Facile Direct Insertion of Nitrosonium Ion (NO⁺) into a Ruthenium−Aryl Bond

Abstract

T he discovery that nitric oxide plays many fundamental physiological roles has aroused interest in the structures, electronic properties, and reactivities of metal-nitrosyl complexes. [1][2][3][4][5][6][7][8][9][10][11][12][13] The chemistry between NO and organometallic complexes, especially reactions that lead to formation of new carbonnitrogen bonds, is of considerable interest because organic nitroso compounds have been demonstrated to be a class of attractive electrophiles in many carbon-nitrogen and/or carbon-oxygen bond forming reactions. 14-20 In the past few decades, investigations on the insertion of NO into metal-alkyl and metal-aryl bonds to form C-nitroso complexes provided insightful results for the development of metal-mediated organic transformation reactions, 21-36 and the alkyl/aryl moiety migration to the coordinated NO ligand, i.e. R-M-(NO) þ L f L-M-N(dO)R, has been demonstrated to be a critical step in carbon-nitrogen bond formation. Nitrosonium ion (NO þ ), a close relative of NO, is known to react substitutionally with metal complexes to give metal-nitrosyl systems, 8,37-44 although there are several examples proposing that NO þ can insert into metal-carbon bonds in an intermolecular fashion. [25][26][27]31 We herein present a systematic investigation of the reaction between NO þ and 2-phenylpyridine anion (phpy)-ligated cyclometalated ruthenium(II) complexes, which demonstrates for the first time that NO þ inserts into a Ru II -aryl phpy bond to give 2-(2-nitrosophenyl)pyridine (NO-phpy)-coordinated complexes. Experimental evidence supports a direct bimolecular NO þ insertion mechanism, i.e. M-R þ NO þ f [M-N(dO)-R] þ , but not an intramolecular migratory insertion mechanism for the insertion reactions in this work. Moreover, theoretical calculations reveal that direct NO þ insertion into the Ru-C bond may be rationalized as a frontier orbital interaction between the [Ru-aryl]-based HOMO of the Ru(II) complexes and the LUMO of the NO þ . Unlike many literature examples, the non-NO-ligated complexes [Ru(phpy)([9]aneS3)(L)] þ ([9]aneS3 = 1,4,7-trithiacyclononane) were employed to react with NO þ in this study; this can reduce ambiguity in mechanism evaluations. When excess [NO][BF 4 ] (5-fold) was added to [Ru(phpy)([9]aneS3)(solv)] þ (1-solv; solv = CH 3 CN, EtOH) in CH 3 CN under argon at room temperature, the solution changed from yellow to dark red immediately. The dark red product isolated (85% yield) was found to be [Ru(NO-phpy)-([9]aneS3)(CH 3 CN)] 2þ (2-CH 3 CN; NO-phpy = 2-(2-nitrosophenyl)pyridine) by 1 H and 13 C NMR spectroscopy, X-ray crystallography, and elemental analysis (Scheme 1). This reactivity is different from that for other ruthenium(II) complexes which react with NO þ substitutionally to give the ligand-substituted Runitrosyl products. 37,38,40,41,43 Reaction between the S-bound dmso complex [Ru(phpy)([9]aneS3)(dmso)] þ (1-dmso) and [NO]-[BF 4 ] in CH 3 CN also gave 2-CH 3 CN in 80% yield.The X-ray crystal structure for [2-CH 3 CN](PF 6 ) 2 3 CH 3 CN represents the...

A Ruthenium(II) Complex Supported by Trithiacyclononane and Aromatic Diimine Ligand as Luminescent Switch-On Probe for Biomolecule Detection and Protein Staining

“…Excitation of 1 ′ (31 μM) at 450 nm in acetonitrile resulted in an emission with λ max at 692 nm, a quantum yield of 2.334 × 10 −3 , and a lifetime of 0.272 μs. This emission was assigned as the triplet d π (Ru II ) → π*(N ∧ N) charge-transfer in nature based on comparison with analogous complexes reported previously 7 37 38 39 40 41 42 43 44 45 46 47 . The replacement of the bpy ligand with dcmb has been previously reported to red-shift the emission maximum of ruthenium(II) complexes 48 .…”

Influence of nitrosyl coordination on the binding mode of quinaldate in selective ruthenium frameworks. Electronic structure and reactivity aspects

“…The complexes with Enemark-Feltham notation 13 of {Ru(NO)} 6 in [Ru II (trpy)(L)(NO + )Cl](BF 4 ), [1]BF 4 , and [Ru II (trpy)(L) (NO + )](BF 4 ) 2 , [2](BF 4 ) 2 , have been synthesized via the direct reaction of NOBF 4 with the previously structurally characterized precursor complex [Ru II (trpy)(L)Cl] (A) 14 and the reaction of NOBF 4 with the in situ generated [Ru II (trpy)(L)(C 2 H 5 OH)] + , respectively, as shown in Scheme 1 (trpy = 2,29:69,299-terpyridine, L 2 = deprotonated form of unsymmetrical quinaldic acid, HL). 15,16 [1]BF 4 and [2](BF 4 ) 2 exhibit satisfactory microanalytical and mass spectral data (Fig. S1{) and show 1 : 1 and 1 : 2 molar conductivities in acetonitrile solution, respectively (see Experimental Section).…”

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

“…The chemical properties of nitrosoarene transition-metal complexes have also been a fascinating topic in connection with their π-conjugated systems . Several nitrosations with NO ligands on transition-metal complexes through direct C–N bond formation have been described, but among them are only a few couplings with arenes: the reaction of [Cp 2 Zr(Ph) 2 ] with NO, the reaction of [CpCr(NO) 2 (Ph)] with NOPF 6 , thermolysis of [Cp*W(NO)(Ph) 2 ], and direct NO + insertion of cyclometalated [Ru(ĈN)([9]aneS 3 )(L)] + (C^N = deprotonated phenylpyridine; [9]aneS 3 = 1,4,7-trithiacyclononane; L = solvent, t BuNC) and [Ru(C^N)([14]aneS 4 )] + ([14]aneS 4 = 1,4,8,11-tetrathiacyclotetradecane) . We recently reported two types of interesting nitrosation reactions (Scheme ).…”