Synthesis of tripod ligands containing mixed donor sets with phosphane and pyrazole donors - Bidentate chelate binding modes and dynamic behaviour of tripod ligands in d8-metal complexes (NiII, PdII, PtII)

FULL PAPER

Synthesis of tripod Ligands Containing Mixed Donor Sets with Phosphane and

Pyrazole Donors ؊ Bidentate Chelate Binding Modes and Dynamic Behaviour

of tripod Ligands in d⁸-Metal Complexes (Ni^II, Pd^II, Pt^II)

Ralf Faissner,^[a]Gottfried Huttner,*^[a]Elisabeth Kaifer,^[a]Peter Kircher,^[a]Peter Rutsch,^[a]

and Laszlo Zsolnai^[a][†]

Dedicated to Professor Rolf Gleiter^[‡]

Keywords: Tripod ligands / Conformation / Nickel / Palladium / Platinum

The synthesis of a series of tripod ligands MeOCH₂C(CH₂X)-

(CH₂Y)(CH₂Z) (X = PR₂; Y, Z = PRЈ₂or pz; pz = 1-pyrazolyl)

based on the 3,3-difunctionalized oxetane O^a[CH₂]₂C^a-

(CH₂OMs)(CH₂Br)(O^a−C^a) as the starting material is de-

scribed. With their mixed donor sets these ligands coordinate

to d⁸-metal ions in a bidentate binding mode. One of the

the kind of donor functions and on the kind of co-ligands R.

With palladium(II) and platinum(II) as the d⁸centres, square-

planar coordination is observed throughout. The size of the

chelate cycles varies from six to eight depending on the num-

ber of pyrazole entities within the cycle. The conformations

and the conformational flexibility characterizing the chelate

three donors remains uncoordinated in each case. Coordina- cycles have been analysed by X-ray analyses and by vari-

tion of phosphane donors is generally preferred over coor- able-temperature NMR. The classes of conformations ob-

dination of pyrazole donors. With bulky phosphanes such as

−CH₂PMes₂, however, pyrazole may compete with PR₂, de- twist-boat conformations. Dynamic exchange between these

pending on the kind of the d⁸fragment. Dynamic exchange

conformations is observed. In one case, the same compound

between coordinated and noncoordinated pyrazole donors is forms two different types of crystals that differ by the con-

served may be formally reduced to chair, half-chair and

observed. Tetracoordinate complexes of the general type

L₂MR₂are formed (L₂symbolizes the tripod ligand in its bi-

formation adopted by their chelate cycles. All compounds

have been fully characterized by standard analytical tech-

dentate chelate binding mode with two donors functions co- niques including X-ray structure analysis of 14 chelate com-

ordinating and the third one serving as a dangling arm; M = pounds.

Ni^II, Pd^II, Pt^II). With nickel(II) as the d⁸species, tetrahedral or

square-planar coordination geometries ensue, depending on

( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,

Germany, 2003)

Introduction

The scope of this type of reaction sequence was tested by

applying different phosphorus nucleophiles as well as differ-

ent nitrogen nucleophiles. The coordination properties of

these ligands versus the d⁸-metal ions nickel(), pal-

ladium(), and platinum() were tested to elucidate the

competition between different types of donor groups. In

such coordination compounds the potential tripod ligands

will act as bidentate ligands with the third potential donor

function uncoordinated.^[5b,5f,6]The dynamic exchange be-

tween coordinated and uncoordinated ligand functions in

tripod compounds as well as the conformation of the che-

late cycles are also reported here.

The synthesis of neopentane-based tripod ligands

RCH₂C(CH₂X)(CH₂Y)(CH₂Z) that contain up to three dif-

ferent donor functions X, Y, Z, is generally well developed

for different kinds of donor functions.^[1Ϫ5]The selective in-

troduction of nitrogen donor functions is, however, in most

cases limited to special kinds of nitrogen donors^[5]as well

as to specific reaction schemes^[5]. Pyrazole is a nitrogen-

donor group of more general applicability in tripod syn-

thesis^[5e,5f]that may be especially easily incorporated in

tripod ligands HOCH₂C(CH₂pz)(CH₂PR₂)(CH₂X) by a

series of nucleophilic substitutions and ring-opening reac-

tions starting from the functionalized oxetane

O^a[CH₂]₂C^a(CH₂Br)(CH₂OMs)(O^aϪC^a).^[5e]

Results

[a]

Anorganisch-Chemisches Institut der Universität Heidelberg,

Ligand Synthesis

Im Neuenheimer Feld 270, 69120 Heidelberg, Germany

Fax: (internat.) ϩ 496221/545707

The tripod ligands 3 and 4 were obtained from oxetane

precursors 2, which were themselves synthesized from the

functionally substituted oxetane 1 by standard procedures

E-mail: g.huttner@indi.aci.uni-heidelberg.de

[†]

Deceased.

[‡]

As a late contribution to his 65th birthday.

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DOI: 10.1002/ejic.200200535

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Scheme 1. Synthesis of OH-functionalized tripod compounds

(Scheme 1).^[5e]Some compounds (2a, 2c, 3a, 4a) have al-

ready been described.^[5e]All the compounds 2؊4 were fully

characterized by the usual spectroscopic techniques as well

as by elemental analyses (see Exp. Sect. and Tables 10, 12,

and 14).

Scheme 3. Synthesis of coordination compounds 7؊14

The transformation of the tripod ligands 3 and 4, which

bear a CH₂OH group at the backbone, into the correspond-

ing methyl ethers 5 and 6 followed the standard protocol

(Scheme 2).^[3i,7]None of the difficulties often observed in

the etherification of analogous tripod ligands containing

either three different P donors or P donors and Cp derived

donor functions were encountered.^[3i,4d,8]Analytical data of

5 and 6 are given in the Exp. Sect. and Tables 10, 12, and

14.

Crystal structure analyses of metal complexes derived

from the ligand 5a were performed for compounds 7a, 8,

and 9a (Tables 2Ϫ4, 7, and Figures 1 and 2). All these com-

pounds show a square-planar coordination around the me-

tal centre. Ligand 5a is observed to coordinate via its two

PPh₂donor groups exclusively while the pyrazole donor re-

mains uncoordinated. The six-membered chelate cycle thus

formed shows a half-chair conformation for 7a, 8, and 9a.

Figure 1 shows two examples. Within the chelate cycles

showing a half-chair conformation (7a/1, 8, 9a) the

CH₂OMe group occupies the axial position, with the more

bulky CH₂pz group in the equatorial position throughout.

For 7a two different crystal forms were obtained: one (7a/

1·CH₂Cl₂) contains molecules with the chelate cycle in a

half-chair conformation as well, and the other one (7a/

2·0.5CH₂Cl₂) contains molecules in which the chelate cycle

has a twist-boat conformation, showing that different con-

formations are accessible to the chelate cycles (Figure 2).

These findings agree well with observations made on the

chelate cycles in [{κ²P-R₂PCH₂CH(OH)CH₂PRЈ₂}Rh(η⁴-

cod)]^ϩPF₆^؊. For this type of diphosphane-containing che-

late cycle a thorough analysis of the conformation hyper-

surface^[9]as well as of the NMR dynamics^[7,10]revealed a

small energy difference between half-chair and twist-boat

conformations of the chelate cycle. This agrees well with the

fact that 7a forms two different types of ring conformation

Scheme 2. Synthesis of tripod ligands 5 and 6

Coordination Chemistry

Coordination derivatives, in which compounds 5 and 6 in its crystals under standard crystallization conditions.

bind to MHal₂(M ϭ Ni^II, Pd^II, Pt^II) as bidentate ligands,

Ligands containing one phosphane and two pyrazole N

are obtained by standard procedures (see Exp. Sect.), in donors are found to coordinate to nickel() by one phos-

some cases as single crystals suitable for X-ray analysis phorus and one nitrogen donor (11a, 11c, see Table 1) or

(Scheme 3, Table 1).

by two pyrazole donors with the CH₂PR₂group playing the

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tripod Ligands Containing Phosphane and Pyrazole Donors

Table 1. Coordination compounds 7؊14

FULL PAPER

Compd. Ligand Coord. groups X, Y

Noncoord. groups Z, R

MHal₂Colour of compd. Coord. geometry Crystal

structure

7a

7b

7c

7d

8

9a

9b

10

11a

11b

11c

12

13

14

5a

5b

5c

PPh₂

pz

PPh₂

P(m-Tol)₂

PMes₂

PPh₂

P(m-Tol)₂

PPh₂

pz

py

pz

PMes₂

pz

CH₂OMe

CH₂OEt

CH₂OMe

Me

NiCl₂

NiBr₂

PdCl₂

PtCl₂

NiBr₂

NiCl₂

NiBr₂

PdCl₂

NiCl₂

NiBr₂

orange-coloured^[a]square-planar

yes

no

orange-coloured

ruby-coloured

orange-coloured

red

colourless

pale yellow

colourless

violet

square-planar

tetrahedral

5d

5a

5b

5a

6a

Ϫ^[b]

6a

6b

Ϫ^[c]

no

yes

no

yes

no

yes

violet

tetrahedral

yellow

blueϪviolet

blue

square-planar

tetrahedral

pz

[a]

[b]

In crystalline form: red. Ligand EtOCH₂C(CH₂PPh₂)(CH₂pz)₂; synthesis see ref.^{[5e] [c]}Ligand: CH₃C(CH₂pz)₃; synthesis see ref.^[5e]

Figure 2. X-ray structure (without phenyl groups) of compound

7a/1 (top, half-chair conformation) and 7a/2 (bottom, twist-boat

conformation)

gands containing a pz,pz donor set were used. Thus com-

pounds 11c and 14 (Table 1) are derived from ligands re-

ported earlier.^[5e]In each case the coordination geometry

around nickel() is tetrahedral. Compounds 11aϪc, 13, and

14 are paramagnetic Ϫ in contrast to compounds 7 and 8

with their square-planar nickel coordination.

Analytically pure 14 with its tripod ligand

[5e]

CH₃C(CH₂pz)₃crystallized as a conglomerate of differ-

ent crystal forms, most of which were blue. Their structure

corresponds to a tetrahedral coordination of the nickel

atom as evidenced by crystallography (14, see Tables 1Ϫ4,

8). A few crystals were red-brown. Their quality was, how-

ever, insufficient for X-ray analysis. It is assumed that the

difference in colour of these crystals is due to differing

Figure 1. X-ray structure of compound 8 (top) and 9a (bottom)

derived from ligand 5a

role of a dangling arm (13, see Table 1). Figure 3 shows kinds of coordination, probably involving the formation of

examples of the two coordination modes (P,N versus N,N). dinuclear entities with bromide acting as a bridging ligand.

In addition to the ligands 6a and 6b two other tripod li- Thus, different chelate compounds containing NiBr₂groups

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ber of atoms within the cycle increases by one, such that

P,N-coordinated compounds (11, 12) have seven-membered

chelate cycles and N,N-coordinated compounds (13, 14)

contain eight-membered chelate cycles. Because the pyra-

zole ligands are coplanar with their substituents Ϫ with the

carbon atom bonded to one of its nitrogen centres and the

metal atom coordinated to the other Ϫ the conformation

of the chelate cycles may be characterized by an idealized

graph with a pseudo corner (Q) at the centre of the pyrazole

NϪN bond (Scheme 4).

Scheme 4. Idealized graph for chelate cycles containing pyrazole

donors: A: original; B: idealization

This kind of idealization reduces the pyrazole-containing

chelate cycles to six-membered cycles (B, Scheme 4), even

though they actually have seven or eight atoms within the

cycle (A, Scheme 4) . The observed conformations may

therefore be characterized in the same way as for six-mem-

bered cycles.

Table 2 indicates the conformation of the chelate cycles

observed in each case. The difference between the two

classes Ϫ (i) twist-boat and (ii) chair or half-chair Ϫ is most

clearly evident from the pseudo torsion angle 3Ϫ2Ϫ6Ϫ5

(Table 2). Chair or half-chair conformations have 2Ϫ3 and

6Ϫ5 bonds that are almost parallel. The respective torsion

angles are close to zero (deviation from Ϫ1.9 to ϩ12.9°, see

Table 2). For twist-boat conformations these bonds cannot

be parallel, of course, and the corresponding torsion angles

are between 44.3 and 67.0° (for absolute values, see

Table 2). These two classes are, of course, also differentiated

by the sequence of sign changes of the torsion angles

around the cycles (columns MϪ2Ϫ3Ϫ4 to 6ϪMϪ2Ϫ3 in

Table 2). The different types of conformation listed in

Figure 3. X-ray structure of compound 11a (top) and 13 (bottom)

were prepared (8, 11a, 11c) in addition to 14. The phenom- Table 2 do obviously not reflect the either square-planar or

enon could not be observed for 8 or 11a. With 11c, however, tetrahedral coordination of the metal centre since the same

crystallization yielded violet crystals containing the tetra- types of conformations are found for both coordination

hedrally coordinated monomeric compound (analogous to modes.

