Synthesis and characterization of xylene-based group-six metal PCP pincer complexes

Abstract

In the present study, the Cr(III) complex trans-[Cr(PCP CH2-iPr)(CH 3 CN)(Br) 2 ] as well as seven-coordinate cationic bromo carbonyl Mo(II) and W(II) complexes of the type [M(PCP CH2-iPr)(CO) 3 Br] (M=Mo, W) featuring PCP pincer ligands based on a xylene scaffold were prepared and characterized. The seven-coordinate bromo tricarbonyl complexes exhibit fluxional behavior in solution due to rapid CO ligand interconversions. The mechanism of this process was studied by means of DFT calculations. Structures of representative complexes were determined by single-crystal X-ray analyses.

Cr(II) and Cr(I) PCP Pincer Complexes: Synthesis, Structure, and Catalytic Reactivity

“…7 Complex 2b adopts a slightly distorted octahedral geometry around the metal center with the bromide ligands being in positions trans to one another. The same geometry was recently found for the analogous complexes trans-[Cr(PCP NEt 5,6 Treatment of 2a with 2 equiv of LiBH 4 in THF for 24 h afforded the borohydride complex [Cr(POCOP-tBu)(κ 2 -BH 4 )] (3) in 86% yield as an orange solid (Scheme 2). On the basis of EPR (see the Supporting Information) and solution magnetic susceptibility measurements (CH 2 Cl 2 , Evans method), 3 is also a d 4 high-spin complex with a solution effective magnetic moment of 4.9(1) μ B .…”

“…This complex exhibits a solution magnetic moment of μ eff = 4.0(1) μ B (CH 2 Cl 2 , Evans method) consistent with three unpaired electrons as expected for a d 3 configuration. The analogous Cr­(III) PCP complexes trans -[Cr­(PCP NEt - i Pr)­(Cl) 2 (THF)] and trans -[Cr­(PCP CH2 - i Pr)­(Br) 2 (CH 3 CN)] featuring NEt and CH 2 linkers, respectively, were reported recently. , …”

Synthesis, Characterization, and Catalytic Reactivity of {CoNO}8 PCP Pincer Complexes

“… 9 , 10 The analogous complex [Co(PCP CH2 - i Pr)Br] ( 1c ), where the PCP ligand features CH 2 -linkers, was prepared in analogous fashion by treatment of the ligand PCP CH2 - i Pr-Br with n BuLi and subsequent transmetalation in 65% isolated yield. 11 In analogy to 1a and 1b , complex 1c is a d 7 low spin complex with a solution magnetic moment μ eff of 2.3(1) μ B (Evans method). The solid-state structures of complexes 1b and 1c were determined by X-ray diffraction, and representations of the molecules are presented in Figures 1 and 2 .…”

“…The starting materials for the present study, [Co­(PCP NMe - i Pr)­Cl] ( 1a ) and [Co­(PCP O - i Pr)­Cl] ( 1b ), were obtained by the reaction of anhydrous CoCl 2 and PCP NMe/O - i Pr ( 1a , 1b ) in the presence of a strong base as reported previously. , The analogous complex [Co­(PCP CH2 - i Pr)­Br] ( 1c ), where the PCP ligand features CH 2 -linkers, was prepared in analogous fashion by treatment of the ligand PCP CH2 - i Pr-Br with n BuLi and subsequent transmetalation in 65% isolated yield . In analogy to 1a and 1b , complex 1c is a d 7 low spin complex with a solution magnetic moment μ eff of 2.3(1) μ B (Evans method).…”

“…Nitric oxide (NO 2.5) was purchased from MESSER GmbH (Gumpoldskirchen, Austria). The synthesis of 2-bromo-1,3-phenylene)bis(methylene)bis(diisopropylphosphane) (P(C–Br)P CH2 - i Pr), 11 [Co(PCP NMe - i Pr)Cl] ( 1a ), 9 [Co(PCP O - i Pr)Cl] ( 1b ), 10 and [Co(PCP NMe - i Pr)(CO) 2 ] ( 4a ) 16 was carried out according to the literature. 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectra were recorded on Bruker AVANCE-250 and AVANCE-400 spectrometers.…”