Gas phase characterization by photoelectron spectroscopy of unhindered α-heterosubstituted...

Gas phase characterization by photoelectron spectroscopy

of unhindered a-heterosubstituted germylenes [1]

Thierry Pigot, Severine Foucat, Genevieve Pfister-Guillouzo*

Laboratoire de Chimie Theorique et Physico-Chimie Moleculaire, CNRS UMR 5624/ FR 2606, Universite de Pau & des Pays de l’Adour,

Avenue de l’Universite, F-64000 Pau, France

Received 17 September 2004; revised 4 November 2004; accepted 8 November 2004

Available online 28 January 2005

Abstract

Two unhindered a-heterosubstituted (O and S) cyclic germylenes have been generated and characterized by the combination of flash

vacuum thermolysis of stable germacyclopentenes and ultraviolet photoelectron spectroscopy. This coupling associated with ab initio

calculations with the hybrid functional B3LYP and the 6-311G(d) basis set allows to predict the electronic properties of the generated

germylenes. The thermodynamic stabilization of these reactive molecules by electronic delocalization of the heteroatom p lone pairs within

the 4p orbitals of the germanium atom is clearly shown.

q 2004 Elsevier B.V. All rights reserved.

Keywords: UV-photoelectron spectroscopy; Flash vacuum thermolysis; DFT calculations; Germylenes

1. Introduction

Germylenes have been extensively studied for the last

20 years [2]. Most of these compounds, like the silicon or

carbon analogs, are short live species. They could be

indirectly characterized by trapping reactions with various

substrates, i.e. dienes, diones, etc. Without a quencher

present, germylenes easily undergo polymerization. To

avoid the oligomerization, bulky ligands on germanium may

be used. In this case germylene shows a monomeric state in

the gas phase and/or the solid state (kinetic stabilization)

[3]. Another way of stabilizing germylenes can be achieved

by incorporating various special donor groups such as –NH2

[4], –OR [5], –PR [6] (RZsilyl, alkyl, aryl) or by

complexing them with transition metals [7]. Examples of

intramolecular coordination with base ligands can be found

in recent literature [8]. However, these molecules need to

remain quite hindered around the Ge(II) atom, because

otherwise their reactivity is too high to allow characteri-

zation by classical techniques.

0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.molstruc.2004.11.025

* Corresponding author. Tel.: C33 5 59 40 75 82; fax: C33 5 59 40 75

88.

E-mail address: [email protected] (G. Pfister-Guillouzo).

Studies on stable imidazol-2-ylidene [9,10] 2-silaimida-

zol-2-ylidene and 2-germa-imidazol-2-ylidene [12a], have

prove that photoelectron spectroscopy associated with DFT

calculations provide a unique approach to characterize these

molecules.

Electronic structure of diaminogermylene was explored

particularly since the pionnering work of Harris and Lappert

on Ge(N(SiMe3)2)2 [11], mainly 2-germa-imidazol-2-yli-

dene A [12] and 2-germa-imidazolin-2-ylidene B [13].

However, some points on the explanation of the stability of

these species, in particular B [14], are still heavily debated.

These 2-germa-imidazolin-2-ylidene with R:tBu are stable

at room temperature but we described recently [15] the

characterization of a less hindered 2-germa imidazolin-2

ylidene B (R:Et) 2c by ultraviolet photoelectron spec-

troscopy. Much less information is known about the

oxygen or the sulfur substituted germylenes analogs. Their

reactivities have been well described by Dousse and

Lavayssiere [16] and their formation confirmed by mass

spectroscopy [16c].

This paper deals with the characterization of two cyclic

saturated heteroatomic a-substitued germylenes (S, O).

These compounds were generated by flash vacuum

thermolysis (FVT) and characterized directly by UV-PES.

Journal of Molecular Structure 782 (2006) 36–43

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Scheme 1.

T. Pigot et al. / Journal of Molecular Structure 782 (2006) 36–43 37

This coupling FVT/PES has been successfully used in our

laboratory for the detection of low coordinated group 14

compounds [17]. The synthetic pathway used in this work is

the well known cycloreversion of germacyclopentenes

adequately substituted (Scheme 1).

