Phosphine exchange reactions involving cis-[Pt(PPh3)2(Bcat)2] (cat = 1,2-O2C6H4) and the oxidative addition of 1,2-B2Cl2(NMe2)2 to Pt0

Article abstract of DOI:10.1039/a810006c

The reaction between the platinum(II) bis(boryl) complex cis-[Pt(PPh₃)₂(Bcat)₂] (cat = 1,2-O₂C₆H₄) and the tertiary phosphines PMe₃, PEt₃, PMe₂Ph, PMePh₂ and dcpe [1,2-bis(dicyclohexylphosphino)ethane] and the phosphite P(OEt)₃ afforded the new complexes cis-[Pt(PR₃)₂(Bcat)₂] (PR₃ = PMe₃, PEt₃, PMe₂Ph or PMePh₂), cis-[Pt(dcpe)-(Bcat)₂] and cis-[Pt{P(OEt)₃}₂(Bcat)₂]. With PCy₃ the mixed phosphine species cis-[Pt(PCy₃)(PPh₃)(Bcat)₂] is the major product and was characterised by X-ray crystallography. With P(OMe)₃ reductive elimination of B₂(cat)₂ and the formation of platinum(0) products occurs exclusively whereas with dmpe [1,2-bis(dimethylphosphino)ethane] the only identifiable product is the platinum(ii) species [Pt(dmpe)₂]Cl₂. With dppm [bis(diphenylphosphino)methane] a reaction occurs to give a product assigned the structure cis-[Pt(dppm)(Bcat)₂] or [Pt₂(dppm)₂(Bcat)₄] but two binuclear products were isolated as minor products, namely [Pt₂(PPh₃)(μ-dppm)₂(Bcat)(μ-Bcat)] and [Pt₂(κ¹-dppm)-(μ-dppm) ₂(Bcat)(μ-Bcat)]. Both compounds were characterised by X-ray crystallography and shown to contain unusual semi-bridging Bcat groups. The reaction between [Pt(PPh₃)₂(η-C₂H₄)] and the diborane(4) compound 1,2-B₂Cl₂(NMe₂)₂ is also described which results in B-B bond oxidative addition yielding cis-[Pt(PPh₃)₂{BCl(NMe₂)}₂] and a complex to which this bis(boryl) subsequently rearranges, namely trans-[PtCl(PPh₃)₂{BCl(NMe₂)}]. Both of these complexes were characterised by X-ray crystallography and have geometries typical of cis-bis(boryl) and trans-boryl chloride complexes respectively.

Full text of DOI:10.1039/a810006c

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Phosphine exchange reactions involving cis-[Pt(PPh3)2(Bcat)2]
(cat ؍ 1,2-O2C6H4) and the oxidative addition of 1,2-B2Cl2(NMe2)2
to Pt0
David Curtis, M. J. Gerald Lesley, Nicholas C. Norman,* A. Guy Orpen* and
Jonathan Starbuck
The University of Bristol, School of Chemistry, Bristol, UK BS8 1TS.
E-mail: N.C.Norman@Bristol.ac.uk
Received 24th December 1998, Accepted 16th March 1999
The reaction between the platinum() bis(boryl) complex cis-[Pt(PPh3)2(Bcat)2] (cat = 1,2-O2C6H4) and the tertiary
phosphines PMe3, PEt3, PMe2Ph, PMePh2 and dcpe [1,2-bis(dicyclohexylphosphino)ethane] and the phosphite
P(OEt)3 afforded the new complexes cis-[Pt(PR3)2(Bcat)2] (PR3 = PMe3, PEt3, PMe2Ph or PMePh2), cis-[Pt(dcpe)-
(Bcat)2] and cis-[Pt{P(OEt)3}2(Bcat)2]. With PCy3 the mixed phosphine species cis-[Pt(PCy3)(PPh3)(Bcat)2] is the
major product and was characterised by X-ray crystallography. With P(OMe)3 reductive elimination of B2(cat)2 and
the formation of platinum(0) products occurs exclusively whereas with dmpe [1,2-bis(dimethylphosphino)ethane]
the only identifiable product is the platinum() species [Pt(dmpe)2]Cl2. With dppm [bis(diphenylphosphino)methane]
a reaction occurs to give a product assigned the structure cis-[Pt(dppm)(Bcat)2] or [Pt2(dppm)2(Bcat)4] but two
binuclear products were isolated as minor products, namely [Pt2(PPh3)(µ-dppm)2(Bcat)(µ-Bcat)] and [Pt2(κ1-dppm)-
(µ-dppm)2(Bcat)(µ-Bcat)]. Both compounds were characterised by X-ray crystallography and shown to contain
unusual semi-bridging Bcat groups. The reaction between [Pt(PPh3)2(η-C2H4)] and the diborane(4) compound 1,2-
B2Cl2(NMe2)2 is also described which results in B–B bond oxidative addition yielding cis-[Pt(PPh3)2{BCl(NMe2)}2]
and a complex to which this bis(boryl) subsequently rearranges, namely trans-[PtCl(PPh3)2{BCl(NMe2)}]. Both
of these complexes were characterised by X-ray crystallography and have geometries typical of cis-bis(boryl) and
trans-boryl chloride complexes respectively.
The platinum catalysed addition of diborane(4) compounds to
the C–C/C–O multiple bonds present in alkenes,1 alkynes,2 1,3-
dienes,3 α,β-unsaturated ketones4 and allenes5 (diboration) is
now well established. Key intermediates in these reactions are
platinum() bis(boryl) complexes formed by oxidative addition
of the B–B bond of the diborane(4) compound to a platinum(0)
centre1–6 and many examples of complexes with the general
formula cis-[Pt(PR3)2(BRЈ2)2] have now been isolated and
structurally characterised.2b,c,e,3b,7–9 As part of a study of the
chemistry of platinum() bis(boryl) complexes, with the
ultimate aims of developing better diboration catalysts, gaining
further insight into the mechanism of diboration catalysis and
probing further the nature of the Pt–B bond, we have carried
out exploratory studies involving phosphine exchange reactions
with the complex cis-[Pt(PPh3)2(Bcat)2] 1 (cat = 1,2-O2C6H4).
This study builds on preliminary work which established
that no dissociation of PPh3 occurs at room temperature in
solution (at least on the timescale associated with 31P NMR
spectroscopy) although the chelating diphosphines dppe [1,2-
bis(diphenylphosphino)ethane] and dppb [1,2-bis(diphenyl-
phosphino)butane] did substitute both PPh3 ligands yielding
the complexes [Pt(dppe)(Bcat)2] 2 and [Pt(dppb)(Bcat)2] 3.2e
We also describe herein the reaction of the diborane(4) com-
pound 1,2-B2Cl2(NMe2)2, which has recently been shown to
undergo reactions giving rise to metal complexes containing
diboran(4)yl [–B(NMe2)BCl(NMe2)]10 and borylene [B(NMe2)]
ligands,11 with [Pt(PPh3)2(η-C2H4)].