11a depicted in Figure 3) and red-brown crystals containing

Table 3 shows that the nickelϪligand distances respond

the dinuclear species 15 (Figure 4). Both kinds of crystals significantly to the kind of coordination. NiϪP distances of

were suitable for X-ray analysis. The nickel centres in 15 ca. 217 pm are found for compounds showing a square-

show idealized square-pyramidal coordination (τ ϭ 0.16, planar coordination of the nickel atom (Table 3) and of ca.

see Figure 4).^[11]

230 pm for tetrahedrally coordinated nickel compounds

With palladium() as the central metal ligand 6a acts as (Table 3). NiϪN distances have only been measured for

a P,N ligand resulting in 12 (Table 1). However, the coordi- compounds with tetrahedrally coordinated nickel atoms,

nation around the palladium() atom is square-planar and are 198 pm, within a few standard deviations, in each

(Figure 5), in contrast to the tetrahedral coordination of case (Table 3). As expected, all nickel compounds that con-

nickel() (11) by the same ligand arrangement.

tain at least one nitrogen donor in their chelate cycle show

With each pyrazole group replacing a one-atom donor tetrahedral nickel coordination. The NiϪCl and NiϪBr dis-

group (e.g. PR₂) of a six-membered chelate cycle, the num- tances are around 221 and 236 pm, respectively (Table 3),

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Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

FULL PAPER

Figure 4. X-ray structure of the dinuclear nickel compound 15; the compound is of crystallographic C_isymmetry

served in 8, 11, or 14 (Table 3). The shortest NiϪBr dis-

tance of 15 (245 pm) corresponds to the terminal NiϪBr

bond. The bridging NiϪBr distances are still around 8 pm

longer than this (Table 3). Consequently, all bonds are

weakened by changing from tetra-coordination (8, 11, and

14) to penta-coordination (15). The fact that the mono-

meric arrangement in 11c and the dimeric arrangement of

the same compound in 15 are of almost equal energy is

indicated by their co-crystallization as a conglomerate in

the same experiment. The solubility of 11c in CH₂Cl₂is

higher than that of 15, such that attempts to dissolve red-

brown 15 in CH₂Cl₂led to violet solutions (Table 1) of 11c.

The angles at the metal centre are in the ranges expected

for square-planar and tetrahedral coordination (Table 4). In

square-planar compounds the angles subtended by the co-

ordinating atoms of the chelate ligands are somewhat larger

than the ideal value of 90° (Table 4). For the tetrahedrally

coordinated compounds these angles are smaller than ex-

pected for an ideal tetrahedron (109.4°, see Table 4). Devi-

ation from this ideal value is greater for a P,N donor set (11

and 12, see Table 4) than for an N,N donor set (13 and 14,

see Table 4).

Figure 5. X-ray structure of compound 12

with no detectable influence due to the kind of coordi-

nation geometry.

Compounds 9a and 12 contain the palladium atom in a

square-planar coordination with the chelate ligand coordi-

nating via one N and one P donor (12). In 12 the PdϪCl

distances (Table 3) are influenced by their trans ligands,

NMR Dynamics

It is well known that L₂NiHal₂(L ϭ aryl phosphane) Ϫ

with the bond trans to the nitrogen donor [228.2(1) pm] even if square-planar in the solid state Ϫ may suffer distor-

being significantly shorter than that trans to the phos- tions to tetrahedral arrangements at room temperature in

phorus donor [235.6(1) pm].

solution such that no ³¹P NMR signals are observed.^[12]

The NiϪP distance of the dinuclear compound 15 is

When crystalline 7a, which consists of crystals with the

235.9 pm (Table 3, Figure 4), which is even longer than the ligand in the chair conformation (7a/1) and crystals in

NiϪP distances in compounds containing tetrahedrally co- twist-boat conformation (7a/2), is dissolved in CH₂Cl₂no

ordinated nickel atoms. This corresponds to the apical posi- ³¹P NMR signals are observed at room temperature. At

tion of the phosphorus donor in 15 (Figure 4). The NiϪBr Ϫ40°C a single sharp resonance is apparent, which broad-

distances are also longer than the NiϪBr distances ob- ens upon lowering the temperature further and gradually

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Table 2. Conformation and torsion angles [°] of the chelate cycles in 7a, 8, 9a, 11Ϫ15

FULL PAPER

Conformation

Compound

MϪ2Ϫ3Ϫ4 2Ϫ3Ϫ4Ϫ5 3Ϫ4Ϫ5Ϫ6 4Ϫ5Ϫ6ϪM 5Ϫ6ϪMϪ2 6ϪMϪ2Ϫ3 3Ϫ2Ϫ6Ϫ5

of the chelate cycle^[a]

Half-chair

Chair

λ-twist

7a/1 (2, 6 ϭ P)

ϩ40.6

ϩ42.4

ϩ41.9

Ϫ68.3

Ϫ65.7

Ϫ70.7

Ϫ58.8

Ϫ44.4

Ϫ54.2

Ϫ46.8

Ϫ55.0

Ϫ53.0

Ϫ45.1

ϩ66.3

ϩ65.3

ϩ68.3

ϩ75.6

Ϫ16.8

Ϫ22.4

Ϫ33.6

Ϫ32.5

Ϫ37.1

Ϫ36.9

Ϫ42.3

Ϫ37.1

Ϫ78.4

ϩ62.7

ϩ82.8

ϩ86.0

ϩ89.6

ϩ89.2

ϩ84.5

ϩ7.6

ϩ14.9

ϩ7.5

ϩ56.3

Ϫ37.0

Ϫ61.6

Ϫ51.6

Ϫ51.0

Ϫ44.3

Ϫ46.9

Ϫ9.1

Ϫ14.7

Ϫ9.6

Ϫ49.0

Ϫ11.2

ϩ11.1

Ϫ3.9

Ϫ6.1

Ϫ16.5

Ϫ6.7

Ϫ1.4

ϩ0.2

Ϫ1.9

ϩ12.9

Ϫ44.3

Ϫ52.9

Ϫ57.7

Ϫ61.7

Ϫ67.0

Ϫ56.9

8

(2, 6 ϭ P)

9a

11a (2 ϭ P, 6 ϭ Q) ϩ53.3

7a/2 (2, 6 ϭ P)

ϩ59.7

11c (2 ϭ P, 6 ϭ Q) ϩ52.5

12

13

14

15

(2 ϭ P, 6 ϭ Q) ϩ64.5

(2, 6 ϭ Q)

ϩ70.0

ϩ78.3

(2 ϭ P, 6 ϭ Q) ϩ63.9

[a]

A consistent numbering scheme for all the compounds as depicted below is used for the sake of easier comparison; the λ-enantiomer

was considered throughout.

Table 3. Selected bond lengths [pm] in 7a, 8, 9a, 11Ϫ15

Coord. geometry^[a]

Comp.

M, Hal

MϪP

MϪN

MϪHal

Square-planar

7a/1

7a/2

8

Ni, Cl

Ni, Br

Pd, Cl

216.8 (1), 217.4 (1)

216.6 (1), 216.8 (1)

217.8 (2), 217.8 (2)

224.7 (2), 225.0 (2)

224.6 (1)

Ϫ

221.1 (1), 221.3 (1)

219.7 (1), 220.4 (1)

234.5 (1), 236.0 (1)

235.6 (1), 236.4 (1)

228.2 (1) (trans to N)

235.6 (1) (trans to P)

234.7 (1), 236.4 (1)

234.6 (1), 235.4 (1)

221.7 (1), 222.2 (1)

234.8 (1), 237.9 (1)

252.6 (1) (bridged)

254.6 (1) (bridged)

245.2 (1) (terminal)

9a

12

203.6 (2)

Tetrahedral

11a

11c

13

14

15

Ni, Br

Ni, Cl

Ni, Br

228.8 (1)

231.9 (2)

Ϫ

197.3 (1)

199.4 (5)

198.2 (3), 198.7 (3)

197.7 (4), 198.4 (4)

207.0 (1)

Ϫ

Square-pyramidal

235.9 (1)

[a]

Standard deviations in units of the least significant digit are given in each case.

Table 4. Selected bond angles [°] in 7a, 8, 9a, 11؊15

Compd.

M, Hal

HalϪMϪHal^[a]

HalϪMϪP

HalϪMϪN

PϪMϪP

PϪMϪN

NϪMϪN

7a/1

7a/2

8

Ni, Cl

Ni, Br

Pd, Cl

Ni, Br

Pd, Cl

Ni, Cl

91.1(1)

93.0(1)

92.1(1)

90.0(1)

124.8(1)

124.3(1)

90.6(1)

125.9(1)

86.2(1), 87.1(1), 175.2(1), 175.7(1)

86.9(1), 88.3(1), 172.7(1), 178.0(1)

86.1(1), 86.8(1), 174.0(1), 177.0(1)

86.4(1), 88.4(1), 175.2(1), 175.8(1)

99.5(1), 116.7(1)

108.4(1), 109.4(1)

87.2(1), 176.9(1)

Ϫ

96.0(1)

92.0(1)

95.2(1)

95.3(1)

Ϫ

97.0(1)

94.6(1)

93.6(1)

Ϫ

9a

11a

11c

12

101.9(1), 113.9(1)

103.3(1), 112.9(1)

88.5(1), 178.3(1)

103.9(1), 105.8(1),

106.3(1), 108.3(1)

98.7(1), 106.3(1),

108.0(1), 112.5(1)

88.0(1), 91.4(1),

164.0(1)

13

Ϫ

105.3(1)

14

15

Ni, Br

123.6(1)

Ϫ

106.8(1)

84.4(1), 89.6(1),

154.9(3)

94.9(1), 98.1(1),

110.2(1)

96.6(1)

Ϫ

[a]

Standard deviations in units of the least significant digit are given in each case.

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tripod Ligands Containing Phosphane and Pyrazole Donors

FULL PAPER

Figure 6. δ/λ isomerisation of 7a; temperature dependence of the ³¹P NMR spectra (81 MHz) of 7a in CH₂Cl₂; experiment, simulation,

and rate constants

evolves into a pattern corresponding to two doublets with (∆G₂^϶₀₀ϭ 37.6Ϯ0.5 kJ/mol). The activation parameters for

2

a coupling constant of J_PPϭ 108 Hz (Figure 6). The analogous processes, involving six-membered chelate cycles

underlying process is interpreted in terms of a δ/λ isomer- containing two phosphorus donors and a rhodium() centre,

isation of the chelate cycle (Scheme 5).

have recently been analysed in detail.^[10]The activation en-

thalpies are somewhat higher (around 60 kJ/mol). The acti-

vation entropies are negative throughout, around Ϫ35 J/

mol K. The ³¹P NMR pattern observed for these rhodium

chelate compounds is thus Ϫ mutatis mutandis Ϫ the same

as the one observed for 7a.^[10]The main difference being

that the ligands in the rhodium compounds are chiral while

the ligand in 7a is not.

Scheme 5. δ/λ isomerisation of the chelate cycle in 7a/2

Nickel compounds 7b and 7c contain two different PR₂

groups in the chelate cycle and their ligands are therefore

chiral (Table 1). It was not possible to obtain crystals suit-

able for X-ray analysis of these compounds. With 7b con-

taining a PPh₂donor and a P(m-Tol)₂donor the limit of

slow exchange could not be reached experimentally at the

lowest achievable temperature in CH₂Cl₂(Ϫ100°C for 7b).

With the more bulky PMes₂donor group in the chelate cy-

cle of 7c (Table 1) a ³¹P NMR spectrum close to the slow

exchange limit was evident at Ϫ90°C. The solution could

be undercooled to Ϫ110°C, at which point the slow ex-

change limit was reached. Above 0°C, where the high tem-

perature limit is not yet reached, paramagnetic broadening

starts to obscure individual resonances.

Due to the chiral conformation of the chelate cycle the

two phosphorus nuclei within the cycle in a twist confor-

mation are no longer equivalent. A pattern of two doublets

is therefore expected for the ³¹P NMR spectrum. The ob-

served temperature dependence of the ³¹P NMR spectra of

7a can be neatly simulated^[13]on the hypothesis of equili-

brating δ- and λ-forms of the chelate cycle. Even though 7a

has also been obtained as crystals containing the chelate

cycle in a chair conformation (7a/1) this conformation is

not observed by NMR (temperature range below Ϫ40°C),

which means that in solution the chair conformation has a

higher energy than the twist-boat conformation. Figure 6

shows a comparison of the observed and the simulated ³¹P

NMR spectra of 7a.

Throughout the temperature range Ϫ30 to Ϫ110°C a pat-

tern with two doublets (²J_PPϭ 95 Hz) persists. A second

The rate constants for the δ/λ isomerisation of 7a (Fig- structure, which appears as a broad singlet at Ϫ30°C,

ure 6) give a linear Eyring plot with ∆G₂^϶₉₈ϭ 40.2Ϯ0.5 kJ/ evolves into a pattern composed of a pair of two doublets

2

mol, ∆H^϶ϭ 28.1Ϯ0.9 kJ/mol and ∆S^϶ϭ Ϫ40.7Ϯ5.0 J/mol with coupling constants of J_PPϭ 98 and 101 Hz (Fig-

K. The coalescence temperature is 200 K (81.015 MHz), ure 7). This type of pattern is typical for the twist-boat con-

which results in ∆G₂^϶₀₀ϭ 37.0Ϯ0.8 kJ/mol, in fair agree- formation of a chiral chelate cycle.^[10]The two doublets,

ment with the value taken from Eyring plot analysis which do not significantly change their appearance between

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

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FULL PAPER

Ϫ30°C and Ϫ110°C (signals at the left- and right-hand side ing the role of a dangling arm (square-planar coordination).

of the spectrum depicted in Figure 7), are ascribed to the

Temperature-dependent ¹H{³¹P} NMR spectra of the

chair conformation of the chelate cycle, which is in only palladium compound 12 (Figure 5) reveal a different type

slow exchange with the twist-boat conformation, such that of dynamic exchange different to those already described.

the appearance of the signals is not affected by exchange While the ³¹P NMR signal of 12 is a singlet in the range

processes (Scheme 6). The thermodynamic stability of the Ϫ80 to 120°C the appearance of the proton spectrum

chair and the twist-boat forms of the chelate cycle is differ- changes drastically (Figure 8).

ent: the signals corresponding to the chair conformation

have a 4:1 integral ratio to the signals corresponding to the

twist-boat conformation at Ϫ30°C, while this ratio is only

3:2 at Ϫ110°C.

