Synthesis and molecular structure of four-coordinate neutral and cationic diphenylcarbenerhodium(I) complexes

Abstract

Abstract Neutral diphenylcarbenerhodium(I) complexes of the general composition trans -[RhX(CPh 2 )(P i Pr 3 ) 2 ] (X=F ( 3 ), OCN ( 4 ), CF 3 CO 2 ( 5 ), PhCO 2 ( 6 ), CF 3 SO 3 ( 7 )) were prepared from the chloro or bromo precursors trans -[RhCl(CPh 2 )(P i Pr 3 ) 2 ] ( 1 ) and trans -[RhBr(CPh 2 )(P i Pr 3 ) 2 ] ( 2 ) by salt metathesis in acetone and isolated in excellent yields. While treatment of 1 with Tl(acac[F 6 ]) afforded the substitution product trans -[Rh(κ 1 -acac[F 6 ])(CPh 2 )(P i Pr 3 ) 2 ] ( 8 ), the corresponding reaction of 1 with Tl(acac) gave the chelate compound [Rh(κ 2 -acac)(CPh 2 )(P i Pr 3 )] ( 9 ) with only one phosphine ligand attached to the metal center. In acetone solution, the triflato complex 7 is in equilibrium with the cation trans -[Rh{OC(CH 3 ) 2 }(CPh 2 )(P i Pr 3 ) 2 ] + which after addition of NaBAr F 4 precipitates as the BAr F 4 salt 11 . The starting material 1 as well as the bis(triphenylphosphine) and bis(triisopropylstibine) analogues 14 and 15 react with pyridine or acetonitrile in the presence of KPF 6 to yield the cationic complexes trans -[Rh(py)(CPh 2 )(PPh 3 ) 2 ]PF 6 ( 16 ) and trans -[Rh(CH 3 CN)(CPh 2 )(L) 2 ]PF 6 (L=P i Pr 3 ( 17 ), Sb i Pr 3 ( 18 )). The BAr F 4 salt of the cation trans -[Rh(CH 3 CN)(CPh 2 )(Sb i Pr 3 ) 2 ] + ( 19 ) was characterized by X-ray crystallography. Compounds 11 , 16 – 19 and the bis(pyridine) derivative cis -[Rh(CPh 2 )(NC 5 H 5 ) 2 (P i Pr 3 )]PF 6 ( 12 ) are the first representatives of four-coordinate cationic diphenylcarbenerhodium(I) complexes.