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Carbonyl−Metal Clusters with Mixed O,N-Donor Ligands:  Reactivity of the Ureato Cluster [Ru3(μ-H)(μ3-HNCONMe2)(CO)9] with Phosphines. Structural Characterization of a Triphenylphosphine Derivative and of a Bis(diphenylphosphido) Derivative Which Also Contains a Bridging η1-Phenyl Ligand

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posted on 1997-09-02, 00:00 authored by Javier A. Cabeza, Ignacio del Río, Víctor Riera, Santiago García-Granda, S. Bamidele Sanni
The ureato-bridged carbonyl cluster [Ru3(μ-H)(μ3-HNCONMe2)(CO)9] (1) (H2NCONMe2 = N,N-dimethylurea) reacts with 1 equiv of triphenylphosphine or diphenylphosphine to give the isostructural derivatives [Ru3(μ-H)(μ3-HNCONMe2)(L)(CO)8] (L = PPh3, PPh2H). The X-ray structure of [Ru3(μ-H)(μ3-HNCONMe2)(PPh3)(CO)8] indicates that the substitution has taken place on an equatorial position cis to the bridging NH fragment. Treatment of 1 with bis(diphenylphosphino)methane (dppm) affords a mixture of the symmetric (Cs) and asymmetric (C1) isomers of [Ru3(μ-H)(μ3-HNCONMe2)(μ-dppm)(CO)7]. All these reactions take place at room temperature. The phenyl-bridged bis(diphenylphosphido) derivative [Ru3(μ-η1-Ph)(μ3-HNCONMe2)(μ-PPh2)2(CO)6] has been prepared by reaction of 1 with 2 equiv of PPh3 in the presence of alumina and has been characterized by X-ray diffraction methods. The thermolysis of [Ru3(μ-H)(μ3-HNCONMe2)(PPh2H)(CO)8] in refluxing THF leads to the phosphido-bridged derivatives [Ru33-HNCONMe2)(μ-PPh2)(μ-CO)2(CO)6] and [Ru3(μ-H)(μ3-HNCONMe2)(μ-PPh2)2(CO)6]. It has been observed that carbonyl substitution reactions on compound 1 are easier than those previously reported on clusters containing N- and/or P-donor bridging ligands. This seems to be related to the hard−soft character of the bridging ligand:  the harder the ligand the more reactive is the cluster in carbonyl substitution reactions.

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