Synthesis and Properties of [NiCp*(2,5‐tBu₂PC₄H₂)], a 20‐Valence‐Electron Phosphanickelocene

Abstract

The reaction of the bulky phospholide salt Li(2,5-tBu2PC4H2) x 2THF (1; THF = tetrahydrofuran) with [NiCp*(acac)] (HCp* = pentamethylcyclopentadiene, Hacac = acetylacetone) gives the green air-sensitive phosphanickelocene [NiCp*(2,5-tBu2PC4H2)] (2) in yields of about 85%. An X-ray structural determination of 2 shows long Ni-ring bonds and "delocalised" ring P-C and C-C bonds characteristic of a classical 20-valence-electron (ve) nickelocene. The electronic structure of 2 has been clarified through a combined Amsterdam density functional (ADF) and photoelectron spectroscopic study, which indicates that the higher lying semi-occupied molecular orbital (SOMO) (-5.82 eV) has a' symmetry and that the phosphorus "lone pair" is energetically low-lying (-8.15 eV). Oxidation of phosphanickelocene 2 by AgBF4 occurs quantitatively to give the corresponding air-sensitive orange phosphanickelocenium salt [NiCp*(2,5-tBu2PC4H2)][BF4] (3). This complex has also been characterised by an X-ray crystallographic study, which reveals long Ni-C(alpha) and short C(alpha)-C(beta) bonds in the phospholyl ligand indicative of a SOMO having a'' symmetry. PMe3 reacts with 2 at room temperature to provoke a ring-slip reaction that gives the 18ve complex [NiCp*eta1-(2,5-tBu2PC4H2)(PMe3)] (4), but shows no reaction with the phosphanickelocenium salt 3 under the same conditions.

Cycloheptatrienyl Zirconium Sandwich Complexes with Lewis Basic Phospholyl Ligands (Phosphatrozircenes): Synthesis, Structure, Bonding and Coordination Chemistry

“…[5,35] Additionally, few theoretical experiments on phospholyl complexes are present in the literature, [12,36] with landmark molecular orbital calculations on phosphaferrocenes probably being the most important.…”

Synthesis, Structure and Reactivity of Trimethylsilyl‐Substituted Phosphametallocenes

“…The steric bulk of the SiMe 3 groups becomes apparent from the angles Fe-Ct1-Si (95.7°, 96.8°), which exceed the ideal value of 90°, while the deviation for the β-Me groups is significantly smaller (90.9°, 91.1°). In conclusion, the structural parameters of the parent compound differ only very slightly from those observed for the related phosphaferrocene and ruthenocene ([Cp*M{(2,5-tBu 2 )C 4 H 2 P}], M = Fe, [20] Ru [21] ) with tBu groups in place of the Me 3 Si groups. A closely related molecule with alkynyldimethylsilyl substituents was obtained by Mathey et 6 ].…”

A Persistent Dipotassium 1,2,4‐Diazaphospholide Radical Complex: Synthesis, X‐Ray Structure, and Bonding

“…Probably owing to their high reactivity, anion radicals derived by reduction of five-membered heterocyclic aromatic systems have never been characterized structurally [7] before the present work. The deprotonated 1H-1,2,4-diazaphosphole group [3,5-R 2 dp] À (B) is a mixed nitrogen-phosphorus (s 2 l 3 ) analogue of Cp À and may be viewed as the combination of phospholyl [3,8] and pyrazolato (pz) [9] ions. Theoretical analyses and photoelectron spectra suggested that azaphospholes containing s 2 l 3 phosphorus atoms are highly aromatic.…”