A series of thirty‐three N,N′‐diaryl, dialkyl, and alkyl‐aryl ureas have been prepared in pyridine or toluene by reaction of silylamines with CO2. This protocol is shown to provide facile access to 13C‐labeled ureas, as well as chiral and macrocyclic ureas. These reactions proceed through initial generation of the corresponding silylcarbamates, which subsequently react with silylamine under thermal conditions to afford the thermodynamically favored urea and disilyl ether.

A series of thirty‐three N,N′‐diaryl, dialkyl, and alkyl‐aryl ureas have been prepared in pyridine or toluene by reaction of silylamines with CO2. This protocol is shown to provide facile access to 13C‐labeled ureas, as well as chiral and macrocyclic ureas. These reactions proceed through initial generation of the corresponding silylcarbamates, which subsequently react with silylamine under thermal conditions to afford the thermodynamically favored urea and disilyl ether.

The synthesis and use of the first examples of unsymmetrical, mixed phosphine donor tripodal NPP 2 ′ ligands N-(CH 2 CH 2 PR 2 ) 2 (CH 2 CH 2 PPh 2 ) are presented. The ligands are synthesized via a convenient, one pot reductive amination using 2-(diphenylphosphino)ethylamine and various substituted phosphonium dimers in order to introduce mixed phosphine donors substituted with P/ P′, those being Ph/Cy (2), Ph/ i Pr (3), Ph/ i Bu (4), Ph/o-Tol (5), and Ph/p-Tol (6). Additionally, we have developed the first known synthesis of a symmetrical tripodal NP 3 ligand N(CH 2 CH 2 PiBu 2 ) 3 using bench safe ammonium acetate as the lone nitrogen source (7). This new protocol eliminates the use of extremely dangerous nitrogen mustard reagents typically required to synthesize NP 3 ligands. Some of these tetradentate ligands and also P 2 NN′ ligands N(CH 2 -o-C 5 H 4 N)(CH 2 CH 2 PR 2 ) 2 (P 2 NN′-Cy, R = Cy; P 2 NN′-Ph, R = Ph) prepared by reductive amination using 2-picolylamine are used in the synthesis and reactions of iron complexes. FeCl 2 (P 2 NN′-Cy) (8) undergoes single halide abstraction with NaBPh 4 to give the trigonal bipyramidal complex [FeCl(P 2 NN′-Cy)][BPh 4 ] (9). Upon exposure to CO(g), complex 9 readily coordinates CO giving [FeCl(P 2 NN′-Cy)(CO)][BPh 4 ] (10), and further treatment with an excess of NaBH 4 results in formation of the hydride complex [Fe(H)(P 2 NN′-Cy)(CO)][BPh 4 ] (11). Our previously reported complex FeCl 2 (P 2 NN′-Ph) undergoes double halide abstraction with NaBPh 4 in the presence of the coordinating solvent to give [Fe(NCMe) 2 (P 2 NN′-Ph)][BPh 4 ] 2 (12). Ligand 3 can be coordinated to FeCl 2 , and upon sequential halide abstraction, treatment with NaBH 4 , and exposure to an atmosphere of dinitrogen, the dinitrogen hydride complex [Fe(H)(NPP 2 ′-i Pr)(N 2 )][BPh 4 ] (13) is isolated. Our symmetrical NP 3 ligand 7 can also be coordinated to FeCl 2 and, upon exposure to an atmosphere of CO(g), selectively forms [FeCl(NP 3 )(CO)][BPh 4 ] (14) after salt metathesis with NaBPh 4 . Complex 14 can be treated with an excess of NaBH 4 to give the hydride complex [Fe(H)(NP 3 )(CO)][BPh 4 ] (15), which can further be deprotonated/reduced to the Fe(0) complex Fe(NP 3 )(CO) (16) upon treatment with an excess of KH.