Contents 1. Introduction 4236 2. The Stability of P 4 Phosphorus with Respect to Its Allotropes and Neutral Polyphosphorus Species 4237 2.1. Allotropic Modifications of Phosphorus 4237 2.2. Stability of Neutral Polyphosphorus Species 4238 3. General Trends of P 4 Phosphorus Activation 4239 3.1. General Remarks 4239 3.2. Degradation of P 4 Phosphorus by Nucleophiles under Maintenance of P n Structural Moieties 4241 4. Activation and Degradation of P 4 Phosphorus by Main Group Elements and Compounds 4243 4.1. Activation of P 4 Phosphorus by Group 1 and 2 Elements and Compounds 4243 4.2. Activation of P 4 Phosphorus by Group 13 Element Compounds 4245 4.3. Activation and Degradation of P 4 Phosphorus by Group 14 Element Compounds 4246 4.4. Activation and Degradation of P 4 Phosphorus by Group 15 Element Compounds 4250 4.5. Activation and Degradation of P 4 Phosphorus by Group 16 and 17 Element Compounds 4251 5. Abbreviations 4252 6. Acknowledgments 4253 7. References 4253

Since the discovery of the first "inorganic benzene" (borazine, B3N3H6), the synthesis of other noncarbon derivatives is an ongoing challenge in Inorganic Chemistry. Here we report on the synthesis of the first pnictogen-silicon congeners of benzene, the triarsa- and the triphospha-trisilabenzene [(PhC(NtBu)2)3Si3E3] (E = P (1a), As (1b)) by a simple metathesis reaction. These compounds are formed by the reaction of [Cp″2Zr(η(1:1)-E4)] (E = P, As; Cp″ = C5H3tBu2) with [PhC(NtBu)2SiCl] in toluene at room temperature along with the silicon pnictogen congeners of the cyclobutadiene, [(PhC(NtBu)2)2Si2E2] (E = P (2a), As (2b)), which is unprecedented for the arsenic system 2b. All compounds were comprehensively characterized, and density functional theory calculations were performed to verify the stability and the aromatic character of the triarsa- and the triphospha-trisilabenzene.

Psoriatic onycho-pachydermo periostitis (POPP) is recognized as a rare subset of psoriatic arthritis, characterized by psoriatic onychodystrophy, connective tissue thickening above the distal phalanx, and a periosteal reaction. Therapy for this rare disease is based on treatments used for psoriatic arthritis, but traditional disease-modifying antirheumatic drugs, such as sulfasalazine and methotrexate, have shown inconsistent and unsatisfactory results. We report herein a successful therapeutic approach for POPP using the fully human anti-tumor necrosis factor (TNF) antibody adalimumab in a 42-year-old male patient. After 4 months of anti-TNF treatment, a remarkable normalization of the clinical appearance was achieved and magnetic resonance imaging showed complete resolution of the initial inflammatory lesions. Therefore, we consider a TNF-blocking strategy as promising for treatment of POPP.Psoriatic onycho-pachydermo periostitis (POPP) is a recently described entity that consists of psoriatic onychodystrophy and connective tissue thickening above the distal phalanx, including a periosteal reaction (1). Together, these lesions result in a typical drumstick-like deformity of the digits. POPP can be extremely painful and frequently causes significant functional impairment. It has been recognized as an uncommon subset of psoriatic arthritis and, to date, only 15 cases have been described worldwide (1-12). Therapy for this rare disease is based on experiences with treatment of psoriatic arthritis but, according to the few published case reports, nonsteroidal antiinflammatory drugs and sulfasalazine showed inconsistent and unsatisfactory results (1-3). Methotrexate provided some benefit in only 3 reported cases (4,5,9). In this report, we describe the successful treatment of POPP using adalimumab, fully human monoclonal antibody that blocks tumor necrosis factor (TNF). CASE REPORTThe patient, a 42-year-old man, had an 18-month history of painful swelling and onycholysis that affected all toes. Additionally, he had experienced inflammatory back pain for the last 6 months and intermittent pain in the right knee. His general medical history was unremarkable and there was no sign of intestinal or urogenital infection. As a metal worker who had to wear safety boots, the patient was severely affected by the painful lesions of his toes and was unable to perform his duties at that time.Physical examination revealed tender, drumsticklike swelling of all toes. The toenails exhibited severe onycholysis with subungual debris ( Figure 1A). Erythematous, hyperkeratotic plaque with hemorrhagic pustules was seen on the soles of both feet. In addition, the right sternoclavicular joint and both sacroiliac joints were tender and Mennell's sign was positive bilaterally.Laboratory investigations showed an erythrocyte sedimentation rate of 16 mm/hour, a mildly elevated C-reactive protein level of 6.4 mg/liter, a gamma glutamyl transferase level of 30 units/liter, and an alkaline phosphatase level of 220 units/liter. HLA-B27 was positive...

