Binuclear Hydridoplatinum(II): One-Pot Synthesis, INS Spectra and X-ray Crystal Structure of [Pt2(dcype)2(H)3][BPh 4] {dcype = 1,2-Bis(dicyclohexylphosphanyl)ethane}

Article abstract of DOI:10.1002/ejic.200300252

The binuclear platinum(II) hydride [Pt₂(dcype) ₂(H)₃][Cl] (1b) has been isolated in high yields by treatment of Pt(dcype)Cl₂ with NaBH₄ (molar ratio 1:2) in ethanol solution at room temperature. This one-pot synthesis is not straightforward when starting from diphenylphosphanylalkane complexes. The compounds [Pt₂(dppp)₂(H)₃][OH] (3b) and [Pt₂(dppb)₂(H)₃][OH] (4) were isolated by starting from the mononuclear hydrides {cis-[Pt(P-P)(H)₂]} while mixtures of both binuclear {[Pt₂(dppe)₂(H) ₃]⁺, 5} and trinuclear {[Pt₃(dppe) ₃(H)₃]⁺, 6} trihydrides were obtained with the dppe ligand. Various salts of the cation 1, [Pt₂(dcype) ₂(H)₃][X] (X = BF₄, 1a; OH, 1c; BPh ₄, 1d), were isolated either from [Pt(dcype)(μ-OH)] ₂[BF₄]₂ (2) by a general procedure (1a), or by decomposition of the complex cis-[Pt(dcype)(H)₂] in solution (1c), as well as by metathesis reactions (1a, 1c, and 1d). Compounds 1a, 1b, and 1d react with CO under mild conditions to afford the corresponding Pt^I binuclear hydrides [Pt₂(dcype)₂(μ-CO)(μ-H)][X] (X = Cl, 7a; BF₄, 7b; BPh₄, 7c). The binuclear core of cation 1 is broken by KCN in methanol solution, yielding the mononuclear complex cis-[Pt(dcype)(CN)(H)] (8). The complexes 1a-d, 2, 7a-c, and 8 have been characterised by FAB MS, IR, and NMR (¹H, ³¹P, and ¹⁹⁵Pt) spectroscopic techniques; the 1 and 7 cations show fluxional behaviour on the NMR timescale. The structure of compound 1d was determined, at 200 K, by single-crystal X-ray diffraction. All the hydrido ligands were located. The Pt-Pt separation is 2.696(1) A and the coordination geometry around each platinum centre can be regarded as distorted square planar. Incoherent Inelastic Neutron Scattering (INS) spectra were obtained for la and [Pt₂(dppe)₂(H)₃][BF₄] (5a); the spectra reflect the different geometries of the two "P₄Pt ₂(H)₃" cores as found by single-crystal structure determinations. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300252

FULL PAPER
Binuclear Hydridoplatinum(II): One-Pot Synthesis, INS Spectra and X-ray
Crystal Structure of [Pt2(dcype)2(H)3][BPh4]
{dcype ؍ 1,2-Bis(dicyclohexylphosphanyl)ethane}
Anna Laura Bandini,*[a] Guido Banditelli,[a] Mario Manassero,*[b] Alberto Albinati,*[b]
Daniele Colognesi,[c] and Juergen Eckert[d,e]
Keywords: Hydride ligands / INS spectroscopy / Phosphane ligands / Platinum / X-ray diffraction
The binuclear platinum(II) hydride [Pt2(dcype)2(H)3][Cl] (1b)
has been isolated in high yields by treatment of Pt(dcype)Cl2
with NaBH4 (molar ratio 1:2) in ethanol solution at room tem-
perature. This one-pot synthesis is not straightforward when
starting from diphenylphosphanylalkane complexes. The
compounds [Pt2(dppp)2(H)3][OH] (3b) and [Pt2(dppb)2-
(H)3][OH] (4) were isolated by starting from the mononuclear
hydrides {cis-[Pt(P-P)(H)2]} while mixtures of both binuclear
{[Pt2(dppe)2(H)3]+, 5} and trinuclear {[Pt3(dppe)3(H)3]+, 6} trih-
7a; BF4, 7b; BPh4, 7c). The binuclear core of cation 1 is
broken by KCN in methanol solution, yielding the mononu-
clear complex cis-[Pt(dcype)(CN)(H)] (8). The complexes
1a−d, 2, 7a−c, and 8 have been characterised by FAB MS, IR,
and NMR (1H, 31P, and 195Pt) spectroscopic techniques; the 1
and 7 cations show fluxional behaviour on the NMR time-
scale. The structure of compound 1d was determined, at
200 K, by single-crystal X-ray diffraction. All the hydrido li-
˚
gands were located. The Pt−Pt separation is 2.696(1) A and
ydrides were obtained with the dppe ligand. Various salts of the coordination geometry around each platinum centre can
the cation 1, [Pt2(dcype)2(H)3][X] (X = BF4, 1a; OH, 1c; BPh4,
1d), were isolated either from [Pt(dcype)(µ-OH)]2[BF4]2 (2) by
a general procedure (1a), or by decomposition of the complex
cis-[Pt(dcype)(H)2] in solution (1c), as well as by metathesis
reactions (1a, 1c, and 1d). Compounds 1a, 1b, and 1d react
be regarded as distorted square planar. Incoherent Inelastic
Neutron Scattering (INS) spectra were obtained for 1a and
[Pt2(dppe)2(H)3][BF4] (5a); the spectra reflect the different
geometries of the two ‘‘P4Pt2(H)3’’ cores as found by single-
crystal structure determinations.
with CO under mild conditions to afford the corresponding ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
PtI binuclear hydrides [Pt2(dcype)2(µ-CO)(µ-H)][X] (X = Cl,
Germany, 2003)
Introduction
obidentate (bridging) diphosphane,[3] a number of species
with chelating diphosphanes (P-P) have also been
Since the first examples Ϫ [Pt2(PR3)2(H)2(SiR3)2], re-
ported by M. Green and co-workers[1] Ϫ binuclear platinum
hydrides have been a topic of continuous interest. Besides
complexes with monodentate tertiary phosphanes[2] or ex-
described.[4Ϫ6] These complexes include 30-electron species,
[5]
both neutral [Pt(P-P)(H)]2
and cationic [Pt2(P-
P)2(H)3]ϩ,[4] as well as 28-electron [Pt(P-P)(H)]22ϩ species.[6]
The observed differences in their formation, spectroscopic
properties and molecular structures seem to be largely de-
pendent on the ancillary diphosphanyl ligand. Moreover,
when chelating diphosphanes have been used, only a few
examples of mononuclear cis-dihydrides {cis-[Pt(P-P)(H)2]}
have been described.[4d,5a,5c,7]
[a]
CNR-ISTM and Dipartimento di Chimica Inorganica,
`
Metallorganica e Analitica, Universita degli Studi di Milano,
Via G. Venezian, 21 20133 Milano, Italy
E-mail: annalaura.bandini@unimi.it
Dipartimento di Chimica Strutturale
[b]
e
Stereochimica
`
Inorganica and INFM, UdR Milano, Universita degli Studi
di Milano
The trihydrido cations {[Pt2(P-P)2(H)3]ϩ} have been
widely investigated. In solution they show fluxional behav-
iour on the NMR timescale over a wide temperature range,
at least down to 183 K. Typically, only one resonance for
the hydrides is observed in the 1H NMR spectrum, coupled
to four 31P and two 195Pt magnetically equivalent nuclei. In
the solid state, however, two distinct types of structure have
been observed, with either a (H)Pt(µ-H)2Pt or a (H)Pt(µ-
H)Pt(H) core. The former arrangement, with two bridging
Via G. Venezian, 21 20133 Milano, Italy
E-mail: alberto.albinati@unimi.it
m.manassero@istm.cnr.it
[c]
[d]
[e]
CNR Istituto di Fisica Applicata ‘‘Nello Carrara’’
50127 Firenze, Italy
LANSCE, Los Alamos National Laboratory,
Los Alamos, NM 87545, USA
Materials Research Laboratory, University of California Santa
Barbara, Santa Barbara, CA 93106, USA.