It seems that these experimental conditions exclude the

formation of dimeric species, due to the fact that the

Si(ButNCH2CH2NBut) analog has been shown to undergo

reversible dimerisation upon sublimation [11].

Our experimental results are supported by the estimation

of the energies of the first vertical ionization potentials (IPv),

based on the analysis of the Kohn–Sham orbitals and the

corresponding eigenvalues, as used by Arduengo and

coworkers [9] for the interpretation of photoelectronic

spectra of compounds A and isologues.

All the theoretical evaluations were performed with the

DFT theory ab B3LYP/6-311G(d) level of theory.

These photoelectronic experimental data, with the first

ones published on non-hindered a-hetero-germylenes, allow

us to estimate the influence of the substituent on the

germanium nucleophilicity and to visualize the importance

of the p delocalization.

1.1. Study of thermolysis of sulfur compound 1a

The following is an interpretation of the spectrum for the

precursor which is displayed in Fig. 1a, based on the

experimental data of sila(germa)cyclopent-3-ene serie [18],

cyclogermathianes [19] and dimercaptomethanes [20].

The double bond carbon–carbon cyclopentenic ring

ionization is observed at 8.5 eV. According to the higher

intensity at 8.8 eV, we have attributed this band to two

ionization processes: ejection of an electron from sulfur

atom p lone pair in-phase and out-of-phase combinations.

The sulfur atoms p lone pair out-of-phase combination and

the GeS and GeC bonds are ionized in the second band at

10.4 eV.

At 913 K this PES is modified and it indicates that the

thermolysis of the precursor is complete (Fig. 1b). We

observed the systematic formation of dimethylbutadiene

(DMB) by the characteristic ionization potentials at 8.7,

10.3 and 11.4 eV. The spectrum 1c, which is obtained after

the digital subtraction of the DMB spectrum, could be

associated to the germylenes 2a.

To confirm this hypothesis we have carried out a quantic

study of the privilegied forms of 2a and calculated their

ionization energies.

The geometrical parameters are displayed in Fig. 2. We

highlight a unique minimum on the potential energy surface

for this cyclic compound 2a. The cycle adopts a twisted

conformation to minimize interactions between the meth-

ylene groups (twist angle 388). The angle to germanium is

938, the GeS bond lenght is 2.27 A.

One transition state (TS) has been found on the potential

energy surface of 2a. It corresponds to a coplanar structure,

energetically very close to the minimum (4.58 kc). Thus,

taking into account this small energetic difference, a rapid

interconversion between two twist forms is expected to

occur in gas phase.

The interpretation of PES is made on the basis of

calculated energies of the Kohn–Sham orbitals (3iKS) for 2a

and 2a (TS) (Table 1). Arduengo and co-workers [9] first

used DFT calculations at the non-local level to assign the

PES of 2-germaimidazol-2-ylidene. Werstiuk [21], Rade-

macher [22] and ourselves [23] have verified for different

compounds that 3iKS could be linked to the experimental

vertical ionization potentials by a uniform shift of x.

The value of x is taken as xZ jK3i HOMO K IPcalcIV j. This

approach is justified if the first vertical ionization potential

calculated, IPIVcalc, as the difference between ET(cation) and

ET(molecule) lies very close to experimental values

(Table 1).

Hoffman has recently shown that the localization of KS

orbitals are very similar to those obtained after HF

calculations [24]. So it is possible to identify more precisely

the nature of the first ionization and to interpret unambigu-

ously the photoelectron spectrum.

Fig. 3 shows graphical representation of the first five

occupied KS orbitals and the LUMO for 2a.

The computed DSCF value and estimated values of IP’s

are both in excellent agreement with the experimental data.

The first band at 9.0 eV is attributed to the ejection of an

electron from the out-of-phase p sulfur lone pairs

combination. The ionization of germanium lone pair is

observed at 9.3 eV. The ionization of the in-phase p sulfur

lone pairs combination corresponds to the band at 10 eV.

The bands at 10.3 and 11.9 eV are attributed to the

ionizations of Ge–S bonds and s sulfur lone pairs,

respectively.

We notice that the gap between the ionization energies of

sulfur atoms p lone pairs bonding and antibonding

combinations is 1 eV. This gap shows a clear stabilization

of the bonding combination due to an important delocaliza-

tion from the sulfur atom lone pairs into the germanium

atom pp vacant orbital (Fig. 3 LUMO and HOMO-3). NBO

analysis [25] shows in fact that the germanium pp vacant

orbital is occupied by 0.35 e.

