Synthesis of Heterobimetallic Complexes by Coordination of Rhodium(III) and Iridium(III) Poly-N,O-NHC Complexes to Silver(I), Copper(II), and Zinc(II)

Abstract

The reaction of [RhCl 2 (Cp*)] 2 with 2-trimethylsiloxyphenyl isocyanide (1) led to the mononuclear diisocyanide complex [RhCl(Cp*)(1) 2 ]. Cleavage of the Si− O bonds of the coordinated isocyanide ligands with a catalytic amount of KF and H 2 O gave the neutral rhodium(III) complex [RhCl(Cp*)(NH,O-NHC)(N,O-NHC)] ([2]) bearing a C2metalated N,O-benzoxazolinato ligand and an NH,O-benzoxazolin-2-ylidene ligand. In the presence of AgBF 4 the same reaction sequence with [MCl 2 (Cp*)] 2 (M = Rh, Ir) and 1 led to the removal of all halogeno ligands and formation of the complexes [M(Cp*)(NH,O-NHC)(N,O-NHC) 2 ] (M = Rh, [3]; M = Ir, [4]) bearing one C-metalated NH,O-NHC benzoxazolin-2-ylidene and two C-metalated N,O-benzoxazolinato ligands. Deprotonation of the remaining N−H function in complexes [3] and [4] generated complexes with three amido donor functions which act as tripodal metalloligands for the coordination to additional transition metals such as Ag I , Cu II , and Zn II , thus allowing the preparation of the polynuclear heterobimetallic complexes [5]−[10] bearing C/N-metalated benzoxazolinato ligands.

Mechanistic Studies of Styrene Production from Benzene and Ethylene Using [(η2-C2H4)2Rh(μ-OAc)]2 as Catalyst Precursor: Identification of a Bis-RhI Mono-CuII Complex As the Catalyst

“…The orientation of coordinated ethylene is perpendicular to the Rh coordination square plane, which is characteristic for d 8 Rh I (η 2 -C 2 H 4 ) complexes. , Similar to other reported Rh­(I) complexes with an ethylene ligand, , the CC bond of coordinated ethylene in 4 is only slightly longer (1.393(6) and 1.402(6) Å) than that of free ethylene (1.330 Å), suggesting substantial double bond character. The bond length of coordinated ethylene in 4 is slightly longer than that reported for 1 (1.35–1.40 Å) …”

“…The resulting crystal was characterized as the heterometallic complex 4 with bridging pivalate groups between the Rh I centers and Cu II (Figure ). Reported examples of structurally characterized trinuclear Rh 2 Cu complexes are rare. − The distance between Rh and Cu atoms (3.0095(5) Å) is longer than the sum of the covalent radii of rhodium (1.39 Å) and copper (1.27 Å) in cluster compounds and is longer than the typical range of Rh–Cu bond lengths (2.5–2.6 Å) in this class of Rh 2 Cu complexes. − Therefore, we believe little or no Rh–Cu bonding interaction is involved in 4 . The orientation of coordinated ethylene is perpendicular to the Rh coordination square plane, which is characteristic for d 8 Rh I (η 2 -C 2 H 4 ) complexes. , Similar to other reported Rh­(I) complexes with an ethylene ligand, , the CC bond of coordinated ethylene in 4 is only slightly longer (1.393(6) and 1.402(6) Å) than that of free ethylene (1.330 Å), suggesting substantial double bond character.…”

“…The bond length of coordinated ethylene in 4 is slightly longer than that reported for 1 (1.35−1.40 Å). 80 To ascertain if complex 4 persists in solution, further NMR studies were conducted. Diffusion ordered spectroscopy experiments were not possible due to rapid spin relaxation of the ethylene protons of 4 (see the Supporting Information).…”