Correlating Pt-P bond lengths and Pt-P coupling constants

Article abstract of DOI:10.1039/c003256e

The X-ray structures of (5) cis-PtBr₂(P(OMe)₃) ₂, (6) cis-PtBr₂(P(OMe)₂Ph)₂, (7) cis-PtBr₂(P(OMe)Ph₂)₂, (8) cis-PtBr ₂(PPh₃)₂

Full text of DOI:10.1039/c003256e

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PAPER
www.rsc.org/dalton | Dalton Transactions
Correlating Pt–P bond lengths and Pt–P coupling constants†
Paul G. Waddell, Alexandra M. Z. Slawin and J. Derek Woollins*
Received 16th February 2010, Accepted 8th June 2010
DOI: 10.1039/c003256e
The X-ray structures of (5) cis-PtBr2(P(OMe)3)2, (6) cis-PtBr2(P(OMe)2Ph)2, (7) cis-PtBr2(P(OMe)Ph2)2,
(8) cis-PtBr2(PPh3)2, (9) cis-PtI2(P(OMe)3)2, (10) cis-PtI2(P(OMe)2Ph)2, (11) cis-PtI2(P(OMe)Ph2)2 and
(12) cis-PtI2(PPh3)2 are reported and compared with the previously reported chloride analogues. The
magnitude of the J{Pt–P} varies linearly with the Pt–P bond length (lPt–P = 2.421 - J/24255) for these
12 complexes.
crystallography were grown by slow diffusion of hexane into
Introduction
a solution of the complex in dichloromethane for all except
cis-PtBr2(PPh3)2 (grown by slow diffusion of hexane into a
solution of the complex in chloroform).
As a consequence of their interesting reactivity and since the
discovery of the anticancer action of cis-platin1 the study of square
planar platinum complexes has been of great interest. Platinum
complexes containing phosphorus ligands are of particular interest
as their 31P NMR spectra contain 195Pt satellite peaks which allow
the 31P–195Pt coupling constant to be measured giving insight
into the nature of bonding around the platinum centre.2 Previous
studies have shown in a limited range of compounds that there
is a crude correlation between the P–Pt bond length and the 31P–
195Pt coupling constant.3–5 Here we report the crystal structures
of a series of cis-PtX2(P(OMe)nPh3-n)2 (X = Br or I; n = 0–3)
and compare them to their cis-PtCl2(P(OMe)nPh3-n)2 analogues to
create a series with coupling constants in the range 3450–5750 Hz
and show that the relationship between their 31P–195Pt coupling
constant and Pt–P bond length is linear.
Preparation of cis-PtI2(P(OMe)2Ph)2
1 g (1.53 mmol) of trans-PtI2(PhCN)2 was vigorously stirred in
40 mL acetone to which 0.48 mL (3.05 mmol) of P(OMe)2Ph
was added affording a clear yellow solution. The volume of
acetone was reduced to ca. 10 mL with a yellow precipitate
of cis-PtI2(P(OMe)2Ph)2 forming. The remaining product was
precipitated upon addition of 50 mL diethyl ether. The solid was
filtered and washed with diethyl ether to give a crystalline, yellow
solid, mp 172–174◦. Crystals were grown for X-ray crystallography
by slow diffusion of hexane into a solution of the product in
dichloromethane. Yield: 0.632 g (0.8 mmol), 52%. Elemental
Analysis (%, calculated in brackets): C, 24.65 (24.35); H, 2.51
1
(2.81). H NMR (CDCl3, 291 K): d(ppm) = 3.66 (d, 12H, methyl,
Experimental
1
3JPH = 12.9 Hz), d(ppm) = 7.41–7.77 (m, 10H, phenyl). 31P{ H}
NMR (C6D6, 295 K): d(ppm) = 96.4 (1J
= 4618 Hz). Infra red:
Unless otherwise stated all manipulations were performed under
an oxygen-free nitrogen atmosphere, using standard Schlenk tech-
niques and glassware. Solvents were dried and stored according
to common procedures. Reagents were obtained from Aldrich
P–Pt
nPt–I 163, 150 cm-1, nPt–P 202, 188 cm-1, nP–O-alkyl 1045 cm-1, nP–Ph
1434 cm-1.
and used without further purification. Solution state 31P–{ H}
1
Preparation of cis-PtI2(P(OMe)Ph2)2
(109 MHz, Table 1) and 1H (270 MHz) NMR spectra were
recorded using a JEOL GSX Delta 270. IR spectra were recorded
using KBr discs on a Perkin-Elmer System 2000 FT spectrometer.
