Preparation of buta-1,3-diynyl complexes of platinum(II) and their use in the construction of neutral molecular squares: Synthesis, structural and theoretical characterisation of cyclo-{Pt(μ-C≡CC≡C)(dppe)}4 and related chemistry

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Preparation of buta-1,3-diynyl complexes of platinum(II) and

their use in the construction of neutral molecular squares:

synthesis, structural and theoretical characterisation of

᎐

cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppe)} and related chemistry

᎐

4

Michael I. Bruce,^aKarine Costuas,^a,bJean-François Halet,^bBen C. Hall,^aPaul J. Low,^a,c

Brian K. Nicholson,^dBrian W. Skelton^eand Allan H. White^e

^aDepartment of Chemistry, University of Adelaide, Adelaide, South Australia 5005.

E-mail: michael.bruce@adelaide.edu.au

^bLaboratoire de Chimie du Solide et Inorganique Moléculaire, UMR 6511 CNRS,

Université de Rennes 1, Institut de Chimie de Rennes, Avenue du Général Leclerc,

35042 Rennes cedex, France

^cDepartment of Chemistry, University of Durham, South Road, Durham, UK DH1 3LE

^dDepartment of Chemistry, University of Waikato, Hamilton, New Zealand

^eDepartment of Chemistry, University of Western Australia, Crawley, Western Australia 6009

Received 3rd September 2001, Accepted 7th November 2001

First published as an Advance Article on the web 11th January 2002

Copper()-catalysed reactions of cis-PtCl₂(L)₂(L = PEt₃, L₂= dppe, dppp) with buta-1,3-diyne have given the

᎐

corresponding diynyl complexes, cis-Pt(C᎐CC᎐CH) (L) (L = PEt 1, L = dppe 2, dppp 3) whose solid-state

᎐

2

3

2

structures have been determined from single crystal X-ray diﬀraction studies. Theoretical calculations were carried

out to probe the electronic structure of these diynyl complexes. Complex 2 reacts with Co₂(CO)₈to give a bis-adduct

᎐

5 and with Ru₃(µ-dppm)(CO)₁₀to give a mono-adduct 6; in both, the least hindered C᎐C triple bond(s) is(are)

᎐

coordinated. Lithiation (LiBu^t) of 2 gives a dilithio derivative, which has been converted to dimethyl 7 or mono-

SiMe₃8 or -Au(PPh₃) 9 complexes. Cu() and Ag() (M^I) adducts (“tweezer” complexes) have been obtained from

reactions of 2 with M^ISCN or [M^I(NCMe)₄]^ϩ. An ES mass spectrometric study of the interactions of 2 with

Group 1 cations and with Tl^ϩis also described; comparative experiments with {W(CO)₃Cp}₂(µ-C₈), in which the

᎐

four C᎐C triple bonds do not have a “tweezer” conformation, have also been carried out. The degree of association

᎐

is determined by the competitive solvation of the Group 1 cation. Coupling of the buta-1,3-diynyl complexes with

᎐

Pt(OTf ) (LЈ) gives homo- or mixed-ligand molecular squares cyclo-{(L) Pt(µ-C᎐CC᎐C) Pt(LЈ) } (L, LЈ = PEt ,

᎐

2

3

᎐

L , LЈ = dppe, dppp; not all combinations), of which the molecular structure of cyclo-{Pt(µ-C᎐CC᎐C)(dppe)} 17

᎐

2

4

is described (as solvates containing dmso). The molecular squares form adducts with substituted ammonium

triﬂates [NH₂R₂][OTf] (R = Et, Prⁱ, Cy; NH₂R₂= dbuH) and with Group 11 cations [M^I(NCMe)]^ϩ.

platinum() complexes, according to the geometry of the start-

ing material. The bis(alkynyl)platinum sub-units subtend angles

of ca. 90 or 180Њ at the platinum, respectively. While the trans

isomers have long been used to make polymeric materials

containing platinum in the backbone,^4,5the cis isomers are

receiving increasing attention because of their ability to act as

“molecular tweezers”, whereby small metal–ligand fragments

can be stabilised within the bite of the two alkyne arms.⁶More

recently, a series of complexes containing long poly-yne chains

capped by PtR{P(tol)₃}₂fragments (R = tol, C₆F₅) have been

described.⁷

Introduction

The design and synthesis of molecules having speciﬁc 2D or 3D

architectures is of much current interest, such structures includ-

ing molecular rods, squares, hexagons and boxes.^1,2Assemblies

of molecular squares containing transition metals by supra-

molecular techniques were among the ﬁrst areas of success. As

edges, a variety of exo-bidentate ligands have been employed

including N-donor ligands such as 4,4Ј-bipyridyl or 2,7-diaza-

pyrene, and more recently 4-phenyl- or 4-ethynylpyridines and

4,4Ј-biphenyldiyl. Stang and coworkers have reported high yield

syntheses of complexes such as [{Pt(µ-4,4Ј-bpy)L₂}₄]^8ϩ(L =

In the last few years the synthesis and properties of many

buta-1,3-diyne-1,4-diyl complexes containing metals other than

platinum have been reported.^8–14These complexes have been

obtained either directly from buta-1,3-diyne, or from silylated

PEt₃, L₂= dppp), [{Pt(µ-C₆H₄CN-4)L₂}₄]^4ϩor [{Pt(µ-C᎐CC -

᎐

5

H₄N-4)L₂}₄]^{4ϩ 3}

.

The challenge of making similar molecules

having atomic chains as edges, such as the buta-1,3-diyne-1,4-

diyl (C₄) ligand, has aesthetic appeal as well as a practical

advantage, since the resulting complexes are neutral and may

enclose larger cavities than exist in molecules in which the edges

consist of aromatic or similar bulky groups. In order for 2D or

3D molecules to be built, the reactive metal sub-units need to

have two or more ligands which can enter into further reactions.

Some of the most extensively used metal systems of this type

are the square-planar platinum() bis(tertiary phosphine) com-

plexes, PtX₂L₂. Reactions of 1-alkynes with chloroplatinum()

precursors result in the formation of cis- or trans-bis(alkynyl)-

or stannylated derivatives of the diyne. Detailed studies have

9

᎐

been carried out on {MnI(dppe) } (µ-C᎐CC᎐C), {Re(NO)-

᎐

2

10

11

᎐

(PPh )Cp*} (µ-C᎐CC᎐C),

{Fe(dppe)Cp*} (µ-C᎐CC᎐C)

᎐

2

᎐

3

2

and {Ru(PPh )(PR )Cp} (µ-C᎐CC᎐C) (R = Ph, Me).¹²Hetero-

᎐

3

2

metallic complexes in which two diﬀerent metal centres are

linked by the unsaturated carbon chain are also known.^8b,c,15All

of the systems described so far have been one-dimensional.

We have brieﬂy described the ready synthesis of buta-1,3-

diynyl complexes of platinum() directly from buta-1,3-

diyne.^8b,cThis paper gives the full details of this chemistry,

DOI: 10.1039/b107929h

J. Chem. Soc., Dalton Trans., 2002, 383–398

This journal is © The Royal Society of Chemistry 2002

383

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᎐

Scheme 1 Complexes 5–9 were obtained from Pt(C᎐CC᎐CH)₂(dppe) and the indicated reagents.

᎐

describing the preparation and structural characterisation of

several molecular tweezers and their self-assembly with

appropriate cis-Pt(OTf )₂(L)₂(L = PEt₃, L₂= dppe, dppp) com-

plexes to give molecular squares. During these studies,

related chemistry was published by Tessier and Youngs and

their coworkers, including full structural characterisation of

a molecule with C₄PtC₄edges.¹⁶

spectra of the three complexes are similar, with addition of

alkali metal or silver() ions resulting in the formation of ion

aggregates [M ϩ MЈ]^ϩand [2M ϩ MЈ]^ϩ(MЈ = Na^ϩor Ag^ϩ) as

the only observable ions. These observations prompted a more

detailed study into the formation of the adduct ions, which is

discussed further below.

A similar reaction between PtCl₂(cod) and the diyne aﬀorded

an unstable brown material which was not fully characterised.

However, addition of one equivalent of dppe to the initial

reaction mixture aﬀorded a quantitative yield of 3, consistent

Results and discussion

᎐

with the intermediate formation of Pt(C᎐CC᎐CH) (cod) 4 and

᎐

2

Preparation of cis-bis(diynyl)platinum(II) compounds

subsequent replacement of the cod by the dppe ligand. This

method could prove useful in the preparation of further

examples not otherwise readily obtained.

As previously communicated,^8bthe complexes cis-PtCl₂(L)₂

react with buta-1,3-diyne in dmf–diethylamine solution in the

᎐

presence of CuI to give cis-Pt(C᎐CC᎐CH) (L) (L = PEt 1, L =

᎐

2

3

2

dppe 2, dppp 3; Scheme 1) in high yields. These white or pale

yellow complexes can be recrystallised from benzene–hexane or

CH₂Cl₂–hexane mixtures and their identities have been con-

ﬁrmed crystallographically. Their spectroscopic properties were

in accord with their solid-state structures. In the IR spectra of

᎐

Molecular structures of cis-Pt(C᎐CC᎐CH) (L) (L

؍

PEt 1,

L₂

؍

dppe 2, dppp 3)

᎐

2

3

Plots of a single molecule of each of the three complexes are

shown in Fig. 1–3 and important structural parameters are

1, bands at 3249 and 2147 cm^Ϫ1were assigned to ν(᎐CH) and

᎐

ν(C᎐C) absorptions respectively, while similar bands were

᎐

found at 3288 and 2147 cm^Ϫ1for 2 and at 3296 and 2151 cm^Ϫ1

for 3. In the ¹H NMR spectra, the acetylenic protons are found

at δ ca. 1.8 ppm and show coupling to the two chemically

equivalent but magnetically non-equivalent ³¹P nuclei. Other

signals are consistent with the phosphine substituents present,

with 1 showing signals arising from the ethyl groups at δ 1.08

(CH₃) and δ 1.97 (CH₂). Both 2 and 3 showed peaks corre-

sponding to the phenyl rings at δ ca. 7.30–7.90, and a multiplet

corresponding to the methylene protons of the phosphine

backbone at δ 2.42 or δ 2.70 ppm for 2 and 3, respectively. In the

¹³C NMR spectra, relatively weak signals were recorded for the

carbon chains at δ ca. 94, 80, 72 and 62. All signals were singlets

with no discernible coupling to Pt or P which precluded

assignments to particular carbon atoms. However, the lower

ﬁeld signals probably arise from C_γand C_δ(where C_α, C_β, ؒ ؒ ؒ ,

etc., denote the carbons of the C₄chain moving out from the Pt

centre). The ³¹P NMR spectra contained the usual apparent

triplets at δ 5.44 [J(PPt) = 2262 Hz] for 1, at δ 43.26 [J(PPt) =

2288 Hz] for 2 and at δ Ϫ6.69 [J(PPt) = 2204 Hz] for 3. These

coupling constants are consistent with the cis-orientation of the

two tertiary phosphine nuclei.¹⁷The electrospray (ES) mass

᎐

Fig. 1 Projection of cis-Pt(C᎐CC᎐CH)₂(PEt₃)₂(1), showing atom

᎐

numbering scheme.

384

J. Chem. Soc., Dalton Trans., 2002, 383–398

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Table 1 Selected bond parameters for butadiynyl–platinum complexes 1, 2 and 3

1

2

3

dcype¹⁶

Pt–C(1)

1.976(4)

1.218(6)

1.390(6)

1.174(7)

2.319(1)

—

2.20(1)

1.17(2)

1.36(2)

1.16(2)

2.269(3)

1.84(1)

1.49(2)

1.997, 2.002(9)

1.21, 1.18(1)

1.36, 1.37(1)

2.03(4), 2.06(2)

1.15, 1.17(2)

1.39, 1.37(3)

1.17, 1.19(3)

2.271(8), 2.278(5)

1.84, 1.83(2)

1.53(3)

C(1)–C(2)

C(2)–C(3)

C(3)–C(4)

Pt–P

P–C(0)

C(0)–C(0Ј)

1.17, 1.17(2)

2.304, 2.305(2)

1.83(1), 1.811(9)

1.52, 1.53(1)

—

C(1)–Pt–C(1Ј)

C(1)–Pt–P

P–Pt–PЈ

Pt–C(1)–C(2)

C(1)–C(2)–C(3)

C(2)–C(3)–C(4)

C(1)–Pt–P

Pt–P–C(0)

P–C(0)–C(0Ј)

[P]C(1)–C(2)–C(3)

86.5(2)

84.1(1)

105.22(4)

179.2(4)

179.8(5)

179.7(7)

170.7(1)

—

93.2(5)

90.5(3)

86.2(1)

171.7(9)

176(1)

88.9(3)

84.7, 89.7(3)

97.02(8)

175.2, 171.0(8)

173.6(9), 175(1)

178, 176(1)

176.8, 170.9(3)

117.7, 115.6(3)

114.0, 116.7(6)

112.2(7)

93.2(11)

88.4(9), 92.8(6)

86.3(2)

177(3), 175(2)

175, 179(2)

177, 179(2)

175.3(6), 170.6(10)

109.8(7), 108.6(6)

110.5(14), 113.6(12)

175(1)

173.7(3)

107.2(4)

110.0(8)

—

᎐

Fig. 2 Projection of Pt(C᎐CC᎐CH)₂(dppe) (2).

᎐

Fig. 3 Projection of Pt(C᎐CC᎐CH)₂(dppe) (3).

᎐

collected in Table 1. Some comparable bond parameters for

᎐

Pt(C᎐CC᎐CH) (dcype) [dcype

=

1,2-bis(dicyclohexylphos-

separations of 1.218, 1.390 and 1.174(6) Å (for 1), 1.17, 1.36

and 1.16(2) Å (for 2) and 1.21, 1.36, 1.17(1) Å (for 3) conﬁrm

retention of diynyl character along the C₄chain. The diynyl H

atoms were not reﬁned. In 1, angles at the carbon atoms of the

chain range between 179.2(4) and 179.7(7)Њ, i.e. the C₄chains

are linear within experimental error. In contrast, the C₄chains

are distinctly non-linear in 2 and 3 with the corresponding

angles ranging from 171.7(9) to 176(1)Њ (for 2) and 171.0(8) to

178(1)Њ (for 3); the largest departures from linearity are found at

atoms C(1) and C(2). In 3 the C(1)–Pt–C(1Ј) and P–Pt–PЈ

angles are 88.9(3) and 97.02(8)Њ, respectively, perhaps the

result of steric interactions between the phenyl groups of the

tertiary phosphine ligands and the C₄chains (but see also

the theoretical discussion below). The facile bending of C_n

chains has been recently noted and discussed in a series of

complexes containing longer C_nchains (n = 6–12) attached to

rhenium²¹or platinum.⁷In this context, it is of interest to note

the size of the anisotropic displacement parameters of C(4),

which are nearly twice those for the other three carbon atoms

of the chain. It is evident that deformation of the C₄chain is a

low energy process. Intramolecularly, we note that in 3

C(22) ؒ ؒ ؒ H(222) (2.6₂Å) is especially close, while Pt ؒ ؒ ؒ H(16)

᎐

2

phino)ethane] are also listed.¹⁶In 1, the molecule lies with the

metal on a site of mm symmetry, so that only one quarter,

containing half a ligand of each type, comprises the asym-

metric unit of the structure. In 2, the molecule is also disposed

thus, the axis passing through the mid-point of the central C–C

bond of the diphosphine ligand. Bond parameters are similar

for all complexes. The platinum atom has approximate square-

planar coordination, the bulk of the PEt₃ligands in 1 being

associated with expanded P–Pt–P angles (105.22(4)Њ), whereas

the angles subtended at Pt in the chelate complexes are depend-

ent on the bite-angles of the chelating phosphines. Thus, we

ﬁnd values for P(1)–Pt–P(2) of 86.2(1) and 97.02(8)Њ for 2 and 3

respectively. There are similar variations in the C–Pt–C angles

[86.5(2), 93.2(5) and 88.9(3)Њ for 1, 2 and 3 respectively] while

the P–Pt–C angles vary between 84.1(1) and 90.5(3)Њ.

