Terminal Phosphinidene Complexes Cp^R(L)MPAr of the Group 9 Transition Metals Cobalt, Rhodium, and Iridium. Synthesis, Structures, and Properties

Abstract

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.

N‐Heterocyclic Carbene Functionalized Iridium Phosphinidene Complex [Cp*(NHC)IrPMes*]: Comparison of Phosphinidene, Imido, and Carbene Complexes

“…The metal ± ligand BDE for 4 strongly resembles that of previously reported IrÀCO bonds in similar phosphinidene complexes, [Cp(CO)IrPH]. [10] However, the IrÀCO bond length is much shorter (1. . Again, the diagonal C ± P relationship [15] in the Periodic Table is stressed, whereas the vertical N ± P relationship is much less pronounced.…”

“…[9,10] A unique aspect of these novel complexes concerns the facile variation of stabilizing ligand L. So far, established ligands such as phosphines, arsines, phosphites, isocyanides and carbon monoxide have been introduced successfully, leading to stable, isolable complexes with strong metalÀligand bonds. [10] This encouraged us to investigate the availability of phosphinidene complexes that contain an N-heterocyclic carbene ligand, and to study their structural and electronic properties.…”

Synthesis and Structural Characterization of the First Thermally Stable, Neutral, and Electrophilic Phosphinidene Complexes of Vanadium

“…39 Such reactions parallel the properties of transient electrophilic phosphinidenes [(CO) 5 WdPR] as demonstrated by Mathey. 36 Theoretical (DFT) studies of terminal phosphinidene complexes have shown that the character (nucleophilic, electrophilic) of the phosphinidene fragment can be influenced by the metal fragment, particularly the donor or acceptor properties of the ligands and the substituents on the phosphorus atom.…”

“…They are thermally stable, despite in some notable cases, such as the Re and Co compounds, the lack of sterically encumbered substituents on the metal or phosphorus ligand. The thermal stability of [Re(CO) 5 -{P(N i Pr 2 )}} þ compared to the reported instability of the isoelectronic [W(CO) 5 (PR)] is particularly notable. Clearly it would seem that electronic factors, including the presence of donor substituents on the nonmetal, are responsible for the enhanced stability of the Re cation.…”

“…þ , and the phosphaorganic chemistry of transient electrophilic phosphinidenes such as [(CO) 5 WdPR] and [(CO) 4 FedPR)],generatedinsitu,hadbeen e l e g a n t l ye x p l o r e db yM a t h e y 36 and co-workers and Lammertsma et al 37 The Lammertsma group has recently reported the direct observation of the phosphinidene complex [W(CO) 5 (η 1 -PAr)] (Ar = aryl) by electrospray ionization tandem mass spectrometry (ESI-MS/MS), and the chemistry displayed by this reactive species matches that observed in solution. 38 Over the past few years we have isolated a series of cationic, terminal complexes including the remaining member [Cp*Cr(CO) 3 -{PN 21,[23][24][25]34 These molecules, all of which have been structurally characterized, display several important features.…”