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

The reaction of [Cp*Fe(eta5-P5)] with Cu(I)Cl in solvent mixtures of CH2Cl2/CH3CN leads to the formation of entirely inorganic fullerene-like molecules of the formula [[Cp*Fe(eta5:eta1:eta1:eta1:eta1:eta1-P5)]12[CuCl]10[Cu2Cl3]5[Cu(CH3CN)2]5] (1) possessing 90 inorganic core atoms. This compound represents a structural motif similar to that of C60: cyclo-P5 rings of [Cp*Fe(eta5-P5)] molecules are surrounded by six-membered P4Cu2 rings that result from the coordination of each of the phosphorus lone pairs to CuCl metal centers, which are further coordinated by P atoms of other cyclo-P5 rings. Thus, five- and six-membered rings alternate in a manner comparable to that observed in the fullerene molecules. The so-formed half shells are joined by [Cu2Cl3]- as well as by [Cu(CH3CN)2]+ units. The spherical body has an inside diameter of 1.25 nanometers and an outside diameter of 2.13 nanometers, which is about three times as large as that of C60.

Terminal metal phosphinidene complexes (L n M = PR) are, despite continued interest, far less developed than their isolobal metal imide and alkylidene counterparts.[1] Although the first L n M=PR complex was reported over a quarter of a century ago, [2] sterically demanding R-groups are required, as M=PR linkages are reactive and require kinetic stabilization.[3] Certainly, free phosphinidenes (PR) are usually very reactive owing to their triplet ground states and unsaturated valence shells.[4] Although stabilization of a triplet PR group by a triplet metal fragment to generate a formal M=P bond is an attractive strategy, unlike the well-known L n M=NH and L n M=CH 2 linkages, [5] there has never been a structurally authenticated report of a d-/f-block metal-stabilized terminal parent phosphinidene L n M = PH, [6,7] and studies of such species are limited to computational investigations. [8] This paucity is underscored by a triplet-singlet energy gap of 22 kcal mol À1 for free PH, [4b] which has only been observed transiently in the gas phase or low temperature matrices. [4a, 9]