with 1 equivalent of either dppe or dppb affording 2 and 3
respectively in essentially quantitative yield. Compound 1
reacts similarly with 1 equivalent of dcpe [1,2-bis(dicyclo-
hexylphosphino)ethane] in toluene affording 4, NMR data for
which are presented in Table 1 (data for compounds 1–3 are
also given for comparison). In all cases, the 31P-{1H} resonances
are broad, due to the presence of the quadrupolar boron
nucleus trans to phosphorus, whilst the small |1JPt–P| values are
as expected for cis co-ordination about platinum() but also
reflect the large trans influence of the boryl group.9c The
11B-{1H} resonances occur in the region δ 47–55 consistent with
other platinum boryl compounds.9c
Ph3P
Ph3P
Bcat
Bcat
P
Bcat
Pt
Pt
P
Bcat
1
2 PP = dppe; 3 PP = dppb; 4 PP = dcpe
In contrast to the reactions of compound 1 with dppe, dppb
and dcpe, that in toluene with 1 equivalent of the more basic
diphosphine dmpe [1,2-bis(dimethylphosphino)ethane] was
more complicated. After precipitation of all products from
toluene by addition of hexane (only PPh3 remained in solution)
and redissolving in CD2Cl2, analysis by 31P-{1H} NMR
spectroscopy revealed, in addition to traces of unchanged 1,
three resonances with approximately equal intensities each with
1
platinum satellites, one of which (δP 26.5; JPt–P = 2397 Hz) is
For a report dealing with related phosphine substitution
reactions involving the rhodium complex [RhCl(PPh3)2(Bcat)2]
see ref. 12.
attributed to the ionic platinum() compound [Pt(dmpe)2]Cl2
1
by comparison with data given in ref. 14 (δP 29.0; JPt–P = 2352
Hz). We propose that the chloride counter ion derives from the
NMR solvent since we observed that [Pt(dmpe)2]Cl2 was
formed as the sole product when an excess of dmpe was
added to a solution of [Pt(PPh3)2(η-C2H4)] in CD2Cl2 at room
Results and discussion
As stated above and described in ref. 2(e), compound 1 reacts
J. Chem. Soc., Dalton Trans., 1999, 1687–1694
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Table 1 The 31P-{1H} and 11B-{1H} NMR data for [Pt(P)2(Bcat)2] compoundsa
Compound
θ/Њ (νb/cmϪ1
)
Solvent
δP (1JPt–P/Hz)
δB
1 cis-[Pt(PPh3)2(Bcat)2]
145 (2068.9)
125
CDCl3
28.7 (1616)
57.8 (1454)
21.6 (1589)
78.1 (1404)
17.3 (1522)
Ϫ17.2 (1398)
18.0 (1564)
Ϫ5.5 (1537)
9.2 (1594)
149.9 (2824)
36.6 (1713); 23.7 (1564)
30.4 (1434)
47.0
48.9
48.9
54.5
47.5
47.9
49.6
48.4
47.0
48.0
48.8
50.8
36.4
2 cis-[Pt(dppe)(Bcat)2]c
C6D6–thf
C6D6–thf
CH3C6H5
CD2Cl2
CD2Cl2
C6D6
3 cis-[Pt(dppb)(Bcat)2]c
4 cis-[Pt(dcpe)(Bcat)2]
142
121
5 cis,cis-[Pt2(µ-dppm)2(Bcat)4]d,e
8 cis-[Pt(PMe3)2(Bcat)2]
118 (2064.1)
132 (2061.7)
122 (2065.3)
136 (2067.0)
108 (2077.0)
170 (2056.4)
9 cis-[Pt(PEt3)2(Bcat)2]
10 cis-[Pt(PMe2Ph)2(Bcat)2]e,f,g
11 cis-[Pt(PMePh2)2(Bcat)2]d
12 cis-[Pt{P(OEt)3}2(Bcat)2]e,g
13 cis-[Pt(PCy3)(PPh3)(Bcat)2]
14 cis-[Pt(PPh3)2{BCl(NMe2)}2]
15 trans-[PtCl(PPh3)2{BCl(NMe2)}
C6D6
CD2Cl2
CD2Cl2
CD3C6D5
CD3C6D5
CD3C6D5
25.8 (3188)
a The δ (31P) values reported in ppm with positive shifts downfield relative to 85% H3PO4 at 161.3 (400), 121.5 (300) and 36.1 MHz (90), δ (11B) values
in ppm with positive shifts downfield relative to BF3ؒOEt2 at 128.4 (400), 96.3 (300) and 28.6 MHz (90). b Ligand (PR3) cone angle and electronic
parameter {ν = νCO(A1) of [Ni(CO)3L] in CH2Cl2} from ref. 13. c Ref. 2(e). d At Ϫ90 ЊC. e Contained unchanged compound 1. f At Ϫ55 ЊC. g Con-
tained decomposition products.
temperature, although the presence of traces of DCl cannot
be ruled out as a source of chloride. The remaining 31P signals
1
1
(δP 22.3; JPt–P = 3837 Hz; δP 36.4; JPt–P = 2041 Hz) arise from
compounds which we have not been able to identify. The
11B-{1H} NMR spectrum, however, showed no signals consist-
ent with the presence of a platinum boryl complex although a
resonance corresponding to the diborane(4) compound B2(cat)2
was observed indicating the likely reductive elimination of the
boryl groups in 1. Signals due to the compounds B2(cat)3 and
[B(cat)2]Ϫ, which are often associated with the decomposition
of metal–Bcat complexes, were also observed however.2e,9c
The reaction of compound 1 in dichloromethane with
1.1 equivalent of dppm [bis(diphenylphosphino)methane]
resulted in an orange-red solution (compounds 1–4 are colour-
less or pale yellow) for which only an extremely broad
resonance at about δ Ϫ8 was seen in the 31P-{1H} spectrum. No
platinum satellites were observed but on cooling to Ϫ90ЊC the
spectrum resolved into two major resonances, each with
platinum satellites, one corresponding to unchanged 1 and the
other (δP 17.3; 1JPt–P = 1522 Hz) characteristic of a new platinum
cis-bis(boryl) complex 5 [in the presence of an excess of dppm
(2.6 equivalents) only 5 was observed]. Additional resonances
were also observed at Ϫ90Њ C arising from free PPh3 and dppm
together with signals due to traces of other unidentified prod-
ucts. One possible structure for 5 is equivalent to the known
structures of 2 and 3, i.e. cis-[Pt(dppm)(Bcat)2] 5a, although in
view of the known propensity of dppm to act as a bridging
ligand and the observed 31P chemical shift15 a binuclear
structure is more likely, i.e. cis,cis-[Pt2(µ-dppm)2(Bcat)4] 5b; the
Bcat groups would be expected to be cis as observed in
the mononuclear examples. The 11B-{1H} NMR spectrum of
the reaction mixture at room temperature contained a broad
resonance [δB 46.9 (C7D8); 47.5 (CD2Cl2)] also consistent with
the presence of a metal boryl species.9c
Fig. 1 A view of the molecular structure of compound 6 with key
atoms labelled. Ellipsoids are drawn at the 30% probability level and
hydrogen atoms have been omitted for clarity. The peculiar nature of
some of the ellipsoids is a consequence of disorder problems discussed
in the Experimental section.
Fig. 2 A view of the molecular structure of compound 7 with key
atoms labelled. Ellipsoids are drawn at the 30% probability level and
hydrogen atoms have been omitted for clarity.
P
P
Bcat
Bcat
Bcat
Bcat
P
P
P
P
Bcat
Bcat
Pt
Pt
Pt
ively; both crystallise as solvates (see Experimental section).
Selected bond lengths and angles are given in Table 2. Although
both structures are affected by disorder, the basic features of
their geometries are well established.
