Oxido‐ and Sulfidoniobium(V) N,N‐Diethylcarbamates: Synthesis, Characterization and DFT Study

Abstract

N,N‐Diethylcarbamates [NbE(O2CNEt2)3] (E = O, S) have been prepared in high yields by treating NbOCl3 or [NbSCl3(CH3CN)2] with CO2/NHEt2 in toluene at approximately –10 °C. The products were characterized by spectroscopic techniques, elemental analysis and X‐ray diffractometry in the case of [NbO(O2CNEt2)3]. The molecular structure of the latter consists of a niobium centre coordinated to the oxido moiety and six O atoms belonging to bridging and bidentate carbamates, in a slightly distorted pentagonal‐bipyramidal arrangement. The structures of both [NbE(O2CNEt2)3] compounds were reproduced by DFT calculations, which show substantial similarity despite the different nature of the chalcogen atoms.

Recent Advances in the Chemistry of Metal Carbamates

“…More in general, metal chlorido complexes can be used as precursors for the installation of carbamato unit(s) [166,171,[231][232][233] Other metal compounds, such as Dy(III) [235], Fe(II) [236], Cu(II) [237][238][239][240][241], Ni(II) [239] and Zn(II) [240][241][242][243] perchlorates, nitrates and sulfates, uranyl diacetate [244] Other metal compounds, such as Dy(III) [235], Fe(II) [236], Cu(II) [237][238][239][240][241], Ni(II) [239] and Zn(II) [240][241][242][243] perchlorates, nitrates and sulfates, uranyl diacetate [244] or [Pd(MeCN) 4 ] 2+ [245] were used as starting materials for the preparation of carbamato derivatives. The reactions are usually carried out in polar organic solvents (MeOH, MeCN) in the presence of amines, polyamines or aza-macrocyclic ligands under CO 2 atmosphere (Scheme 23a).…”

“…The aggregation is realized by bridging coordination of the carbamato moieties, as well as metal-metal bonding in some cases, and can be regulated by the nitrogen substituents, with bulkier groups usually favoring a lower degree of aggregation. For instance, [Ti(O 2 CNR 2 ) 4 ] (R = Me, Et, i Pr, pyrrolidine; Scheme 17 a) and [Nb(O 2 CNR 2 ) 5 ] (R = Me, Et; Scheme 17 c) are examples of mononuclear complexes featuring only chelating ( C/1 ) or chelating ( C/1 ) and monodentate ( M/1 ) carbamates, respectively [ 130 , 171 , 172 , 173 , 174 ]. On the other hand, homoleptic diethyl or dimethyl carbamato derivatives of W(III), Mo(II) and Sn(II) ( Scheme 16 c) are dinuclear, featuring bridging ligands ( B/2 ) and the first two complexes also M-M bonding [ 136 , 175 , 176 ].…”

“…More in general, metal chlorido complexes can be used as precursors for the installation of carbamato unit(s) [ 166 , 171 , 231 , 232 , 233 ]. In this setting, treating TiCp* 2 Cl, VOCl 3 and NbOCl 3 with pre-carbonated amines respectively allowed the isolation of [TiCp* 2 (O 2 CNEt 2 )] [ 234 ], [VO(NMe 2 )(O 2 CNMe 2 ) 2 ] [ 166 ] and [NbO(O 2 CNEt 2 ) 3 ] 2 [ 171 ] ( Scheme 22 a). Similarly, ruthenium(II) complexes mer -[RuCl(O 2 CN i Pr 2 )(PPh 3 ) 3 ] and [Ru(O 2 CN i Pr 2 ) 2 (PPh 3 ) 2 ] were prepared by chloride/carbamate exchange from [RuCl 2 (PPh 3 ) 3 ] and the chloro-bridged dimer [Ru 2 Cl 5 (PPh 3 ) 4 ] − , respectively ( Scheme 22 b) [ 231 ].…”

“…Instead, [Nb(O 2 CNEt 2 ) 5 ] treated with circa 1 eq. of water in toluene afforded a product of presumable formula [Nb 2 O 3 (O 2 CNEt 2 ) 4 ], being reminiscent of the structurally characterized [Ta 2 (µ-O) 3 (O 2 CNEt 2 ) 4 ] 4 based on IR and NMR spectra [ 171 ].…”

“…TiCl 4 with one equivalent of preformed [TMG][O 2 CNEt 2 ] (TMG = tetramethylguanidine), leading to the trinuclear [TiCl 2 (O 2 CNEt 2 ) 2 ] 3[109]. Interestingly, the co-product is not the expected guanidinium chloride but the hexachlorometalate [TMG] 2 [TiCl 6 ] (probably formed via addition of chlorides to unreacted TiCl 4 ), which can be easily removed by filtration.More in general, metal chlorido complexes can be used as precursors for the installation of carbamato unit(s)[166,171,[231][232][233]. In this setting, treating TiCp* 2 Cl, VOCl 3 and NbOCl 3 with pre-carbonated amines respectively allowed the isolation of [TiCp* 2 (O Drawings based on published data[220,221,225,227,228], H atoms omitted for clarity.…”