1

Figure 8. Variable-temperature H{³¹P} NMR spectra (200 MHz)

of 12; dynamic exchange is clearly apparent at δ ഠ 4.5 ppm and

δ ഠ 6.5 ppm; spectra at 105 and 120°C were recorded in DMSO

Figure 7. ³¹P NMR spectrum of 7c in CH₂Cl₂at Ϫ110°C

as solvent; at lower temperatures the solvent was CH₂Cl₂; asterisks

designate solvent peaks

The NMR data of 7bϪ7d also clearly show that the li-

At Ϫ40°C a pattern of sharp signals is clearly evident,

gands 5bϪ5d bind by two phosphorus donors, with the with all the resonances expected for 12 (Figure 8, Table 11).

CH₂pz group serving as a dangling arm. The structures of The signals corresponding to the coordinated CH₂pz arm

7bϪ7d are thus analogous to that of 7a (Figure 2), which and the noncoordinated one are clearly separated. The res-

is known from crystallography (Tables 1Ϫ4). Interestingly, onances of the coordinated pyrazole group are shifted

when the potential tripod ligands contain two pyrazole do- downfield significantly (δ ϭ 6.64, 8.98, 8.11), in contrast to

nors and one PR₂donor (6a, 6b) the preference for P coor- the noncoordinated one (δ ϭ 6.30, 7.33, 7.60). The methyl-

dination versus N coordination appears to depend on the ene protons of the CH₂pz groups give rise to two doublets

bulkiness of the PR₂ligand. While ligands containing one at δ ϭ 3.79 and 4.02 ppm (noncoordinated) and 4.56 and

PPh₂and two pyrazole donors show P,N coordination ex- 4.82 (coordinated), with similar coupling constants of about

clusively (11a, 11c, 12, 15), ligand 6b with a PMes₂,pz,pz ²J_HHϭ 14.5 Hz. At higher temperatures the corresponding

donor set coordinates via the two pyrazole functions, with signals coalesce. From the protons of the pyrazole groups

the CH₂PMes₂group serving as a dangling arm in 13 (tetra- (Table 11) only H4 (Scheme 13, Exp. Sect.) gives rise to a

hedral coordination). In 7c where ligand 5c offers a PPh₂, signal, which does not overlap with the signals of aromatic

a PMes₂, and a pyrazole donor set the two phosphorus do- protons over the whole temperature range. Coalescence of

nors are bonded exclusively with the CH₂pz function play- signals of H4 for the coordinated and noncoordinated pro-

Scheme 6. Interconversion of the conformation of the chelate cycle in 7c

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Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

FULL PAPER

ton occurs at 105°C (k_cϭ 350 s^Ϫ1), corresponding to

∆G₃^϶₇₈ϭ 77.5Ϯ0.8 kJ/mol. The signals of the methylene

group of the CH₂pz functions (coordinated and noncoordi-

nated) are free from overlap with other signals over the

whole temperature range. Coalescence is observed at 120°C

(k_cϭ 150 s^Ϫ1), corresponding to ∆G₄^϶₀₃ϭ 80.0Ϯ0.8 kJ/mol.

This kind of exchange phenomenon (Scheme 7) has not yet

been observed for potential tripod ligands containing a

P,N,N donor set.^[5b]

Scheme 8. General structure of 16Ϫ19

Compound 7a, after activation with TlPF₆, reacts with

C₃H₅MgBr to produce 16a·PF₆in which the phosphorus

donors of the chelate cycle are trans to an η³-coordinated

allylic system (Scheme 9). The palladium compound

16b·PF₆was obtained by treating [Pd(η³-C₃H₅)Cl]₂with the

[5e]

ligand EtOCH₂C(CH₂PPh₂)(CH₂pz)₂and with KPF₆as

the halide-abstracting reagent (Scheme 9).

Direct, selective substitution of just one halide function

in compounds of the type [(chelate)M^IIHal₂] was, however,

not successful. Substitution products [(chelate)M^IIRHal]

were synthesized by starting from [L₂M^IIRHal] [L₂ϭ cod,

(PPh₃)₂] by reaction with the tripod ligands.

Scheme 7. Dynamic exchange of the coordinated and noncoordi-

nated CH₂pz function of 12 at higher temperatures

Substitution Products

Compound 17 was obtained from [trans-(PPh₃)₂Ni-

All compounds 7Ϫ14 (Table 1) contain the chelate li- (Mes)Br] using 5a as the chelating agent (Scheme 10).

gands bonded to an MHal₂entity. Even though the Similarly, the palladium compound 18 was obtained by

metalϪhalide bond lengths are independent of the type of the reaction of [(η⁴-cod)PdClMe] with 5a (Scheme 11).

chelate ligand within each set of compounds (square-planar, The structures of compounds 16a·PF₆, 16b·PF₆, and 18

tetrahedral, see Table 3), exchange of the halide ligands by (Figure 9, Tables 6 and 9) were analysed by crystallography.

other functions might well influence the binding mode of Suitable single crystals could not be obtained for 17.

the chelate ligand. To analyse this potential influence de-

When, instead of 5a, ligand 6a Ϫ with its two pyrazole

rivatives 16Ϫ19 (Scheme 8, Table 5) were synthesized in functions Ϫ was treated with [trans-(PPh₃)₂Ni(Mes)Br] the

which one or both of the halide functions are replaced by formation of 6a·Ni(Br)Mes as an analogue of 17

organic substituents.

(Scheme 10) was indicated by its ³¹P NMR spectrum (a sin-

Table 5. Substitution compounds 16Ϫ19

Compd. Ligand Coord. group X Noncoord. group RЈ M(R)(L)

Colour of compd. Coord. geometry Crystal structure

16a·PF₆5a

PPh₂

pz

PPh₂

pz

CH₂OMe

CH₂OEt

CH₂OMe

Ni(allyl)^ϩ

Pd(allyl)^ϩ

Ni(Mes)Br

PdMeCl

yellow

colourless

yellow

square-planar

yes

no

yes

16b·PF₆Ϫ^[a]

17

5a

6a

18

pale grey

19·PF₆

Ni(Mes)(PPh₃)^ϩyellow

[a]

Ligand EtOCH₂C(CH₂PPh₂)(CH₂pz)₂; synthesis see ref.^[5e]

Scheme 9. Synthesis of cationic (η³-allyl)metal complexes 16a·PF₆and 16b·PF₆

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FULL PAPER

Scheme 10. Synthesis of compound 17

Scheme 11. Synthesis of compound 18

glet at δ ϭ 11.8 ppm). However, the compound could not

be crystallized. Treatment of the reaction mixture with

TlPF₆resulted in the expected Br^؊o PPh₃exchange to

produce 19·PF₆(Scheme 12), which could be characterized

by X-ray analysis (Figure 10, Tables 6, 9).

The conformation of the chelate cycles (Table 6) in 16a^؉,

16b^؉, 18, and 19^؉is quantitatively similar to that described

for [(chelate)M^IIHal₂] compounds (Table 2). In all four

compounds the coordination around the metal atom is

square-planar. The conformation of the chelate cycles

(Table 6) corresponds to a chair (16a^؉, 19^؉), a half-chair

(18) and a twist-boat conformation (16b^؉). The bond

lengths between the chelate donor atoms and the metal

atoms are very similar to the ones shown in Table 3. The

MϪC and MϪHal distances to the external ligands, as well

as the valence angles at the metal centre, are all in the usual

and normal range (Table 6). The only clear indication of a

trans influence is observed for the MϪP bonds in 18. The

NϪP bond trans to the chloride ligand is not much different

from the one observed in 12 (224.6 pm) with its P₂Cl₂donor

set (Table 3). The MϪP distance trans to the methyl sub-

stituent in 18 is lengthened by the trans influence of the

methyl group to 231.4 pm (Table 6). There is, however, some

uncertainty with respect to the exact values of both dis-

tances, which may be larger than the calculated standard

Figure 9. X-ray structure of the cation 16a^؉(top) and 16b^؉(bot-

tom)

deviation (Table 6), due to the fact that crystals of 18 show inter alia from NMR data. As expected for the dia-

some positional disorder between the chloride and the stereotopic phosphorus nuclei in 17 (the compound as a

methyl substituents even though this disorder could be re- whole is chiral!) two doublets are observed in its ³¹P NMR

solved by appropriate refinement (Table 9).

spectrum (see Exp. Sect. and remark therein). The diamag-

While the structure of the intermediate [6a·Ni(Br)Mes] netism of 17 proves the square-planar coordination of the

formulated in the synthesis of 19·PF₆may be Ϫ albeit in- nickel centre.

directly Ϫ inferred from X-ray analysis of 19·PF₆(see

Even if the above results show that the conformation of

above) the structure of 17 [5a·Ni(Br)Mes] has to be inferred the chelate cycles is not very much dependent on the kind

Scheme 12. Synthesis of 19·PF₆

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Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

FULL PAPER

of co-ligands L in [(chelate)M^IIL₂] there is a definite influ-

ence due to the kind of co-ligands on the type of coordi-

nation around a nickel() centre: ligand 6a results in a tetra-

hedral coordination of the nickel atom with the NiBr₂frag-

ment (11a) while the same ligand coordinated to an

[Ni^II(PPh₃)(Mes)]^ϩfragment induces a square-planar coor-

dination in 19^؉. The greater ligand field of PPh₃and Mes

(19^؉) as compared with the two Br (11a) must be the reason

for this.

Conclusion

1. The synthesis of tripod ligands RCH₂C-

(CH₂PR₂)(CH₂pz)(CH₂X) with X being a phosphorus or a

nitrogen donor has broad applicability.

2. These potential tripod ligands coordinate to d⁸-metal

ions (Ni^II, Pd^II, Pt^II) as bidentate chelate cycles, leaving the

third group as a dangling arm. For ligands with a P,P,N

donor set, coordination via the two phosphorus donors is

generally observed. For ligands with a P,N,N donor set con-

taining a bulky phosphorus donor (CH₂PMes₂), N,N coor-

dination may be preferred over P,N coordination.

Figure 10. X-ray structure of the cation 19^؉(for the sake of clarity,

the phenyl groups of the tripod ligand are represented by their

ipso-carbon atom only)

Table 6. Selected bond lengths [pm], bond angles [°], and torsion angles [°] of compounds 16a, 16b, 18, and 19

16a·PF₆

X

16b·PF₆

18

19·PF₆

R

M

Ni

R, L

M

Pd

X

R, L

M

X

R

L

M

X

pz

L

PPh₃

Ϫ

PPh₂

η³-C₃H₅

pz

η³-C₃H₅

Pd PPh₂CH₃

Half-chair (2, 6 ϭ P)

Cl^ϪNi

Mes^Ϫ

Chelate cycle^[a][b]Chair (2, 6 ϭ P)

λ-twist (2 ϭ P, 6 ϭ Q)

chair (2 ϭ P, 6 ϭ Q)

MϪ2Ϫ3Ϫ4

2Ϫ3Ϫ4Ϫ5

3Ϫ4Ϫ5Ϫ6

4Ϫ5Ϫ6ϪM

5Ϫ6ϪMϪ2

6ϪMϪ2Ϫ-3

3Ϫ2Ϫ6Ϫ5

ϩ45.3

Ϫ62.4

ϩ62.9

Ϫ46.7

ϩ25.6

Ϫ24.8

ϩ0.7

ϩ60.2

Ϫ50.2

Ϫ32.1

ϩ84.5

Ϫ53.7

ϩ0.9

ϩ42.4

Ϫ67.3

ϩ69.3

Ϫ45.2

ϩ17.1

Ϫ16.4

ϩ0.7

ϩ58.6

Ϫ51.1

ϩ65.5

Ϫ80.0

ϩ66.8

Ϫ61.0

ϩ11.9

Ϫ57.0

MϪC

200.8(1) (internal)

202.3(1), 204.6(1) (terminal)

214.4(4) (internal)

211.2(4) (trans to N)

220.7(3) (trans to P)

Ϫ

218.0(3)

194.5(4) (trans to N)

Ϫ

MϪCl

MϪP

Ϫ

236.3(1)

223.7(1) (trans to Cl^Ϫ)

231.4(1) (trans to CH₃

Ϫ

217.0(2), 217.4(2)

230.0(1)

222.4(3) (P ϭ ligand)

225.8(3) (P ϭ PPh₃)

Ϫ

)

MϪN

Ϫ

209.5(3)

196.1(7) (trans to Mes^Ϫ)

PϪMϪR

PϪMϪX

LϪMϪX

LϪMϪR

LϪMϪP

XϪMϪR

93.5(1)

99.5(1)

94.8(1)

72.1(1)

166.4(1)

165.3(1)

97.1(1)

96.5(1)

98.3(1)

67.8(1)

164.7(1)

165.7(1)

88.1(1)

95.8(1)

90.1(1)

86.2(1)

173.6(1)

174.4(1)

88.4(1)

91.0(1)

94.2(1)

87.3(1)

172.2(1)

171.6(1)

^[a]Standard deviations in units of the least significant digit are given in each case. ^[b]A consistent numbering scheme for all the compounds

as depicted below is used for the sake of easier comparison.

