Bridging phosphanes

Coordination Chemistry of 2,5-(2-Pyridyl)phosphole Derivatives Complexes Bearing Bridging Phosphane Ligands and Coordination-driven Supramolecular Organization of -Conjugated Chromophores... 

Bimetallic Coordination Complexes Bearing a Bridging Phosphane Ligand... 

In comparison to the other 2-(2-pyridyl)-phosphole P,N-ligands 3c-f, 2,5-bis(2-pyridyl)-phosphole ligand 3b revealed a very original coordination chemistry toward Pd(I), Pt(I), and Cu(I) metal centers. A family of coordination complexes exhibiting a bridging phosphane coordination mode was thus evidenced, a very rare coordination mode for such a commonly used family of ligands. 

In an attempt to generalize this original bridging phosphane coordination mode to other metal ions, we have investigated the coordination chemistry of ligand 3b with Cu(I) salts [29]. Thus, reaction of di(2-pyridyl)phosphole 3b with Cu(CH3CN)4PF(l in a 1 2 ratio afforded quantitatively the dimetallated complex 15 (Scheme 12.9). 

Leca F, Lescop C, Rodriguez E, Costuas K, Halet JF, R6au R (2005) Bridging phosphanes exotic or versatile binucleating ligands Angew Chem Int Ed 44 4362... 

Nohra B, Rodriguez-Sanz E, Lescop C, Reau R (2008) Chemistry of bridging phosphanes Cu-I dimers bearing 2,5-bis(2-pyridyl)phosphole ligands. Chem Eur J 14 3391... 

Leca F, Sauthier M, Deborde V, Toupet L, Reau R (2003) Chemistry of bridging phosphanes Pd-1 dimers bearing 2,5-dipyridylphosphole ligands. Chem Eur J 9 3785... 

Welsch S, Nohra B, Peresypkina EV, Lescop C, Scheer M, R au R (2009) Chemistry of bridging phosphanes a comparative study within Cu-I-Ag-I-Au-I triad-based homonuclear dimers. Chem Eur J 15 4685... 

Trifluorophosphane can behave as a /x3 donor towards a triangular palladium core.559,360 The symmetrically bridging / -coordination mode has little precedent for tertiary ligands based on Group 15 atoms. The synthesis of a Pd1 dimer featuring a strongly bonded symmetrically bridging /i2-phosphole unit, which is the first example of this coordination mode for a tertiary phosphane, has been reported.561... 

In the group of Izod, the tris(phosphane oxide) 19 was 1,2-dilithiated by the reaction with two equivalents of w-butyllithium in THF at room temperature (Scheme 7). The similarity of the structural formula of compound 20 (Lewis formula) to 1,2-dilithium compounds found by Sekiguchi and coworkers (see Section n. E), where two lithium centres are bridging a C2 unit, is not maintained in the solid state. The X-ray structural analysis reveals a centrosymmetric dimer containing no carbon-lithium contacts (Figure 8). 

When phosphaalkynes are exposed to bis- and tris(diazo) compounds, bis- or tris(l,2,4-diazaphosphol-5-yl) compounds are formed that may be further converted into a variety of novel heterocyclic systems. For example, bis- and tris[diazo(tri-methylsilyl)methyl]phosphanes 237 and 240 afforded bis- and tris(diazaphospho-lyl)phosphanes 238 and 241 after cycloaddition with terf-butylphosphaacetylene followed by a subsequent 1,5-silyl shift (Scheme 8.56) (300). Reaction with electrophilic halides at the Wsilyl functions allows the introduction of a heteroatom bridge between the diazaphosphole ring leading to polycyclic ring systems such as 239 and 242. 

With 1,1-difluorocyclopropabenzene and a range of nickel(O) complexes, nickelabicy-clobutanes 118 (84—93%) are formed by loss of olefin or phosphane ligands and addition of the nickel atom across the bridge bond (Scheme 20)256-266. The products appear to be stable at ambient temperatures but are oxygen sensitive the majority revert to cycloproparene in solution even below -20 °C. With (j -allyl)( s-cyclopentadienyl(palladium in the... 

Finally, there are two examples of intramolecular C,P chelates, viz. LPd k2-C,P-2-CH2C6H4P(o-To1)2 (L = Tp 468, Bp 469), both prepared by cleavage of the halide bridged dimer with KL (Scheme 46). 43 These complexes were targeted to explore their potential in the guise of catalysts for organic synthesis, a role to which the cyclopalladated tris(o-tolyl) phosphane precursor had been previously applied. However, this preliminary study revealed these materials to be unreactive toward electrophiles (see also Section III.C.3.b), and no further investigations have been reported. 

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