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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DOI: 10.1002/ejic.200300252
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967

Binuclear Hydridoplatinum()
FULL PAPER
and one terminal hydride, implies different environments mediates: cationic bis-pyrazole adducts (i) or µ-hydroxo bi-
for the two platinum atoms, as found in the structures of nuclear cations (ii), as summarised in Scheme 1.
[Pt2{Ph2P(CH2)2PPh2}2(H)3]ϩ [4c,8] and [Pt2{(Ph2PC5H4)2-
In the current case (P-P ϭ dcype), attempts to operate
Fe}2(H)3]ϩ.[4f] On the other hand, the coordination geo- according to path (i) were unsuccessful, owing to difficulties
metries of the two platinum atoms in the structures of in isolating the pyrazolato precursor. Similarly, pathway (ii)
[Pt2(dtbpp)2(H)3]ϩ [4b] and [Pt2(butaphos)2(H)3]ϩ [4g] are ap- was also unsatisfactory; compound [Pt2(dcype)2(H)3][BF4]
proximately the same, and are consistent with the presence (1a) was isolated, but yields were erratic and often mod-
of two terminal and one bridging hydrides.
est.[10] Analytical and NMR spectroscopic data suggested
Different factors could be considered in order to explain the formation of complex reaction mixtures in the first step:
the observed differences in the solid state, in particular: the synthesis of the binuclear µ-hydroxo complex
(i) the influence of the bite angle of the chelating ligands, [Pt(dcype)(µ-OH)]2[BF4]2 (2). The 31P{1H} NMR spectra
and (ii) the steric demand of the substituents on the phos- of the crude products showed, besides the signals of com-
phorus atoms. Moreover, more subtle factors, such as crys- pound 2, a number of resonances in the 55Ϫ75 ppm range,
tal-packing forces, could also be responsible for the exist- probably due to other platinum species with oxygen donors.
1
ence of different structures involving small energy differ- The values of the JP,Pt coupling constants, 3900Ϫ3400 Hz,
ences.
suggest species with a trans PϪPtϪO arrangement with
In pursuit of our interest in platinum polynuclear hy- anionic (OH or OR) rather than neutral (H2O or CH3OH)
drides, we report here the synthesis of the complexes ligands (e.g. ref.[11b]). The chelating behaviour of dcype is
[Pt2(dcype)2(H)3][X] (Xϭ BF4, 1a; Cl 1b; OH, 1c; BPh4, 1d) confirmed by the large 31P downfield shift with respect to
and the X-ray crystal structure of the BPh4 salt. In ad- the free ligand (∆δ ϭ 50Ϫ70 ppm).
dition, the Incoherent Inelastic Neutron Spectra of com-
An analytical sample of the intermediate 2 was isolated
plexes 1a and [Pt2(dppe)2(H)3][BF4] (5a) are also reported.
from the crude product as a less soluble species in acetone.
Complex 1b can be obtained in good yields directly from Its spectroscopic (IR, 3lP{1H} NMR, and FAB MS)
[Pt(dcype)Cl2] by a one-pot reaction. This synthetic ap- properties (see Exp. Sect.) are highly reminiscent of those
proach has also been used with less sterically demanding of homologous cations with various bis(diphenylphosphan-
bis-diphenylphosphanylalkanes: satisfactory yields have yl)alkanes.[11]
been obtained in the case of dppp {[Pt2(dppp)2(H)3]ϩ, 3}
The cation [Pt2(dcype)2(H)3]ϩ (1) had previously been de-
and dppb {[Pt2(dppb)2(H)3]ϩ, 4} ligands, but the quantitat- tected in solution by multinuclear NMR spectra either as
ive conversion of Pt(P-P)Cl2 was only obtained when the the final product of the decomposition of cis-[Pt(dcy-
corresponding mononuclear hydrides {cis-[Pt(P-P)(H)2]} pe)(H)2][7b] or as that of the protonation of the platinum()
were isolated and then converted into the corresponding bi- dihydride [Pt(dcype)(H)]2,[5a] this compound also being re-
nuclear cations. With dppe mixtures, both binuclear versibly obtained from cis-[Pt(dcype)(H)2][5a] (see
{[Pt2(dppe)2(H)3]ϩ, 5} and trinuclear {[Pt3(dppe)3(H)3]ϩ, 6} Scheme 2).
trihydrides were obtained.
It therefore seemed that cation 1 might be directly obtain-
The [Pt2(dcype)2(H)3][X] species react with CO under able in a one-pot reaction, through the controlled decompo-
mild conditions to give the binuclear p1atinum() hydrides sition of cis-[Pt(dcype)(H)2]. Indeed, we were able to obtain
[Pt(dcype)2(µ-CO)(µ-H)]ϩ (X ϭ Cl, 7a; BF4, 7b; BPh4, 7c). the complex [Pt2(dcype)2(H)3][Cl] (1b) in high yields by
The monuclear hydrido complex cis-[Pt(dcype)(CN)(H)] treatment of a dichloromethane solution of [Pt(dcype)Cl2]
Ϫ
(8) has been obtained from the reaction between 1b and with an ethanol solution of NaBH4 (Pt/BH4 mo1ar ratio
KCN in methanol solution.
1:2) at room temperature (under dinitrogen atmosphere).
A preliminary report of this work has already ap- At lower reaction temperatures the yield was decreased and
peared.[9]
unchanged [Pt(dcype)Cl2] was recovered. Significant
Throughout this paper the chelating diphosphanyl li- amounts of the mononuclear dihydride cis-[Pt(dcype)(H)2]
gands (P-P) are indicated as follows: dcype, 1,2-bis(dicy- have occasionally been detected in the crude products of
clohexylphosphanyl)ethane; dtbpe, 1,2-bis(di-tert-buthyl- synthesis reactions of compound 1b; these could be con-
phosphanyl)ethane; dppe, 1,2-bis(diphenylphosphanyl)- verted into the compound [Pt2(dcype)2(H)3][OH] (1c) by
ethane; dfepe, 1,2-bis[bis(perfluoroethyl)phosphanyl]ethane treatment with wet methanol.
(C2F5)2PCH2CH2P(C2F5); dtbpp, 1,3-bis(di-tert-butylphos-
The corresponding tetrafluoroborate 1a and the tetraphe-
phanyl)propane; dippp, 1,3-bis(diisopropylphosphanyl)pro- nylborate [Pt2(dcype)2(H)3][BPh4] (1d) were easily obtained
pane; dppp, 1,3-bis(diphenylphosphanyl)propane; but- from 1b through a metathesis reaction with a large excess
aphos,
1-(diphenylphosphinoxy)-2-[N-ethyl-N-(diphenyl- of the sodium salt of the appropriate anion in methanol
phosphanyl)amino]butane; dppb, 1,4-bis(diphenylphos- solution. Moreover, the more nucleophilic CNϪ anion dis-
phanyl)butane.
rupts the binuclear core. Under analogous experimental
conditions, complex 1b and KCN react to give, in high
yields, the mononuclear hydride cis-[Pt(dcype)(CN)(H)] (8),
which in turn, in CDCl3 solution, slowly decomposes to
Results and Discussion
Our previously reported platinum binuclear trihydrides afford mixtures of cis-[Pt(dcype)Cl2] and cis-[Pt(dcy-
[Pt2(P-P)2(H)3]ϩ were synthesised from two different inter- pe)(CN)(Cl)] (9). This decomposition path gave a clue for
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967
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FULL PAPER
Scheme 1
Scheme 2. For a detailed discussion of the steps summarised in this scheme see references [4Ϫ8]
reliable assignment of the NMR parameters of complex 8 phenylphosphanyl)alkane derivatives (dppe, dppp, and
(see Exp. Sect.), which indicate a larger trans influence from dppb) as ligands.
the terminal hydride [1JP(trans-H)-Pt ϭ 1714 Hz] than from
As far as we know, only two examples of cis-[Pt(P-P)(H)2]
compounds with (diphenylphosphanyl)alkane ligands (P-
the cyanide ligand [1JP(trans-CN)ϪPt ϭ 2706 Hz].
