Synthesis and reactivity of bis(diphenylphosphino)amine-bridged heterobimetallic iron-platinum μ-isonitrile and μ-aminocarbyne complexes Dedicated to Prof. Jacques Amaudrut on the occasion of his 75th birthday.

ACCEPTED MANUSCRIPT

Graphical abstract

Zwitterionic heterobimetallic

Ph PNPPh )Pt(PPh )] (L = CO, CNR) have been synthesized by deprotonation of the bridging dppa

aminocarbyne

complexes

[(OC) (L)Fe{µ-CN(R)R’}(µ-

2

3

ligand and their reactivity towards various electrophiles has been investigated. Thus, N-alkylated or

N-metallated aminocarbyne complexes such as the heterotrinuclear gold-amide complex

[

(OC) Fe{µ-CN(Me)xylyl}{µ-Ph PN(AuPPh )PPh }Pt(PPh )][OSO CF ] have been obtained.

3 2 3 2 3 2 3

Highlights

•

Heterobimetallic isonitrile and µ-aminocarbyne Fe-Pt complexes have been synthesized.

The bonding mode of the CNR ligand (bridging vs. terminal) depends on the σ-donor/π-

acceptor propensity of R.

•

Regioselective substitution of PPh at the Pt center.

3

Zwitterionic compounds were obtained by deprotonation of the dppa ligand.

Heterotrimetallic aminocarbynes were characterized by multinuclear NMR and X-ray

diffraction.

1

Synthesis and Reactivity of Bis(diphenylphosphino)amine-bridged

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Heterobimetallic Iron-Platinum µ-Isonitrile and µ-Aminocarbyne Complexes

*

[a]

* [a]

[a]

Michael Knorr

a]

, Isabelle Jourdain

[b]

, Ahmed Said Mohamed,

[b]

Abderrahim Khatyr

[

,

Stephan Koller , Carsten Strohmann

th

Dedicated to Prof. Jacques Amaudrut on the occasion of his 75 birthday

a

Institut UTINAM UMR CNRS 6213, Université de Franche-Comté,

Faculté des Sciences et des Techniques, 16, Route de Gray, 25030 Besançon, France

b

Institut für Anorganische Chemie der Technischen Universität Dortmund, Otto-Hahn-Strasse 6,

4

4227 Dortmund, Germany

ABSTRACT

Reaction of [(OC) Fe(µ-CO)(µ-dppa)Pt(PPh )] (1) (dppa = bis(diphenylphosphino)amine) with

3

various isonitriles in a 1:1 or 1:2 ratio yields the isonitrile-bridged compounds [(OC) Fe(µ-CN-

3

R)(µ-dppa)Pt(PPh )] (2) and [(OC) (RNC)Fe(µ-CN-R)(µ-dppa)Pt(PPh )] (3), respectively.

3

2

3

However, addition of tert-butylisonitrile to 1 affords the carbonyl-bridged complex [(OC) (tert-

2

BuNC)Fe(µ-CO)(µ-dppa)Pt(PPh )] (2g). Upon treatment of [(OC) Fe(µ-CN-o-anisyl)(µ-

3

dppa)Pt(PPh )] (2b) with SO , the µ-CNR ligand is chased from its bridging position to give the

3

2

sulfur dioxide-bridged compound [(OC) (o-anisylNC)Fe(µ-SO )(µ-dppa)Pt(PPh )] (4). These

2

3

compounds are converted to the µ-aminocarbyne salts [(OC) (L)Fe{µ-CN(R)R’}(µ-

2

+

dppa)Pt(PPh )] (5 R’ = Me, Et) by N-alkylation using [Me O][BF ] or ethyl triflate as

3

4

electrophiles. In function of the sterical crowding exerted by µ-aminocarbyne groups, two

stereoisomers can be formed. Upon addition of P(OMe) or tert-BuNC to 5, no carbonyl

3

substitution occurs. Instead the Pt-bound PPh ligand is replaced by L’ in a regioselective manner to

3

give [(OC) (L)Fe{µ-CN(Me)R}(µ-dppa)Pt(L’)][BF ] (5e, 5f, 5g). Deprotonation of the N-H

2

4

function of the bis(diphenylphosphino)amine ligand of salts 5 by KSi(OMe) or KH produces the

3

zwitterionic compounds [(OC) (L)Fe{µ-CN(R)R’}(µ-Ph PNPPh )Pt(PPh )] (6). The latter react

2

3

with various organic and inorganic electrophiles to produce the N-alkylated or metallated

+

aminocarbyne complexes [(OC) (L)Fe{µ-CN(R)R’}{µ-Ph PN(E)PPh }Pt(PPh )] (7: E = Me, 8: E

2

3

=

AuPPh , CuAsPh , CuPPh HgMe). The molecular structures of 2c, 3b, 5b, 8a and 8b have been

3 3 3,

determined by X-ray diffraction studies.

Keywords: Heterobimetallic complexes / Isonitrile complexes / Aminocarbyne complexes / Iron /

Platinum

2

Corresponding author. Tel.: + [33] 3 81 66 62 70; Fax : + [33] 3.81.66.55.04

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E-mail addresses: michael.knorr@univ-fcomte (M. Knorr)

1. Introduction

The use of bis(diphenylphosphino)methane (dppm) as short-bite ligand to assemble homo- and

heterodinuclear complexes is documented in a plethora of articles and even some reviews deal on

the coordination chemistry of dppm [1]. Although the first examples on the use of the related

ligand bis(diphenylphosphino)amine (dppa) have been reported in the seventies, [2] considerably

less work on the synthesis and reactivity of heterodinuclear and heterotrinuclear systems spanned

by dppa are documented. Some selected examples are [(OC) Mo(µ-dppa) RhCl(CO)] [3],

3

2

[

(C F ) Pd(ꢀ-dppa) Ag][ClO ]

[4]

[(OC) Fe(µ-dppa)ReBr(CO) ]

[5a],

[(OC) Fe{µ-

3

6

5 2

2

4

Si(OMe) (OMe)}(µ-dppa)Pd(I)] [5b], [(OC) Fe(µ-dppa)Pd(CH CH C(=O)Me)][BF ] [5c],

2

4

2

4

[

Cp(PPh )RuCl(µ-dppa)AuCl] [6], [(OC) Fe(ꢀ-dppa){ꢀ-C(C H CF -o)C═C(H)}Pt(PPh )] [7],

3 3 6 4 3 3

(Cp)Ru(ꢀ-CO) (ꢀ-dppa)MCl ] (M = Rh, Ir) [8], and [Cp(OC) Mo(µ-dppa)Pt(CO)Mo(CO) Cp]

2

3

10]. With the objective to combine our research interest on heterobimetallic complexes bearing

bridging isonitrile ligands, we have reported several years ago on the synthesis of the carbonyl-

bridged complex [(OC) Fe(µ-C=O)(µ-dppa)Pt(PPh )] (1) and its reactivity towards aromatic

3

isonitriles leading to a series of [(OC) Fe(µ-CN-Ar)(µ-dppa)Pt(PPh )] complexes [11]. We have

3

also demonstrated that the latter can be converted to cationic aminocarbyne complexes

+

[

(OC) Fe{µ-C=N(E)Ar}(µ-dppa)Pt(PPh )] by addition of electrophiles E on the basic N-atom of

3

the bridging isonitrile ligand. Since heterometallic µ-aminocarbyne complexes are still very

scarce, we have since our first short report investigated more in detail the synthetic access,

structural features and reactivity of this species. Another objective of this paper is the exploration

of the possibility to use the presence of the dppa-bridge to construct heterotrimetallic

aminocarbyne complexes. The synthesis of these heterotrimetallic systems, their characterisation

by multinuclear NMR studies and X-ray diffraction is presented in the second part of this article.

2. Results and Discussion

2.1. Synthesis of Fe-Pt Mono- and Bis(isonitrile) Complexes

In a manner similar as already described for the preparation of complexes [(OC) Fe(µ-CN-

3

xylyl)(µ-dppa)Pt(PPh )] (2a) and [(OC) Fe(µ-CN-o-anisyl)(µ-dppa)Pt(PPh )] (2b), [11] reaction of

3

[

(OC) Fe(µ-CO)(µ-dppa)Pt(PPh )] (1) with the aliphatic benzylisonitrile in a 1:1 ratio gives cleanly

3 3

within 10 min the isonitrile-bridged compound [(OC) Fe(µ-CN-benzyl)(µ-dppa)Pt(PPh )] (2c),

3

isolated in 88% yield (Scheme 1). The isonitrile ligand adopts also a bridging bonding mode after

3

stoichiometric addition of isocyanomethylacetate and p-tosylmethylisonitrile affording

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[

(CO) Fe{µ-CN-CH C(=O)OMe}(µ-dppa)Pt(PPh )] (2d) and [(CO) Fe{µ-CN-CH SO p-Tol}(µ-

3 2 3 3 2 2

dppa)Pt(PPh )] (2e), respectively. The crystal structure of 2c is shown in the Supporting

3

1

Information (Figure S1). Exemplarily for these series 2, the P{ H} NMR spectrum of 2e is

depicted in Figure 1, the NMR data for all complexes are presented in Table 3.

1

P

2

P

3

P

31

1

Fig. 1. P{ H} NMR spectrum of 2e recorded in CDCl at 298 K.

3

4

H

N

H

N

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^P^P^h2

^P^P^h3

N

PPh₂

PPh

2

Ph P

2

^P^h2^P

Ph P

2

N

^P^P^h3

Pt

^P^P^h3

C

Pt

C

Fe

O

Fe

O

Fe

CO

C

O

CO

C

O

C

N

3

b

3a

3

c

Bz N C

CO

Di N C

2 CO

-

Xylyl N C

CO

-

H

N

H

N

^P^P^h2

^P^P^h3

PPh₂

Ph P

2

Ph P

Ph

2

3

P

2

Bz N C

Xylyl N C

Pt

PPh

PPh₃

3

Pt

(

OC) Fe

3

(

OC) Fe

(OC)

Fe

3

CH Cl

CH Cl₂

2

C

-

CO

C

- CO

C

N

1

O

N

C

2a

2

c

N

O

MeO

O

^C^H2

t-Bu N C

S

C-CH N C

2

Tol

- CO

O

- CO

-

CO

H

N

H

N

PPh₂

^P^P^h2

PPh₂

PPh₃

t-Bu

^P^h2^P

Ph P

2

PPh₃

N

PPh₃

Pt

C

(

OC) Fe

(OC)

Fe

3

Fe

CO

C

O

C

N

3

d

2

e

2d

O

S O

Tol

MeO

O

Scheme 1. Syntheses of heterodinuclear mono- and bis(isonitrile) complexes

The reaction becomes more complicated when using stronger electron-donating aliphatic isonitriles.

Addition of n-butylisonitrile to 1 produces in almost quantitative yield the substitution product

31

[

(CO) Fe(µ-CN-Bu-n)(µ-dppa)Pt(PPh )] (2f), which has been isolated as a yellow solid. The P

3 3

NMR spectrum recorded at 243 K exhibits chemical shifts and coupling constants quite comparable

with those of 2e illustrated in Figure 1. However, at 298 K two species are detectable in an

approximate 60:40 ratio. The spectroscopic data of the first set correspond to those of the 243 K

2

+3

spectrum with a J(P-P) coupling of 180 Hz between the two dppa phosphorous atoms, the second

2

+3

set appears down-field shifted with respect to the first one with a J(P-P) coupling of 213 Hz.