The Pt–P distances are 2.319(1) 1, 2.269(3) 2 and 2.304,

2.305(2) Å 3, which may be compared with values of 2.220(8) Å

for PtCl₂(dppe)¹⁸and 2.233(1), 2.2317(8) Å for PtCl₂(dppp).¹⁹

The Pt–C distances are 1.976(4) 1, 2.02(1) 2 and 1.997, 2.002(9)

Å 3 [cf. Pt–C 2.10, 2.04(1) Å in cis-Pt(C᎐CPh) (PPh ) ²⁰]. Along

᎐

2

3 2

the C₄chain from the metal, alternate short and long C–C

J. Chem. Soc., Dalton Trans., 2002, 383–398

385

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(2.9₈Å) in 2 and Pt ؒ ؒ ؒ H(122, 212) (2.8₂, 3.0₅Å) in 3 may be

considered quasi-agostic.

FMOs 1a₁and 2b₁, respectively (see Fig. 4). This leads to an

important electron donation from the C₄H units towards the

metallic fragments as illustrated numerically by the braced

digits in Fig. 4 which indicate the electron occupation of FMOs

following the interaction of the component fragments.

Theoretical considerations

Compounds 1, 2 and 3 are typical 16-electron square-planar

ML₂LЈ₂complexes. Extended Hückel (EH) and Density Func-

tional (DF) molecular orbital calculations were carried out on

An interesting point to discuss is the additional interaction

of the π/π* orbitals of the C₄H ligands with the metal fragment.

The large energy diﬀerence between the donor metallic FMOs

and the four low-lying acceptor π* orbitals on the C₄H entities

limits the degree to which back-bonding interactions may con-

tribute to the M–C bonding in 2-H. The electron occupation of

the acceptor carbon orbitals is computed to be only between

0.01 and 0.09. It turns out that the major Pt–C π-type inter-

actions are ﬁlled/ﬁlled interactions between the occupied

carbon and metal π orbitals. Among the four π FMOs of the

C₄H ligands, three of them, the in-plane 2a₁, and the out-of-

plane 1b₂and 1a₂FMOs interact rather strongly with the

corresponding occupied metallic FMOs 1b₂, a₂and 1a₁. As a

result of these interactions, the C₄H π orbitals are stabilised,

whereas the metallic orbitals are somewhat destabilised and

become the HOMOs of 2-H. An important consequence of

these π-type interactions is the strong mixing of the C₄H and

Pt(dHpe) FMOs which leads to a large percentage contribution

from the carbon atoms of the C₄H unit to the HOMOs of 2-H

(54, 57 and 61% platinum and 46, 43 and 39% C₄H character

for the 3a₁, 2a₂and 2b₂MOs, respectively). The HOMOs are

therefore delocalised over the entire Pt(C₄H)₂core, being anti-

bonding between Pt and C(1) and between C(2) and C(3), but

bonding between C(1) and C(2) and between C(3) and C(4). It

may be concluded that any eventual oxidation process which

would involve loss of electrons from these HOMOs will aﬀect

the whole molecule. A large gap of 3.18 eV is computed

between the 3a₁HOMO and the 4a₁LUMO which nearly

exclusively derives from one C₄H π* component.

᎐

the hydrogen-substituted model complex Pt(C᎐CC᎐CH) -

᎐

2

(dHpe) (2-H) and derivatives in order to gain further insight

into the electronic structure of these 16-electron platinum()

diynyl species. Computational details are given in the Experi-

mental section.

A simple EH molecular orbital diagram (Fig. 4) is useful

These qualitative conclusions are further supported by

density functional molecular orbital calculations, which

᎐

were carried out on diﬀerent Pt(C᎐CC᎐CH) (L) species. For

᎐

2

instance, calculations on the geometry-optimised hydrogen-

᎐

substituted model complex Pt(C᎐CC᎐CH) (dHpp) (3-H)

᎐

2

shows a HOMO/LUMO gap of 3.07 eV with HOMOs largely

delocalised both on the metal centre and the diynyl chains. With

computed Pt–C distances of 1.977, 1.976 Å, Pt–P distances of

2.259 Å, C(1)–C(2), C(2)–C(3) and C(3)–C(4) separations of

1.231, 1.364 and 1.221 Å, respectively, and C–Pt–C and P–Pt–P

angles of 93.2Њ and 95.5Њ, respectively, the optimised geometry

of 3-H compares rather well with that of the crystallograph-

Fig.

4

᎐

EH orbital interaction diagram for the model complex

᎐

Pt(C᎐CC᎐CH)₂(dHpe) (2-H) of C_2vsymmetry. FMO occupancies after

᎐

interaction are given in brackets. For clarity the C₄H σ-type FMOs la₁

and 2b₁are not sketched.

᎐

ically characterised complex Pt(C᎐CC᎐CH) (dppp) (3) (see

᎐

2

Table 1). Interestingly enough, the PtCCCCH sequences are

not strictly linear but are slightly curved [Pt–C(1)–C(2) 172.6,

172.9, C(1)–C(2)–C(3) 176.6, 177.9, and C(2)–C(3)–C(4) 178.9,

177.9Њ]. Nevertheless the curvature is slightly greater in the

experimental complex 3 (see Table 1), suggesting that the

bending of the C₄chains implicates both electronic eﬀects

(correlated with geometrical parameters) and crystal packing

forces. It is noteworthy that the most bent carbon chains are

observed with the smallest bite P–Pt–PЈ angles (see Table 1).

EH Mulliken and DF Hirshfeld²³atomic net charges are the

following: Ϫ0.18, 0.09 for Pt, Ϫ0.41, 0.64, 0.21 for P, Ϫ0.19 for

C(1), Ϫ0.05, Ϫ0.07 for C(2), 0.06, Ϫ0.03 for C(3) and Ϫ0.23,

Ϫ0.11 for C(4). They indicate some ﬂow of electron density

from the phosphorus and, to a lesser extent, the metal atoms to

part of the carbon chains. It follows that a substantial amount

of negative charge resides on C(1) and to a lesser extent on

C(4), whereas C(2) and C(3) remain nearly neutral.

for qualitatively understanding the bonding between the C₄H

chains and the metallic fragment. Using a fragment analysis,

the formation of 2-H of C_2vsymmetry can be envisioned as the

result of the interaction of the frontier molecular orbitals

(FMO) associated with the two (C₄H)^Ϫunits with those of

the ML₂platinum fragment [Pt(dHpe)]^2ϩ. The charges on the

fragments have been arbitrarily chosen in such a way that

the number of electrons associated with the carbon atoms of

the C₄H fragments is consistent with the octet rule.

The non-conical C_2v[Pt(dHpe)]^2ϩmetal fragment possesses

four mainly d-based orbitals at low energy (1b₂, a₂, 1a₁, and

2a₁), separated from two high-lying hybrid orbitals, one radial

(3a₁) and one tangential (b₁), which point away from the dHpe

ligand. At higher energy lies a metal p orbital, 2b₂.²²Such a

fragment is set up to interact with the FMOs of the two (C₄H)^Ϫ

units, restoring the usual splitting pattern for a square-planar d⁸

ML₄complex. The FMOs of the two (C₄H)^Ϫunits consist of a

set of in-phase and out-of-phase combinations of σ, π and π*

carbon orbitals (see the right-hand side of Fig. 4). The Pt–C

bonding in 2-H is dominated by strong σ-type interactions

between the vacant hybrid metal orbitals 3a₁and b₁and the

in-phase and out-of-phase combinations of the C₄H σ-type

Reactions of 2 with Co₂(CO)₈or Co₂(ꢀ-dppm)(CO)₆

The cobalt complexes Co₂(CO)₈and Co₂(µ-dppm)(CO)₆have

been used as protecting groups for alkynes²⁴as well as to con-

ﬁrm the presence of extended C_nchains in poly-yne com-

386

J. Chem. Soc., Dalton Trans., 2002, 383–398

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plexes.²⁵Reactions between Co₂(CO)₈and Pt(C᎐CC᎐CH) -

᎐

Table 2 Selected bond parameters for Pt{C᎐CC₂H[Co₂(µ-dppm)-

᎐

2

(CO)₄]}₂(dppe) (5)

(dppe) resulted in the formation of many products in low yield,

none of which were satisfactorily characterised. However, reac-

tion of 2 with two equivalents of Co₂(µ-dppm)(CO)₆resulted in

Pt–P(01)

Pt–P(02)

Pt–C(11)

Pt–C(21)

C(11)–C(12)

C(12)–C(13)

C(13 )–C(14)

C(21)–C(22)

C(22)–C(23)

C(23)–C(24)

Co(11)–Co(12)

Co(21)–Co(22)

2.272(8)

2.251(8)

2.03(3)

2.01(3)

1.20(4)

1.43(4)

1.25(4)

1.22(4)

1.38(4)

1.32(3)

2.458(5)

2.472(5)

Co(11)–P(11)

Co(12)–P(12)

Co(22)–P(22)

Co(24)–P(22)

Co(11)–C(13)

Co(11)–C(14)

Co(12)–C(13)

Co(12)–C(14)

Co(21)–C(23)

Co(21)–C(24)

Co(22)–C(23)

Co(22)–C(24)

2.197(8)

2.215(8)

2.212(9)

2.217(8)

1.89(3)

1.87(3)

1.95(3)

1.91(3)

1.98(2)

2.02(3)

1.98(3)

2.02(3)

᎐

the formation of red Pt{C᎐CC H[Co (µ-dppm)(CO) ]} (dppe)

᎐

2

4

2

5 in 50% yield. Coordination of the Co₂fragments to both C₄

arms was established by IR, NMR and ES mass spectrometry

and conﬁrmed by a (relatively imprecise) single-crystal X-ray

structure determination. The IR spectrum contained three

Ϫ1

peaks at 2016 [ν(C᎐C)], 1990 and 1960 cm [ν(CO)]. The ³¹P

᎐

NMR spectrum has two resonances, a triplet at δ 34.96 [J(PPt)

= 2258 Hz] (dppe) and a singlet at δ 20.66 (dppm). The negative-

ion ES mass spectrum contained a molecular anion at m/z 1920,

which fragmented by successive loss of up to eight CO groups.

The positive-ion spectrum of a solution containing NaOMe has

a single peak at m/z 1943, corresponding to the [M ϩ Na]^ϩion.

A molecule of 5 is shown in Fig. 5, with the important bond

P(01)–Pt–P(02)

C(11)–Pt–C(21)

P(01)–Pt–C(11)

P(01)–Pt–C(21)

P(02)–Pt–C(11)

P(02)–Pt–C(21)

86.0(3)

90(1)

91.4(8)

176.1(7)

175.8(8)

92.2(8)

Pt–C(11)–C(12)

176(2)

173(3)

142(3)

173(2)

173(3)

144(3)

C(11)–C(12)–C(13)

C(12)–C(13)–C(14)

Pt–C(21)–C(22)

C(21)–C(22)–C(23)

C(22)–C(23)–C(24)

orange solution is formed which is assumed to contain the

᎐

dilithio intermediate Pt(C᎐CC᎐CLi) (dppe), since addition of

᎐

2

two equivalents of iodomethane resulted in the formation of

᎐

the dimethyl derivative Pt(C᎐CC᎐CMe) (dppe) 7 in 93% yield.

᎐

2

This compound was characterised by NMR and ES mass

spectrometry. The ¹H and ¹³C NMR spectra showed the

presence of equivalent Me groups (δ_H1.28, δ_C50.76). The ES

mass spectrum contained two peaks, the molecular ion at m/z

719 and [M ϩ Li]^ϩat m/z 726.

Treatment of the dilithio derivative with SiClMe₃resulted in

᎐

the formation of the monosilylated complex, Pt(C᎐CC᎐CH)-

᎐

(C᎐CC᎐CSiMe )(dppe) 8 (68%). The IR spectrum contained

᎐

3

two ν(C᎐C) bands at 2149 and 2089 cm^Ϫ1, while the ¹H and ¹³

C

᎐

NMR spectra both conﬁrmed the presence of the SiMe₃group

(δ_H0.07, δ_C1.30). Monoauration similarly occurs in the reac-

tion between the dilithio derivative and AuCl(PPh₃) to give

᎐

Pt(C᎐CC᎐CH){C᎐CC᎐C[Au(PPh )]}(dppe) 9 in 60% yield.

᎐

3

᎐

This was identiﬁed by IR [two ν(C᎐C) bands at 2140 and 2084

᎐

cm^Ϫ1] and H NMR spectrometry (δ 1.22 for ᎐CH ). Integration

1

᎐

of the aromatic region conﬁrmed that only one Au(PPh₃) group

was present. The ES mass spectrum contained M^ϩ(m/z 1149).

Complex 9 was also obtained by treating 2 with AuCl(PPh₃) in

the presence of CuCl as catalyst. Molecular modelling of

᎐

Pt{C᎐CC᎐C[Au(PPh )]} (dppe) showed no steric interactions

᎐

3

2

᎐

Fig. 5 Projection of Pt{C᎐CC₂H[Co₂(µ-dppm)(CO)₄]}₂(dppe) (5).

᎐

between phenyl groups and it is not yet apparent why only the

mono-substituted derivatives 8 and 9 could be isolated.

lengths and angles being summarised in Table 2. While detailed

comparisons with the structure of 2 are not warranted, the

cis-Bis(buta-1,3-diynyl)platinum(II) complexes as molecular

tweezers

structure determination clearly shows that the two Co₂moieties

᎐

are attached to the least sterically hindered C᎐C triple bonds of

᎐

Many examples of cis-bis(alkynyl)metal complexes acting

as chelating ligands (“molecular tweezers”) towards metal

fragments have been reported,⁶among which examples with

guest fragments M^IX (M^I= Cu, Ag) feature prominently.²⁸

When either CuSCN or AgSCN is added to 2, mono-adducts

each C₄arm. The usual bending back of the substituents on this

C₂unit is found.

Reaction of 2 with Ru₃(ꢀ-dppm)(CO)₁₀

In a manner analogous to the reactions of organic 1-alkynes²⁶

I

᎐

M (SCN){(HC᎐CC ) Pt(dppe)} (M = Cu 10, Ag 11, respect-

᎐

and other terminal diynyl complexes,²⁷facile oxidative addition

2

ively; Scheme 2) are formed in excellent yields. The silver deriv-

ative is light sensitive, decomposing rapidly under standard

laboratory ﬂuorescent lights. Evidence for their composition

was obtained from IR, NMR and mass spectrometry, together

with elemental analyses. The IR spectra of 10 and 11 showed

2

᎐

of 2 to Ru₃(µ-dppm)(CO)₁₀gave yellow Ru (µ-H){µ -η -C C᎐C-

᎐

3

2

᎐

[Pt(C᎐CC᎐CH)(dppe)]}(µ-dppm)(CO) 6 in high yield. The

᎐

7

composition was determined by microanalysis, NMR and ES

mass spectrometry and showed that only one Ru₃cluster is

present, presumably for steric reasons. A doublet hydride

resonance at δ Ϫ19.39 [J(HP) = 34 Hz] is similar to that found

ν(CN) at ca. 2155 cm^Ϫ1from the SCN group and ν(C᎐C) bands

᎐

at lower frequencies than that of 2 (2098 10 and 2093 cm^Ϫ111).

2

27

᎐

for Ru (µ-H){µ -η -C C᎐C[W(CO) Cp]}(µ-dppm)(CO) . The

᎐

This is in agreement with the back-bonding from the M^Icentre

to the alkyne. While the ¹H NMR spectrum showed little

change from that of 2, the ¹³C NMR spectrum showed a down-

ﬁeld shift of C_αand C_βas a result of their complexation. The ES

mass spectra were similar with M^ϩat m/z 755 for 10 and m/z 799

for 11. Also present were peaks corresponding to [2(2) ϩ M^I]^ϩ

at m/z 1446 (10) or 1491 (11). Presently no X-ray structural

3

2

3

7

negative ion ES mass spectrum of 6 with added NaOMe

contained [M ϩ OMe]^Ϫ(m/z 1607) and [M Ϫ H]^Ϫ(m/z 1575)

with further fragmentation occurring by loss of CO ligands.