A significant improvement was obtained on carrying out P ϭ dppp, dppb) have been isolated and characterised; both
the synthesis of compound 1b starting from [Pt(COD)Cl2], are unstable in the absence of a dihydrogen atmosphere.[7c]
the commonest precursor of Pt(P-P)Cl2 species. Yields of In the dppe case, the mononuclear hydride was reported to
1b close to 65% were obtained under the same experimental be a source either of Pt0 species[7a] or of various hydrides.[4d]
conditions by sequential addition of dcype ligand and Carmichael and co-workers inferred from a VT. NMR
NaBH4 to a dichloromethane solution of [Pt(COD)Cl2].
The role of the mononuclear cis-[Pt(P-P)(H)2] complexes formation follows the sequence:[4d] cis-[Pt(dppe)(H)2],
to give platinum polyhydrides is summarised in Scheme 2.
[Pt(dppe)(H)]2, [Pt2(dppe)2(H)3]ϩ, and then [Pt3-
It is also worth notice that the neutral PtI and 28 eϪ (dppe)3(H)3]ϩ.
study (from 233 K to room temperature) that the hydride
dihydrido species have been isolated only with aliphatic di-
We carried out a few attempts under different conditions
phosphanes and that the complex cis-[Pt(dcype)(H)2] seems (see Exp. Sect.) starting from the appropriate [Pt(P-P)Cl2]
to be the unique complex that acts as an effective precursor precursor and obtained the binuclear hydrides [Pt2(P-
of all the known types of binuclear polyhydrides.
P)2(H)3][Cl] (P-P ϭ dppp, 3a; P-P ϭ dppe, 5b). However the
Thus, if the cis-[Pt(P-P)(H)2] complexes are assumed to one-pot reaction was unattractive, due to the unsatisfactory
function as effective precursors in the formation of the bi- yields. With the dppe ligand, the major product was always
nuclear trihydrides directly from [Pt(P-P)Cl2], a dimeris- the trinuclear cation [Pt3(dppe)3(H)3]ϩ (6),[4d,12] the product
ation (see Scheme 2) aimed at a one-step synthesis could be of a formal addition of a (P-P)Pt0 fragment to the binuclear
envisaged under experimental conditions designed to en- cation 5.
hance the lifetime of the mononuclear cis-dihydrides and
However, compounds [Pt2(P-P)2(H)3][OH] (P-P ϭ dppp,
avoid total dihydrogen loss (the most favoured reaction). 3b; P-P ϭ dppb, 4) were obtained in nearly quantitative
We tested this approach to obtain complexes bearing bis(di- yields, provided that the corresponding mononuclear hy-
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Eur. J. Inorg. Chem. 2003, 3958Ϫ3967

Binuclear Hydridoplatinum()
FULL PAPER
drides were isolated. These were quickly converted into 3b tion, it is worth comparing their relevant IR and NMR
and 4, respectively, after dissolution, under dinitrogen, in spectroscopic properties (see Table 1).
common organic solvents (e.g. chloroform).
In the IR spectra, the region of the terminal PtϪH
stretching seems to be a diagnostic feature: the 28 eϪ species
do not in fact show any vibration in this region, while one
or two bands are observed in the case of 30 eϪ complexes
(the PtII cations and the neutral PtI species, respectively).
In the NMR spectra the multiplicities of the main reson-
ances, as well as the satellites’ intensities, have no diagnostic
value, owing to the fluxionality and identical nuclearity
mentioned above. Significant differences between various
NMR parameters are observed, however. Provided that the
same diphosphanyl ligand is present, the following points
can be used in order to distinguish the different binuclear
hydrides: (i) greater 1JHϪPt values are associated with 28 eϪ
species, (ii) shifts towards higher field of the hydrido reson-
The same conversion also occurs in the solid state: after
two months,
a not carefully stored sample of cis-
[Pt(dppp)(H)2] was found to have been fully converted into
compound 3b. Dimerisation reactions in the solid state are
not unprecedented, but in the present case, in addition to a
facile H2 loss, the process requires a proton source, reason-
ably atmospheric moisture. In solution we cannot exclude
different processes, as previously suggested for, for example,
the formation of the cations [Pt2{R2P(CH2)nPR2}2(H)3]ϩ
[R ϭ tBu, n ϭ 2 (dtbpe), 3 (dtbpp)].[4b]
In the case of the dppe ligand, the one-pot reaction seems
to be more profitable for synthesis of the trinuclear 6 species
than of the binuclear 5. The yield of compound 6, calcu-
lated from the amounts of [Pt(dppe)Cl2] consumed, reached
65%, a significant improvement with respect to the values
2
ances and smaller JP,P values are observed in the case of
the 30 eϪ cations, and (iii) the neutral PtI complexes show
2
the greatest JP,Pt values.
obtained with other precursors {26% from the hydride 5
These observations allowed, inter alia, the proposal of a
binuclear platinum() dihydride [Pt(dppp)(H)]2 [1H NMR in
CD2Cl2 (hydrido region): δ ϭ Ϫ1.5 (quintet with 1:8:18:8:1
2ϩ
and from [Pt(dppe)(µ-OH)]2
,
and 30% from
[Pt(dppe)(Hdmpz)2]2ϩ},[12b] which in turn require at least
two other synthetic steps from [Pt(dppe)Cl2]. On the other
hand, the isolation of the cis-[Pt(dppe)(H)2] is ruled out by
its well established instability, even though its formation
during the one-pot reaction is suggested by the occasional
1
2
satellites, JPtϪH ϭ 529, JPϪH ϭ 39 Hz) ppm; 31P{1H}
1
2
NMR (CD2Cl2): δ ϭ 19.2, JP,Pt ϭ 2420, JP,Pt ϭ 318,
JPϪP ϭ 37 Hz] as a by-product in the crude mixtures iso-
lated in the attempts to synthesise cation 3 directly from
Pt(dppp)Cl2.
1
presence in the H NMR spectra of a complex multiplet
2
[hydrido region in (CD3)2CO: δ ഠ Ϫ3.6, JPϪH ഠ 168 and
Compounds 1a, 1b, or 1c do not react with excess
NaBH4, unlike 5, which gave rise to the trinuclear cation 6
[Pt3(dppe)3(H)3]ϩ. We observe that these trinuclear hydrides
are not known with diphosphanyl ligands that stabilise
mononuclear cis-dihydrides in respect to Pt0 species (i.e.,
with dppp, dppb, dtbpe, dtbpp, dippp, and dcype ligands).