5a
5b
PP = dppm
However, crystallisation from the orange-red reaction solu-
tion did not afford crystals of compound 5 but rather yielded
small quantities of two new materials, one red and the other
orange which were both characterised by X-ray crystallography
and shown to be [Pt2(PPh3)(µ-dppm)2(Bcat)(µ-Bcat)] 6 (Fig. 1)
and [Pt2(κ1-dppm)(µ-dppm)2(Bcat)(µ-Bcat)] 7 (Fig. 2) respect-
The two structures are very similar and comprise a Pt2P5B2
core in which the diplatinum moiety [6, Pt(1)–Pt(2) 2.7719(13);
7, 2.7690(8) Å] is bridged by two dppm ligands. In 6, Pt(1) is
also bonded to a PPh3 group whereas in 7 this platinum is
linked to one phosphorus of a third dppm ligand, a κ1-binding
mode. The other platinum atom, Pt(2), in both structures
1688
J. Chem. Soc., Dalton Trans., 1999, 1687–1694

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0
(µ-H)(µ-dppm)2][PF6] (A frame, 30 eϪ, Pt–Pt),17 trans, trans-
Table 2 Selected bond lenghts (Å) and angles (Њ) for compounds 6
and 7
[Pt2(CN)4(µ-dppm)2] (32 eϪ, Pt–Pt),18 cis, cis-[Pt2Me4-
0
(µ-dppm)2] (32 eϪ, Pt–Pt)19 and [Pt2Me3(µ-dppm)2][PF6] [so-
0
called V frame, 32 eϪ, Pt–Pt 2.769(1) Å],20 the PtI2 compounds
1
6
7
[Pt2Cl2(µ-dppm)2] [30 eϪ, Pt–Pt 2.651(1) Å]21 and [Pt2H(κ1-
1
Pt(1)–Pt(2)
Pt(1)–B(1)
Pt(2)–B(1)
Pt(2)–B(2)
Pt(1)–P(2)
Pt(1)–P(4)
Pt(1)–P(5)
Pt(2)–P(1)
Pt(2)–P(3)
2.7719(13)
2.12(2)
2.49(2)
2.7690(8)
2.14(2)
2.51(2)
dppm)(µ-dppm)2][PF6] [30 eϪ, Pt–Pt 2.769(1) Å]22 and the Pt0
1
2
compound [Pt2(µ-dppm)3] (32 eϪ, Pt–Pt).23 With the exception
0
of the PtII compound [Pt2Me3(µ-dppm)2][PF6] which is
2.04(2)
2.06(2)
2
described as having a donor–acceptor Pt–Pt bond, only the PtI2
compounds have platinum–platinum (single) bonds. Of the two
PtI2 dimers mentioned above, the complex [Pt2H(κ1-dppm)-
(µ-dppm)2][PF6] bears most resemblance to 6 and 7 (HϪ and
BcatϪ are formally analogous) and structurally the Pt2-
(dppm)2(P) core is similar in all three structures. However, the
hydride compound has only 30 valence electrons and contains
no bridging ligand. In the other complex, [Pt2Cl2(µ-dppm)2], a
terminal chloride is present on each platinum trans to the Pt–Pt
bond. A structure similar to this, i.e. [Pt2(µ-dppm)2(Bcat)2], is
an interesting possibility for a product from the reaction
described here and might arise from reductive elimination of
B2(cat)2 from structure 5b described earlier. We propose, how-
ever, that in view of the known high trans influence of boryl
ligands9c and the similarly high trans influence of the Pt–Pt
bond,19 a structure such as [Pt2(µ-dppm)2(Bcat)2] is not favour-
able and that in order to avoid this mutually trans alignment of
Pt–B and Pt–Pt bonds one boryl group tips into a cis, and
ultimately semi-bridging, position thereby generating a vacant
co-ordination site at that platinum centre which is filled by a
phosphine ligand; PPh3 in 6 and dppm in 7. In principle, this
might also happen with the other boryl group thereby gener-
ating a 34 electron complex [Pt2(µ-dppm)2(P)2(Bcat)2] but it
is likely that there would be problems of steric conjestion
associated with this structure. At this stage, however, it would
be unwise to speculate further on precisely what is happening in
the reaction between 1 and dppm, but the isolation of
complexes containing a bridging boryl group is certainly
unusual. The only other example of which we are aware is the
rhodium complex [Rh2(µ-H)2H(dippe)2(µ-Bcat)] [dippe = 1,2-
bis(diisopropylphosphino)ethane], a 30 eϪ complex.24
2.309(5)
2.334(5)
2.297(5)
2.284(5)
2.302(5)
2.305(3)
2.304(3)
2.303(3)
2.281(3)
2.290(3)
B(2)–Pt(2)–Pt(1)
B(2)–Pt(2)–P(1)
B(2)–Pt(2)–P(3)
B(2)–Pt(2)–B(1)
P(1)–Pt(2)–P(3)
B(1)–Pt(2)–P(1)
B(1)–Pt(2)–P(3)
Pt(1)–B(1)–Pt(2)
Pt(2)–Pt(1)–B(1)
Pt(2)–Pt(1)–P(2)
Pt(2)–Pt(1)–P(4)
Pt(2)–Pt(1)–P(5)
B(1)–Pt(1)–P(2)
B(1)–Pt(1)–P(4)
B(1)–Pt(1)–P(5)
P(2)–Pt(1)–P(4)
P(2)–Pt(1)–P(5)
P(4)–Pt(1)–P(5)
175.2(6)
87.6(6)
88.5(6)
137.7(8)
171.5(2)
98.8(6)
175.5(4)
88.7(4)
88.8(4)
136.9(5)
172.43(12)
99.4(4)
87.2(4)
72.7(5)
131.5(4)
95.51(8)
120.18(12)
100.63(12)
96.6(4)
89.1(6)
73.5(7)
129.0(7)
83.32(14)
96.04(16)
103.1(2)
129.0(7)
97.5(7)
96.6(4)
89.8(4)
120.18(12)
114.66(12)
100.63(12)
91.4(6)
121.6(2)
103.1(2)
109.6(2)
carries a terminal Bcat group [6, Pt(2)–B(2) 2.04(2); 7, 2.06(2)
Å] whilst the second Bcat group bridges the two platinum
centres albeit quite asymmetrically [6, Pt(1)–B(1) 2.12(2), Pt(2)–
B(1) 2.49(2); 7, 2.14(2), 2.51(2) Å]. In terms of the Pt–B
distances, the values for the Pt(2)–B(2) and Pt(1)–B(1) bonds
are typical of platinum boryl bond lengths in a range of
platinum bis(boryls),9c the latter slightly longer, whereas the
Pt(2)–B(1) distance is considerably longer. This observation
together with the Pt–Pt bond distances is consistent with a
description of 6 and 7 as bis(dppm) bridged platinum() dimers
in which each platinum carries a terminal Bcat group. In
addition, one platinum, Pt(1), is attached to a third two-
electron donor ligand (PPh3 in 6 and a κ1-dppm in 7) which
results in the Bcat group on that platinum tilting towards the
second platinum centre such that a semi-bridging attachment
mode is adopted. As far as the geometries around each
platinum are concerned, Pt(2) is almost ideally square planar if
the long Pt(2)–B(1) bond is ignored [maximum atom deviations
from the mean plane are 0.0996 (6) and 0.0918 Å (7)] whereas
Pt(1) adopts an irregular five-co-ordinate geometry. The two
boron trigonal planes and the mean square plane around Pt(2)
are essentially orthogonal.
