Laurence John Taylor

Peri-substituted bis(tertiary) phosphine-arsine Acenap(PiPr₂)(As(SPh)Ph) (4, Acenap = acenaphthene-5,6-diyl) was synthesized by the reaction of the chloroarsine (PiPr₂)(AsPhCl) with PhSLi. The X-ray crystal structure of this compound reveals an intramolecular P∙∙∙As–Cl pnictogen bond, with the phosphorus lone pair donating into the As–S σ* orbital.

Here, we report an improved synthesis of the bulky phosphanide anion [P(SiⁱPr₃)₂]^- in synthetically useful yields and its complexation to group 12 metals. The ligand is obtained as the sodium salt NaP(SiⁱPr₃)₂ 1 in a 42% isolated yield and a single step from red phosphorus and sodium. This is a significantly higher-yielding and safer preparation compared to the previously reported synthesis of this ligand, and we have thus applied 1 to the synthesis of the two-coordinate complexes M[P(SiⁱPr₃)₂]₂ (M = Zn, Cd, Hg). These group 12 complexes are all monomeric and with nonlinear P-M-P angles in the solid state, with DFT calculations suggesting that this bending is due to the steric demands of the ligand. Multinuclear NMR spectroscopy revealed complex second-order splitting patterns due to strong PP' coupling. This work demonstrates that the synthesis of 1 is viable and provides a springboard for the synthesis of low-coordinate complexes featuring this unusual bulky ligand.

Here, we report the first practical synthesis of the bulky phosphanide anion [P(SiiPr3)2]− in synthetically useful yields, and its complexation to Group 12 metals. The ligand is obtained as the sodium salt NaP(SiiPr3)2 1 in a 42% isolated yield and a single step from red phosphorus and sodium. This is a significant improvement on the previously reported synthesis of this ligand, and we have thus applied 1 to the synthesis of the two-coordinate complexes M[P(SiiPr3)2]2 (M = Zn, Cd, Hg). These Group 12 complexes are all monomeric and with non-linear P–M–P angles in the solid state, with DFT calculations suggesting that this bending is due to the steric demands of the ligand. Multinuclear NMR spectroscopy revealed complex 2nd order splitting patterns due to strong PP’ coupling. This work demonstrates that the synthesis of 1 is viable and provides a springboard for the synthesis of low-coordinate d-block complexes featuring this unusual bulky ligand.

We report the total synthesis of seven Illicium-derived neolignans along with experimental evidence which unites homooligomers and apparent heterooligomers under a new biosynthesis proposal that features a single common precursor.

In situ monitoring and reaction sampling (IR, NMR, EPR, Mössbauer spectroscopy) and structural characterisation of isolable species allows detailed mechanistic insight into the scission/homologation of CO by two-coordinate iron terphenyl complexes.

Two mixed peri-substituted phosphine-chlorostibines, Acenap(PiPr₂)(SbPhCl) and Acenap(PiPr₂)(SbCl₂) (Acenap = acenaphthene-5,6-diyl) reacted cleanly with Grignard reagents or nBuLi to give the corresponding tertiary phosphine-stibines Acenap(PiPr₂)(SbRR’) (R, R’ = Me, iPr, nBu, Ph). In addition, the Pt(II) complex of the tertiary phosphine-stibine Acenap(PiPr₂)(SbPh₂) as well as the Mo(0) complex of Acenap(PiPr₂)(SbMePh) were synthesised and characterised. Two of the phosphine-stibines and the two metal complexes were characterised by single-crystal X-ray diffraction. The peri-substituted species act as bidentate ligands through both P and Sb atoms, forming rather short Sb-metal bonds. The tertiary phosphine-stibines display through-space J(CP) couplings between the phosphorus atom and carbon atoms bonded directly to the Sb atom of up to 40 Hz. The sequestration of the P and Sb lone pairs results in much smaller corresponding J(CP) being observed in the metal complexes. QTAIM (Quantum Theory of Atoms in Molecules) and EDA-NOCV (Energy Decomposition Analysis employing Naturalised Orbitals for Chemical Valence) computational techniques were used to provide additional insight into a weak n(P)→σ*(Sb-C) intramolecular bonding interaction (pnictogen bond) in the phosphine-stibines.

