3-Rhoda-1,2-diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene.

Rh-containing metallacycles, [(TPA)Rh^III(κ²-( C, N)-CH₂CH₂(NR)₂-]Cl; TPA= N, N, N,N-tris(2-pyridylmethyl)amine have been accessed through treatment of the Rh^I ethylene complex, [(TPA)Rh(η² -CH₂CH₂)]Cl ([ 1]Cl) with substituted diazenes. We show this methodology to be tolerant of electron-deficient azo compounds including azo diesters (RCO₂NNCO₂R; R=Et [ 3]Cl, R= iPr [ 4]Cl, R= tBu [ 5]Cl, and R=Bn [ 6]Cl) and a cyclic azo diamide: 4-phenyl-1,2,4-triazole-3,5-dione (PTAD), [ 7]Cl. The latter complex features two ortho-fused ring systems and constitutes the first 3-rhoda-1,2-diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N-N coordination followed by insertion of ethylene into a [Rh]N bond. In terms of reactivity, [ 3]Cl and [ 4]Cl successfully undergo ring-opening using p-toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh^III(Cl)(κ¹-( C)-CH₂CH₂(NCO₂R)(NHCO₂R)]OTs; [ 13]OTs and [ 14]OTs. Deprotection of [ 5]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end-on coordinated diazene [(TPA)Rh^III(κ²-( C,N)-CH₂CH₂(NH)₂-]⁺ [ 16]Cl, a hitherto unreported motif. Treatment of [ 16]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh^III(κ²-( C,N)-CH₂CH₂(NAc)₂-]⁺, [ 17]Cl. Treatment of [ 1]Cl with AcNNAc did not give the RhN insertion product, but instead the N,O-chelated complex [(TPA)Rh^I (κ²-( O,N)-CH₃(CO)(NH)(NC(CH₃)(OCHCH₂))]Cl [ 23]Cl, presumably through insertion of ethylene into a [Rh]O bond. [ABSTRACT FROM AUTHOR]