Syntheses, properties, and reactivities of nucleophilic phosphinidene complexes [L(n)M=P-R] are reviewed. Emphasis is placed on the electronic tuning of this emerging class of phosphorus reagents, using different ancillary ligands and coordinatively unsaturated transition-metal moieties. The difference in applicability of the established stable 18-electron and transient 16-electron phosphinidenes is addressed.

Novel terminal rhodium-and cobalt-complexed phosphinidenes, Cp*(PR 3 ) and Cp(PPh 3 )CodPAr (8), were obtained by dehydrohalogenation of the primary phosphine complexes Cp*RhCl 2 (PH 2 Ar) (2) and CpCoI 2 (PH 2 Ar) (7) in the presence of a phosphine. X-ray crystal structures are reported for Cp*(PPh 3 )RhdPMes* (3) and Cp(PPh 3 )CodPMes* (8). A comparative reactivity study and a computational survey were performed on the Co-, Rh-, and Ir-containing phosphinidene complexes. All react with organic dihalides to form phosphaalkenes, with the rhodium congener being far more reactive than the iridium and cobalt complexes. Density functional theory calculations give geometrical parameters and 31 P NMR chemical shifts in good agreement with experimental data. The rhodium congeners exhibit the most pronounced charge separation of the RhdP bond, which may explain its higher reactivity. The M-L bond is strong in all Cp(L)MdPH (M ) Co, Rh, Ir) complexes and inhibits reactivity at the metal center. Comparisons with the Zr-containing complex Cp 2 (PH 3 )Zr-PH are made.

Catalyst tuning by changing ligands is a well-established protocol in transition-metal chemistry. N-Heterocyclic carbenes (NHCs) and tertiary phosphines (R(3)P) are the ubiquitous ligand actors. Here we demonstrate that the relative sigma-donor/pi-acceptor ability of the NHC ligand itself can be influenced by a simple substituent-controlled conformational change, thereby directly impacting the reactivity of the transition-metal complex.

The N-heterocyclic carbene (NHC) functionalized phosphinidene complexes [(pCy)(I i Pr2Me2)RuPMes*] (4), [(pCy)(I i Pr2Me2)OsPMes*] (6), and [(Cp*)(I i Pr2Me2)RhPMes*] (7) were generated by a double-dehydrohalogenation−ligation sequence of the corresponding primary phosphine complexes with 3 equiv of NHC. The effect of the NHC ligand on the electronic properties of the phosphinidene complexes [(Ring)(NHC)MPH] (8−16), bearing group 7−9 transition metals and cycloheptatrienyl (Cht+), benzene, and cyclopentadienyl (Cp−) as ancillary ligands, was studied by density functional theory. All ligand−M bond energy strengths increase with the order of the transition metal in the periodic table. The metal−carbene bond (M−NHC) is dominated by σ-interaction from the ligand, but the π-interaction is substantial, contributing up to ∼20% of the total orbital interaction arising from metal to ligand π-back-donation. The charged ligands Cht+ and Cp− have notable effects on the total σ- and π-interactions in the M−NHC bond. On going to the right in the periodic table, the structures show an increase in M−NHC bond energy that concurs with the net charge on the phosphorus atom of the MP bond.

18-Electron nucleophilic, Schrock-type phosphinidene complexes 3 [Cp*(Xy-N[triple bond]C)Ir=PAr] (Ar = Mes*, Dmp, Mes) are capable of unprecedented [1 + 2]-cycloadditions with 1 equiv of isocyanide RNC (R = Xy, Ph) to give novel iridaphosphirane complexes [Cp*(Xy-N[triple bond]C) IrPAr C=NR]. Their structures were ascertained by X-ray diffraction. Density functional theory investigations on model structures revealed that the iridaphosphirane complexes are formed from the addition of the isocyanide to 16-electron species [Cp*Ir=PAr] forming first complex 3 that subsequently reacts with another isocyanide to give the products following a different pathway than its nitrogen analogue [Cp*Ir[triple bond]Nt-Bu] 1.

Ein bewegliches Molekül: Die Umsetzung von in situ erzeugten Phosphinidenen mit Phosphaalkinen eröffnet einen einfachen Zugang zum neuen metallkoordinierten η3‐Diphosphavinylcarben 1, das leicht Ligandenaustauschreaktionen und eine neuartige Umlagerung eingeht, an welcher der Phosphinidenkomplex 2 und der η3‐Phosphaalkenylphosphinidenkomplex 3, das 1,3‐Isomer von 1, beteiligt sind.magnified image

Dieser Kurzaufsatz gibt einen Überblick über die Synthese, Eigenschaften und Reaktivitäten nucleophiler Phosphinidenkomplexe, [LnMPR]. Ein Schwerpunkt liegt auf Methoden zur Feinabstimmung der elektronischen Eigenschaften dieser neuen Klasse von Phosphorreagentien mithilfe verschiedener Hilfsliganden und koordinativ ungesättigter Übergangsmetallfragmente. Zudem richten wir unser Augenmerk auf die charakteristischen Unterschiede in der Anwendbarkeit der stabilen 18‐Elektronen‐Phosphinidene und der kurzlebigen 16‐Elektronen‐Phosphinidene.

The synthesis of 3′‐deoxyribolactones was accomplished in a few steps from the commercially available 3‐decyn‐1‐ol in 44 % overall yield. The key transformation comprises a one‐pot four‐reaction hydrolysis‐induced lactonization cascade. The strategy was employed to efficiently access optically active 5′‐chloro‐3′‐deoxyribolactones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)