Lithiation reactions

When 2 is treated with two equivalents of LiBu^tat Ϫ78 ЊC an

J. Chem. Soc., Dalton Trans., 2002, 383–398

387

View Article Online

ligands,^32–34by cryptands or by valinomycin.³⁵The use of metal

ions, particularly Ag^ϩ, to form ions from neutral species for

analysis by ES mass spectrometry is now well established for

substrates with π-electron density and for metal carbonyls.^36–39

The availability of complexes containing polyalkyne units

arranged in diﬀerent ways provided interesting substrates for

investigating possible interactions with metal ions, ES mass

spectrometry being used to screen varying combinations rapidly

and on a small scale. As noted, the ES mass spectrum of a

methanolic solution of 3 containing Ag^ϩions showed clean

peaks at m/z 813 and 1519, corresponding to [3 ϩ Ag]^ϩand

[2(3) ϩ Ag]^ϩ, respectively. Similar results were obtained in

EtOH, while in MeCN ions [3 ϩ Ag(MeCN)]^ϩdominated at

lower cone voltages, with increasing amounts of [3 ϩ Ag]^ϩas

the cone voltage was raised. When the same complex in MeOH

was treated with Li^ϩions, there was a strong ion corresponding

to [3 ϩ Li ϩ MeOH]^ϩ(m/z 744) and a weaker signal from [2(3)

ϩ Li]^ϩ(m/z 1418) at a cone voltage of 20 V. At 40 V, the ion [3 ϩ

Li]^ϩ(m/z 712) is dominant while at 80 V the ion at m/z 744

has vanished. The relative intensity of the m/z 1418 signal

remains roughly constant as the cone voltage changes. With

the larger cations Na^ϩ, K^ϩ, Rb^ϩ, Cs^ϩand Tl^ϩ(MЈ) the spectra

are simpler, giving mainly ions of the type [3 ϩ MЈ]^ϩ, with no

solvated equivalents even at low cone voltages, together with

weaker [2(3) ϩ MЈ]^ϩspecies.

To gauge the selectivity towards diﬀerent ions, a solution of 3

was treated with an equimolar mixture of the mono-charged

cations as their chlorides in MeOH solution. The resulting mass

spectrum recorded with a cone voltage of 30 V is shown in

Fig. 6, and shows selectivity in the order Cs^ϩ> Tl^ϩ> Rb^ϩ> K^ϩ

Scheme 2

information is available for either complex, but it is likely that

they have structures similar to those found for related com-

plexes²⁸in which the M^Icentre has approximate trigonal-planar

coordination from the two η²-alkyne groups and the η¹-SCN

ligand, although the M^I(C₂)₂Pt system is non-planar.

Addition of [M^I(NCMe)₄]BF₄to 2 similarly gives complexes

I

᎐

of composition [M (NCMe){(HC᎐CC ) Pt(dppe)}]BF (M =

᎐

2

4

Cu 12, Ag 13) in high yields. Their IR spectra are similar with

Ϫ1

᎐

ν(᎐CH) and ν(C᎐C) bands at 3255 and 2141 cm (for 12) and

᎐

3281 and 2139 cm^Ϫ1(for 13), both spectra also containing broad

ν(BF) absorptions at 1060 cm^Ϫ1. The ¹H NMR spectra showed

very little diﬀerence from that of 2 with the exception of signals

arising from the coordinated MeCN at δ 2.00. The ¹³C NMR

spectra showed a downﬁeld shift of the C_αand C_βresonances as

a result of attachment of the [M^I(NCMe)]^ϩfragment. The ES

mass spectra showed similar features with [2 ϩ M^I(NCMe)]^ϩat

m/z 796 for 12 and 840 for 13. Also present were peaks corre-

sponding to [2(2) ϩ M^I]^ϩat m/z 1446 (12) and 1491 (13).

While treatment of 12 with one equivalent of [Ag(NCMe)₄]^ϩ

resulted in the appearance of a peak corresponding to [3 ϩ

Ag]^ϩat m/z 799, there was no change observed in the spectrum

of a solution of 13 with [Cu(NCMe)₄]^ϩ. These qualitative

results indicate that the silver is more strongly held than the

copper and prompted us to attempt to obtain more information

concerning the formation of adducts of these molecular

tweezers with mono-positive cations of Groups 1 and 11. We

have carried out a survey of the ES mass spectra of solutions

containing these complexes with added cations.

᎐

Fig. 6 The ES mass spectrum of Pt(C᎐CC᎐CH)₂(dppe) (3) in MeOH

᎐

in the presence of equimolar concentrations of Li^ϩ, Na^ϩ, K^ϩ, Rb^ϩ, Cs^ϩ

and Tl^ϩions. Cone voltage was set at 30 V to minimise overlap of the

[M ϩ Li ϩ MeOH]^ϩsignal with that of [M ϩ K]^ϩ, both at m/z 744.

> Na^ϩ> Li^ϩ. At ﬁrst sight, this seems counter-intuitive since it

might have been expected that the more polarising cations

would form stronger adducts with the alkyne groups on the

metal complex. Taken in isolation, the stability of cation-π

Electrospray mass spectrometry of bis(diynyl)platinum(II)

complexes

It is now generally accepted that the technique of ES mass

spectrometry is a reliable way of determining which ionic

species are present in a solution, since the gentle ionisation

process transfers ions intact to the gas phase for analysis in

the mass spectrometer. As a consequence, several ES mass

spectrometry studies have investigated semi-quantitatively the

interaction of ions with complexing ligands.²⁹The area has

been reviewed³⁰and more recent examples include the relative

binding of Group 1 ions by cholic acid derivatives³¹and the

complexation of metal ions by crown ethers and related

interactions is normally found to lie in the order Li^ϩ> Na^ϩ

>

K^ϩ, etc.,³⁸the reverse of the trend found and illustrated in

Fig. 6. However the observed order in the present study is

understandable in terms of competition between the alkyne

groups and the solvent molecules for sites about the M^ϩions.

Li^ϩis strongly solvated by MeOH so the alkyne group would

compete poorly giving weak adducts, whereas for the larger

cations such as Cs^ϩ, the MeOH molecules would be more read-

ily displaced. Alternatively, it can be rationalised in terms of

hard–soft acid–base theory; the alkyne group is a soft base

388

J. Chem. Soc., Dalton Trans., 2002, 383–398

View Article Online

while MeOH is hard, so the adduct with 3 would be most

favoured for the softest acid, i.e. the larger cation. Not

unexpectedly, none of these Group 1 cations competes eﬀect-

ively with Ag^ϩfor adduct formation. Note that the observed

selectivity is not a size-based one related to a “tweezer” eﬀect,

since similar results were found for polyalkyne complexes where

no tweezer eﬀect is possible (see below).

In MeCN solutions containing the same mixture of cations, 3

gave a similar spectrum to that in Fig. 6 except that the relative

intensities of the Tl^ϩand Rb^ϩadducts were reversed and the

Li^ϩadduct was barely detectable, i.e. Cs^ϩ> Rb^ϩ> Tl^ϩ> K^ϩ>

Na^ϩӷ Li^ϩ≈ 0. These diﬀerences presumably reﬂect the

strengths of solvation of the cations in MeOH and MeCN,

respectively.

Adducts of 3 with more complex mono-charged cations can

also be obtained. Thus when a mixture of 3 and PhHg(OAc) in

MeOH was introduced to the mass spectrometer, a signal at m/z

984 appeared and was readily assigned to the [3 ϩ HgPh]^ϩ

ion. The use of [HgMe]^ϩto derivatise neutral nitrogen bases

has been reported previously,⁴⁰but we are not aware of other

examples involving an HgR^ϩ-π type complexation.

the distribution shown in Fig. 6 for 3, except that negligible

amounts of the Li^ϩadduct were formed for 15 in competition

with the other cations. This also suggests that the selectivity

arises through competition with solvation, rather than by a size-

dependent tweezer eﬀect. Of interest is the observation that the

spectrum of 15 in MeOH without added cations gave rise to

peaks assigned to M^ϩand [M Ϫ nCO]^ϩ(n = 1, 2, 3, 4, depending

on cone voltage) arising from oxidation to the radical cation

in the mass spectrometer. While this is not unknown for

electron-rich species, it is a relatively rare type of ionisation

under normal electrospray conditions,^36a,43,44and no similar

signals were found for 3.

In a separate competition experiment, MeOH solutions

containing equal amounts of 3 and 15 together with the Group

1 cations were examined to assess the relative ease of adduct

formation. With Cs^ϩ, the [3 ϩ Cs]^ϩsignal was about three times

as intense as that of [15 ϩ Cs]^ϩ, while for the other cations (Tl^ϩ,

Rb^ϩ, K^ϩ, Na^ϩand Li^ϩ) the adducts formed by 15 were barely

detectable relative to the very strong [3 ϩ MЈ]^ϩions. This shows

that the platinum complex with two orthogonal C₄H groups

attaches to the cations more strongly than the tungsten example

with a linear C₈unit. This may be due to a small tweezer eﬀect,

but other explanations such as the eﬀect of the more extended

delocalised π-cloud for the C₈ligand compared with those of

two shorter C₄H groups can also be proposed.

The general pattern that is found for these complexes is that

the strongest adducts form for the Group 11 cations Ag^ϩand

Cu^ϩ, as would be expected for complexes involving π-

interactions. With the Group 1 cations, where non-covalent

(electrostatic) forces are proposed, the most abundant adducts

are with the least strongly solvated cation Cs^ϩ, where the

weakly coordinating alkyne groups can most readily displace

solvent molecules. This also explains the lack of ions involving

association with multiply-charged ions where solvation by

MeOH would be even stronger. This is in direct contrast to the

ES mass spectral work referred to above where complexation

of the ions by crown ethers and other O- or N-donor ligands

is involved. Stronger adducts were formed with the more polar-

ising cations and 2^ϩcations gave identiﬁable adducts. The

similarity of results for tweezer-type substrates and linear ones

suggests that there is no size-related tweezer eﬀect with the

Group 1 cations.

More highly charged ions, such as Ba^2ϩ, Cd^2ϩ, Sn^2ϩ, Pb^2ϩor

Hg^2ϩ(added as their nitrates) do not give simple adducts with 3.

Presumably these more highly charged cations are too strongly

solvated to become attached to the alkyne groups of 3. Only

with added Cu^2ϩwere identiﬁable species recorded, but these

were of the type [3 ϩ Cu]^ϩand [2(3) ϩ Cu]^ϩ, arising from

in situ reduction of Cu() to Cu(). When 3 was treated with a

mixture of Cu^2ϩand 1,10-phenanthroline a very strong,

clean signal corresponding to [3 ϩ Cu(phen)]^ϩwas found at

m/z 949.

᎐

The ES mass spectra of Pt{C᎐CC᎐C[W(CO) Cp]} (dppe)

᎐

3

2

14,^8cobtained from solutions in MeCN containing formic acid,

contained an [M ϩ H]^ϩion at m/z 1357, while an ion at m/z

1342 is formulated as [2(14) ϩ 2H Ϫ CO]^2ϩ. The use of MeCN

solutions containing AgNO₃resulted in the formation of

doubly-charged aggregate ions with masses and isotopic

distributions consistent with the formulations [{14 ϩ Ag}₂ϩ

5MeCN]^2ϩ(m/z 1566) and [{14 ϩ Ag}₂]^2ϩ(m/z 1464). The

complex Pt{C᎐CC᎐C[W(CO) Cp]} (dppp) (≡ M^W) was also

8c

᎐

3

2

examined in MeOH and EtOH, although solubility was very

limited. This also provided [M^Wϩ MЈ]^ϩsignals for MЈ = Li^ϩ,

Na^ϩ, K^ϩand Cs^ϩ. More interestingly, with Ag^ϩions the dom-

inant signal at m/z 1478 could be assigned to a [{M^Wϩ Ag}₂]^2ϩ

It is also clear that in choosing cations for derivatising neutral

substrates for ES mass spectral studies, the nature of the sub-

strate directs the choice. Where the functional groups are hard,

with N or O donor atoms for example, then smaller cations

such as Li^ϩare preferred, while for soft functional groups,

especially those with π-electrons, softer cations such as Ag^ϩor

Cu^ϩrespond better.

species, since the interpeak spacing in the isotope pattern was

᎐

0.5 amu. In vitro, coordination of two C᎐C triple bonds of

᎐

alkynyl-metal complexes to Cu^ϩor Ag^ϩions has been found on

many occasions.⁴¹In the present case, similar structures can be

᎐

proposed in which C᎐C triple bonds from two molecules of the

᎐

complex eﬀectively sandwich the Group 11 cations, rather than

acting in the tweezer mode.

To determine whether 3, with its four C᎐C triple bonds, is

Construction of molecular squares

᎐

acting in a tweezer fashion, analogous experiments were carried

The availability of the cis-bis(buta-1,3-diyn-1-yl) complexes 1, 2

and 3, which could be considered to form the two edges and

corner of a square or rectangle suggested their incorporation

into square molecules. However, addition of 1, 2, or 3 to

PtCl₂(L)₂under copper()-catalysed coupling conditions

resulted in the formation of polymers, probably due to the rapid

rates of these reactions, while the reaction of Pt(OTf )₂(L)₂with

1, 2 or 3 in a methanol–dichloromethane mixture resulted in

rapid decomposition, probably as a result of the formation of

triﬂic acid as a by-product of the coupling reaction. However,

we were encouraged by the appearance of ions corresponding

to the molecular squares in the ES mass spectra of the reaction

mixtures. Accordingly, use of high dilution techniques in reac-

tions carried out in the presence of a weak base, such as sodium

acetate, resulted in the quantitative self-assembly of the molec-

42

᎐

out with the complex {W(CO) Cp} {µ-(C᎐C) } 15. This has

᎐

3

2

4

the same number of alkyne groups, but they are arranged in

linear fashion so that they cannot exert a tweezer eﬀect. The

results were similar. With Li^ϩions in MeOH, 15 gave signals

assigned to [15 ϩ Li]^ϩ, [15 ϩ Li ϩ MeOH]^ϩand [15 ϩ Li ϩ

2MeOH]^ϩat a cone voltage of 30 V, while Na^ϩgave the corre-

sponding [15 ϩ Na]^ϩtogether with a weak [15 ϩ Na ϩ

MeOH]^ϩ. The other cations Ag^ϩ, K^ϩ, Rb^ϩ, Cs^ϩand Tl^ϩgave

ions [15 ϩ cation]^ϩonly, with no solvated equivalents even at

low cone voltages. However, when [Cu(MeCN)₄][BF₄] was

added to a MeOH solution of 15, the major ion was [15 ϩ

Cu(MeCN)]^ϩ. These observations are entirely consistent with

competition of the cations between solvent and alkyne groups

discussed earlier.

᎐

When a solution of 15 was treated with the equimolar

mixture of cations, the relative intensities of the signals were

Cs^ϩ> Tl^ϩ> Rb^ϩ> K^ϩ> Na^ϩ> Li^ϩ≈ 0. This is very similar to

ular squares cyclo-{Pt(µ-C᎐CC᎐C)(L) } (Scheme 3), with little

᎐

2 4

᎐

decomposition or polymer formation. Isolation of the products

was achieved by evaporation to small volume, followed by

J. Chem. Soc., Dalton Trans., 2002, 383–398

389

View Article Online

addition of hexane. Cream precipitates were identiﬁed as cyclo-

A brief survey of the inclusion of substituted ammonium

᎐

{Pt(µ-C᎐CC᎐C)(PEt ) } 16, cyclo-{Pt(µ-C᎐CC᎐C)(dppe)} 17

triﬂates were undertaken by varying the amine used in the

preparation of the adduct of 19. The resulting products were

analysed by ES mass spectrometry. When NHEt₂was used, the

base peak corresponded to [M Ϫ OTf]^ϩ(m/z 1990), followed by

successive losses of up to three PEt₃ligands which could be

followed by MS/MS experiments. Similar results were seen with

NHCy₂and NHPrⁱ₂with [M Ϫ OTf]^ϩpeaks at m/z 2097 and

m/z 2017 respectively. Even with the bulky base dbu (dbu = 1,8-

diazabicyclo[5.4.0]undec-7-ene), the adduct gave [M Ϫ OTf]^ϩas

the major peak at m/z 2068. Interestingly, in all cases peaks were

also present corresponding to loss of a Pt(PEt₃)₂group, i.e.

apparent break-up of the square possibly by reductive elimin-

ation to form a triangular macrocycle. With the exception of

the peaks due to the inclusion of [NH₂Et₂][OTf], the NMR

spectra of the adducts 19, 20 and 21 vary little from those of the

“pure” molecular squares.

