Terminal Imido Rhodium Complexes

Abstract

Compounds of the late transition metals with M=X multiple bonds (X=CR2, NR, O) represent a synthetic challenge, partly overcome by preparative chemists, but with noticeable gaps in the second- and third-row elements. For example, there are no isolated examples of terminal imido rhodium complexes known to date. Described herein is the isolation, characterization, and some preliminary reactivity studies of the first rhodium complexes [Rh(PhBP3)(NR)] (PhBP3=PhB{CH2PPh2}3) with a multiple and terminal Rh=N bond. These imido compounds result from reactions of organic azides with the corresponding rhodium(I) complex having a labile ligand, and display a pseudo-tetrahedral core geometry with an almost linear Rh-N-C arrangement [177.5(2)°] and a short Rh-N bond [1.780(2) Å]. We also show that the Rh=N bond undergoes protonation at the nitrogen atom or addition of H2 , and also engages in nitrene-group transfer and cycloaddition reactions.

Beyond Triphos – New hinges for a classical chelating ligand

“…As these complexes have been studied as hydrogenation and hydrogen transfer catalysts, several complexes feature Rh-H fragments (67, 68, 72 and 74). Imido complexes A c c e p t e d M a n u s c r i p t Edited April 3 9 similar to the cobalt-and iron-complexes previously discussed have been synthesized, and all show identical reactivity with CO, forming their respective dicarbonyl complexes [M(CO) 2 (κ 3 -PhBP 3 R )] [35]. Rhodium-imido complexes were additionally reacted with (i) azides to give a tetrazene (75), (ii) acids to give tris solvent ligated complexes (76), and (iii) molecular hydrogen to afford dihydride species (74).…”

“…More recent work has focused on second row transition metals such as rhodium [31,32] and ruthenium [32,33]. Rhodium derivatives have displayed a wide range of chemistry, with many reported complexes (64-76, Scheme 12) [32,34,35]. As these complexes have been studied as hydrogenation and hydrogen transfer catalysts, several complexes feature Rh-H fragments (67, 68, 72 and 74).…”

“…It is interesting to note that when considering the activation of silanes on iridium, 10 can behave as a source of "[PhBP]Ir" or "[PhBP]IrH 2 " depending on the reaction conditions. M a n u s c r i p t Cobalt-, iron-and rhodium-imide complexes described in Section 2.1 exhibit similar reactivity towards CO and H 2 , producing isocyanate and primary amines, respectively (Scheme 26) [25,26,28,35]. The fate of the metal fragment was identical for each metal upon exposure to excess CO; namely, the formation of dicarbonyl complexes (73, 168 and 169, Scheme 26) via a reductive two-electron group-transfer process that delivers the bound imido group to the substrate.…”

“…Conversely, upon exposure to molecular hydrogen, the metallic components behaved differently. In both cases, the imido group is converted into a primary amine, but in the case of rhodium complexes, dihydride species are formed with the in situ generated amine remaining coordinated (74) [35]. On the other hand the iron complex released the generated amine and activate the benzene solvent by protonation (170, Scheme 26) [26].…”

Redox Non‐Innocent Behavior of a Terminal Iridium Hydrazido(2−) Triple Bond

“…Then, the resulting 1,1-isodiazene can be displaced by CO, forming Cp*Ir(CO) 2 and the free nitrene, which decomposes in solution. In comparison, Cp*IrN t Bu and other related imido complexes react with CO to form η 2 -bound organoisocyanates, [11] Thus, unlike normal terminal imidos, the nitrogen ligand of 6 undergoes CO-induced tautomerization rather than reacting directly with CO. Reactions of 6 with other L donors such as PMe 3 or outer-sphere oxidants such as [Fc]+[PF 6 ]-also produce product mixtures from diazene decomposition, and traces of the analogous reduced product Cp*Ir(PMe 3 ) 2 were detectable by NMR.…”