The reactions between compound 1 and two equivalents
of a number of monodentate phosphines and phosphites in
dichloromethane according to eqn. (1) were also studied. The
cis-[Pt(PPh3)2(Bcat)2] ϩ 2 PR3 →
1
cis-[Pt(PR3)2(Bcat)2] ϩ 2 PPh3 (1)
8, PR3 = PMe3;
9, PR3 = PEt3;
10, PR3 = PMe2Ph;
11, PR3 = PMePh2;
12, PR3 = P(OEt)3
compound cis-[Pt(PMe3)2(Bcat)2] 8 was formed cleanly when
two equivalents of PMe3 were added (Table 1) but with an
excess of PMe3 some reductive elimination of B2(cat)2 was
evident with concomitant formation of platinum(0) products.
At first sight this observed reductive elimination was surprising
since a more basic phosphine such as PMe3 should favour the
higher oxidation state, in this case PtII, in any reductive
elimination/oxidative addition equilibrium. However, a more
detailed analysis of the 31P and 11B NMR spectra revealed the
presence of the mono and bis adducts of B2(cat)2, namely
[B2(cat)2(PMe3)] and [B2(cat)2(PMe3)2] formed from the reaction
between an excess of PMe3 and B2(cat)2. Their formation was
confirmed in a separate experiment in which PMe3 was added
to a CHCl3 solution of B2(cat)2 and spectroscopic data for both
products are given in the Experimental section. Mono and bis
adducts of diborane(4) compounds with two-electron donor
P
P
L
Pt
Pt
P
Bcat
B
cat
P
6 PP = dppm, L = PPh3
7 PP = dppm, L = κ1-dppm
The formulas of compounds 6 and 7 are such that the total
valence electron count for the PtI2 unit is 32 and in this sense
they are rather unusual. Of the numerous known examples of
complexes containing the Pt2(dppm)2 core, representative
examples for comparison are the PtII compounds [Pt2Cl2-
2
(µ-CH2)(µ-dppm)2] (A frame, 32 eϪ, Pt–Pt; the character above
0
the Pt–Pt bond denotes the formal bond order),16 [Pt2Me2-
J. Chem. Soc., Dalton Trans., 1999, 1687–1694
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PMe3
O
O
O
O
O
O
O
B
B
B
B
O
PMe3
PMe3
ligands, including phosphines, have been observed previously as
described in ref. 25.†
The reaction between compound 1 and either PEt3, PMe2Ph
or PMePh2 in dichloromethane afforded the compounds cis-
[Pt(PEt3)2(Bcat)2] 9, cis-[Pt(PMe2Ph)2(Bcat)2] 10 and cis-[Pt-
(PMePh2)2(Bcat)2] 11 as the major products although small
quantities of some other platinum–phosphine species were also
evident. Thus with PMe2Ph small amounts of the mixed phos-
phine platinum(0) complex [Pt(PPh3)2(PMe2Ph)2] [which has
1
been previously reported:26 δP(CH3CN) 15.1, Ϫ38.3, JPt–P
=
1
3779, 3900 Hz, cf. δP 14.6, Ϫ39.8, JPt–P = 3774, 3802 Hz
from ref. 26] were observed. Decomposition products such as
[Pt(PPh3)2(PMe2Ph)2] are not unexpected in reactions such as
those described here, however, in view of the known sensitivity
of metal boryl compounds in solution; see for example ref. 12.
In the case of compound 11, 31P NMR spectroscopy showed a
characteristic broad signal with 195Pt satellites (Table 1) and a
similarly characteristic platinum boryl resonance was observed
in the 11B NMR spectrum. Only at Ϫ90 ЊC, however, was the
31P spectrum clearly resolved since at room temperature even
a trace excess of PMePh2 resulted in very broad signals due,
presumably, to phosphine exchange processes. Similar observ-
ations were made for some related rhodium complexes.12 With
less than two equivalents of PMePh2, the 31P spectrum showed
only 11 and unchanged 1 with no evidence for a mixed phos-
phine species.
Fig. 3 A view of the molecular structure of compound 13 with key
atoms labelled. Details as in Fig. 2.
Table 3 Selected bond lengths (Å) and angles (Њ) for compound 13
Pt(1)–B(1)
Pt(1)–B(2)
2.044(4)
2.050(4)
Pt(1)–P(1)
Pt(1)–P(2)
2.3824(11)
2.3456(10)
B(1)–Pt(1)–B(2)
B(1)–Pt(1)–P(1)
B(1)–Pt(1)–P(2)
73.3(2)
163.91(12)
90.13(12)
B(2)–Pt(1)–P(1)
B(2)–Pt(1)–P(2)
P(1)–Pt(1)–P(2)
90.84(12)
163.10(12)
105.84(4)
taining free PPh3 and 13. The structure of 13 was confirmed by
X-ray crystallography (Fig. 3) selected bond lengths and angles
for which are given in Table 3. The structure of 13 adopts the
expected square planar co-ordination geometry around the
platinum centre (maximum atom deviation from the PtP2B2
mean plane is 0.0614 Å) with the boryls in a cis configuration
and oriented approximately perpendicular to the platinum
square plane [B(1) 74.8Њ and B(2) 70.2Њ]. In most respects the
structure differs in no significant way from those of other
platinum() cis-bis(boryls),2b,c,e,3b,7–9 but there is still some
discussion in the literature as to the extent of any platinum to
boron π-back bonding9c and having an unsymmetrical species
such as 13 where each Bcat group is trans to a different
phosphine could therefore offer some structural data relevant
to this matter. The two Pt–B bond lengths, however, are
the same within experimental error [Pt(1)–B(1) 2.044(4), Pt(1)–
B(2) 2.050(4) Å] although the two Pt–P distances are slightly
different [Pt(1)–P(1) 2.3824(11), Pt(1)–P(2) 2.3456(10) Å]
with that to the PCy3 ligand being the longer. Thus, whatever
factors influence the Pt–P bond lengths, there is clearly no effect
on the trans Pt–B distances and therefore, by implication, the
extent of any Pt–B π bonding at least on the basis of bond
lengths.
As a conclusion to this section on phosphine substitution
reactions it is useful to look for any apparent trends. Clearly the
chelating diphosphines all readily substitute PPh3 in a manner
consistent with the chelate effect. The phosphines dppe, dppb
and dcpe all do this cleanly to afford new cis-bis(boryls),
whereas dmpe leads to extensive decomposition involving the
solvent, and dppm results in products which reflect the
propensity of this diphosphine to act as a bridging ligand. With
regard to the monodentate tertiary phosphine ligands, all of
those studied substitute both PPh3 ligands with the exception
of PCy3, the latter possibly due to steric effects. Small amounts
of decomposition products are evident in many cases compris-
ing platinum(0) species and boron compounds such as B2(cat)3
and [B(cat)2]Ϫ. Reductive elimination of B2(cat)2 does not seem
to be a major process consistent with the expectation that more
basic phosphines should favour the Pt() product. In the case
of the reaction with PMe3, however, the products of reductive
elimination are seen although this is most likely due to the fact
that the B2(cat)2 produced is removed from the system through
When the phosphite ligand P(OEt)3 was used the boryl
complex cis-[Pt{P(OEt)3}2(Bcat)2] 12 was produced as the
major product together with minor amounts of [Pt{P(OEt)3}4]
(δP 128.6, 1JPt–P = 5386 Hz)27 and some unchanged 1. The use of
P(OMe)3, however, resulted exclusively in the rapid formation
1
of [Pt{P(OMe)3}4] (δP 133.4, JPt–P = 5403 Hz) with no new
platinum() bis(boryl) complex evident; B2(cat)2 was observed
in the 11B-{1H} NMR spectrum.
