solution and
refinement were carried out using the SHELXTL-PLUS software package
[19]. The structures were solved by direct methods and refined
(202 MHz): d = À35.2. IR (
m
, cmÀ1): 2103 (C„C), 1650 (C@O). Anal.
successfully in the space groups Pbca, P1, and P21/c for complexes
ꢀ
Calc. for C36H46N6O4PdP2: C, 54.38; H, 5.83. Found: C, 54.97;
cis-1, trans-3 and trans-4, respectively. Full matrix least-squares
H, 5.70%.
refinements were carried out by minimizing
R
w(Fo2 À Fc2)2. The
non-hydrogen atoms were refined anisotropically to convergence.
A molecule of CH2Cl2 solvate was found in case of cis-1 which
was refined with geometrical restraints. A molecule of CHCl3 was
located in case of trans-4. All hydrogen atoms were treated using
appropriate riding model (AFIX m3).
2.1.3.11. Synthesis of trans-[Pt{C2(o-py)}2(DAPTA)2] (trans-12). Reagents
used: cis-PtCl2(DAPTA)2 (0.080 g, 0.11 mmol), triethylamine (0.034 g,
0.33 mmol), and 2-ethynylpyridine (0.057 g, 0.55 mmol) in absolute
ethanol (25 mL total). Reaction time: ca. 48 h. Complex trans-12 was
obtained as an off-white solid (0.077 g, 82% yield), Mp 196–198 °C.
1H NMR (300 MHz, DMSO-d6): d = 8.42 (br s, 2H, ArH), 7.68 (br m,
2H, ArH), 7.47 (m, 2H, ArH), 7.18 (br m, 2H, ArH), 5.59 (br m, 2H,
NCH2N and 2H, PCH2N), 5.02 (br m, 2H, NCH2N), 4.87 (br m, 2H,
PCH2N), 4.62 (br m, 2H, NCH2N), 4.28 (br m, 2H, PCH2N), 4.19–4.01
Complete listings of geometrical parameters, positional and
isotropic displacement coefficients for hydrogen atoms,
anisotropic displacement coefficients for the non-hydrogen atoms
are submitted as Supplementary data within the associated CIF
files.

J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
59
Table 1
Crystallographic data and refinement for complexes cis-1, trans-3, and trans-4.
cis-1
trans-3
trans-4
Formula
C
60H76N12P4Pt2ÁCH2Cl2
C26H32N8P2Pt
713.63
C26H32N8P2PdÁ2CHCl3
863.67
0.15 Â 0.07 Â 0.06
monoclinic
P21/c
5.9965(15)
22.542(15)
12.990(3)
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
1564.31
0.43 Â 0.18 Â 0.17
0.47 Â 0.08 Â 0.07
orthorhombic
triclinic
ꢀ
Pbca
11.3678(5)
20.2126(10)
25.9026(14)
90
90
90
5951.7(5)
P1
6.3135(3)
9.9760(5)
10.8270(5)
110.424(2)
91.205(2)
96.390(2)
633.77(5)
1.870
b (Å)
c (Å)
a
(°)
90
b (°)
102.123(12)
90
1716.7(7)
c
(°)
V (Å3)
Dcalc (g cmÀ3
)
1.746
1.671
Z
4
1
2
Absorption coefficient (mmÀ1
)
4.945
5.695
1.136
h (°)
2.02–34.36
2.01–43.55
29006/8630
semi-empirical from equivalents
0.6879 and 0.1762
R1 = 0.0207
wR2 = 0.0396
1.81–25.50
38556/3160
semi-empirical from equivalents
0.9329 and 0.8490
R1 = 0.0388
wR2 = 0.0747
Reflections collected/independent reflections
Absorption correction
Maximum and minimum. transmission
Final R indices [I > 2r(I)]
20843/12458
semi-empirical from equivalents
0.4817 and 0.2228
R1 = 0.0270
wR2 = 0.0589
All but one of the complexes produced from the synthetic route
in the reaction shown in Scheme 1 had a cis-orientation of the PTA
and DAPTA ligands with the exception being the palladium DAPTA
complex, trans-12. The complexes were isolated as white to off-
white or yellow (cis-14) solids in yields ranging from 78% to 89%.
