Unusual [Pt{κ2(C,N)}]+ → [Pt{κ2(N,N)}]+ coordination mode flip of the guanidinate(1-) ligand in cationic N,N′,N″-tris(3,5-xylyl)guanidinatoplatinum(II) bis(phosphine) complexes. Syntheses, structural and theoretical studies

Article abstract of DOI:10.1021/acs.organomet.0c00408

Separate reactions of [Pt{κ²(C,N)}X(S(O)Me₂)] (κ²(C,N) = N,N′,N″-triarylguanidinate(1-); Ar = 2-(MeO)C₆H₄ (3), 2-MeC₆H₄ (4), 4-MeC₆H₄ (5), 2,4-Me₂C₆H₃ (6), 2,5-Me₂C₆H₃ (7), and 3,4-Me₂C₆H₃ (8); X = Cl (3), OC(O)CF₃ (4-8)) with 1,1-bis(diphenylphosphino)methane (dppm) afforded the respective cationic complexes [Pt{κ²(C,N)}{κ²(dppm)}][X] (10-15) in high yields. In contrast, the separate reactions of [Pt{κ²(C,N)}(OC(O)CF₃)(S(O)Me₂)] (κ²(C,N) = N,N′,N″-tris(3,5-xylyl)guanidinate(1-); 9) with dppm and 1,2-bis(diphenylphosphino)ethane (dppe) afforded the cationic guanidinatoplatinum(II) complexes [Pt{κ²(N,N)}{κ²(P,P)}][OC(O)CF₃] (P,P = dppm (16), dppe (17), respectively) in high yields. Further, the separate reactions of 9 with dppe and 1,3-bis(diphenylphosphino)propane (dppp) afforded the cationic complexes [Pt{κ²(C,N)}{κ²(P,P)}][OC(O)CF₃] (P,P = dppe (18), dppp (19), respectively) in high yields. The salt metathesis reaction of 19 with an excess of NH₄PF₆ afforded the cationic complex [Pt{κ²(C,N)}{κ²(dppp)}][PF₆] (20) in good yield. The new Pt(II) complexes were characterized by elemental analyses, mass spectrometry, IR, multinuclear (¹⁹⁵Pt, ³¹P, ¹H, ¹³C, and ¹⁹F) NMR spectroscopy, and conductivity measurements. Further, the molecular structures of 10·CHCl₃, 11·CHCl₃, 12·CH₂Cl₂, 14·1.5C₇H₈, 15·CH₂Cl₂, 16, 17, 18·0.5C₇H₈, 19·C₄H₁₀O, and 20·C₇H₈ were determined by single-crystal X-ray diffraction. To the best of our knowledge, 17 and 18·0.5C₇H₈ represent the first pair of crystallographically characterized metallacyclic structural isomers to be reported. The reactions of 9 with dppm and dppe carried out separately in CDCl₃ at RT were monitored by variable-time ³¹P NMR spectroscopy, which revealed the formation of a transient species, [Pt{κ²(C,N)}{κ²(dppm)}][OC(O)CF₃] (22), and 18 before finally forming the end products 16 and 17, respectively. The contributions of various factors in dictating the coordination flip of the guanidinate(1-) ligand from κ²(C,N) in 22 and 18 to κ²(N,N) in 16 and 17, respectively, were unraveled. The mechanism associated with the coordination flip of the guanidinate(1-) ligand was mapped with the aid of DFT calculations on a model complex, [Pt{κ²(C,N)}{κ²(P,P)}][OC(O)CF₃] (22′), which revealed a pathway involving a Wheland intermediate, F, and further point out that the product, [Pt{κ²(N,N)}{κ²(P,P)}][OC(O)CF₃] (16′), is a kinetically controlled product.

Full text of DOI:10.1021/acs.organomet.0c00408

pubs.acs.org/Organometallics
Article
Unusual [Pt{κ2(C,N)}]+ → [Pt{κ2(N,N)}]+ Coordination Mode Flip of the
Guanidinate(1−) Ligand in Cationic N,N′,N″‑Tris(3,5-
xylyl)guanidinatoplatinum(II) Bis(phosphine) Complexes. Syntheses,
Structural and Theoretical Studies
Rishabh Ujjval, Masilamani Deepa, Jisha Mary Thomas, Chinnappan Sivasankar,
and Natesan Thirupathi*
Cite This: https://dx.doi.org/10.1021/acs.organomet.0c00408
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Separate reactions of [Pt{κ2(C,N)}X(S(O)Me2)]
(κ2(C,N) = N,N′,N″-triarylguanidinate(1−); Ar = 2-(MeO)C6H4
(3), 2-MeC6H4 (4), 4-MeC6H4 (5), 2,4-Me2C6H3 (6), 2,5-
Me2C6H3 (7), and 3,4-Me2C6H3 (8); X = Cl (3), OC(O)CF3
(4−8)) with 1,1-bis(diphenylphosphino)methane (dppm) af-
forded the respective cationic complexes [Pt{κ2(C,N)}-
{κ2(dppm)}][X] (10−15) in high yields. In contrast, the separate
reactions of [Pt{κ2(C,N)}(OC(O)CF3)(S(O)Me2)] (κ2(C,N) =
N,N′,N″-tris(3,5-xylyl)guanidinate(1−); 9) with dppm and 1,2-
bis(diphenylphosphino)ethane (dppe) afforded the cationic
guanidinatoplatinum(II) complexes [Pt{κ2(N,N)}{κ2(P,P)}][OC-
(O)CF3] (P,P = dppm (16), dppe (17), respectively) in high yields. Further, the separate reactions of 9 with dppe and 1,3-
bis(diphenylphosphino)propane (dppp) afforded the cationic complexes [Pt{κ2(C,N)}{κ2(P,P)}][OC(O)CF3] (P,P = dppe (18),
dppp (19), respectively) in high yields. The salt metathesis reaction of 19 with an excess of NH4PF6 afforded the cationic complex
[Pt{κ2(C,N)}{κ2(dppp)}][PF6] (20) in good yield. The new Pt(II) complexes were characterized by elemental analyses, mass
1
spectrometry, IR, multinuclear (195Pt, 31P, H, 13C, and 19F) NMR spectroscopy, and conductivity measurements. Further, the
molecular structures of 10·CHCl3, 11·CHCl3, 12·CH2Cl2, 14·1.5C7H8, 15·CH2Cl2, 16, 17, 18·0.5C7H8, 19·C4H10O, and 20·C7H8
were determined by single-crystal X-ray diffraction. To the best of our knowledge, 17 and 18·0.5C7H8 represent the first pair of
crystallographically characterized metallacyclic structural isomers to be reported. The reactions of 9 with dppm and dppe carried out
separately in CDCl3 at RT were monitored by variable-time 31P NMR spectroscopy, which revealed the formation of a transient
species, [Pt{κ2(C,N)}{κ2(dppm)}][OC(O)CF3] (22), and 18 before finally forming the end products 16 and 17, respectively. The
contributions of various factors in dictating the coordination flip of the guanidinate(1−) ligand from κ2(C,N) in 22 and 18 to
κ2(N,N) in 16 and 17, respectively, were unraveled. The mechanism associated with the coordination flip of the guanidinate(1−)
ligand was mapped with the aid of DFT calculations on a model complex, [Pt{κ2(C,N)}{κ2(P,P)}][OC(O)CF3] (22′), which
revealed a pathway involving a Wheland intermediate, F, and further point out that the product, [Pt{κ2(N,N)}{κ2(P,P)}][OC-
(O)CF3] (16′), is a kinetically controlled product.
external base in methanol or a methanol/toluene mixture
under heating conditions. In this method, the role of NaOAc
was thoroughly scrutinized and the OAc− group was shown to
enter into the coordination sphere of the Pt(II) atom during
the course of the cycloplatination reaction.1,7a,8,9
INTRODUCTION
■
Cycloplatinated imine, oxime, ketimine, and related N-donor
complexes have been extensively studied in the literature due
to their relevance in Pt(II)-mediated C−H activation and their
utility as luminescent materials and metallomesogens.1−6 The
mechanism of C−H activation involving Pt(II) salts/
precursors and an appropriate N-donor ligand was shown to
critically depend upon various factors such as the nature of the
Pt(II) precursors, the steric, electronic, and conformational
properties of the N-donor ligands, and the nature of the
external base and solvent.1,7 One of the simplest methods to
cycloplatinate the N-donor ligands is to use cis-[PtCl2(S(O)-
Me2)2] as the Pt(II) precursor in the presence of NaOAc as an
Received: June 15, 2020
https://dx.doi.org/10.1021/acs.organomet.0c00408
© XXXX American Chemical Society
Organometallics XXXX, XXX, XXX−XXX
A

Organometallics
pubs.acs.org/Organometallics
Article
Figure 1. List of known platinacycles 1−6 and new platinacycles 7−9: X = Cl (3), OC(O)CF3 (4−9).
Transition-metal complexes of N-substituted guanidines
have been extensively studied in the literature due to their
rich structural chemistry, their diverse reactivity patterns, and
their promising role as catalysts in organic transforma-
tions.10−13 During the course of the reactions of sym-
N,N′,N″-triarylguanidines, [(ArNH)2CNAr] (sym = sym-
metrical; Ar = tolyl, xylyl, anisyl) with cis-[PtCl2(S(O)Me2)2],
we were able to identify how factors such as the conformations
of the guanidines and the coordinating ability of OAc− from
the external base NaOAc influence the course of Pt(II)-
mediated C−H activation.8 Further, we have also shown that
the reactions of cis-[PtCl2(S(O)Me2)2] in the presence of
NaOAc or the reactions of [Pt(OC(O)R)2(S(O)Me2)2] (R =
Me, CF3) in the absence of base with sym-N,N′,N″-
triarylguanidines afforded the chelate hemichelate platinacycles
1 and 2 and chelate platinacycles 3−6, as illustrated in Figure
1.8,14
The reactions of five-membered cyclometalated imine
complexes A with bisphosphines such as 1,1-bis-
(diphenylphosphino)methane (dppm) and 1,2-bis-
(diphenylphosphino)ethane (dppe) have been studied in the
literature to probe the lability of the M−N bond in the
substrate, A. Such reactions are known to produce cationic
metallacycles B, neutral organometallic complexes C, or a
equilibrated mixture of these products (see Scheme 1).15 The
exact nature of the products was shown to depend upon the
basicity of the N atom, the endocyclic or exocyclic nature of
the >CN double bond inside the [Pt{κ2(C,N)}] ring, and
the bite angle of the bisphosphines. The Pd−N bond in six-
membered cyclopalladated N,N′,N″-tri(2-tolyl)guanidine and
N,N′,N″-tris(2-anisyl)guanidine complexes [Pd{κ2(C,N)}(μ-
NCS)]2 was cleaved smoothly by treating these palladacycles
with an excess of PMe3 to afford trans-[Pd(κ1C-guanidinate-
(1−))(NCS)(PMe3)2].16
Scheme 1. Reactivity of Metallacycles with Chelating
Bisphosphines
We wished to study the reactions of 3−68,14 and 7−9 with
dppm, dppe, and 1,3-bis(diphenylphosphino)propane (dppp)
to investigate the influence of steric and electronic properties
of the guanidinate(1−) ligands in these platinacycles and the
variation of natural bite angles β in dppm (β = 72°), dppe (β =
85°), and dppp (β = 91°)17 upon the lability of the Pt−N
bond in the platinacycles. In this endeavor, we were able to
isolate the anticipated cationic platinacycles 10−15, 18, and 19
and the pair of unanticipated cationic guanidinatoplatinum(II)
complexes 16 and 17 in high yields (see below). The results
pertinent to the syntheses and complete characterization of
both types of cationic Pt(II) complexes are reported in this
paper. The structural isomers 17 and 18 have been successfully
isolated and structurally characterized for the first time. A
plausible mechanism outlining the transformations of 22 to 16
was mapped with 22′ and 16′ via two pathways, and the factors
responsible for the transformation are also outlined.
RESULTS AND DISCUSSION
■
Syntheses and Reactivity Studies. sym-N,N′,N″-tris-
(3,4-xylyl)guanidine, [(ArNH)2CNAr] (Ar = 3,4-
(CH3)2C6H3; LH23,4‑xylyl), was prepared from the reaction of
sym-N,N′-bis(3,4-xylyl)thiourea and 3,4-xylidine in the pres-
ence of 100% aqueous KOH solution in nitrobenzene in 93%
B
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
a
yield following the literature procedure reported for the other
sym-N,N′,N″-triarylguanidines.18 The separate reactions of cis-
[Pt(OC(O)CF3)2(S(O)Me)2] with sym-N,N′,N″-triarylguani-
dines [(ArNH)2CNAr] (Ar = 2,5-Me2C6H3 (LH22,5‑xylyl),
3,4-Me2C6H3 (LH23,4‑xylyl) and 3,5-Me2C6H3 (LH23,5‑xylyl)) in
toluene under reflux conditions for 8 h afforded 7−9 in 83%,
64%, and 78% yields, respectively, following the literature
procedure reported by us for 4−6 (see Scheme 2).14,19
Scheme 3. Syntheses of 10−15, 18, and 19
Scheme 2. Syntheses of Platinacycles 7−9
a
X = Cl (10) and OC(O)CF3 (11−15, 18, and 19).