Microanalyses were performed by the University of St. Andrews
microanalysis service.
1 g (1.53 mmol) of trans-PtI2(PhCN)2 was vigorously stirred in
40 mL acetone to which 0.61 mL (3.05 mmol) of P(OMe)Ph2
was added affording a clear yellow solution. The volume of
acetone was reduced to ca. 10 mL with a yellow precipitate of
cis-PtI2(P(OMe)2Ph)2 forming. The solid was filtered and washed
with diethyl ether to give a yellow powder, mp 182–186◦. Crystals
were grown for X-ray crystallography by slow diffusion of hexane
into a solution of the product in dichloromethane. Yield: 1.255 g
(1.43 mmol), 93%. Elemental Analysis (%, calculated in brackets):
cis-PtBr2(P(OMe)3)2,6
cis-PtBr2(P(OMe)2Ph)2,7
cis-PtBr2-
7
8
(P(OMe)Ph2)2 and cis-PtBr2(PPh3)2 were prepared in good
yield from trans-PtBr2(PhCN)2 and two equivalents of the
phosphite, phosphonite, phosphinite or phosphine in acetone.
6
cis-PtI2(P(OMe)3)2 was prepared in good yield from trans-
PtI2(PhCN)2 and two equivalents of trimethyl phosphite in
acetone. cis-PI2(PPh3)2 was prepared by metathesis of cis-
PtCl2(PPh3)2 with excess sodium iodide in an equivolume mixture
of water, ethanol, acetone and chloroform. All compounds
were characterised using NMR. Crystals suitable for X-ray
C, 35.52 (35.42); H, 2.66 (2.97).1H NMR (CDCl3, 291 K): d(ppm)
=
3.31 (d, 6H, methyl, 3JPH = 12.4 Hz), d(ppm) = 7.36–7.79 (m, 20H,
8
1
phenyl). 31P{ H} NMR (C6D6, 295 K): d(ppm) = 83.5 (1J P–Pt = 3995
Hz). Infra red: nPt–I 175, 167 cm-1, nPt–P 218, 206 cm-1, nP–O–alkyl
1032 cm-1, nP–Ph 1436 cm-1.
Crystallography
School of Chemistry, University of St Andrews, St Andrews, Scotland KY16
9ST. E-mail: jdw3@st-and.ac.uk
Crystal structure data (Tables 2–4) were collected for all complexes
at 125 K using a Rigaku SCX-Mini, (Mo radiation). All data was
† CCDC reference numbers 766308–766315. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c003256e
8620 | Dalton Trans., 2010, 39, 8620–8625
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Table 1 31P NMR chemical shifts and 195Pt–31P coupling constants for
(1)–(12)
to decrease in the order Cl > Br > I with the exception of the
complexes containing P(OMe)3 where the opposite is observed.
The X-ray crystal structures of the dibromide complexes (5)–(8)
(Fig. 2, Table 2) were determined and refined to a good standard.