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

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FULL PAPER

in Scheme 13.^[15]MS: Finnigan MAT 8230; EI (70 eV); FAB

(xenon; matrix: 4-nitrobenzyl alcohol). UV/Vis: PerkinϪElmer

Lambda 19. Elemental analyses: Microanalytical Laboratory of the

Organisch-Chemisches Institut, University of Heidelberg.

3. For palladium() compounds derived from ligands

containing a P,N,N donor set, dynamic exchange between

coordinated and noncoordinated N donors is observed.

4. While palladium() and platinum() derivatives show

a square-planar coordination throughout, the kind of coor-

dination around the nickel atom (square-planar versus

tetrahedral) depends on the donor set of the chelate ligand

as well as on the kind of co-ligands.

Experimental Section

Scheme 13. Numbering scheme of pyrazole as used for NMR data

General Remarks: All manipulations involving phosphanes were

carried out under argon by means of standard Schlenk techniques.

All solvents were dried by standard methods^[14]and distilled under

argon. The solvents CDCl₃and CD₂Cl₂used for NMR spectro-

Crystallographic Structure Determinations: Suitable crystals were

taken directly from the mother liquor, immersed in perfluorinated

polyether oil, and fixed to a glass capillary at 200 K. The measure-

scopic measurements were degassed by three successive freeze-

˚

pump-thaw cycles and dried over molecular sieves (4 A). NMR: ments were carried out with a Siemens P4 four-circle diffractometer

Bruker Avance DPX 200 at 200.12 MHz (¹H); 50.323 MHz

or with an EnrafϪNonius Kappa CCD diffractometer, using

(¹³C{¹H}); 81.015 MHz (³¹P{¹H}); T ϭ 303 K unless stated other- graphite-monochromated Mo-K_αradiation throughout. For the

wise; chemical shifts (δ) in ppm with respect to CDCl₃(¹H: δ ϭ

7.27 ppm; ¹³C: δ ϭ 77.0 ppm) and CD₂Cl₂(¹H: δ ϭ 5.32 ppm;

¹³C: δ ϭ 53.5 ppm) as internal standards. ³¹P chemical shifts (δ) in

ppm with respect to 85% H₃PO₄(³¹P: δ ϭ 0 ppm) as external stand-

Siemens P4 diffractometer measurements the intensities of three

check reflections (measured every 100 reflections) remained con-

stant throughout the data collection, thus indicating crystal and

electronic stability. The data collected with the Siemens P4 dif-

ard. The NMR numbering scheme for the pyrazole cycle is shown fractometer were corrected as usual, including an experimental ab-

Table 7. Crystallographic data of compounds 7a/1, 7a/2, 8, 9a, and 11a

7a/1

7a/2

8

9a

11a

Empirical formula

(without solvate)

Formula mass [g/mol]

Solvate

Crystal size [mm]

Crystal system

Space group

Lattice constants:

a [pm]

C₃₃H₃₄Cl₂N₂NiOP₂C₃₃H₃₄Cl₂N₂NiOP₂C₃₃H₃₄Br₂N₂NiOP₂C₃₃H₃₄Cl₂N₂OP₂Pd C₂₄H₂₇Br₂N₄NiOP

666.2

1 CH₂Cl₂

0.20ϫ0.30ϫ0.40

monoclinic

P2₁/c (no. 14)

666.2

755.1

Ϫ

0.30ϫ0.30ϫ0.40

monoclinic

P2₁/n (no. 14)

713.9

1 CH₂Cl₂

0.20ϫ0.20ϫ0.30

monoclinic

P2₁/c (no. 14)

637.0

Ϫ

0.30ϫ0.20ϫ0.05

monoclinic

P2₁/n (no. 14)

0.5 CH₂Cl₂

0.20ϫ0.30ϫ0.40

triclinic

¯

P1 (no. 2)

1136.6(3)

2283.6(5)

1359.7(6)

90

93.68(2)

90

1140.2(3)

1118.0(3)

1609.3(3)

81.27(2)

89.71(2)

61.75(1)

1781(1)

2

1110.1(3)

1304.6(2)

2211.3(4)

90

93.41(1)

90

1144.0(2)

2300.8(4)

1367.4(2)

90

86.51(1)

90

1082.5(2)

2004.4(4)

1168.4(2)

90

92.75(3)

90

b [pm]

c [pm]

α [°]

β [°]

γ [°]

V [10⁶ϫpm³]

Z

3522(1)

4

3197(1)

4

3593(1)

4

2532(1)

4

d_x[gϫcm^Ϫ3

T [K]

]

1.417

200

1.320

200

1.569

200

1.473

200

1.671

200

Measuring device

Siemens Nicolet-

Syntex

31

Siemens Nicolet-

Syntex

31

Siemens Nicolet-

Syntex

37

Siemens Nicolet-

Syntex

33

Nonius Kappa

CCD

No. of reflect. for cell

refinement

Scan range [°]

3.5 Յ 2Θ Յ 54.0

4.1 Յ 2Θ Յ 48.0

3.6 Յ 2Θ Յ 51.0

3.5 Յ 2Θ Յ 51.0

4.0 Յ 2Θ Յ 55.0

Method

ω-scan, ∆ω ϭ 0.54° ω-scan, ∆ω ϭ0.54° ω-scan, ∆ω ϭ0.54° ω-scan, ∆ω ϭ0.54° ω-scan, ∆ω ϭ 1.00°

Scan speed

10° min^Ϫ1

8071

7689

5769

I Ն 2σ

403

12° min^Ϫ1

5826

5510

4543

I Ն 2σ

411

12° min^Ϫ1

6225

5908

3916

I Ն 2σ

398

8° min^Ϫ1

7030

6681

4626

I Ն 2σ

403

5 s/frame

10996

5742

4682

I Ն 2σ

302

No. of measured reflections

No. of unique reflections

No. of observed reflections

Observation criterion

No. of param. refined

Resid. el. density [10^Ϫ6e·pm^Ϫ3] 0.61

0.95

4.9/15.4

0.61

4.5/12.2

0.79

5.0/11.0

0.45

3.2/7.6

R₁/R_w[%] (refinement on F²) 4.3/13.5

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tripod Ligands Containing Phosphane and Pyrazole Donors

Table 8. Crystallographic data of compounds 11c, and 12Ϫ15

FULL PAPER

11c

12

13

14

15

Empirical formula

(without solvate)

Formula mass [g/mol]

Solvate

Crystal size [mm]

Crystal system

Space group

Lattice constants:

a [pm]

C₂₅H₂₉Br₂N₄NiOP C₂₄H₂₇Cl₂N₄OPPd C₃₀H₃₉Cl₂N₄NiOP C₁₄H₁₈Br₂N₆Ni

C₅₀H₅₈Br₄N₈Ni₂O₂P₂

651.0

595.8

Ϫ

0.20ϫ0.10ϫ0.05

632.2

Ϫ

0.08ϫ0.15ϫ0.40

488.8

Ϫ

0.30ϫ0.20ϫ0.20

orthorhombic

Pbca (no. 61)

1302.0

Ϫ

0.5 CH₂Cl₂

0.30ϫ0.30ϫ0.30

monoclinic

P2₁/c (no. 14)

0.30ϫ0.30ϫ0.30

triclinic

¯

P1 (no. 2)

958.4(3)

1345.0(3)

2266.8(5)

90

80.63(2)

90

792.1(2)

852.9(2)

1860.4(4)

94.76(3)

100.88(3)

91.97(3)

1228(1)

2

790.0(2)

1225.0(3)

1577.2(3)

91.48(3)

90.15(3)

97.29(3)

1514(1)

2

1418.7(3)

1486.7(3)

1694.3(3)

90

943.3(2)

982.3(2)

1574.2(2)

80.15(1)

74.09(1)

70.04(1)

1314(1)

1

b [pm]

c [pm]

α [°]

β [°]

γ [°]

V [10⁶ϫpm³]

Z

2883(1)

4

3574(1)

8

d_x[gϫcm^Ϫ3

T [K]

]

1.600

200

1.611

200

1.387

200

1.817

200

1.646

200

Measuring device

Siemens Nicolet-

Syntex

31

Nonius Kappa

CCD

Nonius Kappa

CCD

Nonius Kappa

CCD

Siemens Nicolet-

Syntex

32

No. of reflect. for cell

refinement

Scan range [°]

4.3 Յ 2Θ Յ 52.0

4.5 Յ 2Θ Յ 55.0

3.4 Յ 2Θ Յ 55.1

4.6 Յ 2Θ Յ 52.0

4.4 Յ 2Θ Յ 51.0

Method

ω-scan, ∆ω ϭ0.54° ω-scan, ∆ω ϭ1.00° ω-scan, ∆ω ϭ1.00° ω-scan, ∆ω ϭ1.00° ω-scan, ∆ω ϭ0.54°

Scan speed

8° min^Ϫ1

5939

5599

3702

I Ն 2σ

341

10 s/frame

7896

5538

4670

I Ն 2σ

302

2 s/frame

13724

6951

4260

I Ն 2σ

362

10 s/frame

15731

3525

1544

I Ն 2σ

212

8° min^Ϫ1

5162

4848

3833

I Ն 2σ

312

No. of measured reflections

No. of unique reflections

No. of observed reflections

Observation criterion

No. of param. refined

Resid. el. density [10^Ϫ6e·pm^Ϫ3] 0.87

R₁/R_w[%] (refinement on F²) 5.5/15.3

0.43

3.1/6.8

0.83

5.2/12.7

0.78

4.9/6.5

0.76

3.6/9.9

sorption correction. Data from the EnrafϪNonius Kappa CCD

device were processed using the standard Nonius software.^[16]The

calculations were performed using the SHELXT PLUS software

package. Structures were solved by direct methods with the

SHELXS-97 program and refined with the SHELXL-97 pro-

gram.^[17]Graphical handling of the structural data during solution

and refinement was performed with XMPA.^[18]Atomic coordinates

and anisotropic thermal parameters of the non-hydrogen atoms

were refined by full-matrix least-squares calculations. Data relating

to the structure determinations are collected in Tables 7, 8, and 9.

Figures 1Ϫ5, 9, and 10 were prepared using WinRay-32.^[19]CCDC-

194026 to -194039 contain the supplementary crystallographic data

for this paper. These data can be obtained free of charge at

www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge

Crystallographic Data Centre, 12 Union Road, Cambridge

Ligand Synthesis

Synthesis of 2b: Pyrrole (0.81 g, 12 mmol) was dissolved in THF

(50 mL) and deprotonated at 0°C with 1 equiv. of KOtBu (1.35 g,

12 mmol). After warming to 25°C, the solution was stirred for

30 min and then added at 0°C to a solution of 1 (2.59 g, 10 mmol)

in THF (50 mL). The reaction was completed by refluxing for 4 h.

In another flask, HPPh₂(2.23 g, 12 mmol) was dissolved in THF

(50 mL) and deprotonated at 0°C with 1 equiv. of KOtBu (1.35 g,

12 mmol). After warming to 25°C and stirring for 30 min, the red

potassium phosphide solution was added dropwise to the first reac-

tion mixture, which was maintained at 0°C. After warming to 25°C

and stirring for 10 h (the phosphide substitution was monitored by

TLC), the then yellow solution was quenched by the addition of

deoxygenated water (20 mL). The aqueous phase was extracted

with diethyl ether (30 mL, 2ϫ). The combined organic phases were

washed with deoxygenated brine, dried with MgSO₄, filtered, and

concentrated in vacuo. The resulting viscous oil was purified by

column chromatography on silica gel by using petroleum ether/

diethyl ether (1:1; R_fϭ 0.47) as eluent to obtain 1.84 g (5.5 mmol,

55%) of 2b as a colourless, microcrystalline powder. ³¹P NMR

(CDCl₃): δ ϭ Ϫ26.9 (s, PPh₂) ppm. For further analytical data see

Tables 10, 12, and 14.

CB2 1EZ, UK; Fax: (internat.)

deposit@ccdc.cam.ac.uk].

ϩ 44-1223/336-033; E-mail:

Materials: Silica gel (Kieselgel 32Ϫ63 µm, ICN Biomedicals

GmbH) used for chromatography was degassed at 1 mbar for 24 h

and saturated with argon. A solution of nBuLi in hexane (2.5 )

was used for deprotonations. 1,^[1c]2a,^[5e]2c,^[5e]3a,^[5e]4a,^[5e]

EtOCH₂C(CH₂PPh₂)(CH₂pz)₂,^[5e]CH₃C(CH₂pz)₃,^[5e]HPPh₂,^[20]

HPMes₂,^[21][trans-(PPh₃)₂Ni(Mes)Br],^[22]and [(cod)PdClMe]^[23]

were prepared according to or by adaptation of literature

procedures. All other chemicals were obtained from commercial

suppliers and used without further purification. Boiling range of

the light petroleum ether used: 40Ϫ60°C. NMR and analytical data

are collected in Tables 10Ϫ15.

