Activation of Organic Substrates on Multi-Metallic Sites of Transition Metal Polyhydride Clusters Having C5Me5 Groups as Auxiliary Ligands

Abstract

An overview of the chemistry of the di‐ and trinuclear transition metal polyhydride complexes containing only C5Me5 groups as auxiliary ligands is presented. The synthesis of a series of η5‐C5Me5 polyhydride clusters and their reactivities centered about some typical examples of “multi‐metallic activation” including the cleavage of carbon−hydrogen bonds of alkanes, carbon‐carbon bond of cyclopentadiene, and carbon−carbon double bond of 1,1‐disubstituted alkenes, achieved on the reaction site of the polyhydride‐bridged clusters, are reported. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Insertion and C–C coupling processes in reactions of the unsaturated hydride [W2Cp2(H)(μ-PCy2)(CO)2] with alkynes

“…2 The electronic and coordinative unsaturation inherent to these species typically provides them with a high reactivity towards a wide variety of reagents under mild conditions, as exemplified by the extensive chemistry developed around the polyhydrides [M 2 Cp* 2 (-H) 4 ] (M = Fe, Ru), 3 and [M 2 ( 6 -C 6 Me 6 ) 2 (-H) 3 ] + (M = Ru, Os), 4 or that one carried out by our group for the dimolybdenum hydride [Mo 2 Cp 2 (-H)(-PCy 2 )(CO) 2 ]. 5 Remarkably, our work with the ditungsten hydride 1 has revealed that the change of metal (W instead of Mo) has significant effects on the structure and reactivity of these unsaturated molecules.…”

Searching for molecular arene hydrogenation catalysis in ionic liquids

“…The implication from this comparison is that the active catalyst is not homogeneous, but heterogeneous, such as soluble nanoparticles. The essentially complete inactivity of these hydride complexes in neat benzene and [C 4 C 1 im][BF 4 ] was not anticipated, especially, as it has been demonstrated earlier that these compounds are capable of activating numerous organic substrates such as nitriles, thiols, alkenes and alkynes [35].…”

Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10]−

“…3). These compounds have been tentatively formulated as two isomers of the [Re 3 ( -H) 3 ( -2 -N 2 C 4 H 3 )(pymd)(CO) 9 ] − anion (see Scheme 4), on the bases of their hydridic δ values (see Table 1), quite similar to those of the previously known derivative [Re 3 ( -H) 3 ( -2 -NC 5 H 4 )(py)-(CO) 9 ] − , containing a pyridine terminally coordinated on the vertex of the cluster [19]. The two isomers 7a and 7b have been obtained in higher amounts by heating 1 in pyrimidine at 85 • C for 2 h, thus allowing their complete NMR characterisation.…”

“…The mean Re-N bond length in 3 (2.171(12) Å) can not be compared with other Re-pyridazine bond lengths, however it falls in the range observed for analogous complexes in which sp 2 nitrogen atoms are involved in a -2 bridge between two rhenium atoms (see for example the values of 2.168(3), 2.178(9), and 2.18(2) Å found in [Re 3 ( -H) 3 ( -2 -pz)(CO) 9 …”

“…It is known in fact that stable organometallic compounds can provide good models of the reactive intermediates in both homogeneous and heterogeneous catalytic processes. A particular interest is devoted to systems able to activate C-H bonds of organic ligands co-ordinated on metal clusters and several examples of these complexes have been described [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. 2 …”