᎐

3

2

4

᎐

and cyclo-{Pt(µ-C᎐CC᎐C)(dppp)} 18 (Scheme 3).

᎐

4

We note that secondary amines have been used in the pioneer-

ing work of Stoddart and his group, as one component of

a “molecular meccano kit”, speciﬁcally the axle or thread of

a [2]pseudorotaxane.⁴⁵Non-covalent interactions between the

amine hydrogens and the oxygens of appropriate crown ethers

aﬀord the supramolecular array. In the present instance,

᎐

possible association of the amine hydrogens with the C᎐C triple

᎐

bonds, analogous to that found in the chloroform adducts of

46

47

᎐

{Au(PPh Fc)} (µ-C᎐C) or N(C H O) SiC᎐CC᎐CSiMe , for

᎐

2

4

3

example, may explain the strong attachments found here.

Further work is designed to resolve and study further this

problem.

Mixed-ligand molecular squares were also obtained by this

᎐

route, by using combinations of Pt(C᎐CC᎐CH)(L ) and

᎐

2

Pt(OTf )₂(LЈ₂) where L ≠ LЈ. In this way, the complexes

᎐

cyclo-Pt (µ-C᎐CC᎐C) (PEt ) (dppe) ؒ[NH Et ][OTf] 22, cyclo-

᎐

4

᎐

4

3

4

2

᎐

Pt (µ-C᎐CC᎐C) (PEt ) (dppp) ؒ[NH Et ][OTf] 23 and cyclo-

᎐

4

3

4

2

᎐

Pt (µ-C᎐CC᎐C) (dppe) (dppp) ؒ[NH Et ][OTf]

24

were

᎐

4

2

prepared in good yield and readily identiﬁed by NMR and ES

mass spectroscopy. Thus, the ¹H NMR spectrum of 22 showed

signals arising from the presence of the two diﬀerent phosphine

ligands, at δ 0.12 (Me) and 1.01 (CH₂) for PEt₃and δ 2.36 and

6.33–7.07 for dppe. The ³¹P NMR spectra contained two

triplets at δ 5.08 [J(PPt) = 2338 Hz] and 40.76 [J(PPt) = 2323

Hz] for the PEt₃and dppe ligands, respectively. The ES mass

spectrum contained a single peak at m/z 2314 assigned to [M Ϫ

OTf]^ϩ. Similarly, two triplets at δ Ϫ7.69 [J(PPt) = 2284 Hz] and

6.15 [J(PPt) = 2209 Hz] in the ³¹P NMR spectrum of 23 arise

from the dppp and PEt₃ligands, respectively. The ES mass

spectra contained [M Ϫ OTf]^ϩat m/z 2344. In the case of 24,

the ³¹P NMR spectrum contains triplet resonances from

dppp and dppe at δ Ϫ3.45 [J(PPt) = 3408 Hz] and 43.36

[J(PPt) = 2288 Hz], respectively. The ES mass spectrum

contains [M Ϫ OTf]^ϩat m/z 2665. No ions corresponding

to homo-ligand complexes are present in any of these

spectra.

We have not been able to obtain single crystals of any of the

substituted ammonium triﬂate adducts, 19–24, suitable for

X-ray studies, so we cannot say how the cation and anion are

accommodated by the square molecule. However, that the

cation is strongly attached to the neutral complex is shown by

its persistence towards extensive extraction with a variety of

polar solvents, although it can be removed by washing with

aqueous sodium acetate solution.

Scheme 3

The IR spectra of 16, 17 and 18 each contained a single

ν(C᎐C) absorption at ca. 2145 cm^Ϫ1, while the ¹H and ¹³C NMR

᎐

spectra contained signals appropriate for the various tertiary

phosphine ligands. Only in the case of 18 could the two chem-

ically distinct carbons of the C₄bridge be observed in the ¹³C

NMR spectrum, at δ 92.23 and 110.39, but neither J(CP) nor

J(CPt) could be resolved. The ³¹P NMR spectra each contained

triplet resonances [J(PPt) ca. 2200 Hz] consistent with the

presence of the mutually cis phosphine centres. The ES mass

spectra of 16, 17 and 18 gave clean peaks at m/z 1940 [16 ϩ

Na]^ϩ, 2698 [17 ϩ Cs]^ϩand 2643 [18 ϩ Na]^ϩafter addition of

the appropriate alkali metal ion.

When NHEt₂was used as the base, the adducts cyclo-{Pt-

᎐

(µ-C᎐CC᎐C)(PEt ) } ؒ[NH Et ][OTf] 19, cyclo-{Pt(µ-C᎐CC᎐C)-

᎐

3

2

4

2

᎐

(dppe)} ؒ[NH Et ][OTf] 20 and cyclo-{Pt(µ-C᎐CC᎐C)(dppp)} ؒ

᎐

4

2

4

[NH₂Et₂][OTf] 21 were obtained, the compositions being

assigned on the basis of elemental microanalyses and their IR,

NMR and mass spectra. The IR spectra of 19, 20 and 21 vary

little from those of the analogous compounds 16, 17 and 18,

but contained in addition the characteristic ν(SO) and ν(CF)

bands from the triﬂate anion at ca. 1030, 1225 and 1290 cm^Ϫ1

.

Moreover, in the NMR spectra, peaks corresponding to the

presence of [NH₂Et₂]^ϩcations were seen at δ 0.8–1.44 and δ_C

10.93–11.18 for NH₂(CH₂CH₃)₂and δ_H2.64–3.07 and δ_C41.41–

41.94 for NH₂(CH₂CH₃)₂. The ES mass spectrum of 20 in dmso

contained a single ion at m/z 2640 corresponding to [M Ϫ

OTf]^ϩ. MS/MS experiments on this peak showed the formation

of the two daughter ions [M Ϫ NH₂Et₂OTf]^ϩ(m/z 2566) and

[M Ϫ NH₂Et₂OTf Ϫ dppe]^ϩ(m/z 2242). The spectrum of 21 in

CH₂Cl₂–MeOH showed a single peak at m/z 2696 assigned to

[M Ϫ OTf]^ϩ.

᎐

Molecular structure of cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppe)} 17

᎐

4

These molecular squares crystallise with some reluctance. How-

ever, using a sample of 17 prepared using NaOAc as base, we

obtained single crystals from aqueous dmso on two diﬀerent

occasions as diﬀerent phases, modelled as 10dmso and as

4.5dmsoؒH₂O solvates. The following description and discus-

sion are conducted in terms of the former, being representative

390

J. Chem. Soc., Dalton Trans., 2002, 383–398

View Article Online

᎐

Table

3

Selected bond parameters for molecular square cyclo-

in contrast with the situation for cyclo-{Pt(µ-C᎐CC᎐C)(dppp)}

᎐

4

᎐

{Pt(C᎐CC᎐C)(dppe)}₄(17)

᎐

18 in which molecular modelling suggests that signiﬁcant strain

occurs as a result of the proximity of the phenyl rings on

adjacent dppp ligands, which are oriented towards each other

as a result of the longer (CH₂)₃backbone. In contrast we note

that with more bulky edges, the use of dppp has been preferred,

because of the tendency for π-stacking to occur between the

phenyl groups of the dppp ligand and the aromatic rings of the

spacer groups.^1a

The unit cells of 17 contain additional dmso (and water)

molecules. In both phases, the solvent molecules lie about the

centre of the square and, more prominently in the deca-solvate,

along the edges as well.

Pt(1)–P(11)

Pt(1)–P(12)

Pt(2)–P(21)

Pt(2)–P(22)

Pt(1)–C(11)

Pt(1)–C(24)

Pt(2)–C(14)

Pt(2)–C(21)

2.279(4)

2.295(2)

2.282(2)

2.285(4)

2.027(8)

2.00(1)

C(11)–C(12)

C(12)–C(13)

C(13)–C(14)

C(21)–C(22)

C(22)–C(23)

C(23)–C(24)

1.17(1)

1.40(1)

1.22(1)

1.24(2)

1.38(2)

1.21(2)

2.019(8)

2.00(1)

P(11)–Pt(1)–P(22)

P(21)–Pt(2)–P(22)

P(11)–Pt(1)–C(11)

P(11)–Pt(1)–C(24)

P(12)–Pt(1)–C(11)

P(12)–Pt(1)–C(24)

P(21)–Pt(2)–C(14)

P(21)–Pt(2)–C(21)

P(22)–Pt(2)–C(14)

P(22)–Pt(2)–C(21)

84.9(1)

85.2(1)

93.2(3)

178.2(3)

178.0(3)

93.9(2)

177.4(4)

92.0(2)

92.1(3)

174.5(3)

C(11)–Pt(1)–C(24)

C(14)–Pt(2)–C(21)

Pt(1)–C(11)–C(12)

C(11)–C(12)–C(13)

C(12)–C(13)–C(14)

C(13)–C(14)–Pt(2)

Pt(1)–C(24)–C(23)

C(24)–C(23)–C(22)

C(23)–C(22)–C(21)

C(22)–C(21)–Pt(2)

87.9(4)

90.6(4)

176(1)

179(1)

178(1)

177(1)

177.3(8)

177(1)

177.5(9)

175.9(8)

Theoretical considerations

In order to understand somewhat the electronic structure of

᎐

the molecular squares cyclo-{Pt(µ-C᎐CC᎐C)(L) } , EH and DF

᎐

2

4

calculations were carried out on the hydrogen-substituted

᎐

model complex cyclo-{Pt(µ-C᎐CC᎐C)(dHpe)} (17-H) of D

᎐

4

4h

symmetry. A rather good agreement is found between the

DF optimised and experimental geometries of 17-H and 17,

respectively. In particular, a slight curvature is computed for

the PtC₄Pt sequences of the square as experimentally observed

(see Table 3).

The DF MO diagram of the optimised geometry of 17-H

shows a closed-shell electron conﬁguration with a rather large

HOMO–LUMO gap of 1.88 eV. A comparable MO diagram is

obtained with EH calculations. The same closed-shell electron

conﬁguration is obtained, with a comparable HOMO–LUMO

gap of 1.82 eV. The composition of the MOs in the HOMO–

LUMO region is similar for both DF and EH results. Therefore,

because of its structural complexity (large size of the molecule)

the detailed analysis of the bonding in 17-H was carried out

using EH calculations.

and less complex, lying with a crystallographic inversion centre

at the centre of the square, of which half is crystallographically

independent. Details of the lower solvate are of comparable

precision and have been deposited. A plot of a molecule of 17 is

shown in Fig. 7, with signiﬁcant structural parameters being

The qualitative MO diagram of model 17-H (not shown here)

is comparable to that of the monometallic model 2-H shown

earlier in Fig. 4. Indeed, as for 2-H, the LUMOs derive almost

exclusively from π* components of the C₄chains, whereas

HOMOs result from strong interactions between d-type metal-

lic FMOs and π components of the carbon units. A set of seven

MOs (three in-plane and four out-of-plane), all of which are

highly delocalised over the Pt₄C₁₆skeleton and quite close

in energy, is found in the HOMO region. All of them are

antibonding between Pt and C_αand between C_βand C_βЈ, but

bonding between C_αand C_β.

Owing to the peculiar nature and the energy of the HOMOs

computed for 17-H, the molecular squares cyclo-{Pt(µ-

᎐

C᎐CC᎐C)L } should be rather easily oxidised without

᎐

2

4

involving important structural changes. Indeed, the ﬁrst

DF ionisation potential computed for model 17-H is 4.79 eV,

which is comparable to that computed for carbon chain-

᎐

Fig. 7 Molecular projection of cyclo-{Pt(µ-C᎐CC᎐C)(dppe)}₄(17),

᎐

normal to the Pt₄plane, in the 10dmso solvate, which is centro-

symmetric.

᎐

containing molecular wires such as {Ru(PH ) Cp} (µ-C᎐CC᎐C)

᎐

3

2

(4.83 eV) which easily undergo one-electron oxidation

processes.¹¹

collected in Table 3. Comparison with 2 shows that the Pt–C

[1.95–2.03(1) Å], C᎐C [1.18–1.22(2) Å], C–C [1.39–1.44(2) Å]

EH Mulliken atomic net charges indicate that, as for 2-H, the

phosphorus atoms are positive (0.64) leading to a substantial

amount of negative charge on C_α(Ϫ0.46) of the carbon chains.

On the other hand, Pt and C_βare nearly neutral (Ϫ0.19 and

Ϫ0.04, respectively).

᎐

and Pt–P distances [2.256–2.285(3) Å] are closely similar; the

angles at Pt subtended by the two C₄edges are between 87.2 and

90.6(5)Њ in 17, compared with 93.2(5)Њ in 2. Along the edges,

angles at the four carbons range between 173 and 179(2)Њ. The

separations of the Pt atoms are 7.726–7.798(1) Å (along

the edges) and 10.703, 11.265(1) Å (along the diagonals).

For the Pt₄plane of the monoclinic form, χ²is 18696, δPt(1–4)

being 0.084, Ϫ0.084, 0.083 and Ϫ0.083(1) Å, and δP(n1,n2)

Ϫ0.162, 0.805; 0.173, 0.178; 0.360, Ϫ0.302 and 0.109,

Ϫ0.190(4) Å.

As found for 2, the phenyl groups of the dppe ligands in 17 lie

over the C₄edges and are bent away from the chain and do not

interfere sterically with each other. (The angles C(1)–Pt–C(1Ј)

and P–Pt–PЈ in 2 are 93.2(5)Њ and 86.2(1)Њ, respectively). This is

Incorporation of Group 11 metals into molecular squares

It was of interest to compare the reactivity of the molecular

squares towards Group 11 molecules or cations with that

described above for the “tweezer” complexes. Internal access

to the corners is somewhat more restricted in the square

complexes, although not prohibitively so. Indeed, previous

examples of Group 11 adducts of platinum-based “tweezer”

complexes show that the Group 11 metal is not coplanar with

the dialkynyl-platinum unit.²⁸

J. Chem. Soc., Dalton Trans., 2002, 383–398

391

View Article Online

The ES mass spectra of solutions of 20 containing

[M^I(NCMe)₄]^ϩ(M^I= Cu or Ag) contain new ions correspond-

ing to [M ϩ Cu]^ϩ(m/z 2629) or [M ϩ Ag ϩ MeCN]^2ϩ(m/z

1356), respectively. Light brown (25) or cream (26) solids were

obtained by addition of {Cu(OTf )}₂C₆H₆or AgOTf, respect-

ively, to solutions of 20, or by adding Pt(OTf )₂(dppe) to the

adducts obtained from the Group 11 species and 2. Analytical

data are consistent with the formation of 1 : 1 adducts of 17

Experimental

General reaction conditions

Reactions were carried out under an atmosphere of nitrogen,

but no special precautions were taken to exclude oxygen during

work-up. Common solvents were dried and distilled under

nitrogen before use. Elemental analyses were performed by

the Canadian Microanalytical Service, Delta, B.C., Canada.

Preparative TLC was carried out on glass plates (20 × 20 cm)

coated with silica gel (Merck 60 GF₂₅₄, 0.5 mm thickness).

with M(OTf ) (M = Cu or Ag), which also contain one unit

I

᎐

of [NH Et ][OTf], namely [{Pt(C᎐CC᎐C)(dppe)} M ][NH Et ]-

᎐

2

4

2

[OTf]₂. However, this formulation was not supported by their

᎐

mass spectra. In their IR spectra two ν(C᎐C) absorptions are

᎐

Instrumentation

present (at 2127 and 2088 cm^Ϫ1for 25; 2147 and 2088 cm^Ϫ1for

26), while their ³¹P NMR spectra each contain two resonances

in ratio 3 : 1, with signiﬁcantly diﬀerent chemical shifts and

J(PPt) values, δ 43.24 [J(PPt) = 2246 Hz] and 46.40 [J(PPt) =

3598 Hz] for 25 and at δ 42.21 [J(PPt) = 2336 Hz] and 44.24

[J(PPt) = 3652 Hz] for 26. As found in the exploratory studies,

their ES mass spectra contained ions at m/z 2629 [17 ϩ Cu]^ϩ

(for 25) and 1356 [17 ϩ Ag(MeCN)]^2ϩ(for 26). These data

suggest incorporation of a single Cu^ϩor Ag^ϩcation into the

complex, although we have not yet been able to get structural

conﬁrmation of this feature; the larger J(PPt) values suggest

that some cis/trans isomerisation may have occurred during the

reaction with concomitant reorganisation of the square.

