Several levels of density functional theory, i.e., various combinations of exchange-correlation functionals and basis sets, have been employed to compute equilibrium geometries for a diverse set of 32 metal complexes from the first transition row, for which precise gas-phase geometries are known from electron diffraction or microwave spectroscopy. Most DFT levels beyond the local density approximation can reproduce the 50 metal−ligand bond distances selected in this set with reasonable accuracy, as assessed by mean and standard deviations of optimized vs observed values. The ranking of some popular functionals, ordered according to decreasing standard deviation, is BLYP ≈ HCTH > B3LYP > BP86 > TPSS ≈ TPSSh. Together with its hybrid variant, the recently introduced meta-GGA functional TPSS performs best of all tested functionals, with mean and standard deviations of −0.5 and 1.4 pm, respectively. Even smaller errors are found for a more compact but less diverse set of transition-metal mono- and dihalides, ...

Geometries of Transition-Metal Complexes from Density-Functional Theory

The coordination chemistry of white phosphorus is nowadays a mature discipline, which during the last four decades has reached a deep understanding of the mechanisms governing the metal-mediated activation of this unique and highly reactive molecule. The birth certificate of this story dates back to 1970 when the synthesis of [RhCl(PPh3)2(η-P4)] together with other rhodium and iridium species was reported by Ginsberg and Lindsell as a short communication in Transactions of the New York Academy of Sciences.1,2 Immediately, this seminal discovery motivated intense research activity worldwide. Worth mentioning among the pioneers in this area are the groups led by Markó in Veszprem, Hungary; Dahl in Madison, Wisconsin, U.S.A.; and Sacconi in Florence, Italy. While the first two demonstrated that fragments deriving from P4 degradation could be stabilized as ligands in the coordination sphere of cobalt carbonyl3 and cyclopentadienyl derivatives,4 Sacconi first succeeded in coordinating the intact tetrahedral P4 molecule to a metal,5 obtaining the Ni(0) complex [(κ-P,P,P-NP3)Ni(ηP4)], and in fully characterizing a vast family of cyclo-P3 late transition metal derivatives spanning from iron to osmium.6 In the following decade, the development of the isolobal concept7 and its application to organometallic and main group chemistry paved the way to the synthesis of an incredible variety of polyphosphorus architectures where CH, CH2, and CH3 fragments in acyclic and cyclic hydrocarbons could be formally replaced by naked P atoms and substituted PH and PH2 units, respectively. Spectacular examples of organometallic phosphorus topologies ruled by the isolobal relationship can be found in the systematic work done in Kaiserslautern by Scherer and his co-workers who applied the isolobal P T C-H relation to the synthesis of a myriad of polycyclic phosphorus species mimicking benzene and other arenes. Landmarks in this area were the discovery of the cyclo-P6 ligand stabilized as internal layer in the triple-decker dimolybdenum complex [{Cp*Mo}2(μ,η-P6)] and the pentaphosphaferrocene derivative [{Cp*Fe}(η-P5)]. These species, within the loose boundaries of the isolobal concept, may be considered as the all-phosphorus analogues of benzene and cyclopentadienyl anion, respectively. The intriguing analogy between hydrocarbon species and organophosphorus compounds has been reviewed in the successful book “Phosphorus: The Carbon Copy” published by Wiley in 1998.10 In the last two decades, several reviews have also appeared covering different aspects of transition metalmediated white phosphorus activation. These include specific surveys addressing the formation of P-H11 and P-C species12 as well as some general reviews targeting the synthesis and the characterization of transition metal complexes incorporating naked phosphorus atoms and units as ligands.13-17 The importance of studying the coordination chemistry of elemental phosphorus by late (and early) transition metal complexes also stems from the need to replace the current technology for the production of organophosphorus derivatives. This reaction, which is of great industrial relevance, is still based on the chlorination of white phosphorus followed by the reaction of PCl3, PCl5, or POCl3 with the † This contribution is dedicated to our colleague and friend Prof. Piero Stoppioni on occasion of his 65th birthday and in recognition of his outstanding achievements in the field of white phosphorus activation. ‡ Note: In figures showing X-ray crystal structures, H atoms are generally omitted for clarity unless specified. * To whom correspondence should be addressed. E-mail: mperuzzini@ iccom.cnr.it. Chem. Rev. 2010, 110, 4178–4235 4178

P4 Activation by Late-Transition Metal Complexes†‡

Aromaticity of phosphorus heterocycles.

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.

O. J. Scherer

Papers

The Gas-Phase Structure of P5Fe(C5Me5) from Electron Diffraction.

The Gas-Phase Structure of P5Fe(C5Me5) from Electron Diffraction.

((η5-P5)Fe(η5-C5Me5)), a Pentaphosphaferrocene Derivative.