Cyclopalladation of the imine ligands ArCHNAr′ (Ar =
2,5-Me2C6H3; Ar′ = Ph, 2,4,6-Me3C6H2) was shown to be
solvent- and temperature-dependent.20,21 Thus, cyclopallada-
tion of ArCHNPh (Ar = 2,5-Me2C6H3) with Pd(OAc)2 in
AcOH was unsuccessful even under reflux conditions while the
analogous reaction with ArCHNAr′ (Ar = 2,5-Me2C6H3 and
Ar′ = 2,4,6-Me3C6H2) in toluene at 60 °C for 24 h was shown
to afford the five-membered dinuclear palladacycle [Pd-
chemistry. Platinacycle 19 was subjected to a metathesis
reaction with an excess of NH4PF6 in CH2Cl2 at RT for 24 h
with the aim of obtaining 21, as PF6− is more noncoordinating
−
anion in comparison with OC(O)CF3 , but only platinacycle
20 was formed in 79% yield, as outlined in Scheme 5 (see also
Figure 2). Thus, our attempt to isolate 21 by carrying out a salt
metathesis reaction on 19 with NH4PF6 was not successful;
rather, we were able to isolate only 20 from the
aforementioned reaction.
{κ2(C,N)(μ-OAc)}]2. Our attempts to cyclopalladate the
guanidine LH2
with Pd(OAc)2 was unsuccessful in
The reaction of 9 with dppm was monitored by 31P NMR
spectroscopy, which revealed the formation of the reactive
intermediate 22, as illustrated in Figure 3, before forming 16
(see below). From the fact that we were able to experimentally
detect or isolate both types of structural isomers, namely 22/
16 and 18/17, we summarize the following three criteria which
all need to be fulfilled for the smooth isomeric transformations.
Platinacyclic precursors [Pt{κ2(C,N)}{κ2(P,P)}][OC(O)CF3]
should possess (i) short-bite-angle phosphines such as dppm
and dppe, (ii) a protruding Me substituent on the carbon atom
adjacent to the Pt−C bond in the platinated aryl ring, and (iii)
the Me substituent para to the Pt−C bond in the platinated
aryl ring. Thus, platinacycles 22 and 18 simultaneously satisfy
all three criteria mentioned above and transform to 16 and 17,
respectively while 13−15 satisfy only criterion i, criteria i and
ii, and criteria i and iii, respectively, and thus these
platinacycles are unable to transform to their respective
κ2(N,N) counterparts such as 16 and 17. The faster
transformation of 22 to 16 in comparison to the trans-
formation of 18 to 17 is ascribed to the smaller bite angle of
dppm in 22 than that of dppe in 18. In other words, 22 is more
destabilized than 18 due to the presence of a four-membered
[Pt{κ2(dppm)}] ring in the former complex and this could
provide a lower energy pathway for the former platinacycle to
undergo a faster transformation.28 One can invoke a
combination of several factors for the smooth transformations
of 22 to 16 or 18 to 17 such as steric factors and an
antisymbiosis or transphobia effect.29 The square-planar Pd(II)
2,5‑xylyl
toluene at elevated temperature, which was ascribed to the
steric hindrance posed by the methyl substituent on the C5
carbon atom of one the N(H)Ar units.22 To our surprise, we
2,5‑xylyl
were able to smoothly cycloplatinate both LH2
and
LH23,5‑xylyl with electrophilic cis-[Pt(OC(O)CF3)2(S(O)Me)2]
to afford 7 and 9, respectively, as illustrated in Scheme 2.
The reactions of cycloplatinated N-donor complexes of the
type [Pt{κ2(C,N)}X(S(O)Me2)] (X = Cl, OC(O)CF3) with
bisphosphines such as dppm, dppe, and 1,1′-bis-
(diphenylphosphino)ferrocene are known to produce the
corresponding cationic platinacycles of the type [Pt{κ2(C,N)}-
{κ2(P,P)}][X].15b,c,23−27 The separate reactions of 3−8 with
dppm in CH2Cl2 at RT for 6 h afforded cationic platinacycles
10−15, respectively, in 90%−95% yields (see Scheme 3).
Separate reactions of 9 with dppm and dppe in CH2Cl2 at RT
for 6 and 24 h afforded the unanticipated cationic
guanidinatoplatinum(II) complexes 16 and 17 in 95% and
91% yields, respectively (see Scheme 4). Separate reactions of
9 carried out with dppe and dppp in CH2Cl2 at RT for 6 h
afforded the cationic platinacycles 18 and 19 in 91% and 84%
yields, respectively (see Scheme 3).
The compositions of 17 and 18 are identical, but the
coordination modes of the guanidinate(1−) ligands are
κ2(N,N) and κ2(C,N), respectively, and thus these two
complexes can be considered as structural or linkage isomers.
To the best of our knowledge, this type of isomerism is
unprecedented in metal guanidinate and metallacyclic
C
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Scheme 4. Syntheses of 16 (n = 1) and 17 (n = 2)
−
−
CF3 with PF6 , which allowed us to isolate only 20, as
illustrated in Scheme 5, but not 21 (see Figure 2). This can
likely be attributed to the absence of a short-bite-angle
phosphine in 19 and 20 and thus criterion i is not fulfilled.
Molecular Structures. The molecular structures of 10·
Scheme 5. Synthesis of 20 via a Metathesis Reaction of 19
with NH4PF6
CHCl3, 11·CHCl3, 12·CH2Cl2, 14·1.5C7H8, 15·CH2Cl2, 16,
3,4‑xylyl
17, 18·0.5C7H8, 19·C4H10O, 20·C7H8, and LH2
were
determined by single-crystal X-ray diffraction. Molecular
structures of the aforementioned complexes are illustrated in
Figures 4−8, and that of LH23,4‑xylyl is illustrated in Figure S1 in
the Supporting Information. Salient structural features of the
aforementioned complexes are given in Tables 1−5.
Figure 2. Hitherto unknown guanidinatoplatinum(II) complex 21
anticipated from the transformation illustrated in Scheme 5.
Figure 4. Molecular structure of 10·CHCl3. Solvent molecules and all
hydrogen atoms except those on the amino nitrogen atoms are
removed for clarity.
The Pt(II) atom in [Pt{κ2(C,N)}{κ2(P,P)}][X] is sur-
rounded by the chelating guanidinate(1−) ligand and chelating
dppm (10·CHCl3, 11·CHCl3, 12·CH2Cl2, 14·1.5C7H8, 15·
CH2Cl2), dppe (18·0.5 C7H8), or dppp (19·C4H10O and 20·
C7H8) ligand. The Pt−P bond that is trans to the Pt−C bond
is uniformly longer than the Pt−P bond that is trans to the Pt−
N bond in the aforementioned platinacycles, a feature typical
of cationic platinacycles of this type reported in the literature
(see Table 1).23−26,30−32 The N1−Pt1−C15 bond angle in 10·
CHCl3 (89.4(3)°), 11·CHCl3 (87.6(3)°), 12·CH2Cl2
(88.7(4)°), and 15·CH2Cl2 (87.1(3)°) are wider than the
corresponding angle in 14·1.5C7H8 (84.4(3)°) due to the
presence of a protruding Me substituent on the carbon atom
adjacent to the Pt−C bond in the last complex. The bite angles
Figure 3. 31P NMR spectroscopically detected transient intermediate
formed upon mixing 9 with dppm in CDCl3.
complexes that contain aryl and phosphine ligands in trans
positions are destabilized due to a antisymbiosis or transphobia
effect, as these two ligands are soft in nature and thus compete
with each other for metal electrons. The phosphine and aryl
ligands are trans to each other around the Pt(II) atom in 19,
and its reactivity was further increased by replacing OC(O)-
D
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Figure 5. Molecular structures of 11·CHCl3, 12·CH2Cl2, 14·1.5C7H8, and 15·CH2Cl2. Solvent molecules and all hydrogen atoms except those on
the amino nitrogen atoms are removed for clarity.
Figure 6. Molecular structures of 16 and 17. All hydrogen atoms except those on the amino nitrogen atoms are removed for clarity.
of dppp in 19·C4H10O (89.78(6)°) and 20·C7H8 (89.76(4)°)
as indicted by the P1−Pt1−P2 angles are wider, and hence the
N1−Pt1−C15 bond angles, 82.6(2)° (19·C4H10O) and
82.0(2)° (20·C7H8), become smaller; this trend is opposite
to the trend observed with solvated 10−12, 14, and 15. As the
P1−Pt1−P2 angle increases in the sequence 10·CHCl3, 11·
CHCl3, 12·CH2Cl2, 14·1.5 C7H8, 15·CH2Cl2 > 18·0.5 C7H8 >
19·C4H10O and 20·C7H8, the P2−Pt1−C15 and P1−Pt1−N1
angles decrease due to an increase in steric factors imparted by
the Ph substituents of bisphosphines.17b
plane, as shown in Table 3. The Pt1 atom revealed a distorted-
square-planar geometry, as reflected in the value of θ1. The
magnitude of distortion, θ1, is largely influenced by the degree
of steric factors associated with the Ar substituent of the 
NAr unit. The folding along the N1···C15 vector of the six-
membered [Pt{κ2(C,N)}] ring, denoted θ2, decreases in the
following order. 14·1.5C7H8 ≫ 11·CHCl3 > 15·CH2Cl2 > 10·
CHCl3 ≈ 12·CH2Cl2. The greater folding of the six-membered
[Pt{κ2(C,N)}] ring in 14·1.5C7H8 in comparison to that in 11·
CHCl3 clearly suggests a significant role of the protruding Me
substituent present adjacent to the Pt−C bond in the former
complex. The role of steric factor associated with the NAr
unit in 10·CHCl3 and the presence of a pair of inter- and
intramolecular N−H···O hydrogen bonds in 12·CH2Cl2 and
The six-membered [Pt{κ2(C,N)}] ring in the platinacycles
revealed a pseudoboat conformation with the Pt1 atom and an
endocyclic N3 atom occupying the flagpole positions while the
remaining C1, N1, C14, and C15 atoms occupy the basal
E
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Table 1. Selected Bond Distances (Å) in
[Pt{κ2(C,N)}{κ2(P,P)}][X]
Pt1−N1
Pt1−C15
Pt1−P1
Pt1−P2
10·CHCl3
11·CHCl3
12·CH2Cl2
14·1.5C7H8
15·CH2Cl2
18·0.5C7H8
19·C4H10O
20·C7H8
2.076(7)
2.091(7)
2.088(9)
2.080(7)
2.080(8)
2.095(3)
2.099(5)
2.090(5)
2.042(7)
2.041(9)
2.045(12)
2.060(9)
2.033(9)
2.065(4)
2.069(6)
2.063(4)
2.370(2)
2.370(2)
2.355(4)
2.330(3)
2.336(3)
2.320(1)
2.328(2)
2.334(1)
2.244(2)
2.243(2)
2.243(4)
2.249(2)
2.249(2)
2.228(1)
2.235(2)
2.244(1)
The overlap of the lone pair of the amino N atoms with the
CN π* orbitals of the CN3 unit in the guanidinate(1−)
ligand in the six-membered [M{κ2(C,N)}] (M = Pd, Pt) unit
of pallada- and platinacycles is known as n−π conjugation, and
this stabilizing effect can be quantified from the ρ value.33 A ρ
value of 1.0 indicates a maximum n−π conjugation and a ρ
value of 0.0 indicates a no n−π conjugation. In general, n−π
conjugation in six-membered cyclometalated guanidine com-
plexes are greater than that in their respective uncoordinated
guanidine ligands.8,14,16,18 This trend was also observed in the
structurally characterized platinacycles [Pt{κ2(C,N)}-
{κ2(P,P)}][X] reported in the present investigation (see the
Supporting Information for ρ value of platinacycles and the
respective guanidine ligands).
The Pt(II) atom is simultaneously chelated by the
guanidinate(1−) ligand in a κ2(N,N) coordination mode on
one side and dppm (16) or dppe (17) in a κ2(P,P)
coordination mode on the opposite side and thus becomes a
part of the four-membered [Pt{κ2(N,N)}] ring and the four-
membered [Pt{κ2(dppm)}] ring in 16, while in 17, the Pt(II)
atom is part of the four-membered [Pt{κ2(N,N)}] ring and the
five-membered [Pt{κ2(dppe)}] ring. In both 16 and 17, the
Pt(II) atom revealed a distorted-square-planar geometry, as
reflected in the θ1 value (see Table 5). The N−Pt−P bond
angles in 16 (111.0(1) and 112.5(1)°) are greater than the
corresponding angles in 17 (102.54(9) and 109.36(9)°), as the
bite angle of dppm (72.82(5)°) in the former complex is
smaller than the bite angle of dppe (84.85(4)°) in the latter.
We have shown that for [(η6-p-cymene)Ru(PTA)(κ2(N,N′)-
{(ArN)2CN(H)Ar})][OTf] (Ar = 2-MeC6H4; PTA = 1,3,5-
triaza-7-phosphaadamantane) the lone pair on the N atoms of
Figure 7. Molecular structure of 18·0.5C7H8. Solvent molecules and
all hydrogen atoms except those on the amino nitrogen atoms are
removed for clarity.
15·CH2Cl2, respectively, can be invoked together to explain
the trend associated with θ2 in these platinacycles. The greater
folding of the six-membered [Pt{κ2(C,N)}] ring along the
N1···C15 vector in 18·0.5C7H8, 19·C4H10O, and 20·C7H8 in
comparison to that in the remaining cationic platinacycles can
be correlated to the greater degree of steric pressure exerted by
Ph substituents of dppe and dppp in the former complexes
upon the six-membered [Pt{κ2(C,N)}] ring in comparison to
the Ph substituents of dppm in the latter complexes.17b
The degree of folding of the four-membered [Pt{κ2(P,P)}]
ring along the P···P vector was reflected in the value of θ3,
which is greater for 10·CHCl3 and 12·CH2Cl2 than for of 11·
CHCl3, 14·1.5C7H8, and 15·CH2Cl2. This trend is somewhat
inversely related to the trend observed with θ2, with the
exception being 14·1.5C7H8. Thus, a subtle balance is observed
between folding along the N1···C15 vector of the six-
membered [Pt{κ2(C,N)}] ring and the P···P vector of the
four-membered [Pt{κ2(P,P)}] ring to maintain the distorted-
square-planar geometry of the Pt(II) atom. In the case of 19·
C4H10O and 20·C7H8, the six-membered [Pt{κ2(dppp)}] ring
exhibits a chair conformation with the Pt1 and C21 atoms
occupying the tip and bottom of the chair while P1, P2, C20,
and C22 occupy the basal plane.