IR: Perkin Elmer 1720X FT IR. NMR: Bruker CXP300 or

ACP300 (¹H at 300.13 MHz, ¹³C at 75.47 MHz, ³¹P at 121.50

MHz) or Varian Gemini 200 (¹H at 199.8 MHz, ¹³C at 50.29

MHz) spectrometers. Spectra were recorded using solutions in

5 mm sample tubes. FAB mass spectra: VG ZAB 2HF (using

3-nitrobenzyl alcohol as matrix, exciting gas Ar, FAB gun

voltage 7.5 kV, current 1 mA, accelerating potential 7 kV. ES

mass spectra: Finnegan LCQ or VG Platform II. Solutions were

directly infused into the instrument.

Reagents

Buta-1,3-diyne,⁴⁸cis-PtCl₂(PEt₃)₂,⁴⁹cis-Pt(OTf )₂(PEt₃)₂,^3acis-

Further examples of these complexes were obtained from

reactions between 17 and four equivalents of [M^I(NCMe)₄]-

[BF₄] (M^I= Cu, Ag) in acetonitrile, both yielding cream solids

on work-up. The Cu() adduct 27 contains two Cu(NCMe)-

PtCl₂(dppe),⁵⁰cis-Pt(OTf )₂(dppe),^3acis-PtCl₂(dppp),⁵¹cis-

Pt(OTf )₂(dppp),^3a

PtCl₂(cod),⁵²

W(C᎐CC᎐CH)(CO)Cp,

᎐

42

᎐

Co₂(µ-dppm)(CO)₆,⁵³Ru₃(µ-dppm)(CO)₁₀,⁵⁴[Cu(NCMe)₄]-

[BF₄],⁵⁵[Ag(NCMe)₄][BF₄]⁵⁵and AuCl(PPh₃),⁵⁶were prepared

by the cited literature methods.

1

(BF₄) fragments, as shown by H, ¹³C and ³¹P NMR spectral

data. These include two ³¹P triplets at δ 40.03 [J(PPt) = 2275 Hz]

and 43.35 [J(PPt) = 3604 Hz] in a 1 : 1 ratio. The diﬀerences in

both the chemical shifts and coupling constants suggested the

incorporation of two [Cu(NCMe)]^ϩcations into two of the

corners of the square. The ES mass spectra of 27 contained

a doubly-charged ion at m/2z 1388, corresponding to [M Ϫ

2BF₄]^2ϩ. In contrast the silver complex 28 contains four

Ag(NCMe)(BF₄) units, as determined by NMR and ES mass

spectroscopy. The ³¹P NMR spectrum showed a triplet at

δ 42.40 [J(PPt) = 2421 Hz] corresponding to the dppe ligand.

The ES mass spectrum in MeCN showed peaks at m/z 3156

corresponding to [M ϩ 4Ag(MeCN)]^ϩ, m/z 3115 for [M ϩ 4Ag

ϩ 3MeCN]^ϩand a doubly charged peak at m/2z 1540 corre-

sponding to [M ϩ 4Ag ϩ 2MeCN]^2ϩ. Similar adducts of the

Buta-1,3-diynyl-platinum complexes

᎐

(a) cis-Pt(C᎐CC᎐CH) (PEt ) 1. CuI (10 mg, 0.05 mmol) and

᎐

2

3 2

buta-1,3-diyne (5.1 mmol as a 2.8 M solution in thf ) were

added sequentially to a solution of cis-PtCl₂(PEt₃)₂(250 mg,

0.51 mmol) in dmf (12 ml)–NHEt₂(3 ml), and the mixture was

stirred for 30 min. Solvents were removed in vacuo and the

residue was stirred with water (30 ml). The crude material so

obtained was washed with several portions of water, methanol

and Et₂O and then extracted with CH₂Cl₂. The extracts were

concentrated to ca. 5 ml and ﬁltered through celite into rapidly

stirred hexane. The resulting white precipitate was collected,

washed with cold hexane and air dried to give cis-

᎐

Pt(C᎐CC᎐CH) (PEt ) 1 (231 mg, 80%). Crystals suitable for

molecular square cyclo-{Pt(C᎐CC᎐C)(dcype)} containing up

᎐

2

3

᎐

4

to four Ag^ϩcations have been prepared by addition of AgBF₄

or AgOTf to the square and characterised by FAB and MALDI

mass spectrometry.¹⁶

the X-ray study were grown from CH₂Cl₂–hexane by slow

diﬀusion. Anal. Found: C, 43.54; H, 5.73. C₂₀H₃₂P₂Ptؒ0.5CH₂-

᎐

Cl calc.: C, 43.05; H, 5.81%; M, 529. IR (Nujol): ν(᎐CH) 3249s,

᎐

2

ν(C᎐C) 2147s cm^Ϫ1. ¹H NMR (CDCl₃): δ 1.08 [dt, J(HP) = 8 Hz,

᎐

18H, Me], 1.81 [t, J(HP) = 4.6 Hz, 2H, ᎐CH], 1.97 [dq, J(HP) =

᎐

Conclusions

8 Hz, 12H, CH₂]. ¹³C NMR: δ 8.23 [t, J(CP) = 16 Hz, Me], 16.90

(m, CH₂), 60.89 (s, C_δ), 72.04 (s, C_γ), 80.97 (s, C_β), 94.69 (s, C_α).

³¹P NMR (d₆-dmso): δ 5.44 [s, J(PPt) = 2262 Hz, PEt₃]. ES mass

spectrum (in MeOH containing NaOMe, m/z): 1081, [2M ϩ

Na]^ϩ; 552, [M ϩ Na]^ϩ.

This paper has described the syntheses of several examples of

square-planar platinum() complexes containing two mutually

cis buta-1,3-diynyl ligands, which have been used in further

condensations with cis-Pt(OTf )₂(L)₂complexes to give neutral

᎐

square molecules cyclo-{(L) Pt(µ-C᎐CC᎐C) Pt(LЈ) } . Some

᎐

2

2 2

᎐

reactions of the bis(diynyl) complexes with Group 11 cations

(in which they act as “molecular tweezers”) and other reagents,

such as LiBu^t, Co₂(µ-dppm)(CO)₆or Ru₃(CO)₁₀(NCMe)₂, in

which they show the conventional reactions of substituted

1-alkynes, are reported. Inclusion of Group 11 cations and

secondary ammonium cations into the molecular squares has

also been found. Accompanying these studies is a limited ES

mass spectrometric investigation into the aggregation of diynyl

species with various metal cations. Characterisation of several

bis(diynyl)platinum complexes and of one example of the

molecular squares by X-ray crystallography is described. These

results are accompanied by theoretical studies (at the EH and

DF levels of theory) of the electronic structures of these two

types of complex.

(b) Pt(C᎐CC᎐CH) (dppe) 2. Similarly, PtCl (dppe) (1.0 g,

᎐

2 2

1.5 mmol) in dmf–NHEt₂(45 : 15 ml), CuI (30 mg, 0.15 mmol)

and buta-1,3-diyne (15 mmol as a 2.8 M solution in thf )

were stirred for 15 min. Work-up gave a white precipitate of

᎐

Pt(C᎐CC᎐CH) (dppe) 2 (1.0 g, 96%). Crystals suitable for

᎐

2

X-ray study were grown from CH₂Cl₂–hexane by slow diﬀusion.

Anal. Found: C, 59.25; H, 3.76. C₃₄H₂₆P₂Pt calc.: C, 59.09; H,

Ϫ1

᎐

3.76%; M, 691. IR (Nujol): ν(᎐CH) 3288w, ν(C᎐C) 2147s cm

.

᎐

1

᎐

H NMR (CDCl ): δ 1.82 [t, J(HP) = 4Hz, 1H, ᎐CH], 2.42 [m,

᎐

3

2H, P(CH₂)₂P], 7.44–7.89 (m, 10H, PPh₂). ¹³C NMR (CDCl₃):

δ 27.80 (unresolved dd, CH₂P), 61.74 (s, C_γ), 71.75 (s, C_δ), 77.21

(s, C_β), 93.70 (s, C_α), 128.41–133.53 (m, Ph). ³¹P NMR (d₆-

dmso): δ 43.26 [s, J(PPt) = 2288 Hz]. FAB mass spectrum (m/z):

692, [M ϩ H]^ϩ; 642, [M ϩ H Ϫ C₄H]^ϩ; 593, [M Ϫ 2C₄H]^ϩ. ES

392

J. Chem. Soc., Dalton Trans., 2002, 383–398

View Article Online

mass spectrum (MeCN ϩ Ag^ϩ, m/z): 1491, [2M ϩ Ag]^ϩ; 839,

[M ϩ Ag ϩ MeCN]^ϩ; 799, [M ϩ Ag]^ϩ.

stirred for 10 min, when the colour had darkened to orange.

MeI (82 mg, 0.58 mmol) was added and the resulting solution

warmed to room temperature. MeOH was added to give

a cream precipitate, which was collected and washed with

EtOH, MeOH, Et₂O and hexane and then air-dried to give

᎐

(c) Pt(C᎐CC᎐CH) (dppp) 3. A mixture of PtCl (dppp) (1.0 g,

᎐

2

1.47 mmol) in dmf–NHEt₂(45 : 15 ml), CuI (30 mg, 0.15 mmol)

and buta-1,3-diyne (15 mmol as a 2.8 M solution in thf ) was

stirred for 30 min. Concentration and addition of water gave

᎐

Pt(C᎐CC᎐CMe) (dppe) 7 (97 mg, 93%). IR (Nujol): ν(C᎐C)

᎐

2

2148s, 2082m cm^Ϫ1. ¹H NMR (CDCl₃): δ 1.28 (br s, 6H, CH₃),

2.39 (m, 4H, CH₂), 7.40–7.83 (m, 20H, Ph). ¹³C NMR (CDCl₃):

δ 28.25 (m, dppe-CH₂), 50.76 (s, Me), 61.71 (s, C_δ), 71.81 (s, C_γ),

93.09 (s, C_β), 96.96 (s, C_α), 128.48–133.95 (m, dppe-Ph). ES

mass spectrum (CH₂Cl₂–MeOH, m/z): 726, [M ϩ Li]^ϩ; 719, M^ϩ.

᎐

white Pt(C᎐CC᎐CH) (dppp) 3 (831 mg, 80%). Crystals suitable

᎐

2

for the X-ray study were grown from CH₂Cl₂–hexane by slow

diﬀusion. Anal. Found: C, 59.51; H, 4.08. C₃₄H₂₈P₂Pt calc.: C,

᎐

59.57; H, 4.00%; M, 705. IR (Nujol): ν(᎐CH) 3296s, ν(C᎐C)

᎐

2151s cm^Ϫ1. H NMR (d₆-dmso): δ 1.71 [t, J(HP) = 23Hz, 2H,

1

᎐CH], 2.70 [m, 6H, P(CH ) P], 7.31–7.72 (m, 20H, PPh ). ¹³C

᎐

t

᎐

(d) Pt(C᎐CC᎐CH)(C᎐CC᎐CSiMe )(dppe) 8. Similarly, LiBu

᎐ ᎐ ᎐

3

2

3

2

NMR (d₆-dmso): δ 64.40 (s, C_δ), 72.02 (s, C_γ), 128.23–133.41 (m,

Ph). ³¹P NMR (d₆-dmso): δ Ϫ6.69 [s, J(PPt) = 2204 Hz, dppp].

ES mass spectrum (MeOH ϩ Ag^ϩ, m/z): 1519, [2M ϩ Ag]^ϩ;

813, [M ϩ Ag]^ϩ.

(260 µl of a 1.7 M pentane solution, 0.43 mmol) was added to 2

(100 mg, 0.15 mmol) in thf (15 ml) at Ϫ30 ЊC. SiClMe₃(630 µl,

0.58 mmol) was then added and the resulting solution was

warmed to room temperature. MeOH was added to give a

cream precipitate, which was collected and washed with EtOH,

MeOH, Et₂O and hexane. A CH₂Cl₂extract of the solid was

᎐

(d) Pt(C᎐CC᎐CH) (cod) 4. To a solution of PtCl (cod) (200

᎐

2

mg, 0.54 mmol) in dmf–NHEt₂(5 : 3 ml), CuI (9 mg, 0.05

mmol) was added followed by buta-1,3-diyne (5.4 mmol as a 2.2

M solution in thf ). The solution was stirred at room temper-

ature for 15 min and the solvent was removed. Water (10 ml)

᎐

added dropwise to cold hexane to give Pt(C᎐CC᎐CH)-

᎐

(C᎐CC᎐CSiMe )(dppe) 8 (75 mg, 68%). Anal. Found: C, 58.43;

᎐

3

H, 4.56. C₃₇H₃₄P₂PtSi calc.: C, 58.10; H, 4.40%; M, 763. IR

1

(Nujol): ν(C᎐C) 2149s, 2089m cm^Ϫ1. H NMR (CDCl₃): δ 0.07

᎐

was then added and Pt(C᎐CC᎐CH) (cod) 4 separated as a

᎐

2

(s, 9H, SiMe ), 1.75 (s, 1H, ᎐CH), 2.34 (m, 4H, CH ), 7.41–7.79

᎐

3

2

(m, 20H, Ph). ¹³C NMR (CDCl₃): δ 1.30 (s, SiMe₃), 28.83 (m,

brown sticky solid, which rapidly decomposes upon attempted

᎐

isolation (121 mg, 56%). IR (Nujol): ν(C᎐CH) 3270, ν(C᎐C)

᎐

dppe-CH ), 79.07 (m, C᎐C), 126.8–133.63 (m, dppe-Ph).

᎐

2

2131 cm^Ϫ1. The complex is very unstable in solution. However,

addition of dppe (213 mg, 0.54 mmol) in EtOH (15 ml) and

᎐

(e) Pt(C᎐CC᎐CH){C᎐CC᎐C[Au(PPh )]}(dppe) 9. Method

᎐

3

᎐

(i). As above, LiBu^t(260 µl of a 1.7 M pentane solution,

0.43 mmol) was then added to 2 (100 mg, 0.15 mmol) dissolved

in thf (15 ml) and cooled to Ϫ30 ЊC. AuCl(PPh₃) (142 mg,

0.29 mmol) was then added and the resulting solution allowed

to warm to room temperature. MeOH was added to give a

cream precipitate, which was collected and washed with

EtOH, MeOH, Et₂O and hexane and then air-dried to give

stirring at rt for 15 min gave Pt(C᎐CC᎐CH) (dppe) 2 (368 mg,

᎐

2

99%) after precipitation from cold hexane.

᎐

Reactions of Pt(C᎐CC᎐CH) (dppe) 2

᎐

2

᎐

(a) Pt{C᎐CC H[Co (ꢀ-dppm)(CO) ]} (dppe) 5. A mixture of

᎐

2

4

2

2 (100 mg, 0.15 mmol) and Co₂(µ-dppm)(CO)₆(193 mg, 0.29

mmol) in thf (20 ml) was heated under reﬂux for 30 min. TLC

showed the formation of a burgundy coloured compound.

Solvent was removed and the residue was dissolved in CH₂Cl₂

and chromatographed on silica plates (acetone : hexane, 2 : 3).

