Insertion Routes to Tetrasubstituted Guanidinate Complexes of Ta(V) and Nb(V).
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.
Tin
Ma Khin Tan
MK
Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
Yap
Glenn P. A.
GP
Richeson
Darrin S.
DS