Figure 8. Molecular structures of 19·C4H10O and 20·C7H8. Solvent molecules and all hydrogen atoms except those on the amino nitrogen atoms
are removed for clarity.
F
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Table 2. Selected Bond Angles (deg) in [Pt{κ2(C,N)}{κ2(P,P)}][X]
N1−Pt1−C15
P2−Pt1−C15
P1−Pt1−P2
P1−Pt1−N1
P1−Pt1−C15
N1−Pt1−P2
10·CHCl3
11·CHCl3
12·CH2Cl2
14·1.5C7H8
15·CH2Cl2
18·0.5C7H8
19·C4H10O
20·C7H8
89.4(3)
87.6(3)
88.7(4)
84.4(3)
87.1(3)
83.8(1)
82.6(2)
82.0(2)
97.9(2)
96.8(3)
97.1(4)
100.0(2)
98.0(3)
94.7(1)
92.7(2)
93.4(1)
70.84(7)
73.16(9)
71.6(1)
73.24(9)
73.11(9)
83.94(4)
89.78(6)
89.76(4)
102.0(2)
102.9(2)
102.7(3)
101.7(2)
101.8(2)
96.49(9)
94.2(1)
167.7(2)
168.7(3)
168.4(3)
171.5(2)
171.1(3)
172.4(1)
174.1(2)
172.8(1)
172.7(2)
173.1(2)
173.3(3)
171.7(2)
174.3(2)
172.05(9)
170.5(1)
173.2(1)
94.2(1)
Table 3. Key Structural Parameters Illustrating the
Distortion of the [Pt{κ2(C,N)}] Ring and the Pt(II) Atom
in [Pt{κ2(C,N)}{κ2(P,P)}][X]
Table 5. Key Structural Parameters of the Guanidinate(1−)
Ligands in 16 and 17
structural param
16
17
a
θ1 (deg)
θ2 (deg)
θ3 (deg)
6.9(3)
0.5(8)
20.4(7)
0.036(5)
0.053(5)
343
7.9(1)
3.8(4)
13.9(4)
0.002(3)
0.009(3)
352
b
c
ΔCN (Å)
ΔCN′ (Å)
∑N1 (deg)
∑N2 (deg)
∑N3 (deg)
a
b
c
θ1 (deg)
θ2 (deg)
θ3 (deg)
10·CHCl3
11·CHCl3
12·CH2Cl2
14·1.5C7H8
15·CH2Cl2
18·0.5C7H8
19·C4H10O
20·C7H8
5.3(36)
7.99(30)
4.39(26)
8.10(43)
2.59(18)
10.38(18)
9.64(32)
7.92(26)
21.72(47)
26.46(46)
21.67(31)
42.21(44)
23.79(20)
44.64(16)
48.90(29)
46.64(23)
31.86(34)
14.31(32)
28.60(74)
13.65(71)
15.00(57)
27.36(16)
42.05(12)
43.50(11)
360
354
360
349
a
θ1 is the angle between the mean plane defined by the N1Pt1N3 and
b
P1Pt1P2 planes. θ2 is the angle between the mean plane defined by
the N1Pt1N3 and N1C1N3 planes. θ3 is the angle between the mean
plane defined by the N1C1N3 and C8N2H2 planes.
c
in both 16 and 17 is involved in intramolecular N−H···O
hydrogen bonding with the OC(O)CF3 anion. Further, the
bond parameters associated with the CN3 unit of the
guanidinate(1−) ligand in 16 and 17 closely match with the
corresponding bond parameters reported for the guanidi-
nate(1−) ligand in [Pt{κ2(N,N)[(PhN)2C−N(H)Ph]}2] (ΔCN
= 0.025(5) Å, ΔCN′ = 0.050(5) Å; ∑N = 343, 356, 360°).35
Solution Studies. The new complexes were characterized
by conductivity measurements and multinuclear (31P, 195Pt,
1H, 13C, and 19F) NMR spectroscopy. The molar conductance
(ΛM) values of cationic platinacycles prepared in the present
investigation fall in the range 68.4−116.0 Ω−1 cm2 mol−1 (10−3
M) anticipated for 1:1 electrolytes reported in the literature.36
31P NMR spectra of 10−15 revealed a pair of doublets with
each doublet flanked by 195Pt satellites assignable to two
distinct P nuclei of dppm. The δ(31P) shifts of 10−15 and 18−
20 are given in Table 6. Platinacycles 10−15 revealed one
a
θ1 is the angle between the mean plane defined by the N1Pt1C15
and P1Pt1P2 planes. θ2 is the angle between the mean plane defined
by the N1Pt1C15 and N1C1C14C15 planes. θ3 is the angle between
the mean plane defined by the P1C20P2 and P1Pt1P2 planes (10·
CHCl3, 11·CHCl3, 12·CH2Cl2, 14·1.5 C7H8, 15·CH2Cl2), the angle
between the mean plane defined by the P1C20C21P2 and P1Pt1P2
planes (18·0.5C7H8), and the angle between the mean plane defined
by the P1C20C22P2 and P1Pt1P2 planes (19·C4H10O and 20·C7H8).
b
c
the CN3 unit overlaps with the antibonding orbital of the
central C atom to different extents, with the order of overlap
being N1 (syn to H atom of NH(Ar) unit) > N3 (exocyclic N
atom of N(H)Ar unit) > N2 (anti to H atom of NH(Ar)
unit).34 There was a small but significant overlap of the lone
pair on the N3 with the antibonding orbital of the tolyl ring. A
perusal of the C−N distances of the CN3 unit in the
guanidinate(1−) ligands of 16 and 17 suggests a bonding
pattern analogous to that observed in the aforementioned
guanidinatoruthenium(II) complex, although the angle sums
around the N1 and N3 atoms differ more widely in 16. This
stereochemical difference arises due to the difference in the
bite angle of dppe (84.85(4)°) in 17 with that of dppm
(72.82(5)°) in 16. The H atom of the exocyclic −N(H)Ar unit
doublet in the range δ(31PN) −37.8 to −43.9 ppm (1JP−Pt
=
3388−3448 Hz; 1JP−P = 35−39 Hz) assignable to the P nucleus
located trans to the N atom of the [Pt{κ2(C,N)}] chelate and
one doublet in the range δ(31PC) −31.9 to −34.0 ppm (1JP−Pt
=
1463−1504 Hz; 1JP−P = 35−43 Hz) assignable to the P nucleus
located trans to the C atom. The more upfield δ(31PN) shift
value in comparison to the δ(31PC) shift and greater JP−Pt
1
Table 4. Selected Bond Distances (Å) and Bond Angles (deg) in 16 and 17
16
17
16
17
Pt1−N1
Pt1−N3
Pt1−P1
Pt1−P2
2.104(4)
2.073(4)
2.242(1)
2.234(1)
2.107(3)
2.073(3)
2.238(1)
2.226(1)
N1−Pt1−N3
N3−Pt1−P1
P1−Pt1−P2
N1−Pt1−P1
N1−Pt1−P2
N3−Pt1−P2
63.9(2)
175.8(1)
72.82(5)
112.5(1)
172.5(1)
111.0(1)
63.7(1)
171.4(1)
84.85(4)
109.36(9)
165.23(9)
102.54(9)
G
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Table 6. 31P{1H} (161.8 MHz, CDCl3) NMR Chemical Shifts and Coupling Constants for [Pt{κ2(C,N)}{κ2(P,P)}][X]
a
δ(31P) (ppm)
Δ
1JP−Pt (Hz)
1JP−P (Hz)
platinacycle
P trans to N
P trans to C
P trans to N
P trans to C
P trans to N
P trans to C
P trans to N
P trans to C
10
11
12
13
14
15
18
19
−37.8
−37.9
−37.8
−38.2
−43.9
−38.1
32.4
−34.0
−33.6
−31.9
−33.6
−32.6
−32.4
36.2
−14.2
−14.3
−14.2
−14.6
−20.3
−14.5
44.9
−10.4
−10.0
−8.3
−10.0
−9.0
−8.8
48.7
3422
3433
3388
3448
3409
3388
3784
3675
3698
1504
1463
1468
1463
1463
1492
1872
1696
1714
39
35
35
37
39
35
39
39
35
37
43
35
−4.40
−0.45
−0.50
−4.50
12.9
16.85
16.8
12.8
30
30
26
28
b
20
a
37 b
Δ = δ(31P)complex − δ(31P)bis(phosphine); δ(31P) −23.6 ppm (dppm), −12.5 ppm (dppe), and −17.3 ppm (dppp). δ −143.53 (sept, JP−F = 713
Hz) was also observed for PF6 .
1
−
1
value associated with the former P nucleus in the
aforementioned complexes are in line with the literature
trend reported for the related [Pt{κ2(C,N)}{κ2(P,P)}][X] type
platinacycles.15b,c,23−27,31,32 This spectral pattern is ascribed to
a greater trans influence of the platinated carbon in comparison
to that of the imine N atom in this type of platinacycles. The
slightly greater coordination chemical shift,37 Δ = −20.3 ppm,
observed for the P located trans to the N atom in 14 is ascribed
to the influence of steric factors imparted by the Me
substituent on the carbon atom adjacent to the Pt−C bond
in the platinated xylyl ring.
Table 7. δPt (85.78 MHz, CDCl3) and JPt−P Values for
[Pt{κ2(C,N)}{κ2(P,P)}][X]
a
1JPt−P (Hz)
δ(195Pt) (ppm)
P trans to N
P trans to C
10
11
12
13
14
15
18
19
−3819
−3786
−3789
−3755
−3917
−3790
−4546
−4519
3430
3417
3401
3448
3411
3400
3780
3701
1499
1438
1467
1465
1481
1465
1874
1720
1
The δ(31P) shifts and JP−Pt values observed for 10−15 and
1
18 compare favorably with the δ(31P) shifts and JP−Pt values
a
A standard deviation of up to ∼26 Hz was noted in the 1JPt−P values
reported for the six-membered cycloplatinated 2-benzylpyr-
idine complex [Pt{κ2(C,N)}{κ2(dppm)}][BF4]38 and the six-
membered cyloplatinated amine,27 6-alkyl-2,2′-bipyridine,32
benzylpyridine,38 and pyridylphosphane oxide39 complexes of
the type [Pt{κ2(C,N)}{κ2(dppe)}][Cl], respectively. Platina-
cycles 19 and 20 revealed 31P NMR spectral patterns
analogous to those revealed by 13−15; however, δ(31P) shifts
are shifted less upfield in the former platinacycles. The trend
associated with the coordination chemical shift, Δ for 18 > 19
and 20 > 13−15, parallels that known for cis-M-
(CO)4{κ2(P,P)} (κ2(P,P) = dppm, dppe, dppp; M = Cr, Mo,
W).37 31P NMR spectra of 16 and 17 revealed a singlet at
δ(31P) −58.6 ppm (1JP−Pt = 2782 Hz) and δ(31P) 38.2 ppm
(1JP−Pt = 3277 Hz), respectively, with both singlets flanked by
195Pt satellite peaks. The coordination chemical shift observed
for 17 (Δ = 50.7 ppm) is greater than that of 16 (Δ = −35.0
ppm), as anticipated.37
for certain complexes, and this error is acceptable considering the
wide range of about 15000 ppm known in 195Pt NMR.40
−3716 ppm (1JPt−P = 2799 Hz) and δ(195Pt) −4356 ppm
(1JPt−P = 3277 Hz), respectively.
31P NMR Monitoring Experiments. The separate
reactions of 9 with dppm and dppe in CDCl3 at RT were
monitored with time by 31P NMR spectroscopy in order to
investigate the nature of the intermediates formed prior to the
formation of 16 and 17, respectively. The 31P NMR stack plot
for the reaction involving 9 and dppm in CDCl3 is illustrated in
Figure 9. The 31P NMR spectrum of the reaction mixture
recorded immediately after mixing the reactants revealed the
formation of a pair of doublets at δ(31PC) −31.8 (1JP1t−P = 1440
Hz) and δ(31PN) −42.8 ppm (1JPt−P = 3406 Hz), JP−P = 39
Hz, as indicated by blue ● and red ● symbols, respectively.
We assign these signals to a highly reactive species, 22, on the
basis of a comparison of the aforementioned 31P NMR shifts
and coupling constants with those shifts and coupling
constants of 13−15. A minor singlet represented with an
orange ▼ symbol was also observed at δ(31P) −58.8 ppm.
The intensity of this singlet and the associated 195Pt satellites
(1JPt−P = 2783 Hz) grew after 2 h, and this signal was thus
assigned to the P nucleus of dppm in 16. The 31P NMR
spectrum of the reaction mixture recorded after 6 h revealed
the complete disappearance of signals attributed to 22 and the
presence of the signals exclusively attributable to 16.