3

1

Overall the P data of the second set are quite similar to those of the carbonyl-bridged precursor 1.

-1

The IR spectrum in solution exhibits a broadened ν(C=Ν) vibration at 1694 cm stemming from

-1

the bridging isonitrile ligand, but there is also a further absorption at 2143 cm characteristic for a

5

terminal isonitrile. We conclude that there is a temperature-dependent equilibrium between a µ-

ACCEPTED MANUSCRIPT

CNR isomer [(CO) Fe(µ-CN-Bu-n)(µ-dppa)Pt(PPh )] (2f) and an isomeric µ-CO species 2f’ as

3

shown in Scheme 2.

H

N

PPh₂

PPh₃

t-Bu

Ph P

2

N

t-Bu N C

CO

Pt

1

C

-

Fe

C

O

CO

C

2

g

n-Bu N C

CO

O

-

H

N

H

^P^P^h2

N

PPh₂

n-Bu

Ph P

2

Ph P

2

PPh₃

N

O

Pt

^P^P^h3

C

Pt

C

Fe

C

CO

C

O

CO

C

O

2

f

2f'

minor

N

O

major

n-Bu

Scheme 2. Reactivity of 1 towards n-butyl and t-butyl isonitrile

This hypothesis is supported by the observation that after addition of a stoichiometric amount of

tert-butylisonitrile the µ -CO complex [(OC) (tert-BuNC)Fe(µ-CO)(µ-dppa)Pt(PPh )] (2g) was

2

3

formed. In this orange-colored microcrystalline solid, the isonitrile ligand adopts a terminal

bonding mode orthogonal with respect to the Fe-Pt bond, which is bridged by a µ -carbonyl ligand

2

The bonding situation is evidenced from the IR spectrum, which displays in addition to a broadened

-1

ν(C=Ο) vibration at 1735 cm an intense ν(C≡N) absorption at 2123 cm stemming from the

-1

terminal CNR ligand. The presence of two further strong ν(CΟ) absorptions at 1950 and 1909 cm

proofs that the CNR ligand is bound orthogonal to the metal-metal axis. In the alternative case of

two trans-arranged terminal carbonyls only one band should have been observed. Compared to the

position of ν(C=Ο) band of precursor 1, that of 2f is shifted to lower frequency due to the electron-

-1

donating character of the tert-butylisonitrile ligand (1760 vs. 1735 cm ).

Of course the question arises, why tert-BuNC prefers to adopt a terminal bonding mode rather than

a bridging one. A crystal structure of the first bimetallic example of a µ-CNR complex,

[

Cp(CO)Fe(µ-CNxylyl)(µ-CO)FeCp(CO)], revealed a bridging bonding mode for xylylNC ligand

Chart 1) [12]. Some years later, Cotton and Adams studied the fluxional behavior of the tert-BuNC

(

derivative and established crystallographically a terminal bonding mode for [Cp(CO)Fe(tert-

BuNC)(µ-CO) FeCp(CO)] [13]. To explain this finding, the authors advanced steric arguments.

2

6

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Chart 1

However, we are more in favor for a rationalization based on an electronic argumentation. In

these electron-rich Fe-Pt complexes, a strong π-acceptor ligand such as µ-CO, µ-SO (see below) or

2

µ-CNR with aromatic or moderately electron-donating R group can compensate the electron-

richness by back-bonding. However in the case of tert-BuNC, the strong electron-donating +I effect

of the t-Bu group may considerably weaken the back-bonding propensity of this isonitrile, so that

finally a µ-CO is more efficient as π-acceptor. Furthermore, our X-ray structure determination of

the µ-vinylidene complex [(CO) Fe{µ-C=C(H)tBu}(µ-dppm)Pt(PPh )] demonstrates that a t-butyl

3

group is able to adopt a bridging position without causing sterical hindrance [14].

Conducting the reaction of 1 in CH Cl solution in the presence of 2 equivalents of RNC, or

2

reacting 2a,c with one further equivalent of RNC afforded the bis(isonitrile) complexes

(OC) (xylylNC)Fe(µ-CN-xylyl)(µ-dppa)Pt(PPh )] (3a) and [(OC) (BzNC)Fe(µ-CN-Bz)(µ-

[

2

3

2

dppa)Pt(PPh )] (3b), respectively. Addition of the di(isonitrile) ligand 1,2-bis(2-

3

isocyanophenoxy)ethane (diNC) to 1 results in formation of complex 3c, in which one isonitrile

group is bridging and the second one is ligated in a terminal manner on the iron center, thus

forming a 13-membered macrocycle. We also succeeded to synthesize the mixed bis(isonitrile)

complex [(OC) (tert-BuNC)Fe(µ-CN-xylyl)(µ-dppa)Pt(PPh )] (3d) by reacting 2a with 1

2

3

equivalent of tert-BuNC. In the case of series 3, the coordination of the terminal CNR ligand in an

orthogonal position relative to the metal-metal bond can be deduced from the IR spectra, which

shows two ν(CO) stretches of approximate equal intensities characteristic for a cis-arrangement of

the two carbonyl ligands of the Fe(CO) unit [15]. In addition, two ν(C≡N) vibrations due to the

2

terminal and bridging isonitrile ligands are found in the IR spectra. For example, the terminal tert-

-1

BuNC ligand of 3d gives rise to an adsorption at 2122 cm , whereas the broadened band at 1652

-1

cm is attributed to the bridging xylylNC ligand. Compared to complex 2a, the position of the latter

absorption is shifted to ca. 19 wavenumbers to lower frequencies. This is probably due to the

additional electron donating effect of the second terminal CNR ligand, which is partially

compensated by back-bonding in π*-orbitals of the µ -CNR ligand, thus weakening the C=N bond

2

1

[

16]. A H NMR investigation of 3a at variable temperature revealed the occurrence of a dynamic

behavior of one xylylisonitrile ligand (Figure S2). At room temperature the methyl groups of each

7

xylylNC ligand appear as a singlet at δ 1.82 and 2.09, the later resonance being somewhat

ACCEPTED MANUSCRIPT

broadened. Progressive lowering of the temperature causes further broadening and coalescence is

reached at 273 K. Below this temperature, a splitting of this signal occurs. Finally, two well-

resolved singlets are observed at 243 K. We attribute these two singlets to the methyl groups of the

bridging xylylNC ligand. Most probably, this phenomenon is a consequence of a hindered rotation

around the Ar-N bond due to steric effect. An exchange between bridging and terminal CNR ligand

has been discussed for other bimetallic systems [13] [17-21], but we exclude this possibility for 3a,

since the resonance due to the two methyl groups of the terminal xylylNC ligand are not involved

in this dynamic behavior.

Crystal structure of [(CO) (BzNC)Fe(

µ

-CN-Bz)(

and selected bond length and angles of 3b are presented in Figure 2. Suitable crystals of

•0.5CH Cl were grown from CH Cl /hexane. The structural parameters may be compared with

µ-dppa)Pt(PPh )] (3b). The structural features,

2

3

3b

2

those of the complex [(OC) Fe(µ-CN-Bz)(µ-dppa)Pt(PPh )] (2c) shown in Fig. S1. The

3

replacement of one CO ligand by a second terminal xylylNC ligand hardly affects the Fe–Pt

distance [2.5425(4) vs. 2.5741(13) Å]. The µ -isonitrile ligand is symmetrically ligated between the

2

two metal centers, the Fe–C(1) and Pt–C(1) distances being 2.000(9) and 1.998(10) Å. Both the

length of the C(1)=N bond [1.259(12) vs. 1.233(3) Å)] and the inclination C(1)–N–C(12) [120.8(9)

vs. 122.2(2)°] correspond to that of 2c. Also the bending of the benzyl group towards the carbonyl

iron moiety is identical. The perpendicular disposition of the terminal benzylisonitrile deduced

from the IR data is confirmed by this crystallographic study, the angle Pt–Fe–C(3) being 91.4(4)°.

As expected for a terminal coordination, the C(3)–N(3)–C(4) array is almost linear (172.6(12)°),

the presence of a C≡N triple bond is reflected by the short C(3)–N(3) distance of 1.175(15) Å.

8

ACCEPTED MANUSCRIPT

Fig. 2. Perspective view of 3b showing the atom-labelling scheme. Hydrogen atoms and the CH Cl

2

molecule have been omitted for clarity. Selected distances (Å) and angles (°): Fe–Pt 2.5741(13), Fe–P(1)

.228(2), Pt–P(2) 2.295(2), Pt–P(3) 2.269(2), Fe–C(1) 2.000(9), Fe–C(2) 1.713(11), Fe–C(3) 1.834(12), Fe–

2

C(11) 1.730(11), Pt–C(1) 1.998(10), C(1)–N(1) 1.259(12), C(3)–N(3) 1.175(15), N(1)–C(12) 1.443(14),

N(3)–C(4) 1.425(15), C(11)–O(2) 1.190(15), C(2)–O(1) 1.18(14), P(1)–N(2) 1.703(8), P(2)–N(2) 1.697(7);

P(1)–Fe–Pt 91.33(7), P(2)–Pt–Fe 97.94(7), P(3)–Pt–Fe 148.58(7), P(3)–Pt–P(2) 113.36(8), Pt–C(1)–Fe

8

0.2(4), C(2)–Fe–Pt 83.2(4), C(11)–Fe–Pt 157.9(4), C(3)–Fe–Pt 91.4(4), C(1)–Pt–P(3) 99.0(3), C(1)–Pt–

P(2) 147.6(3), C(1)–Fe–P(1) 140.7(3), N(3)–C(3)–Fe 176.5(11), C(3)–N(3)–C(4) 172.6(12), N(3)–C(4)–

C(5) 111.9(11), P(1)–N(2)–P(2) 122.4(4), C(1)–N(1)–C(12) 120.8(9).