All of the structures exhibit square planar geometry about the
platinum and were observed to be isostructural to their dichloride
Compound
dppm
JP–Pt/Hz
(1) cis-PtCl2(P(OMe)3)2
(2) cis-PtCl2(P(OMe)2Ph)2
(3) cis-PtCl2(P(OMe)Ph2)2
(4) cis-PtCl2(PPh3)2
(5) cis-PtBr2(P(OMe)3)2
(6) cis-PtBr2(P(OMe)2Ph)2
(7) cis-PtBr2(P(OMe)Ph2)2
(8) cis-PtBr2(PPh3)2
(9) cis-PtI2(P(OMe)3)2
(10) cis-PtI2(P(OMe)2Ph)2
(11) cis-PtI2(P(OMe)Ph2)2
(12) cis-PtI2(PPh3)2
73.7
97.2
85.2
14.5
75.2
97.0
84.9
14.0
77.6
96.4
83.5
11.6
5707
4819
4183
3679
5662
4777
4141
3627
5477
4618
3995
3472
˚
analogues. The Pt–Br distances lie within the range 2.4696(4) A
˚
to 2.4933(5) A and exhibit no significant trend. The Pt–P bond
˚
˚
lengths are within the range 2.207(2) A to 2.2685(10) A and, as
was observed in the dichloride analogues, increase in the order
P(OMe)3 < P(OMe)2Ph < P(OMe)Ph2 < PPh3. The P(1)–Pt–
P(2) and Br(1)–Pt–Br(2) bond angles lie in the ranges 93.74(9)◦to
98.41(4)◦ and 86.000(18)◦ to 89.265(17)◦ respectively with no
significant trends apparent.
corrected for absorption. The structures were solved by direct
methods and refined by full-matrix least-squares methods on F2
values of all data.9 Refinements were performed using SHELXL.10
Results and discussion
The crystal structures and 31P NMR for the dichloride com-
plexes have been previously reported [(1) cis-PtCl2(P(OMe)3)2,5
12
(2) cis-PtCl2(P(OMe)2Ph)2,11 (3) cis-PtCl2(P(OMe)Ph2)2 and
(4) cis-PtCl2(PPh3)2].13 The dibromide and diiodide analogues
[(5) cis-PtBr2(P(OMe)3)2, (6) cis-PtBr2(P(OMe)2Ph)2, (7) cis-
PtBr2(P(OMe)Ph2)2, (8) cis-PtBr2(PPh3)2, (9) cis-PtI2(P(OMe)3)2,
(10) cis-PtI2(P(OMe)2Ph)2, (11) cis-PtI2(P(OMe)Ph2)2 and (12) cis-
PtI2(PPh3)2] were characterised in this work.
1
The 31P–{ H} NMR spectra of all the complexes (Table 1)
1
exhibit singlets together with satellites due to JPt–P couplings.
For each of the three halides the coupling constant is observed
to decrease in the order P(OMe)3 > P(OMe)2Ph > P(OMe)Ph2 >
PPh3 (Fig. 1) as the p-acidity of the phosphorus ligands decrease.
In addition to this, for each of the four phosphorus ligands the
coupling constant decreases in the order Cl > Br > I as the degree
of p back-bonding between the platinum and the halide, and hence
the halide’s ability to compete with the phosphorus for the electron
back-donation, increases. This can be interpreted as an increase in
trans-influence as the coupling constant is an indication of bond
strength and trans-influence is defined as the ability of a ligand to
weaken the bond trans to it.14 The chemical shifts are also seen
Fig. 2 X-ray crystal structure of (7). The structures of (5), (6) and (8) are
not illustrated as they are similar.
The X-ray crystal structures of the diiodide complexes (9)–
(12) (Fig. 3, Table 2) were also determined and observed to be
isostructural though not necessarily isomorphous to the dibro-
mide structures. Similar trends in bond lengths and angles as those
observed for the dibromides are also evident. Most significantly
Fig.
1
Variation of 195Pt–31P coupling constants with phos-
Fig. 3 X-ray crystal structure of (10). The structures of (9), (11) and (12),
phite/phosphine character.
are not illustrated as they are similar.
