N-Heterocyclic Silylenes as Metal–Metal Bridges and Metal–Halide Activators in Transition Metal Complexes

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. Dipp 2 NHSi (1,3-bis(2,6-diisopropyphenyl)-1,3-diaza-4silacyclopent-4-en-2-yliden) reacts with [{(η 5 -C 5 H 5 )Fe(CO) 2 } 2 ] and [(η 5 -C 5 H 5 ) 2 Ni] to yield, in contrast to the results obtained for analogous transformations with NHCs, the dinuclear silylene-bridged complexes [{(η 5 -C 5 H 5 )Fe(CO)} 2 (μ-CO)(μ-Dipp 2 NHSi)] ( 1) and [{(η 5 -C 5 H 5 )Ni(μ-Dipp 2 NHSi)} 2 ] (2). The reaction with [(η 5 -C 5 H 5 )Ni(PPh 3 )(Cl)] leads with insertion of the silylene into the nickel− chloride bond to [(η 5 -C 5 H 5 )Ni(PPh 3 )(Dipp 2 NHSi-Cl)] (3). [Mn(CO) 5 (Cl)] reacts with 2 equiv of Dipp 2 NHSi to afford [Mn(CO) 4 (Dipp 2 NHSi)(Dipp 2 NHSi-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 Dipp 2 NHSi with the corresponding iodide complex [Mn(CO) 5 (I)] leads to formation of the bis-silylene complex [Mn-(CO) 3 (Dipp 2 NHSi) 2 (I)] (4).

Carbazole Substituted Amidinato Silylene: Synthesis, Bonding, and Coordination Behavior with Coinage Metals

“…This reaction behavior is presumably due to the halophilic nature of the silylene. 34 The formation of 5 was serendipitous as we intended to see the complexation of 1 with CuSPh, and for the preparation of CuSPh, we used CuI and LiSPh. Assuming the generation of CuSPh in situ, we added an equivalent amount of 1 in the reaction mixture.…”

“…To our surprise, the reaction of 1 with CuBr 2 led to the formation of 4 along with the side product [PhC­(N t Bu) 2 Si­(Cbz)­Br 2 ]. This reaction behavior is presumably due to the halophilic nature of the silylene …”

A square planar silylene nickel four-membered ring

“…In general, four-membered [M-Si(II)] 2 -rings (M = transition metal) are rare [50][51][52][53] and only a few examples are known for Ni. [54][55][56][57][58] However, the bonding situation and the nature of the silylene is different in those complexes (Scheme 2).…”

“…In analogy to the procedure in small Scheme 2 Literature known Si 2 Ni 2 compounds and the title complex. [54][55][56][57] four-membered ring molecules which was intensely investigated, 63 the force constant of the out-of-plane motion is determined according to the method of Wilson, Decius and Cross. 64 Using the G-matrix element G oop = 1/2(μ Si + μ Ni ), 63 the unusually large force constant value of 1.92 mdyn•Å −1 is thus obtained, which is indicative of a rather rigid Ni 2 Si 2 framework.…”

Antibacterial activity, synthesis and characterization of a new Ag(I) and Pd(II) complexes with N-heterocyclic carbene

“…Numerous methods have been used to examine the creation of NHC metal complexes. 16,17,18 Metal complexes of N-Heterocyclic Carbenes can be made using a number of different techniques. The following is a list of the three most popular routes.…”