9

Table 1

Crystallographic and refinement data for 3b, 5b, 5d and 8a

ACCEPTED MANUSCRIPT

3

b•CH Cl

5b

5d•CH Cl •Et O

8a

2

CCDC number

Formula

1031961

1031962

1031963

1031964

C H Cl Fe N C H BF FeN O C H BCl F FeN C H AuF FeN

1

21 102

2

6

54 46

4

2

3

64 69

2

4

3

74 62

3

2

O P Pt

P₃Pt

O P Pt

1429.78

293(2)

O P PtS

1736.10

173(2)

4

6

2

3

6 4

-1

Formula weight [gꢁmol ] 2462.69

T [K]

1201.59

173(2)

Crystal size [mm]

Crystal system

Space group

a [Å]

b [Å]

c [Å]

α [°]

β [°]

γ [°] ₃

V [Å ]

0.20 x 0.10 x 0.10 0.30 x 0.20x 0.20 0.30 x 0.20 x 0.20 0.30 x 0.20 x 0.10

orthorhombic

monoclinic

triclinic

P1;¯ (2)

12.57(4)

13.32(4)

21.67(6)

77.7(2)

88.3(3)

70.7(2)

3343(18)

2

monoclinic

Pna2 (33)

P2 /c (14)

P2 /n (14)

1

23.024(5)

11.256(2)

21.535(4)

90

11.732(2)

20.671(4)

21.063(4)

90

90.80(3)

90

16.8304(5)

20.7199(4)

21.8066(6)

90

109.644(3)

90

5581.0(19)

2

5107.5(16)

4

7162.0(3)

4

Z

-3

ρ calc [gꢁcm ]

ꢀ

1.465

1.563

1.420

1.610

-1

[mm ]

2.942

3.173

2.514

4.370

F (000)

2468

2392

1444

3416

θ range [°]

2.01 – 26.00

2.00 – 25.00

–13 ≤ h ≤13

–24 ≤ k ≤ 22

–25 ≤ l ≤ 25

35977

1.73 – 24.00

–14 ≤ h ≤ 14

–14 ≤ k ≤ 15

0 ≤ l ≤ 24

10469

2.20 – 27.00

–21 ≤ h ≤ 21

–26 ≤ k ≤ 26

–27 ≤ l ≤ 27

79775

–

28 ≤ h ≤ 27

–13 ≤ k ≤ 13

26 ≤ l ≤ 26

31772

0894

R_i_n_t= 0.1009)

Index ranges

–

collected reflections

1

(

8983

10469

15595

(R_i_n_t= 0.0510)

independent reflections

(

Rint = 0.1899)

(

R_i_n_t= 0.0000)

Data / Restraints /

Parameters

1

0894 / 1 / 659

8983/0/624

1.023

10469 / 1 / 756

1.057

15595 / 0 / 841

1.006

Goodness-of-fit on F2

largest diff peak and

1.015

-3

3.570 and –1.813 1.324 and –2.229 3.850 and –3.493 2.782 and –1.232

hole [e Å ]

R1 = 0.0601

wR2 = 0.1591

R1 = 0.0674

wR2 = 0.1669

R1 = 0.0800,

wR2 = 0.1979

R1 = 0.1168

wR2 = 0.2343

R1 = 0.0699,

wR2 = 0.1791

R1 = 0.0811

wR2 = 0.1893

R1 = 0.0323,

wR2 = 0.0670

R1 = 0.0584

wR2 = 0.0695

final R indices [I>2σ(I)]

R indices (all data)

The tendency of strong π-acceptor ligands to occupy in these Fe-Pt systems a bridging position in

order to compensate a high electron density by π-back-bonding is also confirmed by treatment of

2

b with SO . Theoretical and experimental studies have shown that sulfur dioxide as bridging

2

ligand may exert a π-acceptor propensity exceeding even that of carbon monoxide [22]. This

explains why, after short bubbling of SO in a dichloromethane solution of 2b, the µ-isonitrile

2

ligand is chased away from his bridging position and a µ-SO molecule occupies in [(OC) (o-

2

anisylNC)Fe(µ-SO )(µ-dppa)Pt(PPh )] (4) its former place with concomitant CO extrusion

2

3

(Scheme 3).

1

0

H

N

H

N

OMe

PP

A

h

CCEPTED MANUSCRIPT

2

PPh₂

Ph P

2

Ph P

2

N

^P^P^h3

PPh₃

O

Pt

C

SO₂

Pt

C

Fe

CO

C

CO

S

O

C

O

CH Cl₂

2

-

CO

O

N

2

b

O

4

OMe

Scheme 3. Formation of a heterodinuclear µ-SO complex

2

3

1

195

Both the P- and

Pt NMR data indicate that the metal-metal bonded core skeleton of 4

-1

remained intact (Table 3). From the position of the ν(C≡N) vibration at 2125 cm it is evident,

that the isonitrile is now ligated in a terminal manner. Characteristic for SO in a bridging bonding

2

mode is the presence of an intense symmetric and an asymmetric ν(SO)-vibration in the range

-1

between 1190-1050 cm . For example, the occurrence of two vibrations at 1189 and 1049 cm

has been reported for [(OC)(Rh(µ-SO )(µ-S)(µ-dppm) Mn(CO) )], and we observed previously

2

-1

two vibrations at 1183 and 1044 cm in the IR spectrum of [(OC) W(µ-SO )(µ-dppa)Pt(PPh )]

4

2

3

-1

[

23]. Therefore the two strong absorptions observed at 1097 and 1026 cm are attributed to the

ν(SO) stretches of 4.

2.3. Preparation and reactivity of cationic N-alkylated aminocarbyne complexes.

In an analogous manner to the preparation of the µ-aminocarbyne complex [(OC) Fe{µ-

3

CN(Me)xylyl}(µ-dppa)Pt(PPh )][BF ] (5a), the cationic derivative [(OC) Fe{µ-CN(Me)Bz}(µ-

3

4

3

dppa)Pt(PPh )][BF ] (5b) was obtained by electrophilic addition on the basic nitrogen atom of the

3

4

µ-CNR ligand using the Meerwein salt [Me O][BF ] or methyl triflate as the alkylating agent

3

4

(Scheme 4). Note that these compounds may alternatively be considered as alkylated iminium salts

A (Chart 2) [24], but in line with the group of Busetto et al. [25], we prefer a description as µ-

aminocarbyne complexes C (see also the discussion concerning the isomerization of 5h below) [17,

26, 27] with an important contribution of form B.

Chart 2

1

N-methylation allowed also to convert the labile mixed bis(isonitrile) complex 3d into the stable

ACCEPTED MANUSCRIPT

salt 5d. Note that the terminal tert-BuNC ligand does not react even with an excess of the alkylating

agent (Scheme 4).

H

N

^P^P^h2

^P^P^h3

N

PPh₂

^P^h2^P

Ph P

2

O

Pt

[Me O][BF ]

O

^P^P^h3

C

3

4

Pt

C

Fe

C

CO

Bz

CH Cl

298 K

2

CO

O

C

O

C

BF₄

N

Me

Bz

2

c

5

b

H

N

PPh₂

^P^P^h2

t-Bu

Ph P

^P^h2^P

2

N

PPh₃

^P^P^h3

Pt

C

Fe

O

Fe

O

CO

C

O

C

O

C

BF₄

^B^F4

N

Me

5

d

5

c

H

N

H

N

H

PPh₂

PPh₃

PPh₂

PPh₃

N

PPh₂

PPh₃

Ph P

2

N

O

Pt

C

Pt

C

Fe

CO

C

O

C

O

C

O

C

5h

Et

C

5

h'

5i

N

Et

Scheme 4. Preparation of µ-aminocarbyne complexes 5 by N-alkylation.

A priori two isomeric forms are conceivable with the methyl group orientated towards the platinum

1

31

195

centre or alternatively towards the Fe(CO) fragment. All H, P and Pt NMR data indicate the

n

formation of just one isomer (Table 3). To unambiguously ascertain the stereochemistry around the

µ₂-aminocarbyne ligand, X-ray diffraction studies on 5b and 5d were undertaken.

Crystal structures of [(OC) Fe{

µ-CN(Me)Bz}(µ-dppa)Pt(PPh )][BF ] (5b) and [(OC) (tert-

3 4 2

3

BuNC)Fe{

Suitable single-crystals of yellow 5b were grown from CH Cl /Et O. The structure depicted in

µ-CN(Me)xylyl}(µ-dppa)Pt(PPh )][BF ] (5d).

3

4

2

Figure 3 shows that the µ-aminocarbyne ligand symmetrically bridges [Fe–C(1) 1.905(13), Pt–C(1)

.989(15) Å] the two metal centers, the separation of which, 2.5182(16) Å, is indicative of the

1

2

presence of a metal-metal bond. Due to steric factors, only the isomer with the benzyl group

ACCEPTED MANUSCRIPT

oriented towards the iron center is formed. The short bond length between C(1) and N(1) of

1.330(17) Å reflects the partial C=N double-bond character of the µ-aminocarbyne unit, which,

therefore may alternatively be considered as a dimetallated iminium salt ligand (Chart 2). To date,

to the best of our knowledge, only one other example of a heterobimetallic µ-aminocarbyne

complex has been structurally described. A C–N distance of 1.29(2) Å was observed for this

tungsten-gold [(CO) (Cp)W{µ-CN(Et)Me}Au(C F )] complex bridged by a CN(Et)Me ligand [25].

2

6 5

A separation of 2.938 Å between the N atom of the dppa ligand in 5b and the F(1) atom of the

tetrafluoroborate counter ion suggests the presence of a hydrogen-bonding interaction {d

H(2)····F(1) 2.109 Å}. A comparable N···F distance of 2.941 Å has been reported for

t

[

Ru (CO) (µ-NO)(µ-H)(µ-P Bu )(µ-dppa)][BF ] [28], a weaker interaction with the N–H proton

2

4

2

4

d(N···F) = 3.105 Å] was found for [(OC) Fe(µ-dppa)Pd{CH CH C(=O)Me}][BF ] [5c, 29-31].

4

2

4

In the structure of 5d, which contains both a CH Cl and Et O molecule of crystallisation, the

2

methyl group of the aminocarbyne ligand points again towards the PtPPh moiety (Figure 4). The

3

C(1)–N(1) bond length of 1.265(12) Å is even shorter than that of 5b. An intermolecular hydrogen

-

bond between the BF counter ion and the N-H group of the dppa ligand is also encountered for

4

this salt {d[N(2)····F(1)] 2.987 Å; H(2)····F(1) 2.163 Å}.

Fig. 3. Perspective view of 5b showing the atom-labelling scheme. Apart from H(2), all hydrogen atoms

have been omitted for clarity. Selected distances (Å) and angles (°): Fe–Pt 2.5182(16), Fe–P(1) 2.232(4), Pt–

P(2) 2.328(3), Pt–P(3) 2.293(3), Fe–C(1) 1.905(13), Fe–C(10) 1.775(12), Fe–C(11) 1.775(14), Fe–C(12)

1

3

1.822(14), Pt–C(1) 1.989(15), C(1)–N(1) 1.330(17), C(2)–N(1) 1.488(18), N(1)–C(3) 1.452(17), C(10)–O(1)

ACCEPTED MANUSCRIPT

1

.170(14), C(11)–O(2) 1.164(15), C(12)–O(3) 1.136(14), P(1)–N(2) 1.708(9), P(2)–N(2) 1.710(10); P(1)–

Fe–Pt 95.95(10), P(2)–Pt–Fe 96.19(8), P(3)–Pt–Fe 156.89(10), P(3)–Pt–P(2) 106.91(11), Pt–C(1)–Fe

0.6(6), C(10)–Fe–Pt 76.1(4), C(11)–Fe–Pt 161.8(5), C(12)–Fe–Pt 88.9(4), C(1)–Pt–P(3) 108.6(4), C(1)–Pt–

8

P(2) 144.4(4), C(1)–Fe–P(1) 146.3(4), N(1)–C(1)–Fe 137.2(10), C(1)–N(1)–C(2) 124.5(12), C(1)–N(1)–

C(3) 122.0(12), C(2)–N(1)–C(3) 113.4(13), P(1)–N(2)–P(2) 124.2(6).