In contrast, the reaction of the cis-MCl2(PTA)2 and cis-MCl2
(DAPTA)2 complexes with the terminal alkynes produced both
cis- and trans-complexes depending upon the metal and the alky-
nyl group (Eqs. 1 and 2) with the trans products preferred for the
PTA complexes. The complexes shown in Eqs. 1, 2 were isolated
as white to off-white or yellow (trans-11) solids in yields ranging
from 71–84%. For those complexes reported herein where both
routes shown in Scheme 1 and Eqs. 1 and 2 that afforded the same
product (cis-1, cis-7, cis-10, trans-12, and cis-13) the yields were
generally slightly higher from the MCl2(COD) route.
3. Results and discussion
A series of cis- and trans-platinum(II) and palladium(II) com-
plexes containing two substituted alkynyl and two PTA or DAPTA
ligands with the general formula, [M(C„CR)2(PR3)2] (where
M = Pt or Pd, PR3 = PTA, R = p-tol, o-py, m-py, m-C6H4NH2, and
CH2Ph (Pt only); M = Pt or Pd, PR3 = DAPTA, R = p-tol ; M = Pt, PR3 =
DAPTA, R = o-py, m-py, m-C6H4NH2) were synthesized. Two gen-
eral methods were used to prepare the new complexes. The first
route utilized a ligand exchange reaction of a bis(alkynyl)platinum
or palladium cyclooctadiene precursor, M(C„CR)2(COD) in
dichloromethane with two equivalents of the phosphine ligands,
PTA or DAPTA in methanol (Scheme 1). The second synthetic route
involved reaction of the bis(phosphine)platinum or palladium
dichloride precursors, MCl2(PTA)2 and MCl2(DAPTA)2 in absolute
ethanol with the terminal alkyne in the presence of triethylamine
(Eqs. 1 and 2, respectively). The new complexes were characterized
by 1H and 31P{1H} NMR and IR spectroscopy, MS and EA in most
cases, and X-ray crystallography for three of the complexes.
Slow isomerization of complexes cis-3 and trans-5 to the corre-
sponding trans-isomers was observed in solution after several
days. The palladium complexes reported herein were all found to
be unstable in CDCl3 solution over extended periods of time.
M(C2R)2(cod)
O
N
N
P
2
CH2Cl2
MeOH
- cod
2
O
N
N
P
N
P
N
O
O
N
N
O
O
N
N
N
N
R
R
R
R
N
N
N
N
P
M
P
P
P
M
M
R
R
N
P
N
N
N
N
N
N
O
N
1
(cis- ) M = Pt, R = p-tol
O
O
10
(cis- ) M = Pt, R = p-tol
(cis-1 ) M = Pt, R = m-py
O
12
3
(cis- ) M = Pt, R = o-py
3
14
(trans- ) M = Pd, R = o-py
5
(cis- ) M = Pt, R = m-py
(cis- ) M = Pt, R = m-C6H4NH2
7
(cis- ) M = Pt, R = m-C6H4NH2
Scheme 1. Synthesis of bis(alkynyl) Pt and Pd PTA and DAPTA complexes.

60
J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
1
(PTA)2 (À64.5 ppm, JPtP = 2167 Hz, [5b]), whereas the trans
complexes of 3, 5, and 9 showed couplings near 2300 Hz. The
chemical shift and coupling values for the trans complexes
described herein are similar to trans-[Pt{C„C(CH2)3NH3}2(PTA)2]
Br2 (1JPtP = 2305 Hz) and the trans-Pt(C„CPh)2(PTA)2 complex
N
N
Cl
Cl
P
N
M
2
H
+
R
N
N
P
N
1
previously reported by our group (À64.3 ppm, JPtP = 2309 Hz)
Et3N
EtOH
[13]. The trans-Pd-PTA complexes 2, 4, 6, and 8 all exhibited a
single downfield 31P{1H} resonance at À56 ppm compared to the
Pt-PTA complexes.