In the reaction between compound 1 and two equivalents of
PCy3 in toluene the mixed phosphine compound cis-
[Pt(PCy3)(PPh3)(Bcat)2] 13 was produced [eqn. (2)] as evidenced
[Pt(PPh3)2(Bcat)2] ϩ 2 PCy3 →
1
[Pt(PCy3)(PPh3)(Bcat)2] ϩ PPh3 ϩ PCy3 (2)
13
by the presence of two broad resonances in the 31P-{1H} NMR
spectrum each with platinum satellites (δP 36.6, 23.7,
1JPt–P = 1713, 1564 Hz). Additional resonances (δP 9.2 and Ϫ5.8)
indicated that both PCy3 and PPh3 were also present as
“unbound” ligands consistent with the formula of 13 and the
reaction stoichiometry. The chemically inequivalent boryl lig-
ands were not resolved by 11B-{1H} NMR which displayed only
a single broad resonance at δB 48.8. Even in the presence of
excess of PCy3 no evidence of a bis-PCy3 boryl complex was
observed.
Slow diffusion of hexane into a toluene solution of com-
pound 13 resulted in a colourless crystalline precipitate con-
† Diborane(4) compounds with diolate groups have previously only
been observed to form adducts with nitrogen bases such as amines and
pyridines whereas the more Lewis acidic dithiolate derivatives form
adducts with phosphine ligands as well.25b The PMe3 adducts of B2(cat)2
are therefore the first reported adducts of a diolate diborane(4) com-
pound with a phosphine. We should note, however, that in ref. 25(a),
it was mentioned in a concluding sentence that B2(cat)2 showed no
evidence for adduct formation with PMe3, an assertion which is now
clearly seen to have been in error.
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J. Chem. Soc., Dalton Trans., 1999, 1687–1694

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formation of adducts with PMe3; the other phosphines studied
here do not form adducts with this diborane(4) compound.
In the case of the two phosphites studied, their enhanced
π-acceptor capabilities should serve to stabilise the homoleptic
platinum(0) complexes observed thereby accounting for the
observed facile elimination of B2(cat)2 particularly in the case
of P(OMe)3.
As mentioned above in the discussion of Pt–B π bonding in
compound 13, this feature of the bonding in metal boryls
remains unresolved and one which this study was, in part,
designed to address. Most of the platinum boryls sructurally
characterised to date have involved either diolate or dithiolate
groups bonded to the boron,2b,c,e,3b,7,9 although the BF2 complex
described in ref. 8 is an exception. In order to extend the range
of boryl substituents we looked at the oxidative addition
reaction of 1,2-B2Cl2(NMe2)2 with [Pt(PPh3)2(η-C2H4)]. Oxid-
ative addition of this diborane(4) compound to metal centres
has been little studied, although recent work by Braunschweig
and co-workers10,11 has established that it is an effective source
of diboran(4)yl and borylene ligands in certain cases.
Fig. 4 A view of the molecular structure of compound 14 with key
atoms labelled. Details as in Fig. 2.
The reaction between [Pt(PPh3)2(η-C2H4)] and one equiv-
alent of 1,2-B2Cl2(NMe2)2 in toluene or benzene was monitored
by 31P NMR spectroscopy which revealed the presence of new
products in addition to substantial amounts of unchanged
starting materials. With an excess of 1,2-B2Cl2(NMe2)2 (≈3.5
equivalents) all of the platinum starting material was consumed
and three new products were formed as shown in Scheme 1
although the distribution of these products changed over time.
Ph3P
+
1,2-B2Cl2(NMe2)2
Pt
Ph3P
Ph3P
BCl(NMe2)
BCl(NMe2)
Ph3P
Cl
BCl(NMe2)
Ph3P
Cl
H
+
Pt
Pt
+
Pt
Fig. 5 A view of the molecular structure of compound 15 with key
atoms labelled. Details as in Fig. 2. Only the major component of the
disorder associated with the BCl(NMe2) ligand is shown.
Ph3P
PPh3
PPh3
14
15
Scheme 1
Table 4 Selected bond lengths (Å) and angles (Њ) for compound 14
One of the three products was identified as the known
Pt(1)–B(1)
Pt(1)–B(2)
Pt(1)–P(1)
Pt(1)–P(2)
2.084(3)
2.076(4)
2.3445(8)
2.3382(7)
B(1)–N(1)
B(2)–N(2)
B(1)–Cl(1)
B(2)–Cl(2)
1.378(4)
1.379(5)
1.861(4)
1.854(4)
1
compound trans-[PtH(Cl)(PPh3)2] (δP 28.6, JPt–P = 3022 Hz)2e
whilst NMR spectroscopic data (Table 1) for the other two were
consistent with the formulas cis-[Pt(PPh3)2{BCl(NMe2)}2] 14
and trans-[PtCl(PPh3)2{BCl(NMe2)}] 15. Compound 14 is
present as the major species early in the reaction but after
prolonged reaction times 15 starts to dominate. The amount of
the hydride trans-[PtH(Cl)(PPh3)2] present does not change over
time indicating that this is probably a side product possibly
resulting from some initial degree of hydrolysis but since
the mechanism of this reaction, particularly the apparent trans-
formation of 14 into 15, is unclear, any further speculation is
B(1)–Pt(1)–B(2)
B(1)–Pt(1)–P(1)
B(1)–Pt(1)–P(2)
B(2)–Pt(1)–P(1)
B(2)–Pt(1)–P(2)
P(1)–Pt(1)–P(2)
75.15(13)
92.48(9)
167.31(9)
167.63(9)
92.23(9)
Pt(1)–B(1)–N(1)
Pt(1)–B(1)–Cl(1)
Cl(1)–B(1)–N(1)
Pt(1)–B(2)–N(2)
Pt(1)–B(2)–Cl(2)
Cl(2)–B(2)–N(2)
128.7(3)
117.0(2)
114.3(2)
127.6(3)
117.5(2)
114.8(3)
100.13(3)
Table 5 Selected bond lengths (Å) and angles (Њ) for compound 15
1
unwarranted. The H NMR spectra for both 14 and 15 show
two sets of methyl resonances consistent with hindered rotation
about the B–N bonds.