Fig. 4. Perspective view of the cation of 5d showing the atom-labelling scheme. Hydrogen atoms, the

CH Cl and Et O molecules have been omitted. Only the ipso carbon atoms of the phenyl groups of dppa are

2

shown for clarity. Selected distances (Å) and angles (°): Fe–Pt 2.500(9), Fe–P(1) 2.217(8), Pt–P(2) 2.281(8),

Pt–P(3) 2.282(9), Fe–C(1) 1.909(11), Fe–C(2) 1.759(10), Fe–C(3) 1.869(11), Pt–C(1) 1.992(9), C(1)–N(1)

1

.265(12), C(5)–N(1) 1.474(13), N(1)–C(6) 1.477(13), C(2)–O(1) 1.145(11), C(4)–O(2) 1.125(11), C(3)–

N(3) 1.154(12), P(1)–N(2) 1.678(9), P(2)–N(2) 1.665(10); P(1)–Fe–Pt 96.9(3), P(2)–Pt–Fe 95.3(3), P(3)–Pt–

Fe 157.12(13), P(3)–Pt–P(2) 107.5(2), Pt–C(1)–Fe 79.8(4), C(2)–Fe–Pt 84.7(4), C(4)–Fe–Pt 158.1(3), C(3)–

Fe–Pt 83.0(4), C(1)–Pt–P(3) 108.6(3), C(1)–Pt–P(2) 143.9(3), C(1)–Fe–P(1) 148.5(3), N(1)–C(1)–Fe

1

35.9(7), N(3)–C(3)–Fe 178.5(8), C(1)–N(1)–C(5) 124.4(8), C(1)–N(1)–C(6) 122.5(8), C(5)–N(1)–C(6)

13.1(8), C(3)–N(3)–C(14) 174.1(11), P(1)–N(2)–P(2) 126.2(5).

1

Similarly, N-alkylation of 3c affords the macrocyclic compound 5c, whose enhanced stability in

1

3

solution compared to that of precursor 3c allowed the recording of a C NMR spectrum.

Characteristic for this type of aminocarbyne complexes is the resonance of the µ-C atom, which is

2

observed in the low-field region at δ = 315.7 as a doublet of doublets of doublets with J(P-C)

coupling constants of 3, 16 and 79 Hz, respectively.

1

4

More complicated is the outcome of the N-alkylation of 2b using ethyl triflate leading to

ACCEPTED MANUSCRIPT

[

(OC) Fe{µ-CN(Et)Bz}(µ-dppa)Pt(PPh )][OSO CF ] (5h) (Scheme 4). Initially, the isomer with an

3 3 2 3

orientation of the benzyl group towards the Fe(CO) fragment and of the ethyl group toward Pt is

3

formed. NMR monitoring reveals after some hours in solution the appearance of a second set of

signals, whose intensity augments steadily. After approximately 24 h the presence of an isomeric

mixture of 50% 5h and 50% 5h' can be observed. It seems that now a steady state equilibrium is

3

1

reached, since no further conversion in favor to isomer 5h' occurs. Recording the P NMR at 318

and 228K respectively revealed no shift of the 50:50 ratio between the two isomers. After

recrystallization, a crystalline mixture was obtained in which 5h' is enriched to about 70 %. This

1

31

finding allows assigning unequivocally the sets of signals in the H NMR and P NMR spectra to

the respective isomer (see Experiment. Section). A restricted rotation around the C-N bond of the

trimetallic cluster [Fe (µ -H)(CO) {µ-CN(Et)i-Pr}] has been evidenced by Howell et al. via NMR

3

2

10

experiments at variable temperature [32]. The isomerization in the case of 5h ⇄ 5h' implies also a

restricted rotation around the C-N bond, therefore a description of the complexes of series 5 as µ₂-

aminocarbyne complexes is more appropriate than considering them as dimetallated iminium salts.

In contrast, ethylation of 3a resulted in formation of only one isomeric form of

[

(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-dppa)Pt(PPh )] (5i), in which the ethyl group is pointing

2 3

+

towards the PtPPh moiety. The composition of this yellow salt was also ascertained by a FAB

3

mass spectrum exhibiting an intense peak of the cation at m/z 1245, whose experimental isotopic

distribution pattern fits with the simulated one.

As discussed above, addition of tert-butylisonitrile to 2a yielded exclusively the carbonyl

substitution product 3d. In contrast, upon addition of an excess of tert-BuNC to 5b no carbonyl

substitution takes place. Instead the Pt-bound PPh ligand is replaced by tert-BuNC in a

3

regioselective manner to give [(OC) Fe{µ-CN(Me)Bz}(µ-dppa)Pt(CNBu-t)][BF ] (5e) (Scheme 5).

3

4

3

1

P NMR monitoring revealed that within 15 min quantitative formation of 5e occurs as evidenced

2

+3

by the observation of two doublets at δ = 125.5 and δ = 45.9 with a J(P-P) coupling of 152 Hz

along with a broad hump at δ -1.7 due to the liberated PPh . In an analogous manner, 5c reacts

3

quantitatively with tert-BuNC to give the mixed isonitrile salt 5g bearing both a Fe-bound and a Pt-

3

1

bound terminal CNR ligand. The composition of this yellow salt, whose P NMR spectrum is

+

depicted in the SI (Figure S3), was furthermore ascertained by FAB mass spectrometry showing as

most intense peak that of cation at m/z 1054. The isotopic distribution of the experimental spectrum

matches perfectly with the simulated one.

The nucleophilic trialkylphosphite ligands are known to substitute carbonyl ligands in dinuclear

organometallics, [33-35] but there are also some examples of P-C coupling reactions [36-40]. For

1

2

example, P(OMe) reacts with the allenyl ligand in [Fe (CO) (µ-PPh ){µ-η :η -(H)C=C=CH }] to

3

2

6

2

1

5

1

2

affords the α,β-unsaturated phosphonate-bridged complex [Fe (CO) (µ-PPh ){µ- η :η -

2

6

2

ACCEPTED MANUSCRIPT

(

CH )C=CH{P=O(OMe) }}]. However, when reacting 5a with P(OMe) , exclusively PPh

3 2 3 3

substitution occurred yielding exclusively [(OC) Fe{µ-CN(Me)xylyl}(µ-dppa)Pt{P(OMe) }][BF ]

3

4

3

1

(

5f). The P NMR spectrum (shown in Figure S4) exhibits a doublet of doublets at δ 141.9 with a

1

195

very strong J(Pt-P) coupling of 6088 Hz, characteristic for a Pt-bound P(OMe) ligand. The Pt

3

NMR spectrum features the expected ddd pattern at δ -2631 with J(Pt-P) couplings of 6088, 2636

and 69 Hz.

H

N

H

N

^P^P^h2

^P^P^h3

PPh₂

Ph P

2

L

O

L

Pt

C

CH Cl₂

2

Fe

CO

C

- PPh₃

C

BF₄

Me

C

BF₄

Me

N

R

5

a

b

R = Xylyl

R = Benzyl

5e R = Benzyl, L = t-BuNC

5f R = Xylyl, L = P(OMe)₃

H

N

PPh₂

C N

Pt

Ph P

2

N

t-BuNC

N

PPh₃

Pt

t-Bu

C

CH Cl₂

2

O

Fe

O

Fe

O

CO

C

O

- PPh₃

C

BF₄

Me

C

BF₄

N

Me

5g

5

c

Scheme 5. Site-selective substitution of the Pt-bound PPh ligand by L

3

2

.4. Preparation and reactivity of zwitterionic aminocarbyne complexes

.4.1 Preparation of zwitterionic aminocarbyne complexes

2

Due its slightly acidic character, the N-H group of dppa can be easily deprotonated by bases to

give bis(diphenylphosphanyl)amide. For example, treatment of dppa with BuLi affords the salt

Li[Ph PNPPh ] [41]. The possibility to deprotonate metal-coordinated dppa has been demonstrated

2

for early and late transition metal complexes, selected examples are the mononuclear chelate

complexes [Pd(Cl)(Ph PNPPh )(PEt )] and [CpFe(CO)(Ph PNPPh )] [42-45]. Ellermann and

2

3

2

Braunstein have reported on the deprotonation of homo- and heterodinuclear dppa-spanned

complexes [46]. We have communicated several years ago that deprotonation of the dppa-bridge

of 5a occurs even with mild bases such as KOSiMe leading to the structurally characterized

3

zwitterionic aminocarbyne complex [(OC) Fe{µ-CN(Me)xylyl}(µ-Ph PNPPh )Pt(PPh )] (6a)

3

2

3

[

11]. To explore the scope of the reactivity of these species, we prepared a couple of other

1

6

derivatives including examples bearing a terminal CNR ligand. Thus addition of KOSiMe to a

3

ACCEPTED MANUSCRIPT

CH Cl solution of 5b produces quantitatively the very stable compound [(OC) Fe{µ-

2

3

1

95

31

CN(Me)Bz}(µ-Ph PNPPh )Pt(PPh )] (6b). Like in 6a, the resonances in the Pt and P NMR

2

3

spectra of 6b are considerably broadened, whereas the resonance of the Pt-bound PPh ligand

3

gives rise to a well-resolved doublet (See Experimental Section). Addition of an excess of t-BuNC

31

to a solution of 6a did not lead to a carbonyl substitution, P NMR monitoring revealed a

quantitative replacement of the Pt-bound PPh₃producing [(OC) Fe{µ-CN(Me)xylyl}(µ-

3

Ph PNPPh )Pt(CNBu-t)] (6c) (Scheme 7). Similarly, the PPh ligand is replaced by addition of a

2

3

slight

excess

of

trimethylphosphite

to

yield

[(OC) Fe{µ-CN(Me)xylyl}(µ-

3

Ph PNPPh )Pt{P(OMe) }] (6d). This yellow microcrystalline zwitterionic complex was

2

3

alternatively obtained in high yield by deprotonation of [(OC) Fe{µ-CN(Me)xylyl}(µ-

3

dppa)Pt{P(OMe) }][BF ] (5f) with KOSiMe .

3

4

3

H

N

^P^P^h2

^P^P^h3

PPh₂

Ph₂P

O

L

C

Pt

C

KOSiMe₃

Fe

CO

-

^H^O^Sⁱ^M^e3

O

C

BF₄

- KBF₄

N

Me

Bz

R

5

b

f

R = Benzyl, L = PPh₃

R = Xylyl, L = P(OMe)₃

HOSiMe₃

6b

-

KOSiMe₃

-

KBF₄

N

PPh₂

CNBu-t

PPh₂

Ph P

2

^P⁽^O^M^e⁾3

2

t-BuNC

^P⁽^O^M^e⁾3

^P^P^h3

O

Pt

O

Pt

C

Pt

C

CH Cl

2

CH Cl₂

2

Fe

CO

C

O

C

O

C

O

- PPh

3

-

PPh₃

C

6

c

6

d

6a

N

Me

Xyl

Me

Xyl

H

N

PPh₂

PPh₃

PPh₂

Xyl

Ph P

2

Ph P

2

N

PPh

3

Pt

C

KH

-H₂

Fe

CO

Xyl

CO

Xyl

C

O

OC

OSO CF

C

2

3

6e

5

i

-

KOSO CF₃

2

N

Et

Scheme 6. Preparation of zwitterionic aminocarbyne complexes 6.