195Pt NMR spectroscopy is a useful technique to probe the
environment around the square-planar Pt(II) com-
plexes.8,14,40−44 δ(195Pt) values of platinacycles prepared in
the present investigation except for the shift of 20 were
measured and are given in Table 7. 195Pt NMR spectra of 10−
15 revealed a doublet of doublets in the range δ(195Pt) −3755
to −3917 ppm (1JPt−P = 3400−3448 and 1438−1499 Hz) due
to coupling with two distinct P nuclei. The more shielded
δ(195Pt) values observed for 18 and 19 in comparison to those
observed for 13−15 is in line with the literature trend
published for thes types of platinacyles.23,27,45 Remarkably, the
δ(195Pt) shift observed for 14 is more shielded than the shifts
observed for 10−13 and 15, and this spectral feature is
ascribed to the more sterically hindered environment around
the Pt(II) atom in the former complex (see Table 7). 195Pt
NMR spectra of 16 and 17 revealed a triplets at δ(195Pt)
The reaction of 9 with dppe in CDCl3 was much slower, as
revealed by the 31P NMR stack plot illustrated in Figure 10,
possibly due to the greater bite angle of dppe (β = 85°) in
comparison to that of dppm (β = 72°).17 The 31P NMR
spectrum of the reaction mixture containing 9 and dppe in
CDCl3 recorded after 6 h revealed the formation of 18
H
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Figure 9. VT 31P{1H} (161.8 MHz, CDCl3) NMR spectra of an equimolar mixture of 9 and dppm measured (i) immediately, (ii) after 2 h, and
●
●
(iii) after 6 h. The blue and red symbols represent signals of two distinct P nuclei of 22. The asterisks represent the signal of an as yet
unidentified species.
exclusively, as indicated by blue ● and red ● symbols, and
after 12 h the intensity of 31P NMR signals of 18 decreases
with the concomitant growth of 31P NMR signals of 17, as
indicated by an orange ▼ symbol, with the major species
being the former complex. The intensity of 31P NMR signals of
17 grew gradually at the expense of 31P NMR signals of 18
after 12 and 18 h. The 31P NMR signals of 18 completely
disappeared, and those of 17 appeared exclusively after 24 h.
Thus, the variable-time (VT) 31P NMR studies discussed
above point out that 22 and 18 are some of the possible
intermediates formed transiently before the final products 16
and 17, respectively, are formed.
responsible for the conversions of 22 to 16 and of 18 to 17
discussed in the previous sections. In the proposed mechanism
illustrated in Scheme 6, the guanidinate(1−) ligand in 22′
undergoes amine−imine tautomerism to afford D, and this
transformation was calculated to be endergonic in nature by
15.3 kcal/mol. The conversion of D to E proceeds by the
deprotonation of the coordinated amine by the weakly basic
trifluoroacetate anion, and this step was calculated to be
slightly exergonic in nature by 0.9 kcal/mol; thus, this step can
be considered almost thermoneutral. We have recently shown
that the guanidinate(2−) ligand with the anionic charges
residing on the N and the C atoms such as that found in E in
the coordination sphere of Pt(II) could be isolated and
structurally characterized.44 Further, the trifluoroacetic acid
released during the formation of E protonates the platinated
carbon atom of the guanidinate(1−) ligand to afford the
Wheland intermediate F. The formation of F was calculated to
DFT Studies on the Transformation of [Pt{κ2(C,N)}-
{κ2(P,P)}][OC(O)CF3] to [Pt{κ2(N,N)}{κ2(P,P)}][OC(O)CF3].
DFT calculations were carried out on the model complexes
22′ and 16′ and the possible intermediates formed between
these two model complexes to illuminate the driving force
I
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Figure 10. VT 31P{1H} (161.8 MHz, CDCl3) NMR spectra of an equimolar mixture of 9 and dppe measured after (i) 6 h, (ii) 12 h, (iii) 18 h, and
(iv) 24 h. Asterisks represent the signal of an as yet unidentified species.
be slightly endergonic in nature by 3.0 kcal/mol. In other
words, the intermediate E is said to be in a rapid equilibrium
with D on one side and F on the other side in solution at any
moment. Finally, the Wheland intermediate F converts into
16′, and this transformation was calculated to be exergonic by
15.3 kcal/mol.
Protonation of the Pt−C bond in organoplatinum complexes
and mechanistic aspects pertinent to this subject has been
extensively discussed in the literature. Protonation of the Pt−C
bond in organoplatinum complexes can occur via (i) a
concerted SE2 pathway and (ii) stepwise oxidative addition
to the Pt(II) atom followed by reductive elimination, an SEox
pathway.26,46−50 Thus, the protonation of the intermediate E
with trifluoroacetic acid can occur via oxidative addition to
afford the cationic PtIV-hydride species G, and this trans-
formation was calculated to be more exergonic in nature by
63.8 kcal/mol; nevertheless, the formation of 16′ from G via H
is not feasible (see Scheme 7). Probably, the Pt(II) atom in the
model complex 22′ is much less crowded than that in 22 and
thus protonation of the former complex becomes easier and as
a result this step is more exergonic in our calculations. Thus,
the formation of 16′ from the cationic PtIV-hydride species G
via the agostic species H is not feasible due to over-
simplification of steric factors in the models 22′, D, and E.
The facile protonation of the platinated C atom in the
intermediate E by trifluoroacetic acid to afford F is likely due
to the transphobia effect,29 as both the platinated C atom and
the P atom which is located trans to the platinated C atom are
soft in nature. Thus, the platinated C atom could be
nucleophilic enough for fast protonation and as a result the
formation of 16′ is controlled by kinetics. The fact that we
were able to isolate both 16 and 17 only when the platinated
aryl ring in their respective precursors contains Me substituents
in 4,6-positions and not in 3,5-, 3,6-, and 4,5-positions suggests
J
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Scheme 6. DFT Studied Transformation of 22′ to 16′ via the Wheland Intermediate F
Scheme 7. DFT Studied Transformation of 22′ to 16′ via the PtIV-Hydride Species G
the pathway illustrated in Scheme 6 (see Figure 1). The
formations of a Wheland intermediate such as F and an agostic
complex such as H have been invoked as intermediates in the
protonation of organoplatinum(II) phosphine complexes.49,51
spectroscopic techniques and conductivity measurements.
The molecular structures of representative complexes from
both types of complexes were determined by single-crystal X-
ray diffraction (SCXRD). The structural or linkage isomers 17
and 18 are stable enough for isolation and complete
characterization by analytical, spectral, and SCXRD studies,
while 22 was only formed transiently in solution, as inferred
from VT 31P NMR spectroscopy, before forming the stable and
crystallographically characterized complex 16. We have
identified three factors responsible for the 22 to 16 and 18
CONCLUSION
■
Two types of cationic guanidinatoplatinum(II) complexes,
namely [Pt{κ2(C,N)}{κ2(P,P)}][X] and [Pt{κ2(N,N)}-
{κ2(P,P)}][X], were isolated in high yields and fully
characterized by analytical, IR, and multinuclear NMR
K
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
124.92 (d, 1JC−P = 3.9 Hz, P(C6H5)2, ipso-C), 125.17, 125.49 (d, 1JC−P
= 4.7 Hz, P(C6H5)2, ipso-C), 125.71, 126.23 (d, JC−P = 4.8 Hz,
to 17 transformations: namely, steric factors imparted by a Me
substituent ortho to the Pt−C bond, electronic factors
imparted by a Me substituent para to the Pt−C bond to
labilize the Pt−C bond in the six-membered [Pt{κ2(C,N)} ring
of respective Pt(II) substrates, and a greater level of ground-
state destabilization of 22 in comparison to that of 18 due to
the greater steric nature of dppm in the former complex in
comparison to that of dppe in the latter. The transformation of
22′ to 16′ was investigated through DFT calculations, which
point out the possibility of the formation of the Wheland
intermediate F, rather than the frequently reported PtIV−H
intermediate, as one of the key intermediates.
1
P(C6H5)2, ipso-C), 126.61, 127.05, 127.29, 127.42, 128.40, 128.50,
128.55, 128.66, 129.03, 129.16, 129.28, 129.49, 129.61, 130.25,
130.96, 131.01, 131.05, 131.42, 131.85, 132.00, 132.26, 132.59,
132.80, 132.92, 133.45, 133.50, 133.56, 133.61, 133.70, 133.88,
134.01, 137.24, 137.29, 145.59, 146.87, 146.95, 151.51 (ArCH/ArC),
151.92 (CN3). ESI mass m/z [ion]: 955.2504 [M − Cl]+. ΛM (Ω−1
cm2 mol−1, MeCN) = 74.7 (10−3 M).
[Pt{κ2(C,N)-C6H3Me-3-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppm)][OC(O)CF3] (Ar = 2-MeC6H4; 11). Platinacycle 11 was
prepared from platinacycle 4 (40.0 mg, 0.056 mmol) and dppm (21.7
mg, 0.056 mmol) in freshly distilled CH2Cl2 (15 mL) and purified as
described previously for platinacycle 10. The solid obtained from the
reaction mixture was dissolved in CHCl3 (2 mL), layered with toluene
(2 mL), and stored at RT for 4 days to afford 11·CHCl3 as
transparent colorless crystals suitable for SCXRD. Yield: 95% (54.9
mg, 0.053 mmol). Mp: 208.4 °C. Anal. Calcd for PtC49H44O2P2N3F3·
1/5CHCl3 (Mw 1020.9367 + 23.8738 g/mol): C, 56.56; H, 4.26; N,
4.02. Found: C, 56.77; H, 4.49; N, 4.14. ATR-IR (cm−1): ν(N−H)
3402 (w), νa(OCO) 1686 (s), ν(CN) 1616 (m), νs(OCO)
EXPERIMENTAL SECTION
■
[Pt{κ2(C,N)-C6H2Me2-4,5-(NHC(NHAr)(NAr))-2}(OC(O)CF3)-
(S(O)Me2)] (Ar = 3,4-Me2C6H3; 8). cis-[Pt(OC(O)CF3)2(S(O)-
Me2)2] (50.6 mg, 0.087 mmol) and LH2
3,4‑xylyl
(32.5 mg, 0.087
mmol) were placed in a 25 mL round-bottom (RB) flask and
dispersed in toluene (10 mL). The RB flask was fitted with a double
surface condenser capped with a freshly prepared anhydrous CaCl2
guard tube and the reaction mixture refluxed for 8 h and filtered. The
volume of the filtrate was reduced to about one-third of its original
volume and stored at RT for 2 days to afford 8 as colorless crystals.
Yield: 64% (42.8 mg, 0.056 mmol). Mp: 207.6 °C. ATR-IR (cm−1):
ν(N−H) 3366 (m); νa(OCO) 1672 (s); ν(CN) 1640 (m);
νs(OCO) 1317 (m); ν(SO) 1138 (s). Anal. Calcd for
PtC29H34O3N3F3S (Mw: 756.7482 g/mol): C, 46.03; H, 4.53; N,
1
1331(m), ν(P−C6H5) 1103 (s). H NMR (CDCl3, 400 MHz): δ
1.95, 2.00, 2.18 (each s, 3 × 3 H, CH3), 3.96−4.05 (m, 1 H, CH2,
dppm), 4.15−4.24 (m, 1 H, CH2, dppm), 6.39 (t, JHH = 7.4 Hz, 1 H,
ArH), 6.43−6.45 (m, 1 H, ArH), 6.52 (t, JHH = 7.4 Hz, 1 H, ArH),
6.67 (t, JHH = 7.4 Hz, 1 H, ArH), 6.85−6.91 (m, 3 H, ArH), 7.02−
7.06 (m, 1 H, ArH), 7.08−7.14 (m, 3 H, ArH (2 H), NH (1 H)), 7.21
(t, JHH = 7.8 Hz, 1 H, ArH), 7.36−7.47 (m, 7 H, P(C6H5)2), 7.52−
7.59 (m, 8 H, P(C6H5)2), 7.63−7.71 (m, 5 H, P(C6H5)2), 7.95 (s, 1
H, NH). 13C{1H} NMR (CDCl3, 100.5 MHz): δ 17.68 18.01, 18.49
(CH3), 47.31 (dd, 1JC−P = 27.0 and 28.0 Hz, CH2, dppm), 117.46 (q,
1JC−F = 296.6 Hz, CF3), 122.84, 122.90, 122.96, 123.61, 123.67
1
5.55; S, 4.24. Found: C, 45.83; H, 4.34; N, 5.42; S, 4.20. H NMR
(CDCl3, 400 MHz): δ 2.17 (s, 3 H, CH3), 2.23 (br, s, 2 × 3 H, CH3),
2.24, 2.27, 2.29 (each s, 3 × 3 H, CH3), 3.14 (s, 2 × 3 H,
(CH3)2S(O)), 6.25, 6.50 (each s, 2 × 1 H, NH), 6.55 (s, 1 H, ArH),
1
(ArCH/ArC), 124.98 (d, JC−P = 6.7 Hz, P(C6H5)2, ipso-C, dppm),
1
125.53 (d, JC−P = 6.7 Hz, P(C6H5)2, ipso-C, dppm), 125.74, 126.02,
6.82 (d, JHH = 8.0 Hz, 1 H, ArH), 6.86 (s, 1 H, ArH), 6.94 (d, JHH
=
126.41, 126.55, 126.90, 127.56, 128.34, 128.50, 128.69, 129.01,
129.11, 129.18, 129.29, 129.43, 129.54, 130.47, 131.39, 131.45,
131.57, 132.16, 132.25, 132.45, 132.84, 132.96, 133.49, 133.55,
133.62, 133.71, 134.78, 135.90, 136.07, 139.96, 140.11, 148.17,
7.6 Hz, 1 H, ArH), 6.99 (s, 1 H, ArH), 7.12 (d, JHH = 8.0 Hz, 1 H,
ArH), 7.19 (d, JHH = 8.0 Hz, 1 H, ArH), 7.72 (s, JPt−H = 30.8 Hz, 1 H,
ArH). 13C{1H} NMR (CDCl3, 100.5 MHz): δ 19.23, 19.31, 19.36,
19.49, 19.88, 19.90 (CH3), 45.58 ((CH3)2S(O)), 105.01 (ArCH/
2
1
148.23 (ArCH/ArC), 148.28 (CN3), 161.26 (q, JC−F = 32.8 Hz,
ArC), 117.02 (q, JC−F = 292.8 Hz, CF3), 115.97, 123.36, 124.38,
OC(O)). 19F{1H} NMR (CDCl3, 376.31 MHz): δ −74.8. ESI mass
m/z [ion]: 907.2687 [M − OC(O)CF3] +. ΛM (Ω−1 cm2 mol−1,
MeCN) = 103.7 (10−3 M).