Pt(1)–B(1)
Pt(1)–Cl(1)
2.075(10)
2.470(2)
Pt(1)–P(1)
Pt(1)–P(2)
2.291(2)
2.288(2)
Crystals of both compounds 14 and 15 were obtained from
toluene–hexane mixtures and the structures of both were
determined by X-ray crystallography. Views of the two struc-
tures are shown in Figs. 4 and 5 and selected bond lengths and
angles are presented in Tables 4 and 5. Compound 14 (Fig. 4),
which crystallises as a toluene solvate, adopts a structure typical
for this class of bis(boryl) compound2b,c,e,3b,7–9 for which the
notable parameters are the distances Pt(1)–B(1) 2.084(3) and
Pt(1)–B(2) 2.076(4) Å and the angles B(1)–Pt(1)–B(2) 75.15(13)
and P(1)–Pt(1)–P(2) 100.13(3)Њ all of which lie within prev-
iously observed ranges.9c All non-hydrogen atoms in each boryl
ligand are essentially coplanar, allowing for B–N π overlap,
these planes being nearly orthogonal to the mean platinum
B(1)–Pt(1)–Cl(1)
B(1)–Pt(1)–P(1)
B(1)–Pt(1)–P(2)
175.9(2)
90.4(2)
89.9(2)
Cl(1)–Pt(1)–P(1)
Cl(1)–Pt(1)–P(2)
P(1)–Pt(1)–P(2)
87.79(4)
91.82(4)
178.73(5)
square plane [dihedral angles: B(1), 86.5Њ; B(2), 80.1Њ]. The
structures of platinum() cis-bis(boryls) have been discussed in
detail [see ref. 9(c) and refs. therein] and no further comment
will be made here except to note that the Pt–B bond lengths are
not significantly different from those observed in a range of
diolate substituted species.9c On this basis, there is no real
structural evidence to indicate whether the BCl(NMe2) boryl
group is any better or worse as a π acceptor than other types of
J. Chem. Soc., Dalton Trans., 1999, 1687–1694
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boryl ligands. Indeed, in a range of structures with differing
boryl substituents and various phosphines, the Pt–B distances
all lie within a fairly narrow range9c which might be taken as
evidence for little Pt–B π bonding although small differences
in extent may not be reflected in significant bond length
variations.
The structure of compound 15 (Fig. 5) is similar to that of
trans-[PtCl(PPh3)2(Bcat)].7 In 14 the boryl groups avoid a
mutually trans configuration due to their high trans influence
but in 15 the presence of the weaker trans influence chloride
allows for the observed trans configuration. In contrast to
trans-[PtCl(PPh3)2(Bcat)] which has quite a short Pt–B bond
[2.008(8) Å],7 the Pt–B bond in 15 [Pt(1)–B(1) 2.075(10) Å]
is closer to those bonds found in 14. Some care should be
exercised in discussing the metric parameters associated with
the boryl (and chlorine) group in 15, however, due to a degree
of disorder associated with the orientation of the boryl group
as discussed in the Experimental section.
of atmospheric moisture or oxygen. The 31P-{1H} and 11B-{1H}
NMR data for all new complexes are given in Table 1.
Preparations and reactions
cis-[Pt(dcpe)(Bcat)2] 4. Samples of compound 1 (0.100 g,
0.095 mmol) and dcpe (0.040 g, 0.095 mmol) were transferred
to a 10 cm3 Young’s tap NMR tube and dissolved in toluene (≈2
cm3) resulting in a pale yellow solution. The solution was
analysed by 31P-{1H} and 11B-{1H} NMR spectroscopy which
showed essentially quantitative conversion into 4. The reaction
solution was then layered with hexane (≈3.0 cm3) but solvent
diffusion at room temperature afforded only oils and incom-
plete separation of PPh3; no analytically pure samples of 4 were
obtained. The reaction between 1 and dmpe was carried out
similarly. Precipitation of the products directly from toluene
afforded a white solid which was redissolved in CD2Cl2 and
analysed by 31P NMR spectroscopy.
In conclusion, we have shown that the phosphine ligands in
compound 1 are labile and readily substituted by a range of
more basic monodentate tertiary phosphines and diphosphines.
Whilst it has previously been demonstrated that platinum bis-
(boryls) with chelating diphosphines are not active diboration
catalysts, consistent with the active catalytic species having only
one bound phosphine,2e compounds such as 8–12 and particu-
larly 13 are currently being examined for their effectiveness in
catalysing the diboration of alkynes and other unsaturated
species. These studies together with results which demonstrate
that 14 is a very effective catalyst precursor for the addition of
1,2-B2Cl2(NMe2)2 to alkynes will form the basis of a future
report. In terms of any structural insight into the nature of the
Pt–B bond in platinum(), cis-bis(boryls), the results described
here for 13 and 14, together with the results of previous struc-
tural studies,9c show that the Pt–B bond lengths as well as the
orientations of the boryl ligands with respect to the platinum
square plane show little variation as a function of the groups
bound to boron or the nature of the phosphine bound to
platinum.
The reaction between compound 1 and dppm. Samples of
compound 1 (0.150 g, 0.143 mmol) and dppm (0.062 g, 0.161
mmol, 1.1 equivalents) were added to a 5 cm3 Young’s tap
NMR tube and dissolved in CD2Cl2 (≈0.75 cm3) resulting in an
orange solution which became red over time. Analysis by 31P-
{1H} and 11B-{1H} NMR spectroscopy at room temperature
and Ϫ90 ЊC (see text for details) showed the presence of 5 as the
major product. The reaction solution was then layered with
hexane (≈3 cm3) and solvent diffusion over a period of days at
room temperature afforded red crystals of 6 and minor quan-
tities of orange crystals of 7. When 2.6 molar equivalents of
dppm were used larger quantities of 7 were obtained but in
neither reaction were the yields of 6/7 high although crystals of
each compound were suitable for X-ray crystallography. Com-
pound 5 could not be isolated as a solid (see Table 1 for NMR
data) and obtaining satisfactory analytical data and NMR
spectra for 6 and 7 was hampered by low yields and the fact that
both compounds crystallised together making separation
difficult.
cis-[Pt(PMePh2)2(Bcat)2] 11. A sample of compound 1 (0.100
g, 0.095 mmol) was transferred to a 5 cm3, Young’s tap NMR
tube and dissolved in CD2Cl2 (≈0.75 cm3) to which PMePh2
(36 µL, 0.19 mmol) was added via syringe resulting in an orange
solution. Analysis by 31P-{1H} and 11B-{1H} NMR spec-
troscopy revealed the presence of 11 in essentially quantitative
yield although attempts at crystallisation did not afford analyt-
ically pure samples as only oily products were obtained. The
reactions with PMe3, PEt3, PMe2Ph, P(OEt)3 and P(OMe)3
were performed similarly, NMR data for which are given in
Table 1 and, where appropriate, in the text. In the case of the
reaction with PMe3 evidence for the presence of the PMe3
adducts of B2(cat)2 was obtained when an excess of PMe3 was
used. These adducts were also prepared by addition of
two equivalents of PMe3 to B2(cat)2 in CHCl3: NMR, [B2(cat)2-
(PMe3)], 11B-{1H} δ 37.6 (B) and Ϫ14.6 (Me3P→B), 31P-{1H}
Ϫ12.2; [B2(cat)2(PMe3)2], 11B-{1H} δ 1.5, 31P-{1H} δ Ϫ4.5.
Experimental
General procedures
Except where indicated all operations were carried out under
dry dinitrogen or argon atmospheres using standard Schlenk
and vacuum line techniques. All non-deuteriated solvents
used were distilled over appropriate drying agents prior
to use. Deuteriated solvents were dried over molecular sieves
and degassed by three freeze–pump–thaw cycles under
nitrogen.
High field NMR spectra were recorded using a JEOL
GX-400 spectrometer [11B-{1H} at 128.4 MHz and 31P-{1H} at
161.3 MHz], a JEOL Lambda 300 spectrometer [11B-{1H} at
96.3 MHz and 31P-{1H} at 121.5 MHz] or a JEOL EX-90
spectrometer [11B-{1H} at 26.8 MHz and 31P-{1H} at 36.1
MHz]. Chemical shifts are reported in ppm relative to external
or internal (JEOL EX-90) BF3ؒEt2O and 85% H3PO4.