1

7

ACCEPTED MANUSCRIPT

The basicity of KOSiMe is not sufficient to deprotonate the more electron-rich isonitrile-

3

+

substituted complexes [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-dppa)Pt(PPh )] (5i), however the

2

3

addition of KH to a THF solution allows a fast and quantitative conversion to zwitterionic

complex [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-Ph PNPPh )Pt(PPh )] (6e) (Scheme 6).

2

3

2.4.2 Preparation of N-alkylated aminocarbyne complexes

In the presence of an excess of CH I, the amide function of the deprotonated dppa ligand of

3

6b

is readily methylated forming the yellow salt [(OC) Fe{µ-CN(Me)Bz}{µ-

3

Ph PN(Me)PPh }Pt(PPh )][I], which coexists according the NMR data as a 80:20 mixture of

2

3

isomers 7a and 7a’ (Scheme 7 and Figure S5). We assume that this coexistence of two isomeric

forms is again due to a restricted rotation around the C-N bond, as already discussed in the case of

the 5h ⇄ 5h' interconversion.

Me

N

Me

N

^P^P^h2

^P^P^h3

PPh₂

PPh₃

Ph P

^P^h2^P

2

Ph₂P

O

Pt

O

^P^P^h3

C

^C^H3^I

C

Pt

O

Pt

C

Fe

+

Fe

CO

C

CH Cl

C

CO

O

2

O

C

O

I

C

298 K

C

6

b

7a

N

7a'

N

Me

Bz

Me

N

PPh₂

N

PPh₂

PPh₃

Ph P

2

N

Ph P

2

^P^P^h3

N

CH₃I

CH Cl

Pt

C

Pt

C

Fe

CO

Fe

C

O

CO

2

C

O

2

98 K

C

7b

C

6e

I

N

Et

Scheme 7. N-methylation of the zwitterionic aminocarbyne complexes 6.

Quantitative N-methylation of the P-N-P backbone also occurs after agitation of a solution of

the zwitterionic complex 6e in the presence of an excess of CH I to produce [(OC) (xylylNC)Fe{µ-

3

2

CN(Et)xylyl}{µ-Ph PN(Me)PPh }Pt(PPh )][I]

(7b).

The

formation

of

a

2

3

1

bis(diphenylphosphino)methylamine-bridge was evidenced from the H NMR spectrum, which

3

displays a triplet ( J(P-H) = 6.1 Hz) at δ 2.45 due to the N-Me group. Compared to the dppa-

bridged derivative [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-dppa)Pt(PPh )][OSO CF ] 5i, the N-

2

3

2

3

1

8

methylation causes a significant low-field shift of the diphosphine resonances to δ 124.0 and 99.2

ACCEPTED MANUSCRIPT

ppm, whereas the signal of the PPh ligand at δ 33.0 has the same chemical shift as in 5i.

3

2.4.3 Preparation of heterotrimetallic aminocarbyne complexes

Ellermann has reported that reaction of Li[Ph PNPPh ] with PPh AuCl does not lead to the gold

2

3

amide complex [Ph PN(AuPPh )PPh ], but to formation of the dinuclear species [Au(Ph P) N]

2

3

2

with dissociation of triphenylphosphine [47a]. In contrast, the lithiated chelate complexes

Li[(OC) M(Ph PNPPh )] (M = Cr, Mo, W) have been converted to the heterodinuclear compounds

4

2

[

(OC) M{Ph PN(AuPPh )PPh }] [47b]. This intrigued us whether the zwitterionic compounds of

4 2 3 2

type 6 could be used to construct heterotrimetallic complexes by reaction with electrophilic coinage

metal salts. Initial attempts to react 6a with PPh AuCl were not straightforward, but using in situ

3

generated [AuPPh ][OSO CF ] allowed the isolation of the heterotrinuclear gold-amide complex

3

2

3

[

(OC) Fe{µ-CN(Me)xylyl}{µ-Ph PN(AuPPh )PPh }Pt(PPh )][OSO CF ] (8a) in 58% yield in

3

2

3

2

3

2

3

form of air-stable bright-yellow crystals (Scheme 8).

^A^s^P^h3

PPh₃

Au

N

Cu

N

^P^P^h2

^P^P^h3

PPh₂

N

PPh₂

PPh₃

Ph P

2

L

2

Ph P

2

C

^P^P^h3

O

L

Pt

[

AuPPh ]CF SO

Pt

3

Fe

CO

C

CH Cl

C

CO

O

2

O

C

O

CF SO

NO₃

Me

3

C

298 K

C

N

R

Xyl

6

a

e

L = CO ; R = Me

L = XylyNC ; R = Et

8a L = CO ; R = Me

8b L = XylyNC ; R = Et

8

c

Ph₃P PPh₃

Cu

PPh₃

Cu

Me

Hg

N

PPh₂

N

PPh₂

Ph P

^P^h2^P

L

2

- PPh₃

PPh₃

Ph

C

2

P

PPh₃

^P^P^h3

O

L

Pt

PPh

3

Pt

+

Fe

CO

C

O

C

O

C

O

C

O

^N^O3

NO₃

Et

Cl

C

N

Et

Me

Xyl

8

d

L = XylyNC

8d' L = XylyNC

8e

Scheme 8. Preparation of heterotrimetallic aminocarbyne complexes 8.

31

The structure of the trimetallic core of 8a can be deduced from the combination of P- and

1

95

Pt-NMR spectra. As encountered in the bimetallic µ-aminocarbyne complexes presented above,

1

9

3

1

the P{ H}-NMR spectrum consists of three mutually coupled signals at δ 105.6, 87.0 and 34.8,

ACCEPTED MANUSCRIPT

which are assigned to the iron- and platinum-bound dppa nuclei as well as to the Pt-bound PPh₃

ligand. The resulting doublet of doublets pattern is splitted again by coupling with the PPh ligand

3

coordinated on the gold atom (δ = 32.3), so finally the signals appear in form of a doublet of

1

95

doublets of doublets. Furthermore, each ddd resonance is flanked by Pt satellites. These Pt-P

195

1

couplings are detailed in the Pt{ H} NMR spectrum depicted in Figure 5. Note that due to an

2

+3

4

accidentally identical magnitude of the

J(Pt-P) and J(Pt-P) coupling of around 66 Hz, the

pattern of the signal centered at δ - 2618 appears as a doublet of doublets of triplets.

1

95

1

Fig. 5. Pt{ H} NMR spectrum of heterotrimetallic complex 8a in CDCl at 298 K

3

Crystal structure of [(OC) Fe{

µ-CN(Me)xylyl}{

µ-Ph PN(AuPPh )PPh }Pt(PPh )][OSO CF ] (8a).

2 3 2 3 2 3

3

Suitable single-crystals of 8a were grown from CH Cl /Et O. The structure of this salt crystallizing

2

in the monoclinic space group P2 /n is shown in Figure 6. The Fe–Pt bond distance of 2.4932(6) Å

1

is very similar with that of 5d. Like in precursor 6a, the xylyl group of the aminocarbyne ligand

points towards the sterically less crowded Fe(CO) fragment. The N–P–Au array of the gold-amid

3

fragment is almost linear [N(1)–Au–P(1) = 174.26(10)°]. The bond length of the covalent Au–N(1)

amide bond amounts to 2.053(4) Å and may be compared with that of the trinuclear complex

[

C H {NHPPh Au(C F ) }{N(AuPPh )PPh Au(C F ) }] 2.096(4) [48]. Also the Au–P(1) distances

6 4 2 6 5 3 3 2 6 5 3

are quite comparable in both compounds [2.2213(13) vs. 2.2404(16) Å].

2

0

ACCEPTED MANUSCRIPT

Fig. 6. Perspective view of 8a showing the atom-labelling scheme. Hydrogen atoms have been omitted for

clarity. Selected distances (Å) and angles (°): Fe–Pt 2.4932(6), Fe–P(3) 2.2576(13), Pt–P(2) 2.2930(12), Pt–

P(4) 2.2730(11), Fe–C(43) 1.781(5), Fe–C(44) 1.787(5), Fe–C(45) 1.793(5), Fe–C(64) 1.929(4), Pt–C(64)

1

.987(4), C(64)–N(2) 1.276(5), C(67)–N(2) 1.456(5), N(2)–C(66) 1.475(5), C(43)–O(1) 1.144(5), C(44)–

O(2) 1.143(5), C(45)–O(3) 1.139(5), P(2)–N(1) 1.681(4), P(3)–N(1) 1.664(3), Au–N(1) 2.053(4), Au–P(1)

.2212(13); P(3)–Fe–Pt 96.03(4), P(2)–Pt–Fe 94.56(3), P(4)–Pt–Fe 157.25(3), P(4)–Pt–P(2) 108.05(4), Pt–

2

C(64)–Fe 79.09(16), C(43)–Fe–Pt 156.70(15), C(44)–Fe–Pt 87.49(14), C(45)–Fe–Pt 74.48(14), C(64)–Pt–

P(4) 107.97(13), C(64)–Pt–P(2) 143.97(12), C(64)–Fe–P(3) 146.55(13), N(2)–C(64)–Fe 136.8(3), C(64)–

N(2)–C(67) 121.8(4), C(64)–N(2)–C(66) 124.0(4), P(3)–N(1)–P(2) 122.1(2), Au–N(1)–P(2) 116.61(18),

Au–N(1)–P(3) 121.23(19), N(1)–Au–P(1) 174.26(10).

In a similar manner, the yellow heterotrimetallic salt [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}{µ-

2

Ph PN(AuPPh )PPh }Pt(PPh )][OSO CF ] (8b) was obtained by reaction of 6e with

2

3

2

3

2

3

[

AuPPh ][OSO CF ] (Scheme 8). This yellow compound was characterized by IR spectroscopy and

3 2 3

1

95

multinuclear NMR techniques (Table 3). Noteworthy is the Pt NMR spectra shown in Figure S6

in the SI. In contrast to the spectrum of 8a, now 4 distinct Pt-P couplings are present. Therefore the

resonance centered at δ -2672 is splitted into a doublet of doublets of doublets of doublets pattern,

2

+3

1

4

1

2

1

3

with J(P -Pt) = 60, J(P -Pt) = 81, J(P -Pt) = 2774 and J(P -Pt) = 3577 Hz. All solution data

match perfectly with those of an X-ray diffraction study.

2

1

ACCEPTED MANUSCRIPT

Crystal

structure

of

[(OC) (xylylNC)Fe{µ-CN(Et)xylyl}{µ-

2

Ph PN(AuPPh )PPh }Pt(PPh )][OSO CF ] 8b

2

3

2

3

2

3

Suitable crystals of 8b•CH Cl were obtained from CH Cl /Et O. The structure of this compound is

2

presented in Fig. S7 in the Supporting Information, together with selected bond length and angles.

Since the overall structures of 8b is very reminiscent to that of 8a, only the most relevant features

are discussed. The Fe–Pt bond distance of 8b is almost identical to that of 8a (2.4943(13) vs.

