Synthesis of Ruthenium Triazolato and Tetrazolato Complexes by 1,3-Dipolar Cycloadditions of Ruthenium Azido Complex with Alkynes and Alkenes and Regiospecific Alkylation of Triazolates

Abstract

The [3+2] cycloaddition reactions of alkynes and alkenes with ruthenium azido complex [Ru]-N 3 ( 1, [Ru] = ( η 5 -C 5 H 5 )(dppe)Ru, dppe = Ph 2 PCH 2 CH 2 PPh 2 ) have been investigated. The metal-bound heterocyclic complexes produced are triazolates [Ru]N 3 C 2 (CO 2 Me) 2 ( 2 ) and [Ru]N 3 C 2 HCO 2 Me ( 3 ) from dimethyl acetylene dicarboxylate and methyl propiolate, respectively. Reaction of 1 with fumaronitrile in CH 2 Cl 2 at room temperature results in removal of a HCN molecule and produces the triazolato complex [Ru]N 3 C 2 HCN ( 4 ). In contrast, reaction of tetracyanoethene with 1 affords the tetrazolato complex [Ru]N 4 C[C(CN) C(CN) 2 ] ( 5 ). The structures of these complexes are all clearly established as N(2)-bound. Alkylation of 2 with organic bromides causes cleavage of the Ru−N bond and affords [Ru]-Br and N (1)-alkylated five-membered-ring organic triazoles N 3 (R)C 2 (CO 2 Me) 2 ( 6a, R = CH 2 C 6 F 5; 6b, R = CH 2 Ph; 6c, R = CH 2 CO 2 Me). Reaction of 3 with excess methyl propiolate gives a mixture of Z - and E -form zwitterionic N (1)-bound N (3)-alkylated-4-substituted triazolato complexes [Ru]N 3 (CH CHCO 2 Me)C 2 H(CO 2 ) ( 7 ) in a ratio of ca. 4:1. Reaction of ( Z )- 7 with ICH 3 affords {[Ru]N 3 (CH CHCO 2 Me)C 2 H(CO 2 Me)}[I] ( 8a ) and the following cleavage of the Ru−N bond gives [Ru]-I and an organic triazole, N 3 (CH CHCO 2 Me)C 2 H(CO 2 Me) ( 9a ). A regiospecific alkylation happens by treatment of 3 with organic halides and gives a series of cationic N (1)-bound N (3)-alkylated-4-substituted triazolato complexes exclusively with high yields. The structures of 2, 3, 4, 5, ( Z )- 7, and 10a have been determined by single-crystal X-ray diffraction analysis.