Heterobimetallic Indenyl Complexes. Kinetics and Mechanism of Substitution and Exchange Reactions of trans-[Cr(CO)₃-indenyl-Rh(CO)₂] with Olefins

Abstract

The trans coordination of the benzene ring of the indenyl-Rh(CO) 2 complex with tricarbonylchromium strongly enhances the rate of substitution of CO's with bidentate olefins, 1,5-cyclooctadiene (COD) and norbornadiene (NBD) ("extra-indenyl effect"). The activation parameters suggest an associative reaction pathway assumed to proceed via the intermediacy of a nonisolable low-hapticity species, η 1 -indenyl-Rh(CO) 2 (L 2 ). In addition, the rate of exchange of the Cr(CO) 3 group of the complexes trans-[Cr(CO) 3 -indenyl-Rh(CO) 2 ], 3, and trans-[Cr(CO) 3 -indenyl-Rh(COD)], 3a, and suitable acceptors (hexamethylbenzene and cycloheptatriene) is markedly increased with respect to that measured for the same reaction in the monometallic complex η-naphthalene-Cr(CO) 3 ("extra-naphthalene effect"). These mutual effects of the Cr(CO) 3 and RhL 2 units are transmitted through the 10 π electron indenyl framework, and the results obtained are in agreement with the existence of an haptomeric ground-state equilibrium between the two isomers trans-[Cr(CO) 3 -µ,η 6 :η 3 -indenyl-RhL 2 ], I, and trans-[Cr(CO) 3 -µ,η 4 :η 5 -indenyl-RhL 2 ], II.

Walking Metals in d8⋅⋅⋅d8 Hetero‐bimetallic Complexes: An Original Dynamic Phenomenon

“…[3][4][5] Strikingly, most studies have focused thus far on monometallic complexes, and, comparatively, metal-shift processes have only been rarely evidenced and studied in polymetallic complexes. [6] On the one hand, the unique properties associated with the presence of several metal centers make their dynamic behavior all the more interesting to be studied. But No evidence for a metal shift was observed in that case, even at high temperature, thus indicating that inplane pincer coordination to the Pd center plays a crucial role.…”

Synthesis and structure of mono- and dinuclear cyclopentadienyl–indenyl complexes of iron(II) and further reactions to mixed tri- and tetranuclear iron–cobalt complexes

“…The NMR spectra were recorded at 300 K on a Bruker Avance 500 ( 1 H NMR 500 MHz, 13 C NMR 125 MHz) or on a Bruker AC300 ( 1 H NMR 300 MHz, 13 C NMR 75 MHz) spectrometer. 1 H NMR spectra were referenced to residual protons of the solvent, 13 C NMR to the solvent signal (C 6 D 6 : d H = 7.27 ppm, d C = 128.00 ppm) as standard.…”

“…1 H NMR (C 6 D 6 , 500 MHz, 300 K), d (ppm): 7.94, 7.36 (2 d, 2 Â 1H, H7 0 , H4 0 ), 7.08 (t, 2H, H5 0 , H6 0 ), 6.10, 6.13 ( 5 ). 13 C NMR (C 6 D 6 , 75 MHz, Table 4 Crystallographic data of 1, meso-2, rac-3, meso-4 and 5. a 1 meso-2 rac-3 meso-4 5 …”

“…The presence of two fused psystems in the indenyl system enables this bicyclic arene to act as a bridging ligand in homo-and heterobinuclear complexes [L n M(lg:g-ind)M 0 L 0 n ]. However, examples for such a bridging coordination mode are still relatively rare [9][10][11][12][13][14], and especially in the area of multidecker sandwich complexes the number of structurally characterized examples is limited to few examples in which indenyl acts as a central l-g 5 :g 6 -bridge between [(g 5 -C 5 (R) 5 )Ru] (R = H, CH 3 ) and [(g 4 -C 4 (CH 3 ) 4 )Co] fragments [15,16].…”

“…: C, 72.65; H, 5.46. 1 H NMR (C 6 D 6 , 500 MHz, 300 K), d (ppm): 2.55 (s, 6H, CH 3 ), 3.83 (s, 10H, C 5 H 5 ), 4.01 (d, 2H, H2), 4.75 (d, 2H, H3), 6.80 (m, 4H, H5, H6), 7.40 (m, 2H, H7), 7.73 (m, 2H, H4) 13. C NMR (C 6 D 6 , 75 MHz, 297 K), d (ppm): 32.43 (C(CH 3 ) 2 ), 36.28 (C(CH 3 ) 2 ), 60.05 (C2), 69.32 (C 5 H 5 ), 70.41 (C3), 85.39 (C1), 88.53 (C7a), 93.48 (C3a), 122.87, 122.88 (C5, C6), 128.47 (C7), 128.53 (C4).…”