2.4932(6) Å). The linear terminal iron-bound isonitrile ligand is orthogonal with respect to the

metal–metal bond, the angle Fe–Pt–C(14) being 93.5(3)°. Within the gold-amide fragment, the N–

P–Au array is almost linear [N(2)–Au–P(4) = 176.2(2)°]. The bond length of the covalent Au–N(2)

bond amounts to 2.060(6) Å, the Au–P(4) distance 2.215(2) Å. The P(1)–N(2) and P(2)–N(2)

distances of 1.655(7) und 1.672(6) Å also match with those of 8a.

Spectroscopic properties of 8a.

Many articles concerning the photophysical behaviour of platinum complexes bearing

phosphine ligands are reported in the literature [49]. There are also several reports on the

luminescence properties of gold complexes [50]; for example the Au(I)PR fragment is known to

3

exhibit luminescence both in the solid state and in solution [51]. It was therefore of interest to

investigate the trinuclear complex 8a containing these two heavy metals. The normalized electronic

absorption and emission spectra recorded in CH Cl and in the solid state are shown in Figure 7.

2

Absorption and emission spectral data obtained in solution and in the solid state are summarized in

Table 2. The absorption spectrum of 8a is dominated by the phosphine and MeXylyl π,π*

transitions at 247 and 278 nm. After excitation at 370 nm, 8a exhibits the emission maximum at

434 nm. This emission band was also observed for the dinuclear complex 5a (Table 2, Fig. S8),

thus confirming that there is no significant contribution of the AuPPh fragments. The emission

3

intensity of 8a in 2-MeTHF (Fig. S9) increases when the temperature decreases and leads to the

conclusion that it is phosphorescence centered on the phosphine ligand as assigned for

[

Au(PPh ) ][PF ] [50a] or [Cu(PPh ) ][BH ] [52]. After excitation at 380 nm, the emission spectra

3 2 6 3 2 4

recorded in the solid state for complexes 5a (Fig. S8) and 8a (Fig. 7) are similar and show two

bands, a high energy (HE) band around 438 nm and a low energy (LE) band about 668 nm. The HE

band in the spectra of 5a and 8a observed in solution is assigned to the emission centered on the

phosphine ligands. The LE band is due either to emission from a platinum-based state or to an

excimer present in the solid state. The large Stokes shift of this emission is typical of metal-based

states in similar compounds [53].

2

1

.2

1

.2

1

ACCEPTED MANUSCRIPT

Ex.

Abs.

1

Em.

0

.8

0

.8

.6

.4

.2

0

0.6

0.4

0.2

0

2

30

330

430

530

630

360

420

480

540

600

660

720

λ(nm)

Fig. 7. Normalized absorption (blue) and emission (red) spectra of 8a recorded in CH Cl at 298K (left) and

2

in the solid state at 298K (right).

Table 2. Absorption and emission spectral data obtained for 5a and 8a.

Absorption

Emission

Complex

CH Cl at 298 K

solid at 298 K

em/nm [λexcit/nm]

439, 670 [380]

2-MeTHF

2

-1

λ /nm (ε/L mol cm )

abs

λ_e_m/nm[λ_e_x_c_i_t/nm]

λ

em /nm [λexcit/nm]

5

8

a

232 (24150), 277 (sh) (5000)

247 (22760), 278 (23450)

433[370]

-

434[370]

436, 667 [380]

415[370]

The related trimetallic aminocarbyne complex [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}{µ-

2

Ph PN(CuPPh )PPh }Pt(PPh )][NO ] (8d) bearing a Cu-N bond was obtained by treatment of 6e

2

3

2

3

with [Cu(PPh ) ][NO ] [54a]. Unfortunately, due to its lability in solution no satisfying elemental

3

2

3

analysis could be obtained. Thus our tentative structural proposition for 8d is essentially based on

31

1

2+3

the P{ H} NMR spectrum recorded at 233 K. This shows two signals at δ 105.1 (dd, J(P-P) =

3

+4

2

129 Hz,

J(P-P) = 12 Hz), 83.6 (dd, J(P-P) = 12 Hz) for the phosphorous nuclei of the

diphosphine and a triplet at 34.6 for the Pt-bound PPh ligand. Two further very broadened signals

3

at δ 9.9 and -0.4 are attributed to the two Cu-bound PPh ligands. This broadening could be on the

3

6

3

65

one hand due to the quadrupole moment of the Cu-isotopes Cu (69% natural abundance) and Cu

31% natural abundance) with I = 3/2. However, upon raising the temperature a progressive

(

broadening, notably that of the high-field signal was noticed, which gets shifted towards the

resonance for uncoordinated PPh (δ = -4.5). At ambient temperature, the three low-field signals of

3

the Fe-Pt core remain well resolved; in contrast the resonances at δ 10.0 and -2.0 are collapsed to

broad "humps". We therefore suggest a partial dissociation of one of the Cu-bound PPh occurs,

3

which is slowed down at low temperature. The interpretation of the NMR data is hampered by the

lability of the Cu-N amide bond. During several attempts to grow single-crystals, the aminocarbyne

complex [(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-dppa)Pt(PPh )][NO ]•O=PPh (5i’) has been

2

3

isolated, in which a O=PPh ligand is attached through a hydrogen bridge on the dppa ligand [55,

3

56]. The coordination of triphenylphosphine oxide via a N-H····O-bridge is obvious from the IR-

2

3

1

-1

and P NMR spectra. A broad N-H absorption at 3130 cm , as well as overtone/combination

ACCEPTED MANUSCRIPT

-1

vibration at 2667 cm are characteristic for the presence of a hydrogen bridge.

We reacted also 6a with [Cu(AsPh ) ][NO ] [54b] and succeeded to isolate [(OC) Fe{µ-

3

CN(Me)xylyl}{µ-Ph PN(CuAsPh )PPh }Pt(PPh )][OSO CF ] (8c) in 51% yield (Scheme 8).

2

3

2

3

2

3

1

195

Whereas the resonances in the P NMR spectrum are well-resolved, the Pt NMR spectrum

exhibits a very broadened doublet of doublet centered at δ -2584. According the elemental analysis

obtained for this microcrystalline bright-yellow product, only one AsPh ligand is ligated on the

3

copper atom. 8c is moderately stable in the solid state, but NMR monitoring reveals that in solution

like in the case of 8d progressively rupture of the Cu-N amide bond occurs giving [(OC) Fe{µ-

3

CN(Me)xylyl}(µ-dppa)Pt(PPh )][NO ] (5a’). The cleavage product 5a’ was also the sole product

3

which could be isolated when attempting to react 6a with [Ag(AsPh ) ][NO ] [57].

3

We also failed to obtain any metallation product when reacting 6a with Me SnCl and Me PbCl,

3

only quantitative formation of [(OC) Fe{µ-CN(Me)xylyl}(µ-dppa)Pt(PPh )][Cl] was noticed [58].

3

However, treatment of 6a and 6e with MeHgCl afforded the mercurated heterotrinuclear amide

complexes [(OC) (L)Fe{µ-CN(R)xylyl}{µ-Ph PN(HgMe)PPh }Pt(PPh )][Cl] 8e (L = CO; R = Me)

2

3

and 8f (L = xylylNC; R = Et). Characteristic for these yellowish solids is the observation of a

1

2

199

singlet resonance in the H NMR spectra, whose J( Hg-H) couplings of 202.0 and 204.5 Hz are

in the range reported for other methylmercury(II) amides [59].

3. Conclusion and Perspectives

We have demonstrated that the bonding mode (bridging vs. terminal) of the CNR ligand in

these dppa-spanned Fe-Pt complexes is governed by the electronic propensity of the isonitrile. A

t

strongly donating CNR ligand such as CNBu occupies a terminal site on Fe, whereas isonitriles

with a more pronounced π-acceptor character prefer a bridging position. Also the coordination of a

second CNR ligand is electronically controlled (site-selectivity). Whereas in the case of

[

(OC) Fe(µ-CN-R)(µ-dppa)Pt(PPh )] (2)

a

Fe-bound carbonyl is substituted to give

3

(OC) (RNC)Fe(µ-CN-R)(µ-dppa)Pt(PPh )] (3), the addition of CNR to the aminocarbyne

2

3

+

complexes [(OC) Fe{µ-CN(R)R’}(µ-dppa)Pt(PPh )] leads exclusively to substitution of the Pt-

3

+

bound PPh ligand. The cationic aminocarbyne salts [(OC) (L)Fe{µ-CN(R)R’}(µ-dppa)Pt(PPh )]

3

2

3

(

5 R’ = Me, Et), which are conveniently prepared by N-alkylation using [Me O][BF ] or ethyl

3 4

triflate, are readily deprotonated by bases to yield the zwitterionic aminocarbynes [(OC) (L)Fe{µ-

2

CN(R)R’}(µ-Ph PNPPh )Pt(PPh )] (6). These latter in turn can be converted to heterotrimetallic

2

3

+

species by N-metallation using [AuPPh ] , [CuPPh ] , [CuAsPh ] and ClHgMe as electrophiles.

3

We are currently investigating the reactivity of these µ-aminocarbyne complexes towards

unsaturated molecules such as alkenes and alkynes for C-C coupling reactions [60].

2

4

2

5

ACCEPTED MANUSCRIPT

3

1

195

1

Table 3. Selected P{ H}- and Pt{ H} NMR data (δ in ppm and J in Hz) at 298K, in CDCl

3

1

2

3

2+3

1

2

3

1

3

195

Complex

δ(P )

J(P -P ); J(P -P ); J(P -P );

δ( Pt)

1

2

1

.

2+3

1

J(Pt-P ); J(Pt-P ); J(Pt-P )

2

c

113.8 dd

112.8 dd

112.1 dd

114.4 dd

118.0 d

88.7 dd

88.2 dd

87.8 dd

89.0 dd

92.8 dd

93.3 dd

88.5 dd

88.8 dd

89.8 dd

80.3 dd

80.6 dd

81.3 dd

82.2 dd

45.9 d

38.8 dd 175; 45; 9; 2897; 4275; 42

37.8 dd 170; 40; 10; 2862; 4267; 41

37.2 dd 164; 40; 10; 2830; 4248; 47

37.7 dd 180; 45; 8; 2891; 4297; 48

-2690 ddd

-2969 ddd

-2680 ddd

–

2

d

2

e

2

f

2f’

42.1 d

41.7 d

213; 62; ND; ND; ND; ND

–

2

3

g

117.9 d

212; 62; ND; 2868; 4628; ND

-2544 ddd

–

b

113.3 dd

113.9 dd

112.8 dd

114.4 dd

102.7 dd

104.6 dd

103.1 dd

125.5 d

38.3 dd 184; 58; 10; 2956; 4172; ND

39.1 dd 185; 54; 10; 2950; 4188; ND

41.3 dd 195; 59; 8; 2973; 4132; ND

30.0 dd 158; 32; 10; 3375; 4050; 45

34.6 dd 100; 9; 13; 2808; 3793; 72

33.7 dd 110; 18; 14; 2963; 3656; 76

34.3 dd 114; 19; 13; 2981; 3603; 69

152; 3920; ND

3

c

–

3

d

b

–

4

-3102 ddd

-2715 ddd

-2809 ddd

-2836 ddd

–

5

c

5

d

5

e

5

f

102.7 dd

108.1 d

79.8 dd

77.1 d

141.9, dd 106; 10; 19 2636; 6088; 69

119; 2876; 82

-2631 ddd

-2587 dd br

–

5

g

h

102.1 dd

101.7 dd

103.8 dd

86.6 dd br

103.7 d br

87.9 dd

80.2 dd

79.8 dd

81.5 dd

72.0 d

34.6 dd 100; 7; 13; 2819; 3802; 71

33.5 dd 100; 7; 13; 2811; 3781; 71

5

h’

