Synthesis and reactivity of ruthenium tetrazolate complexes containing a tris(pyrazolyl)borato (Tp) ligand

Facile ligand substitutions are observed when the neutral ruthenium cyclopropenyl complex (PPh3)[Ru]–CC(Ph)CHCN (1, [Ru] = Tp(PPh3)Ru) is treated with MeCN and pyrazole yielding the nitrile substituted ruthenium cyclopropenyl complex (MeCN)[Ru]–CC(Ph)CHCN (4a) and the ruthenium metallacyclic pyrazole complex (C3H3NN)[Ru]–CC(Ph)CH2CN (7a), respectively. The reactions of Me3SiN3 with 1, 4a and 7a are investigated. Treatment of 1 with Me3SiN3 affords in high yield the cationic N-coordinated nitrile complex {(PPh3)[Ru]NCCH(Ph)CH2CN}N3 (3). Interestingly, the reaction of 4a with Me3SiN3 in CH2Cl2 in the presence of NH4PF6 results in an insertion of four nitrogen atoms into the Ru–Cα bond to form a diastereomeric mixture of the bright yellow zwitterionic tetrazolate complex (MeCN)[Ru]–N4CCH(Ph)CH2CN (6a) in a 3:2 ratio. The reaction of 7a with Me3SiN3 gives the zwitterionic tetrazolate complex (C3H3NNH)[Ru]–N4CCH(Ph)CH2CN (9a). The two cationic tetrazolate complexes {(C3H3NNH)[Ru]–N4(R)CCH(Ph)CH2CN}+ (12a, R = CH3, 12b, R = C6H5CH2) are prepared by electrophilic addition of organic halides to 9a. All of the complexes are identified by spectroscopic methods as well as elemental analysis. Pathways for the synthesis of these compounds are proposed.

Graphical abstractTreatment of the neutral ruthenium cyclopropenyl complex 1 with pyrazole afforded the ruthenium metallacyclic pyrazole complex 7a. The reaction of 7a with Me3SiN3 gives the zwitterionic tetrazolate complex 9a.Figure optionsDownload full-size imageDownload as PowerPoint slide