Paramagnetic carbenemetal complexes. Part 1. Cationic chromium(I) complexes and the chemistry of their chromium(0) precursors and of related molybdenum(0) and Tungsten(0) complexes, especially with bulky carbene ligands C(OR′)R[R  CH(SiMe₃)₂or CH₂SiMe₃]

Abstract

Die Carbenmetall(0)‐Komplexe (II) werden ausgehend von den Hexacarbonylen (I) durch sukzessive Umsetzung mit entsprechenden Organyl‐Li‐ Verbindungen und Alkylierungsreagenzien dargestellt.

Synthesis and oxidation of (benzimidazolylidene)Cr(CO)5 complexes

“…The very similar ESR spectrum was also observed in the oxidation of 1 (g = 2.005, A N = 5.0 G, A H = 1.3 G) with (4-BrC 6 H 4 ) 3 -NSbCl 6 . In contrast, in LappertÕs imidazolylnylidene chromium radical cation complexes [5], these radicals are not coupled with nitrogen but coupled with only Cr and coordinated phosphines (Fig. 4).…”

“…To clarify the oxidized state, the benzimidazolylidene ligand was chosen partly because the radical cation species might be stabilized by delocalization through the enlarged p-conjugation. In this paper, we describe a general route to a series of (benzimidazolylidene)Cr(CO) 5 …”

“…Thus, the oxidized form of the imidazolylidene ligand is considered to increase the contribution of the back donation from metal center. Although some reactions of group 6 metal carbene complexes induced by oxidation and/or reduction have been reported [4], there are few reports concerning with the study of oxidized/reduced intermediates [5,6]. To clarify the oxidized state, the benzimidazolylidene ligand was chosen partly because the radical cation species might be stabilized by delocalization through the enlarged p-conjugation.…”

N-heterocyclic carbene complexes of Group 6 metals

“…In 1980, Lappert et al [58] reported that cationic Cr(I)-NHC complexes Cr-58(a-c) (Figure 4.6) could be prepared through the oxidation of their Cr(0) precursors Cr-4(a,b) and Cr-3 with …”

“…A series of Group 6 M(0) carbonyl complexes Cr-1(a,b), Mo-1(a-c), W-1(a,b), Mo-2(a,b), Mo-3a, Mo-4, and Cr-2 have been prepared through cleavage of electron-rich olefins with metal carbonyl precursors under thermal conditions [Cr-1a, M = Cr, n = 1, R = Me Cr-1b, M = Cr, n = 1, R = Et Mo-1a, M = Mo, n = 1, R = Me Mo-1b, M = Mo, n = 1, R = Et Mo-1c, M = Mo, n = 1, R = Bz Mo-3a, M = Mo, n = 2, R = Me W-1a, M = W, n = 1, R = Me W-1b, M = W, n = 1, R = Et Mo-2a, n = 1, R = Me Mo-2b, n = 1, R = p-Tol Mo-4, -4a, M = Cr, R = Et, L^L = dmpe Cr-4b, M = Cr, R = Et, L^L = dppe W-4a, M = W, R = Et, L = dppe W-4b, M = W, R = Bz, Reactivity of Cr-1(a,b), Mo-1(a-c), and W-1(a,b)towards phosphine and pyridine[55][56][57][58] 2.1.1.1 Cyclisation route In 1986, Fehlhammer et al reported that hydrogen isocyanide complexes M(CO) 5 (CNH) (M = Cr, Mo, W) reacted with aziridines at r.t. through protonation of aziridine, nucleophilic attack of cyano-N atom and ring-opening followed by intramolecular cyclisation, to give the imidazolidin-2-ylidene complexes Cr-1(c-e), Mo-1d and W-1c. Complex Cr-1f can be obtained when Cr(CO) 5 (CNH) reacting with N-methylaziridine but at higher temperature (60 °C).…”