–

5

i

33.2 tr

35.9 d

109; 17; 2924; 3590; 72

129; 14; ND; 2521; 3748

112; ND, 2730

-2791 ddd

-2470 dd br

–

6

b

6

c

77.0 d br

70.4 dd

70.7 d br

97.8 dd

97.5 dd

99.2 dd

87.0 ddd

87.7 ddd

83.7 dd

83.6 dd

80.7 dd

84.9 d br

6

d

145.9 dd 131; 11; 18; 2374; 6019; 61

34.9 dd 136; 15; 9; ND; 3452; ND

-2440 dd

–

6

e

85.4 br

7

a

121.8 dd

124.0 dd

105.6 ddd

106.4 ddd

101.9 dd

105.1 dd

102.5 dd

34.2 t

32.9 t

121; 12; 12; 2876; 3858; ND

121; 11; 12; 2876; 3821; ND

-2758 ddd

-2789 ddd

-2834 ddd

-2618 ddt

-2672 dddd

-2584 dd, br

7

a’

7

b

33.0 dd 130; 19; 13; 2985; 3694; 72

34.8 ddd 115; 7; 13; 2689; 3808; 64

b

8

a

c

8

b

33.8 dt

125; 13; 15; 2774; 3577; 60

8

c

35.6 dd 121; 5; 12; 2819; 3819; 69

d

8

d

34.6 t

34.3 t

33.7 t

129; 12; 12; 2754; 3568; ND

102; 11; 9; 2834; 3813; 70

e

8

e

–

8f

109.0 d br

102; 14; ND; 3584; ND; ND

1

2

3

a

b

4

P = P ; P = P ; P = PR . ND = Not determined. δ at 243 K. δ (PPh ) = 32.3, “q”, J(P-P) = 5 Hz, J(Pt-

Fe

Pt

3

3Au

c

4

d

PPh ) = 68 Hz. δ (PPh ) = 32.5, “q”, J(P-P) = 5 Hz, J(Pt- PPh ) = 81 Hz. δ (PPh₃_C_u) = 9.9, s; -0.4, s,

3Au

e

br. δ at 253 K.

2

5

2

6

ACCEPTED MANUSCRIPT

4. Experimental

All reactions were performed in Schlenk-tube flasks under purified nitrogen. Solvents were dried

and distilled under nitrogen before use, toluene and hexane over sodium, dichloromethane from

P O . – IR spectra have been recorded on a Nicolet Nexus 470 spectrometer. - Elemental C, H, N

4

10

1

31

1

analyses were performed on a Leco Elemental Analyser CHN 900. - The H and P{ H} NMR

spectra were recorded at 313.13 and 121.50 MHz, respectively, on a Bruker Avance 300

1

95

1

instrument, or on a Bruker ACP 200 machine (200.13 and 81.01 MHz). The Pt{ H} chemical

shifts were measured on a Bruker ACP 200 instrument (42.95 MHz) and externally referenced to

K PtCl in water with downfield chemical shifts reported as positive. NMR spectra were recorded

2

4

in CDCl , unless otherwise stated. The reactions were generally monitored by IR spectroscopy in

3

the ν(CO) region. The isocyanides and alkylating agents were obtained commercially from Alfa

Aesar or Aldrich. Dppa and 1,2-bis(2-isocyanophenoxy)ethane wer prepared as described in the

literature [61].

4

.1. Preparation of [(OC) Fe(

µ-CN-R)(µ-dppa)Pt(PPh )] (2)

3

To a solution of [(CO) Fe(µ-CO)(µ-dppa)Pt(PPh )] (202 mg, 0.2 mmol) in CH Cl (5 ml) was

3

2

added dropwise one equivalent of the respective isonitrile, dissolved in CH Cl (5 ml). After

2

stirring for 20 min. at ambient temperature (CO release), the clear orange-red solution is reduced

and the products were precipitated by slow addition of hexane. The yellow to orange-colored

products are obtained analytically pure with yields ranging from 75 to 95%.

2c

[(OC) Fe(µ-CN-Bz)(µ-dppa)Pt(PPh )]: Anal. Calcd. for C H FeN O P Pt•0.5CH Cl

3 3 53 43 2 3 3 2 2

(

1099.79+42.46): C, 55.68; H, 3.76; N, 2.45. Found: C, 55.77; H, 3.77; N, 2.26 %. IR (CH Cl ):

2 2

ν(CO) 2002 m, 1934 vs, ν(C=N): 1684 m, br; (KBr) ν(NH) 3276 w, ν(CO) 2001 m, 1933 s, 1920 s,

-1

1

3

ν(C=N) 1678 m, br cm . H NMR: δ = 4.87 (s, 2H, CH ), 5.00 (m, br, NH, J(Pt-H) = 89.2 Hz),

2

6.56–7.63 (m, 40H, Phenyl).

2d

[(CO) Fe{µ-CN-CH C(=O)OMe}(µ-dppa)Pt(PPh )]:

Anal.

Calcd.

for

3

2

3

C H FeN O P Pt•0.5CH Cl (1081.73+42.46): C, 52.89; H, 3.77; N, 2.49. Found: C, 53.01; H,

49

41

2

5

3

2

3

.72; N, 2.26 %. IR (CH Cl ): ν(CO) 2006 m, 1940 vs, 1923 sh, ν(C=O) 1750 w, br, ν(C=N) 1676

2 2

-1

1

3

m, br cm . H-NMR: δ = 3.65 (s, 3H, OCH ), 4.42 (s, 2H, CH ), 4.97 (m, br, NH, J(Pt-H) = 90.0

3

2

Hz), 7.06–7.60 (m, 35H, Phenyl).

[(CO) Fe(µ-CN-CH SO p-Tol)(µ-dppa)Pt(PPh )]:

2e

Anal.

Calcd.

for

3

2

3

C H FeN O P PtS•1.5CH Cl (1177.92+127.39): C, 51.02; H, 3.68; N, 2.14. Found: C, 51.48; H,

54

45

2

5

3

2

3

.86; N, 2.37 %. IR (CH Cl ): ν(CO) 2009 m, 1940s, 1922 sh, ν(C=N) 1648 m, br; (KBr) ν(NH)

2 2

2

6

2

7

ACCEPTED MANUSCRIPT

-1 1

3

4

2

250 w, ν(CO) 1990 m, 1926 s, 1918 s, ν(C=N) 1642 m, br cm . H NMR: δ = 2.17 (s, 3H, CH ),

3

.88 (s, 2H, CH ), 4.92 (m, br, NH, J(Pt-H) = 88.2 Hz), 6.74–7.63 (m, 39H, Aryl).

2

f

[(CO) Fe(µ-CN-Bu-n)(µ-dppa)Pt(PPh )]: Anal. Calcd. for C H FeN O P Pt•CH Cl

3 3 50 45 2 3 3 2 2

(

1065.77+84.93): C, 53.23; H, 4.18; N, 2.43. Found: C, 53.31; H, 4.41; N, 2.59 %. IR (CH Cl ):

2 2

-1 1

ν(CO): 1988 vs, 1931 vs, ν(C=N) 1694 m, br cm . H-NMR (243 K): δ = 0.64-1.57 (m, 9H, Bu),

3

4

.99 (m, br, NH, J(Pt-H) = 94.0 Hz), 6.97–7.40 (m, 35H, Phenyl).

2

g [(CO) Fe(µ-CN-Bu-tert)(µ-dppa)Pt(PPh )]: Anal. Calcd. for C H FeN O P Pt•2CH Cl

3

50 45

2

3

2

(1065.77+169.87): C, 50.55; H, 4.00; N, 2.27. Found: C, 50.36; H, 4.18; N, 2.57 %. IR (KBr):

-1 1

ν(NH) 3303 w, ν(CN) 2123 s, ν(CO): 1950 s, 1909 vs, 1735 m cm . H-NMR (263 K): δ = 1.25 (s,

t

3

9

H, Bu), 4.98 (m, br, NH, J(Pt-H) = 89.0 Hz), 6.90–7.70 (m, 35H, Phenyl).

4

.2. Preparation of [(OC) (RNC)Fe(µ-CN-R)(µ-dppa)Pt(PPh )] (3):

3

2

The preparation was similar to that of series 2 reacting 1 with 2 equivalents of CNR or by reacting

2

3

with a further equivalent of the respective CNR ligand.

a [(OC) (xylylNC)Fe(µ-CN-xylyl)(µ-dppa)Pt(PPh )]: Anal. Calcd. for C H FeN O P Pt

2

3

62 54

3

2 3

(1216.98): C, 61.19; H, 4.47; N, 3.45. Found: C, 61.21; H, 4.55; N, 2.89 %. IR (KBr): ν(CO) 1943

-1 1

s, 1908 s, ν(CN) 2092 m, ν(C=N) 1651 m, br cm . H-NMR: δ 1.82 (s, 6H, Xylyl-Me), 2.09 (s, 6H,

3

Xylyl-Me), 5.27 (m, br, NH, J(Pt-H) = 101 Hz), 6.89-7.65 (m, 41H, Aryl).

3

b [(OC) (BzNC)Fe(µ-CN-Bz)(µ-dppa)Pt(PPh )]: Anal. Calcd. for C H FeN O P Pt•1.5CH Cl

2 3 60 50 3 2 3 2 2

(

1188.98+127.39): C, 56.12; H, 4.03; N, 3.19. Found: C, 56.79; H, 4.25; N, 3.27 %. IR (CH Cl ):

2 2

ν(CO) 1930 s, 1878 s, ν(CN) 2157 m, ν(C=N) 1653 m; (KBr) ν(NH) 3311w, ν(CO) 1931 s, 1878 s,

-1 1

ν(CN) 2157 m, ν(C=N) 1652 m cm . H-NMR: δ = 3.69 (s, 2H, CH -N=C), 4.89 (s, 2H, CH -NC),

2

3

6

3

4

.75 (m, br, NH, J(Pt-H) = 89.2 Hz), 7.01–7.28 (m, 45H, Phenyl).

c: Anal. Calcd. for C H FeN O P Pt (1218.91): C, 59.12; H, 3.97; N, 3.45. Found: C, 59.38; H,

6

0

48

3

4 3

.12; N, 3.56 %. IR (CH Cl ): ν(CO) 1953 vs, 1912 s, ν(CN) 2093 m, ν(C=N) 1654 m; (KBr):

2

-1 1

ν(NH) 3420 w, ν(CO) 1948 vs, 1909 s, ν(CN) 2154 w, 2092 m, ν(C=N) 1653 m cm . H-NMR

3

(

302 K): δ = 3.86-4.55 (m, br, 4H, OCH CH O), 5.86 (m, br, NH, J(Pt-H) = 89.2 Hz), 6.60–7.70

2

(

m, 43H, Aryl).

d [(OC) (tert-BuNC)Fe(µ-CN-xylyl)(µ-dppa)Pt(PPh )]: This very labile product was only

3

2

3

characterized in situ by IR spectroscopy and immediately treated with [Me O][BF ] to give stable

3

4

-1

5

d. IR (CH Cl ): ν(CO) 1946 vs, 1899 s, ν(CN) 2122 m, ν( C=N) 1652 m cm .

