The trans-influence: its measurement and significance

Coordination chemistry and catalysis with hemilabile oxygen-phosphorus ligands

Ni2p3/2 X-ray photoelectron spectral peak binding energies of Ni metal, NiS, and NiAs (all conductors) span a range of about 0.5 eV and are, consequently, insensitive to formal Ni oxidation state and to the nature of the ligand to which Ni is bonded, relative to other metals (e.g., Fe). Ni2p3/2 peak structures and binding energies reflect two energetic contributions. The major contribution is that associated with the electrostatic field produced by ejection of the Ni(2p) photoelectron, the minor contribution is the relaxation energy associated with filling unoccupied, conduction band 3d9 and 4s Ni metal orbitals. These conduction band orbitals become localized on the Ni photoion (and sometimes filled) in response to the field created by the photoemission event. Because only the core Ni2p electron and nonbonding orbitals of predominantly metallic character are affected, the main peak of all three conductors are affected similarly, leading to similar Ni2p3/2 main peak binding energies. NiO, Ni(OH)2, and NiSO4 are insulators in which Ni is divalent and is bonded to oxygen. Although Ni is bonded to oxide in these phases, Ni2p binding energies differ substantially, and reflect primarily the nature of the ligand (O2−, OH−, SO4
2−) to which Ni is bonded. The influence of the ligand is the result of charge (electron) transfer from valence band bonding orbitals of dominantly ligand character, to unoccupied conduction band orbitals localized on Ni photoions. Relaxation energy resulting from charge transfer is acquired by the emitted photoelectron, thus Ni2p3/2 photopeak binding energies of these insulators reflect the nature of the ligand to which Ni is bonded. The Ni2p main peak binding energy of these conductors and insulators is a poor guide to Ni oxidation states. The Ni2p3/2 binding energies of insulators reflect, however, the nature of the ligand in the first coordination sphere of Ni. The intensity of the Doniach–Sunjic contribution to Ni2p XPS spectra of NiS and NiAs is dependent on the nature of the ligand. The Doniach–Sunjic contribution to ligand XPS core-level photopeaks (e.g., S2p of NiS and As3d of NiAs) has not been explained and is poorly understood.

Interpretation of Ni2p XPS spectra of Ni conductors and Ni insulators

Trans-effects in octahedral transition metal complexes

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†‡

Phosphorus-31 nuclear magnetic resonance study of tertiary phosphine derivatives of Group VI metal carbonyls

A phosphorus-31 nuclear magnetic resonance study of tertiary phosphine complexes of platinum(II)

X-ray photoelectron spectroscopy of inorganic and organometallic compounds of molybdenum

Unsymmetrical bis-phosphorus ligands. IV. Group VI metal carbonyl derivatives of diphenylphosphinomethyl and diphenylphosphinomethyl phosphinites, (C6H5)2P(CH2)nOP(C6H5)2, n = 1 or 2, and an unusual phosphorus chemical shift chelate effect

Crystal and molecular structures of pentacarbonyltriphenylphosphinechromium(0) and pentacarbonyl(triphenyl phosphite)chromium(0)

Samuel O. Grim

Papers

Phosphorus-31 nuclear magnetic resonance study of tertiary phosphine derivatives of Group VI metal carbonyls

A phosphorus-31 nuclear magnetic resonance study of tertiary phosphine complexes of platinum(II)

X-ray photoelectron spectroscopy of inorganic and organometallic compounds of molybdenum

Unsymmetrical bis-phosphorus ligands. IV. Group VI metal carbonyl derivatives of diphenylphosphinomethyl and diphenylphosphinomethyl phosphinites, (C6H5)2P(CH2)nOP(C6H5)2, n = 1 or 2, and an unusual phosphorus chemical shift chelate effect

Crystal and molecular structures of pentacarbonyltriphenylphosphinechromium(0) and pentacarbonyl(triphenyl phosphite)chromium(0)