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†‡

Unter Phosphor-, Arsen-, Antimon- und Bismutliganden verstand man bis vor kurzem fast ausschlieslich Verbindungen wie R3E, R2E(CH2)nER2 und RC[(CH2)nER2]3 (E = P,As,Sb,Bi), deren freies Elektronenpaar am E-Atom als 2e-Donor fungiert. Das Forschungsinteresse gilt aber zunehmend den substituentenfreien En-Liganden (n = 1-6), die bevorzugt aus EX3(X = F,Cl,Br,Ph), E(SiMe3)3, (RAs)n, P4S3, As4S4, grauem Arsen und vor allem P4 und As4 erhaltlich sind und die in Gegenwart bestimmter Ubergangsmetallkomplexfragmente koordinativ stabilisiert werden konnen. In Zwei- und Dreikernkomplexen mit P1-, As1- und Sb1-Liganden treten M-E-Mehrfachbindungsanteile auf. E-Atome konnen aber auch teilweise oder vollstandig in Hohlraumen der unterschiedlichsten Metallcluster eingeschlossen sein. Besonders haufig entstehen Metallatetrahedrane mit bis zu drei E-Atomen. Die mit Abstand groste Koordinationsvielfalt weisen neben den E1 - die E4-Liganden auf, denen man sowohl in Form intakter Tetraeder als auch als Bestandteile von Ketten, Polycyclen, Wurfeln und eines trigonalen Prismas begegnet. Die zu den carbocyclischen (CH)n-π-Systemen isoelektronischen Phosphor- und Arsenanaloga cyclo-En eignen sich als Liganden fur Sandwich- (n = 3,4,5) und Tripeldeckerkomplexe (n = 3,5,6). Nicht zuletzt sind diese Verbindungen aufgrund ihrer Reaktivitat und der Parallelen zur Organischen Chemie und Festkorperchemie bei Chemikern verschiedener Disziplinen auf reges Interesse gestosen.

Komplexe mit substituentenfreien acyclischen und cyclischen Phosphor‐, Arsen‐, Antimon‐ und Bismutliganden

Main Group–Transition Metal Cluster Compounds of the Group 15 Elements

Polyhedron report number 19

Isolierbare sowie am Metallzentrum erzeugte niederkoordinierte (Koordinationszahl eins bis drei) Mehrfachbindungssysteme des Phosphors und seiner Homologen sind vielseitige Liganden. Sie konnen an Ubergangsmetallfragmenten als 2e-, 4e-, 6e- und 8e-Donor-Liganden fungieren und terminal(ν1), side-on(ν2), kanten- und/oder flachenuberbruckend an das (die) Metallatom(e) koordiniert sein. Das vielfach noch vorhandene (p-p)π-Bindungssystem der Liganden ist zu Additionen und intra- oder intermolekularen Cycloadditionen befahigt. Einige der dabei gebildeten Polycyclen sind neuartige, mehrzahnige Ligandensysteme.

Dipl.-Chem. Dieter Binder

Papers

Chelate‐Stabilized Diphosphene and Diphosphorus Complexes of Nickel