Matthias Mastalir

Divergent Coupling of Alcohols and Amines Catalyzed by Isoelectronic Hydride Mn(I) and Fe(II) PNP Pincer Complexes.

Herein, we describe an efficient coupling of alcohols and amines catalyzed by well-defined isoelectronic hydride Mn(I) and Fe(II) complexes, which are stabilized by a PNP ligand based on the 2,6-diaminopyridine scaffold. This reaction is an environmentally benign process implementing inexpensive, earth-abundant non-precious metal catalysts, and is based on the acceptorless alcohol dehydrogenation concept. A range of alcohols and amines including both aromatic and aliphatic substrates were efficiently converted in good to excellent isolated yields. Although in the case of Mn selectively imines were obtained, with Fe-exclusively monoalkylated amines were formed. These reactions proceed under base-free conditions and required the addition of molecular sieves.

Manganese-Catalyzed Aminomethylation of Aromatic Compounds with Methanol as a Sustainable C1 Building Block

This study represents the first example of a manganese-catalyzed environmentally benign, practical three-component aminomethylation of activated aromatic compounds including naphtols, phenols, pyridines, indoles, carbazoles, and thiophenes in combination with amines and MeOH as a C1 source. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps which give rise to selective C-C and C-N bond formations, thereby releasing hydrogen and water. A well-defined hydride Mn(I) PNP pincer complex, recently developed in our laboratory, catalyzes this process in a very efficient way, and a total of 28 different aminomethylated products were synthesized and isolated yields of up to 91%. In a preliminary study, a related Fe(II) PNP pincer complex was shown to catalyze the methylation of 2-naphtol rather than its aminomethylation displaying again the divergent behavior of isoelectronic Mn(I) and Fe(II) PNP pincer systems.

Air-Stable Triazine-Based Ni(II) PNP Pincer Complexes As Catalysts for the Suzuki–Miyaura Cross-Coupling

Air-stable, thermally robust, and well-defined cationic Ni(II) PNP pincer complexes based on the 2,4-diaminotriazine scaffold are described. These complexes are active catalysts for the Suzuki-Miyaura cross-coupling of a wide range of aryl, heteroaryl (including benzoxazole, thiazole, pyridine, pyrimidine, thiazole), primary and secondary alkyl halides, and pseudohalides with different organoboronate reagents giving excellent to good isolated yields. Neutral deprotonated complexes seem to play a key role in the catalytic process.

Three Different Reactions, One Catalyst: A Cu(I) PNP Pincer Complex as Catalyst for C–C and C–N Cross-Couplings

An air-stable, thermally robust, and well-defined Cu(I) PNP pincer complex based on the 2,6-diaminopyridine scaffold is described. This complex is an active catalyst for the cross-couplings of a range of aryl and heteroaryl (including benzoxazole, thiazole, pyridine, and thiophene) halides with different organomagnesium reagents, alkynes, and aryl-amines giving excellent to good isolated yields.

Iron PCP Pincer Complexes in Three Oxidation States: Reversible Ligand Protonation To Afford an Fe(0) Complex with an Agostic C–H Arene Bond

In the current investigation, the reaction of Fe2(CO)9 with the ligand precursor 2-chloro-N1,N3-bis(diisopropylphosphanyl)-N1,N3-diethylbenzene-1,3-diamine (P(C-Cl)PNEt- iPr) (1) was investigated. When a suspension of Fe2(CO)9 and 1 in CH3CN was transferred in a sealed microwave glass vial and stirred for 18 h at 110 °C the complex [Fe(PCPNEt- iPr)(CO)2Cl] (2) was obtained. In an attempt to prepare the hydride Fe(II) complex [Fe(PCPNEt- iPr)(CO)2H] (3), 2 was reacted with 1 equiv of Li[HBEt3] in THF. Instead of ligand substitution, this complex underwent a one electron reduction which led to the formation of the low-spin d7 Fe(I) complex [Fe(PCPNEt- iPr)(CO)2] (4). Exposure of a benzene solution of 4 to NO gas (1 bar) at room temperature affords the diamagnetic complex [Fe(PCPNEt- iPr)(CO)(NO)] (5). This is the first iron PCP nitrosyl complex. Protonation of 5 with HBF4·Et2O affords the cationic Fe(0) complex [Fe(κ3 P,CH,P-P(CH)PNEt- iPr)(CO)(NO)]BF4 (6) which features an η2-Caryl-H agostic bond. Even with relatively weak bases such as NEt3 the agostic C-H bond can be deprotonated with reformation of the starting material 5. Therefore, protonation of 5 is completely reversible.

Crystal structure of the tetra­hydro­furan disolvate of a 94:6 solid solution of [N2,N6-bis­(di-tert-butyl­phosphan­yl)pyridine-2,6-di­amine]­dibromido­manganese(II) and its monophosphine oxide analogue

The MnBr2 complex of N 2,N 6-bis(di-tert-butylphosphanyl)pyridine-2,6-diamine (1·MnBr2) co-crystallizes with 5.69% of the monophosphine oxide analogue (1O·MnBr2) and two tetrahydrofuran (THF) molecules, namely {N 2,N 6-bis(di-tert-butylphosphanyl)pyridine-2,6-diamine}dibromidomanganese(II)–[bis(di-tert-butylphosphanyl)({6-[(di-tert-butylphosphanyl)amino]pyridin-2-yl}amino)phosphine oxide]dibromidomanganese(II)–tetrahydrofuran (0.94/0.06/2), [MnBr2(C21H41N3P2)]0.94[MnBr2(C21H41N3OP2)]0.06·2C4H8O. The 1·MnBr2 and 1O·MnBr2 complexes are connected by weak N—H⋯Br hydrogen bonding into chains extending along [001] with the THF molecules located between the layers formed by these chains.

Crystal structure of 2,6-di­amino­pyridinium chloride

The crystal structure of the organic–inorganic hybrid title salt is held together by N—H⋯Cl hydrogen bonds.