Formation of n-Butyldiazoate by Reaction of [M(CN)5NO]2- (M = Fe, Ru, Os) with Lithium n-Butylamide

TRÁPANI, C.; ESCOLA, N.; DOCTOROVICH,* F.

ORGANOMETALLICS

American Chemical Society

Año: 2002 vol. 21 p. 2021 - 2023

0276-7333

Summary: The reactions of [M(CN)5NO]2- (M ) Fe, Ru, Os) with lithium n-butylamide are reported for the first time. Free (E)-n-butyldiazoate was found as the only product arising from the amide. This result and the reinvestigation of the reactions of n-butylamine with [Fe(CN)5NO]2- and [Ru(bpy)2(NO)Cl]2+ give a strong indication that diazoates (and/or diazoic acids) are intermediates in the reactions of amines with these nitrosyl complexes. Our group is exploring the possibility of obtaining stabilized diazonium ions by reaction of primary amines with coordinated nitrosyl ligands. This route was first pointed out by Meyer et al.,1 who obtained aromatic diazonium salts stabilized by coordination to ruthenium through the reaction of [Ru(bpy)2(NO)Cl]2+ with aniline and other aromatic amines. In previous works we have studied the reaction of n-butylamine, benzylamine, and other aliphatic amines with [Fe(CN)5NO]2- and [Ru(bpy)2(NO)Cl]2+ (bpy is 2,2’- bipyridyl),2-5 finding evidence for the stabilization by coordination of the corresponding diazonium salts. In this work we have explored for the first time the reaction of lithium n-butylamide with [M(CN)5NO]2- (M) Fe, Ru, Os). n-Butylamide has the advantage over n-butylamine of being a much more potent nucleophile. This not only accelerates a nucleophilic attack to NO but also brings up the possibility of using nitrosyl complexes which are not electrophilic enough for reacting with amines. Although in previous works1-5 diazoates (RNdNO-) and diazoic acids were proposed as intermediates for the formation of diazonium salts in reactions of amines with these nitrosyl complexes, there was no evidence supporting this suggestion. In this work we provide strong evidence indicating that the formation of diazonium salts in these reactions occurs via the corresponding diazoates. When a THF solution of lithium n-butylamide6 was added at 0 °C to a pyridine solution of (tba)2[Fe(CN)5NO] (tba is the tetra-n-butylammonium ion), the initially pale yellow solution turned brown immediately. 13C NMR of the reaction mixture in pyridine-THF-C6D6 showed four signals of almost equal intensity at ä (ppm) 14.1, 20.7, 30.0, and 54.1, corresponding to (E)-nbutyldiazoate. 9 The only other observed product was 5NO]2- (M ) Fe, Ru, Os) with lithium n-butylamide are reported for the first time. Free (E)-n-butyldiazoate was found as the only product arising from the amide. This result and the reinvestigation of the reactions of n-butylamine with [Fe(CN)5NO]2- and [Ru(bpy)2(NO)Cl]2+ give a strong indication that diazoates (and/or diazoic acids) are intermediates in the reactions of amines with these nitrosyl complexes. Our group is exploring the possibility of obtaining stabilized diazonium ions by reaction of primary amines with coordinated nitrosyl ligands. This route was first pointed out by Meyer et al.,1 who obtained aromatic diazonium salts stabilized by coordination to ruthenium through the reaction of [Ru(bpy)2(NO)Cl]2+ with aniline and other aromatic amines. In previous works we have studied the reaction of n-butylamine, benzylamine, and other aliphatic amines with [Fe(CN)5NO]2- and [Ru(bpy)2(NO)Cl]2+ (bpy is 2,2’- bipyridyl),2-5 finding evidence for the stabilization by coordination of the corresponding diazonium salts. In this work we have explored for the first time the reaction of lithium n-butylamide with [M(CN)5NO]2- (M) Fe, Ru, Os). n-Butylamide has the advantage over n-butylamine of being a much more potent nucleophile. This not only accelerates a nucleophilic attack to NO but also brings up the possibility of using nitrosyl complexes which are not electrophilic enough for reacting with amines. Although in previous works1-5 diazoates (RNdNO-) and diazoic acids were proposed as intermediates for the formation of diazonium salts in reactions of amines with these nitrosyl complexes, there was no evidence supporting this suggestion. In this work we provide strong evidence indicating that the formation of diazonium salts in these reactions occurs via the corresponding diazoates. When a THF solution of lithium n-butylamide6 was added at 0 °C to a pyridine solution of (tba)2[Fe(CN)5NO] (tba is the tetra-n-butylammonium ion), the initially pale yellow solution turned brown immediately. 13C NMR of the reaction mixture in pyridine-THF-C6D6 showed four signals of almost equal intensity at ä (ppm) 14.1, 20.7, 30.0, and 54.1, corresponding to (E)-nbutyldiazoate. 9 The only other observed product was