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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for (1)–(12)
5
11
12
13
(1) PtCl2(P(OMe)3)2
(2) PtCl2(P(OMe)2Ph)2
(3) PtCl2(P(OMe)Ph2)2
(4) PtCl2(PPh3)2
Pt–Cl(1)
Pt–Cl(2)
Pt–P(1)
Pt–P(2)
P(1)–Pt–P(2)
Cl(1)–Pt–Cl(2)
2.384(4)
2.408(4)
2.192(3)
2.155(3)
95.5(1)
2.3625(9)
2.3625(9)
2.2193(9)
2.2193(9)
101.16(3)
89.08(3)
2.3693(12)
2.3533(12)
2.2272(11)
2.2279(12)
98.14(4)
2.3632(8)
2.3294(9)
2.2713(9)
2.2515(8)
99.12(3)
87.56(3)
85.8(1)
89.37(4)
(5) PtBr2(P(OMe)3)2
(6) PtBr2(P(OMe)2Ph)2
(7) PtBr2(P(OMe)Ph2)2
(8) PtBr2(PPh3)2
Pt–Br(1)
Pt–Br(2)
Pt–P(1)
Pt–P(2)
P(1)–Pt–P(2)
Br(1)–Pt–Br(2)
2.4742(11)
2.4753(11)
2.217(2)
2.207(2)
93.74(9)
88.54(3)
2.4933(5)
2.4762(4)
2.2161(9)
2.2248(12)
93.76(4)
2.4895(4)
2.4828(5)
2.2400(11)
2.2424(11)
98.41(4)
2.4696(4)
2.4859(5)
2.2625(13)
2.2685(10)
97.55(4)
89.209(16)
89.265(17)
86.000(18)
(9) PtI2(P(OMe)3)2
(10) PtI2(P(OMe)2Ph)2
(11) PtI2(P(OMe)Ph2)2
(12) PtI2(PPh3)2
Pt–I(1)
Pt–I(2)
Pt–P(1)
Pt–P(2)
P(1)–Pt–P(2)
I(1)–Pt–I(2)
2.6587(4)
2.6571(4)
2.2214(14)
2.2248(16)
94.56(5)
2.6608(5)
2.6569(4)
2.2360(14)
2.244(2)
93.84(6)
88.836(17)
2.6814(5)
2.6533(5)
2.2481(19)
2.2518(19)
93.01(7)
2.6647(6)
2.6448(5)
2.295(2)
2.277(2)
97.47(7)
87.456(18)
88.979(13)
88.003(17)
Table 3 Experimental and refinement details for the X-ray structures for (5)–(8)
Compound
(5)
(6)
(7)
(8)·CHCl3
Fw
M
C6H18O6P2Br2Pt
603.05
C16H22O4P2Br2Pt
695.19
C26H26O2P2Br2Pt
787.34
C37H31P2Cl3Br2Pt
998.86
T/K
125
125
Triclinic
¯
P1
125
Monoclinic
P 21/n
125
Triclinic
¯
P1
Crystal System
Space group
Orthorhombic
Pna21
12.6116(9)
7.6773(6)
16.0931(12)
90
90
90
1558.2(2)
4
14.328
˚
a/A
9.1545(7)
9.9510(8)
13.1489(10)
110.452(8)
94.763(7)
108.745(8)
1036.72(14)
2
10.778
2.227
3629
3641
12.675(3)
13.753(5)
14.938(10)
90
93.283(9)
90
2599.6(20)
4
8.604
11.1265(7)
11.7130(7)
14.2633(10)
90.826(6)
98.341(7)
106.986(8)
1755.81(20)
2
6.608
1.889
15229
6155
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
U/A
Z
m(Mo-Ka)mm-1
Dc/Mg m-3
2.570
12415
2730
2.012
22176
4568
Total reflections
Independent
Reflections (Rint
)
(0.085)
0.4333, 0.2386
0.0335, 0.0664
1.36
(0.026)
(0.050)
0.2776, 0.2071
0.0265, 0.0624
1.16
(0.036)
Max and min. transmission
Final R,R¢
0.3575, 0.1904
0.0203, 0.0449
0.49
0.5297, 0.2587
0.0353, 0.0842
1.00
Largest difference
-3
˚
peak, hole/e.A
-0.92
-0.69
-0.99
-0.88
˚
˚
than the P(OMe)3 complexes (Table 2, Fig. 4). For each of the
phosphorus ligands the Pt–P bond length increases in the order
Cl < Br < I with Pt–P bond lengths in the iodide complexes
the Pt–P bond lengths (2.2214(14) A to 2.295(2) A) increase in
the order P(OMe)3 < P(OMe)2Ph < P(OMe)Ph2 < PPh3. The
˚
˚
Pt–I distances are in the range 2.6448(5) A to 2.6814(5) A and
the P(1)–Pt–(P2) and Br(1)–Pt–Br(2) bond angles lie in the ranges
88.979(13)◦ to 97.47(7)◦ and 87.456(18)◦ to 94.56(5)◦ respectively
with the latter decreasing in the order P(OMe)3 > P(OMe)2Ph >
P(OMe)Ph2 > PPh3.