N
N
N
N
The Pt- and Pd-DAPTA complexes 10–14 exhibited more com-
plex resonances in the region of 5.8 – 3.5 ppm in the 1H NMR spec-
tra for the NCH2N and PCH2N protons compared to the PTA
complexes in this study. As described by Mendía and Laguna and
coworkers, the splitting patterns for these resonances resulted
from the presence of diastereotopic protons and coupling to phos-
phorus for the PCH2N protons [11x]. These resonances and chemi-
cal shifts are similar to that of the free ligand [11x]. The Pt-DAPTA
complexes, cis-10, trans-12, and cis-14 displayed a single resonance
in the 31P{1H} NMR spectrum with 1JPtP coupling values of approx-
imately 2140 Hz and a larger coupling of 2441 Hz for trans-12. The
Pd-DAPTA complex, trans-11 also exhibited a single 31P{1H} NMR
resonance. As observed with other Pt- and Pd-DAPTA complexes,
the 31P{1H} NMR chemical shifts are shifted downfield compared
to the related PTA complexes. [11w,11x,13] The presence of two
acyl methyl resonances in the 1H NMR spectrum for these four
complexes supports an anti-conformation of the acyl groups of
the DAPTA ligands. However, complex cis-13 exhibited three acyl
methyl resonances as well as two 31P{1H} resonances with nearly
identical chemical shifts and intensities at À45.0 and À45.2 ppm,
respectively (1JPtP = 2124 and 2123 Hz) supports the presence of
two conformers in solution (syn and anti with respect to the DAPTA
ligands). The coupling values observed for the new complexes
reported herein are similar to the related complexes, cis- and
trans-[Pt(C„C(CH2)3NH3)2(PTA)2]Br2 [5b,16] and cis- and trans-
M(C„CR)2(PR3)2 (M = Pt or Pd, R = C6H5 or SiMe3, PR3 = PTA or
DAPTA) [13]. In contrast, complexes trans-11 and cis-13 exhibited
two 31P{1H} resonances with nearly identical chemical shifts and
intensity at À35 and À45 ppm, respectively (1JPtP = 2124 and
2123 Hz for cis-13) supporting the presence of two conformers in
solution (syn and anti with respect to the DAPTA ligands).
Transition-metal complexes containing the PTA and DAPTA
ligands have attracted attention due to the water solubility of the
free ligands. However, preliminary water solubility studies on
complexes cis-7 and cis-13 (solubility (at 25 °C) = 0.52 and
0.28 mM, respectively) show that these complexes are consider-
ably less soluble than the free PTA and DAPTA ligands [1d] as well
as related platinum and palladium complexes reported previously
[13].
N
N
R
R
P
M
P
P
P
N
R
R
M
N
N
N
N
N
1
2
(cis- ) M = Pt, R = p-tol
(cis- ) M = Pt
(trans- ) M = Pd, R = p-tol
7
3
(trans- ) M = Pt, R = o-py
4
R = m-C6H4NH2 (trans- ) M = Pd, R = o-py
5
(trans- ) M = Pt, R = m-py
6
(trans- ) M = Pd, R = m-py
8
(trans- ) M = Pd
R = m-C6H4NH2
(trans- ) M = Pt, R = CH2Ph
9
Eq. 1. Synthesis of bis(alkynyl) Pt and Pd PTA complexes.
O
O
N
N
N
P
Cl
Cl
M
H
R
2
+
P
N
N
N
O
O
NEt3
EtOH
O
O
O
N
N
O
O
N
N
N
N
R
R
P
N
P
P
R
M
P
R
M
N
N
N
The molecular structures of complexes cis-1, trans-3, and trans-
4 were determined by single crystal X-ray crystallography. The
molecular structure of complex cis-1 is shown in Fig. 1 with
selected bond distances and angles. The molecular structure exhib-
its a slightly distorted square planar geometry at the platinum cen-
ter with the sum of the angles around the platinum center being
360.15°. The larger than expected PAPtAP bond angle of ca. 98°
and smaller CAPtAP angles of 85–88° suggest that distortion from
the ideal geometry in cis-1 is due to some steric repulsion between
the cis-PTA ligands. The bond distances found in cis-1 are similar to
those observed in cis-Pt(C„CH)2(dppe) (PtAC = 2.025(5) Å,
PtAP = 2.2851(12) Å, and C„C 1.1648(8) Å) [20]. The methylene
chloride solvate molecule was omitted from Fig. 1.
N
N
O
O
O
10
(cis- ) M = Pt, R = p-tol
13
(cis- ) M = Pt, R = m-C6H4NH2
11
(trans- ) M = Pd, R = p-tol
12
(trans- ) M = Pt, R = o-py
Eq. 2. Synthesis of bis(alkynyl) Pt and Pd DAPTA complexes.