Compounds 1a, 1b, and 1d react with CO to give the
corresponding µ-hydrido µ-carbonyl platinum() derivatives
[Pt2(dcype)2(µ-H)(µ-CO)][X] (X ϭ Cl, 7a; BF4, 7b; BPh4,
7c), isolated as blue-green powders. The reactions, carried
out as reported previously for the analogous species with
various diphosphanyl ligands,[4e,13] seem to be dependent
on the counter-ions: species 7b and 7c are in fact obtained
nearly quantitatively, while the yields of 7a are lower, due
to the formation of minor by-products often including
[Pt(dcype)Cl2].
1
10 Hz] with satellites (1:4:1; JPtϪH ഠ 880 Hz).
All the compounds 1Ϫ8 reported here have been ident-
ified by analytical and spectroscopic data, while the solid-
state structure of complex 1d has been established by single-
crystal X-ray diffraction at 200 K.
The spectroscopic data for cation 1 are consistent with
those reported for the analogous hydrides and are not sig-
nificantly affected by the nature of the counter-ions.
The IR spectra show a strong and broad νPtϪH vibration
at 1980 cmϪ1 (in CH2Cl2), not observed in the correspond-
ing deuterides and thus attributable to terminal PtϪH
bonds.
The 1H, 31P{1H}, and 195Pt NMR spectra confirm
fluxional behaviour, not frozen at least down to 183 K. The
hydrido resonance appears as a typical quintet with four
satellites (intensity ratios: 1:8:18:8:1) indicating the mag-
netic equivalence of the four phosphorus and two plati-
num atoms.
Consistently, the 195Pt{1H} NMR spectra show the res-
onance of the most abundant isotopomer (195Pt-Pt: 44.8%)
as a triplet of triplets. In the 195Pt{31P} spectrum the central
resonance is split into a quadruplet, giving unequivocal evi-
dence for the number of hydrido ligands.
Their spectroscopic features (IR and NMR spectra) are
reminiscent of those observed for the homologous com-
plexes with different diphosphanes either of platinum[4e,13]
or of palladium.[14] The IR spectra show the strong absorp-
tion due to the bridging carbonyl group at about 1710
cmϪ1. Slight differences are observed with the different
anions.
1
In the H NMR spectra (300 MHz), the main resonance
of the hydride (δ ഠ ϩ0.7) and of the diphosphanyl ligand
This determination is obviously a crucial point for the resonances overlap, so that only the two external satellites
correct assignment of a new compound to the appropriate of the hydrido ligand (1JHϪPt ϭ 984 Hz) are observed. Their
family of the different binuclear hydrides, namely the 30 multiplicity (up to 323 K) is intermediate between the pre-
eϪ species {[Pt(P-P)(H)]2 or [Pt2(P-P)2(H)3]ϩ} or the 28 eϪ viously reported limiting spectra,[13] a quintet (fast ex-
derivatives {[Pt(P-P)(H)]22ϩ}. As these compounds are change region) and a triplet of triplets (frozen), suggesting
often formulated on the basis of spectroscopic data in solu- that the exchange process is slower in this case. Variable
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967
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A. L. Bandini, G. Banditelli, M. Manassero, A. Albinati, D. Colognesi, J. Eckert
Table 1. Relevant IR and NMR data for selected diphosphanyl platinum hydrides
FULL PAPER
Compound
lH[a]
31P{1H}[a]
IR
Ref.
Hydrido region[b]
δ
lJHϪPt 2JHϪP
δ
lJPϪPt 2J
3JP,P JPtϪPt νPtϪH
PϪPt
[Pt(P-P)H]2
dcype[c] [d]
dippe[c][e]
dtbpe[c][f]
dppe[g]
[5a]
[5a]
[5a]
[4c]
0.49
0.49
512
516
570
564
40
40
42
42
92.8
2180
2210
3112
2201
420
410
362
388
44
45
47
44
1965, 1937
105.5
119.9
70.9
1939, 1926
1975, 1931
not isolated
0.05
0.30[h]
1902
2ϩ [i]
[Pt(P-P)H]2
dcype
[6]
[6]
[6]
n.r.[j]
1.72[k]
0.12
n.r.[j]
786
767
n.r.[j]
96
119
61
2758
2880
2861
134
139
133
26
1644
1631
1629
[k]
dtbpe
dtbpp
35
1280
1820
31
20[l]
[Pt2(P-P)2(H)3]ϩ [m]
dcype
dtbpe
dtbpp
dppe
Ϫ2.77
Ϫ3.85
Ϫ5.89
Ϫ2.8
480
443
396
500
458
38
40
38
41
40
84.0
108.7
49.4
57.2
9.0
2803
2946
3039
2925
2913
150
161
168
171
172
8.1
7.9
6.8
9.8
7.3
801
815
840
793
1980 s,br[n]
2000, 1650
2045, 1650
2000 w,br
2020 m,br
this work
[4a]
[4a]
[4b]
[4b]
dppp
Ϫ3.7
[12]
[Pt3(dppe)3(H)3]ϩ
Ϫ1.6
387
29
57.8
2837
108
17.7
2010 s
[a] At ambient temperature unless otherwise stated; J in Hz. [b] always observed as quintets with satellites. [c] In C6D6. [d] Frozen at 237 K.
[e]
[f]
[g]
[h]
[i]
[j]
[k]
Frozen at 219 K. Fluxional at 183 K. In [D8]THF. At 213 K. In CD2Cl2. Not reported. Triplet of triplets: 2JHϪPtrans ϭ
2
[l]
[m]
[n]
73; JHϪPcis ϭ 7. Reported as mean value.
In CDCl3. In CH2Cl2.
temperature 31P{1H} NMR spectra (121.5 MHz) show a
broad singlet with satellites at 323 K, which is split at room
temperature. The dynamic behaviour of compounds 7aϪc
seems to be frozen at ca. 223 K, allowing the full set of
coupling constants for the hydrido resonance and for the
two couples of equivalent P nuclei to be evaluated.
˚
Table 2. Selected bond lengths [A] and angles [°] for cation 1d
(e.s.d.s in parentheses)
Pt(1)ϪPt(2)
Pt(1)ϪP(2)
Pt(1)ϪHb
Pt(2)ϪP(4)
Pt(2)ϪHb
2.696(1)
2.223(1)
1.69(3)
2.227(1)
1.75(2)
Pt(1)ϪP(l)
2.281(1)
1.63(2)
2.277(1)
1.61(2)
Pt(1)ϪHt(1)
Pt(2)ϪP(3)
Pt(2)ϪHt(2)
X-ray Crystal Structure of Compound 1d
Pt(2)ϪPt(1)ϪP(1)
P(1)ϪPt(1)ϪP(2)
117.2(1)
88.4(1)
91.5(9)
166.5(9)
116.3(1)
88.2(1)
89.7(8)
171(1)
Pt(2)ϪPt(1)ϪP(2)
P(1)ϪPt(1)ϪHt(1)
P(2)ϪPt(1)ϪHt(1)
Ht(1)ϪPt(1)ϪHb
Pt(1)ϪPt(2)ϪP(4)
P(3)ϪPt(2)ϪHt(2)
P(4)ϪPt(2)ϪHt(2)
Ht(2) ϪPt(2)ϪHb
149.5(1)
176.7(8)
88.5(8)
92(1)
149.7(1)
177.6(9)
90.2(8)
92(1)
The structure of compound 1d consists of packing of
Ϫ
[Pt2(dcype)2(H)3]ϩ cations and BPh4 anions in the molar P(1)ϪPt(1)ϪHb
P(2)ϪPt(1)ϪHb
ratio of 1:1 with normal van der Waals contacts. An OR-
Pt(1)ϪPt(2)ϪP(3)
TEP view of the cation is shown in Figure 1, while selected
P(3)ϪPt(2)ϪP(4)
interatomic distances and angles are listed in Table 2. The
P(3)ϪPt(2)ϪHb
P(4)ϪPt(2)ϪHb
cation consists of two five-membered rings, each made up
of a Pt atom and a chelating dcype ligand, separated by a
˚
Pt-Pt distance of 2.696(1) A, which is the shortest value
observed in these trihydrido cations but similar to that re-
ported in the case of the doubly hydrido bridged 28eϪ spec-
2ϩ
[6]
˚
ies [Pt(dcypp)(H)]2 [PtϪPt ϭ 2.698(1) A]. The two Pt
atoms are also bonded to three hydride ligands, one bridg-
ing the PtϪPt vector, and two terminally bonded, one for
each metal atom.