Compound 12e was prepared from the reaction between
[Pt(PPh3)2(η-C2H4)]28 and B2(cat)2.29 The compound 1,2-B2Cl2-
(NMe2)2 was prepared according to the literature method.30
The phosphines dppm, dmpe, dcpe and PCy3 were used as
purchased without further purification, while PMe3, PEt3,
PMe2Ph, PMePh2, P(OEt)3 and P(OMe)3 were distilled under
argon and stored over molecular sieves (3 Å).
Liquid phosphines and phosphites were as added as stock
solutions (EX-90) or neat via micro-syringe (Lambda 300,
GX-400) depending on the instrumentation for characteris-
ation. Typical reactions are described below. Unless otherwise
indicated, the presence of trace amounts of diborane(4)
decomposition products were apparent in the 11B-{1H} NMR
spectra of several solutions due to reactions with trace amounts
cis-[Pt(PCy3)(PPh3)(Bcat)2] 13. Samples of compound 1
(0.075 g, 0.071 mmol) and PCy3 (0.044 g, 0.157 mmol) were
added to a 10 cm3 Young’s tap NMR tube and dissolved in
CD3C6D5 (≈3 cm3) resulting in a pale yellow suspension which
was gently warmed until all solids had dissolved. Analysis by
31P-{1H} and 11B-{1H} NMR spectroscopy showed essentially
quantitative conversion into 13. Addition of an overlayer of n-
hexane (≈3 cm3) and subsequent solvent diffusion at room tem-
perature afforded intimate mixtures of of PPh3 and 13 which
prevented obtaining satisfactory elemental analytical data.
The reaction between [Pt(PPh3)2(ç-C2H4)] and 1,2-B2Cl2-
(NMe2)2. A sample of [Pt(PPh3)2(η-C2H4)] (0.100 g, 0.134
1692
J. Chem. Soc., Dalton Trans., 1999, 1687–1694

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Table 6 Selected crystallographic details for the complexes 6ؒCH2Cl2, 7ؒ0.15 C6H14ؒ0.69 CH2Cl2, 13, 14ؒ0.5 CD3C6D5 and 15
6ؒCH2Cl2
7ؒ0.15 C6H14ؒ0.69 CH2Cl2
13
14ؒ0.5 CD3C6D5
15
Empirical formula
Formula weight
C81H69B2Cl2O4P5Pt2
1743.91
C88.61H77.54B2Cl1.38O4P6Pt2
1853.14
C48H56B2O4P2Pt
975.58
C43.5H45.5B2Cl2N2P2Pt C38H36BCl2NP2Pt
945.87
845.42
Crystal system
Space group
Monoclinic
C2/c
Monoclinic
P21/c
Monoclinic
P21/n
Triclinic
P1
Triclinic
P1
¯
¯
a/Å
b/Å
c/Å
α/Њ
47.493(13)
12.601(3)
24.635(7)
22.880(4)
14.210(2)
26.731(4)
16.752(3)
12.174(2)
22.850(2)
11.2268(10)
12.0715(14)
17.3490(30)
85.897(8)
72.861(10)
69.461(8)
2102.6(5)
173(2)
10.865(5)
12.093(6)
14.228(5)
95.819(6)
92.523(10)
105.637(6)
1786.1(13)
173(2)
β/Њ
96.442(14)
114.248(10)
111.428(10)
γ/Њ
V/Å3
14651(7)
173(2)
8
7924(2)
173(2)
4
4337.9(11)
173(2)
4
T/K
Z
2
2
µ/mmϪ1
4.047
3.746
3.352
3.572
4.195
Total reflections
Independent reflections
Rint
R1 [I > 2σ(I)] (data)
Extinction coefficient
33762
11470
0.1854
0.0823 (5148)
—
60301
12447
0.1562
0.0656 (7765)
0.00014(2)
27083
9917
0.0517
0.0356 (7258)
0.00020(2)
21868
9499
0.0315
0.0240 (8089)
0.00051(7)
14303
5583
0.0478
0.0307 (4722)
—
mmol) was placed into a scintillation vial to which a solution of
1,2-B2Cl2(NMe2)2 (0.080 g, 0.443 mmol) in C6D6 (or CD3C6D5,
CH3C6H5) (≈1 cm3) was added via pipette. The resulting
solution was then stirred for one hour and transferred to a
NMR tube and analysed by 31P-{1H} and 11B-{1H} NMR spec-
troscopy after which it was transferred to a clean scintillation
vial. Colourless crystals of 14 and 15 suitable for X-ray crystal-
lography were obtained by slow diffusion of n-hexane (≈10 cm3)
into the reaction mixture over a period of three days at room
temperature. Satisfactory elemental analysis could not be
CCDC reference number 186/1386.
See http://www.rsc.org/suppdata/dt/1999/1687/ for crystallo-
graphic files in .cif format.
Acknowledgements
N. C. N. thanks the EPSRC, Laporte plc and The Royal Society
for research support. Johnson Matthey Ltd. and E.I. Du Pont
De Nemours & Co., Inc. are thanked for generous supplies of
platinum salts.
1
obtained due to the co-crystallisation of the two products. H
NMR: for 14 (CD3C6D5), δ 7.58 (m, 12 H, PPh3), 6.92 (m, 18 H,
PPh3), 2.87 (s, 6 H, NMe2) and 2.57 (s, 6 H, NMe2); for 15
(C6D6), δ 7.96 (m, 12 H, PPh3), 7.05 (m, 18 H, PPh3), 2.46 (s, 3
H, NMe2) and 1.91 (s, 3 H, NMe2); for trans-[PtH(Cl)(PPh3)2]
(C6D6), δ 7.86 (m, 12 H, PPh3), 7.03 (m, 18 H, PPh3) and Ϫ15.3
References
1 T. Ishiyama, M. Yamamoto and N. Miyaura, Chem. Commun.,
1997, 689; C. N. Iverson and M. R. Smith, Organometallics, 1997,
16, 2757; T. B. Marder, N. C. Norman and C. R. Rice, Tetrahedron
Lett., 1998, 39, 155.
2 (a) T. Ishiyama, N. Matsuda, N. Miyaura and A. Suzuki, J. Am.
Chem. Soc., 1993, 115, 11018; (b) T. Ishiyama, N. Matsuda,
M. Murata, F. Ozawa, A. Suzuki and N. Miyaura, Organometallics,
1996, 15, 713; (c) C. N. Iverson and M. R. Smith, J. Am. Chem. Soc.,
1995, 117, 4403; (d) A. Maderna, H. Pritzkow and W. Siebert,
Angew. Chem., Int. Ed. Engl., 1995, 35, 1501; (e) G. Lesley,
P. Nguyen, N. J. Taylor, T. B. Marder, A. J. Scott, W. Clegg and N. C.
Norman, Organometallics, 1996, 15, 5137; ( f ) C. N. Iverson and
M. R. Smith, Organometallics, 1996, 15, 5155.
3 (a) T. Ishiyama, M. Yamamoto and N. Miyaura, Chem. Commun.,
1996, 2073; (b) W. Clegg, T. R. F. Johann, T. B. Marder, N. C.
Norman, A. G. Orpen, T. M. Peakman, M. J. Quayle, C. R. Rice
and A. J. Scott, J. Chem. Soc., Dalton Trans., 1998, 1431.