127.26, 128.00, 130.93, 131.38, 131.90, 133.08, 133.64, 135.40,
135.70, 136.75, 138.34, 139.19, 140.37 (ArCH/ArC), 148.67 (CN3),
161.56 (q, 2JC−F = 35.6 Hz, OC(O)). 19F{1H} NMR (CDCl3, 376.31
MHz): δ −74.9. 195Pt{1H} NMR (CDCl3, 85.78 MHz): δ −3664. ESI
mass m/z [ion]: 643.2100 [M − OC(O)CF3]+.
[Pt{κ2(C,N)-C6H3Me-5-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppm)][OC(O)CF3] (Ar = 4-MeC6H4; 12). Platinacycle 12 was
prepared from platinacycle 5 (50.0 mg, 0.070 mmol) and dppm (26.9
mg, 0.070 mmol) in CH2Cl2 (15 mL) and purified as described
previously for platinacycle 10. The solid obtained from the reaction
mixture was dissolved in CH2Cl2 (2 mL), layered with toluene (2
mL) and stored at RT for about 3 days to afford 12·CH2Cl2 as
colorless transparent crystals suitable for SCXRD. Yield: 90% (65.1
mg, 0.063 mmol). Mp: 234.9 °C. Anal. Calcd for PtC49H44O2P2N3F3·
0.20 CH2Cl2 (Mw 1020.9367 + 23.8738 g/mol): C, 56.94; H, 4.31; N,
4.05. Found: C, 57.01; H, 4.48; N, 4.02. ATR-IR (cm−1): ν(N−H)
3051 (w), νa(OCO) 1672 (s), ν(CN) 1638 (m), νs(OCO) 1354
[Pt{κ2(C,N)-C6H3(OMe)-3-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppm)]Cl (Ar = 2-(MeO)C6H4; 10). Platinacycle 3 (50.3 mg, 0.073
mmol) and dppm (28.2 mg, 0.073 mmol) were dispersed in freshly
distilled CH2Cl2 (15 mL) in a 25 mL RB flask, and the flask was
capped with a freshly prepared anhydrous CaCl2 guard tube. The
contents in the flask were stirred at RT for 24 h and the volatiles
removed under reduced pressure to afford a light yellow sticky solid.
The solid was triturated with diethyl ether (10 mL) to afford a free-
flowing pale yellow solid. The solid was dissolved in CHCl3 (2 mL),
layered with toluene (2 mL), and stored at RT for about 5 days to
afford 10·CHCl3 as light yellow crystals suitable for SCXRD. Yield:
93% (68.4 mg, 0.068 mmol). Mp: 162.2 °C. Anal. Calcd for
PtC47H44O3P2N3Cl·1/3CHCl3 (Mw 991.3685 + 39.392 g/mol): C,
55.15; H, 4.34; N, 4.08. Found: C, 55.32; H, 4.62; N, 4.19. ATR-IR
(cm−1): ν(N−H) 3368 (m), ν(CN) 1607 (m), ν(P−C6H5) 1101
1
(m), ν(P−C6H5) 1101 (s). H NMR (CDCl3, 400 MHz): δ 1.76,
2.03, 2.20, (each s, 3 × 3 H, CH3), 4.11 (t, 2JPH = 9.8 Hz, 2 H, CH2,
dppm) 6.47−6.51 (m, 4 H, ArH), 6.76−6.78 (m, 2 H, ArH), 6.83−
6.85 (m, 3 H, ArH), 6.91−6.94 (m, 1 H, ArH), 7.01−7.04 (m, 1 H,
ArH), 7.32−7.41 (m, 12 H, P(C6H5)2), 7.48−7.58 (m, 8 H,
P(C6H5)2), 8.03, 9.47 (each s, 2 × 1 H, NH). 13C{1H} NMR
(CDCl3, 100.5 MHz): δ 20.24, 20.77, 20.99, (CH3), 47.47 (dd, 1JC−P
= 34.7 and 35.7 Hz, CH2, dppm), 117.37 (q, 1JC−F = 295.0 Hz, CF3),
116.93, 116.98, 124.24, 124.58, 124.80, 124.99 (ArCH/ArC), 125.57
1
(m). H NMR (CDCl3, 400 MHz): δ 3.52, 3.75, 3.81 (each s, 3 × 3
H, OCH3), 4.00−4.09 (m, 1 H, CH2, dppm), 4.23−4.32 (m, 1 H,
CH2, dppm), 6.40 (d, JHH = 8.4 Hz, 1 H, ArH), 6.48−6.53 (m, 2 H,
ArH), 6.64−6.66 (m, 2 H, ArH (1 H), NH (1 H)), 6.72 (t, JHH = 8.0
Hz, 1 H, ArH), 6.86−6.91 (m, 1 H, ArH), 6.94−7.01 (m, 3 H, ArH),
7.14−7.17 (m, 1 H, ArH), 7.20 (d, JHH = 6.4 Hz, 1 H, ArH), 7.28−
7.36 (m, 5 H, P(C6H5)2), 7.42−7.43 (m, 4 H, P(C6H5)2), 7.49−7.62
(m, 9 H, P(C6H5)2), 7.81−7.86 (m, 2 H, P(C6H5)2), 8.48 (s, 1 H,
NH). 13C{1H} NMR (CDCl3, 100.5 MHz): δ 47.67 (dd, 1JC−P = 26.9
and 27.9 Hz, CH2, dppm), 55.18, 55.77, 56.03 (OCH3), 107.71,
111.37, 111.81, 120.91, 121.15, 122.97, 123.04, 123.10, 123.64,
1
1
(d, JC−P = 5.8 Hz, P(C6H5)2, ipso-C, dppm), 126.12 (d, JC−P = 4.8
Hz, P(C6H5)2, ipso-C, dppm), 126.29, 126.46, 126.87, 127.54 (ArCH/
ArC), 127.80 (d, 1JC−P = 4.8 Hz, P(C6H5)2, ipso-C, dppm), 128.17 (d,
1JC−P = 4.8 Hz, P(C6H5)2, ipso-C, dppm), 128.50, 128.75, 129.01,
129.13, 129.23, 129.31, 129.36, 129.48, 129.87, 130.16, 131.71,
132.26, 133.07, 133.12, 133.18, 133.44, 133.52, 133.56, 133.63,
135.42, 135.46, 135.58, 136.16, 141.33, 141.47, 147.86, 147.91
L
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
2
(ArCH/ArC), 149.27 (CN3), 161.77 (q, JC−F = 35.0 Hz, OC(O)).
19F{1H} NMR (CDCl3, 376.31 MHz): δ −74.8. ESI mass m/z [ion]:
prepared from platinacycle 8 (50.5 mg, 0.066 mmol) and dppm (25.6
mg, 0.066 mmol) in freshly distilled CH2Cl2 (15 mL) and purified as
described previously for platinacycle 10. The solid obtained from the
reaction mixture was dissolved in CH2Cl2 (2 mL), layered with
toluene (2 mL), and stored at RT for 5 days to afford 15·CH2Cl2 as
colorless crystals suitable for SCXRD. Yield: 92% (64.8 mg, 0.061
mmol). Mp: 241.5 °C. Anal. Calcd for PtC52H50O2P2N3F3·1/
4CH2Cl2 (Mw 1063.0177 + 21.2318 g/mol): C, 57.88; H, 4.69; N,
3.88. Found: C, 58.24; H, 4.94; N, 4.02. ATR-IR (cm−1): ν(N−H)
2918 (w), νa(OCO) 1674 (s), ν(CN) 1578 (m), νs(OCO) 1342
907.2639 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1, MeCN) = 86.9
(10−3 M).
[Pt{κ2(C,N)-C6H2Me2-3,5-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppm)][OC(O)CF3] (Ar = 2,4-C6H3; 13). Platinacycle 13 was
prepared from platinacycle 6 (50.0 mg, 0.066 mmol) and dppm (25.4
mg, 0.066 mmol) in freshly distilled CH2Cl2 (15 mL) and purified as
described previously for platinacycle 10. The solid obtained from the
reaction mixture was dissolved in CH2Cl2 (2 mL), layered with
toluene (2 mL), and stored at RT for 2 days to afford 13 as a white
crystalline material. Yield: 95% (67.0 mg, 0.063 mmol). Mp: 148.3
°C. Anal. Calcd for PtC52H50O2P2N3F3 (Mw 1063.0177 g/mol): C,
58.75; H, 4.74; N, 3.95. Found: C, 58.85; H, 4.61; N, 3.83. ATR-IR
(cm−1): ν(N−H) 3402 (w), νa(OCO) 1686 (s), ν(CN) 1605 (m),
1
(m), ν(P−C6H5) 1111 (s). H NMR (CDCl3, 400 MHz): δ 1.60,
1.65, 1.93, 2.08, 2.11, 2.15 (each s, 6 × 3 H, CH3), 4.08 (t, JPH = 9.8
Hz, 2 H, CH2, dppm), 6.38 (s, 1 H, NH), 6.48−6.50 (m, 1 H, ArH),
6.55−6.57 (m, 1 H, ArH), 6.70−6.76 (m, 3 H, ArH), 6.87−7.00 (m, 2
H, ArH), 7.31 (s, 1 H, ArH), 7.35−7.43 (m, 13 H, P(C6H5)2), 7.49−
7.53 (m, 3 H, P(C6H5)2), 7.58−7.62 (m, 4 H, P(C6H5)2), 8.66 (m, 1
H, NH). 13C{1H} NMR (CDCl3, 100.5 MHz): δ 19.78, 20.31, 20.54,
1
νs(OCO) 1348 (m), ν(P−C6H5) 1103 (s). H NMR (CDCl3, 400
MHz): δ 1.70, 1.75, 2.04, 2.08, 2.22, 2.31, (each s, 6 × 3 H, CH3),
4.02−4.11 (m, 1 H, CH2, dppm), 4.16−4.25 (m, 1 H, CH2, dppm)
6.16 (s, 1 H, NH), 6.51−6.53 (m, 2 H, ArH), 6.65 (d, JHH = 8.0 Hz, 1
H, ArH), 6.67 (s, 1 H, ArH), 6.89 (d, JHH = 7.2 Hz, 1 H, ArH), 6.92
(d, JHH = 7.6 Hz, 1 H, ArH), 7.04−7.06 (m, 2 H, ArH), 7.16 (s, 1 H,
NH), 7.22−7.24 (m, 2 H, P(C6H5)2), 7.31−7.36 (m, 2 H, P(C6H5)2),
7.40−7.46 (m, 3 H, P(C6H5)2), 7.48−7.63 (m, 9 H, P(C6H5)2),
1
20.66, 21.14, 21.35 (CH3), 47.45 (dd, JP−C = 27.3 Hz, CH2, dppm),
1
117.39 (q, JC−F = 295.8 Hz, CF3), 116.49, 116.57, 117.32, 117.37,
1
124.60, 125.34 (ArCH/ArC), 125.60 (d, JP−C = 5.7 Hz, P(C6H5)2,
ipso-C, dppm), 125.99, 126.12, 126.17, 126.63, 127.11, 127.86,
128.18, 128.66, 128.73, 128.83, 129.10, 129.44, 129.60, 129.71,
130.19, 131.20, 131.74, 132.18, 132.73, 132.98, 133.01, 133.07,
133.88, 133.92, 134.01, 134.12, 135.47, 135.51, 136.17, 136.21,
7.72−7.83 (m, 4 H, P(C6H5)2). 13C{1H} NMR (CDCl3, 100.5 MHz):
2
1
147.90 (ArCH/ArC), 149.38 (CN3), 161.73 (q, JC−F = 32.6 Hz,
δ 17.58, 17.64, 18.58, 19.88, 20.72, 21.10 (CH3), 47.05 (dd, JC−P
=
OC(O)). 19F{1H} NMR (CDCl3, 376.31): δ −75.0. ESI mass m/z
[ion]: 949.3201 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1, MeCN) =
83.2 (10−3 M).