The dihedral angle between the Pt1ϪP1ϪP2 and
Pt2ϪP3ϪP4 planes is 82.74(1)°, in agreement with the
‘‘overall conformation’’ detected in homologous cations. At
variance with this, the same dihedral angle ranges from
‘‘90° to 180° conformations’’ in the reported structures of
the dihydrido platinum species,[5,6] either neutral PtI com-
plexes [Pt(P-P)(H)]2 or 28 eϪ platinum() cations [Pt(P-
P)(H)]22ϩ, in which the geometry around each platinum
centre was assumed to be square-planar as in cation 1. The
Figure 1. ORTEP view of the inner core of cation 1,
[Pt2(dcype)2(H)3]ϩ; ellipsoids are drawn at 30% probability level
3962
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Eur. J. Inorg. Chem. 2003, 3958Ϫ3967

Binuclear Hydridoplatinum()
FULL PAPER
[5b]
accommodation of the third hydride in the Pt2(P-P)2(H)2 polymorphic platinum() hydride [Pt(dfepe)H]2
core may be responsible for the ‘‘90° conformation’’ which to occur at very low energy, also in the solid state.
appears as a typical feature of these platinum() 30 eϪ cat-
observed
ions.
Incoherent Inelastic Neutron Spectroscopy (INS)
Bond lengths and angles involving the Pt atoms in the of 1a and 5a
current cation can be compared with those found in cation
[Pt2(butaphos)2(H)3]ϩ (10).[4g] Cation 10 differs from the
present one only in the substitution of the two dcype li-
gands with two butaphos ones. In both cations the overall
coordination around the Pt atom, if the PtϪPt bond is neg-
lected, can be described as distorted square planar, and the
idealised symmetry of the two cations is C2, with the two-
fold axis passing through the bridging hydride ligand and
the midpoint of the PtϪPt vector. The PtϪP distances are
As the structures of [Pt2(dcype)2(H)3][BF4] (1a) and
[Pt2(dppe)2(H)3][BF4] (5a) have been shown by diffraction
methods (X-ray and neutron for 1a and 5a,[4c,8] respectively)
to be different, we have carried out an INS spectroscopic
study of these complexes to obtain additional information
on the nature of the PtϪH interactions.
˚
of two kinds: two shorter [Pt1ϪP2 2.223(1) vs. 2.222(3) A
in 10, and Pt2ϪP4 2.227(1) vs. 2.217(3) in 10], and two
˚
longer [Pt1ϪP1 2.281(1) vs. 2.324(3) A in 10, and Pt2ϪP3
˚
2.277(1) vs. 2.309(3) A in 10]. The longer bonds are ap-
While the vibrational modes of bridging hydrides can be
investigated by optical spectroscopy,[16] this is in general
rather difficult because of severe line broadening and inter-
ference from other modes. Instead, INS has the major ad-
vantage that the incoherent neutron scattering cross section
for hydrogen is much larger than that for all other atomic
species and that modes involving H atoms therefore domi-
nate the INS spectra. To distinguish the vibrational modes
of the hydrides from those of the hydrogens in the ligands
unambiguously, however, a ‘‘sample difference’’[17] tech-
nique has been used (see Exp. Sect.).
The INS difference spectra of 5a and of 1a are shown in
Figures 2 and 3, respectively. As can be seen, the two spec-
tra are quite different, reflecting the different coordination
of the two ‘‘Pt2H3’’ moieties.
Although a complete assignment of the vibrational
modes would require a normal coordinates analysis, a
qualitative assignment of the main spectral features may
still be carried out on the basis of published data for similar
binuclear complexes[18] and other metal hydrides.[16,19] We
note that the stretching frequency for a terminal ‘‘PtϪH’’
group is to be expected in the 1900Ϫ2100 cmϪ1 region,
proximately trans to the terminal hydrides, displaying the
expected trans influence. We also note that the Pt1ϪP1 and
Pt2ϪP3 bonds are significantly longer in 10, possibly due to
the different steric requirements of the butaphos and dcype
ligands and the formation of seven vs. five-membered met-
allacycles, respectively.
Whereas in 10 only two hydride atoms had been detected
in the final Fourier maps, and the third was placed in its
position on the basis of symmetry considerations, in the
current cation the three hydrides have been found in the
final Fourier maps and included in the refinement with iso-
tropic thermal parameters, thus confirming the stereochem-
istry suggested for 10.[4g] The current structure is the first
X-ray determination of a complex of the type [Pt2(P-
P)2(H)x]nϩ (x ϭ 2, n ϭ 0, 2; x ϭ 3, n ϭ 1) in which all the
hydride ligands have been experimentally located, and the
resulting bond parameters are consistent with those re-
ported in the more precise neutron diffraction structure of
the cation [Pt2(dppe)2(H)3]ϩ.[8,15]
It was previously suggested that the geometry of the
Pt2(P-P)2(H)3 cores is controlled by the steric bulk of the
phosphorus substituents,[4f] rather than by the bite angle of
the chelating diphosphane. This view is supported by the
current structure if comparison is made with the analogous
cation with dppe: different structures are indeed observed
with two diphosphanes with different steric bulk but similar
bite angles. On the other hand, the same structure was re-
ported for cations with diphosphanes displaying the same
bite angle but different substituents (as in 10 or with
dtbpp).[4b,4g] The available X-ray structure determinations
therefore suggest that no conclusive statement can be made
on this point, and that misleading conclusions may be
drawn by use of comparison criteria focused only on these
ligand features. As previously emphasised,[4c] the fluxional
behaviour in solution suggests a very soft energy surface
producing different core conformations, so that even appar-
ently weak forces, such as crystal packing forces, could well
be responsible for structural differences involving small en-
ergy changes. In this connection, it is worth noting the sig-
Figure 2. INS difference spectrum for compound 5a; the line is
nificant change, from a 90° to a 180° conformation, in the drawn only as a guide for the eye
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967
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3963

A. L. Bandini, G. Banditelli, M. Manassero, A. Albinati, D. Colognesi, J. Eckert
FULL PAPER
A more complex pattern than in 5a is found in the
1200Ϫ1600 cmϪ1 region. The νs mode is at 1080 cmϪ1
,
while the νas bands are at 1240 cmϪ1 and 1340 cmϪ1. These
two bands are consistent with two slightly different environ-
ments around the two Pt atoms. Moreover, the new band at
1420 cmϪ1 may be connected with the presence of a single
bridging hydride and thus a less rigid metal framework. To
help with this assignment we have carried out a DFT calcu-
lation[22] on the model compound [(PMe3)2HPt(µϪH)-
PtH(PMe3)2]ϩ and have found a mode at 1490 cmϪ1 corre-
sponding to a combination of the νs(µϪH) and the out of
plane bending of both terminal hydrides, a vibrational
mode not possible when the platinum atoms are bridged by
two hydrides.
These results, as also observed previously,[18] show that
coupling between stretching and bending modes may be im-
portant in these bridging hydrides.