General Procedure for the Synthesis of 3 and 4 The appropriately

substituted oxetane 2 (1 equiv.) was dissolved in THF (50 mL). In

a second flask, HPR₂(1.2 equiv.) was dissolved in THF (50 mL)

and deprotonated at 0°C with nBuLi (1.2 equiv.). After warming

to 25°C and stirring for 30 min, the red lithium phosphide solution

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

www.eurjic.org

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2231

R. Faissner, G. Huttner, E. Kaifer, P. Kircher, P. Rutsch, L. Zsolnai

FULL PAPER

Table 9. Crystallographic data of compounds 16a, 16b, 18, and 19

16a·PF₆

16b·PF₆

18

19·PF₆

Empirical formula

(without solvate)

Formula mass [g/mol]

Solvate

Crystal size [mm]

Crystal system

Space group

Lattice constants:

a [pm]

C₃₆H₃₉F₆N₂NiOP₃

C₂₈H₃₄F₆N₄OP₂Pd

C₃₄H₃₇ClN₂OP₂Pd

C₅₁H₅₃F₆N₄NiOP₃

781.3

725.0

Ϫ

0.05ϫ0.05ϫ0.30

orthorhombic

Pna2₁(no. 33)

693.5

Ϫ

0.20ϫ0.10ϫ0.05

monoclinic

P2₁/n (no. 14)

1003.6

0.75 CH₂Cl₂

0.30ϫ0.30ϫ0.40

monoclinic

Cc (no. 9)

0.35 CH₂Cl₂

0.10ϫ0.05ϫ0.05

triclinic

¯

P1 (no. 2)

1706.3(3)

1207.7(2)

1875.0(5)

90

95.80(1)

90

3844(1)

4

1947.8(4)

1712.2(3)

898.3(2)

90

2996(1)

4

1110.9(2)

1328.7(3)

2174.2(4)

90

91.70(3)

90

3208(1)

4

1091.5(2)

1186.1(2)

2098.4(4)

91.25(3)

105.04(3)

111.04(3)

2429(1)

b [pm]

c [pm]

α [°]

β [°]

γ [°]

V [10⁶ϫpm³]

Z

2

d_x[gϫcm^Ϫ3

T [K]

]

1.460

200

1.607

200

1.430

200

1.412

200

Measuring device

No. of reflect. for cell

refinement

Siemens Nicolet-Syntex

25

Nonius Kappa CCD

Scan range [°]

4.1 Յ 2Θ Յ 51.0

ω-scan, ∆ω ϭ0.54°

12° min^Ϫ1

3430

2772

I Ն 2σ

477

0.44

5.3/14.6

3.2 Յ 2Θ Յ 52.0

ω-scan, ∆ω ϭ1.00°

30 s/frame

43721

5882

5315

I Ն 2σ

399

0.39

2.8/6.3

3.7 Յ 2Θ Յ 55.0

ω-scan, ∆ω ϭ1.00°

30 s/frame

13378

7316

5458

I Ն 2σ

375

0.62

5.5/10.0

3.7 Յ 2Θ Յ 50.0

ω-scan, ∆ω ϭ0.50°

30 s/frame

16851

8526

5380

I Ն 2σ

548

1.02

14.6/24.3

Method

Scan speed

No. of measured reflections

No. of unique reflections

No. of observed reflections

Observation criterion

No. of param. refined

Resid. el. density [10^Ϫ6e·pm^Ϫ3

R₁/R_w[%] (refinement on F²)

]

was added dropwise to the oxetane solution at 0°C. The mixture

was allowed to warm to 25°C, while the reaction progress was

monitored by TLC. Upon completion (10 h stirring at 25°C), the

General Procedure for the Synthesis of 5 and 6: The substituted

hydroxy compound 3 or 4 (1 equiv.), respectively, was dissolved in

THF (50 mL) and the solution was cooled to 0°C. Addition of

reaction was quenched by the addition of deoxygenated water solid KOtBu (2 equiv.) yielded a clear, pale yellow solution. After

(50 mL). The aqueous phase was extracted with diethyl ether

5 min of stirring at 0°C, 2 equiv. of methyl iodide was added

(30 mL, 2ϫ). The combined organic phases were washed with de-

rapidly. Within a few minutes KI precipitated. The suspension was

oxygenated brine, dried with MgSO₄, filtered, and concentrated in stirred for at 0°C 1 h (the methylation was monitored by TLC).

vacuo yielding the crude products as pale yellow oils. The crude

product was purified by column chromatography on silica gel. 3b:

Starting material 2a (2.02 g, 6.0 mmol). Eluent petroleum ether/

The solvent was evaporated in vacuo at 0°C. The residue was dis-

solved in diethyl ether (30 mL) and the solution was filtered to

remove potassium iodide. Removal of the solvent yielded the crude

diethyl ether (2:1; R_fϭ 0.24). Yield 1.90 g (3.45 mmol, 58%) as a products as colourless oils. The crude product was purified by col-

colourless, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ29.9 umn chromatography on silica gel. 5a: Starting material 3a (1.77 g,

4

[d, J_PPϭ 10 Hz, P(m-Tol)₂], Ϫ29.5 (d, J_PPϭ 10 Hz, PPh₂) ppm.

3c: Starting material 2a (1.97 g, 5.85 mmol). Eluent petroleum

ether/diethyl ether (1:1; R_fϭ 0.51). Yield 2.89 g (4.75 mmol, 81%)

as a colourless, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ

3.4 mmol). Eluent petroleum ether/diethyl ether (3:1; R_fϭ 0.36).

Yield 1.41 g (2.6 mmol, 78%) as a colourless, microcrystalline pow-

der. ³¹P NMR (CDCl₃): δ ϭ Ϫ28.7 (s, PPh₂) ppm. 5b: Starting

material 3b (1.60 g, 2.9 mmol). Eluent petroleum ether/diethyl ether

4

Ϫ35.9 (d, J_PPϭ 16 Hz, PMes₂), Ϫ28.3 (d, J_PPϭ 16 Hz, PPh₂). (3:1; R_fϭ 0.36). Yield 1.31 g (2.3 mmol, 80%) as a colourless,

3d: Starting material 2a (2.02 g, 6.0 mmol). Eluent petroleum ether/

diethyl ether (3:1; R_fϭ 0.35). Yield 1.35 g (2.5 mmol, 42%) as a

microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ29.0 [d, ⁴J_PP

6 Hz, P(m-Tol)₂], Ϫ28.7 (d, J_PPϭ 6 Hz, PPh₂) ppm. 5c: Starting

ϭ

4

colourless, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ29.9 material 3c (700 mg, 1.15 mmol). Eluent petroleum ether/diethyl

(br. s, PPh₂), Ϫ18.5 [br. s, P(c-C₆H₁₁)₂] ppm. 3e: Starting material ether (3:1; R_fϭ 0.43). Yield 615 mg (1.0 mmol, 87%) as a colour-

2b (670 mg, 2.0 mmol). Eluent petroleum ether/diethyl ether (2:1,

R_fϭ 0.36). Yield 830 mg (1.6 mmol, 80%) as a colourless, micro-

crystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ29.5 (s, PPh₂) ppm.

4b: Starting material 2c (1.75 g, 8.0 mmol). Eluent petroleum ether/

diethyl ether (2:3; R_fϭ 0.35). Yield 2.65 g (5.4 mmol, 68%) as a

less, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ35.8 (d,

4

⁴J_PPϭ 6 Hz, PMes₂), Ϫ28.3 (d, J_PPϭ 6 Hz, PPh₂). 5d: Starting

material 3e (625 mg, 1.2 mmol). Eluent petroleum ether/diethyl

ether (2:1; R_fϭ 0.65). Yield 560 mg (1.05 mmol, 87%) as a colour-

less, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ29.2 (s,

colourless, microcrystalline powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ36.5 PPh₂) ppm. 6a: Starting material 4a (1.62 g, 4.0 mmol). Eluent

(s, PMes₂) ppm. For further analytical data see Tables 10, 12, and

14.

petroleum ether/diethyl ether (2:1; R_fϭ 0.49). Yield 1.49 g

(3.6 mmol, 89%) as a colourless, microcrystalline powder. ³¹P

2232

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

Table 10. Chemical shifts (δ values), integrals [x H] and coupling constants J in the H{³¹P} NMR spectra of 2Ϫ6 in CHCl₃

FULL PAPER

1

Compd.^[a][b]CH₂N

[2 H]

CH₂O

[2 H]

CH₂P

[4 H]

OH

[1 H]

OCH₃

[3 H]

Pyrazole-H^[c]

H4^[d][1 H] H5^[d][1 H] H3^[d][1 H]

Aryl-H

Other

2b

4.48 s

4.30 d, 4.42 d 2.44 s [2 H]

Ϫ

7.36Ϫ7.51 m 6.19 pt, 6.72 pt

[4 H]

²J_HHϭ 6.2

[10 H]

[4 H]

pyrrole-H^[c]

3a

3b

3c

4.23 s

4.28 s

3.26 s

2.46 br. s

2.49 br. s

n. d.

Ϫ

6.18 t

6.21 t

6.16 t

7.09 d

7.15 d

6.90 d

7.49 d

7.50 d

(o)

7.33Ϫ7.46 m

[20 H]

7.22Ϫ7.49 m 2.35 br. s [6 H]

[18 H] m-CH₃

6.78 m [4 H], 2.24 s [6 H]

p-CH₃

7.29Ϫ7.48 m 2.38 s, 2.40 s

[10 H]

7.30Ϫ7.52 m 1.21 m, 1.48 m,

[10 H]

3.31 s

4.06 br. s

3.92 br. s

4.13 d, 4.26 d 3.23 d, 3.36 d 2.49 m, 2.72 d,

²J_HHϭ 14.2

4.29 br. s

4.11 s

²J_HHϭ 12.0

2.86 d

²J_HHϭ 14.3

[12 H] o-CH₃

3d

3e

4a

4b

3.30 d, 3.46 d 1.73 m, 2.33 d,

²J_HHϭ 11.8

4.22 br. s

n. d.

Ϫ

6.24 t

(o)

2.46 d

1.73 m [22 H]

cyclohexyl-H

²J_HHϭ 14.7

2.24 d, 2.39 d

²J_HHϭ 14.3

3.43 s

Ϫ

7.28Ϫ7.51 m 6.12 pt, 6.69 pt

[20 H]

[4 H]

pyrrole-H

[c]

4.22 d, 4.46 d 3.27 s

[4 H]

2.13 s [2 H]

2.55 s [2 H]

4.37 br. s

4.01 br. s

6.26 t

[2 H]

7.31 d

[2 H]

7.60 d

[2 H]

7.35Ϫ7.48 m

[10 H]

²J_HHϭ 14.3

4.24 d, 4.38 d 3.33 s

[4 H]

6.22 t

[2 H]

7.38 d

[2 H]

7.54 d

[2 H]

6.83 m [4 H] 2.26 s [6 H]

p-CH₃

²J_HHϭ 14.3

2.40 br. s

[12 H] o-CH₃

5a

5b

5c

4.44 s

3.03 s

3.04 s

2.51 br. s

2.48 m

Ϫ

2.80 s 6.24 t

2.81 s 6.24 t

2.77 s 6.19 t

(o)

7.56 d

7.55 d

7.51 d

7.32Ϫ7.48 m

[20 H]

7.22Ϫ7.43 m 2.33 s, 2.35 s

[18 H]

6.76 m [4 H], 2.21 s [6 H]

p-CH₃

7.28Ϫ7.50 m 2.34 s, 2.48 s

7.13 d

(o)

[6 H] m-CH₃

4.36 d, 4.45 d 3.00 d, 3.16 d 2.38 br. s, 2.54 d,

²J_HHϭ 14.0

²J_HHϭ 9.2

2.77 br. s

²J_HHϭ 14.6

[10 H]

[12 H]

o-CH₃

5d

6a

6b

4.14 s

2.99 s

2.42 br. s

Ϫ

2.80 s

Ϫ

7.31Ϫ7.46 m 6.12 pt, 6.62 pt

[20 H]

[4 H]

pyrrole-H

[c]

4.32 d, 4.43 d 3.03 s

[4 H]

2.23 s [2 H]

2.66 s [2 H]

2.92 s 6.28 t

[2 H]

7.58 d

[2 H]

7.71 d

[2 H]

7.33Ϫ7.50 m

[10 H]

²J_HHϭ 14.2

4.34 d, 4.43 d 3.11 s

[4 H]

3.03 s 6.25 t

[2 H]

7.55 br. s

[2 H]

7.55 br. s

[2 H]

6.82 m [4 H] 2.26 s [6 H]

p-CH₃

2.42 br. s [12 H]

o-CH₃

²J_HHϭ 14.2

[a]

[b]

s ϭ singlet; d ϭ doublet; t ϭ triplet; m ϭ multiplet; br. s ϭ broad signal; pt ϭ pseudo triplet; (o) ϭ overlapped; n. d. ϭ not detected.

