ja5b10074_si_002.cif (20.99 kB)
Cyclo‑P3 Complexes of Vanadium: Redox Properties and Origin of the 31P NMR Chemical Shift
dataset
posted on 2015-12-09, 00:00 authored by Balazs Pinter, Kyle T. Smith, Masahiro Kamitani, Eva M. Zolnhofer, Ba L. Tran, Skye Fortier, Maren Pink, Gang Wu, Brian C. Manor, Karsten Meyer, Mu-Hyun Baik, Daniel J. MindiolaThe
synthesis and characterization of two high-valent vanadium–cyclo-P3 complexes, (nacnac)V(cyclo-P3)(Ntolyl2) (1) and (nacnac)V(cyclo-P3)(OAr) (2), and an inverted
sandwich derivative, [(nacnac)V(Ntolyl2)]2(μ2-η3:η2-cyclo-P3) (3), are presented. These novel complexes
are prepared by activating white phosphorus (P4) with three-coordinate
vanadium(II) precursors. Structural metrics, redox behavior, and DFT
electronic structure analysis indicate that a [cyclo-P3]3– ligand is bound to a V(V) center
in monomeric species 1 and 2. A salient
feature of these new cyclo-P3 complexes
is their significantly downfield shifted (by ∼300 ppm) 31P NMR resonances, which is highly unusual compared to related
complexes such as (Ar[iPr]N)3Mo(cyclo-P3) (4) and other cyclo-P3 complexes that display significantly upfield shifted
resonances. This NMR spectroscopic signature was thus far thought
to be a diagnostic property for the cyclo-P3 ligand related to its acute endocyclic angle. Using DFT calculations,
we scrutinized and conceptualized the origin of the unusual chemical
shifts seen in this new class of complexes. Our analysis provides
an intuitive rational paradigm for understanding the experimental 31P NMR spectroscopic signature by relating the nuclear magnetic
shielding with the electronic structure of the molecule, especially
with the characteristics of metal–cyclo-P3 bonding.