Synthesis, Structure, and Reactivity of Nitrosyl Pincer-Type Rhodium Complexes

GAVIGLIO, C; BEN DAVID, Y.; SHIMON, L.; DOCTOROVICH, F.; MILSTEIN, D

ORGANOMETALLICS

Año: 2009 vol. 28 p. 1917 - 1926

0276-7333

Pincer-type linear nitrosyl Rh(I) complexes, Rh(PCPtBu)(NO)][BF4] (2) and [Rh(PCPtBuCH2)(NO)][BF4] (8), are reported (PCPtBu ) 1,3-bis[(di-tert-butylphosphino)methyl]-2,4,6-trimethylbenzene). Complex 2 was synthesized by reaction of the Rh(I) dinitrogen complex Rh(PCPtBu)N2 (1) with NOBF4, whiletreatment of the methyl chloride complex Rh(PCPtBu)(CH3)Cl (7) with NOBF4 led to the formation of 8. Upon addition of CO, a linear T bent nitrosyl equilibrium was established, both in solution and in the solid state, between the linear nitrosyl Rh(I) complex 2 and the bent nitrosyl Rh(III) complex [Rh(PCPtBu)(NO)(CO)][BF4] (3). Addition of LiCl to complex 2 resulted in the quantitative formation of the bent nitrosyl complex Rh(PCPtBu)(NO)(Cl) (4). An IR study of solvent interactions of the nitrosylligand of complex 2 in various solvents is also presented, showing a linear T bent nitrosyl equilibrium induced by solvent coordination. Treatment of 4 with HBF4 · O(C2H5)2 led to chloride abstraction, with formation of complex 2. Upon addition of NOBF4 to the PNP Rh(I) complex [C5H3N(CH2P-(tBu)2)2Rh(CH3CN)]BF4 (5), the bent nitrosyl complex [C5H3N(CH2P(tBu)2)2Rh(CH3CN)(NO)][BF4]2 (6) was obtained. Employing 15NO-labeled complexes it is possible to assign the bent or linear modes of bonding of NO on the basis of 15N NMR spectroscopy. X-ray structures of all nitrosyl complexes reported here confirm that the tetracoordinate species are square-planar with a linear nitrosyl ligand occupying the position trans to the aromatic ring and the metal is Rh(I), whereas the pentacoordinate complexes adopt a square-pyramidal geometry with a bent apical nitrosyl coordinated to Rh(III).