J. Derek Woollins

Inorganic backbone phosphines

Abstract The synthesis, reactivity and structures of bidentate ligands PEP (E=main group atom or group of atoms) are reviewed.

Naphthalene and related systems peri-substituted by Group 15 and 16 elements.

Synthetic and bonding aspects of heavier Group 15 (P, As, Sb, Bi) and 16 (S, Se, Te) peri-substituted naphthalenes, are discussed in this review. An important and unifying feature of the chemistry of these systems is the lively discussion about the nature of the interaction between peri-atoms. Are atoms bonded when they are closer than the sum of their van der Waals radii? Is there any (weak) bonding, or just a strained repulsive interaction? Positioning atoms of Group 15 and 16 at the naphthalene 1,8-positions provides leading systems with which to study these bonding issues.

THE PREPARATION AND COORDINATION CHEMISTRY OF IPR2P(E)NHP(E')IPR2 (E, E' =SE; E = SE, E' = S; E = S, E' = O; E, E' = O

Reaction of i Pr 2 PCl with (Me 3 Si) 2 NH gives i Pr 2 PNH i PPr 2 (not isolated) which was oxidised with sulfur/selenium/oxygen to give i Pr 2 P(E)NHP(E′) i Pr 2 (E, E′=Se; E=Se, E′=S; E=S, E′=O; E,E′=O). These neutral LH molecules readily undergo deprotonation/complexation to form simple ML 2 species and demonstrative examples with Zn, Cd, Pd, Pt are reported. The X-ray structure of two examples of i Pr 2 P(E)NHP(E′) i Pr 2 (E, E′=Se, E,E′=O) are reported. The molecules pack into infinite chains via H…E Hydrogen bonds. The X-ray structures of three typical metal complexes which illustrate tetrahedral (Cd[( i Pr 2 PSe) 2 ] 2 ) and square planar (Pt[N( i Pr 2 PSe) 2 ] 2 ) coordination at the metal centre as well as the ability of the ME 2 P 2 N ring to adopt the pseudo-chair conformation (Pt[ i Pr 2 P(Se)NHP(S) i Pr 2 ] 2 ) are also reported.

The preparation and structure of complexes containing simple sulphur-nitrogen ligands

Complexes avec les groupes NS, NSX, les diimines, complexes de S 2 N 2 H − , S 2 N 2 2− , S 3 N − et S 2 N 3 3−

Chemistry of azopyrimidines. Part II. Synthesis, spectra, electrochemistry and X-ray crystal structures of isomeric dichloro bis[2-(arylazo)pyrimidine] complexes of ruthenium(II) ☆

Abstract 2-(Arylazo)pyrimidines (aapm, 3) are new N,N′- chelating ligands in the azoimine family and were reacted with RuCl3 in ethanol under refluxing conditions. Three isomers of the composition Ru(aapm)2Cl2 have been chromatographically separated and are established as having trans–cis–cis (tcc), cis–trans–cis (ctc) and cis–cis–cis (ccc) configurations with reference to the order of coordination pairs as Cl; N(pyrimidine), N and N(azo), N′. Two of the three isomeric structures have been confirmed by X-ray crystallography. In both of these structures, the Ru–N(azo) distances are relatively shorter than those of Ru–N(pyrimidine), indicating stronger bonding in the former and the presence of a Ru-(aapm) π-interaction that is localised in the Ru-azo fragment. The isomer configuration is supported by IR and 1H NMR data. The complexes exhibit t2(Ru)→π*(aapm) MLCT transitions in the visible region. Redox studies show the Ru(III)/Ru(II) couple in the green complexes [tcc-Ru(aapm)2Cl2] at 1.1–1.2 V and in the blue complexes [ctc- and ccc-Ru(aapm)2Cl2] at 1.2–1.4 V versus saturated calomel electrode (SCE) and two successive azo reductions. The difference in the first metal and ligand redox potentials is linearly correlated with νCT [t2(Ru)→π*(aapm)].