Comparing the structures of compounds (1)–(12) it can be seen
that for each of the halides the Pt–P bond length is seen to increase
in the order P(OMe)3 < P(OMe)2Ph < P(OMe)Ph2 < PPh3 with
˚
being ca. 0.03 A longer than their dichloride equivalents. These
two effects are in accord with [1] the p-acidity of the phosphorus
ligands increasing as the oxygen content rises and [2] the heavier
halogens being better p-acceptors and thus phosphorus trans to
iodine is less strongly bound than phosphorus trans to chloride.
When considering the magnitude of the {Pt–P} coupling
constant the s-character of the orbitals involved in the Pt–P bond
is usually considered to be the most important variable.
˚
the PPh3 complexes having Pt–P bond lengths ca. 0.06 A longer
8622 | Dalton Trans., 2010, 39, 8620–8625
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Table 4 Experimental and refinement details for the X-ray structures for (9)–(12)
Compound
(9)
(10)
(11)
(12)·H2O
Fw
M
C6H18O6P2I2Pt
697.05
C16H22O4P2I2Pt
789.19
C26H26O2P2I2Pt
881.34
C36H32OP2I2Pt
991.49
T/K
125
Monoclinic
P21/n
125
Triclinic
¯
P1
125
Monoclinic
Cc
125
Triclinic
¯
P1
Crystal System
Space group
˚
a/A
9.0554(4)
14.7571(7)
12.8733(9)
90
98.251(7)
90
1702.46(16)
4
12.035
9.496(3)
10.044(3)
13.743(4)
66.910(15)
71.546(18)
71.621(15)
1116.0(6)
2
9.189
2.348
9745
3922
10.456(4)
17.143(7)
15.597(6)
90
104.500(3)
90
2706.7(19)
4
7.585
9.8227(5)
10.4994(6)
17.7427(13)
86.757(6)
77.704(6)
70.376(5)
1683.78(17)
2
6.107
1.955
14529
5893
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
3
˚
U/A
Z
m(Mo-Ka)mm-1
Dc/Mg m-3
2.719
14469
2993
2.163
11522
4748
Total reflections
Independent
Reflections (Rint
)
(0.051)
0.5837, 0.2200
0.0276, 0.0472
0.76
(0.035)
(0.035)
0.7023, 0.4157
0.0267, 0.0467
0.94
(0.046)
Max and min. transmission
Final R,R¢
0.2602, 0.2062
0.0287, 0.0625
1.25
0.6088, 0.4408
0.0403, 0.0922
2.02
Largest difference
-3
˚
peak, hole/e.A
-0.93
-1.66
-1.00
-1.15
We found that as the bond length increases the coupling con-
stant decreases. The correlation between these two measurements
in this series of compounds is rather good giving a reasonable
straight line that can be fitted by eqn (2) (Fig. 5). We did consider
that another way of gauging the s-character and hence the strength
of the bond would be to look at the R–P–R, R–P–O and O–P–
O bond angles in these complexes with larger values indicating a
move towards more ideal sp3 hybridisation however we did not
observe any correlation in this regard.. It thus appears that in a
narrow series of complexes the coupling constant could be used as
a good indicator of bond length.