Fig. 1. PE Spectra of 1a at (a) 300 K (b) 913 K and DMB spectrum (c) at 913 K after digital substraction of DMB spectrum.

T. Pigot et al. / Journal of Molecular Structure 782 (2006) 36–4338

In the previously studied nitrogen homologue 2c [15]

(2-germaimidazol-2 germylene) we have observed a 1.4 eV

gap and an occupation of the pp vacant orbital of

germanium of 0.32 e. Nevertheless, in this case the angle

Fig. 2. Optimized structur

to germanium is more acute (858) allowing a spacial

interaction of 2ppN–ppN. In spite of the length of GeS bond

the p delocalization is favored by the 3ppS–4ppGe

overlapping.

es of 2a, 2b and 2c.

Table 1

Kohn–Sham energies (K3i), calculated (IPv cal.), estimated (IPv est.) and vertical ionization potentials for 2a and 2a (TS) with experimental values (in eV)

Nature npKS

nGe KnsCS

npCS

nsKS

KsGe S nsþS

KsC S

2a K3iKS 6.7 7.1 7.6 8 9.5

IPv (calc.) 8.8 9.43

IPv (est.) 8.9 9.3 9.8 10.2 11.7

2a (T.S.) K3iKS 6.6 7.1 7.75 7.8 9.85

IPv (calc.) 8.66 9.23 9.97

IPv (est.) 8.7 9.2 9.85 9.9 11.95

IP (exp.) 8.9 9.3 10 10.2 12


1.2. Study of thermolysis of dioxolane compound 1b

We realized the interpretation of 1b precursor

spectrum displayed in Fig. 4 with the support of

germacyclopentenes, trimeric and tetrameric dimethyl

germoxane [26] photoelectron studies. We have assigned

Fig. 3. Graphical representations of the LUMO a

the first band at 8.7 eV to the germacyclopentenic pCaC

orbital ionization energy. The ionic state associated to

the ejection of an electron from the oxygen atoms p lone

pairs in-phase combination nOpC (strong interaction with

the GeC bonds) is observed at 9.0 eV. The band at

10.0 eV is assigned to the out-of-phase interactions of

nd the five first KS orbitals of 2a, and 2c.

Fig. 4. PE Spectra of 1b at (a) 300 K; (b) 773 K and DMB Spectrum (c) 773 K after digital substraction of DMB spectrum.


the nOpK and the sGe–C out-of-phase. The IP’s associated

to sGeO bonds out-of-phase combination is observed in

the broad signal around 11.4 eV.

Up to 723 K we observed a notable modification of

the spectrum. The characteristic DMB ionizations appear

at 8.7, 10.3 and 11.4 eV (Fig. 4b). After we substract the

PE spectrum of DMB from the thermolysis one we

obtained the spectrum displayed in Fig. 4c. The latter

could correspond to the dioxogermylene 2b PE spectrum.

The reaction of thermolysis is not complete and we

observe at 9 eV the first band of weak intensity of the

precursor.

To confirm this hypothesis, we carried out a

theoretical evaluation of the geometric and electronic

parameters of 2b.

Similar to the sulfur derivatives, we characterized a

minimum on the potential energy surface of 2b in the

fundamental singlet state (Fig. 2). 2b is slightly twisted,

with a twist angle of 238 which is less than in the sulfur

analog. The inversion barrier is calculated to be 0.52 kcal/

mol. According to the NBO the analysis the germanium

atom pp is occupied by 0.25 e. The delocalization of

the lone pairs electrons on the oxygen atoms seems weaker

than in the sulfur derivatives, despite a short GeO distance

Table 2

Kohn–Sham energies (K3i), calculated (IPv cal.), estimated (IPv est.) and vertical ionization potentials for 2b and 2b (TS) with experimental values (in eV)