᎐

Pt(C᎐CC᎐CH){C᎐CC᎐C[Au(PPh )]}(dppe).CH Cl 9 (198 mg,

᎐

3

2

60%). Anal. Found: C, 50.63; H, 3.43. C₅₂H₄₀AuP₃Pt calc.: C,

᎐

51.55; H, 3.42%; M, 1149. IR (Nujol): ν(C᎐C) 2140m, 2084m

᎐

cm^Ϫ1. H NMR (dmso): δ 1.22 (s, 1H, ᎐CH), 2.32 (m, 4H, CH ),

1

᎐

A burgundy band (R_f= 0.65) was collected and recrystallised

᎐

2

7.28–7.83 (m, 35H, Ph). ¹³C NMR (dmso): δ 27.11 (m, CH₂),

128.85–133.85 (m, Ph). ES mass spectrum (CH₂Cl₂–MeOH,

m/z): 1150, [M ϩ H]^ϩ.

᎐

from CH Cl –pentane to give dark red crystals of Pt{C᎐CC -

᎐

2

H[Co₂(µ-dppm)(CO)₄]}₂(dppe) 5 (140 mg, 50%). Anal. Found:

C, 57.30; H, 3.63. C₉₂H₇₀Co₂O₈P₆Pt calc.: C, 57.54; H, 3.67%;

M, 1919. IR (CH₂Cl₂): ν(CO) 2016, 1990, 1960 cm^Ϫ1. ¹H NMR

(CDCl₃): δ 1.86 (s, 2H, C₂H), 2.45 (m, 4H, dppe-CH₂), 3.53 (m,

4H, 2 × dppm CH₂), 6.98–7.99 (m, 60H, Ph). ¹³C NMR

(CDCl₃): δ 29.05 (m, CH₂), 29.57 (m, CH₂), 127.65–138.46 (m,

Ph). ³¹P NMR (CDCl₃): δ 20.66 (s, dppm), 34.96 [s, J(PtP) =

2259 Hz, dppe]. ES mass spectrum (CH₂Cl₂, m/z): 1920, M^Ϫ;

1892–1696, [M Ϫ nCO]^Ϫ(n = 1–8).

Method (ii). Alternatively, addition of a catalytic amount of

CuI (≈3 mg, 0.015 mmol) followed by AuCl(PPh₃) (143 mg, 0.29

mmol) to 2 (100 mg, 0.145 mmol in NHEt₂–thf (5 ml : 10 ml)

and stirring at room temperature for 1 h resulted in the

᎐

formation of a cream precipitate of Pt(C᎐CC᎐CH){C᎐CC᎐C-

᎐

[Au(PPh₃)]}(dppe) 9 (115mg, 69%).

᎐

Reactions of Pt(C᎐CC᎐CH) (dppe) 2 with Group 11 substrates

᎐

2

᎐

2

᎐

(b) Ru (ꢀ-H){ꢀ -ꢁ -C C᎐C[Pt(C᎐CC᎐CH)(dppe)]}(ꢀ-dppm)-

᎐

3

᎐

(a) Cu(SCN){(HC᎐CC ) Pt(dppe)} 10. A mixture of 2 (100

(CO)₇6. A mixture of Ru₃(CO)₁₀(dppm) (100 mg, 0.1 mmol)

and 2 (69 mg, 0.1 mmol) in thf (30 ml) was heated at reﬂux

point for 10 h. Solvent was removed and the residue extracted

with CH₂Cl₂and puriﬁed by TLC (silica gel, acetone : hexane,

4 : 6). The yellow band (R_f0.5) was collected and recrystall-

ised from CH Cl –hexane to give Ru (µ-H){µ -η -C C᎐C-

2

mg, 0.15 mmol) and Cu(SCN) (36 mg, 0.29 mmol) in MeCN

(20 ml) was kept at room temperature for 1 h, the yellow

solution changing to cream–orange. After ﬁltering and evapor-

ation of solvent, extraction of the residue with CH₂Cl₂followed

by dropwise addition to cold hexane gave an orange precipitate

of Cu(SCN){(HC᎐CC ) Pt(dppe)} 10 (112 mg, 95%). IR

2

᎐

2

3

᎐

[Pt(C᎐CC᎐CH)(dppe)]}(µ-dppm)(CO) 6 (88.3 mg, 56%). Anal.

᎐

2

᎐

7

Ϫ1

.

¹H NMR

᎐

(CH Cl ): ν(C᎐C) 2098m, ν(CN) 2155s cm

Found: C, 50.02; H, 3.07. C₆₉H₄₈O₁₀P₄PtRu₃calc.: C, 49.95; H,

2.92%; M, 1577. IR (CH₂Cl₂): ν(CO) 2060m, 2054s, 1999m,

1943(br) cm^Ϫ1. ¹H NMR (CDCl₃): δ Ϫ19.39 [d, J(PtH) = 34 Hz,

1H, RuH], 2.36 (m, 4H, dppe), 3.45 (m, 2H, dppm), 4.36 (m,

2H, dppm), 6.65–8.05 (m, 40H, Ph). ¹³C NMR (CDCl₃): δ 28.89

(s, CH₂), 29.70 (s, CH₂), 128.48–133.88 (m, Ph). ES mass spec-

trum (CH₂Cl₂containing NaOMe, m/z): 1607, [M ϩ OMe]^Ϫ;

1575, [M Ϫ H]^Ϫ; 1547–1463, [M Ϫ nCO]^Ϫ(n = 1–4).

᎐

2

᎐

(CDCl ): δ 1.77 (unresolved m, 1H, ᎐CH), 2.35 (m, 4H, dppe-

᎐

3

CH₂), 7.16–7.83 (m, 20H, dppe-Ph). ¹³C NMR (CDCl₃): δ 28.09

(m, dppe-CH₂), 61.72 (s, C_δ), 71.80 (s, C_γ), 93.11 (s, C_β), 100.00

(s, C_α), 128.47–133.47 (m, dppe-Ph). ³¹P NMR (CDCl₃): δ 37.13

[s, J(PPt) = 2297 Hz, dppe]. ES mass spectrum (CH₂Cl₂–

MeOH, m/z): 1446, [2(2) ϩ Cu]^ϩ; 755, [2 ϩ Cu]^ϩ; 691, [2]^ϩ.

᎐

(b) Ag(SCN){(HC᎐CC ) Pt(dppe)} 11. Similarly, 2 (100 mg,

᎐

2

᎐

(c) Pt(C᎐CC᎐CMe) (dppe) 7. A solution of 2 (100 mg,

0.15 mmol) and Ag(SCN) (48 mg, 0.29 mmol) in MeCN (20 ml)

were stirred at rt for 1 h, the yellow solution changing to cream–

yellow. The ﬁltered solution was evaporated and a CH₂Cl₂

᎐

2

0.15 mmol) in thf (15 ml) was cooled to Ϫ30 ЊC. LiBu^t(260 µl,

0.43 mmol) was added via syringe and the yellow solution was

J. Chem. Soc., Dalton Trans., 2002, 383–398

393

View Article Online

extract of the residue added dropwise to cold hexane to give a

(d₆-dmso): δ 24.10 (m, CH₂dppe), 128.69–133.25 (m, Ph dppe).

³¹P NMR (d₆-dmso): δ 43.32 [s, J(PPt) = 3605 Hz, dppe]. ES

mass spectrum (CH₂Cl₂–MeOH ϩ Cs^ϩ, m/z): 2698, [M ϩ Cs]^ϩ.

᎐

cream precipitate of Ag(SCN){(HC᎐CC ) Pt(dppe)} 11 (124

᎐

2

1

mg, 99%). IR (CH Cl ): ν(C᎐C) 2093m, ν(CN) 2154s cm^Ϫ1. H

᎐

2

᎐

NMR (CDCl ): δ 1.77 [t, 1H, J(PH) = 4.2 Hz, ᎐CH], 2.32 (m,

᎐

3

4H, dppe-CH₂), 7.41–7.83 (m, 20H, dppe-Ph). ¹³C NMR

(CDCl₃): δ 27.72 (s, dppe-CH₂), 61.75 (s, C_δ), 71.77 (s, C_β), 93.60

(s, C_α), 107.92 (s, C_α), 128.45–133.53 (m, dppe-Ph). ³¹P NMR

(CDCl₃): δ 41.16 [s, J(PPt) = 2302.93 Hz, dppe]. ES mass spec-

trum (dmso, m/z): 1490, [2(2) ϩ Ag]^ϩ; 798, [2 ϩ Ag]^ϩ. MS²on

m/z 1490 gave daughter ions at m/z 1441 [2(2) ϩ Cu Ϫ NC₄H]^ϩ,

m/z 1381 [2(2)]^ϩand m/z 798 [2 ϩ Ag]^ϩ.

(c) cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppp)} 18. Similarly, 3 (78 mg,

᎐

4

0.11 mmol) in CH₂Cl₂(50 ml) with NaOAc (60 mg, 0.44 mmol)

in MeOH (10 ml) was treated with Pt(OTf )₂(dppp) (100 mg,

0.11 mmol) in CH₂Cl₂(10 ml). Removal of solvent followed

by addition of hexane resulted in the precipitation of cream

᎐

cyclo-{Pt(µ-C᎐CC᎐C)(dppp)} 18 (210 mg, 73%). Anal. Found:

᎐

4

C, 56.29; H, 3.89. C₁₂₄H₁₀₄P₈Pt₄calc.: C, 56.78; H, 4.00%; M,

1

2621. IR (Nujol): ν(C᎐C) 2148m cm^Ϫ1. H NMR (d₆-dmso):

᎐

δ 2.60 (m, 6H, dppp CH₂), 7.05–7.74 (m, 20H, dppp Ph). ¹³C

᎐

(c) [Cu(NCMe){(HC᎐CC ) Pt(dppe)}]BF ] 12. Similarly, 2

᎐

2

4

(150 mg, 0.22 mmol) and [Cu(NCMe)₄][BF₄] (41 mg, 0.217

NMR (d₆-dmso): δ 24.78 (m, dppp CH₂), 127.56–133.74 (m,

dppp Ph). ³¹P NMR (d₆-dmso): δ Ϫ7.69 [s, J(PPt) = 2188 Hz,

dppp]. ES mass spectrum (CH₂Cl₂–MeOH ϩ NaOMe, m/z):

2644, [M ϩ Na]^ϩ.

᎐

mmol) in MeCN (20 ml) gave cream [Cu(NCMe){(HC᎐CC ) -

᎐

2

Pt(dppe)}][BF₄] 12 (154 mg, 80%). Anal. Found: C, 48.88; H,

3.38. C₃₆H₂₉BF₄NP₂CuPt calc.: C, 48.97; H, 3.31%; M, 883. IR

(Nujol): ν(C᎐CH) 3281m; ν(C᎐C) 2139m; ν(BF) 1060s cm^Ϫ1. ¹H

᎐

NMR (CDCl ): δ 1.75 (s, 2H, ᎐CH), 2.00 (s, 3H, MeCN), 2.53

(d) cyclo-{Pt(ꢀ-C᎐CC᎐C)(PEt ) } ؒ[NH Et ][OTf] 19. cis-

3

᎐

3

2

4

2

(m, 4H, dppe-CH₂), 7.46–7.72 (m, 20H, dppe-Ph). ¹³C NMR

(CDCl₃): δ 1.82 (s, MeCN), 29.67 (s, dppe-CH₂), 65.33 (s, C_δ),

67.56 (C_γ), 77.42 (C_β), 99.21 (s, C_α), 116.29 (s, CH₃CN), 129.29–

133.02 (m, dppe-Ph). ³¹P NMR (CD₃CN): δ 42.18 [s, J(PPt) =

2409 Hz, dppe]. ES mass spectrum (MeCN, m/z): 1446, [2(2) ϩ

Cu]^ϩ; 1396, [2(2) ϩ Cu Ϫ C₄H]^ϩ; 796, [2 ϩ Cu ϩ NCMe]^ϩ; 755,

[2 ϩ Cu]^ϩ.

Pt(OTf )₂(PEt₃)₂(68 mg, 0.09 mmol) in CH₂Cl₂(10 ml) was

slowly added via syringe pump over 2 h to 1 (50 mg, 0.09 mmol)

in CH₂Cl₂(50 ml) containing NHEt₂(1 ml). The initial pale

yellow solution darkened to a light orange–brown. Partial

evaporation and ﬁltration into stirred hexane gave a cream

᎐

precipitate of cyclo-{Pt(µ-C᎐CC᎐C)(PEt ) } ؒ[NH Et ][OTf] 19

᎐

3

2

4

2

(121 mg, 63%). Anal. Found: C, 38.27; H, 6.47. C₆₉H₁₃₂

-

F₃NO₃P₈Pt₄S calc.: C, 38.71; H, 6.21%; M, 2138. IR (Nujol):

᎐

1

ν(C᎐C) 2136m, ν(OTf ) 1254m, 1222m, 1030m cm^Ϫ1. H NMR

(d) [Ag(NCMe){(HC᎐CC ) Pt(dppe)}][BF ] 13. A solution

᎐

2

4

᎐

of 2 (150 mg, 0.22 mmol) and [Ag(NCMe)₄][BF₄] (51 mg,

0.22 mmol) in MeCN (20 ml) was stirred at rt for 1 h. After

evaporation, a CH₂Cl₂extract (5 ml) was added dropwise to

(d₆-dmso): δ 0.64 [dt, J(HP) = 7.5 Hz, 72H, PCH₂Me], 0.83 [dd,

J(HH) = 6.3 Hz, 48H, NH₂(CH₂Me)₂], 1.56 [t, J(HH) = 6.9 Hz,

6H, PCH₂Me], 2.64 (unresolved m, 4H, NH₂(CH₂Me)₂). ¹³C

NMR (d₆-dmso): δ 8.21 (s, PCH₂Me), 11.04 (s, NH₂(CH₂Me)₂),

16.65 [dq, J(CP) = 17.13 Hz, PCH₂Me], 41.60 (s, NH₂-

(CH₂Me)₂), 93.09 (m, C_β) 94.98 (m, C_α). ³¹P NMR (d₆-dmso):

δ Ϫ0.43 [s, J(PPt) = 2260 Hz, PEt₃]. ES mass spectrum (MeOH,

m/z; M ≡ 19): 1990, [M ϩ NH₂Et₂]^ϩ; 1635, [M ϩ NH₂Et₂Ϫ

3PEt₃]^ϩ; 1559, [M ϩ NH₂Et₂Ϫ Pt(PEt₃)₂]^ϩ. MS²on m/z 1990

gave one daughter ion at m/z 1559 [M ϩ NH₂Et₂- Pt(PEt₃)₂]^ϩ.

MS³on m/z 1559 gave two daughter ions at m/z 1485 [M Ϫ

NH₂Et₂]^ϩand m/z 1368 [M Ϫ Pt(PEt₃)₂Ϫ PEt₃]^ϩ. MS⁴on m/z

1485 gave one daughter ion at m/z 1368 [M Ϫ Pt(PEt₃)₂

Ϫ2PEt₃]^ϩ. MS⁵on m/z 1368 gave one daughter ion at m/z 1251

[M Ϫ Pt(PEt₃)₂Ϫ 3PEt₃]^ϩ.

cold rapidly stirred Et₂O (100 ml) to give a cream precipitate of

᎐

[Ag(NCMe){(HC᎐CC ) Pt(dppe)}][BF ] 13 (124 mg, 62%).

᎐

2

4

Anal. Found: C, 46.88; H, 3.28. C₃₆H₂₉BF₄NP₂AgPt calc.: C,

᎐

46.58; H, 3.15%; M, 928. IR (Nujol): ν(᎐CH) 3255m, ν(C᎐C)

᎐

2141m, ν(BF) 1061s cm^Ϫ1. H NMR (CD₃CN): δ 1.95 (s, 2H,

1

᎐

᎐CH), 2.00 (s, 3H, MeCN), 2.41 (m, 4H, dppe-CH ), 7.36–7.65

᎐

2

(m, 20H, dppe-Ph). ¹³C NMR (CD₃CN): δ 1.18 (s, MeCN),

28.33 (m, dppe-CH₂), 65.96 (s, C_δ), 69.60 (s, C_δ), 79.29 (s, C_β),

102.54 (s, C_α), 129.92–134.27 (m, dppe-Ph). ³¹P NMR (CD₃CN):

δ 46.23 [s, J(PPt) = 2434 Hz]. ES mass spectrum (MeCN, m/z):

1491, [2(2) ϩ Ag]^ϩ; 1441, [2(2) ϩ Ag Ϫ C₄H]^ϩ; 839, [2 ϩ Ag ϩ

MeCN]^ϩ; 799, [2 ϩ Ag]^ϩ.