Figure 3. INS difference spectrum for compound 1a; the line is
drawn only as a guide for the eye
Experimental Section
while the modes involving the µ-bridging H may be de-
scribed in terms of a symmetric (νs) and anti-symmetric
(νas) MϪHϪM stretching modes (1000Ϫ1400 cmϪ1) as well
Evaporation was always carried out under reduced pressure. The
analytical samples were pumped to constant weight (room tem-
perature, ca 0.1 Torr). Elemental analyses were performed by the
Analytical Laboratory of the University of Milan and the Mi-
kroanalytisches Labor Pascher (Remagen-Bandorf).
as skeletal deformations and torsions (i.e., δPMH and δMHM
)
at lower frequencies.[18Ϫ20] As the intensities of the INS
bands depend on the displacements of the H ligands, one
would expect that the intensities of the deformation and
torsional modes should be greater than those of the stretch-
ing modes, if coupling between the modes is small. These
qualitative criteria allow for a relative straightforward as-
signment of the principal bands.
The infrared spectra were recorded on a Jasco FT/IR 420 spec-
trometer. NMR spectra were recorded at ambient temperature in
CDCl3 solutions unless otherwise stated, on a Bruker DRX 300
Avance spectrometer operating at 300 (1H), 121.5 (31P), and
64.5 MHz (195Pt), respectively. The shift values are given in ppm
from the usual standards; δ ϭ 195Pt is referred to Na2[PtCl6] aque-
ous solution. Abbreviations used in the description of NMR spec-
troscopic data are as follows: br., broad; s., singlet; d., doublet; t.,
triplet; q., quintet; m., multiplet.
Thus, in the difference spectrum of 5a, we assign the
band at 2080 cmϪ1 to the PtϪH stretch (based on the corre-
spondence with the IR broad band at ca. 2000 cmϪ1), the
1170 cmϪ1 band to the νas and that at 1010 cmϪ1 to the νs
mode of the ‘‘Pt(µ-H)Pt’’ moiety. The very intense bands at
750 cmϪ1 correspond to the δMHM mode of the same moi-
ety.
Solvents (RPE grade; Carlo Erba) were distilled prior to use.
NaBH4, NaBD4 and KBH4 were purchased from Merck, Aldrich
and Fluka, respectively. The diphosphanyl ligands were obtained
from Strem Chemicals and employed as received.
It is worth noting that it is possible to obtain structural
information on the MϪHϪM bridge from the νs/νas ratio.
Howard and co-workers[21] have in fact shown that, if the
metal framework may be regarded as rigid and the angle-
bending force constant is small, then the following relation
holds: νas/νs ϭ tan(θ/2), where θ is the MϪHϪM angle.
We have also shown[18] that the above equation also holds
accurately for compounds of the type [PR3LPt(µ-
H)PtLPR3] (L ϭ Ph, H; PR3 ϭ PMe3, PEt3).
The [Pt(P-P)Cl2][4d,23] from [Pt(COD)Cl2] and the cis-[Pt(P-P)-
(H)2][7] complexes were synthesised by literature methods.
Synthesis and Characterisation. [Pt(dcype)(µ-OH)]2[BF4]2 (2): The
products isolated by previously reported procedures[11] were mix-
tures of different p1atinum species with O-donors; compound 2
was always the most abundant product (NMR). Starting from
[Pt(dcype)Cl2] (636 mg, 0.92 mmol) and AgBF4 (360 mg,
1.9 mmol), the analytical sample was isolated as follows. After ac-
curate elimination of the insoluble AgCl, the crude reaction prod-
From the above assignment for 5a, a value of θ ϭ 98° is uct was crystallised from CH2Cl2/Et2O. A first crop was precipi-
tated by slow addition of diethyl ether to the dichloromethane solu-
tion; it was filtered off and then washed with acetone. Compound
2 was obtained as a residue (150 mg) slightly soluble in acetone. A
second fraction (40 mg) of the same compound was obtained from
the mother liquor by concentration in the presence of diethyl ether
obtained from this relationship, in very good agreement
with the average value of 97° for the PtϪHϪPt angle ob-
tained from single-crystal neutron diffraction.[8]
The difference spectrum of 1a clearly reflects a different
disposition of the H ligands around the Pt centres, as found
by X-ray diffraction. The PtϪH stretch is now at 2000 cmϪ1
[1970Ϫ1950 cmϪ1 in the IR (Nujol)], while the deformation
modes are at lower frequencies (560Ϫ620 cmϪ1), possibly
reflecting the different electron densities at the metal centres
due to the different basicity of the phosphanes.
and of a few drops of MeOH. Yield 30%. IR (nujol, cmϪ1): 3550
1
vbr. νOH, 1065 br. νBF4
.
31P{1H} NMR: δ ϭ 59.9 (s., JP,Pt
ϭ
3513 Hz) ppm. FAB MS (NBA): 1266 m/z [M Ϫ 2H]ϩ·. M.p. 235
°C (dec). C52H98B2F8O2P4Pt2 (1443.01): calcd. C 43.28, H 6.86, B
1.50, F 10.53, O 2.22, P 8.58, Pt 27.04; found C 43.32, H 7.10, F
9.93, P 8.4, Pt 26.7.
3964
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Eur. J. Inorg. Chem. 2003, 3958Ϫ3967

Binuclear Hydridoplatinum()
[Pt2(dcype)2(H)3][X] (X: BF4, 1a, Cl 1b; OH, 1c; BPh4, 1d): The (ppm): δ ϭ 83.9 (br. s, JP,Pt ϭ 2788, JP,Pt ϭ 149, JP,P ϭ not
FULL PAPER
1
2
3
salts 1a, 1b, and 1c were obtained from compound 2 (i), from
detectable, JPtϪPt ϭ 802 Hz).
[Pt(dcype)Cl2] (ii), or from cis-[Pt(dcype)(H)2][5a] (iii), respectively.
؊
Reactions of Pt(P-P)Cl2 (P-P ؍ dppe, dppp, dppb) with BH4
:
These reactions were attempted by procedure (ii) as reported above
for 1b, but under various experimental conditions [i.e., with or
without H2 atmosphere, with NaBH4 or KBH4, with use of differ-
ent BH4/Pt ratios (from 1:1 to 4:1), and at different temperatures
(from Ϫ15 °C to room temperature]. Even though the formation
of the [Pt2(P-P)2(H)3]ϩ cations was always observed, only the com-
pounds [Pt2(dppp)2(H)3][Cl] (3a) and [Pt3(dppe)3(H)3][Cl] (6) were
isolated as analytical samples.
(i) [Pt2(dcype)2(H)3][BF4] (1a): From [Pt(dcype)(µ-OH)]2[BF4]2 (2).
A suspension of KBH4 (7.5 mg. 0.14 mmol) in methanol (20 mL)
was added under dinitrogen atmosphere to a stirred solution of
compound 2 (172 mg, 0.12 mmol) in the same solvent (10 mL).
After ten minutes the colourless solution was evaporated to dryness
and the residue was extracted with CH2Cl2 (ca. 7 mL). The insol-
uble material was filtered off, and the white product (99 mg, yield
62%) was precipitated by addition of diethyl ether (ca. 20 mL) to
the clear solution. IR (nujol, cmϪ1): ν˜ ϭ 1970 s,br νPtH, 1050 s,br
νBF4. FAB MS: 1237 m/z [M]ϩ. M.p. 218 °C (dec.). C52H99BF4P4Pt2
(1325.22): calcd. C 47.14, H 7.54; found C 47.18, H 7.44.
The former product (3a) was isolated (yield 40%) by crystallisation
from acetone/diethyl ether of reaction products obtained by pro-
cedure (ii), but with use of a BH4/Pt ratio of 1:1.
