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

Abstract

Facile ligand substitutions are observed when the neutral ruthenium cyclopropenyl complex (PPh 3)[Ru]–C C(Ph)CHCN ( 1, [Ru] = Tp(PPh 3)Ru) is treated with MeCN and pyrazole yielding the nitrile substituted ruthenium cyclopropenyl complex (MeCN)[Ru]–C C(Ph)CHCN ( 4a) and the ruthenium metallacyclic pyrazole complex (C 3H 3NN)[Ru]–C C(Ph)CH 2CN ( 7a), respectively. The reactions of Me 3SiN 3 with 1, 4a and 7a are investigated. Treatment of 1 with Me 3SiN 3 affords in high yield the cationic N-coordinated nitrile complex {(PPh 3)[Ru]NCCH(Ph)CH 2CN}N 3 ( 3). Interestingly, the reaction of 4a with Me 3SiN 3 in CH 2Cl 2 in the presence of NH 4PF 6 results in an insertion of four nitrogen atoms into the Ru–C α bond to form a diastereomeric mixture of the bright yellow zwitterionic tetrazolate complex (MeCN)[Ru]–N 4CCH(Ph)CH 2CN ( 6a) in a 3:2 ratio. The reaction of 7a with Me 3SiN 3 gives the zwitterionic tetrazolate complex (C 3H 3NNH)[Ru]–N 4CCH(Ph)CH 2CN ( 9a). The two cationic tetrazolate complexes {(C 3H 3NNH)[Ru]–N 4(R)CCH(Ph)CH 2CN} + ( 12a, R = CH 3, 12b, R = C 6H 5CH 2) 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.