Carbene Iridium(I) and Iridium(III) Complexes Containing the Metal Center in Different Stereochemical Environments

The mixed-ligand complex [IrCl(C 2 H 4 )(Sb i Pr 3 )(P i Pr 3 )] ( 2 ), prepared from [IrCl(C 2 H 4 )(P i Pr 3 )] 2 ( 1 ) and Sb i Pr 3, reacts not only with CO, diphenylacetylene, and H 2 by ligand substitution or oxidative addition but also with diaryldiazomethanes R 2 CN 2 to give the four-coordinate iridium(I) carbenes [IrCl( CR 2 )(Sb i Pr 3 )(P i Pr 3 )] ( 8 − 10 ) in 60−70% isolated yield. In contrast, treatment of 2 and of the related cyclooctene derivative trans -[IrCl(C 8 H 14 )(Sb i Pr 3 ) 2 ] ( 12 ) with C 5 Cl 4 N 2 affords the diazoalkane complexes trans -[IrCl(N 2 C 5 Cl 4 )(Sb i Pr 3 )(E i Pr 3 )] ( 11, E = P; 13, E = Sb) without elimination of N 2 . Displacement of the stibine ligand in 8 − 10 by P i Pr 3 leads to the corresponding bis(phosphine) compounds trans -[IrCl( CR 2 )(P i Pr 3 ) 2 ] ( 14 − 16 ), while the reaction of 8 (R = C 6 H 5 ) with NaC 5 H 5 yields the half-sandwich-type complex [(η 5 -C 5 H 5 )Ir( CPh 2 )(P i Pr 3 )] ( 17 ). Protonation of 17 with HCl occurs stepwise to give via the iridium(III) alkyl [(η 5 -C 5 H 5 )IrCl(CHPh 2 )(P i Pr 3 )] ( 20 ) the ring-substituted isomer [(η 5 -C 5 H 4 CHPh 2 )IrHCl(P i Pr 3 )] ( 21 ); however, if 17 is treated with HBF 4, a cationic complex is formed which probably contains a η 3 -coordinated benzylic ligand. The square-planar iridium(I) carbenes 8 and 14 react with HBX 4 (X = F, Ar F ) to afford the ionic products [IrHCl( CPh 2 )(P i Pr 3 )(E i Pr 3 )]BX 4 ( 23, 24, E = P; 25, E = Sb) and with HCl to give the relatively labile octahedral species [IrHCl 2 ( CPh 2 )(P i Pr 3 )(E i Pr 3 )] ( 26, E = P; 27, E = Sb). Treatment of 8 and 14 with ethene yields, besides [IrCl(C 2 H 4 ) 2 (Sb i Pr 3 ) 2 ] ( 18 ) and/or trans -[IrCl(C 2 H 4 )(P i Pr 3 ) 2 ] ( 28 ), a mixture of two isomeric olefinic products CH 2 CHCHPh 2 ( 29 ) and CH 3 CH CPh 2 ( 30 ), the ratio of which is independent of the ligand sphere of the iridium precursor. The molecular structures of 13, 14, 17, and 24 have been determined by X-ray crystallography.