(ii) [Pt2(dcype)2(H)3][Cl] (1b): From cis-[Pt(dcype)Cl2]. A solution
of NaBH4 (120.0 mg, 3.17 mmol) in ethanol (50 mL) was added
dropwise under dinitrogen atmosphere to a stirred solution of
[Pt(dcype)Cl2] (1.00 g, 1.45 mmol) in dichloromethane (70 mL).
After ten minutes, the turbid solution was evaporated to dryness
and the white solid residue was extracted with few millilitres (ca.
5) of CH2Cl2. The crude product (830 mg) was precipitated by ad-
dition of diethyl ether to the clear, filtered solution. The analytical
sample was obtained by crystallisation from CH2Cl2/Et2O (790 mg;
yield 85.6%). IR (nujol, cmϪ1): 1970Ϫ1950 s,br (1980 s,br in
CH2Cl2) νPtH. 1H NMR (ppm): δ ϭ 1.6Ϫ1.9 and 1.3Ϫ1.1 (m. unre-
With dppe ligand, under dihydrogen atmosphere but independently
of temperature and BH4/Pt ratio, the isolated powders were found
to be mixtures of unchanged Pt(dppe)Cl2 and variable amounts of
the binuclear (5) and trinuclear (6) hydrides. Compound 6 was iso-
lated as a pale yellow powder by slow addition of diethyl ether
to clear solutions of these mixtures in a few millilitres (4Ϫ5) of
dichloromethane. The best results (yield 63%) were obtained by
carrying out the reactions in ethanol/dichloromethane mixtures
(1:1), with use of a BH4/Pt ratio of 4:1, either at Ϫ15 °C or at room
temperature. The reaction times were 2 hours and 30 minutes,
respectively.
1
solved, CH2), δ ϭ Ϫ2.77 (q. with satellites, H, JHϪPt ϭ 480,
Reaction of 1 with CO and KCN. [Pt2(dcype)2(µ-CO)(µ-H)][X] (X:
Cl, 7a; BF4, 7b; BPh4, 7c): The compounds were synthesised by
bubbling CO through acetone solutions of the appropriate hydrido
salt at room temperature. The colourless solutions quickly turned
blue. The compounds were isolated by addition of diethyl ether to
the concentrated solutions at different reaction times: 30 minutes
(7a) or 4 hours (7b and 7c). Compounds 7b and 7c were isolated
as analytical samples (yields: 83% and 95%, respectively), while 7a
was crystallised from acetone/diethyl ether (yield 68%). IR (nujol,
cmϪ1): ν˜ ϭ 1710s νCO (1053 s,br, νBF4, 7b; 1579 m, BPh4, 7c).
31P{1H} NMR [(CD3)2CO, under CO atmosphere, ppm]: δ ϭ 64.3
2JHϪP ϭ 38 Hz). 31P{1H} (ppm): δ ϭ 84.0 (s., 1JP,Pt ϭ 2803, 2JP,Pt ϭ
3
1
150, JP,P ϭ 8.1, JPtϪPt ϭ 801 Hz); 195Pt{1H} and 195Pt{31P}
[(CD3)2CO, ppm]: δ ϭ Ϫ5141 tt. (1JPtϪP ϭ 2795; 2JPtϪP ϭ 148 Hz)
or quadruplet (1JPtϪH ഠ 480 Hz), respectively. M.p. 185 °C (dec.).
C52H99ClP4Pt2 (1273.87): calcd. C 49.04, H 7.85, Cl 2.79, P 9.74,
Pt 30.65; found C 48.82, H 7.87, Cl 2.90, P 9.52, Pt 31.0.
[Depending on the NaBH4 stock, indefinable salts of the binuclear
cation (NMR data), possibly with BxHy type anions (IR sugges-
tion), were isolated as white powders. By addition of a large excess
(400%) of a methanolic solution of NH4Cl to the reaction crude,
it is converted to 1b in few minutes (15Ј). This procedure is near
quantitative (yield 80% after crystallisation). Take care that
working with NaCl in acetone solution the major product was a
yellow oily, in which 4-hydroxy-4-methyl-2-pentanone was ident-
ified by GC.MS and 1H NMR data as the most abundant product.]
1
1
2
(br, JP,Pt ϭ 2260 Hz, Ptrans-C), δ ϭ 64.1 (br, JP,Pt ϭ 4390, JP,Pt
ϭ
460 Hz, Ptrans.H). 1H NMR [(CD3)2CO, under CO atmosphere, at
243 K, ppm]: δ ϭ ϩ0.72 (hydrido resonance; external satellites ob-
served as triplets of triplets: 1JHϪPt ϭ 454, JHϪPtrans ϭ 76, JHϪPcis ϭ
10 Hz). 31P{1H} NMR [(CD3)2CO, under CO atmosphere, at
1
2
223 K, ppm]: δ ϭ 65.8 (d, JP,Pt ϭ 2240, JP,P ϭ 26 Hz, PtransϪC),
1
2
2
(iii) [Pt2(dcype)2(H)3][OH] (1c): From cis-[Pt(dcype)(H)2]. A solu-
tion of cis-[Pt(dcype)(H)2] in methanol was stirred overnight under
dinitrogen atmosphere, and was then evaporated to dryness. The
white solid residue was dissolved in the minimum amount of
CH2Cl2, and compound 1c was precipitated by slow addition of
δ ϭ 65.0 (d, JP,Pt ϭ 4370, JP,Pt ϭ 470, JP,P ϭ 26 Hz, PtransϪH).
M.p. (dec) 200 °C, 7a; 215 °C, 7b; 190 °C, 7c. C53H97BF4OP4Pt2
(1351.21), 7b: ca1cd. C 47.14, H 7.25, found C 47.42, H 7.22.
cis-Pt(dcype)(H)(CN) (8):
A suspension of KCN (100 mg;
1.54 mmol) in methanol (20 mL) was added to a vigorously stirred
solution of 1b (400 mg, 0.314 mmol) in the same solvent (25 mL).
The solution immediately fizzed and a white precipitate was
formed. After ten minutes the suspension was evaporated to dry-
ness, the white residue was dissolved in CH2Cl2, and the insoluble
material was filtered off; this was repeated twice. The analytical
sample (300 mg; yield 75.3%) was obtained by addition of a large
excess of diethyl ether to few millilitres of a dichloromethane solu-
tion of the crude product. IR (nujol, cmϪl) 2118 vs νCN, 1992 vs
νPtH. 1H NMR (hydrido region, ppm): δ ϭ Ϫ2.01 (dd, 2JHϪPtrans ϭ
178.4, 2JHϪPcis ϭ 15; 1JHϪPt ϭ 986 Hz). 31P{1H} NMR (ppm): δ ϭ
diethyl ether (yield 95%). IR (nujol, cmϪ1): 3400Ϫ3200 vs,br νOH
,
1968 s,br νPtH. C52H100OP4Pt2 (1255.42): calcd. C 49.75, H 8.04;
found C 49.31, H 7.90.
The tetraphenylborate salt 1d was obtained variously from 1a, 1b,
or 1c by exchange reactions carried out in methanol solution with
a large excess of NaBPh4. The yields referred to analytical1y pure
samples were: 80% from 1a, 90% from 1b, and 84% from 1c. IR
(nujol, cmϪ1): ν˜ ϭ 1966br. s νPtH, 1580 m (BPh4Ϫ). M.p. 240 °C
(dec). C76H119BP4Pt2 (1557.68): ca1cd. C 58.62, H 7.72; found C
58.71, H 7.68.