1
26.9 and 27.9 Hz, CH2, dppm), 117.55 (q, JC−F = 297.3 Hz, CF3),
122.25, 122.31, 124.91, 125.40 (d, JC−P = 4.8 Hz, P(C6H5)2, ipso-C,
dppm), 125.87 (d, JC−P = 5.8 Hz, P(C6H5)2, ipso-C, dppm), 126.24
1
1
[Pt{κ2(N,N)[(ArN)2C(NHAr)]}(κ2(P,P)-dppm)][OC(O)CF3] (Ar =
3,5-Me2C6H3; 16). Platinacycle 16 was prepared from platinacycle 9
(50.3 mg, 0.066 mmol) and dppm (25.5 mg, 0.066 mmol) in freshly
distilled CH2Cl2 (15 mL) and purified as described previously for
platinacycle 10. The solid obtained from the reaction mixture was
dissolved in CH2Cl2 (2 mL), layered with toluene (2 mL), and stored
at RT for about 4 days to afford 16 as bright yellow transparent
crystals suitable for SCXRD. Yield: 95% (67.3 mg, 0.063 mmol). Mp:
232.5 °C. Anal. Calcd for PtC52H50O2P2F3N3 (Mw 1063.0177 g/mol):
C, 58.75; H, 4.74; N, 3.95. Found: C, 58.45; H, 4.35; N, 3.60. ATR-IR
(cm−1): ν(N−H) 3053 (w), νa(OCO) 1676 (s), ν(CN) 1572 (m),
1
1
(d, JC−P = 5.8 Hz, P(C6H5)2, ipso-C, dppm), 126.61 (d, JC−P = 5.8
Hz, P(C6H5)2, ipso-C, dppm), 127.56, 127.72, 127.96, 128.20, 128.58,
128.65, 128.75, 129.09, 129.20, 129.36, 129.49, 129.61, 130.86,
131.09, 131.38, 131.44, 131.50, 132.14, 132.26, 132.40, 132.50,
132.97, 133.32, 133.44, 133.50, 133.61, 134.15, 134.28, 136.08,
137.01, 139.46, 141.17, 141.34, 145.89, 145.95 (ArCH/ArC), 146.99
(CN3) 160.83 (q, JC−F = 31.8 Hz, OC(O)). 19F{1H} NMR (CDCl3,
2
376.31 MHz): δ −74.9. ESI mass m/z [ion]: 949.3534 [M −
OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1, MeCN) = 116.0 (10−3 M).
[Pt{κ2(C,N)-C6H2Me2-3,6-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppm)][OC(O)CF3] (Ar = 2,5-Me2C6H3; 14). Platinacycle 14 was
prepared from platinacycle 7 (45.1 mg, 0.059 mmol) and dppm (22.8
mg, 0.059 mmol) in freshly distilled CH2Cl2 (15 mL) and purified as
described previously for platinacycle 10. The solid obtained from the
reaction mixture was dissolved in CH2Cl2 (2 mL), layered with
toluene (2 mL), and stored at RT for about 7 days to afford 14·
1.5(toluene) as colorless crystals suitable for SCXRD. Yield: 93%
(58.4 mg, 0.055 mmol). Mp: 138.3 °C. Anal. Calcd for
PtC52H50O2P2F3N3·1/2C7H8 (Mw 1063.0177 + 46.0705 g/mol): C,
60.10; H, 4.91; N, 3.79. Found: C, 60.40; H, 5.20; N, 3.98. ATR-IR
(cm−1): ν(N−H) 3051 (w), νa(OCO) 1682 (s), ν(CN) 1605 (m),
1
νs(OCO) 1335 (m), ν(P−C6H5) 1109 (s). H NMR (CDCl3, 400
MHz): δ 1.92 (s, 4 × 3 H, CH3), 2.01 (s, 2 × 3 H, CH3), 5.08 (t,
2JP−H = 11.4 Hz, 2 H, CH2, dppm), 6.31 (br, 4 H, NH (1H), ArH
(3H)), 6.41−6.46 (m, 6 H, ArH), 7.34−7.41 (m, 7 H, P(C6H5)2),
7.50−7.56 (m, 13 H, P(C6H5)2). 31P{1H} NMR (CDCl3, 161.8
MHz): δ −58.6 (1JPt−P = 2782 Hz). 13C{1H} NMR (CDCl3, 100.5
1
MHz): δ 20.94 (CH3), 21.04 (CH3), 44.81 (t, JC−P = 34.7 Hz, CH2,
1
dppm), 117.56 (q, JC−F = 297.3 Hz, CF3), 120.30, 121.75, 122.72,
124.08, 125.24, 125.55, 125.80, 126.32, 126.76, 126.98, 129.00,
129.11, 129.46, 129.51, 129.57, 132.74, 132.96, 133.01, 133.08,
135.79, 137.16, 138.05, 138.26, 138.53, 138.61, 138.89, 140.72,
144.61, 144.97, 147.45, 150.94 (ArCH/ArC), 161.19 (q, 1JC−F = 32.4
1
νs(OCO) 1435 (m), ν(P−C6H5) 1167 (s). H NMR (CDCl3, 400
MHz): δ 1.67, 1.84, 1.95, 1.97 (each s, 4 × 3 H, CH3), 2.25 (br, s, 2 ×
3 H, CH3), 3.72−3.84 (m, 1 H, CH2, dppm), 4.60−4.69 (m, 1 H,
CH2, dppm), 5.77 (s, 1 H, NH), 6.61 (d, JHH = 6.4 Hz, 1 H, ArH),
6.75 (d, JHH = 7.2 Hz, 1 H, ArH), 6.83−6.88 (m, 4 H, ArH (3 H), NH
(1 H)), 7.03−7.10 (m, 1 H, ArH), 7.16−7.18 (m, 2 H, ArH), 7.28−
7.38 (m, 12 H, P(C6H5)2), 7.45−7.54 (m, 4 H, P(C6H5)2), 7.57−7.64
(m, 4 H, P(C6H5)2). 13C{1H} NMR (CDCl3, 100.5 MHz): δ 19.47,
Hz, OC(O)), 165.54 (CN3). 19F{1H} NMR (CDCl3, 376.31): δ
1
−74.6. 195Pt{1H} NMR (CDCl3, 85.78 MHz): δ −3716 (t, JPt−P
=
2799 17 Hz). ESI mass m/z [ion]: 949.3153 [M − OC(O)CF3]+.
ΛM (Ω−1 cm2 mol−1, MeCN) = 68.4 (10−3 M).
[Pt{κ2(N,N)[(ArN)2C(NHAr)]}(κ2(P,P)-dppe)][OC(O)CF3] (Ar =
3,5-Me2C6H3; 17). Platinacycle 17 was prepared from platinacycle 9
(50.2 mg, 0.066 mmol) and dppe (26.4 mg, 0.066 mmol) in freshly
distilled CH2Cl2 (15 mL) in a 25 mL RB flask which was fitted with a
guard tube. The contents in the RB flask were stirred at RT
continuously for 2 days. Subsequently, the volatiles were completely
removed under reduced pressure to afford a light green solid, which
was dissolved in CH2Cl2 (2 mL), layered with toluene (2 mL), and
stored at RT for about 7 days to afford 17 as light green transparent
crystals suitable for SCXRD. Yield: 91% (65.1 mg, 0.060 mmol). Mp:
229.2 °C. Anal. Calcd for PtC53H52O2P2F3N3 (Mw 1077.045 g/mol):
C, 59.10; H, 4.87; N, 3.90. Found: C, 58.81; H, 5.17; N, 3.75. ATR-IR
(cm−1): ν(N−H) 2916 (w), νa(OCO) 1682 (s), ν(CN) 1597 (m),
1
20.00, 20.23, 20.34, 20.83, 21.04 (CH3), 47.13 (dd, JP−C = 27.3 Hz,
CH2, dppm), 117.07 (q, JC−F = 295.8 Hz, CF3), 116.18, 116.25,
117.01, 117.05, 124.28, 125.02 (ArCH/ArC), 125.28 (d, JP−C = 5.7
Hz, P(C6H5)2, ipso-C, dppm), 125.67, 125.81, 125.85, 126.31, 126.78,
127.54, 127.87, 128.34, 128.42, 128.51, 128.78, 129.12, 129.29,
129.39, 129.88, 130.89, 131.42, 131.87, 132.41, 132.66, 132.70,
132.76, 133.57, 133.61, 133.69, 133.81, 135.16, 135.20, 135.86,
1
1
2
135.89, 147.58 (ArCH/ArC), 149.07 (CN3), 161.41 (q, JC−F = 32.6
Hz, OC(O)). 19F{1H} NMR (CDCl3, 376.31 MHz): δ −74.8. ESI
mass m/z [ion]: 949.3146 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1,
MeCN) = 95.0 (10−3 M).
1
[Pt{κ2(C,N)-C6H2Me2-4,5-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
νs(OCO) 1327 (m), ν(P−C6H5) 1111 (s). H NMR (CDCl3, 400
dppm)][OC(O)CF3] (Ar = 3,4-Me2C6H3; 15). Platinacycle 15 was
MHz): δ 1.86 (s, 4 × 3 H, CH3), 1.96 (s, 2 × 3 H, CH3), 2.43−2.56
M
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
1
(m, 2 × 2 H, CH2, dppe), 6.07 (br, s, 4 H, ArH), 6.10 (s, 1 H, NH),
6.32−6.34 (m, 4 H, ArH), 6.38 (s, 1 H, ArH), 7.39−7.44 (m, 7 H,
P(C6H5)2), 7.50−7.55 (m, 13 H, P(C6H5)2). 31P{1H} NMR (CDCl3,
161.8 MHz): δ 38.2 (1JPt−P = 3277 Hz). 13C{1H} NMR (CDCl3,
dppp), 29.53 (d, JC−P = 40.4 Hz, CH2, dppp trans to N), 117.69 (q,
1JC−F = 297.3 Hz, CF3), 113.64, 122.60, 124.01, 125.04, 126.00,
126.61, 126.68, 126.92, 127.37, 127.48, 127.70, 128.37, 128.49,
128.87, 128.98, 129.04, 129.13, 129.27 (ArCH/ArC), 130.00 (d 1JC−P
= 3.8 Hz, P(C6H5)2, ipso-C, dppp), 131.03, 131.08, 131.31, 132.08,
132.47, 132.51, 132.62, 132.76, 132.88, 132.92, 134.86, 136.17,
1
100.5 MHz): δ 20.90 (CH3), 21.01 (CH3), 28.50 (d, JC−P = 6.7 Hz,
CH2, dppe), 28.94 (d, 1JC−P = 6.7 Hz, CH2, dppe), 117.68 (q, 1JC−F
=
1
297.6 Hz, CF3), 120.64, 123.19, 125.32, 125.93, 126.23, 129.29,
136.34, 138.96, 139.64 (ArCH/ArC), 139.97 (d JC−P = 2.9 Hz,
P(C6H5)2, ipso-C, dppp), 140.58 (d 1JC−P = 2.9 Hz, P(C6H5)2, ipso-C,
129.35, 129.41, 132.55, 133.17, 133.23, 133.28, 135.25, 137.94,
2
2
138.14, 143.22, (ArCH/ArC), 160.98 (q, JC−F = 29.9 Hz, OC(O)),
dppp), 142.89, 145.21 (ArCH/ArC), 151.30 (CN3), 161.09 (q, JC−F
167.52 (CN3). 19F{1H} NMR (CDCl3, 376.31): δ −74.5. 195Pt{1H}
NMR (CDCl3, 85.78 MHz): δ −4356 (t, 1JPt−P = 3277 Hz). ESI mass
m/z [ion]: 963.3280 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1,
MeCN) = 69.7 (10−3 M).
= 32.8 Hz, OC(O)). 19F{1H} NMR (CDCl3, 376.31): δ −74.4. ESI
mass m/z [ion]: 977.3485 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1,
MeCN) = 81.4 (10−3 M).
[Pt{κ2(C,N)-(C6H2Me2-4,6-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppp)][PF6] (Ar = 3,5-Me2C6H3; 20). Platinacycle 19 (15.7 mg,
0.014 mmol) was stirred with a large excess of NH4PF6 (15.2 mg,
0.093 mmol) in freshly distilled CH2Cl2 (15 mL) for 24 h at RT in a
25 mL RB flask which was fitted with a freshly prepared anhydrous
CaCl2 guard tube. The reaction mixture was filtered off with
Whatman filter paper to remove NH4OC(O)CF3 and unreacted
NH4PF6. The filtrate was stored at RT over a period of 3 days to
afford 20·(toluene) as colorless transparent crystals suitable for
SCXRD. Yield: 79% (13.2 mg, 0.011 mmol). Mp: 189.7 °C. Anal.
Calcd for PtC52H54P3F6N3 (Mw 1121.0047 g/mol): C, 55.71; H, 4.68;
[Pt{κ2(C,N)-(C6H2Me2-4,6-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppe)][OC(O)CF3] (Ar = 3,5-Me2C6H3; 18). Platinacycle 18 was
prepared from platinacycle 9 (50.1 mg, 0.066 mmol) and dppe (26.4
mg, 0.066 mmol) in freshly distilled CH2Cl2 (15 mL) and purified as
described previously for platinacycle 10. The solid obtained from the
reaction mixture was dissolved in CH2Cl2 (2 mL), layered with
toluene (2 mL), and stored at RT for about 3 days to afford 18·1/
2(toluene) as colorless crystals suitable for SCXRD. Yield: 91% (65.1
mg, 0.060 mmol). Mp: 224.6 °C. Anal. Calcd for PtC53H52O2P2F3N3·
1/4C7H8 (Mw 1077.045 + 23.035 g/mol): C, 59.78; H, 4.95; N, 3.82.