J
(2)
l(Pt−P) = 2.421−
24255
Fig. 4 Variation of Pt–P in PtX2(P(OMe)nPh3-n)2 complexes.
SM (0) 2
DE
64p2
9
1J(M−P) = g Mg P
b2
SP (0) 2 (P'SM
)
S
P
2
(1)
Thus, to a good approximation, the coupling constant is given
by eqn (1)3 where the s-characters of the orbitals is contained
in the M.O. bond order between the s-orbitals, (P¢S P )2. The
S
M
valance state s-orbital basis functions are given by the expressions
|SP(0)| and |SM (0)| , DE is the average excitation energy and
g M and g P the magnetogyric constants for each nucleus. As is
evident the principles involved are complex however for a given
Fig.
5
Correlation of 1JPt–P with Pt–P bond length in
PtX2(P(OMe)nPh3–n)2 complexes.
phosphorus ligand and metal centre |SP(0)| and |SM(0)| should
2
remain relatively constant leaving (P¢SM
)
as the dominating
To further test the principle we compared Pt–P bond lengths and
1JPt–P coupling constants we examined Pt(E2N2)(PR3)2
as their protonated equivalents that have been prepared in our
and other labs,18,20–25 corresponding cis- and trans-dihalides26–48
S
P
1
15–21
factor in the magnitude of JPt–P. Clearly given eqn (1), provided
the nature of the bonding is not dramatically different there should
be a good correlation between Pt–P bond length and J{Pt–P}.
as well
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Table 5 Pt–P distances and Coupling constants used in Fig. 6
1JPt–P/Hz
˚
Compound (trans-atom in bold)
Pt–P Bond Length/A
15
Pt(S2N2)(P(OPh)3)2
2.221(3)
2.234(3)
2.217(3)
2.246(3)
2.239(2)
2.237(2)
2.2175(15)
2.2407(15)
2.250(2)
2.256(2)
2.263(4)16
2.317(4)
2.265(3)18
2.271(4)
2.243(2)19
2.281(2)
2.261(6)17
2.268(5)
2.262(2)18
2.305(2)
2.249(1)23
2.263(1)
2.270(3)24
2.320(3)
2.2675(2)
2.3145(2)
2.243(2)
2.214(2)
2.2480(14)
2.2266(13)
2.260(3)
2.253(4)
2.3069(17)
2.2664(12)
2.271(2)20
2.261(2)
2.262(2)20
2.301(2)
2.257(3)
2.313(3)
2.2235
4634
4503
4502
4395
4498
4415
3864
3761
Pt(S2N2)(P(OPh)3)2
15
Pt(S2N2)(P(OMe)3)2
Pt(S2N2)(P(OMe)3)2
15
Pt(S2N2)(P(OEt)3)2
Pt(S2N2)(P(OEt)3)2
15
Pt(S2N2)(P(OMe)2Ph)2
Pt(S2N2)(P(OMe)2Ph)2
15
Pt(S2N2)(P(OMe)Ph2)2
3287
Pt(S2N2)(P(OMe)Ph2)2
Pt(S2N2)(PPh3)2
3249
299417
2827
Pt(S2N2)(PPh3)2
Pt(S2N2)(PMe2Ph)2
279917
2731
Pt(S2N2)(PMe2Ph)2
Pt(S2N2)(PMePh2)2
288617
2781
1
Fig. 6 Correlation of JPt–P with Pt–P bond length in large range of
Pt–Phosphorus complexes. Black line is best fit to the points in the graph
eqn (3). Red line is the line from eqn (2).