Nature npKO

nGe KnsCO

npCO

nsKO

KsGe O

2b K3iKS 7.37 7.58 8.57 8.67 9.32

IPv (calc.) 9.75

IPv (est.) 9.75 10.0 11.0 11.1 11.7

2b (T.S) K3iKS 7.56 7.56 8.67 8.67 9.31

IPv (calc.) 9.6 9.94

IPv (est.) 9.6 9.96 11.0 11.0 11.7

IP (exp.) 9.8 10 11 11.6

Table 3

The NBO analysis results

pp (Ge) q (Ge) q (X) s GX (% X) Lone pair Ge (% s)

2a 0.35 0.52 K0.20 72 14s 86p 85.7

2b 0.25 1.18 K0.89 87 22s 77p 86.3

2c 0.32 0.98 K1.04 82 31s 69p 81.6


(1.81 A), resulting in the lower polarizability of oxygen lone

pair electrons but also in a less favorable 2pp–4pp

overlapping with regard to sulfur derivative.

In Table 2 we report the Kohn–Sham orbital energies and

in Fig. 3 the graphical representation of the first five

occupied KS orbitals and the LUMO of 2b. The first ionic

state is evaluated at 9.75 eV for 2b and 9.6 eV for 2b (T.S).

The first band of the spectrum centered at 10 eV (Fig. 4c)

with a shoulder at 9.7 eV can be assigned to the two first

ionizations: out-of-phase p pairs combination of the oxygen

atoms and germanium lone pair. Around 11 eV we find the

in-phase combination of p lone pairs of the oxygen atoms

and out-of-phase combination of s lone pairs of oxygens

and the s GeO bonds.

The bands are large due to the fast inversion of the cycle.

As for the sulfur compound we observe a gap of 1.3 eV

between the ionization associated the out-of-phase and in-

phase p lone pair combinations.

This is in agreement with a delocalization towards the

4pp vacant orbital of the germanium. This gap is close to

the one observed for the nitrogen derivative 2c. For these

two systems the angle to germanium is 898 for O and 848 for

N, favorable to a spacial interaction 2pp–2pp between the

two heteroatoms, which increases the gap. However, in spite

of a GeO length shorter than the Ge–N one, the occupation

of the Ge 4pp orbital is more important for the nitrogen

derivative (mesomeric effect more important).

If the p donation seems less important for the oxygen

derivative than for the sulfur derivative, we observe on an

other hand a clear stabilization (about 0.8 eV) of the

ionization energy of the germanium lone pair.

2. Conclusion

The coupling FVT–PES associated with the ab initio

calculations have allowed an unambiguous characterization

of two homoleptic (O and S) cyclic germylenes. PES allows

a direct visualization of the pp–pp delocalization; stabili-

zation of the ionization potential associated to the ejection

of an electron from the in-phase combination of the

heteroatom lone pairs.

This delocalization, due to the ring-strain, decreases

according to the NBO data in the order of SONOO.

All the synthesis tests for obtaining acyclic dithioger-

mylenes lead to polymer formation, contrary to dioxo

and diamino germylenes. Therefore the pp–pp delo-

calization is not the only bonding feature that can solely

explain the a-heterosubstituted germylenes thermo-

dynamic stabilization. Cioslowski [27] suggested that

for carbenes, the unusual stability is related to the

substantial s back-donation from the carbenic atom to

the adjacent nitrogen atoms. The calculated charge

distribution (Table 3) shows a weak polarization for 2a

compared to 2b and 2c. The electronegativity effect (OONOS) should modify in the same way the nucleophili-

city of the germanium lone pair. We have experimentally

observed, for this lone pair, the ionization potentials in

the following order: O: 10, S: 9.2, N: 8.5 eV.

This points out the difficulty in rationalizing the

importance of s polarization. The order observed for the

germanium lone pair ionization is explained by

the particular hybridization of germanium. The Ge–X

bonds have a strong p character on germanium and the

heteroatom. Due to the respective positions of the energies

of these orbitals with, 4p Ge: 7.90 eV, 3p S: 10.36 eV, 2p O:

13.62 eV and 2p N: 14.53 eV we have observed (NBO data)

a more important participation of the 4 s orbital for Ge–N

bond and therefore a stronger p character for the lone pair

(lower ionization energy).

The calculated gap HOMO-1 and LUMO also allows to

estimate the substituant effects (mesomeric and s attractor).

It is of the same order of magnitude for the oxygen and


nitrogen derivatives and smaller for the sulfur derivatives

(Fig. 3).

