Bridging Rhodium–Iron Borataaminocarbyne Complexes Formed by Intramolecular Isonitrile–Borane Coordination

Abstract

Reaction of [(TXPB)Rh(μ-CO)2Fe(CO)Cp] (1; TXPB = 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene) with both aryl and alkyl isonitriles formed [(TXPB)Rh(μ-CO)(μ-CNR)Fe(CO)Cp] (R = C6H4Cl-p (2), Xyl (3), n Bu (4); Xyl = 2,6-dimethylphenyl), in which the CNRBR3 unit is best described as a borataaminocarbyne ligand with single bonds between carbon and nitrogen and between nitrogen and boron. The carbon atom of the borataaminocarbyne ligand is doubly bound to iron and singly bound to rhodium. For comparison, borane-free [(TXPH)Rh(μ-CO)2Fe(CO)Cp] (5; TXPH = 2,7-di-tert-butyl-4-diphenylphosphino-9,9-dimethylthioxanthene) was prepared from [(TXPH)RhCl(CO)] and K[CpFe(CO)2], and reaction of 5 with either 1 or 2 equiv of CNC6H4Cl-p afforded [(TXPH)Rh(CO)(μ-CNC6H4Cl-p)2Fe(CO)Cp] (6), which contains two μ-isonitrile ligands and two terminal carbonyl ligands: one bound to iron and the other to rhodium. The C–N stretching frequency for 6 is 124 cm–1 higher than that for the TXPB CNC6H4Cl-p complex 2, and the Rh–(μ-CNR) and Fe–(μ-CNR) distances are notably longer than those in 2, and the C–N distance is shorter.

Aminocarbyne ligands in organometallic chemistry

“…Lewis acids other than protonating and classical alkylating agents may react with isocyanide complexes to form aminocarbyne-like species. The addition to isocyanides of a range of metal dihalides and boranes yield, respectively, 'metallaaminocarbynes' and 'borataaminocarbynes', which might be viewed as bi-or tri-metallic units bridged by a C,N isocyanide moiety and will not be discussed further [112,113,235,236,237,238,239]. An overview of 2-aminocarbyne-like ligands derived from the possible isocyanide-Lewis acid combinations is given in Scheme 43.…”

Platinum Complexes of a Borane‐Appended Analogue of 1,1′‐Bis(diphenylphosphino)ferrocene: Flexible Borane Coordination Modes and in situ Vinylborane Formation

“…For example, addition of TXPB to [Pd 2 (dba) 3 ] (dba= trans , trans ‐dibenzylideneacetone) afforded [Pd(dba)(TXPB)], in which dba bridges between palladium and boron to generate a zwitterionic η 3 ‐boratoxyallyl complex 10. Furthermore, addition of isonitriles (RNC; R= n Bu, 2,6‐dimethylphenyl, para ‐chlorophenyl) to [(TXPB) Rh(μ‐CO) 2 Fe(CO)Cp] provided [(TXPB)Rh(μ‐CNR)(μ‐CO)Fe(CO) Cp] complexes that feature a bridging borataaminocarbyne ligand 27. Additionally, a range of Rh, Pd, and Pt complexes with a halide bridging between the metal and the borane have been isolated 11.…”

Metal–ligand cooperation at tethered π-ligands

“…The ligand was shown to be versatile and gave rise to a broad variety of complexes, but problems were encountered as the central thioether donor group was shown to be easily replaced from the metal center. 66,75,76 Therefore, a new ligand system was designed containing a bisphosphine moiety instead. A ferrocene group was included to provide increased flexibility, while still remaining a firmly bound complex.…”