Versatile Modes of Cooperative B−H Bond Activation Reactions in Ruthenium‐Carbene Complexes: Addition, Ring‐Opening and Insertion

Abstract

Cooperative B-H bond activation reactions with thio- and iminophosphoryl tethered ruthenium-carbene complexes are reported. The complexes show surprisingly different reactivities towards the commonly employed boranes CatBH, PinBH and BH ⋅LB as a result of different modes of metal-ligand cooperation. Although the iminophosphoryl system allows for selective 1,2-addition of the B-H bond across the Ru=C double bond, the sulfur analogue only delivers the 1,2-addition product for CatBH, whereas activation of BH and PinBH lead to further insertion reactions in one or more sides of the Ru-C-P-S-ring. The different reactivities can be explained by the differences in the electronics of the carbene complexes and the phosphoryl tether and by the Lewis acidities of the boranes. DFT calculations show that the mechanism of the reactions either proceeds by an addition across the Ru=C bond with different regioselectivities or across the Ru-S linkage.

Geminal Dianions Stabilized by Main Group Elements

“…[266][267][268] As mentioned in their first report, 266 attempts to obtain 135 by similar procedures to the one employed in the synthesis of 130 were unfruitful. They succeeded to isolate 135 by heating a benzene solution containing Me 3 PF 2 and the ylide Me 3 P=CH-SiMe 3 (133). 269 273 In strong agreement with a highly electron-rich carbon atom, the carbodiphosphorane nature of 144 was evidenced by its very diagnostic signal displayed in 13 C NMR for the central carbon that resonates at high-field ( = 11.8 ppm, 1 J P,C = 122, 119 Hz).…”

Tuning Ruthenium Carbene Complexes for Selective P−H Activation through Metal‐Ligand Cooperation

“…Since the PÀ H activation could also proceed via a concerted 1,2-addition or an oxidative addition at the metal centre followed by proton transfer, these two pathways have also been investigated exemplarily for the combination 2a'/HPPh 2 . The energy of the transition state for the concerted 1,2-addition across the Ru=C linkage (Conc, 16), Ru1À P1 2.2585(4), Ru1À P2 2.3856(4), C1À P1 1.7691 (17), C1À S1 1.7295( 16), P1À C8 1.8068 (17), P1À C2 1.8237 (17), S1À C14 1.7785 (18), S1À O1 1.4428(13), S1À O2 1.4472(13), P2À N1 1.5689( 14), S1À C1À P1 127.28 (10), P2À N1À Si1 144.29 (10). Scheme 3.…”

“…All hydrogen atoms except for the methylene bridges and the phosphine moieties have been omitted for clarity. Selected bond lengths [Å] and angles [°]: 3 a: C1À Ru1 2.181(2), C1À P1 1.813(2), C1À S1 1.7560(19), S1À O1 1.4421(17), S1À O2 1.4461(17), S1À C14 1.775(2), P1À N1 1.5366(19), P1À C2 1.831(2), P1À C8 1.804(2), Ru1À C13 2.074(2), Ru1À P2 2.2848(5), S1À C1À P1 117.52(10), Ru1À C1À P1 107.29(10), P1À N1À Si1 156.82(14). 6: Ru1À C1 2.174(2), C1À S1 1.770(2), S1À O1 1.4457(16), S1À O2 1.4511(16), S1À C14 1.770(2), C1À P1 1.817(2), P1À N1 1.5455(19), P1À C8 1.803(2), P1À C2 1.825(2), N1À Si1 1.6633(19), Ru1À P2 2.2785(5), S1À C1À P1 115.81(11), P1À N1À Si1 146.89(14).…”

Evaluation of the Lewis acidity of metal complexes using ESI mass spectrometry

“…2 That is because the metal complexes possess Lewis acidity, the substrates can be coordinated and thereby activated by the metal center for subsequent reaction. Thus, the Lewis acidity of metal complexes has a critical effect on the catalytic performance [3][4][5] and the judicious evaluation of the Lewis acidity plays a guiding role in catalyst design.…”