Coupling constants in Hz. Coupling constant J_HHϭ 2.0 Hz. See Scheme 13 for numbering scheme of the pyrazole.

[c]

3

[d]

NMR (CDCl₃): δ ϭ Ϫ28.6 (s, PPh₂) ppm. 6b: Starting material 4b

(1.95 g, 4.0 mmol). Eluent petroleum ether/diethyl ether (2:1; R_fϭ

0.65). Yield 1.65 g (3.3 mmol, 82%) as a colourless, microcrystalline

powder. ³¹P NMR (CDCl₃): δ ϭ Ϫ36.6 (s, PMes₂) ppm. For further

analytical data see Tables 10, 12, and 14.

Recrystallization from CH₂Cl₂/Et₂O afforded two different kinds

of red crystals (7a/1·CH₂Cl₂and 7a/2·0.5CH₂Cl₂), both suitable for

X-ray structure analysis. ³¹P NMR (CD₂Cl₂, Ϫ30°C): δ ϭ 11.2 (s,

2

PPh₂) ppm. ³¹P NMR (CD₂Cl₂, Ϫ100°C): δ ϭ 9.6 (d, J_PP

ϭ

2

108 Hz, PPh₂), 13.6 (d, J_PPϭ 108 Hz, PPh₂) ppm. 7b: Starting

material 5b (590 mg). Yield 500 mg (0.72 mmol, 72%) as an orange-

coloured, microcrystalline solid. ³¹P NMR (CD₂Cl₂, Ϫ30°C): δ ϭ

11.3 [br. s, PPh₂, P(m-Tol)₂] ppm. ³¹P NMR (CD₂Cl₂, Ϫ100°C):

δ ϭ 9.4 (d, ²J_PPϭ 110 Hz), 12.1Ϫ15.0 (m) ppm. 7c: Starting mate-

rial 5c (650 mg). Yield 710 mg (0.95 mmol, 95%) as a ruby-col-

Coordination Chemistry

General Procedure for the Synthesis of 7a؊d: A solution of the

respective tripod ligand 5 (1.05 mmol) in ethanol (10 mL) was ad-

ded rapidly to a solution of NiCl₂·6H₂O (240 mg, 1.0 mmol) in

ethanol (10 mL). The colour of the reaction mixture changed im-

mediately to red and within a few minutes the nickel complexes

precipitated. After stirring at 25°C for 1 h, the precipitate was fil-

tered off, washed with 10-mL portions of diethyl ether (3ϫ), and (br. s, twist-PMes₂, twist-PPh₂), 2.2 (d, J_PPϭ 95 Hz, chair-PPh₂)

dried in vacuo. 7a: Starting material 5a (565 mg). Yield 540 mg

(0.85 mmol, 85%) as an orange-coloured microcrystalline solid.

oured, microcrystalline solid. H NMR and ¹³C NMR: due to dy-

1

namic processes, no sharp signals could be detected. ³¹P NMR

2

(CD₂Cl₂, Ϫ30°C): δ ϭ Ϫ6.6 (d, J_PPϭ 95 Hz, chair-PMes₂), Ϫ0.5

2

ppm. ³¹P NMR (CD₂Cl₂, Ϫ100°C): δ ϭ Ϫ4.8 (d, J_PPϭ 95 Hz,

2

chair-PMes₂), Ϫ3.0 (d, J_PPϭ 98 Hz, twist-PMes₂), Ϫ0.2 (d,

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

www.eurjic.org

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2233

R. Faissner, G. Huttner, E. Kaifer, P. Kircher, P. Rutsch, L. Zsolnai

FULL PAPER

1

Table 11. Chemical shifts (δ values), integrals [x H] and coupling constants J in the H{³¹P} NMR spectra of 7Ϫ18 in CH₂Cl₂

Compd.^[a][b]CH₂N

[2 H]

CH₂O

[2 H]

CH₂P

[4 H]

OCH₃

[3 H] H4^[d][1 H] H5^[d][1 H] H3^[d][1 H]

Pyrazole-H^[c]

Aryl-H

Other

7a

7b

7d

3.82 s

3.66 s

1.98 s

2.26 d, 2.92 br. s

2.45 s 6.22 t

2.52 s 6.23 t

7.20 d

7.21 d

Ϫ

7.47 d

(o)

7.57Ϫ8.32 m

[20 H]

²J_HHϭ 15.2

1.96 d, 2.03 d 2.28 d, 2.30 d,

²J_HHϭ 9.6

7.38Ϫ8.35 m 2.51 br. s

[18 H]

2.97 br. s

[6 H] m-CH₃

²J_HHϭ 15.2

2.08 d, 4.01 br. s

²J_HHϭ 14.8

2.24 s

2.39 s

Ϫ

7.44Ϫ8.42 m 6.09 pt, 6.43 pt

[20 H]

[4 H]

[c]

pyrrole-H

8

3.74 s

4.07 s

1.88 s

2.09 s

2.50Ϫ2.60m

2.58 s 6.19 t

2.24 s 6.25 t

7.16 d

7.23 d

7.44 d

(o)

7.44Ϫ8.28 m

[20 H]

7.53Ϫ8.24 m

[20 H]

9a

2.33 d, 2.89 d

²J_HHϭ 15.1

9b

4.02 s

4.01 s

1.99 d, 2.08 d 2.33 br. s, 2.81 d,

2.82 d

2.25 s 6.21 t

2.25 s 6.24 t

7.20 d

7.23 d

7.60 d

(o)

7.38Ϫ8.17 m 2.43 br. s

[18 H]

[6 H] m-CH₃

²J_HHϭ 9.8

²J_HHϭ 15.3

2.44 d, 2.94 d

²J_HHϭ 15.3

10

2.12 s

7.52Ϫ8.21 m

[20 H]

12^[e]

3.79 d^[f], 4.02 d^[f]1.89 d, 1.96 d 1.51 d, 2.49Ϫ2.64 m 2.59 s 6.30 t^[f]

7.33 d^[f]

[1 H]

8.98 d^[g]

[1 H]

7.60 d^[f]

[1 H]

8.11 d^[g]

[1 H]

7.51Ϫ8.25 m

[10 H]

[2 H]

²J_HHϭ 14.4

[1 H]

6.64 t^[g]

[1 H]

2

4.56 d^[g], 4.82 d^[g]J_HHϭ 9.6

[2 H]

²J_HHϭ 14.4^[f],

14.8^[g]

16a·PF₆

4.19 s

2.32 s

2.52 d, 2.99 d

2.15 s 6.26 t

2.62 s 6.24 t

7.36 d

7.24 d

7.54 d

7.48 d

7.35Ϫ7.63 m 2.15 br. s, 4.07 br. s

²J_HHϭ 15.2

[20 H]

[4 H] CH₂

5.56 m [1 H] allyl-CH

17

3.84 s

2.30 d, 2.68 d 1.90Ϫ1.99 m,

²J_HHϭ 9.6

2.36Ϫ2.47 m, 2.95 m

6.09Ϫ6.13 m 1.99 s [3 H]

[2 H], p-CH₃

7.09Ϫ8.22 m 2.79 s, 2.83 s

[20 H] [6 H] o-CH₃

7.40Ϫ8.18 m 0.67 s^[h]

[20 H] [3 H] Pd-CH₃

18^[e]

4.06 pt

²J_HHϭ 14.0

2.12 d, 2.46 d 2.00Ϫ2.31 m, 2.89 pt, 2.21 s 6.22 t

²J_HHϭ 9.6

7.17 d

(o)

3.09 pt

²J_HHϭ 14.2, 15.4

^[a]s ϭ singlet; d ϭ doublet; t ϭ triplet; m ϭ multiplet; br. s ϭ broad signal; pt ϭ pseudo triplet; (o) ϭ overlapped. ^[b]Coupling constants

[c]

3

[d]

[e]

in Hz. Coupling constant J_HHϭ 2.0 Hz. See Scheme 13 for numbering scheme of the pyrazole. Measuring temperature Ϫ40°C.

[f]

[g]

[h]

1

3

Noncoordinated CH₂pz group. Coordinated CH₂pz group. In H NMR spectra: δ ϭ 0.67 (dd, J_PHϭ 3.8 and 7.8 Hz).

2

²J_PPϭ 101 Hz, twist-PMes₂), 1.8 (d, J_PPϭ 101 Hz, twist-PPh₂),

91%) as a blue-violet, microcrystalline solid. Recrystallization from

3.1 (d, ²J_PPϭ 98 Hz, twist-PPh₂), 4.8 (d, ²J_PPϭ 95 Hz, chair-PPh₂) CH₂Cl₂/Et₂O afforded blue-violet crystals suitable for X-ray struc-

ppm, see Figure 7. 7d: Starting material 5d (560 mg). Yield 630 mg ture analysis. UV/Vis (CH₂Cl₂): λ (ε) ϭ 552 nm (200 ^Ϫ1·cm^Ϫ1),

(0.95 mmol, 95%) as an orange-coloured, microcrystalline solid.

³¹P NMR (CD₂Cl₂, Ϫ30°C): δ ϭ 9.8 (s, PPh₂) ppm. ³¹P NMR

(CD₂Cl₂, Ϫ100°C): δ ϭ 10.4Ϫ10.8 (m, PPh₂) ppm. For crystallo-

912 (110), 1007 (sh, 70). NMR: no NMR signals due to para-

magnetism. 11b: Starting materials 6a (440 mg) and [(dme)NiCl₂].

Yield 485 mg (0.88 mmol, 88%) as a violet, microcrystalline solid.

graphic data see Table 7; for further analytical data see Tables 11, UV/Vis (CH₂Cl₂): λ (ε) ϭ 527 nm (180 ^Ϫ1·cm^Ϫ1), 890 (100), 997

13, and 15.

(80). NMR: no NMR signals due to paramagnetism. 11c: Starting

[5e]

materials EtOCH₂C(CH₂PPh₂)(CH₂pz)₂

(455 mg) and [(dme)-

General Procedure for the Synthesis of 8, 11a؊c, 13, and 14: A

solution of the respective tripod ligand 5 or 6 (1.05 mmol) in THF

NiBr₂]. Yield 525 mg (0.80 mmol, 80%) as a blue-violet, microcrys-

talline solid. Recrystallization from CH₂Cl₂/Et₂O afforded two dif-

(20 mL) was added rapidly to a suspension of [(dme)NiCl₂] ferent kinds of crystals, both suitable for X-ray structure analysis,

(220 mg, 1.0 mmol) or [(dme)NiBr₂] (310 mg, 1.0 mmol), respec-

tively, in THF (20 mL). After stirring at 25°C for 12 h, all volatiles

were removed in vacuo. The residual solid was washed with 10-mL

portions of diethyl ether (3ϫ) and dried in vacuo. 8: Starting mate-

which were identified as 11c·0.5CH₂Cl₂(blue-violet) and the dimer

15 (red-brown). UV/Vis (11c, CH₂Cl₂): λ (ε) ϭ 550 nm (195



^Ϫ1·cm^Ϫ1), 913 (120), 1109 (sh, 50). NMR: no NMR signals due

to paramagnetism. 13: Starting materials 6b (525 mg) and [(dme)Ni-

rials 5a (565 mg) and [(dme)NiBr₂]. Yield 515 mg (0.68 mmol, 68%) Cl₂]. Yield 495 mg (0.78 mmol, 78%) as a blue-violet, microcrystal-

as a red, microcrystalline solid. Recrystallization from CH₂Cl₂/

line solid. Recrystallization from CH₂Cl₂/Et₂O afforded blue-violet

crystals suitable for X-ray structure analysis. UV/Vis (CH₂Cl₂): λ

(ε) ϭ 520 nm (100 ^Ϫ1·cm^Ϫ1), 579 (140), 974 (60). NMR: no NMR

signals due to paramagnetism. 14: Starting materials

Et₂O afforded red crystals suitable for X-ray structure analysis. ³¹

P

NMR (CD₂Cl₂, Ϫ30°C): δ ϭ 10.7 (s, PPh₂) ppm. 11a: Starting

materials 6a (440 mg) and [(dme)NiBr₂]. Yield 580 mg (0.91 mmol,

2234

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

FULL PAPER

Table 12. Chemical shifts (δ values) and coupling constants J in the ¹³C{¹H} NMR spectra of 2Ϫ6 in CHCl₃

Compd.^[a][b]CH₂N

CH₂O

CH₂P

OCH₃C_q

Pyrazole-C

C5^[c]

Aryl-C

Other

C4^[c]

C3^[c]

