Insertion Routes to Tetrasubstituted Guanidinate Complexes of Ta(V) and Nb(V)

Abstract

The preparation and characterization of guanidinate-containing complexes of Nb and Ta is described. The direct reactions of M(NMe(2))(5) with either dicyclohexylcarbodiimide (CyN=C=NCy) and diisopropylcarbodiimide ((i)PrN=C=N(i)Pr) proceeded smoothly at room temperature under nitrogen to yield [RNC(NMe(2))NR]M(NMe(2))(4) (M = Ta, Nb; R = Cy, (i)Pr). The spectroscopic characterization of these materials is consistent with a symmetrical chelating bidentate guanidinate anion bonded to a pseudo-octahedral metal center. Confirmation of these details was provided by a single-crystal X-ray diffraction study in the case of [CyNC(NMe(2))NCy]Ta(NMe(2))(4) (1). Delocalization of the lone pair of electrons on the guanidinate NMe(2) group into the ligand N-C-N pi system does not appear to be significant in these species.

Guanidinate anions and dianions. Reactions involving alkylguanidines, (RNH)2CNR (R = i-Pr or Cy), and metal amido complexes M(NMe2)5 (M = Ta or Nb)

“…two NMe 2 groups cis to the Cl atom and one NMe 2 in trans position). This structural proposition is endorsed by our results with monoanionic tetrasubstituted guanidinates for which we observed species with structures represented by III 11 and the structural results presented below.…”

Guanidinate-Stabilized Monomeric Hafnium Amide Complexes as Promising Precursors for MOCVD of HfO2

“…24 Moreover, guanidinate ligands provide tuneability in terms of steric and electronic properties, by variation of the substituents R and R′ and, hence, are used extensively for many elements across the periodic table. [24][25][26][27][28][29][30][31][32][33][34][35][36] As a part of our research interest in the precursor chemistry of Hf, we undertook the synthesis of a range of hafnium amides with a stabilizing guanidinate ligand system. The bidentate chelating effect of the guanidinate ligands is expected to enhance the thermal/chemical stability of the resulting metal complexes and thus make them suitable precursors for the MOCVD and ALD of HfO 2 .…”

Synthesis of Guanidine Derivatives and Molecular Recognition

“…In addition, the complexes of transition metals with guanidine and their derivates, including 1,1,3,3-tetramethyl-guanidine, were of considerable interest to chemists. [7][8][9][10] To our knowledge, however, there were few previous examples of complexes containing acyl guanidine ligands which have been structurally characterized. [11] When we attempt to prepare new guanidine complexes with transition metals, unexpectedly, we obtained crystal of 4a, which is suitable for X-ray analysis.…”

“…nidine derivatives (3)(4) have the abilities of molecular recognition for phosphate (6)(7)(8)(9) and adipate (10). The other molecular recognition details of these compounds will be published elsewhere.…”