This agrees with Ciolowski’s conclusions on carbenes,

especially for germylenes where the p donation is weaker

(overlapping with 4pp orbital) and the retro-donation is

stronger (Ge more electropositive).

To conclude the two effects of both p donating and saccepting of the substituant contribute to the stabilization of

a germylene. For example, the amino group (strong pdonor) and the oxgroup (strong s acceptor both) appear to

be good electron-active substituents. The steric protection,

which is possible for the amino group, explains the success

of the synthesis reported on numerous diamino germylenes.

3. Experimental section

3.1. Coupling FVT–PES

Photoelectron spectra were recorded on an Helectros

0078 spectrometer. This one was monitored by a micro-

computer system supplemented by a digital analogic

converter. The spectra were built with 2000 points and

were accurate within 0.1 eV. They were recorded with

21.21 eV HeI irradiation as photon source and calibrated on

well known helium autoionization at 4.98 eV [HeII(He)]

and nitrogen ones at 15.59 eV.

Thermolysis experiments have been performed with a

short path thermolysis (SPT) with an internal heating device,

STP permitted to analyze both species with short life time

and their decomposition products because of high vacuum

(w10K5 mbar) and short distance (25 mm) minimizing

intermolecular collisions [28]. Under these conditions, it is

estimated that the detection of thermolysis products with life

times from 10K1 to 10K3 could be performed.

4. Computational details

Calculations were performed with the GAUSSIAN 98

program [29–30] using the density functional theory [31].

The various structures were fully optimized at B3LYP level

[32] and the second derivatives were calculated in order to

determine if a minimum or a transition state (one negative

eigen value) existed for the resulting geometry. This

functional is built with Becke’s three parameter exchange

functional [32a] and the Lee–Yang Pair correlation func-

tional [32c].

Graphical representations of the nature of the molecular

orbitals were obtained using MOLDEN program [33]. The

electronic structure of the molecules is examined using the

natural bond orbital (NBO) partitioning scheme [25].

5. Synthesis of precursors

All reactions were carried out under a dry nitrogen

atmosphere. 1H and 13C NMR spectra were recorded on a

Bruker AC 400 MHz spectrometer. Chemical shifts were

reported in ppm relative to TMS as a reference. Mass

spectra were obtained under electron impact (70 eV) after

direct introduction of samples into a 5972 Mass Selective

Detector (Hewlett Packard), only characteristic fragments

are listed. Elementar analysis were performed at the

‘Laboratoire Central d’Analyses du CNRS’, Lyon, France.

6. General procedure

A solution of 1,1-dichloro-2,3-dimethylgermacyclopent-

3-ene (2.5 M) in diethylether was added dropwise to a

suspension of the lithium salt of the ethylendithiol or

ethyleneglycol in stoechiometric proportions (prepared

from thiol or alcool and 1.5 M BuLi in pentane). The

mixture was refluxed for 2 h, then the solvent was removed

in vaccum. The residue was washed with pentane and

filtered to eliminate LiCl. Concentrating by distillation in

vaccum of the resulting oil afforded the desired compound.

1a: bp: 65 8C (0.5 torr), yield: 65%1H NMR (CDCl3): 1.76 (m, 6H, CH3); 2.07 (m, 4H,

CH2Ge); 3.09 (s, 4H, CHsS) 13C NMR (CDCl3): 18.8 (CH3);

30.6 (CH2); 37.1 (CH2); 130.1 (CaO); MS (m/z): 248

(MC%), 166 (M-DMB). Anal. calc. for C8H14S2Ge: C,

38.71%; H, 5.64%. Found: C, 38.04%; H, 5.78%.

1b: bp: 60 8C (0.2 torr), yield: 70% 1H NMR (CDCl3):

1.77 (m, 6H, CH3); 2.22 (m, 4H, CH2); 3.92 (s, 4H, CHs)13C

NMR (CDCl3): 18.8 (CH3); 28.3 (CH2); 32.7 (CH2); 129.0

(CaC); MS (m/z): 216 (MC%), 134 (M-DMB). Anal. calc.

for C8H14O2Ge: C, 44.44%; H, 6.48%. Found: C, 44.02%;

H, 6.14%.

