Anionic Phosphinimine-Chelate Complexes of Rhodium and Iridium:  Steric and Electronic Influences on Oxidative Addition of CH₂Cl₂

The phosphinimines Ph 3 PNR (R = Ph 1, 2,6-Me 2 C 6 H 3 2, 3,5-Me 2 C 6 H 3 3, 2,6- i- Pr 2 C 6 H 3 4 ) were prepared and used to generate the species of the form [Li( o -C 6 H 4 PPh 2 NR)] 2 ·Et 2 O (R = Ph 5, 2,6-Me 2 C 6 H 3 6, 3,5-Me 2 C 6 H 3 7, 2,6- i -Pr 2 C 6 H 3 8 ). Subsequent reactions with [Rh(μ-Cl)(COD)] 2 gave the complexes Rh(COD)( o -C 6 H 4 PPh 2 NR) (R = Ph 9, 2,6-Me 2 C 6 H 3 10, 3,5-Me 2 C 6 H 3 11, 2,6- i -Pr 2 C 6 H 3 12 ). Similarly, the Ir analogue of 9 ( 13 ) was prepared using [Ir(μ-Cl)(COD)] 2 . The reaction of 9 with (CH 2 PPh 2 ) 2 afforded Rh(PPh 2 CH 2 CH 2 PPh 2 )( o -C 6 H 4 PPh 2 NPh) ( 14 ). Compound 9 was also shown to react with CH 2 Cl 2 to give two products, one of which was confirmed to be [Rh( o -C 6 H 4 PPh 2 NPh)(CH 2 - o -C 6 H 4 PPh 2 NPh)(μ-Cl) 2 Rh(COD)] ( 15 ). Similar treatment of 10 and 12 with CH 2 Cl 2 showed no reaction, while reaction of 11 with CH 2 Cl 2 gave a mixture of unidentified products. The related imidazole-phosphinimine ligands (N 2 C 3 H 3 )PPh 2 NR (R = Ph 18, 2,6-Me 2 C 6 H 3 19 ) were also prepared. These ligands react with NaH to give the corresponding Na-imidazolate-phosphinimines, 20 and 21, and subsequent reaction with [Rh(μ-Cl)(COD)] 2 gave the complexes Rh(COD)((N 2 C 3 H 2 )PPh 2 NR) (R = Ph 22, 2,6-Me 2 C 6 H 3 23 ). The compounds 22 and 23 do not react with CH 2 Cl 2 . The effects of steric and electronic modifications to the ligands on oxidative addition of C−Cl bonds are discussed. DFT calculations were performed on the model fragments [Rh((C 6 H 4 )PH 2 NH)] and [Rh((N 2 C 3 H 2 )PH 2 NH)], and the calculated atomic charges provide some insight into the reactivity of these compounds.