Synthesis of Dirhodium(II) Complexes with Several Cyclometalated Thienylphosphines

Abstract

The thermal reaction of dirhodium tetraacetate with tris(3-thienyl)phosphine (3TP), diphenyl(3-thienyl)phosphine (3TPPh 2 ), and diphenyl(2-thienyl)phosphine (2TPPh 2 ) gives rise to mono-cyclometalated and bis-cyclometalated compounds; the latter can have a head-to-head (H-H) or head-to-tail (H-T) configuration. Bis-cyclometalated compounds with H-T configuration can be prepared in high yield under photochemical conditions or by combining irradiation with subsequent thermal treatment in acetic acid. The reactivity order of aromatic ring C-H activation is phenyl < 2-thienyl , 3-thienyl, which leads to a selective activation of the thienyl ring. Thus, only one mono-cyclometalated compound is obtained from the thermal reaction with 3TPPh 2 , and activation of the thienyl ring competes favorably with activation at the phenyl rings in the case of 2TPPh 2 . The reaction of these mono-cyclometalated compounds with d 4 -acetic acid was monitored by 1 H NMR spectroscopy, which demonstrates that the H/D exchange occurs during the demetalation step. The energy values calculated (DFT) for the different compounds agree with the experimental results.

Dirhodium(II) Compounds with Bridging Thienylphosphines: Studies on Reversible P,C/P,S Coordination

“…These chemical shifts are in the normal range for bridging, metalated thienylphosphines. [33,40] The intensity ratio between aliphatic and aromatic protons in these two compounds is consistent with the proposed stoichiometry. In addition, compound 2 a was structurally characterized by single-crystal X-ray methods.…”

“…[34][35][36][37][38] Thienylphosphines acting as P,S bridging ligands are even less common. [39][40][41] Remarkably, [35,36] the switching between P,S and P,C coordination mode of thienylphosphines in monometallic [RuA C H T U N G T R E N N U N G (bpy) 2 (pt)] complexes (bpy = bipyridine, pt = polythiophene phosphine) results in considerable changes on the electrochemical and spectroscopic properties of the complexes.…”

Chiral Dirhodium Catalysts: A New Era for Asymmetric Catalysis

“…Moreover, Estevan and co-workers [77,78] have reported the synthesis of new ortho-metalated dirhodium catalysts from the reaction of tri(2-thienyl)phosphine 167 [77], with dirhodium acetate in refluxing toluene for 1 hour. The single crystal X-ray crystal structure revealed that the thienyl ring for the bis-cyclometalated product is arranged in either a head-to-tail (H-T, 170) or a head-tohead (H-H, 168) configurations (Fig.…”

Thermal transformations of tris(2-thienyl)phosphine (PTh3) at low-valent ruthenium cluster centers: Part I. Carbon–hydrogen, carbon–phosphorus and carbon–sulfur bond activation yielding Ru3(CO)8L{μ-Th2P(C4H2S)}(μ-H) (L = CO, PTh3), Ru3(CO)7(μ-PTh2)2(μ3-η2-C4H2S), Ru4(CO)9(μ-CO)2(μ4-η2-C4H2S)(μ4-PTh) and Ru5(CO)11(μ-PTh2)(μ4-η4-C4H3)(μ4-S)

“…1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 Among the many functionalized phosphine ligands, the chemistry of phosphine ligands bearing thienyl (Th), 16,17,18,19,20,21,22,23,24,25 furyl (Fu), 26,27,28,29,30 and pyrrolyl (Pyr) 31,32,33 substituents are among the most widely investigated. In reactions with transition metal carbonyl complexes, these heterofunctional ligands often behave in a fashion similar to triphenylphosphine, readily acting as two-electron donor ligands.…”