Carbide complexes as π-acceptor ligands

Abstract

A terminal carbide complex binds as a π-acceptor towards electron-rich metal centers, mirroring CO, and provides the first homoleptic, carbide-ligated complex.

Modification of σ‐Donor Properties of Terminal Carbide Ligands Investigated Through Carbide–Iodine Adduct Formation

“…Conversely, there is no apparent shift in the intense I−I stretching frequency (at 135 cm −1 for both isotopes). The Ru≡C stretching modes (1032–1036 cm −1 ) are insensitive to the identity of X but occur at lower frequencies than those in the parent RuC complexes ( RuC : 1050 cm −1 ), in line with weakening of the Ru≡C bond upon coordination.…”

Chromium carbides and cyclopropenylidenes

“…The neutral carbido complexes [(L) 2 Cl 2 M≡C:] (M = Ru, [17][18][19] Os; 20 L = PPh 3 , PCy 3 , NHC), originally synthesized by Heppert in 2002, 17 can form dative bonding Lewis pairs with various transition metals. [21][22][23][24][25] The anionic terminal carbide [(Ar t BuN) 3 Mo≡C] -(Ar = m-Xylyl) has been prepared by Cummins and coworkers via deprotonation of a terminal methylidyne complex. 26 Akin to the neutral terminal carbides, [17][18][19][20][21] the anionic carbides also bind various metals to form dinuclear structures, but those dinuclear carbido complexes have a metallocarbyne character.…”

Synthons for carbide complex chemistry

“…These fragments would nonetheless have potential relevance to substrate conversion by nitrogenases 9 and Fischer-Tropsch process catalysts. 10 Though reaction of the terminal ruthenium carbide complex, (Cy 3 P) 2 Cl 2 RuRC (RuC, Cy = cyclohexyl), with non-metal fragments 11 occasionally induces ligand migration, 12 metallation invariably leaves an intact RuC coordination sphere, 13,14 i.e. (Cy 3 P) 2 Cl 2 RuRC-[M].…”

“…This emphasizes the unique reactivity of trans-PtCl 2 (py) 2 towards RuC as compared to other metal fragments. 13,14 Structurally, py2 RuCPt parallels Johnson's arylcarbyne, (Cy 3 P)Cl 3 RuRC(p-C 6 H 4 CH 3 ), 16 and Grubbs' homometallic [RuRC-Ru] complex. 17 Bond distances along the RuRC-Pt spine mirror known RuRC-Pt fragments 14 (Table 1), whereas the carbide bridge is unusually bent.…”

“…The coupling of nuclear spins indicates electronic delocalization across the A-frame complex, which sets dppm2 RuCPt apart from typical RuRC-Pt complexes. 14 Replacement of dppm by its saturated analogue, CH 2 (PCy 2 ) 2 (dcpm), allows evaluation of changes in sterics and electrondonating abilities of the diphosphine ligands. Upon reaction with two equivalents of dcpm, py2 RuCPt readily associates with the first dcpm ligand, forming a [(m-dcpm)(Cy 3 P)RuRC-Pt] intermediate (identified by NMR, Scheme 2, cf.…”