Azavinylidene Complexes from Coupling Reactions of Organonitriles with Phosphines

Abstract

The reactions of the rhenium(III)-phosphine complex ReCl 3 (PMePh 2 ) 3 with organonitriles (NCR) were studied and found to give novel addition as well as simple substitution products. Refluxing ReCl 3 (PMePh 2 ) 3 in acetonitrile (MeCN) yielded a mixture of the organonitrile rhenium complex ReCl 3 (PMePh 2 ) 2 (NCMe) and the rhenium phosphonium-substituted azavinylidene complex ReCl 3 (PMePh 2 ) 2 {NC(PMePh 2 )-Me}. Similarly, reactions of ReCl 3 (PMePh 2 ) 3 with arylnitriles p-R-C 6 H 4 CN (R = H, Me, and Br) gave the corresponding azavinylidene complexes ReCl 3 (PMePh 2 ) 2 {N C(PMePh 2 )(p-C 6 H 4 R)}. The nitrile complex ReCl 3 (PPh 3 ) 2 (NCPh) is unreactive toward external PPh 3 , but it reacts with excess PMe 3 to produce the azavinylidene complex ReCl 3 (PMe 3 ) 2 {NC(PMe 3 )Ph}. Computational studies reveal the effect of ligand and substituent of organonitriles on the thermodynamics and kinetics for the reactions of ReCl 3 (PR 3 ) 2 (NCR′) with PR 3. Both the experimental and computational results indicate that nucleophilic addition of phosphines to coordinated nitriles is more favorable for nitriles with an electron-withdrawing group and for phosphines which are more electron-donating.

Synthesis, structure and aromaticity of metallapyridinium complexes

“…Phosphonium-substituted rhenium azavinylidene complexes can be directly produced from the coupling reactions of nitriles with phosphines. 7 DFT studies on aromaticity Density functional theory (DFT) studies 8 were performed on the model complex M-N (Table 1) to examine the aromaticity of complex 2, in which PMePh 2 was replaced by PH 3 to reduce the calculation cost. Nucleus-independent chemical shift (NICS) 9 calculations were carried out.…”

“…Hydrogen atoms on the phenyl and methyl groups were omitted for clarity. Selected bond lengths [Å] and angles [°]: Re1-C4 1.9013(18), Re1-C5 2.1975(18), Re1-N1 2.0525(17), C1-N1 1.295(3), C1-C2 1.434(3), C2-C3 1.418(3), C3-C4 1.423(3), C4-C5 1.425(3), Re1-Cl1 2.4733(5), Re1-Cl2 2.4311(5), Re1-Cl3 2.4570(5), Re1-P2 2.4053(5), C5-P1 1.7874(18), C1-Cl4 1.7342(19), C4-Re1-C5 39.87(7), Re1-C4-C5 81.33(11), Re1-C4-C3 140.88(14), C2-C3-C4 119.94(17), C1-C2-C3 117.72(17), N1-C1-C2 124.13(18), Re1-N1-C1 137.27(14), and C4-Re1-N1 78.12(7).…”

“…Hydrogen atoms on the phenyl and methyl groups were omitted for clarity. Selected bond lengths [Å] and angles [°]: Re1-C1 2.190(5), Re1-C2 1.876(5), Re1-N1 1.996(4), N1-C5 1.331(6), C4-C5 1.439(6), C3-C4 1.414(7), C2-C3 1.441(6), C1-C2 1.424(6), Re1-Cl1 2.4873(13), Re1-Cl2 2.4553(12), Re1-Cl3 2.4010(13), Re1-P2 2.4222(14), C5-P1 1.819(5), C1-P3 1.783(5), C1-Re1-C2 40.06(18), Re1-C2-C1 81.9(3), Re1-C2-C3 141.6(4), C2-C3-C4 118.4(4), C3-C4-C5 118.7(4), N1-C5-C4 122.6(5), Re1-N1-C5 138.3(4), C2-Re1-N1 78.84(19), and N1-C5-P1 116.8(4).…”

A Comprehensive Analysis of the Metal–Nitrile Bonding in an Organo-Diiron System

“…The cations are based on a diiron core comprising the Cp ligands in cis position, bridging aminocarbyne and CO ligands, and terminal CO and nitrile ligands. The C(3)–N(1) interaction [1.288(7)–1.297(4) Å] displays some double-bond character, as typically found in analogous complexes [ 19 , 20 , 21 , 26 , 27 , 57 , 58 ], highlighting the hybrid aminocarbyne/iminium nature of the {µ-CN(Me)(Y)} ligand ( Scheme 4 ). In all structures, the nitrile ligand is on the same side with respect to the bulkier aminocarbyne substituent Y (Z isomer).…”

“…They most commonly behave as monodentate ( end-on ) ligands, and have been widely employed as weakly coordinating agents in complexes of low- to middle-valent transition metals, since their substitution by more strongly coordinating ligands is a convenient strategy to access a multitude of derivatives, catalysts and materials [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Furthermore, nitrile ligands are usually susceptible to nucleophilic attack [ 12 , 13 , 14 ] and may be engaged in a great variety of chemical transformations mediated by the adjacent metal centre, either catalytic [ 15 , 16 , 17 , 18 ] or stoichiometric [ 12 , 19 , 20 , 21 , 22 , 23 ].…”