Found: C, 59.96; H, 4.97; N, 4.01. ATR-IR (cm−1): ν(N−H) 3015
(w), νa(OCO) 1684 (s), ν(CN) 1467 (m), νs(OCO) 1373 (m),
1
N, 3.75. Found: C, 55.45; H, 5.01; N, 3.86. H NMR (CDCl3, 400
MHz): δ 1.26−1.35 (m, 1 H, CH2, dppp), 1.96, 2.04 (each s, 2 × 3 H,
CH3), 2.10 (s, 2 × 3 H, CH3), 2.15−2.30 (m, 2 H, CH2, dppp), 2.34
(s, 2 × 3 H, CH3), 2.41−2.60 (m, 3 H, CH2, dppp), 5.64 (s, 2 H,
ArH), 5.94, 6.29 (each s, 2 × 1 H, NH), 6.55 (s, 1 H, ArH), 6.64 (s, 2
× 1 H, ArH), 6.70−6.75 (s, 3 H, ArH), 6.95−7.02 (m, 6 H,
P(C6H5)2), 7.11−7.22 (m, 5 H, P(C6H5)2), 7.33−7.43 (m, 4 H,
P(C6H5)2), 7.59−7.73 (m, 5 H, P(C6H5)2). 19F{1H} NMR (CDCl3,
376.31): δ −73.0 (d, 1JP−F = 715.0 Hz). ΛM (Ω−1 cm2 mol−1, MeCN)
= 84.6 (10−3 M). Platinacycle 20 was sparingly soluble in CDCl3 and
CD3CN, which hampered our attempts to record 195Pt and 13C NMR
spectra with an acceptable signal to noise ratio.
1
ν(P−C6H5) 1107 (s). H NMR (CDCl3, 400 MHz): δ 1.73 (s, 3 H,
CH3), 1.82 (s, 2 × 3 H, CH3), 1.86, 1.96 (each s, 2 × 1 H, CH2,
dppe), 2.07 (s, 2 × 3 H, CH3), 2.13 (s, 3 H, CH3), 2.38−2.51 (m, 2
H, CH2, dppe), 5.96 (s, 2 H, ArH), 6.20 (s, 1 H, ArH), 6.28 (s, 2 H,
ArH), 6.41 (s, 1 H, ArH), 6.62 (s, 1 H, ArH), 6.69 (s, 1 H, ArH),
7.28−7.37 (m, 8 H, P(C6H5)2), 7.46−7.56 (m, 7 H, P(C6H5)2),
7.65−7.66 (m, 3 H, P(C6H5)2), 7.73−7.75 (m, 2 H, P(C6H5)2), 8.53,
8.77 (each s, 2 × 1 H, NH). 13C{1H} NMR (CDCl3, 100.5 MHz): δ
20.59, 21.00, 21.18 (CH3), 26.85 (dd, 1JC−P = 32.8 Hz, 2JC−P = 7.7 Hz,
1
2
CH2, dppe, trans to C), 32.00 (dd, JC−P = 41.9 Hz, JC−P = 14.0 Hz,
1
CH2, dppe, trans to N), 117.62 (q, JC−F = 296.3 Hz, CF3), 114.31,
114.33, 122.53, 123.19, 123.57 (ArCH/ArC), 126.62 (d, JC−P = 6.7
Hz, P(C6H5)2, ipso-C, dppm), 126.88 (ArCH/ArC), 127.35 (d, JC−P
1
ASSOCIATED CONTENT
■
1
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00408.
= 8.6 Hz, P(C6H5)2, ipso-C, dppm), 127.64, 127.75, 128.07, 128.47,
128.59, 128.85, 128.96, 129.19, 129.67, 129.77, 131.08, 131.20,
131.51, 131.71, 131.84, 132.19, 132.46, 132.61, 132.73, 132.87,
133.91, 134.03, 134.46, 134.57, 135.06, 136.86, 138.50, 138.66,
140.69, 143.64, 146.40 (ArCH/ArC), 151.83 (CN3), 161.63 (q, 2JC−F
= 32.7 Hz, OC(O)). 19F{1H} NMR (CDCl3, 376.31): δ −74.7. ESI
mass m/z [ion]: 963.3311 [M − OC(O)CF3]+. ΛM (Ω−1 cm2 mol−1,
MeCN) = 77.7 (10−3 M).
General considerations, syntheses and complete charac-
terization of LH23,4‑xylyl, NMR (1H, 13C, 31P, 195Pt, and
19F) and mass spectra of all new compounds wherever
applicable, crystal acquisition, and refinement SCXRD
data for the structurally characterized compounds 10·
CHCl3, 11·CHCl3, 12·CH2Cl2, 14·1.5C7H8, 15·CH2Cl2,
16, 17, 18·0.5C7H8, 19·C4H10O, 20·C7H8, LH2
and details pertinent to DFT studies, namely figures of
the optimized structures of 22′, D−H, and 16′ (PDF)
[Pt{κ2(C,N)-(C6H2Me2-4,6-(NHC(NHAr)(NAr))-2}(κ2(P,P)-
dppp)][OC(O)CF3] (Ar = 3,5-Me2C6H3; 19). Platinacycle 19 was
prepared from platinacycle 9 (56.5 mg, 0.074 mmol) and dppp (30.8
mg, 0.074 mmol) in freshly distilled CH2Cl2 (15 mL) in a 25 mL RB
flask which was fitted with a guard tube. The contents in the RB flask
were stirred at RT for 24 h. Subsequently, the volatiles were
completely removed under reduced pressure to afford a colorless
sticky solid. The solid was dissolved in CH2Cl2 (2 mL), layered with
diethyl ether (15 mL), and stored at RT for 7 days to afford 19·
C4H10O as colorless transparent crystals suitable for SCXRD. Yield:
84% (67.9 mg, 0.062 mmol). Mp: 218.8 °C. Anal. Calcd for
PtC54H54O2P2F3N3 (Mw 1091.072 g/mol): C, 59.45; H, 4.99; N, 3.85.
Found: C, 59.83; H, 5.12; N, 3.52. ATR-IR (cm−1): ν(N−H) 2916
(w), νa(OCO) 1686 (s), ν(CN) 1574 (m), νs(OCO) 1360 (m),
ν(P−C6H5) 1105 (s). 1H NMR (CDCl3, 400 MHz): δ 1.28−1.41 (m,
1 H, CH2, dppp), 1.93 (s, 3 H, CH3), 2.02 (br, 1 H, CH2, dppp), 2.05
(s, 2 × 3 H, CH3), 2.07 (s, 3 H, CH3), 2.09−2.22 (m, 1 H, CH2,
dppp), 2.25 (s, 2 × 3 H, CH3), 2.47−2.67 (m, 3 H, CH2, dppp), 5.65
(s, 2 H, ArH), 5.94 (s, 1 H, NH), 6.51 (s, 2 H, ArH), 6.71 (s, 1 H,
ArH), 6.73−6.76 (m, 2 H, ArH), 6.84 (s, 1 H, ArH), 6.91−6.99 (m, 4
H, P(C6H5)2), 7.09−7.21 (m, 7 H, P(C6H5)2), 7.31−7.43 (m, 4 H,
P(C6H5)2), 7.63−7.73 (m, 5 H, P(C6H5)2), 7.93 (s, 1 H, NH).
13C{1H} NMR (CDCl3, 100.5 MHz): δ 19.46, 20.32, 21.22, 21.30,
3,4‑xylyl
Cartesian coordinates of the calculated structures (XYZ)
Accession Codes
CCDC 2003713−2003723 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
■
Corresponding Author
Natesan Thirupathi − Department of Chemistry, University of
Delhi, Delhi 110 007, India; orcid.org/0000-0002-1110-
2681; Email: tnat@chemistry.du.ac.in, thirupathi_n@
yahoo.com
(CH3), 27.15 (d, 1JC−P = 30.9 Hz, CH2, dppp trans to C), 27.72 (CH2,
N
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
(8) Elumalai, P.; Thirupathi, N.; Nethaji, M. Dual Role of Acetate as
a Nucleophile and as an Internal Base in Cycloplatination Reaction of
sym-N,N′,N″-Triarylguanidines. Inorg. Chem. 2013, 52, 1883−1894.
(9) Marcos, I.; Ojea, V.; Vazquez-García, D.; Fernandez, J. J.;
Fernandez, A.; Lopez-Torres, M.; Lado, J.; Vila, J. M. Preparation and
Characterization of Terdentate [C,N,N] Acetophenone and Acetyl-
pyridine Acetylpyridine Hydrazone Platinacycles: A DFT Insight into
the Reaction Mechanism. Dalton Trans. 2017, 46, 16845−16860.
(10) (a) Bailey, P. J.; Pace, S. The Coordination Chemistry of
Guanidines and Guanidinates. Coord. Chem. Rev. 2001, 214, 91−141.
(b) Jones, C. Bulky Guanidinates for the Stabilization of Low
Oxidation State Metallacycles. Coord. Chem. Rev. 2010, 254, 1273−
1289. (c) Francos, J.; Cadierno, V. The Chemistry of Guanidinate
Complexes of the Platinum Group Metals. Dalton Trans. 2019, 48,
9021−9036.
Authors
Rishabh Ujjval − Department of Chemistry, University of Delhi,
Delhi 110 007, India
Masilamani Deepa − Postgraduate and Research Department of
Chemistry, Muthurangam Government Arts College
(Autonomous), Vellore 632 002, Tamil Nadu, India
Jisha Mary Thomas − Catalysis and Energy Laboratory,
Department of Chemistry, Pondicherry University (A Central
University), Pondicherry 605 014, India
Chinnappan Sivasankar − Catalysis and Energy Laboratory,
Department of Chemistry, Pondicherry University (A Central
University), Pondicherry 605 014, India
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00408
(11) Bazinet, P.; Wood, D.; Yap, G. P. A.; Richeson, D. S. Synthesis
and Structural Investigation of N,N′,N″-Trialkylguanidinato-Sup-
ported Zirconium(IV) Complexes. Inorg. Chem. 2003, 42, 6225−
6229.
Notes
The authors declare no competing financial interest.
(12) Coles, M. P. Bicyclic-Guanidines, -Guanidinates and
-Guanidinium Salts: Wide Ranging Applications from a Simple
Family of Molecules. Chem. Commun. 2009, 3659−3676.
(13) Cui, X.-Y.; Tan, C.-H.; Leow, D. Metal-Catalysed Reactions
Enabled by Guanidine-type Ligands. Org. Biomol. Chem. 2019, 17,
4689−4699.
ACKNOWLEDGMENTS
■
This work was supported by Department of Science and
Technology (DST), New Delhi. R.U. acknowledges the DST
for a fellowship.
(14) Mishra, V.; Thirupathi, N. Critical Role of Anions in
Platinum(II) Precursors upon the Structural Motifs of Six-Membered
Cycloplatinated N,N′,N″-Triarylguanidines. ACS Omega 2018, 3,
6075−6090.
REFERENCES
■
(1) Wu, Y.; Huo, S.; Gong, J.; Cui, X.; Ding, L.; Ding, K.; Du, C.;
Liu, Y.; Song, M. Studies on the Cyclometallation of Ferrocenyli-
mines. J. Organomet. Chem. 2001, 637−639, 27−46.
́
(15) (a) Albert, J.; Gomez, M.; Granell, J.; Sales, J.; Solans, X. Five-
and Six-Membered Exo-Cyclopalladated Compounds of N-Benzyli-
deneamines. Synthesis and X-ray Crystal Structure of [PdBr{p-
MeOC6H3(CH2)2NCH(2,6-Cl2C6H3)}(PPh3)] and [PdBr-
{C6H4CH2NCH(2,6-Cl2C6H3)}(PEt3)2]. Organometallics 1990, 9,
(2) (a) Ryabov, A. D.; Otto, S.; Samuleev, P. V.; Polyakov, V. A.;
Alexandrova, L.; Kazankov, G. M.; Shova, S.; Revenco, M.; Lipkowski,
J.; Johansson, M. H. Structural and Mechanistic Look at the
Orthoplatination of Aryl Oximes by Dichlorobis(sulfoxide or
sulfide)platinum(II) Complexes. Inorg. Chem. 2002, 41, 4286−4294.
(b) Otto, S.; Chanda, A.; Samuleev, P. V.; Ryabov, A. D. DFT-
Verified Crystallographic Mechanism of Cycloplatination. Eur. J.
Inorg. Chem. 2006, 2006, 2561−2565.
́
1405−1413. (b) Capape, A.; Crespo, M.; Granell, J.; Font-Bardía, M.;
Solans, X. A Comparative Study of the Structures and Reactivity of
Cyclometallated Platinum Compounds of N-Benzylidenebenzyl-
amines and Cycloplatination of a Primary Amine. Dalton Trans.
2007, 20, 2030−2039. (c) Zheng, F.; Hutton, A. T.; van Sittert, C. G.
C. E.; Gerber, W. J.; Mapolie, S. F. Cyclometallated Platinum(II)
Complexes of Benzylidene-2,6-di-isopropylphenylamine Containing
Bidentate Phosphines: Synthesis, Structural Properties and Reactivity
Studies. Dalton Trans. 2015, 44, 1969−1981.
(3) Scaffidi-Domianello, Y. Yu; Nazarov, A. A.; Haukka, M.;
Galanski, M.; Keppler, B. K.; Schneider, J.; Du, P.; Eisenberg, R.;
Kukushkin, V. Yu First Example of the Solid-State Thermal
Cyclometalation of Ligated Benzophenone Imine Giving Novel
Luminescent Platinum(II) Species. Inorg. Chem. 2007, 46, 4469−
4482.
(4) Pandya, S. U.; Moss, K. C.; Bryce, M. R.; Batsanov, A. S.; Fox,
M. A.; Jankus, V.; Al Attar, H. A.; Monkman, A. P. Luminescent
Platinum(II) Complexes Containing Cyclometallated Diaryl Ketimine
Ligands: Synthesis, Photophysical and Computational Properties. Eur.
J. Inorg. Chem. 2010, 2010, 1963−1972.
(5) Bilgin-Eran, B.; Ocak, H.; Tschierske, C.; Baumeister, U.
