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]-N3 (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) have been investigated. The metal-bound heterocyclic complexes produced are triazolates [Ru]N3C2(CO2Me)2 (2) and [Ru]N3C2HCO2Me (3) from dimethyl acetylene dicarboxylate and methyl propiolate, respectively. Reaction of 1 with fumaronitrile in CH2Cl2 at room temperature results in removal of a HCN molecule and produces the triazolato complex [Ru]N3C2HCN (4). In contrast, reaction of tetracyanoethene with 1 affords the tetrazolato complex [Ru]N4C[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 N3(R)C2(CO2Me)2 (6a, R = CH2C6F5; 6b, R = CH2Ph; 6c, R = CH2CO2Me). 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]N3(CHCHCO2Me)C2H(CO2) (7) in a ratio of ca. 4:1. Reaction of (Z)-7 with ICH3 affords {[Ru]N3(CHCHCO2Me)C2H(CO2Me)}[I] (8a) and the following cleavage of the Ru−N bond gives [Ru]-I and an organic triazole, N3(CHCHCO2Me)C2H(CO2Me) (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.