Nick A. Giffin

Preparation of a diphosphine with persistent phosphinyl radical character in solution: characterization, reactivity with O2, S8, Se, Te, and P4, and electronic structure calculations.

A new, easily synthesized diphosphine based on a heterocyclic 1,3,2-diazaphospholidine framework has been prepared. Due to the large, sterically encumbering Dipp groups (Dipp = 2,6-diisopropylphenyl) on the heterocyclic ring, the diphosphine undergoes homolytic cleavage of the P-P bond in solution to form two phosphinyl radicals. The diphosphine has been reacted with O(2), S(8), Se, Te, and P(4), giving products that involve insertion of elements between the P-P bond to yield the related phosphinic acid anhydride, sulfide/disulfide, selenide, telluride, and a butterfly-type perphospha-bicyclobutadiene structure with a trans,trans-geometry. All molecules have been characterized by multinuclear NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Variable-temperature EPR spectroscopy was utilized to study the nature of the phosphinyl radical in solution. Electronic structure calculations were performed on a number of systems from the parent diphosphine [H(2)P](2) to amino-substituted [(H(2)N)(2)P](2) and cyclic amino-substituted [(H(2)C)(2)(NH)(2)P](2); then, bulky substituents (Ph or Dipp) were attached to the cyclic amino systems. Calculations on the isolated diphosphine at the B3LYP/6-31+G* level show that the homolytic cleavage of the P-P bond to form two phosphinyl radicals is favored over the diphosphine by ~11 kJ/mol. Furthermore, there is a significant amount of relaxation energy stored in the ligands (52.3 kJ/mol), providing a major driving force behind the homolytic cleavage of the central P-P bond.

Varsity athletes have lower 2D:4D ratios than other university students

Abstract The second to fourth digit ratio (2D:4D) is a sexually dimorphic trait with lower finger ratios considered more masculine. These digit ratios are believed to reflect the prenatal hormonal environment with higher exposure to androgens in utero leading to more masculine digit ratios. The 2D:4D ratio has been negatively correlated with many factors, including aggression, physical fitness, and athleticism. We compared 2D:4D finger ratios of (1) male and female varsity athletes (n = 99) versus male and female student non-athletes (n = 122), and (2) males (n = 104) versus females (n = 117). Our results confirmed that both male (mean ± sx : 0.97 ± 0.004) and female (0.98 ± 0.005) varsity athletes had significantly lower ratios than their non-varsity peers (males: 0.99 ± 0.004; females: 1.00 ± 0.006), and that male athletes had significantly lower 2D:4D ratios than female athletes. Overall, males had significantly lower 2D:4D ratios than females (0.98 ± 0.003 vs. 0.99 ± 0.004). A smaller 2D:4D ratio appears to be consistent with participation in varsity sports among both males and females.

Lewis Base Stabilized Oxophosphonium Ions

The rich functional group chemistry of phosphorus has been exploited over the last several decades and even as of late, there have been major advances to the field. There have been regular contributions to the area of N-heterocyclic phosphenium ions A since the first reports 30 years ago. The area has seen a recent resurgence 9–23] which may be due to the popularity of the isovalent singlet carbenes and, as such, the use of phosphenium ions as ligands in transition metal chemistry has been exploited. In the context of main group chemistry, phosphenium ions have been involved in the preparation of phosphinophosphonium systems, as well in reactions with P4, [39,41–44] and other reagents.

1,3-Bis(2,6-diisopropyl­phen­yl)imidazolidin-2-yl­idene

The title compound, C27H38N2, is the first reported free imidazolidin-2-ylidene carbene with 2,6-diisopropylphenyl groups in the 1,3-positions. The five-membered ring adopts a twisted conformation and the dihedral angle between the aromatic rings is 48.81 (6)°. Both isopropyl groups attached to one of the benzene rings are disordered over two sets of sites in 0.74 (2):0.26 (2) and 0.599 (8):0.401 (8) ratios.

1,3-Bis(2,6-diisopropyl-phen-yl)imidazolidinium tetra-phenyl-borate dichloro-methane disolvate.

The title compound, C27H39N2 +·C24H20B−·2CH2Cl2, is the first reported imidazolidinium cation with the sterically demanding 2,6-diisopropylphenyl groups in the 1,3-positions. The crystal structure is stabilized by weak intermolecular C—H⋯π(arene) interactions. Due to the bulky nature of both the flanking 2,6-diisopropylphenyl substituents and the tetraphenylborate counter-ion, anion interactions with the imidazolidinium H atom in the 2-position are not observed, also a first for this class of ortho-alkyl-substituted Arduengo-type carbene precursors.

Reaction of sterically encumbered phenols, TEMPO-H, and organocarbonyl insertion reactions with L-AlH2 (L = HC(MeCNDipp)2, Dipp = 2,6-diisopropylphenyl)

The reaction of L-AlH2 (L = HC(MeCNDipp)2, Dipp = 2,6-diisopropylphenyl) with sterically bulky phenols (2,4,6-trimethylphenol, MesOH; 2,6-diisopropylphenol, DippOH) and an N-hydroxylamine (1-hydroxy-2,2,6,6-tetramethyl-piperidine, TEMPO-H) forms an Al–O bond with concomitant loss of hydrogen gas to give L-Al(H)OMes, L-Al(H)ODipp and L-Al(H)TEMPO, respectively. Reaction with 1 or 2 equivalents of benzaldehyde or 1 equivalent of benzophenone results in insertion of carbonyl into the Al–H bond(s) to give the related benzylate and diphenylmethoxide products. Compounds L-Al(H)OMes, L-Al(H)ODipp, L-Al(H)TEMPO, L-Al(H)OBn, L-Al(OBn)2, and L-Al(H)OCHPh2 have been characterized by NMR spectroscopy, elemental analysis, infrared spectroscopy and single crystal X-ray diffraction. The reaction of L-Al(H)OBn with pinacol borane gives a complex mixture of unidentifiable products, providing evidence of the importance of the triflate group in the known aldehyde and ketone hydroboration catalyst L-Al(H)OTf (OTf = CF3SO3−).

A new polymorph of 2,6-bis­(trifluoro­meth­yl)benzoic acid

The asymmetric unit of a second polymorph of the title compound, C9H4F6O2, contains five independent molecules, which form hydrogen-bonded O—H⋯O dimers about inversion centers. The most significant structural difference between this structure and that of the first polymorph [Tobin & Masuda (2009 ▶). Acta Cryst. E65, o1217] is the hydrogen-bonded, dimeric orientation of the carboxylic acid functionalities.

Crystal Structure of Bis(2,4,6-trimethylphenyl)-phosphine Oxide

The single crystal structure of bis(2,4,6-trimethylphenyl)phosphine oxide has been determined. All interatomic distances and angles can be considered normal. The aryl substituents adopt an intermediate configuration when compared to both sterically unhindered (e.g., diphenylphosphine oxide) and congested (e.g., bis(2,4,6-tri-tert-butylphenyl)phosphine oxide) secondary phosphine oxides, illustrating the influence of steric congestion on the molecular structure.