2b

55.3 d

79.7 d

34.4 d

Ϫ

44.6 d

Ϫ

129.0Ϫ138.9 m 108.7, 121.9

pyrrole-C

³J_CPϭ 10.1 ³J_CPϭ 9.6

¹J_CPϭ 16.6

35.0 m

²J_CPϭ 13.6

46.7 m

3a

3b

58.4 m

68.8 m

68.9 t

³J_CPϭ 8.8

68.6 dd

³J_CPϭ 8.3,

10.1

Ϫ

105.5 131.7 139.3 128.9Ϫ139.3 m

105.4 131.8 139.8 128.7Ϫ140.0 m 21.9 m-CH₃

58.4 t

35.5 m

45.5 t

³J_CPϭ 9.7

57.6 t

²J_CPϭ 11.5

46.3 dd

3c

31.9 dd, 34.6 dd

¹J_CPϭ 17.5, 19.3

³J_CPϭ 9.2, 10.1

Ϫ

105.4 131.6 139.7 128.6Ϫ143.4 m 21.2 d p-CH₃

⁵J_CPϭ 1.8

³J_CPϭ 8.7

²J_CPϭ 12.0,

15.6

23.7 d, 23.9 d o-CH₃

³J_CPϭ 13.8

105.5 131.8 139.7 128.8Ϫ140.1 m 26.8Ϫ35.1 m

cyclohexyl-C

3d

3e

58.7 t

69.1 t

26.8Ϫ35.1 m

Ϫ

44.2 t

³J_CPϭ 9.9

54.8 t

³J_CPϭ 8.6

67.9 t

²J_CPϭ 12.4

45.3 t

35.1 dd

Ϫ

128.9Ϫ139.5 m 108.3, 123.0

pyrrole-C

³J_CPϭ 8.1

³J_CPϭ 8.3

¹J_CPϭ 18.1,

³J_CPϭ 9.5

32.1 m

²J_CPϭ 11.1

4a

4b

54.9 m

55.2 d

³J_CPϭ 9.6

65.5 m

65.8 d

³J_CPϭ 10.0 ¹J_CPϭ 20.1

Ϫ

46.7 m

47.2 d

²J_CPϭ 15.1

105.6 132.3 140.0 128.9Ϫ139.8 m

105.7 132.0 139.9 130.9Ϫ143.0 m 21.2 p-CH₃

23.8 d o-CH₃

29.7 d

³J_CPϭ 13.6

5a

57.6 t

76.8 t

35.4 dd

58.3

44.3 t

105.5 131.5 139.4 128.7Ϫ140.0 m

³J_CPϭ 9.3

³J_CPϭ 8.6

¹J_CPϭ 18.5,

³J_CPϭ 9.5

35.2 m

²J_CPϭ 12.0

5b

5c

57.6 t

76.8 t

³J_CPϭ 8.5

77.1 m

58.3

58.5

44.3 t

105.4 131.5 139.3 128.5Ϫ140.0 m 21.8 m-CH₃

³J_CPϭ 9.2

57.6 t

²J_CPϭ 12.0

45.2 dd

32.6Ϫ34.7 m

105.4 131.4 139.3 128.5Ϫ143.1 m 21.2 p-CH₃

³J_CPϭ 9.2

²J_CPϭ 11.0,

15.6

23.7 d, 23.9 d

o-CH₃

³J_CPϭ 13.8

5d

55.3 t

76.6 t

35.0 dd

58.2

44.4 t

Ϫ

128.7Ϫ140.0 m 108.1, 123.0 pyrrole-C

³J_CPϭ 8.7

³J_CPϭ 8.3

¹J_CPϭ 19.3,

³J_CPϭ 11.0

32.0 d

²J_CPϭ 12.0

6a

6b

54.8 d

74.1 d

³J_CPϭ 8.1

74.2 d

58.6

58.8

45.6 d

105.5 132.2 139.8 128.8Ϫ139.9 m

³J_CPϭ 8.6

55.0 d

¹J_CPϭ 18.1

28.9 d

¹J_CPϭ 19.1

²J_CPϭ 12.1

46.1 d

105.5 132.0 139.6 130.7Ϫ143.1 m 21.2 p-CH₃

³J_CPϭ 10.6 ³J_CPϭ 9.6

²J_CPϭ 15.6

23.8 d o-CH₃

³J_CPϭ 14.0

^[a]All signals are singlets unless otherwise stated; d ϭ doublet; dd ϭ doublet of doublet; t ϭ triplet; m ϭ multiplet. ^[b]Coupling constants

[c]

in Hz. See Scheme 13 for numbering scheme of the pyrazole.

[5e]

CH₃C(CH₂pz)₃

(285 mg) and [(dme)NiBr₂]. Yield 425 mg NMR (CD₂Cl₂, Ϫ100°C): δ ϭ 14.9Ϫ15.8 (m), 16.6Ϫ17.1 (m) ppm.

12: Starting material 6a (210 mg). Yield 245 mg (0.41 mmol, 82%)

(0.87 mmol, 87%) as a blue, microcrystalline solid. Recrystalliza-

tion from CH₂Cl₂/Et₂O afforded blue and red-brown crystals, but as a yellow, microcrystalline solid. Recrystallization from CH₂Cl₂/

only the former were suitable for X-ray structure analysis. UV/Vis Et₂O afforded yellow crystals suitable for X-ray structure analysis.

(CH₂Cl₂): λ (ε) ϭ 550 nm (180 ^Ϫ1·cm^Ϫ1), 600 (230), 1004 (90).

³¹P NMR (CD₂Cl₂): δ ϭ 9.8 (s, PPh₂) ppm. For crystallographic

NMR: no NMR signals due to paramagnetism. For crystallo-

data see Tables 7 and 8; for further analytical data see Tables 11,

graphic data see Tables 7 and 8; for further analytical data see 13, and 15.

Tables 11, 13, and 15.

Synthesis of 10: A solution of the tripod ligand 5a (135 mg,

General Procedure for the Synthesis of 9a, 9b, and 12: A solution

of the respective tripod ligand 5 or 6 (0.5 mmol) in ethanol (15 mL)

was added rapidly to a suspension of [(η⁴-cod)PdCl₂] (145 mg,

0.5 mmol) in ethanol (10 mL). Within a few minutes the yellow

reaction mixture was clearing up. After stirring at 25°C for 12 h,

all volatiles were removed in vacuo. The residual solid was washed

with portions of diethyl ether (10 mL, 3ϫ) and dried in vacuo. 9a:

Starting material 5a (270 mg). Yield 265 mg (0.37 mmol, 74%) as a

colourless, microcrystalline solid. Recrystallization from CH₂Cl₂/

Et₂O afforded colourless crystals suitable for X-ray structure analy-

sis. ³¹P NMR (CD₂Cl₂): δ ϭ 15.8 (s, PPh₂) ppm. ³¹P NMR

0.25 mmol) in ethanol/THF (2:1; 15 mL) was added rapidly to a

suspension of [cis-(CH₃CN)₂PtCl₂] (85 mg, 0.25 mmol) in ethanol

(10 mL). Within a few minutes the reaction mixture was clearing

up and the platinum complex precipitated. After stirring at 25°C

for 12 h, all volatiles were removed in vacuo. The residual solid was

washed with portions of diethyl ether (10 mL, 3ϫ) and dried in

vacuo. Recrystallization from CH₂Cl₂/Et₂O afforded 150 mg

(0.19 mmol, 75%) of 10 as colourless crystals. ³¹P NMR (CD₂Cl₂):

1

δ ϭ Ϫ2.5 (s, with Pt satellites, J_PtPϭ 1720 Hz, PPh₂). ³¹P NMR

2

(CD₂Cl₂, Ϫ100°C): δ ϭ Ϫ3.2 (d, J_PPϭ 20 Hz, PPh₂), Ϫ2.5 (d,

²J_PPϭ 20 Hz, PPh₂). For further analytical data, see Tables 11, 13,

2

(CD₂Cl₂, Ϫ100°C): δ ϭ 15.8 (d, J_PPϭ 115 Hz, PPh₂), 15.9 (d,

and 15.

²J_PPϭ 115 Hz, PPh₂) ppm. 9b: Starting material 5b (280 mg). Yield

255 mg (0.34 mmol, 69%) as a pale yellow microcrystalline solid.

Synthesis of 16a·PF₆: Solid TlPF₆(2 equiv., 210 mg) was added, at

³¹P NMR (CD₂Cl₂): δ ϭ 15.8 [br. s, PPh₂, P(m-Tol)₂] ppm. ³¹P 0°C, to a suspension of 7a (200 mg, 0.3 mmol) in THF (50 mL) to

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

www.eurjic.org

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2235

R. Faissner, G. Huttner, E. Kaifer, P. Kircher, P. Rutsch, L. Zsolnai

Table 13. Chemical shifts (δ values) and coupling constants J in the ¹³C{¹H} NMR spectra of 7Ϫ18 in CH₂Cl₂

FULL PAPER

Compd.^[a][b]CH₂N

CH₂O

CH₂P

OCH₃C_q

Pyrazole-C

C5^[c]

Aryl-C

Others

C4^[c]

C3^[c]

7a

7b

7d

58.5

58.3

58.0

72.7

73.1

29.1

28.7 m

30.3

57.7 42.3

57.6 42.3

57.6 43.4

105.8 br. s 133.2 br. s 140.2 br. s 129.0Ϫ136.3 m

105.6

132.6

140.0

128.8Ϫ140.2 m 21.7, 21.8 m-CH₃

128.8Ϫ138.8 m 108.9, 122.6

pyrrole-C

Ϫ

8

9a

57.4

59.8 t

72.6

72.3 t

³J_CPϭ 5.2

72.3 br. s

26.4

30.7Ϫ31.5 m

57.7 42.6

57.4 43.9

105.5

105.8

131.5

131.7

139.8

140.1

128.7Ϫ139.8 m

128.8Ϫ136.2 m

³J_CPϭ 11.0

59.6 t

9b

30.7Ϫ31.4 m

29.9Ϫ30.8 m

57.5 43.8

57.5 43.9

58.2 45.2

57.5 43.6

105.8

131.6

140.0

128.8Ϫ138.9 m 21.6, 21.7 m-CH₃

128.8Ϫ136.1 m

³J_CPϭ 11.0

59.9

10

72.1 t

³J_CPϭ 5.1

68.6 br. s

105.8

131.7

140.1

³J_CPϭ 11.6

12

52.4 br. s^[d]

54.0 br. s^[e]

60.3 br. s

,

29.4 d

¹J_CPϭ 27.7

30.6-31.3 m

105.9^[e]

108.5^[d]

105.9

,

131.8^[e]

136.2^[d]

132.2

,

140.3^[e]

145.5^[d]

140.2

,

128.8Ϫ132.7 m

16a·PF₆

17

74.0 br. s

129.8Ϫ134.5 m 72.6 allyl-CH₂,

117.6 allyl-CH

127.2Ϫ140.3 m 20.0 p-CH₃

26.8 o-CH₃

128.6Ϫ140.1 m 14.5 dd Pd-CH₃

²J_CPϭ 6.0, 103.0

59.0 dd

74.6 dd

27.8 dd, 29.9 dd

58.0 42.5 br. s 105.6

57.3 44.2 br. s 105.8

131.4

131.6

139.6

139.7

³J_CPϭ 6.0, 10.5 J_CPϭ 5.5, 7.4 J_CPϭ 18.0, J_CPϭ 8.8

3

1

3

18

60.8 t

³J_CPϭ 10.6

72.8 t

³J_CPϭ 5.9

32.2 dd, 34.5 dd

¹J_CPϭ 27.6, J_CPϭ 9.8

3

[a]

All signals are singlets unless otherwise stated; d ϭ doublet; dd ϭ doublet of doublet; t ϭ triplet; m ϭ multiplet; (o) ϭ overlapped.

Coupling constants in Hz. See Scheme 13 for numbering scheme of the pyrazole. Coordinated CH₂pz group. Noncoordinated

[b]

[c]

[d]

[e]

CH₂pz group.

Table 14. Analytical data of ligands 2Ϫ6

Compd.

Formula

M [g/mol]

EI-MS [m/z (%)]

C_calcd./C_found

H_calcd./H_found

N_calcd./N_found

P_calcd./P_found

2b

3b

3c

3d

3e

4b

C₂₁H₂₂NOP

335.38

550.62

606.73

534.66

521.57

488.61

336 (100), 305 (39), 199 (57), 183 (66), 120 (97)

551 (28), 474 (100), 460 (76)

607 (15), 529 (5), 487 (100),369 (10), 337 (11)

534 (1), 452 (100), 183 (10)

521 (10), 444 (100), 199 (14), 183 (24)

489 (49), 473 (67), 407 (22), 369 (45), 269 (100),

250 (39)

75.21/75.33

74.17/74.25

75.23/75.46

71.89/71.67

75.99/75.98

71.29/72.00

6.61/6.95

6.59/6.88

7.31/7.98

8.29/8.15

6.38/6.63

7.63/8.43

4.18/3.61

5.09/4.89

4.62/4.40

5.24/5.10

2.69/2.49

11.47/10.74

9.24/n. d.

11.25/n. d.

10.21/n. d.

11.59/11.47

11.88/n. d.

6.34/n. d.

C₃₄H₃₆N₂OP₂

C₃₈H₄₄N₂OP₂

C₃₂H₄₄N₂OP₂

C₃₃H₃₃NOP₂

C₂₉H₃₇N₄OP

5a

5b

5c

5d

6a

C₃₃H₃₄N₂OP₂

C₃₅H₃₈N₂OP₂

C₃₉H₄₆N₂OP₂

C₃₄H₃₅NOP₂

C₂₄H₂₇N₄OP

536.59

564.64

620.75

535.60

418.47

536 (11), 459 (100), 183 (10)

73.87/73.98

74.45/74.71

75.46/75.50

76.24/76.11

68.88/69.19

6.39/6.39

6.78/7.07

7.47/7.65

6.59/6.58

6.50/6.68

5.22/5.26

4.96/4.84

4.51/4.49

2.62/2.54

13.39/12.77

11.54/11.71

10.97/n. d.

