Gold(III) six-membered N^C^N pincer complexes: synthesis, structure, reactivity and theoretical calculations.
The first six-membered gold(III) N^C^N pincer complex was obtained in good yield, under very mild conditions, by transmetalation of [Hg(κC-N^C^N)Cl] (N^CH^N = 1,3-bis(pyridin-2-ylmethyl)benzene, HL(1)) with Na[AuCl(4)]. The X-ray crystal structure of [Au(N^C^N)Cl][PF(6)] showed that the fused six-membered metallacycles each exist in a strongly puckered boat conformation. As shown by the (1)H NMR spectra in various solvents, the same structure is also retained in solution: no inversion of the six-membered metallacycles is observed in DMSO up to 95 °C. This correlates well with a reaction barrier of 17.5 kcal/mole, as determined by quantum chemical calculations. The reactivity of the present pincer complex is compared to that of the analogous 1,3-bis(2-pyridyl)benzene, HL(2), derivative, which has five-membered fused metallacycles. Sharp differences are found in the reactions with phosphines, such as PPh(3) and dppe (1,2-bis-diphenylphosphino-ethane), and with silver salts. Theoretical calculations were carried out on the two pincer complexes in order to try to understand these differences, and we found that the gold-chlorine bond is significantly stronger in the case of the complex containing five-membered metallacyclic rings.
Alesso
Giuseppe
G
Dipartimento di Chimica, Università degli Studi di Sassari, Via Vienna 2, I-07100, Sassari, Italy.
Cinellu
Maria Agostina
MA
Stoccoro
Sergio
S
Zucca
Antonio
A
Minghetti
Giovanni
G
Manassero
Carlo
C
Rizzato
Silvia
S
Swang
Ole
O
Ghosh
Manik Kumer
MK
D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006046:Gold / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory
D009942:Organometallic Compounds; D002244:Carbon; D006046:Gold; D009584:Nitrogen