<i>N</i>-Heterocyclic Silylenes as Metal–Metal Bridges and Metal–Halide Activators in Transition Metal Complexes
Mirjam J. Krahfuß, Udo Radius
Abstract
Several examples are provided that NHSi (N-heterocyclic silylene) ligands are much better metal–metal bridging ligands as compared to NHCs and that NHSi also tends to insert much more easily into metal–halide bonds of transition metal complexes. Dipp2NHSi (1,3-bis(2,6-diisopropyphenyl)-1,3-diaza-4-silacyclopent-4-en-2-yliden) reacts with [{(η5-C5H5)Fe(CO)2}2] and [(η5-C5H5)2Ni] to yield, in contrast to the results obtained for analogous transformations with NHCs, the dinuclear silylene-bridged complexes [{(η5-C5H5)Fe(CO)}2(μ-CO)(μ-Dipp2NHSi)] (1) and [{(η5-C5H5)Ni(μ-Dipp2NHSi)}2] (2). The reaction with [(η5-C5H5)Ni(PPh3)(Cl)] leads with insertion of the silylene into the nickel–chloride bond to [(η5-C5H5)Ni(PPh3)(Dipp2NHSi-Cl)] (3). [Mn(CO)5(Cl)] reacts with 2 equiv of Dipp2NHSi to afford [Mn(CO)4(Dipp2NHSi)(Dipp2NHSi-Cl)] (5), in which one of the silylenes has inserted into the Mn–Cl bond and acts as a chloro silyl ligand. The reaction of 2 equiv of Dipp2NHSi with the corresponding iodide complex [Mn(CO)5(I)] leads to formation of the bis-silylene complex [Mn(CO)3(Dipp2NHSi)2(I)] (4).