Ortho−Nitrosation of Anilines on a Ruthenium Hydridotris(pyrazolyl)borato Complex and Oxidation of the Resulting Coordinated Amine Groups

Abstract

Nitrosation of anilines at the ortho position was found to proceed on a ruthenium hydridotris(pyrazolyl)borato (Tp) complex. Reactions of [TpRuCl2(NO)] (1) with primary anilines 4-NH2C6H4R (R = tBu, H) in the presence of excess Et3N in CH2Cl2 gave amine-chelated nitrosoarene complexes [TpRuCl{N(O)–C6H3R–NH2-κ2 N,N}] (R = tBu (2a), H (2b)). Use of 2,4,6-trimethylaniline afforded an aryldiazenido complex [TpRuCl2{NNC6H2(Me)3}] (3) without forming the nitrosation product because of the introduction of the Me substituents at the ortho positions. On the other hand, in the case of secondary amines (N-methylanilines 4-NH(Me)C6H4R (R = tBu, H)), similar reactions gave amine-chelated nitroso complexes [TpRuCl{N(O)–C6H3R–NHMe-κ2 N,N}] (R = tBu (4a), H (4b)) and imine-chelated nitroso complexes [TpRuCl{N(O)–C6H3R–NCH2-κ2 N,N}] (R = tBu (5a), H (5b)). Conversion of 4b into 5b by O2 was disclosed by 1H NMR monitoring. Moreover, oxidative reaction of 2a afforded an amide-chelated nitroso complex [TpRuCl{N(O)–C6H3(tBu)–NH-κ2 N,N}] (6a) through one-proton release from the NH2 group.

Ruthenium Derivatives of in Situ Generated Redox-Active 1,2-Dinitrosobenzene and 2-Nitrosoanilido. Diverse Structural and Electronic Forms

“…The evaluation of bond parameters of mono-anionic L′ – in 2 + (Scheme ) with those in reported analogous [T p Ru II Cl­{N­(O)­C 5 H 3 - t Bu-NH-κ 2 -N,N}, T p = hydridotris­(pyrazolyl) borate)], reveals the delocalization of negative charge over the HN–C–C–N­(O) centers.…”

“…Under identical experimental set up, L′ derived tc - 2 + displays reversible one oxidation (O1) and three successive reductions (R1–R3; Figure , Table ), where oxidation and reduction processes are appreciably positive- and negative-shifted, respectively, as compared to the corresponding tc - 1 + , leading to a huge difference in K c1 (O1/R1) value of 10 ( 2 + ) versus 10 ( 1 + ).…”

“…The strong π-acceptor feature of pap might have played a key role in facilitating the reduction of one of the NO groups of L in 1 + to L′ – in 2 + in the presence of protonated solvent. Note that only two reports of metal-coordinated L′ – with Ni­(II), Cu­(II), Pd­(II), Hg­(II), Fe­(II), and Ru­(II) ([T p RuCl­{N­(O)­C 5 H 3 - t Bu-NH-κ 2 -N,N}, T p = hydridotris­(pyrazolyl)­borate)]) are available, but its redox feature has not been addressed so far.…”

Ring Nitrogenation of Aromatic Amines by the Excited State of an Osmium(VI) Nitrido Complex

“…The Os1–N4 (1.796(6) Å) and N4–N5 (1.189(7) Å) bond distances indicate Os  N and NN character, consistent with significant electron delocalization in the Os–N–N moiety. These bond distances, as well as the Os1–N4–N5 (175.0(6)°) and N4–N5–C4 (136.1(7)°) bond angles, are comparable to those of the aryldiazenido Ru complexes, [RuCl 3 ( p -N 2 C 6 H 4 Me)­(PPh 3 ) 2 ] (1.796(9) and 1.144(10) Å and 171.2(9)° and 135.9(11)°), and [TpRuCl 2 {NNC 6 H 2 (Me) 3 }] (1.7991(14) and 1.163(2), 166.41(16)° and 141.4(2)°) …”

“…The IR spectrum of the diazonium complex 1 shows characteristic v(N�N) stretches at 1848 and 1831 cm −1 , and v(C�N) stretches at 2131 and 2121 cm −1 . 10b, 17,18 The IR spectrum of (PPh 4 )2 shows v(N−H) stretch at 3230 cm −1 , v(C�N) stretches at 2114 and 2089 cm −1 , and v(C�N) stretches at 1602 cm −1 . Similar v(C�N) and v(C�N) stretches are also found in 3, 4, and 5 (see the Experimental Section).…”