The characteristic resonances for the methylene NCH2 and PCH2
protons of the PTA ligands for complexes 1–9 generally appeared
as broadened multiplet resonances around 4.6–4.2 ppm in the 1H
NMR spectra, while the DAPTA complexes 10–14 exhibited more
complex resonances in the region of 5.8–3.5 ppm [16] The
acyl-methyl resonances for the DAPTA complexes 10–14 appeared
as two singlets near 2 ppm. The 31P{1H} NMR spectra for the Pt-PTA
The molecular structure of complex trans-3 is shown in Fig. 2
with selected bond distances and angles. The structure exhibits a
nearly ideal square planar geometry with the PTA ligands oriented
trans to each other and the PAPtAP and CAPtAC angles are
179.99°. There is very little deviation from planarity at the Pt
complexes displayed
a
single resonance between À64 and
1
À70 ppm with JPtP coupling values near 2070 Hz for the cis com-
plexes of 1, 3, 5, and 7 (comparable to cis-[Pt(C„C(CH2)3NH2)]

J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
61
Fig. 3. Molecular structure of complex trans-4. Thermal ellipsoids are shown at 50%
probability. Selected bond distances (Å) and angles (°): Pd(1)–P(1)#1 = 2.2614(11),
Pd(1)–P(1) = 2.2614(11), Pd(1)–C(1)#1 = 2.016(4), Pd(1)–C(1) = 2.016(4), C(1)–
C(2) = 1.188(6), C(2)–C(3) = 1.453(6); C(1)#1–Pd(1)–C(1) 180.0(2), C(1)#1–Pd(1)–
P(1)#1 86.25(12), C(1)–Pd(1)–P(1)#1 93.75(12), C(1)#1–Pd(1)–P(1) 93.75(12),
C(1)–Pd(1)–P(1) 86.25(12), P(1)#1–Pd(1)–P(1) 180.0, C(1)–C(2)–C(3) 173.4(4).
the PTA ligands and a subsequent decrease in the PAPtAP angle.
The PtAP, PtAC, and C„C bond distances of trans-[Pt{C„C(C6
H5)}2(PTA)2] were similar to trans-3 (PtAP = 2.26, PtAC = 1.96–
2.04, C„C = 1.14 Å). The PtAP, PtAC, and C„C bond distances of
trans-3 are also similar to those reported for the related complexes,
trans-[Pt{C„C(CH2)3NH3}2(PTA)2] (PtAP = 2.26, PtAC = 2.03, and
C„C = 1.19 Å) (same reference as above for comparison of cou-
pling values [5b,16] and trans-[Pt{C„C(C6H4-4-NH2)3}2(PPh3)2]
(PtAP = 2.31, PtAC = 2.00, and C„C = 1.20 Å)) [21]).
The molecular structure of complex trans-4 is shown in Fig. 3
with selected bond distances and angles. Complex trans-4 displays
a slightly distorted square planar geometry at the palladium cen-
ter. A similar arrangement is observed in the structure of trans-4
as described above with trans-3 with the tilting of the arylalkynyl
groups with respect to the PTA ligands at the metal center with the
C1AC2AC3 angle also being equal to 173°). The PtAP, PtAC, and
C„C bond distances of trans-4 are comparable to those reported
for the related complexes [5b,16,21]. The chloroform solvate
molecule was omitted from Fig. 3.
Fig. 1. Molecular structure of complex cis-1. Thermal ellipsoids are shown at 50%
probability. Selected bond distances (Å) and angles (°): Pt(1)–P(1) = 2.2759(6),
Pt(1)–P(2) = 2.2730(6), Pt(1)–C(1) = 2.011(3), Pt(1)–C(10) = 1.993(2), C(1)–C(2) =
1.205(4), C(10)–C(11) = 1.210(3), C(2)–C(3) = 1.438(4), C(11)–C(12) = 1.436(3);
P(1)–Pt(1)–P(2) 97.95(2), C(1)–Pt(1)–C(10) 88.64(10), C(1)–Pt(1)–P(1) 85.03(7),
C(10)–Pt(1)–P(2) 88.53(7), C(1)–Pt(1)–P(2) 176.72(7), C(10)–Pt(1)–P(1) 171.42(7),
C(2)–C(1)–Pt(1) 176.2(2), C(11)–C(10)–Pt(1) 175.0(2), C(1)–C(2)–C(3) 177.1(3),
C(10)–C(11)–C(12) 175.2(3).