Automated Chemical Crystallography

The first fully automated small-molecule robotic X-ray diffractometer is described. After demonstrating the utility of the instrument using multiple samples of ammonium bitartrate, we investigated the conformational chirality of diphenyl dichalcogenide (E(2)Ph(2), where E = S, Se, or Te). Structural and computational studies suggest that the two enantiomers are energetically indistinguishable. Therefore, it was unsurprising that we found (in 35 suitable data collections) the proportion 0.51:0.49 of M-S(2)Ph(2) to P-S(2)Ph(2) in the bulk sample. Interestingly, after 65 data collections of Te(2)Ph(2), (46 provided suitable data sets), we found the proportion 0.72 +/- 0.13 of M-Te(2)Ph(2), suggesting there could be a statistically significant preference for the M-enantiomer in the sample examined here. We found that Se(2)Ph(2) underwent homochiral crystallization, with all 24 crystals being M. Our experiments may represent a salutary lesson in statistical analysis.

Selenocarbonyl synthesis using Woollins reagent

Abstract [PhP(Se)(μ-Se)]2 selenates secondary and tertiary amides to the corresponding selenoamides in 30–70% yields at 130°C in toluene and indolizine-3-aldehydes to selenoaldehydes in 40–59% yield at 25°C.

Phosphorus-Based Functional Groups as Hydrogen Bonding Templates for Rotaxane Formation

We report on the use of the hydrogen bond acceptor properties of some phosphorus-containing functional groups for the assembly of a series of [2]rotaxanes. Phosphinamides, and the homologous thio- and selenophosphinamides, act as hydrogen bond acceptors that, in conjunction with an appropriately positioned amide group on the thread, direct the assembly of amide-based macrocycles around the axle to form rotaxanes in up to 60% yields. Employing solely phosphorus-based functional groups as the hydrogen bond accepting groups on the thread, a bis(phosphinamide) template and a phosphine oxide-phosphinamide template afforded the corresponding rotaxanes in 18 and 15% yields, respectively. X-ray crystallography of the rotaxanes shows the presence of up to four intercomponent hydrogen bonds between the amide groups of the macrocycle and various hydrogen bond accepting groups on the thread, including rare examples of amide-to-phosphinamide, -thiophosphinamide, and -selenophosphinamide groups. With a phosphine oxide-phosphinamide thread, the solid-state structure of the rotaxane is remarkable, featuring no direct intercomponent hydrogen bonds but rather a hydrogen bond network involving water molecules that bridge the H-bonding groups of the macrocycle and thread through bifurcated hydrogen bonds. The incorporation of phosphorus-based functional groups into rotaxanes may prove useful for the development of molecular shuttles in which the macrocycle can be used to hinder or expose binding ligating sites for metal-based catalysts.

The Reactivity of [PhP(Se)(μ‐Se)]2 and (PhP)3Se2 Towards Acetylenes and Cyanamides: X‐ray Crystal Structures of Some P‐Se‐C and P‐Se‐C‐N Heterocycles

Several unusual P-Se-C and P-Se-C-N heterocycles are formed by the reaction of [PhP(Se)(mu-Se)]2 or (PhP)3Se2 with alkynes or cyanamides, generated by the fragmentation of the organophosphorus-selenium compound and addition across the C identical to C or C identical to N triple bond of the organic substrate. X-ray crystallographic analysis reveals an unexpected diversity of structural motifs within these heterocyclic systems, including P2SeCN, P2C2Se and PC2Se2 rings.

Ruthenium(II) complexes of α-diimines: synthesis, spectral characterisation, electrochemical properties and single-crystal X-ray structure of bis(2,2′-bipyridine){1-benzyl-2-(p-tollylazo)imidazole}ruthenium(II) perchlorate

Abstract Mixed-ligand tris-chelates, [Ru(bpy)2(RaaiR′)](ClO4)2·H2O (bpy=2,2′-bipyridine; RaaiR′=1-alkyl-2-(arylazo)imidazole) have been synthesized by a silver-assisted route [Ru(bpy)2Cl2+RaaiR′+AgNO3+NaClO4/Ru(bpy)2Cl2+[Ag(RaaiR′)2](ClO4)]. The structures of the complexes have been supported by the single-crystal X-ray diffraction study and the stereochemistry are assessed by 1H NMR spectral data. All the complexes show two metal-to-ligand charge transfer (MLCT) transitions in the visible region at ca. 400 and 500 nm and their emission spectra are also described here. Cyclic voltammetric studies exhibit high-potential RuIII/II (1.4 V vs. SCE) and three successive ligand reductions at negative to SCE in acetonitrile solution. The difference in the first metal and successive ligand redox potentials are linearly correlated with the νCT of MLCT band.