4 Y. G. Lawson, M. J. G. Lesley, T. B. Marder, N. C. Norman and
C. R. Rice, Chem. Commun., 1997, 2051.
1
2
(dt, 1 H, JPt–H 1163, JP–H 12 Hz); 31P and 11B NMR data are
given in Table 1.
X-Ray crystallography
Crystals were mounted in inert oil under a stream of argon and
transferred to the cold gas stream of the diffractometer.
Crystallographic data for compounds 6, 7, 13, 14 and 15 (6, 7
and 14 as solvates) are presented in Table 6. Measurements were
made on a Siemens SMART CCD area detector diffractometer
with Mo-Kα radiation (λ = 0.71073 Å). Intensities were
integrated from several series of exposures, each exposure
covering 0.3Њ in ω, with the total data set being more than a
hemisphere in each case. Absorption corrections were applied,
based on multiple and symmetry equivalent measurements. The
structures were solved and refined by standard methods.31
The high values of Rint for complexes 6 and 7 are probably
caused by loss of solvent from the crystals prior to mounting on
the diffractometer. No crystal decay was observed over the data
collection period in either case. The crystal structure of 6
contains 2 solvent molecules of dichloromethane (deuteriated),
one of which is disordered over an inversion centre and the
other exists in two different orientations. The crystal structure
5 T. Ishiyama, T. Kitano and N. Miyaura, Tetrahedron Lett., 1998, 39,
2357.
6 S. Sakaki and T. Kikuno, Inorg. Chem., 1997, 36, 226; Q. Cui, D. G.
Musaev and K. Morokuma, Organometallics, 1997, 16, 1355.
7 W. Clegg, F. J. Lawlor, G. Lesley, T. B. Marder, N. C. Norman,
A. G. Orpen, M. J. Quayle, C. R. Rice, A. J. Scott and F. E. S. Souza,
J. Organomet. Chem., 1998, 550, 183.
8 A. Kerr, T. B. Marder, N. C. Norman, A. G. Orpen, M. J. Quayle,
C. R. Rice, P. L. Timms and G. R. Whittell, Chem. Commun., 1998,
319.
9 (a) H. Wadepohl, Angew. Chem., Int. Ed. Engl., 1997, 36, 2441; (b)
T. B. Marder and N. C. Norman, Topics in Catalysis, eds. W. Leitner
and D. G. Blackmond, Baltzer Science Publishers, Amsterdam,
1998, vol. 5, p. 63; (c) G. J. Irvine, M. J. G. Lesley, T. B. Marder,
N. C. Norman, C. R. Rice, E. G. Robins, W. R. Roper, G. R.
Whittell and L. J. Wright, Chem. Rev., 1998, 98, 2685.
10 H. Braunschweig, B. Ganter, M. Koster and T. Wagner, Chem. Ber.,
1996, 129, 1099.
11 H. Braunschweig and M. Müller, Chem. Ber., 1997, 130, 1295.
12 W. Clegg, F. J. Lawlor, T. B. Marder, P. Nguyen, N. C. Norman,
A. G. Orpen, M. J. Quayle, C. R. Rice, E. G. Robins, A. J. Scott,
F. E. S. Souza, G. Stringer and G. R. Whittell, J. Chem. Soc., Dalton
Trans., 1998, 301.
of
7 contains disordered hexane and dichloromethane
(deuteriated) in the ratio 0.15:0.69. The consequences of the
disordered solvent in these structures are evident in the dis-
placement parameters of atoms in the Bcat ligands which are
themselves somewhat disordered. The crystal structure of 14
contains toluene which is disordered over an inversion centre.
That of 15 shows two orientations of the BCl(NMe2) ligand,
related by a 180Њ rotation about the Pt–B bond, which are dis-
ordered in the ratio 0.76:0.24. A second position for the trans
chloride could not be located in the difference map.
J. Chem. Soc., Dalton Trans., 1999, 1687–1694
1693

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13 C. A. Tolman, Chem. Rev., 1977, 77, 313.
14 G. K. Anderson and G. J. Lumetta, Inorg. Chem., 1987, 26, 1518.
15 P. E. Garrou, Inorg. Chem., 1975, 14, 1435.
16 K. A. Azam, A. A. Frew, B. R. Lloyd, L. Manojlovic-Muir, K. W.
Muir and R. J. Puddephatt, Organometallics, 1985, 4, 1400.
17 M. P. Brown, S. J. Cooper, A. A. Frew, L. Manojlovic-Muir, K. W.
Muir and R. J. Puddephatt and M. A. Thompson, J. Chem. Soc.,
Dalton Trans., 1982, 299.
18 C.-M. Che, V. W.-W. Yam, W.-T. Wong and T.-F. Lai, Inorg. Chem.,
1989, 28, 2908.
19 R. J. Puddephatt, M. A. Thomson, L. Manojlovic-Muir, K. W.
Muir, A. A. Frew and M. P. Brown, J. Chem. Soc., Chem.
Commun., 1981, 805.
20 M. P. Brown, S. J. Cooper, A. A. Frew, L. Manojlovic-Muir, K. W.
Muir, R. J. Puddephatt, K. R. Seddon and M. A. Thomson, Inorg.
Chem., 1981, 20, 1500.
21 L. Manojlovic-Muir, K. W. Muir and T. Solomun, Acta Crystallogr.,
Sect. B, 1979, 35, 1237.
22 L. Manojlovic-Muir and K. W. Muir, J. Organomet. Chem., 1981,
219, 129; M. P. Brown, J. R. Fisher, L. Manojlovic-Muir, K. W.
Muir, R. J. Puddephatt, M. A. Thomson and K. R. Seddon,
J. Chem. Soc., Chem. Commun., 1979, 931.
24 S. A. Westcott, N. J. Taylor, T. B. Marder, R. T. Baker, J. C.
Calabrese and R. L. Harlow, manuscript in preparation.
25 (a) P. Nguyen, C. Dai, N. J. Taylor, W. P. Power, T. B. Marder, N. L.
Pickett and N. C. Norman, Inorg. Chem., 1995, 34, 4290; (b)
W. Clegg, C. Dai, F. J. Lawlor, T. B. Marder, P. Nguyen, N. C.
Norman, N. L. Pickett, W. P. Power and A. J. Scott, J. Chem. Soc.,
Dalton Trans., 1997, 839.
26 P. A. Chaloner and G. T. L. Broadsword-Strong, J. Chem. Soc.,
Dalton Trans., 1996, 1039.
27 P. S. Pregosin and S. N. Sze, Helv. Chim. Acta., 1977, 60, 1371.
28 M. Camalli, F. Caruso, S. Chaloupka, E. M. Leber, H. Rimml and
L. M. Venanzi, Helv. Chim. Acta, 1990, 73, 2263.
29 F. J. Lawlor, N. C. Norman, N. L. Pickett, E. G. Robins, P. Nguyen,
G. Lesley, T. B. Marder, J. A. Ashmore and J. C. Green, Inorg.
Chem., 1998, 37, 5282.
30 H. Nöth and W. Meister, Z. Naturforsch., Teil B, 1962, 17,
714.
31 SMART (control) and SAINT (integration) software, Siemens
Analytical X-ray Instruments Inc., Madison, WI, 1994; G. M.
Sheldrick, SHELXTL, version 5, Siemens Analytical X-ray
Instruments Inc., Madison, WI, 1995.
23 L. Manojlovic-Muir and K. W. Muir, J. Chem. Soc., Chem.
Commun., 1982, 1155.
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