Spin State, Structure, and Reactivity of Terminal Oxo and Dioxygen Complexes of the (PNP)Rh Moiety

Abstract

[Rh(III)H{(tBu(2)PCH(2)SiMe(2)NSiMe(2)CH(2)PtBu{CMe(2)CH(2)})}], ([RhH(PNP*)]), reacts with O(2) in the time taken to mix the reagents to form a 1:1 eta(2)-O(2) adduct, for which O--O bond length is discussed with reference to the reducing power of [RhH(PNP*)]; DFT calculations faithfully replicate the observed O-O distance, and are used to understand the oxidation state of this coordinated O(2). The reactivity of [Rh(O(2))(PNP)] towards H(2), CO, N(2), and O(2) is tested and compared to the associated DFT reaction energies. Three different reagents effect single oxygen atom transfer to [RhH(PNP*)]. The resulting [RhO(PNP)], characterized at and above -60 degrees C and by DFT calculations, is a ground-state triplet, is nonplanar, and reacts, above about +15 degrees C, with its own tBu C--H bond, to cleanly form a diamagnetic complex, [Rh(OH){N(SiMe(2)CH(2)PtBu(2))(SiMe(2)CH(2)PtBu{CMe(2)CH(2)})}].

Double Single‐Crystal‐to‐Single‐Crystal Transformation and Small‐Molecule Activation in Rhodium NHC Complexes

“…As expected based on our previous work,9a–c compound 6 is isolated as a square‐planar complex of dioxygen with an oxygen–oxygen bond that is shorter than the characteristic peroxo bond of ca. 1.45 Å, as previously observed 12b,d. 17…”

“…The rhodium–carbene bonds are nearly identical to structurally related rhodium bis(IPr) O 2 complexes 9c. As previously noted, the OO bond (O1O1A) of complex 6 is shorter than typical peroxo bonds12b,d, 19 at 1.392(11) Å, which is consistent with other examples of related complexes 9c. As the complex also has square‐planar geometry, it is likely that complex 6 is another example of Rh I singlet oxygen complexes.…”

Activation of small molecules by a rhodium bis(phosphinite) pincer complex

“…9 In attempting to isolate complex 6 by removing solvent or crystallization, complex 6 spontaneously decomposed to form a black powder and ligand oxidation products. However, the spectroscopic data in combination with the green color of 6 unequivocally point to the presence of the {Rh(O 2 )} fragment in complex 6.…”

Structure and Reactivity of Dinitrogen Rhodium Complexes Containing N‐Heterocyclic Carbene Ligands

“…[32][33][34] One other example of a low-valent rhodium complex of molecular nitrogen was reported by Caulton's group featuring a unique PNP ligand, [(tBu 2 PCH 2 SiMe 2 ) 2 N]Rh(N 2 ), which has a very low ν(N-N) of 2068 cm -1 . [35] Interestingly, the three-coordinate fragment of Caulton's complex [36] and the similar (PCP)-Rh complex, [Me 2 C 6 H(CH 2 PtBu 2 ) 2 ]Rh, reported by Milstein [37] coordinate oxygen to give Rh I -O 2 complexes similar to 1a and 1b with O-O bond lengths of 1.363 and 1.365 Å, respectively.…”