Pt(S2N2)(PMePh2)2
Pt(S2N2)(PMe3)2
Pt(S2N2)(PMe3)2
274817
2681
[Pt(S2N2H)(PMe2Ph)2]PF6
[Pt(S2N2H)(PMe2Ph)2]PF6
[Pt(S2N2H)(PMe3)2]PF6
[Pt(S2N2H)(PMe3)2]PF6
[Pt(S2N2H)(PEt3)2]PF6
[Pt(S2N2H)(PEt3)2]PF6
[Pt(S2N2H)(PnBu3)2]2[PF6]Cl22
[Pt(S2N2H)(PnBu3)2]2[PF6]Cl
324022
2595
313022
2566
Table 6 Coupling constants and calculated (using eqn (2) or (3)) and
observed bond lengths for selected compounds
316222
2563
Compound
1JPt–P/Hz lPt–P/A
Eqn 2 (A) Eqn 3 (A)
˚
˚
˚
3164
2561
4530
4571
3868
3900
3309
3391
15
51
Pt(SeSN2)(P(OMe)3)2
[Pt(9S3)(PPh3)Cl]PF6
3387
3438
2969
3145
2881
2.2838(8) 2.281 2.266
51
Pt(SeSN2)(P(OMe)3)2
[Pt(10S3)(PPh3)Cl]PF6
[Pt(PMe3)2{CS3}]52
[Pt(PPh3)2{CS3}]52
[Pt(dppp)2{CS3}]52
2.285(2) 2.279
2.264
2.285
2.278
2.289
2.208
15
Pt(SeSN2)(P(OMe)2Ph)2
2.265
2.2915
2.263
2.231
2.298
2.29
2.302
2.227
Pt(SeSN2)(P(OMe)2Ph)2
15
Pt(SeSN2)(P(OMe)Ph2)2
[Pt(Se2naph)(P(OPh)3)2]53 4711
Pt(SeSN2)(P(OMe)Ph2)2
15
Pt(SeSN2)(PPh3)2
2996
Pt(SeSN2)(PPh3)2
2948
Pt(SeSN2)(PMe2Ph)2
Pt(SeSN2)(PMe2Ph)2
[Pt(SeSN2H)(PMe2Ph)2]BF4
[Pt(SeSN2H)(PMe2Ph)2] BF4
[Pt(TeSN2H)(PMe2Ph)2] BF4
279921
2837
is not necessarily linear since at the extremes significant energetic
stabilisation is needed in order to influence bond length and the
magnitude of coupling constants is a better measure of s orbital
overlap than of absolute bond length, however the best fit straight
line is given by eqn (3).
268721
3227
25
2645
3171
5697
5812
5793
5707
4819
4183
[Pt(TeSN2H)(PMe2Ph)2] BF4
cis-PtCl2(P(OEt)3)2
26
cis-PtCl2(P(OiPr)3)2
2.21465
2.1991527
2.17355
J
cis-PtCl2(P(OPh)3)2
cis-PtCl2(P(OMe)3)2
cis-PtCl2(P(OMe)2Ph)2
cis-PtCl2(P(OMe)Ph2)2
(3)
l(Pt−P) = 2.422−
21827
11
2.2190
12
2.22755
2.261413
2.23828
Using eqn (2) and (3) we tested the accuracy of the correlation as
an indicator of bond length on a selection of compounds (Table 6).
It is interesting to note that in most cases eqn (2) tends to give a
more accurate result than eqn (3) the former being on average
cis-PtCl2(PPh3)2
3679
cis-PtCl2(PMe3)2
cis-PtCl2(PMe2Ph)2
cis-PtCl2(PMePh2)2
cis-PtCl2(PEt3)2
348929
354931
361631
352031
353031
364031
3610
2.24430
2.2487532
2.26333
˚
within 0.015 A of the observed distance and the latter within
cis-PtCl2(PEt2Ph)2
cis-PtCl2(PEtPh2)2
2.2529534
2.2574535
2.208
˚
0.02 A. The accuracy of eqn (3) could potentially be improved
36
with a more extensive literature search.
cis-PtCl2(dppe)2
36
cis-PtCl2(dppp)2
2.232
3408
cis-PtBr2(P(OPh)3)2
cis-PtI2(PMe3)2
2.20537
572838
331729
336641
240031
241744
263046
249646
223629
302750
3190
2.257539
2.241840
2.29842
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