Improved Syntheses for the Compounds [(1,5-COD)M(μ-O₂C₈H₁₅)]₂ (M = Ir, Rh)

Abstract

A recent paper 1 describes the synthesis and characterization of the compounds [(1,5-COD)M(μ-O 2 C 8 H 15 )] 2 (COD = cyclooctadiene, M = Ir (1), Rh (2), O 2 C 8 H 15 = 2-ethylhexanoate) as models of industrial Co and Ni Ziegler-type hydrogenation precatalysts. 1À3 For that work, it is important to have definitively characterized, high-purity precatalyst materials readily availablecharacterization of 1 and 2 previously included single-crystal X-ray crystallographic structure determinations (Figure 1). Additionally, it was noted therein 1 that both 1 and 2 have potential in other areas, 4 including film deposition on semiconductor devices, for which the synthesis and preliminary characterization of 1 was described previously. 5 In a broader sense, complexes 1 and 2 are valuable members of the class of alkanoate complexes of M(1,5-COD) + (M = Ir, Rh) typified by the classic acetate prototypes [(1,5-COD)Ir(μ-OAc)] 2 and [(1,5-COD)Rh(μ-OAc)] 2 . 6 Herein we report improved synthetic procedures for 1 and 2 and the resulting simplification in isolating 1 and 2 in pure crystalline form. In addition, the improved synthesis procedure has led to an improved yield of 1: 76% versus the 61% yield achieved via the previous synthetic approach. 1 The improved synthesis and simplified crystallization procedures are significant, not only because of the demonstrated usefulness of 1 as a model for study of the industrial Ziegler-type hydrogenation catalysts, 3 but also because of the potential usefulness of both 1 and 2 in other areas and in important industrial applications. 4,5

Unintuitive Inverse Dependence of the Apparent Turnover Frequency on Precatalyst Concentration: A Quantitative Explanation in the Case of Ziegler-Type Nanoparticle Catalysts Made from [(1,5-COD)Ir(μ-O2C8H15)]2 and AlEt3

“…The dark red precatalyst [(1,5-COD)Ir(μ-O 2 C 8 H 15 )] 2 was prepared as previously reported 41 and used as prepared once its purity had been verified by NMR. 41 Apparatus.…”

“…The dark red precatalyst [(1,5-COD)Ir(μ-O 2 C 8 H 15 )] 2 was prepared as previously reported 41 and used as prepared once its purity had been verified by NMR. 41 Apparatus. Catalytic hydrogenation was performed in an apparatus (that is detailed in our previous literature 42 ) composed of a hydrogen tank (Airgas HY300) with a pressure regulator (Airgas Y12-D244D) set to 40 psi connected to (i) a moisture trap (Trigon Technologies TTM400-4), (ii) an oxygen trap (Trigon Technologies TTO-100-4), (iii) an indicating oxygen trap (Trigon Technologies TTIO-150-4), (iv) a rotary-vane vacuum pump (Welch DirecTorr 8925, 1 × 10 −4 Torr ultimate pressure), (v) Swagelok quick-connects, (vi) a Fisher-Porter bottle (Andrews Glass 3 oz PRV), and (vii) a pressure transducer (Omega PX624) powered by an Omega PSS D15C 15 V power supply and interfaced to a PC via an RS232 interface provided by an Omegabus D1131 (A/D converter).…”