Amidate-Ligated Complexes of Rhodium(I): A Showcase of Coordination Flexibility

Abstract

Reaction of the amidate ligand salts Na[N(Dipp)C(O)R] (R = Ph (1a), tBu (1b); Dipp = 2,6-diisopropylphenyl) with [Rh(NBD)-Cl] 2 (NBD = norbornadiene) proceeds to give the dirhodium(I) complexes [Rh 2 {μ 2 -N,O-N(Dipp)C(O)R} 2 (NBD) 2 ] (R = Ph (2a), tBu (2b)) with variable coordination behavior. For complex 2b, a monomer− dimer equilibrium with the mononuclear complex [Rh{κ 2 -N,O-N(Dipp)-C(O)tBu}(NBD)] (3b) was established for the first time. Precursors 2a,b were treated with PPh 3 and PCy 3 , giving the distorted-square-planar κ 2 -N,O amidates [Rh{κ 2 -N,O-N(Dipp)C(O)R}(PPh 3 ) 2 ] (R = Ph (4a), tBu (4b)) or the κ 1 -O complexes [Rh{κ 1 -O-N(Dipp)C(O)R}(NBD)(PCy 3 )] (R = Ph (5a), tBu (5b)). Initial reactivity screening showed that complex 4b undergoes O 2 activation, providing Ph 3 PO; via the transient peroxo complex 6b, which was characterized in the solution phase. The κ 2 -N,O amidate coordination in 6b has been conclusively established by diagnostic 13 C{ 1 H} NMR spectroscopy.

Oxidation State Dependent Coordination Modes: Accessing an Amidate‐Supported Nickel(I) δ‐bis(C−H) Agostic Complex

“…Further analysis of the crystal structures of 3 and 4 reveals delocalization of charge through the O(1)‐C(28)‐N(1) π‐system as seen by the similar O(1)–C(28) [ 3 , 1.3098(17) Å; 4 , 1.321(2) Å] and N(1)–C(28) [ 3 , 1.3035(18) Å; 4 , 1.305(3) Å] bond lengths. This data is consistent with our reports of κ 2 ‐ N , O amidates bound to other TMs …”

“…The solution 13 C{ 1 H} NMR spectra of 3 and 4 show carbonyl shifts ( δ =187.6 and 186.5, respectively) characteristic of κ 2 ‐ N , O ‐amidate coordination . The κ 2 ‐ N , O assignment is corroborated in the solid state (Figure a,b), wherein the amidate N‐atom in both structures is oriented trans to the bulky IPr coligand; 3 [C(1)‐Ni(1)‐N(1) 167.89(5)°] and 4 [C(1)‐Ni(1)‐N(1) 171.04(8)°].…”

“…Recently, we have begun to explore the coordination chemistry of 1,3‐ N , O chelating ligands on late TMs . In particular, we have found that monoanionic LX‐type amidates [RNCOR′] − can be used to advantage in the formation of square planar Rh I complexes that can access a range of new amidate coordination modes . In addition, we disclosed an unsaturated Cp*Ir III phosphoramidate [RN(P=O)(OR) 2 ] − complex which promotes a range of E−H (E=H, B, C, Si) activation processes ,…”

Catalytic and co-ordination chemistry of enolate oxazoline K2-N,O-ligands to group 9 & 11 transition metals

“…The Ir-O bond lengths in 15 are slightly shorter than those reported in the literature (Table 12) although, other experimental bond lengths and angles for 15 are consistent with other Ir + -COD complexes in the literature. 55,80,83,84…”

“…Bond angles and Ir-O, Ir-N and Ir-C bond lengths are comparable to other Ir +3 -COD complexes ( Table 13). 55,80,83,84…”