Acknowledgements

G. Pfister-Guillouzo thanks for discussion and technical

support K. Miqueu and JM Sotiropoulos from Pau/UMR

5624/CNRS. We also thank Dr G. Schaftenaar for allowing

us to use his graphic program MOLDEN.

References

[1] Part 68: Application of Photoelectron Spectroscopy to Molecular

Properties. For Part 67: see. K. Miqueu, J.M. Sotiropoulos, G. Pfister-

Guillouzo, V.L. Rudzevich, H. Gornitzka, V. Lavallo, V.D.

Romanenko, Eur. J. Inorg. Chem. (2004) 2289.

[2] (a) Recent reviews on Germylenes Chemistry: J. Barrau, G. Rima,

Coord. Chem. Rev. Part I 178 (1998) 593;

(b) M. Driess, H. Grutzmacher, Angew. Chem. Int. Ed. Eng. 35

(1996) 828;

(c) O. Kuhl, Coord. Chem. Rev. 248 (2004) 411.


[3] P. Jutzi, H. Schmidt, B. Neumann, H.G. Stammler, Organometallics

15 (1996) 741.

[4] (a) M.F. Lappert, P.P. Power, M.J. Slade, J. Chem. Soc. Chem.

Commun. (1979) 369;

(b) M.F. Lappert, M.J. Slade, J.L. Afwood, Zaworotko, J. Chem. Soc.

Chem. Commun. (1980) 621;

(c) R.W. Chorley, P.B. Hitchcok, M.F. Lappert, W.P. Leung, P.P.

Power, M.O. Olmstead, Inorg. Chim. Acta 198 (1992) 203;

(d) A. Meller, C.P. Grabe, Chem. Ber. 118 (1985) 2020.

[5] (a) T. Fjelberg, P.B. Hitchcok, M.F. Lappert, S.J. Smith, A.J. Thorne,

J. Chem. Soc. Chem. Commun. (1985) 939;

(b) B. Cetinkaya I. Gumrukeu M.F. Lappert, J.L. Atwood, R. Shakir,

J. Am. Chem. Soc. 102 (1977) 2088.

[6] M. Driess, R. Janoscheck, H. Pritzkow, S. Rell, U. Winckler, Angew.

Chem., Int. Ed. Ing. 107 (1995) 1746.

[7] N. Tokitoh, K. Manmaui, R. Okazaki, Organometallics 13 (1994) 167.

[8] (a) R.S. Foley, Y. Zhou, G.P.A. Yap, D.R. Richeson, Inorg. Chem. 39

(2000) 924;

(b) A. Filippou, P. Portius, G. Kociok-Kohn, V. Albrecht, J. Chem.

Soc. Dalton Trans. (2000); 1759;

(c) W.P. Leung, L.H. Weng, W. Kuok, Z. Zhou, Z. Zhang, T.C. Mak,

Organometallics 18 (1999) 1482.

[9] A.J. Arduengo, H. Bock, H. Chen, M. Denk, A.D. Dixon, J.C. Green,

W.A. Herrmann, N.L. Jones, M. Wagner, R. West, J. Am. Chem. Soc.

116 (1994) 6641.

[10] M. Denk, J.C. Green, N. Metzler, M.J. Wagner, Chem. Soc. Dalton

Trans. (1994); 2405.

[11] D. Harris, M.J. Lappert, Chem. Soc. Chem. Commun. (1974); 895.

[12] (a) W.A. Herrmann, M. Denk, J. Behm, W. Scherer, F. Klingan,

H. Bock, B. Solouki, M. Wagner, Angew. Chem. Int. Ed. Engl.

(1992); 1485;

(b) O. Kuhl, P. Lonnecke, J. Heinicke, Polyhedron 20 (2001) 2215.

[13] C. Boheme, G. Frenking, J. Am. Chem. Soc. 118 (1996) 2039.

[14] J.F. Lehmann, S.G. Urquhart, L.E. Ennis, A. Hitchcock, K. Hatamo,

S. Gupta, M.K. Denk, Organometallics 18 (1999) 1862.

[15] A. Laporte-Chrostowska, S. Foucat, T. Pigot, V. Lemiere, G. Pfister-

Guillouzo, Main Group Met. Chem. 25 (2002) 55.