Synthesis and Mesomorphism of Fluoroalkylated Platinum Com-
plexes. Liq. Cryst. 2012, 39, 467−476.
(6) (a) Crespo, M. Fluorine in Cyclometalated Platinum
Compounds. Organometallics 2012, 31, 1216−1234. (b) Crespo, M.
Diarylplatinum(II) Compounds as Versatile Metallating Agents in the
Synthesis of Cyclometallated Platinum Compounds with N-Donor
Ligands. Inorganics 2014, 2, 115−131.
(7) (a) Crespo, M.; Font-Bardía, M.; Granell, J.; Martinez, M.;
Solans, X. Cyclometallation on Platinum(II) Complexes; the Role of
the Solvent and Added Base Donor Capability on the Reaction
Mechanisms. Dalton Trans. 2003, 3763−3769. (b) Capape, A.;
Crespo, M.; Granell, J.; Vizcarro, A.; Zafrilla, J.; Font-Bardia, M.;
Solans, X. Unprecedented Intermolecular C−H Bond Activation of a
Solvent Toluene Molecule leading to a Seven-membered Platinacycle.
Chem. Commun. 2006, 4128−4130. (c) Crespo, M.; Martín, R.;
Calvet, T.; Font-Bardía, M.; Solans, X. Novel Platinum(II)
Compounds with N-Benzylidenebenzylamines: Synthesis, Crystal
Structures and the Effect of cis or trans Geometry on Cycloplatination.
Polyhedron 2008, 27, 2603−2611.
(16) Saxena, P.; Thomas, J. M.; Sivasankar, C.; Thirupathi, N.
Syntheses and Structural Aspects of Six-membered Palladacyclic
Complexes Derived from N,N′,N″-Triarylguanidines with N- or S-
Thiocyanate Ligands. New J. Chem. 2019, 43, 2307−2327.
(17) (a) Dierkes, P.; van Leeuwen, P. W. N. M. The Bite Angle
Makes the Difference: A Practical Ligand Parameter for Diphosphine
Ligands. J. Chem. Soc., Dalton Trans. 1999, 1519−1529. (b) Mansell,
S. M. Catalytic Applications of Small Bite-angle Diphosphorus
Ligands with Single-atom Linkers. Dalton Trans. 2017, 46, 15157−
15174.
(18) Gopi, K.; Rathi, B.; Thirupathi, N. Synthesis and Conforma-
tional Features of Sym N,N′,N″-Triarylguanidines. J. Chem. Sci. 2010,
122, 157−167.
(19) Sinha, N. K.; Mishra, V.; Nethaji, M.; Thirupathi, N.
Unpublished Results.
(20) Albert, J.; Ceder, R. M.; Gomez, M.; Granell, J.; Sales, J.
Cyclopalladation of N-Mesitylbenzylideneamines. Aromatic versus
Aliphatic C−H Activation. Organometallics 1992, 11, 1536−1541.
(21) Vazquez-Garcia, D.; Fernandez, A.; Lopez-Torres, M.;
Rodriguez, A.; Gomez-Blanco, N.; Viader, C.; Vila, J. M.;
Fernandez, J. J. Versatile Behavior of the Schiff Base Ligand 2,5-
Me2C6H3C(H)N(2,4,6-Me3C6H2) toward Cyclometalation Reac-
tions: C(sp2, phenyl)−H vs C(sp3, methyl)−H Activation. Organo-
metallics 2010, 29, 3303−3307.
(22) Elumalai, P.; Ujjval, R.; Nethaji, M.; Thirupathi, N. Syntheses,
Characterization, Solution Behavior and Catalytic Activity of Trans-
O
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
t
[(guanidine)2PdX2] (X = Cl and OC(O)R; R = Me, Ph and Bu) in
Heck−Mizoroki Coupling Reactions Involving Chloroarenes/Methyl
Acrylate. Polyhedron 2018, 151, 313−322.
(38) Minghetti, G.; Zucca, A.; Stoccoro, S.; Cinellu, M. A.;
Manassero, M.; Sansoni, M. Six-Membered Cyclometallated Deriva-
tives of Platinum(II) Derived from 2-Benzylpyridines. Crystal and
Molecular Structure of [Pt(L)(Ph3P)Cl] (HL = 2-(l-methylbenzyl)-
pyridine). J. Organomet. Chem. 1994, 481, 195−204.
(39) Minghetti, G.; Doppiu, A.; Stoccoro, S.; Zucca, A.; Cinellu, M.
A.; Manassero, M.; Sansoni, M. Reactivity of Ph2P(O)py-2 with
Platinum(II) Alkyl Derivatives−Building-up of a Chiral Phosphorus
Atom through C,N-Cyclometallation. Eur. J. Inorg. Chem. 2002, 2002,
431−438.
(23) Duffy, N. W.; McAdam, C. J.; Robinson, B. H.; Simpson, J.
Phosphine Complexes of Platinum(II) Cycloplatinated Ferrocenyl-
amines. Inorg. Chem. 1994, 33, 5343−5350.
(24) Aghakhanpour, R. B.; Nabavizadeh, S. M.; Rashidi, M.; Kubicki,
M. Luminescence Properties of Some Monomeric and Dimeric
Cycloplatinated(II) Complexes Containing Biphosphine Ligands.
Dalton Trans. 2015, 44, 15829−15842.
(25) Barzegar-Kiadehi, S. R.; Haghighi, M. G.; Jamshidi, M.; Notash,
B. Influence of the Diphosphine Coordination Mode on the Structural
and Optical Properties of Cyclometalated Platinum(II) Complexes:
An Experimental and Theoretical Study on Intramolecular Pt···Pt and
π···π Interactions. Inorg. Chem. 2018, 57, 5060−5073.
(26) Haghighi, M. G.; Nabavizadeh, S. M.; Rashidi, M.; Kubicki, M.
Selectivity in Metal−carbon Bond Protonolysis in p-tolyl- (or
methyl)-Cycloplatinated(II) Complexes: Kinetics and Mechanism of
the Uncatalyzed Isomerization of the Resulting Pt(II) Products.
Dalton Trans. 2013, 42, 13369−13380.
(27) Clemente, M.; Polat, I. H.; Albert, J.; Bosque, R.; Crespo, M.;
Granell, J.; Lopez, C.; Martínez, M.; Quirante, J.; Messeguer, R.;
Calvis, C.; Badía, J.; Baldoma, L.; Font-Bardia, M.; Cascante, M.
(40) Priqueler, J. R. L.; Butler, I. S.; Rochon, F. D. An Overview of
195Pt Nuclear Magnetic Spectroscopy. Appl. Spectrosc. Rev. 2006, 41,
185−226.
(41) Still, B. M.; Anil Kumar, P. G.; Aldrich-Wright, J. R.; Price, W.
S. 195Pt NMRTheory and Application. Chem. Soc. Rev. 2007, 36,
665−686.
(42) Fuertes, S.; Chueca, A. J.; Sicilia, V. Exploring the Transphobia
Effect on Heteroleptic NHC Cycloplatinated Complexes. Inorg. Chem.
2015, 54, 9885−9895.
(43) Sicilia, V.; Arnal, L.; Chueca, A. J.; Fuertes, S.; Babaei, A.;
Munoz, A. M. I.; Sessolo, M.; Bolink, H. J. Highly Photoluminescent
̃
Blue Ionic Platinum-Based Emitters. Inorg. Chem. 2020, 59, 1145−
1152.
̀
(44) Thakur, V.; Thirupathi, N. Syntheses and Structural aspects of
Dinuclear Cycloplatinated N,N′,N″-Triarylguanidinate(2−) Com-
plexes with a Novel Tridentate μ2-κ2(C,N):κ1N Coordination Mode.
J. Organomet. Chem. 2020, 911, 121138−121143.
Platinacycles Containing a Primary Amine Platinum(II) Compounds
for Treating Cisplatin-Resistant Cancers by Oxidant Therapy.
Organometallics 2018, 37, 3502−3514.
(28) Van Zeist, W.-J.; Visser, R.; Bickelhaupt, F. M. The Steric
Nature of the Bite Angle. Chem. - Eur. J. 2009, 15, 6112−6115.
(29) Vicente, J.; Arcas, A.; Bautista, D.; Jones, P. G. The Difficulty of
Coordinating Mutually trans Phosphine and Aryl Ligands in
Palladium Complexes and Its Relation to Important Coupling
Processes. Syntheses and Crystal Structures of a Family of Palladium
Phosphino, Triflato, Perchlorato, and Aquo-2-(arylazo)aryl Com-
plexes. Organometallics 1997, 16, 2127−2138.
́
(45) Albert, J.; Bosque, R.; Crespo, M.; Granell, J.; Lopez, C.;
́
Martín, R.; Gonzalez, A.; Jayaraman, A.; Quirante, J.; Calvis, C.;
̀
Badía, J.; Baldoma, L.; Font-Bardia, M.; Cascante, M.; Messeguer, R.
Neutral and Ionic Platinum Compounds Containing a Cyclo-
metallated Chiral Primary Amine: Synthesis, Antitumor Activity,
DNA Interaction and Topoisomerase I−Cathepsin B Inhibition.
Dalton Trans. 2015, 44, 13602−13614.
(46) Romeo, R.; Minniti, D.; Lanza, S.; Uguagliati, P.; Belluco, U.
Mechanism of Electrophilic Cleavage of the Platinum-Carbon Bond in
Platinum(II)-Diaryl Complexes. Inorg. Chem. 1978, 17, 2813−2818.
(47) Jawad, J. K.; Puddephatt, R. J.; Stalteri, M. A. Selectivity in
Reactions of Alkyl-Aryl-Transition-Metal Complexes with Electro-
philes. Inorg. Chem. 1982, 21, 332−337.
(48) Romeo, R.; Plutino, M. R.; Elding, L. I. Protonolysis of Dialkyl-
and Alkylarylplatinum(II) Complexes and Geometrical Isomerization
of the Derived Monoorgano−Solvento Complexes: Clear-Cut
Examples of Associative and Dissociative Pathways in Platinum(II)
Chemistry. Inorg. Chem. 1997, 36, 5909−5916.
(30) DePriest, J.; Zheng, G. Y.; Woods, C.; Rillema, D. P.; Mikirova,
N. A.; Zandler, M. E. Structure, Physical and Photophysical Properties
of Platinum(II) Complexes Containing 7,8-Benzoquinoline and
Various Bis(diphenylphosphine) Ligands. Inorg. Chim. Acta 1997,
264, 287−296.
(31) DePriest, J.; Zheng, G. Y.; Goswami, N.; Eichhorn, D. M.;
Woods, C.; Rillema, D. P. Structure, Physical, and Photophysical
Properties of Platinum (II) Complexes Containing Bidentate
Aromatic and Bis(diphenylphosphino)methane as Ligands. Inorg.
Chem. 2000, 39, 1955−1963.
(32) Zucca, A.; Stoccoro, S.; Cinellu, M. A.; Minghetti, G.;
Manassero, M.; Sansoni, M. Metallation of Unactivated Methyl
Groups−Platinum(II) Derivatives with 6-Alkyl-2,2′-bipyridines. Eur.
J. Inorg. Chem. 2002, 2002, 3336−3346.
(49) Kalberer, E. W.; Houlis, J. F.; Roddick, D. M. Protolytic
Stability of (dfepe)Pt(Ph)O2CCF3: Supporting Evidence for a
Concerted SE2 Protonolysis Mechanism. Organometallics 2004, 23,
4112−4115.
(50) Fard, M. A.; Behnia, A.; Puddephatt, R. J. Cycloneophylpla-
tinum Chemistry: A New Route to Platinum(II) Complexes and the
Mechanism and Selectivity of Protonolysis of Platinum−Carbon
Bonds. Organometallics 2018, 37, 3368−3377.
(51) Hu, J.; Yip, J. H. K. Regioselective Double Cycloplatination of
9,10-Bis(diphenylphosphino)anthracene. Organometallics 2009, 28,
1093−1100.
̌
(33) Raab, V.; Harms, K.; Sundermeyer, J.; Kovacevic, B.; Maksic, Z.
B. 1,8-Bis(dimethylethyleneguanidino)naphthalene: Tailoring the
Basicity of Bisguanidine “Proton Sponges” by Experiment and
Theory. J. Org. Chem. 2003, 68, 8790−8797.
(34) Kishan, R.; Kumar, R.; Baskaran, S.; Sivasankar, C.; Thirupathi,
N. Ionic and Neutral Half-Sandwich Guanidinatoruthenium(II)
Complexes and Their Solution Behavior. Eur. J. Inorg. Chem. 2015,
2015, 3182−3194.
(35) Bailey, P. J.; Grant, K. J.; Mitchell, L. A.; Pace, S.; Parkin, A.;
Parsons, S. Guanidinates as Chelating Anionic Ligands for Early,
Middle and Late Transition Metals: Syntheses and Crystal Structures
of [Ti{η2-(NPh)2CNEt2}2Cl2], [Ru{η2-(NPh)2CNHPh}3] and [Pt-
{η2-(NPh)2CNHPh}2]. J. Chem. Soc., Dalton Trans. 2000, 1887−
1891.
(36) Geary, W. J. The Use of Conductivity Measurements in
Organic Solvents for the Characterisation of Coordination Com-
pounds. Coord. Chem. Rev. 1971, 7, 81−122.
(37) Garrou, P. E. ΔR Ring Contributions to 31P NMR Parameters
of Transition-Metal-Phosphorus Chelate Complexes. Chem. Rev.
1981, 81, 229−266.
P
https://dx.doi.org/10.1021/acs.organomet.0c00408
Organometallics XXXX, XXX, XXX−XXX