Synthesis of a Ruthenium(II) Complex Containing an [11]ane-P₂C^NHC(NHC = Imidazolidin-2-ylidene) Macrocycle

Abstract

Reaction of [RuCl(Cp)(PPh 3 ) 2 ] with bis[di(2-fluorophenyl)phosphino]benzene, 3, yields complex [RuCl(Cp)(3)], [4]. The chloro ligand in [4] can be exchanged for the 2-azidoethyl isocyanide ligand 2, giving complex [Ru(Cp)(2)(3)]Cl, [5]Cl, which reacts with NH 4 BF 4 to give [5]BF 4 . The azido group of the coordinated isocyanide ligand in [5]Cl or [5]BF 4 can be reduced with Zn/NH 4 Cl/H 2 O to give the complex with the 2-aminoethyl isocyanide ligand. This ligand is not stable but cyclizes by an intramolecular nucleophilic attack of the amino group at the isocyanide carbon atom to give an NH, NH-stabilized NHC ligand in complexes [6]X (X = Cl, [6]Cl; X = 0.5 ZnCl 4 , [6] 2 (ZnCl 4 ); X = BF 4 , [6]BF 4 ). Deprotonation of the NH,NH-stabilized NHC ligands in cations of type [6] þ leads to an intramolecular nucleophilic attack of the amido nitrogen atoms at the fluorinated phenyl groups of the diphosphine ligand under formation of the complex with the facially coordinated macrocyclic [11]ane-P 2 C NHC ligand [1]X (X = Cl, [1]Cl; X = 0.5 ZnCl 4 , [1] 2 (ZnCl 4 ); X = BF 4 , [1]BF 4 ). Formation of the macrocycle is facilitated by the steric pressure excerted by the cyclopentadienyl ligand. The molecular structures of [4], [5]BF 4 , [6]BF 4 3 CH 2 Cl 2 , and [1]Cl 3 CH 2 Cl 2 3 0.5H 2 O have been determined by X-ray diffraction.

Complexes Bearing Protic N-Heterocyclic Carbene Ligands

“…The application of this protocol to ruthenium , and platinum complexes, along with investigations on deprotection conditions, have been explored. Hahn also described the azide-to-amine deprotection–cyclization sequence of ω-azidoalkyl isocyanides CN­(CH 2 ) n N 3 ( n = 2, 3), which provides saturated, protic diaminocarbene complexes of tungsten, manganese, rhenium, iron, ruthenium, ,, and platinum. , Ligation of an electron-donating phosphine again suppresses the cyclization . Reactions of the homologues of 128 and 135 , 2-CNC 6 H 4 CH 2 X (X = OSiMe 3 , or N 3 , ), have been described by Michelin …”

“…Intramolecular nucleophilic substitution at the 2-fluorophenylphosphine ligand in rhenium, ,, manganese, ruthenium, and iron complexes of type 196 results in formation of the facially coordinated, macrocyclic mixed-donor NHC complexes 197 (Scheme ).…”

“…222 Liberation of the amino group in the isocyanide complexes 136 was achieved by a Staudinger reaction, 223 followed by hydrolysis of the resulting The application of this protocol to ruthenium 224,225 and platinum 226 complexes, along with investigations on deprotection conditions, 224 have been explored. Hahn also described the azide-to-amine deprotection−cyclization sequence of ω-azidoalkyl isocyanides CN(CH 2 ) n N 3 (n = 2, 3), which provides saturated, protic diaminocarbene complexes of tungsten, 227 manganese, 183 rhenium, 224 iron, 228 ruthenium, 224,225,229 and platinum. 230,231 Ligation of an electron-donating phosphine again suppresses the cyclization.…”

Non-Classical Anionic Naked N-Heterocyclic Carbenes: Fundamental Properties and Emerging Applications in Synthesis and Catalysis

“…This was first demonstrated by Angelici et al in 1987 [69], in which the deprotonation of protic oxazolidin-2-ylidene iron complex 11 and the subsequent addition of electrophiles afforded a range of N-functionalized metal complexes 13 (Scheme 5). Hahn et al have further exploited this reactivity for the template synthesis of organometallic macrocycles [70] and the stereoselective synthesis of facially coordinated tridentate mixed donor ligands [71][72][73][74][75]. Of particular interest is the intermediate 12, which features a nitrogen atom bearing a formal negative charge, and its corresponding bimetallic complex 13c.…”

Carbene Complexes Derived from Metal‐Bound Isocyanides: Recent Advances

“…Reduction of the azido group of the coordinated isocyanide with Zn/NH 4 Cl/H 2 O generates the 2 -aminoethyl isocyanide ligand that cyclizes intramolecularly to produce a metal -bound NH,NH -NHC species. Deprotonation of the thus -obtained NHC ligands results in an intramolecular nucleophilic attack of the amido nitrogen atoms at the fl uorinated phenyl groups of the diphosphine ligand to afford a complex with the facially coordinated macrocyclic [11]ane -P 2 C NHC species (Figure 15.2 , c ) [50] .…”