The cothermolysis of As and [Cp″Zr(CO)] (Cp″ = η-CHtBu) results in the formation of [Cp″Zr(η-As)] (1) in high yields and the arsenic-rich complex [(Cp″Zr)(Cp″Zr)(μ,η-As)] (2) as a minor product. In contrast to yellow arsenic, 1 is a light-stable, weighable and storable arsenic source for subsequent reactions. The transfer reaction of 1 with [Cp‴Fe(μ-Br)] (Cp‴ = η-CHtBu) yields the unprecedented bond isomeric complexes [(Cp‴Fe)(μ,η-As)] (3a) and [(Cp‴Fe)(μ,η-cyclo-As)] (3b). In contrast, the analogous reaction with the Cp derivative [CpFe(μ-Br)] (Cp = η-C(CH(CH)) leads exclusively to the triple decker complex [(CpFe)(μ,η-As)] (4) possessing the tetraarsabutadiene-type ligand analogous to 3a. To elucidate the stability of the bonding isomers 3a and 3b, DFT calculations were performed. The oxidation of 4 with AgBF affords [(CpFe)(μ,η-As)][BF] (5), which is a product expanded by one arsenic atom, instead of the expected complex [(CpFe)(μ,η-cyclo-As)].

The storage of metastable compounds and modifications of elements are of great interest for synthesis and other, e.g., semiconductor, applications. Whereas white phosphorus is a metastable modification that can be stored under certain conditions, storage of the extremely (light- and air-)sensitive form of arsenic, yellow arsenic, is a challenge rarely tackled so far. Herein, we report on the facile storage and release of these tetrahedral E4 molecules (E = P, As) using activated carbon as a porous storage material. These loaded materials are air- and light-stable and have been comprehensively characterized by solid-state 31P{1H} MAS NMR spectroscopy, powder X-ray diffraction analysis, nitrogen adsorption measurements, and thermogravimetric analysis. Additionally, we show that these materials can be used as a suitable E4 source for releasing intact white phosphorus or yellow arsenic, enabling subsequent reactions in solution. Because the uptake and release of E4 are reversible, these materials are excellent carriers of these highly reactive modifications.

The activation of yellow arsenic is possible with the silylene [PhC(NtBu) SiN(SiMe ) ] (1) and the disilene [(Me Si) N(η -Me C )Si=Si(η -Me C )N(SiMe ) ] (3). The reaction of As with 1 leads to the unprecedented As cage compound [(LSiN(SiMe ) ) As ] (2; L=PhC(NtBu) ) with an As nortricyclane core stabilized by arsasilene moieties containing silicon(II)bis(trimethylsilyl)amide substituents. In contrast, the compound [Cp*{(SiMe ) N}SiAs] (4) containing a butterfly-like diarsadisilabicyclo[1.1.0]butane unit is formed by the reaction of As with the disilene 3. Both compounds were characterized by single-crystal X-ray diffraction analysis, NMR spectroscopy, and mass spectrometry. The reaction outcomes demonstrate the different reaction behavior of yellow arsenic (As ) compared to white phosphorus (P ) in the reactions with the corresponding silylenes and disilenes.

A detailed method for the preparation of [Cp'' Zr(η -P )] (1) is presented. The coordination behavior of 1 towards Lewis acidic transition metal complexes of tungsten, manganese, and iron, respectively, and main group compounds (AlMe , AlEt ) was investigated in detail by computational and experimental studies. In doing so, a series of unprecedented complexes with different coordination modes and multiple coordination numbers of the tetraphosphabicyclo[1.1.0]butane framework were synthesized. All products, as well as the starting materials, were comprehensively characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single crystal X-ray structural analysis.

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