9.98/n. d.

11.57/11.50

7.40/n. d.

564 (18), 487 (100), 473 (77), 183 (14)

620 (2), 543 (2), 501 (100), 269 (10)

535 (8), 458 (100), 199 (10), 183 (13)

418 (100), 341 (82), 337 (52), 305 (37), 269 (59),

199 (52), 183 (44), 151 (36)

6b

C₃₀H₃₉N₄OP

502.64

502 (100), 487 (41), 421 (34), 383 (59)

71.69/71.74

7.82/8.06

11.15/11.02

6.16/6.18

yield a white precipitate of TlCl. After stirring the reaction mixture

at 0°C for 1 h, allylmagnesium bromide (0.35 mL of a 1  solution

in THF) was added dropwise. After stirring at 25°C for 10 h, the

precipitate was filtered off through 2 cm of Kieselguhr and all vol-

atiles were removed in vacuo. The orange-coloured residue was

washed with portions of diethyl ether (10 mL, 2ϫ) and then recrys-

complete precipitation the reaction mixture was cooled overnight

to Ϫ30°C and afterwards filtered. The resultant grey residue was

washed with portions of diethyl ether (10 mL, 2ϫ), dried in vacuo,

and recrystallized from CH₂Cl₂/Et₂O to give 140 mg (0.19 mmol,

64%) of 16b·PF₆as air-stable, colourless crystals suitable for X-

ray structure analysis. ¹H NMR and ¹³C NMR: due to dynamic

tallized from CH₂Cl₂/Et₂O to give 170 mg (0.22 mmol, 72%) of processes, no sharp signals could be detected. ³¹P NMR (CD₂Cl₂):

16a·PF₆·0.75CH₂Cl₂as air-stable, yellow crystals suitable for X-ray δ ϭ Ϫ144.2 (sept, J_PFϭ 710 Hz, PF₆^Ϫ), 11.5 (s, PPh₂) ppm. For

1

structure analysis. ³¹P NMR (CD₂Cl₂): δ ϭ Ϫ144.0 (sept, J_PF

ϭ

crystallographic data see Table 9; for further analytical data see

712 Hz, PF₆^Ϫ), 13.0 (s, PPh₂) ppm. For crystallographic data see Tables 11, 13, and 15.

Table 9; for further analytical data see Tables 11, 13, and 15.

Synthesis of 17: A solution of the tripod ligand 5a (270 mg,

Synthesis of 16b·PF₆:

EtOCH₂C(CH₂PPh₂)(CH₂pz)₂

(10 mL) was added rapidly to a suspension of [Pd(η³-C₃H₅)Cl]₂

A

solution of the tripod ligand

0.5 mmol) in toluene (15 mL) was added to a solution of [trans-

(PPh₃)₂Ni(Mes)Br] (390 mg, 0.5 mmol) in toluene (15 mL). After

stirring the orange-coloured reaction mixture at 25°C for 10 h, the

[5e]

(130 mg, 0.3 mmol) in EtOH

(55 mg, 0.15 mmol) in EtOH (10 mL). When a clear solution had solvent was removed in vacuo. The crude product was suspended

formed (after about 30 min), solid KPF₆(55 mg, 0.3 mmol) was in petroleum ether (20 mL). After filtration of the suspension, the

added and within a few minutes the allyl complex precipitated. For

residue was washed carefully with portions of petroleum ether

2236

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

tripod Ligands Containing Phosphane and Pyrazole Donors

Table 15. Analytical data of metal complexes 7Ϫ19

FULL PAPER

Compd. Formula

M [g/mol] FAB-MS [m/z (%)]

C_calcd./C_foundH_calcd./H_foundN_calcd./N_foundP_calcd./P_foundCl_calcd./Cl_found

7a

7b

7c

7d

8

C₃₃H₃₄Cl₂N₂NiOP₂666.18

664 (4), 629 (100), 594 (18),

459 (36), 409 (24), 364 (31), 351 (28)

692 (4), 657 (100), 622 (10), 487 (19), 60.55/60.28 5.52/5.58

59.50/59.14 5.14/5.34

4.21/4.07

4.04/3.90

3.73/3.56

2.11/2.15

3.71/3.44

3.92/3.79

9.30/8.94

8.92/8.86

8.26/n. d.

9.31/n. d.

8.20/n. d.

8.68/8.53

10.64/10.73

10.21/10.19

9.45/n. d.

C₃₅H₃₈Cl₂N₂NiOP₂694.24

C₃₉H₄₆Cl₂N₂NiOP₂750.35

C₃₄H₃₅Cl₂NNiOP₂665.19

C₃₃H₃₄Br₂N₂NiOP₂755.09

C₃₃H₃₄Cl₂N₂OP₂Pd 713.92

C₃₅H₃₈Cl₂N₂OP₂Pd 741.97

473 (16)

713 (50), 677 (100), 502 (59), 409 (85), 62.43/62.39 6.18/6.50

351 (42)

663 (4), 628 (100), 593 (18), 515 (35), 61.39/60.95 5.30/5.32

458 (34), 408 (15)

672 (69), 629 (54), 594 (17), 459 (25), 52.49/51.33 4.54/4.56

409 (15), 364 (18), 351 (15)

677 (100), 642 (17), 459 (77), 457 (50), 55.52/54.58 4.80/4.93

351 (59)

10.66/n. d.

21.16^[a]

/n. d.

9.93/10.00

9a

9b

10

705 (100), 670 (14), 487 (17)

801 (6), 766 (100), 731 (11), 634 (11), 49.39/49.50 4.27/4.55

459 (12)

56.66/56.32 5.16/5.13

3.78/3.64

3.49/3.35

8.35/8.44

7.72/7.35

9.56/9.52

8.83/9.20

C₃₃H₃₄Cl₂N₂OP₂Pt 802.58

11a

11b

11c

C₂₄H₂₇Br₂N₄NiOP 636.97

C₂₄H₂₇Cl₂N₄NiOP 548.07

C₂₅H₂₉Br₂N₄NiOP 651.00

555 (28), 476 (100), 341 (10), 291 (28), 45.25/45.16 4.27/4.33

246 (64), 185 (38)

511 (88), 476 (76), 341 (26), 291 (49), 52.59/52.63 4.97/4.96

246 (100), 185 (47)

569 (36), 490 (10), 431 (10), 355 (13), 46.12/45.56 4.49/4.55

327 (22), 305 (28), 281 (31), 246 (100)

8.80/8.68

4.86/4.89

25.09^[a]/24.85^[b]

12.94/13.05

10.22/10.19 5.65/5.67

8.61/8.44

4.76/4.72

24.55^[a]/25.70^[b]

12

13

C

₂₄H₂₇Cl₂N₄OPPd 595.80

₃₀H₃₉Cl₂N₄NiOP 632.23

559 (100), 524 (28), 339 (81)

595 (100), 559 (58), 502 (40), 488 (26), 56.99/56.88 6.22/6.27

435 (23), 383 (46)

407 (100), 328 (29)

635 (100), 594 (14), 409 (15), 364 (10) 52.24^[c]/52.39 4.83^[c]/4.88

578 (100), 422 (35), 353 (30) 46.39/46.08 4.73/4.48

792 (1), 673 (14), 594 (100), 409 (35), 63.50/63.32 5.71/5.73

364 (44)

48.38/47.99 4.57/4.61

9.40/9.17

8.86/8.94

5.20/n. d.

4.90/4.89

11.90/n. d.

11.22/11.21

14

C₁₄H₁₈Br₂N₆Ni

488.84

34.40/34.36 3.71/3.73

17.19/16.97

3.32^[c]/3.18

7.73/7.73

32.69^[a]/32.43^[b]

Ϫ

16a·PF₆C₃₆H₃₉F₆N₂NiOP₃781.32

16b·PF₆C₂₈H₃₄F₆N₄OP₂Pd 724.96

17

11.00^[c]/n. d.

8.54/n. d.

7.80/7.67

Ϫ

C

₄₂H₄₅BrN₂NiOP₂794.37

3.53/3.52

10.06^[a]/n. d.

18

C

₃₄H₃₇ClN₂OP₂Pd 693.50

692 (3), 677 (93), 657 (41), 642 (15),

565 (10), 457 (100), 351 (39)

58.89/58.60 5.38/5.60

4.04/3.99

8.93/8.54

5.11/5.10

19·PF₆C₅₁H₅₃F₆N₄NiOP₃1003.60

857 (32), 595 (98), 476 (100), 381 (42) 59.69^[d]/58.53 5.24^[d]/5.25

5.42^[d]/5.51

8.99^[d]/n. d.

Ϫ

[a]

[b]

[c]

[d]

Br_calcd.

.

Br_found

.

Calculated for 16a·PF₆·0.75CH₂Cl₂. Calculated for 19·PF₆·0.35CH₂Cl₂.

(10 mL, 3ϫ) to remove PPh₃, and dried in vacuo to give 285 mg

a precipitate of TlBr appeared immediately. The reaction mixture

(0.36 mmol, 72%) of 17 as a yellow, microcrystalline solid. ³¹P was stirred at 25°C for 3 h and then filtered through 2 cm of Kiesel-

NMR (CD₂Cl₂): δ ϭ Ϫ8.0 (d, ²J_PPϭ 41 Hz, PPh₂trans to Mes^Ϫ), guhr to remove the TlPF₆. The solvent was removed in vacuo and

23.2 (d, ²J_PPϭ 41 Hz, PPh₂trans to Br^Ϫ) ppm. For further analyti-

the crude product was suspended in petroleum ether (20 mL). After

filtration of the suspension, the residue was washed carefully with

portions of petroleum ether (15 mL, 3ϫ) to remove PPh₃, and dried

in vacuo. Recrystallization from CH₂Cl₂/Et₂O afforded 250 mg

cal data see Tables 11, 13, and 15.

Synthesis of 18: A solution of the tripod ligand 5a (270 mg,

0.5 mmol) in CH₂Cl₂(15 mL) was added to a solution of [(η⁴- (0.25 mmol, 50%) of 19·PF₆as yellow crystals suitable for X-ray

cod)PdMeCl] (135 mg, 0.5 mmol) in CH₂Cl₂(15 mL). After stirring structure analysis. H NMR and ¹³C NMR: due to dynamic pro-

1

the colourless reaction mixture at 25°C for 10 h, the solvent was

removed in vacuo. The crude product was suspended in petroleum

ether (20 mL). After filtration of the suspension, the resultant grey

residue was washed with portions of petroleum ether (15 mL, 3ϫ)

and dried in vacuo. Recrystallization from CH₂Cl₂/Et₂O afforded

cesses, no sharp signals could be detected. ³¹P NMR (CD₂Cl₂): δ ϭ

1

2

Ϫ144.0 (sept, J_PFϭ 712 Hz, PF₆^Ϫ), Ϫ5.8 (d, J_PPϭ 272 Hz,

PPh₃), 7.9 (d, ²J_PPϭ 280 Hz, PPh₃), 19.4 (d, ²J_PPϭ 280 Hz, PPh₂),

21.7 (d, ²J_PPϭ 272 Hz, PPh₂) ppm. For this compound a ³¹P NMR

pattern of two doublets corresponding to the two P donors is ex-

pected. Instead, two such patterns are observed (δ ϭ Ϫ5.8/21.7 and

7.9/19.4 ppm). The large coupling constants are in accord with a

295 mg (0.43 mmol, 85%) of 18 as colourless crystals suitable for

2

X-ray structure analysis. ³¹P NMR (CD₂Cl₂): δ ϭ Ϫ6.3 (d, J_PP

ϭ

48 Hz, PPh₂trans to Me^؊), 25.7 (d, J_PPϭ 48 Hz, PPh₂trans to trans position of the two P donors in each case. There are obviously

2

Cl^Ϫ) ppm. For crystallographic data see Table 9; for further analyti-

cal data see Tables 11, 13, and 15.

two isomers, and only the structure of the one characterized by X-

ray crystallography is known. Attempts to isolate the other isomer

have, so far, failed. For crystallographic data see Table 9; for further

analytical data see Tables 11, 13, and 15.

Synthesis of 19·PF₆: A solution of the tripod ligand 6a (210 mg,

0.5 mmol) in toluene (15 mL) was added to a solution of [trans-

(PPh₃)₂Ni(Mes)Br] (390 mg, 0.5 mmol) in toluene (15 mL). After

stirring the orange-coloured reaction mixture at 25°C for 10 h, the

solvent was removed in vacuo and the solid residue was dissolved

in THF (30 mL). Solid TlPF₆(175 mg, 0.5 mmol) was added and

Acknowledgments

We are indebted to the Deutsche Forschungsgemeinschaft and the

Fonds der Chemischen Industrie for financial support. One of us

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

www.eurjic.org

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2237

R. Faissner, G. Huttner, E. Kaifer, P. Kircher, P. Rutsch, L. Zsolnai

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Organic Chemistry is gratefully acknowledged.

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2238

 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org

Eur. J. Inorg. Chem. 2003, 2219Ϫ2238

Article Doi

Synthesis of tripod ligands containing mixed donor sets with phosphane and pyrazole donors - Bidentate chelate binding modes and dynamic behaviour of tripod ligands in d8-metal complexes (NiII, PdII, PtII)

DOI: 10.1002/ejic.200200535

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