Ruthenium complexes of phosphinocarboxamide ligands, and their use to form metallacycles using halide abstraction/deprotonation reactions are reported. Thus, [Ru(p-cym){PPh₂C(=O)NHR}Cl₂; R = ⁱPr (1), Ph (2), p-tol (3)] and [Ru(p-cym){PPh₂C(=O)N(R)C(=O)N(H)R}Cl₂; R = Ph (4), p-tol (5)] were synthesized from [(p-cym)RuCl₂]₂ (p-cym = para-cymene) and phosphinocarboxamides or phosphinodicarboxamides, respectively. Single-crystal X-ray diffraction measurements on 1–5 reveal coordination to ruthenium through the phosphorus donor, with an intramolecular hydrogen bond between the amine-bound proton and a metal-bound chloride. Six-membered metallacycles formed by halide abstraction/deprotonation of complexes 4 and 5 afforded [Ru(p-cym){κ²-P,N-PPh₂C(=O)N(R)C(=O)NR}Cl] [R = Ph (6), p-tol (7)]. These species exist as a mixture of two rotational isomers in solution, as demonstrated by NMR spectroscopy.

A series of peri-substituted acenaphthene-based phosphine selenoether bidentate ligands Acenap(iPr₂P)(SeAr) (L1-L4, Acenap = acenaphthene-5,6-diyl, Ar = Ph, mesityl, 2,4,6-trisopropylphenyl and supermesityl) were prepared. The rigid acenaphthene framework induces a forced overlap of the phosphine and selenoether lone pairs, resulting in a large magnitude of through-space ⁴J_PSe coupling, ranging from 452 to 545 Hz. These rigid ligands L1-L4 were used to prepare a series of selected late d-block metals, mercury, and borane complexes, which were characterized, including by multinuclear NMR and single-crystal X-ray diffraction. The Lewis acidic motifs (BH₃, Mo(CO)₄, Ag⁺, PdCl₂, PtCl₂, and HgCl₂) bridge the two donor atoms (P and Se) in all but one case in the solid-state structures. Where the bridging motif contained NMR-active nuclei (¹¹B, ¹⁰⁷Ag, ¹⁰⁹Ag, ¹⁹⁵Pt, and ¹⁹⁹Hg), J_PM and J_SeM couplings are observed directly, in addition to the altered J_PSe in the respective NMR spectra. The solution NMR data are correlated with single-crystal diffraction data, and in the case of mercury(II) complexes, they are also correlated with the solid-state NMR data and coupling deformation density calculations. The latter indicate that the through-space interaction dominates in free L1, while in the L1HgCl₂ complex, the main coupling pathway is via the metal atom and not through the carbon framework of the acenaphthene ring system.

A binuclear tungsten(0) complex with an asymmetric bridging 1,2-diphosphole ligand was prepared by the photolysis of tungsten hexacarbonyl in the presence of 1-isopropyl-2-phenyl-1,2,5,6-tetrahydroacenaphtho [5,6-cd][1,2]diphosphole. The tungsten complex 1 was characterized by high resolution mass spectrometry, multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P), and elemental microanalysis. The structure of the trans isomer was resolved by single crystal X-ray diffraction, showing a slight elongation of the P−P bond upon coordination to the W(CO)₅ groups.

Treatment options for the management of breast cancer are still inadequate. This inadequacy is attributed to the lack of effective targeted medications, often resulting in the recurrence of metastatic disorders. Cumulative evidence suggests that epidermal growth factor receptor (EGFR-TK) and cyclin-dependent kinases-9 (CDK-9) overexpression correlates with worse overall survival in breast cancer patients. Pyranopyrazole and pyrazolone are privileged options for the development of anticancer agents. Inspired by this proven scientific fact, we report here the synthesis of two new series of suggested anticancer molecules incorporating both heterocycles together with their characterization by IR, ¹H NMR, ¹³C NMR, ¹³C NMR-DEPT, and X-ray diffraction methods. An attempt to get the pyranopyrazole-gold complexes was conducted but unexpectedly yielded benzylidene-2,4-dihydro-3H-pyrazol-3-one instead. This unexpected result was confirmed by X-ray crystallographic analysis. All newly synthesized compounds were assessed for their anti-proliferative activity against two different human breast cancer cells, and the obtained results were compared with the reference drug Staurosporine. The target compounds revealed variable cytotoxicity with IC₅₀ at a low micromolar range with superior selectivity indices. Target enzyme EGFR-TK and CDK-9 assays showed that compounds 22 and 23 effectively inhibited both biological targets with IC₅₀ values of 0.143 and 0.121 µM, respectively. Molecular docking experiments and molecular dynamics simulation were also conducted to further rationalize the in vitro obtained results. Communicated by Ramaswamy H. Sarma