[16] (a) H. Lavayssiere, G. Dousse, G. Satge, Rec. Trav. Chim. Pays Bas

107 (1988) 440;

(b) H. Lavayssiere, G. Dousse, G. Satge, Phosphorus Sulfur Silicon

53 (1990) 411;

(c) S. Mazieres, H. Lavayssiere, G. Dousse, G. Satge, Inorg. Chim

Acta 252 (1996) 25.

[17] (a) S. Foucat, T. Pigot, G. Pfister-Guillouzo, H. Lavayssiere,

S. Mazieres, Organometallics 18 (1999) 5322;

(b) V. Metail, S. Joanteguy, A. Chrostowska-Senio, G. Pfister-Guil-

louzo, A. Systerman, J.L. Ripoll, Inorg. Chem. 36 (1972) 1482.

[18] C. Guimon, G. Pfister-Guillouzo, G. Manuel, P. Mazerolles,

J. Organomet. Chem. 149 (1978) 149.

[19] J.L. Garcia, D. Gonbeau, G. Pfister-Guillouzo, M. Roch, J. Weber,

Can. J. Chem. 63 (1985) 1518.

[20] C. Guimon, M.F. Guimon, G. Pfister-Guillouzo, Tetrahedron Lett. 17

(1975) 1413.

[21] (a) H. Muchall, N. Werstiuk, J. Pitters, M. Workentin, Tetrahedron

55 (1999) 3767;

(b) H. Muchall, N. Werstiuk, B. Choudury, J. Ma, J. Warkentin,

J. Pezacki, Can. J. Chem. 76 (1998) 238;

(c) H. Muchall, N. Werstiuk, B. Choudury, Can. J. Chem. 76 (1998)

221.

[22] H. Muchall, P. Rademacher, J. Mol. Struct. 471 (1998) 189.

[23] K. Miqueu, J.M. Sotiropoulos, G. Pfister-Guillouzo,

H. Ramaivonjatovo, J. Escudie, J. Mol. Struct. 545 (2001) 139.

[24] R. Stowasser, R. Hoffmann, J. Am. Chem. Soc. 121 (1999) 3414.

[25] A.E. Reed, L.A. Curtiss, F. Weinhold, Chem. Rev. 88 (1988) 899.

[26] C. Guimon, G. Pfister-Guillouzo, G. Rima, M. El Almine, J. Barrau,

Spectr. Lett. 18 (1985) 7.

[27] J. Cioslowski, Int. J. Quantum Chem. 27 (1993) 309.

[28] Fora detailed description of FVT/PES coupling see: Y. Vallee,

J.L. Ripoll, S. Lacombe, G. Pfister-Guillouzo, J. Chem. Res. (Synop.)

(1990); 40.

[29] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,

J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery, R.E. Stratman,

J.C. Burant, S. Dapprich, J.M. Millam, A.D. Daniels, K.N. Kudin,

M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B.

Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A.

Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, D.K. Malick, A.D.

Rabuck, K. Raghavachari, J.B. Foresman, J. Cioslowswi, J.V. Ortiz,

A.G. Baboul, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.

Komaromi, R. Gomperts, R. Martin, D.J. Fox, T. Keith, M.A. Al-

Laham, C.Y. Peng, A. Nanayakkara, C. Gonzalez, M. Challacombe,

P.M.W. Gill, B. Jonhson, W. Chen, M.W. Wong, J.L. Andres, M.

Head-Gordon, E.S. Replogle, J.A. Pople, GAUSSIAN 98, Revision A.7,

Gaussian, Inc., Pittsburgh PA, 1998.

[30] W.J. Hehre, L. Radom, P.v.R. Schleyer, J.A. Pople, Ab Initio

Molecular Orbital Theory, Wiley, New York, 1986.

[31] R.G. Parr, W. Yang, Functional Theory of Atoms and Molecules in:

R. Breslow, J.B. Goodenough (Eds.),, Oxford University Press, New

York, 1989.

[32] (a) A.D. Becke, Phys. Rev. A38 (1988) 3098;

(b) A.D. Becke, J. Chem. Phys. 98 (1993) 5648;

(c) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B37 (1988) 785.

[33] G. Schaftenaar, J.H. Noordik, J. Comput. Aided Mol. Des. 14

(2000) 123.

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