Transition Metal Complexes of Phosphinous Acids Featuring a Quasichelating Unit: Synthesis, Characterization, and Hetero-bimetallic Complexes

Diorganophosphane
oxides were employed as preligands for the synthesis of catalytically
active transition metal complexes of the phosphinous acids (CF3)2POH and (C2F5)2POH. Their reactions with solid PtCl2 and PdCl2 led to the formation of mononuclear phosphinous acid complexes [Cl2M­{P­(Rf)2OH}2] (M =
Pd, Pt; Rf = C2F5, CF3), which can be crystallized, for example, as its pyridinium salts,
2­[HPy]+[Cl2Pd­{P­(CF3)2O}2]2–. In vacuo HCl is liberated from
the neutral palladium complexes affording mixtures of di- and polynuclear
complexes. Moreover, (C2F5)2POH was
reacted with several β-diketonato complexes of palladium, platinum,
and nickel yielding air- and moisture-stable complexes [(acac)­M­{[P­(Rf)2O]2H}], featuring a quasichelating
phosphinous acid phosphinito unit {P­(Rf)2O···H···O­(Rf)2P}−. Treatment of [Ni­(Cp)2] (Cp = cyclopentadienyl) and [(cod)­RhCl]2 (cod
= 1,5-cyclooctadiene) with (C2F5)2POH leads to the substitution of one Cp or chloro ligand by a quasichelating
unit. The novel coordination compounds were characterized by NMR and
IR spectroscopies, mass spectrometry, and X-ray diffraction analysis.
The platinum complex [(acac)­Pt­{[P­(C2F5)2O]2H}] (acac = acetylacetonato) was used
for the construction of hetero-bimetallic complexes by the treatment
with [(cod)­RhCl]2 and [Ni­(Cp)2]. The trinuclear
bimetallic complex [{(acac)­Pt­[P­(C2F5)2O]2}2Ni] is the first structurally characterized
hetero-bimetallic species containing a bis­(perfluoroalkyl)­phosphinito
bridge.