805232-34-2Relevant academic research and scientific papers
Sterically hindered electron-withdrawing ligands: The reactions of N-carbazolyl phosphines with rhodium and palladium centres
Burrows, Andrew D.,Manon, Mary F.,Varrone, Maurizio
, p. 3321 - 3330 (2004)
The series of N-carbazolyl phosphines PPh3-n(NC 12H8)n (n = 1, L1; n = 2, L 2; n = 3, L3) has been synthesised using BuLi to generate the N-carbazolyl lithium salt, followed by reaction with the appropriate chlorophosphine. The reactions between [Rh(μ-Cl)(CO)2]2 and four equivalents of L1 or L2 gave [RhCl(CO)(L 1)2] 1 and [RhCl(CO)(L2)2] 2, though attempts to synthesise the analogous complex using L3 resulted in the formation of [Rh(μ-Cl)(CO)(L3)]2 3 instead. The inability of L3 to cleave the chloride bridges can be related to its considerable steric requirements. The electronic properties of L1-3 were assessed by comparison of the (CO) values of the [Rh(acac)(CO)(L 1-3)] complexes 4-6. The increase in number of N-carbazolyl substituents at the phosphorus atom results in a decrease of the σ-donor and increase in the π-acceptor character in the order L1 2 3. In the reactions of L1-3 with [PdCl2(cod)] only L1 was able to displace cod from the metal centre and form [PdCl2(L1)2] 7. The use of [PdCl2(NCMe)2] instead of [PdCl2(cod)] resulted in the formation of the complexes [PdCl2(L1) 2] 7 from L1, the cyclometallated complex [Pd(μ-Cl){P(NC12H8)2(NC12H 7)-κ2P,C}]2 8 from L3, and a mixture of [PdCl2(L2)2] 9 and [Pd(μ-Cl){PPh(NC 12H8)(NC12H7)-κ2P, C}]2 10 from L2. The reaction of L3 with [Pd(OAc)2] produced the cyclometallated complex [Pd(μ-O 2CCH3){P(NC12H8)2(NC 12H7)-2P,C}]211. The reaction of L3 with [Pd2(dba)3]·CHCl3 produced the 14-electron complex [Pd(L3)2] 12. The X-ray crystal structures of six complexes are reported, all of which show the presence of C-H...Pd hydrogen bonding.