Similar preparations were carried out using NHCy₂, NHPrⁱ₂

and dbu as bases for the reaction between 1 and cis-Pt(OTf )₂-

(PEt₃)₂. The following products were characterised by ES mass

spectroscopy (M ≡ 19):

(i) NHCy₂: ES mass spectrum (CH₂Cl₂, m/z): 2099, [M ϩ

NH₂Cy₂]^ϩ; 1668, [M ϩ NH₂Cy₂Ϫ Pt(PEt₃)₂]^ϩ. MS²on m/z 2099

gave one daughter ion at m/z 1668 [M ϩ NH₂Cy₂- Pt(PEt₃)₂]^ϩ.

(ii) NHPrⁱ₂: ES mass spectrum (CH₂Cl₂, m/z): 2019, [M ϩ

NH₂Prⁱ₂]^ϩ; 1587, [M ϩ NH₂Prⁱ₂Ϫ Pt(PEt₃)₂]^ϩ. MS²on m/z 2019

gave two daughter ions at m/z 1585 [M ϩ NH₂Prⁱ₂- Pt(PEt₃)₂]^ϩ

and m/z 1487 [M Ϫ Pt(PEt₃)₂]^ϩ.

Construction of molecular squares

᎐

(a) cyclo-{Pt(ꢀ-C᎐CC᎐C)(PEt ) )} 16. A solution of NaOAc

᎐

3

2

4

(76 mg, 538 mmol) in MeOH (10 ml) was added to 1 (72.5 mg,

0.14 mmol) in CH₂Cl₂(50 ml). Pt(OTf )₂(PEt₃)₂(100 mg, 0.14

mmol) in CH₂Cl₂(10 ml) was added to this mixture via syringe

pump over a period of 2 h during which time the initial pale

yellow solution darkened in colour. Removal of solvent,

extraction with CH₂Cl₂(5 ml) and ﬁltration into rapidly stirred

᎐

cold hexane gave a cream precipitate of cyclo-{Pt(µ-C᎐CC᎐C)-

(PEt₃)₂}₄16 (183 mg, 70%). Anal. Found: C, 40.43; H, 5.97.

᎐

(iii) dbu: ES mass spectrum (CH₂Cl₂, m/z): 2068, [M ϩ

C₆₄H₁₂₀P₈Pt₄calc.: C, 40.07; H, 6.31%; M, 1917. IR (Nujol):

dbuH]^ϩ; 1639, [M ϩ dbuH Ϫ Pt(PEt₃)₂]^ϩ.

Ϫ1

᎐

ν(C᎐C) 2144 cm

.

¹H NMR (d₆-dmso): δ 1.02 (m, 72H,

᎐

PCH₂CH₃), 1.92 (m, 48H, PCH₂CH₃). ¹³C NMR (d₆-dmso):

δ 8.07 (s, PCH₂CH₃), 16.48 [dq, J(CP) = 17.13 Hz, PCH₂CH₃].

³¹P NMR (d₆-dmso): δ Ϫ0.40 [s, J(PPt) = 2260 Hz, PEt₃]. ES

mass spectrum (CH₂Cl₂–MeOH with NaOMe, m/z): 1940,

[M ϩ Na]^ϩ.

᎐

(e) cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppe)} ؒ[NH Et ][OTf] 20. As for

᎐

4

2

᎐

19, a cream precipitate of cyclo-{Pt(µ-C᎐CC᎐C)(dppe)} ؒ

᎐

4

[NH₂Et₂][OTf] 20 (181 mg, 58%) was obtained from 2 (77.5 mg,

0.11 mmol) in CH₂Cl₂(50 ml) containing NHEt₂(1 ml) and

Pt(OTf )₂(dppe) (100 mg, 0.11 mmol) in CH₂Cl₂(10 ml). Anal.

᎐

(b) cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppe)} 17. Similarly, addition of

Found: C, 53.82; H, 3.75; N, 0.49. C₁₂₅H₁₀₈F₃NO₃P₈Pt₄S calc.:

᎐

4

᎐

Pt(OTf )₂(dppe) (100 mg, 0.11 mmol) in CH₂Cl₂(10 ml) to a

mixture of 2 (77.5 mg, 0.11 mmol) in CH₂Cl₂(50 ml) and

NaOAc (61 mg, 0.45 mmol) in MeOH (5 ml) gave a cream

C, 53.82; H, 3.90; N, 0.50%; M, 2788. IR (Nujol): ν(C᎐C)

᎐

2148m, ν(OTf ) 1274m, 1223m, 1032m cm^Ϫ1

.

¹H NMR (d₆-

dmso): δ 1.34 [t, J(HH) = 9.6 Hz, 6H, NH₂(CH₂Me)₂], 2.32 (m,

4H, CH₂), 3.05 [q, J(HH) = 6.6 Hz, 4H, NH₂(CH₂Me)₂],

7.11–7.83 (m, 20H, Ph). ¹³C NMR (d₆-dmso): δ 10.93 [s,

NH₂(CH₂Me)₂], 27.48 (m, CH₂dppe), 41.41 [s, NH₂(CH₂Me)₂],

92.23 (m, C_α), 110.39 (m, C_β), 127.03–133.26 (m, Ph). ³¹P NMR

᎐

precipitate of cyclo-{Pt(µ-C᎐CC᎐C)(dppe)} 17 (207 mg, 72%).

᎐

4

Anal. Found: C, 55.86; H, 3.77. C₁₂₀H₉₆P₈Pt₄calc.: C, 56.17; H,

3.77%; M, 2566. IR (Nujol): ν(C᎐C) 2148m cm^Ϫ1. ¹H NMR (d₆-

᎐

dmso): δ 2.35 (m, 4H, CH₂), 7.08–7.73 (m, 20H, Ph). ¹³C NMR

394

J. Chem. Soc., Dalton Trans., 2002, 383–398

View Article Online

(d₆-dmso): δ 39.63 [s, J(PPt) = 2257 Hz, dppe]. ES mass

spectrum (dmso, m/z; M ≡ 17): 2639, [M ϩ NH₂Et₂]^ϩ. MS²on

m/z 2639 gave two daughter ions at m/z 2565 [M]^ϩand m/z 2241

[M ϩ NH₂Et₂Ϫ dppe]^ϩ.

2 (77.5 mg, 0.11 mmol) and {Cu(OTf )}₂(C₆H₆) (24 mg, 0.11

mmol) were dissolved in CH₂Cl₂(50 ml) and NHEt₂(1 ml). To

this solution, Pt(OTf )₂(dppe) (100 mg, 0.11 mmol) in CH₂Cl₂

(10 ml) was added via syringe pump over a period of 2 h. The

initial pale yellow solution darkened to orange–brown. The

solvent was reduced to ca. 5 ml and ﬁltered into rapidly

stirred cold hexane, to give a light brown precipitate of

᎐

(f ) cyclo-{Pt(ꢀ-C᎐CC᎐C)(dppp)} ؒ[NH Et ][OTf] 21. Simi-

᎐

4

2

larly, the reaction between 3 (78 mg, 0.11 mmol) and Pt(OTf )₂-

᎐

(dppp) (100 mg, 0.11 mmol) gave cream cyclo-{Pt(µ-C᎐CC᎐C)-

[{Pt(C᎐CC᎐C)(dppe)} Cu][NH Et ][OTf] 25 (202 mg, 65%).

᎐

4

2

(dppp)}₄ؒ[NH₂Et₂][OTf] 21 (195 mg, 68%). Anal. Found: C,

Anal. Found: C, 50.21; H, 3.80; N, 0.60. C₁₂₆H₁₀₈CuF₆-

54.92; H, 4.30; N, 0.50. C₁₂₉H₁₁₆F₃NO₃P₈Pt₄S calc.: C, 54.45; H,

NO₆P₈Pt₄S₂calc.: C, 50.41; H, 3.63; N, 0.46%, M, 2778. IR

᎐

4.11; N, 0.49%; M, 2845. IR (Nujol): ν(C᎐C) 2148m, ν(OTf )

(Nujol): ν(C᎐C) 2127m, 2088m, ν(OTf ) 1280m, 1261m, 1224m,

᎐

1274m, 1223m, 1032m cm^Ϫ1. H NMR (d₆-dmso): δ 1.44 [t,

1

1030m cm^Ϫ1. H NMR (d₆-dmso): δ 3.05 (q, 4H, CH₂), 7.11–

7.83 (m, 20H, Ph). ¹³C NMR (d₆-dmso): δ 27.40 (m, CH₂dppe),

127.06–133.32 (m, Ph). ³¹P NMR (d₆-dmso): δ 43.243 [s, J(PPt)

= 2246 Hz, dppe], 46.40 [s, J(PPt) = 3598 Hz, dppe]. ES mass

spectrum (MeCN, m/z; M ≡ 20): 2629, [M ϩ Cu]^ϩ.

J(HH) = 6.9 Hz, 6H, NH₂(CH₂Me)₂], 2.44 (m, 6H, CH₂), 3.07

[q, J(HH) = 7.2 Hz, 4H, NH₂(CH₂Me)₂], 6.89–7.52 (m, 20H,

Ph). ¹³C NMR (d₆-dmso): δ 11.18 [s, NH₂(CH₂Me)₂], 18.72

(m, CH₂), 24.51 (m, CH₂), 41.94 [s, NH₂(CH₂Me)₂], 109.23

(s, C᎐C), 127.70–137.66 (m, dppp Ph). ³¹P NMR (d₆-dmso):

᎐

δ Ϫ8.02 [s, J(PPt) = 2189 Hz, dppp]. ES mass spectrum

᎐

(b) [{Pt(C᎐CC᎐C)(dppe)} Ag][NH Et ][OTf] 26. Similarly,

᎐

4

2

(CH₂Cl₂/MeOH, m/z): 2695, [21 Ϫ OTf]^ϩ.

addition of Pt(OTf )₂(dppe) (100 mg, 0.11 mmol in CH₂Cl₂

(10 ml) to 2 (77.5 mg, 0.11 mmol) and Ag(OTf ) (29 mg, 0.11

mmol) in CH₂Cl₂(50 ml) containing NHEt₂(1 ml) gave cream

[{Pt(C᎐CC᎐C)(dppe)} Ag][NH Et ][OTf] 26 (300 mg, 95%).

Anal. Found: C, 49.56; H, 3.09; N, 0.60. C₁₂₆H₁₀₈AgF₆-

᎐

(g) cyclo-{Pt (ꢀ-C᎐CC᎐C) (PEt ) (dppe) }ؒ[NH Et ][OTf] 22.

᎐

4

3

4

2

Similarly, 2 (100 mg, 0.15 mmol) and Pt(OTf )₂(PEt₃)₂(105 mg,

᎐

4

2

᎐

0.15 mmol) gave cream cyclo-{Pt (µ-C᎐CC᎐C) (PEt ) (dppe) }ؒ

᎐

4

3

4

2

[NH₂Et₂][OTf] 22 (203 mg, 56%). Anal. Found: C, 47.43; H,

NO₆P₈Pt₄S₂calc.: C, 49.68; H, 3.57; N, 0.46%; M, 3046. IR

4.46; N, 0.60. C₉₇H₁₂₀F₃NO₃P₈Pt₄S calc.: C, 47.26; H, 4.90; N,

᎐

(Nujol): ν(C᎐C) 2147m, 2088m, ν(OTf ) 1271m, 1248m, 1226m,

᎐

1

1031m cm^Ϫ1. H NMR (d₆-dmso): δ 3.07 (m, 4H, CH₂), 6.85–

0.57%; M, 2464. IR (Nujol): ν(C᎐C) 2131m, ν(OTf ) 1272m,

᎐

1223m, 1032m cm^Ϫ1

.

¹H NMR (d₆-dmso): δ 0.12 [m, 36H,

7.49 (m, 20H, Ph). ¹³C NMR (d₆-dmso): δ 10.96 [s, NH₂-

(CH₂Me)₂], 28.56 (m, CH₂), 41.34 [s, NH₂(CH₂Me)₂], 128.42–

133.32 (m, PPh₂). ³¹P NMR (d₆-dmso): δ 42.21 [s, J(PPt) = 2336

Hz, dppe], 44.24 [s, J(PPt) = 3652 Hz, dppe]. ES mass spectrum

(MeCN, m/z; M ≡ 20): 1356, [M ϩ Ag(MeCN)]^2ϩ; 1335,

P(CH₂Me)₃], 1.01 [m, 24H, P(CH₂Me)₃], 1.70 [m, 6H, NH₂-

(CH₂Me)₂], 2.36 (m, 8H, dppe CH₂), 6.33–7.07 (m, 40H, dppe

Ph). ¹³C NMR (d₆-dmso): δ 2.67 [s, P(CH₂Me)₃], 7.38 [s,

P(CH₂Me)₃], 12.01 [s, NH₂(CH₂Me)₂], 29.86 (m, dppe CH₂),

43.32 [s, NH₂(CH₂Me)₂], 124.46–132.27 (m, dppe Ph). ³¹P

NMR (d₆-dmso): δ 5.08 [s, J(PPt) = 2338 Hz, PEt₃], 40.76 [s,

J(PPt) = 2323 Hz, dppe]. ES mass spectrum (MeCN, m/z): 2315,

[M Ϫ OTf]^ϩ.

[M ϩ Ag]^2ϩ

.

᎐

(c) [{Pt(C᎐CC᎐C)(dppe)} {Cu(NCMe)} ][BF ] 27. A solu-

᎐

4

2

4 2

tion of [Cu(NCMe)₄][BF₄] (24 mg, 0.12 mmol) and 17 (75 mg,

0.03 mmol) in CH₂Cl₂(20 ml) was stirred at room temperature

for 1 h, after which solvent was removed. A ﬁltered CH₂Cl₂

extract was added dropwise to cold rapidly stirred Et₂O (100

ml) to give a cream precipitate of [{Pt(C᎐CC᎐C)(dppe)} -

{Cu(NCMe)}₂][BF₄]₂27 (32 mg, 37%). Anal. Found: C, 51.97;

᎐

(h) cyclo-{Pt (ꢀ-C᎐CC᎐C) (PEt ) (dppp) }ؒ[NH Et ][OTf] 23.

᎐

4

3

4

2

Similarly, 3 (96.6 mg, 0.14 mmol) and Pt(OTf )₂(PEt₃)₂(100 mg,

᎐

0.14 mmol) gave cream cyclo-{Pt (µ-C᎐CC᎐C) (PEt ) (dppp) }ؒ

᎐

4

3

4

2

᎐

4

[NH₂Et₂][OTf] 23 (193 mg, 57%). Anal. Found: C, 47.98; H,

4.81; N, 0.56. C₉₉H₁₂₄F₃NO₃P₈Pt₄S calc.: C, 47.69; H, 5.01; N,

H, 3.71, N, 0.71. C₁₂₄H₁₀₂B₂Cu₂F₈N₂P₈Pt₄calc.: C, 50.50; H,

᎐

0.56%; M, 2493. IR (Nujol): ν(C᎐C) 2149m, ν(OTf ) 1290m,

᎐

3.48; N, 0.94%; M, 2949. IR (Nujol): ν(C᎐C) 2087m, ν(BF) 839s

1224m, 1029m cm^Ϫ1

.