1
1
71.8 (s, JP(transCN)ϪPt ϭ 2706 Hz), δ ϭ 69.0 (s, JP(transH)ϪPt
ϭ
[Pt2(dcype)2(D)3][Cl] (1b-d3): The deuteride was obtained by pro-
cedure (ii), but with use of NaBD4 and deuterated solvents. The
crude material was crystallised twice (yield 36%). 31P{1H} NMR
1714 Hz). 195Pt{1H} NMR [(CD3)2CO, ppm]: δ ϭ Ϫ5244 (dd).
FAB MS (NBA): 644 m/z [M]ϩ·. M.p.: 180 °C (dec). C27H49NP2Pt
(644.72): calcd. C 50.30, H 7.68, N 2.17; found C 49.93, H 7.70,
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. L. Bandini, G. Banditelli, M. Manassero, A. Albinati, D. Colognesi, J. Eckert
FULL PAPER
Table 3. Crystallographic data
Compound
persion corrections were taken from ref. 27. The structure was
solved by direct methods (SHELXS 86)[28] and refined by full-
matrix, least-squares, by using all reflections and minimising the
function Σw(F2o Ϫ kF2c)2. Anisotropic displacement factors were re-
1d
fined for all the non-hydrogen atoms. The three hydrides were
found in the final Fourier maps and refined isotropically. The other
hydrogen atoms were placed in their ideal positions (CϪH ϭ 0.97
Formula
M
Colour
C76H119BP4Pt2
1557.68
Colourless
Monoclinic
P21/n (no.14)
23.637(2)
13.328(1)
24.351(2)
90
109.17(1)
90
7246.0(11)
4
˚
Crystal system
Space group
A, B 1.10 times that of the carbon atom to which they are attached)
and not refined. In the final difference Fourier map the maximum
˚
a [A]
Ϫ3
˚
˚
residual was 1.06(14) A at 0.78 A from Pt(2). CCDC-208551 con-
tains the supplementary crystallographic data for this paper. These
data can be obtained free of charge at www.ccdc.cam.uk/conts/
retrieving.html or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (internat.)
ϩ44Ϫ1223/336-033; E-mail: deposit@ccdc.cam.ac.uk.
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
U [A ]
Z
Inelastic Incoherent Neutron Scattering (INS) Measurements: The
INS experiments were carried out on TOSCA-I, a crystal-analyser
inverse-geometry spectrometer[29] operating at the ISIS pulsed-neu-
tron source. The incident neutron beam spans a broad energy (E0)
range and energy selection is carried out on the secondary neutron
flight-path by use of the (002) Bragg reflection of a graphite ana-
lyser placed in back-scattering position (ഠ 136°). The resolving
F(000)
3184
1.43
200
Dc [g cmϪ3
T [K]
]
Crystal dimensions [mm]
0.25 ϫ 0.25 ϫ 0.40
40.23
0.76Ϫ1.00
ω
0.30
20
2450
5.00
3Ϫ25
µ (Mo-Kα) [cmϪ1
]
Min. and max. transmission factors
Scan mode
Frame width [°]
Time per frame [s]
No. of frames
DetectorϪsample distance [cm]
θ-range [°]
-
power of TOSCA-I is fairly good (2% Ͻ ∆h ω/E0 Ͻ 3.5%) in the
-
accessible energy transfer range (24 cmϪ1 Ͻ h ω Ͻ 8065 cmϪ1
)
making this instrument a neutron equivalent of a Raman optical
spectrometer. All the intramolecular vibrations can in principle be
easily observed by INS spectroscopy, but it should be also pointed
out that, due to molecular recoil, the neutron-measured frequencies
might be slightly different from those observed on a conventional
Raman spectrometer.
Reciprocal space explored
No. of reflections (total; independent)
Rint
full sphere
63529; 12751
0.038
Final R2 and R2w indices[a] (F2, all reflections) 0.029, 0.043
Conventional R1 index [I Ͼ 2σ(I)]
Reflections with I Ͼ 2σ(I)
No. of variables
0.018
10901
760
The measurements were carried out on samples of
[Pt2(dppe)2(H)3][BF4] (5a) and [Pt2(dcype)2(H)3][BF4] (1b) and their
deuterium analogues (approximately 1 g each), all contained in in-
dividual thin Al-film bags. During the data collection, the samples
were maintained at ca. 12 K and the spectra were recorded up to
an integrated proton current of 1967 µA/h (roughly 10 hours of
beam time).
Goodness of fit[b]
0.93
R2 ϭ [Σ(Fo2 Ϫ kFc )/ΣFo ], R2w ϭ [Σw(Fo2 Ϫ kFc ) /Σw(Fo ) ]
.
[a]
[b]
2
2
2 2
2 2 1/2
[Σw(Fo2 Ϫ kFc ) /(No Ϫ Nv)]1/2
, where w ϭ 4Fo /σ (Fo ) ,
2 2
2
2 2
σ(Fo ) ϭ [σ2(Fo ) ϩ (0.02Fo2)2]1/2, No is the number of observations
and Nv the number of variables.
2
2
In order to distinguish the MϪH vibrational modes from all other
vibrations involving hydrogen atoms of the ligands, a ‘‘sample dif-
ference’’ technique[17] was used. The method is based on the fact
that the incoherent neutron scattering cross sections of hydrogen
and deuterium are very different [79.91(4) and 2.94(3) barn, respec-
tively),[30] making vibrational modes involving D atoms difficult to
detect by INS in the presence of many hydrogen atoms. The differ-
ence between two experimental INS spectra (i.e., those containing
the ‘‘PtϪD’’ and ‘‘PtϪH’’ moieties) should thus only leave the
peaks involving the motion of the hydrides (bridging or terminal),
provided that any possible coupling of the hydride modes to other
molecular modes is negligible (on the scale of the resolution of the
INS experiment). Therefore, as the contribution from the ligand
modes is subtracted out, it is unnecessary to prepare samples with
fully deuterated ligands.
N 2.16. During the 195Pt{1H} NMR spectrum (CDCl3 solution)
acquisition, compound 8 was converted into [Pt(dcype)Cl2] and cis-
[Pt(dcype)(Cl)(CN)] (9): 31P{1H} NMR (ppm): δ ϭ 65.4 (s,
1
1JP(transCl)ϪPt ϭ 3337 Hz), δ ϭ 63.0 (s, JP(transCN)ϪPt ϭ 2568 Hz).
195Pt{1H} NMR (ppm): δ ϭ Ϫ4839 (dd).
X-ray Data Collection and Structure Determination: Crystal data
and other experimental details are summarised in Table 3. The dif-
fraction experiment was carried out on a Bruker SMART CCD
area-detector diffractometer at 200 K by use of Mo-Kα radiation
˚
(λ ϭ 0.71073 A) with a graphite crystal monochromator in the
incident beam. Cell parameters and orientation matrix were ob-
tained from least-squares refinement of 123 reflections each meas-
ured in three different sets of 15 frames, in the range 3 Ͻ θ Ͻ 23°.
At the end of data collection the first 50 frames, containing 235
reflections, were recollected to monitor crystal decay. No correction
was necessary. The collected frames were processed with the
SAINT software package,[24] and an absorption correction was ap-
plied (SADABS)[25] to the 63529 collected reflections, 12751 of
which are unique with Rint ϭ 0.0378 (Rint ϭ Σ|F2o Ϫ Fm2 ean|/ΣF2o).
Acknowledgments
A. A. and G. B. wish to thank the MIUR for financial support
(PRIN 2002). We also wish to thank Mr. P. Illiano for assistance
with the NMR experiments. Work at LANL was supported by the
Office of Science, U. S. Department of Energy.
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www.eurjic.org
Eur. J. Inorg. Chem. 2003, 3958Ϫ3967

Binuclear Hydridoplatinum()
FULL PAPER
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Received April 30, 2003
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3967