center at the bound C and P atoms. However, there is a tilting of the
terminal aryl groups on the alkyne with respect to the central core
of the molecule. In addition, the C1AC2AC3 angle is not linear
(173°). This arrangement is likely preferred to reduce steric inter-
actions between the arylalkynyl groups with the PTA ligands. The
related complex, trans-[Pt{C„C(C6H5)}2(PTA)2] [13] displayed sig-
nificant distortion from square planar geometry with PAPtAP
angle of 137° due to the fan-shaped arrangement of the phenyl
groups on the alkynyl ligand resulting in steric repulsion with
4. Conclusions
Square planar platinum(II) and palladium(II) complexes con-
taining either two of the PTA or DAPTA ligands and two aryl-
substituted alkynyl groups at the metal center, with the general
formula, cis- or trans-(M(PR3)2(C„CAr)2 have been synthesized in
good yields. The complexes were prepared by a ligand substitution
reaction between a M(COD)(C„CAr)2 precursor and two equiva-
lents of PR3 or by a metathesis reaction involving a MCl2(PR3)2 pre-
cursor with the alkyne in the presence of a base. The complexes are
air stable, however, the palladium complexes were all found to be
unstable in CDCl3 solution over extended periods of time. All but
one of the DAPTA complexes produced only a single (anti) isomer
in solution, while the remaining complex gave a mixture of two
conformers. The molecular structures of two Pt-PTA and one
Pd-PTA complexes were confirmed by X-ray crystallography. The
two Pt-PTA complexes exhibited a distorted square planar geome-
try at the metal center whereas the Pd-PTA complex displayed a
nearly ideal square planar environment.
Fig. 2. Molecular structure of complex trans-3. Thermal ellipsoids are shown at 50%
probability. Selected bond distances (Å) and angles (°): Pt(1)–P(1)#1 = 2.2782(3),
Pt(1)–P(1) = 2.2782(3), Pt(1)–C(1)#1 = 1.9955(11), Pt(1)–C(1) = 1.9955(11), C(1)–
C(2) = 1.2165(15), C(2)–C(3) = 1.4317(15); P(1)#1–Pt(1)–P(1) 179.999(15), C(1)#1–
Pt(1)–C(1) 179.999(1), C(1)#1–Pt(1) –P(1)#1 89.25(3), C(1)–Pt(1)–P(1)#1 90.75(3),
C(1)#1–Pt(1)–P(1) 90.75(3), C(1)–Pt(1)–P(1) 89.25(3), C(2)–C(1)–Pt(1) 177.97(10),
C(1)–C(2)–C(3) 173.36(12).
Acknowledgements
Funding from the National Science Foundation – United States
(MRI, CHE-0420497) for the purchase of the ApexII diffractometer
is greatly acknowledged.

62
J. Braddock-Wilking et al. / Polyhedron 87 (2015) 55–62
Dyson, Chem. Sci. (2014) 1097;
Appendix A. Supplementary data
(h) J. Arcau, V. Andermark, E. Aguiló, A. Gandioso, A. Moro, M. Cetina, J.C. Lima,
K. Rissanen, I. Ott, L. Rodríguez, Dalton Trans. 43 (2014) 4426;
(i) K.J. Kilpin, S.M. Cammack, C.M. Clavel, P.J. Dyson, Dalton Trans. 42 (2013)
2008;
(j) E. García-Moreno, S. Gascón, J. Rodriguez-Yoldi, E. Cerrada, M. Laguna,
Organometallics 32 (2013) 3710;
(k) E. Guerrero, S. Miranda, S. Luttenberg, N. Frohlich, J.-M. Koenen, F. Mohr, E.
Cerrada, M. Laguna, A. Mendia, Inorg. Chem. 52 (2013) 6635;
(l) C.G. Hartinger, N. Metzler-Nolte, P.J. Dyson, Organometallics 31 (2012)
5677;
CCDC 1012062, 1012063, and 1012064 contain the supplemen-
tary crystallographic data for trans-4, trans-3, and cis-1. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
(m) P. Bergamini, L. Marvelli, A. Marchi, F. Vassanelli, M. Fogagnolo, P.
Formaglio, T. Bernardi, R. Gavioli, F. Sforza, Inorg. Chim. Acta 391 (2012) 162;
(n) T. Stringer, D.T. Hendricks, H. Guzgay, G.S. Smith, Polyhedron 31 (2012)
486;
(o) E. Vergara, E. Cerrada, C. Clavel, A. Casini, M. Laguna, Dalton Trans. 40
(2011) 10927;
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