¹H NMR (d₆-dmso): δ 1.08 [m, 36H,

᎐

cm^Ϫ1. H NMR (d₆-dmso): δ 2.5 (s, 3H, MeCN), 2.99 (m, 4H,

1

P(CH₂Me)₃], 1.22 [m, 6H, NH₂(CH₂Me)₂], 1.72 [m, 6H,

NH₂(CH₂Me)₂], 1.96 [m, 24H, P(CH₂Me)₃], 2.99 (m, 12H, dppp

CH₂), 7.12–7.71 (m, 40H, dppp Ph). ¹³C NMR (d₆-dmso): δ 8.13

CH₂), 7.19–7.89 (m, 20H, Ph). ¹³C NMR (d₆-dmso): δ, CH₂),

121.89 (s, MeCN), 127.85–134.11 (m, dppe Ph). ³¹P NMR (d₆-

dmso): δ 40.03 [s, J(PPt) = 2275 Hz, dppe], 43.35 [s, J(PPt) =

3604 Hz, dppe]. ES mass spectrum (MeCN, m/z; M ≡ 20): 1388,

[s, P(CH₂Me)₃], 11.17 [s, NH₂(CH₂Me)₂], 16.14 [s, P(CH₂Me)₃],

᎐

24.00 (m, dppp CH ), 41.62 [s, NH (CH Me) ], 92.38 (m, C᎐C),

᎐

2

[M ϩ 2Cu(MeCN)]^2ϩ

.

118.53 (m, C᎐C), 127.85–133.51 (m, dppp Ph). ³¹P NMR

᎐

(d₆-dmso): δ Ϫ7.69 [s, J(PPt) = 2284 Hz, dppp], 6.15 [s, J(PPt) =

2209 Hz, PEt₃]. ES mass spectrum (MeCN, m/z): 2343, [M Ϫ

OTf]^ϩ.

᎐

(d) [{Pt(C᎐CC᎐C)(dppe)} {Ag(NCMe)} ][BF ] 28. Similarly,

᎐

4

4 4

[Ag(NCMe)₄][BF₄] (57 mg, 0.16 mmol) and 17 (100 mg,

0.04 mmol) in CH₂Cl₂(20 ml) gave cream [{Pt(C᎐CC᎐C)-

᎐

(dppe)}₄{Ag(NCMe)}₄][BF₄]₄28 (95 mg, 67%). The compound

darkens upon standing, eventually turning black, and consist-

ent elemental analyses have not been obtained. IR (Nujol):

᎐

(i) cyclo-{Pt (ꢀ-C᎐CC᎐C) (dppe) (dppp) }ؒ[NH Et ][OTf] 24.

᎐

4

2

Similarly, 2 (76 mg, 0.11 mmol) and Pt(OTf )₂(dppp) (100 mg,

0.11 mmol) gave cream cyclo-{Pt (µ-C᎐CC᎐C) (dppe) (dppp) ]ؒ

[NH₂Et₂][OTf] 27 (169 mg, 60%). Anal. Found: C, 53.94; H,

4.05; N, 0.69. C₁₂₇H₁₁₂F₃NO₃P₈Pt₄S calc.: C, 54.14; H, 4.00; N,

᎐

4

2

ν(C᎐C) 2097m, ν(BF) 823s cm^Ϫ1. ¹H NMR (d₆-dmso): δ 2.09 (s,

᎐

3H, MeCN), 2.54 (m, 4H, CH₂), 7.20–8.37 (m, 20H, Ph). ¹³C

NMR (d₆-dmso): δ 28.36 (m, CH₂), 127.72–134.84 (m, PPh₂).

³¹P NMR (d₆-dmso): δ 42.40 [s, J(PPt) = 2421 Hz, dppe]. ES

mass spectrum (MeCN, m/z): 3156, [M ϩ 4Ag ϩ 4MeCN]^ϩ;

᎐

0.50%; M, 2814. IR (Nujol): ν(C᎐C) 2149m, 2086m, ν(OTf )

᎐

1286m, 1244m, 1029m cm^Ϫ1. ¹H NMR (d₆-dmso): δ 1.17 [t, 6H,

J(HH) = 9 Hz, NH₂(CH₂CH₃)₂], 2.53 (m, CH₂), 2.91 [m, 4H,

NH₂(CH₂CH₃)₂], 6.92–7.83 (m, 20H, Ph). ¹³C NMR (d₆-dmso):

3115, [M ϩ 4Ag ϩ 3MeCN]^ϩ; 1535, [M ϩ 4Ag ϩ 2MeCN]^2ϩ

.

δ 11.30 [s, NH₂(CH₂CH₃)₂], 28.56 (m, CH₂dppp). 29.45 (m,

᎐

ES mass spectrometry

CH₂dppe), 41.64 [s, NH (CH CH ) ], 100.28 (s, C᎐C),

᎐

2

3 2

128.38–134.06 (m, Ph). ³¹P NMR (d₆-dmso): δ 43.36 [s, J(PPt) =

2288 Hz, dppe], Ϫ3.45 [s, J(PPt) = 3408 Hz, dppp]. ES mass

spectrum (CH₂Cl₂–MeOH, m/z): 2667, [M Ϫ OTf]^ϩ.

Stock solutions of 2 (0.01 M in MeOH) and of each cation

(0.005 M in 1 : 1 MeOH : H₂O, were prepared using the chlor-

ides (except for Rb^ϩ, for which RbNO₃) were used. The latter

were also used to prepare the mixed cation solution (0.005 M).

Aliquots of 2 (1 ml) and the cations (0.5 ml) were mixed, stirred

for 5 min and the ES mass spectra were measured. Similarly,

Formation of adducts with Group 11 cations

᎐

(a) [{Pt(C᎐CC᎐C)(dppe)} Cu][NH Et ][OTf] 25. Compound

᎐

4

2

J. Chem. Soc., Dalton Trans., 2002, 383–398

395

View Article Online

Table 4 Crystal and reﬁnement data

¯

1

2

3

5

17 (P2₁/c)

17 (P1)

Formula

C₂₀H₃₂P₂Ptؒ0.5CH₂C₂C₃₄H₂₆P₂Ptؒ

C₃₅H₂₈P₂Pt

C₉₂H₇₀Co₄O₈P₆Pt

C₁₂₀H₉₆P₈Pt₄ؒ

≈4.5dmsoؒH₂O

2974.89

C₁₂₀H₉₆P₈Pt₄ؒ

10dmso

3347.55

2CH₂Cl₂

M

571.97

861.49

705.64

1920.22

Crystal system

Space group

a/Å

b/Å

c/Å

α/Њ

β/Њ

Tetragonal

P4₂/nmc

12.3036(8)

Monoclinic

C/2c

28.611(16)

8.958(3)

14.718(14)

Monoclinic

P2₁/n

9.683(4)

22.496(5)

12.993(4)

Monoclinic

P2₁/c

21.486(4)

13.439(2)

29.592(3)

Monoclinic

P2₁/c

21.524(1)

30.235(2)

19.155(1)

Triclinic

P1

¯

13.127(2)

17.201(3)

17.570(3)

70.582(3)

68.705(3)

87.309(3)

3474

16.455(1)

109.59(6)

93.65(3)

99.160(2)

91.937(1)

12458

γ/Њ

V/Å³

Z

2491

4

1.525

1124

3554

4

1.610

1552

2824

4

1.659

1384

8436

4

1.512

3848

1

D_c/g cm^Ϫ3

F(000)

1.564

5780

1.600

1668

Crystal size/mm 0.65 × 0.24 × 0.21

0.40 × 0.22 × 0.65 0.32 × 0.66 × 0.11 0.50 × 0.22 × 0.10 0.35 × 0.10 × 0.10 0.30 × 0.20 × 0.10

T * (min, max)

0.523, 0.894

58.7

0.233, 0.927

43.6

60

0.568, 0.730

51.0

0.336, 0.831

25.92

0.600, 0.831

47.1

0.633, 0.914

43.1

µ/cm^Ϫ1

2θ_max/Њ

58

50

58

50

58

N_total

N (R_int

N_o

R

R_w

26428

1787 (0.026)

1288

0.017

0.034

9558

4967 (0.039)

3422

0.037

0.041

70532

21268 (0.078)

5261

0.092

0.112

139421

21456 (0.040)

9947

0.052

0.050

40676

17074 (0.039)

11568

0.061

0.069

)

5002

3371

0.071

0.074

0.005 M solutions of [M^I(NCMe)₄]BF₄(M^I= Cu, Ag) in

MeOH were mixed with an equimolar amount of 2 in the same

solvent, and the relative intensities of the [M²ϩ M^I]^ϩpeaks

were recorded.

were modelled as disordered, dmso 5 with site occupancy

0.5. Geometries of the components of ring 411, 411Ј were

constrained in reﬁnement.

CCDC reference numbers 169975–169980.

See http://ww w .rsc.org/suppdata/dt/b1/b107929h/ for crystal-

lographic data in CIF or other electronic format.

Structure determinations

For 2 and 3, room-temperature single counter diﬀractometer

data sets (T ca. 295 K; 2θ/θ scan mode, 2θ_maxas speciﬁed) were

measured to the speciﬁed level of redundancy, N_totalreﬂections

(where other than unique) being merged after gaussian absorp-

tion correction, to N unique (R_intcited where appropriate), N_o

with I > 3σ(I ) being used in the full matrix least squares reﬁne-

ment on |F|, minimising Σw∆²and reﬁning anisotropic thermal

parameters for the non-hydrogen atoms, (x, y, z, U_iso)_Hbeing

constrained at estimates. For the remainder, full spheres of data

to 2θ = 58Њ were measured at ca. 153 K using a Bruker AXS

CCD area-detector instrument, merged to unique sets after

“empirical”/multiscan absorption corrections (proprietary

software), N_totdata giving N unique (R_intquoted), N_owith F >

4σ(F) being used in the reﬁnements. All data were measured

using monochromatic Mo-Kα radiation, λ = 0.7107₃Å.

In all cases, conventional residuals R, R_won |F| (statistical

weights) are quoted. Neutral atom complex scattering factors

were used; computation used the XTAL 3.4 program system.⁵⁷

Crystal and reﬁnement data are given in Table 4 and pertinent

structural results are given in Figs. 1–3, 5 and 7 [which show

20% (room temperature) or 50% (low temperature) thermal

envelopes for the non-hydrogen atoms, hydrogen atoms having

arbitrary radii of 0.1 Å)] and Tables 1–3. Individual variations

in procedures, abnormalities, idiosyncrasies, etc., are as follows:

1: Diﬀerence map residues about (3/4, 1/4, 1/4) (etc.) were

modelled as disordered dichloromethane of solvation.

2: Specimens were problematically twinned, one deconvol-

uted reciprocal lattice component being used with separate

scale factors in reﬁnement for hk 1, 2 (k < 6). An analytical

absorption correction was applied.

3: A hemisphere of data was measured; an analytical

absorption correction was applied.

5: Weak and limited data would support meaningful aniso-

tropic displacement parameter reﬁnement for Pt, Co, P only.

17ؒ10dmso: Phenyl ring 212 and dmso molecules 4, 5 were

each modelled as disordered over two sets of sites, occupancies

set at 0.5 after trial reﬁnement. Similarly, in 17ؒ4.5dmsoؒH₂O

(T = 300 K), rings 211, 212, 411 and dmso 3, 4 (S only)

Theoretical calculations

Extended Hückel calculations were carried out on the model

᎐

complexes Pt(C᎐CC᎐CH) (dHpe) (2-H) of C symmetry and

᎐

2

2v

᎐

cyclo-{Pt(µ-C᎐CC᎐C)(dHpe)} (17-H) of D symmetry within

᎐

4

4h

the extended Hückel formalism⁵⁸using the program CACAO.⁵⁹

Standard atomic distances were taken. The exponents (ζ) and

the valence shell ionisation potentials (H_iiin eV) were respect-

ively: 1.3, Ϫ13.6 for H 1s; 1.625, Ϫ21.4 for C 2s; 1.625, Ϫ11.4

for C 2p; 1.6, Ϫ18.6 for P 3s; 1.6, Ϫ14.0 for P 3p; 2.55, Ϫ9.077

for Pt 6s; 2.554, Ϫ5.475 for Pt 6p. The H_iivalue for Pt 5d was

set equal to Ϫ12.59. A linear combination of two Slater-type

orbitals with exponents ζ = 6.013 and ζ₂= 2.696 with the weight-

ing coeﬃcients c₁= 0.6334 and c₂= 0.5513 was used to represent

the Pt 5d atomic orbitals.

Density functional calculations were carried out on the

model complexes Pt(C᎐CC᎐CH) (dHpp) (3-H) of C sym-

metry and cyclo-{Pt(µ-C᎐CC᎐C)(dHpe)} (17-H) of D_4h

᎐

2

2v

᎐

4

symmetry using the Amsterdam Density Functional (ADF)

program⁶⁰developed by Baerends and coworkers.⁶¹The Vosko–

Wilk–Nusair parametrisation⁶²was used for the local density

approximation (LDA) with gradient corrections for exchange

(Becke88)⁶³and correlation (Perdew86).⁶⁴The geometry

optimisation procedure was based on the method developed by

Vesluis and Ziegler.⁶⁵The scalar relativistic eﬀects⁶⁶were taken

into account by use of the quasi-relativistic method.⁶⁷The elec-

tronic conﬁgurations of the molecular systems were described

by a double-ζ Slater-type orbital (STO) basis set for H (1s) and

C (2s, 2p) of the dHpe and dHpp ligands, whereas an uncon-

tracted triple-ζ basis set was used for P (3s, 3p) of the dHpe and

dHpp ligands and for C (2s, 2p) of the C₄H chains, augmented

with a 3d polarisation function. An uncontracted triple-ζ

Slater-type orbital (STO) basis set was used for Pt 5d and

6s atomic orbitals, augmented with a single-ζ 6p function. A

frozen-core approximation was used to treat the core electrons

of C, P and Pt.⁶¹The adiabatic ionisation potential computed

for model 20-H was deﬁned as the energy diﬀerence between

optimised geometries of the reduced and oxidised species.

396

J. Chem. Soc., Dalton Trans., 2002, 383–398

View Article Online

14 Rh, Ir: (a) T. Rappert, O. Nürnberg and H. Werner, Organometallics,

Acknowledgements

1993, 12, 1359; (b) H. Werner, R. W. Lass, O. Gevert and J. Wolf,

Organometallics, 1997, 16, 4077.

We thank the Australian Research Council for support of this

work and Professor M.A. Bennett (Research School of Chem-

istry, Australian National University, Canberra) for a sample of

cis-PtCl₂(PEt₃)₂. BCH and PJL acknowledge receipt of Post-

graduate Research Awards. KC and J-FH thank the Centre de

Ressources Informatique (CRI) of Rennes and the Institut de

Développment et de Ressources en Informatique Scientiﬁque

(IDRIS-CNRS) of Orsay for computing facilities. These studies

were also facilitated by travel grants (ARC IREX, Australia,

and the Centre National de la Recherche Scientiﬁque, France).

15 Heterometallic: (a) A. Wong, P. C. W. Kang, C. D. Tagge and D. R.

Leon, Organometallics, 1990, 9, 1992; (b) F. Paul, W. E. Meyer,

L. Toupet, H. Jiao, J. A. Gladysz and C. Lapinte, J. Am. Chem. Soc.,

2000, 122, 9405.

16 S. M. AlQaisi, K. J. Galat, M. Chai, D. G. Ray III, P. L. Rinaldi,

C. A. Tessier and W. J. Youngs, J. Am. Chem. Soc., 1998, 120, 12149.

17 A. D. Burrows, D. M. P. Mingos, S. E. Lawrence, A. J. P. White and

D. J. Williams, J. Chem. Soc., Dalton Trans., 1997, 1295.

18 D. H. Farrer and G. J. Ferguson, J. Crystallogr. Spectrosc. Res.,

1982, 12, 465.

19 G. B. Robertson and W. A. Wickramasinghe, Acta. Crystallogr.,

Sect. C, 1987, 43, 1694.

20 M. Bonamico, G. Dessy, V. Fares, M. V. Russo and L. Scaramuzza,

Cryst. Struct. Commun., 1977, 6, 39.

21 (a) R. Dembinski, T. Lis, S. Szafert, C. L. Mayne, T. Bartik and

J. A. Gladysz, J. Organomet. Chem., 1999, 578, 229; (b) T. B. Peters,

J. C. Bohling, A. M. Arif and J. A. Gladysz, Organometallics, 1999,

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Article Doi

Preparation of buta-1,3-diynyl complexes of platinum(II) and their use in the construction of neutral molecular squares: Synthesis, structural and theoretical characterisation of cyclo-{Pt(μ-C≡CC≡C)(dppe)}4 and related chemistry

DOI: 10.1039/b107929h

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