The 1,3-dipolar cycloaddition reaction of cis-[Co(N_(3))_(2)(en)_(2)]NO_(3)1 with different organonitriles(NCR)under focussed microwave irradiation produced bis-tetrazolate complexes[Co(N_(4)CR)_(2)(en)_(2)](NO_(3)).I...The 1,3-dipolar cycloaddition reaction of cis-[Co(N_(3))_(2)(en)_(2)]NO_(3)1 with different organonitriles(NCR)under focussed microwave irradiation produced bis-tetrazolate complexes[Co(N_(4)CR)_(2)(en)_(2)](NO_(3)).Interestingly,in the case of 3-cyano pyridine the reaction produced both cis-and trans-isomers(cis-2 and trans-2),whereas for 4-cyano pyridine the compound obtained was exclusively cis(cis-3)and for 4-bromobenzonitrile it was only the trans-(trans-4)compound which was isolated.This indicates a probable role of remote substitution of the phenyl ring in dictating the formation of the preferential isomer.When starting from the trans-isomer of the diazido complex(trans-[Co(N_(3))_(2)(en)_(2)]ClO_(4),1a),upon reacting with different nitriles a mixture of cis-and trans-isomers of[Co(N_(4)CR)_(2)(en)_(2)]ClO_(4)was produced in each case,with a greater preference towards cis-geometry[R=4-NC_(5)H_(4)(cis-5 and trans-5),4-BrC_(6)H_(4)(cis-6 and trans-6)and C_(6)H_(5)(cis-7 and trans-7)].The preferential formation of the cis-analogue of compound trans-4 when starting from the trans-precursor was quite curious.A theoretical investigation of compounds trans-4 and cis-6 reveals that the greater stability of the trans-complex 4 may arise from additional van der Waals interactions in the solid state because of the presence of an extra DMF molecule as solvent of crystallization.However,an interacting counter-anion and a probable halogen–halogen interaction may also contribute to the formation of preferential isomers for cycloaddition complexes,even in the solution state.展开更多
文摘The 1,3-dipolar cycloaddition reaction of cis-[Co(N_(3))_(2)(en)_(2)]NO_(3)1 with different organonitriles(NCR)under focussed microwave irradiation produced bis-tetrazolate complexes[Co(N_(4)CR)_(2)(en)_(2)](NO_(3)).Interestingly,in the case of 3-cyano pyridine the reaction produced both cis-and trans-isomers(cis-2 and trans-2),whereas for 4-cyano pyridine the compound obtained was exclusively cis(cis-3)and for 4-bromobenzonitrile it was only the trans-(trans-4)compound which was isolated.This indicates a probable role of remote substitution of the phenyl ring in dictating the formation of the preferential isomer.When starting from the trans-isomer of the diazido complex(trans-[Co(N_(3))_(2)(en)_(2)]ClO_(4),1a),upon reacting with different nitriles a mixture of cis-and trans-isomers of[Co(N_(4)CR)_(2)(en)_(2)]ClO_(4)was produced in each case,with a greater preference towards cis-geometry[R=4-NC_(5)H_(4)(cis-5 and trans-5),4-BrC_(6)H_(4)(cis-6 and trans-6)and C_(6)H_(5)(cis-7 and trans-7)].The preferential formation of the cis-analogue of compound trans-4 when starting from the trans-precursor was quite curious.A theoretical investigation of compounds trans-4 and cis-6 reveals that the greater stability of the trans-complex 4 may arise from additional van der Waals interactions in the solid state because of the presence of an extra DMF molecule as solvent of crystallization.However,an interacting counter-anion and a probable halogen–halogen interaction may also contribute to the formation of preferential isomers for cycloaddition complexes,even in the solution state.
