852995-10-9Relevant academic research and scientific papers
Substituents effects in POP pincer complexes of ruthenium
Major, Quinn,Lough, Alan J.,Gusev, Dmitry G.
, p. 2492 - 2501 (2005)
Reactions of [RuCl2(p-cymene)]2 with ( tBu2PCH2CH2)2O (POP- tBu) and (iPr2PCH2CH 2)2O (POP-iPr) afforded RuCl 2(POP-tBu) (1) and [Ru2(μ-Cl) 3(POP-iPr)2]Cl (2·Cl), respectively. The POP ligand is coordinated in a mer fashion in complex 1, whose crystal structure revealed a γ-agostic C-H...Ru interaction of one tBu group. Spectroscopic evidence indicated that this agostic interaction is retained in 1 in solution. A related compound, [Ru(N 2)Cl(POP-tBu)]BPh4 (4), which also showed agostic bonding of a tBu group, was obtained by substitution of N2 for Cl- in 1, in the presence of NaBPh4. Compound 2·Cl readily underwent ion exchange with LiBPh4 or LiPF6 to give 2·BPh4 or 2·PF6 salts, respectively. A crystallographic analysis of 2·PF6 established a co-facial bioctahedral geometry of the [Ru2(μ-Cl) 3(POP-iPr)2]+ cation containing two POP ligands coordinated in a fac fashion. Reactions of 1 and 2 with H 2 afforded the dihydrogen complexes cis,trans-Ru(H 2)Cl2(POP-tBu) (3) and cis,cis-Ru(H 2)Cl2(POP-iPr) (5), respectively. The H-H bond distances are very similar in both compounds, r(H-H) = 1.0 ± 0.1 A, based on the T1min and JHD data and results of DFT calculations. Reaction of 2 with N2 gave the dinitrogen complex cis,cis-Ru(N2)Cl2(POP-iPr) (6), but solutions of 1 under a nitrogen atmosphere showed no evidence of an analogous compound. The different steric requirements of the phosphorus substituents of the POP ligands were identified as the source of the differences in the coordination properties of the POP-tBu and POP-iPr complexes 1-6.
