Elsevier

Inorganica Chimica Acta

Volume 261, Issue 1, 15 August 1997, Pages 117-120
Inorganica Chimica Acta

Note
Substitution reactions in dinuclear molybdenum(III) thiolato-complexes induced by isocyanato ligands

https://doi.org/10.1016/S0020-1693(96)05583-1Get rights and content

Abstract

The reactions of [Cp′2Mo2(CO)4(μ-SR)2](BF4)2 with azido compounds proceeds via a mechanism analogous to the Curtius rearrangement to afford isocyanate species [Cp′2Mo2(NCO)(CO)3(μ-SR)2](BF4) (Cp′=C5H5, R=Me 1, Ph 2; Cp′=C5Me5, R=Me 3). Thermal substitution of CH3CN or R′NC (R′=t-Bu, xylyl, benzyl) for CO in 13 results in the formation of monosubstituted derivatives [Cp′2Mo2(NCO)(CO)2(L)(μ-SR)2](BF4) (L=CH3CN: Cp′=C5H5, R=Me 4, Ph 5 ; Cp′=C5Me5, R=Me 6 ; L=R′NC: Cp′=C5Me5, R=Me, R′=t-Bu 7, xylyl 8, benzyl 9).

Introduction

We have investigated for some years the influence of metal centres and of the sulfur substituents R or the Cp′ rings (C5H5, C5Me5) on the electrochemical behaviour and the reactivity of complexes possessing {Cp′2M2(μ-SR)n} core (n=1–3, M=Mo, W, V) 1, 2. We were particularly interested to generate substrate-binding sites and to control their selectivity. Very recently we have reported that the substitution of C5H5 (Cp) rings by the C5Me5 (Cp*) ligands in the series of complexes [Cp′2Mo2(CO)4(μ-SR)2](BF4)2 (Cp′=C5H5, C5Me5) affects the life time of intermediates produced in the reduction processes [2]b and lowers the reactivity of these complexes [2]. Cp* compounds show greater resistance to decarbonylation than their Cp analogues, no substitution of carbonyl by acetonitrile is observed when [Cp*2Mo2(CO)4(μ-SR)2](BF4)2 is stirred in refluxing MeCN [2]a. A way to activate such inert carbonyl complexes is to introduce into the metallic framework a halide or pseudo-halide ligand [3]. We have tried to activate toward carbonyl substitution the inhibited pentamethylcyclopentadienyl complex [Cp*2Mo2(CO)4(μ-SR)2](BF4)2 by transforming one carbonyl group into an isocyanate ligand. Here we report the reaction of the dicationic compound [Cp′2Mo2(CO)4(μ-SR)2](BF4)2 with natrium azide NaN3, giving the isocyanate products [Cp′2Mo2(NCO)(CO)3(μ-SR)2](BF4) (Cp′=C5H5, R=Me 1, R=Ph 2; Cp′=C5Me5, R=Me 3). The reactivity of nitrile (CH3CN) and isocyanide (t-BuNC, xylyNC) towards these isocyanate complexes has been investigated and compared to that with the dicationic tetracarbonyl precursor [Cp′2Mo2(CO)4(μ-SR)2]2+. We show that the presence in the complexes of a pseudo-halide ligand labilises these dinuclear compounds to carbonyl substitution.

Section snippets

Results

A red solution of [Cp′2Mo2(CO)4(μ-SR)2](BF4)2 in acetonitrile reacted instantaneously with one equivalent of NaN3 in ethanol to give a brown solution from which were isolated the isocyanate products [Cp′2Mo2(NCO)(CO)3(μ-SR)2](BF4) (Cp′=C5H5, R=Me 1, R=Ph 2; Cp′=C5Me5, R=Me 3) 13 in quantitative yields (Reaction 1).

These new compounds have been characterised by various spectroscopic methods (1H and 13C NMR, IR) (Table 1) and elemental analyses. 1H and 13C NMR spectroscopy of 13 shows the

Discussion

The reaction of N3 with the dinuclear tetracarbonyl complexes [Cp′2Mo2(CO)4(μ-SR)2]2+ leads to the isocyanate products via a mechanism analogous to the Curtius rearrangement which has been proposed by Beck and coworkers with carbonyl monometallic compounds [LnM–CO] [5]. Some examples of di- or polymetallic isocyanate products have been reported. Gladfelter et al. have described the trinuclear ruthenium complex [Ru3(NCO)(CO)4] obtained by reaction of [Ru3(CO)12] with N3 [6]. Other polynuclear

General procedures

The reactions were performed under either a nitrogen or an argon atmosphere using standard Schlenk techniques, and solvents were deoxygenated and dried by standard methods. Literature methods were used for the preparation of [Cp′2Mo2(CO)4(μ-SR)2](BF4)2 (Cp′=Cp [4], Cp′=Cp* [2]a).

Infrared spectra were obtained with a Perkin-Elmer 1430 spectrophotometer. NMR spectra were recorded on a Bruker AC300 spectrophotometer. Peak positions were relative to tetramethylsilane as an internal reference.

References (11)

  • (a) M. El Khalifa, M. Guéguen, R. Mercier, F.Y. Pétillon, J.Y. Saillard and J. Talarmin, Organometallics, 8 (1989) 140;...
  • (a) P. Schollhammer, F.Y. Pétillon, R. Pichon, S. Poder-Guillou, J. Talarmin, K.W. Muir and L. Manojlović-Muir,...
  • (a) L.A.P. Kane-Maguire, M. Manthey and B. Robinson, J. Chem. Soc., Dalton Trans., (1995) 905; (b) J.K. Shen and F....
  • J. Courtot-Coupez, M. Guéguen, J.E. Guerchais, F.Y. Pétillon, J. Talarmin and R. Mercier, J. Organomet. Chem., 312...
  • (a) W. Beck, J. Organomet. Chem., 383 (1990) 143; (b) Z. Dori and R.F. Ziolo, Chem. Rev., 73 (1973)...
There are more references available in the full text version of this article.

Cited by (5)

View full text