2 2

2

7

2

8

ACCEPTED MANUSCRIPT

4

.3. Preparation of [(OC) (o-anisylNC)Fe(µ-SO )(µ-dppa)Pt(PPh )] (4): SO is bubbled for 3 min

2 2 3 2

into a solution of 2b (111 mg, 0.1 mmol) in CH Cl (5 ml). After 10 further min. under SO -

2

atmosphere, the solvent is removed under reduced pressure and the residue recrystallized from

CH Cl /Et O. The product has been isolated in form of orange-colored plate-like crystals. Yield: 87

2

mg; 62%. Anal. Calcd. for C H FeN O P PtS•0.5CH Cl (1151.84+42.47): C, 52.80; H, 3.71; N,

52

43

2

5

3

2

-1 1

2

.35. Found: C, 53.08; H, 3.84; N, 2.22 %. IR (KBr): ν(CN) 2125 m, ν(CO) 1982 s, 1942 s cm . H

3

NMR: δ = 3.49(s, 3H, OCH ), 5.15 (m, br, NH, J(Pt-H) = 92.0 Hz), 6.60–7.71 (m, 39H, Aryl).

3

+

4

.4. Preparation of [(OC) (L)Fe{

µ

-CN(R)R’}(

µ

-dppa)Pt(PPh )] (5) :

2

3

A solution of the isonitrile complex (0.1 mmol) in CH Cl (5 ml) is treated with two equivalents of

2

[

Me O][BF ] or EtOSO CF . After stirring for 3-4 h at ambient temperature, all volatiles are

3 4 2 3

removed under reduced pressure and the yellow residue rinsed with ether and then dried under

vacuo. The yields are almost quantitative. If necessary, recrystallization is done from CH Cl /Et O.

2

5b

[(OC) Fe{µ-CN(Me)Bz}(µ-dppa)Pt(PPh )][BF ]:

Anal.

Calcd.

for

3

4

C H BF FeN O P Pt•0.5CH Cl (1201.63+42.47): C, 52.62; H, 3.80; N, 2.25. Found: C, 52.58;

54

46

4

2

3

2

H, 3.82; N, 2.34 %. IR (CH Cl ): ν(CO) 2038 m, 1978 vs, ν(C=N) 1568 m,br; (KBr): ν(NH) 3216

2

-1 1

w, ν(CO) 2032 m, 1970 vs, 1955 sh, ν(CN) 1572 w cm . H NMR: δ = 2.61 (s, 3H, NCH ), 5.54 (s,

3

2

5

4

H, CH -N=C), 6.16 (m, br, NH, J(Pt-H) = 92.0 Hz), 7.15–7.46 (m, 40H, Phenyl).

2

c: Anal. Calcd. for C H BF FeN O P Pt•Et O•CH Cl (1320.75+74.12+84.93): C, 53.57; H,

61

51

4

3

4

3

2

.29; N, 2.84. Found: C, 53.68; H, 4.03; N, 3.04 %. IR (KBr): ν(NH) 3230 w, br, ν(CN) 2108

-1 1

s, ν(CO) 1982 s, 1942 s, ν(C=N) 1528 w cm . H NMR: δ = 3.01 (s, 3H, NCH ), 4.19-4.74 (m, 4H,

3

13

1

OCH ), 5.70 (m, br, NH, J(Pt-H) = 103.0 Hz), 5.81–7.56 (m, 43H, Aryl). C{ H} NMR: δ 315.7

2

3

(

ddd, µ-C, J(P-C) = 79, J(P-C) = 16, J(P-C) = 3 Hz), 212.9 (dd, 2 FeCO, J(P-C) = 25, J(P-C) =

2

3

8

1

5

Hz), 210.5 (d, 1 FeCO, J(P-C) = 8 Hz), 169.4 (dd, FeCN, J(P-C) = 30, J(P-C) = 7 Hz), 113.9-

53.7 (m, Aryl), 68.2 (s, OCH ), 67.3 (s, OCH ), 52.4 (m, br, NCH ).

2

3

d [(OC) (tert-BuNC)Fe{µ-CN(Me)xylyl}(µ-dppa)Pt(PPh )][BF ]: Anal. Calcd. for C H B

2

3

4

59 57

F FeN O P Pt•Et O•0.5CH Cl (1270.80+74.12+42.47): C, 54.97; H, 4.94; N, 3.03 Found: C,

4

3

2

3

2

54.98; H, 4.60; N, 2.77 %. IR (KBr): ν(NH) 3231 w, br, ν(CN) 2148 s, ν(CO) 1980 vs, 1937 s,

-1

1

t

ν(C=N) 1539 w cm . H NMR: δ = 0.78 (s, 9H, Bu), 2.22 (s, 3H, Xylyl-Me), 2.37 (s, 3H, Xylyl-

3

Me), 2.85 (s, 3H, NCH ), 5.98 (m, br, NH, J(Pt-H) = 104.0 Hz), 7.20–7.86 (m, 38H, Aryl).

3

5

e [(OC) Fe{µ-CN(Me)Bz}(µ-dppa)Pt(CNBu-t)][BF ]: Anal. Calcd. for C H BF FeN O P Pt

3 4 50 40 4 3 3 2

(

1130.57): C, 53.12; H, 3.57; N, 3.72. Found: C, 52.96; H, 3.81; N, 3.42 %. IR (CH Cl ): ν(CN)

2 2

2

8

2

9

ACCEPTED MANUSCRIPT

2

1

5

138 s, ν(CO) 2001 s, 1993 s, 1921 vs, ν(C=N) 1568 m,br; (KBr): ν(NH) 3216 w, ν(CO) 2032 m,

-1

970 vs, 1955 sh, ν(CN) 1577 w cm .

f [(OC) Fe{µ-CN(Me)xylyl}(µ-dppa)Pt{P(OMe) }][BF ]: To a solution of 5a (0.1 mmol) in

3

4

3

1

CH Cl (5 ml) is added P(OMe) (38 mg, 0.3 mmol) at room temperature. P NMR-monitoring of

2

3

the reaction mixture reveals a quantitative conversion. After 1 h, the yellow solution is reduced to 2

ml and layered with Ether. In the course of several days, yellow crystals are formed at 5°C. Yield:

(

75 mg, 65%). Anal. Calcd. for C H BF FeN O P Pt•Et O (1077.44 + 74.12): C, 45.89; H, 4.55;

40 42 4 2 6 3 2

N, 2.43%. Found: C, 45.77; H, 4.35; N, 2.20. IR (KBr): ν(NH) 2830 m, br, 2610 m, br, ν(CO)

-1 1

2

030m, 1962 vs, ν(CN) 1557 m cm . H-NMR: δ 2.37 (s, 6H, Xylyl-Me), 3.44 (d, 9H, P(OMe) ,

3

J(P-H) = 13.0 Hz), 3.89 (s, NMe), 7.29-8.30 (m, 23H, Aryl), 10.50 (m, br, NH, J(Pt-H) = 85 Hz).

5

g : Anal. Calcd. for C H BF FeN O P Pt (1141.59): C, 50.50; H, 3.97; N, 4.91. Found: C, 50.64;

48 45 4 4 4 2

+

H, 3.83; N, 4.77 %. MS (FAB /NBA-matrix): 1054 M (25%). IR (CH Cl ): ν(CN) 2213 m, 2145

2

-1

vs, ν(CO) 1990 vs, 1950 s, ν(C=N) 1538 w cm .

and 5h’ [(OC) Fe{µ-CN(Et)Bz}(µ-dppa)Pt(PPh )][OSO CF ]: Anal. Calcd. for

5h

3

2

3

C H F FeN O P PtS (1277.92): C, 52.63; H, 3.78; N, 2.19. Found: C, 52.67; H, 3.78; N, 2.27 %.

57

48

3

2

6 3

-1

1

IR (CH Cl ): ν(CO) 2036 m, 1976 vs, ν(C=N) 1555 w cm . 5h H-NMR: δ = 0.37 (t, 3H, CH -

2

3

CH , J(H-H) = 7.1 Hz), 3.13 (q, br, 2H, CH -CH , J(H-H) = 7.1 Hz), 5.55 (s, 2H, NCH ), NH

3

2

3

2

1

3

signal ND, 7.15–7.46 (m, 40H, Phenyl). 5h’ H-NMR: δ = 1.39 (t, 3H, CH -CH , J(H-H) = 7.1

2

3

Hz), 4.09 (q, br, 2H, CH -CH , J(H-H) = 7.1 Hz), 4.43 (s, 2H, NCH ), NH signal ND, 7.15–7.46

2

3

2

(m, 40H, Phenyl).

5i

[(OC) (xylylNC)Fe{µ-CN(Et)xylyl}(µ-dppa)Pt(PPh )][OSO CF ]:

Anal.

Calcd.

for

2

3

2

3

C H F FeN O P PtS (1395.17): C, 55.96; H, 4.26; N, 3.01. Found: C, 55.42; H, 4.10; N, 2.87 %.

65

59

3

5 3

+

(

FAB /NBA-matrix): 1245 M (90%), 1189 M - 2 CO (36%). IR (KBr): ν(NH) 3240 w, br, ν(CN)

-1

1

3

2

121 s, ν(CO) 1972 vs, 1937 s, ν(C=N) 1510 w cm . H NMR: δ = 0.22 (t, 3H, CH -CH , J(H-H)

2 3

=

7.0 Hz), 1.86 (s, 6H, Xylyl-Me), 1.93 (s, 3H, CH ), 2.21 (s, 3H, Xylyl-Me), 3.40 (m, br, 1H,

3

A

B

2

3

CH -CH ), 3.62 (m, br, 1H, CH -CH ), 6.08 (m, 1H, NH, J(Pt-H) = 102.0 Hz), 6.75–7.96 (m,

2

3

41H, Aryl).

4

.5. Preparation of [(CO) LFe{

µ

-CN(R')R}(

µ

-Ph PNPPh )Pt(PR'' )] (6)– To a solution of 5 (0.5

2

3

mmol) in THF (10 ml) are added 3 mmol KOSiMe or KH. After stirring for 30 min., all volatiles

3

are removed under reduced pressure and the yellow residue extracted with Et O (2 x 10 ml). The

2

combined extracts are concentrated and the yellow products precipitated by addition of hexane.

After drying in vacuo, compounds 6 are obtained in analytical pure form. Yields: 80-95%.

2

9

Article Doi

Synthesis and reactivity of bis(diphenylphosphino)amine-bridged heterobimetallic iron-platinum μ-isonitrile and μ-aminocarbyne complexes Dedicated to Prof. Jacques Amaudrut on the occasion of his 75th birthday.

DOI: 10.1016/j.jorganchem.2014.12.028

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Article abstract of DOI:10.1016/j.jorganchem.2014.12.028

Full text of DOI:10.1016/j.jorganchem.2014.12.028

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