Trifluorophosphine reactions

IR spectra, 22 177-179 Raman spectra, 22 178, 179 triazole and triazolate complexes, 32 180 trifluoride, structure, 27 90, 91, 92, 95, 97 trifluorophosphine complexes cyclopentadienyl, 29 103 hexakis anion, 29 53-54 [Ni4(0CH3)4(acac)4(CH3OH4)l, 43 323 Nitramide, reaction mechanisms, 22 138, 139 acid catalysis, 22 139... 

Direct condensation of metal vapors with trifluorophosphine at -196°C provides a convenient alternative to the high-pressure route to metal-PF3 complexes. The reactions of Mo, Cr, Co, Ni, and Pd vapors with PF3 yield only one volatile product in each case, namely Mo(PF3)6 (132), Cr(PF3)6, Co2(PF3)g, Ni(PF3)4, and Pd(PF3)4 (128), respectively. The yields are good, 40-100% depending on the metal vapor used. Some defluorination of the PF3 accompanies the formation of Cr(PF3)6. No complex could be isolated from the manganese vapor-PF3 reaction, although some defluorination seems to have occurred. The reaction of iron and PF3 is complex,... 

Trifluorophosphine is a very convenient ligand in metal atom chemistry to use along with other ligands, e.g., in the stabilization of metal arene complexes (Section III,B). Reaction of a mixture of PF3 and PH3 with nickel vapor yields Ni(PF3)3PH3 and Ni(PF3)2(PH3)2 but no Ni(PH3)4. Attempts to make Ni(PH3)4 lead to hydrogen evolution from the ligand during or after condensation with the nickel vapor (128). 

It was decided to study the system tetrakis (trifluorophosphine) nickel- (0) -ammonia (23) in some detail a smooth reaction was observed when the complex, condensed on excess ammonia at liquid air temperature, was allowed to warm up gradually. Precipitation of colorless crystals, identified as ammonium fluoride in almost stoichiometric amount, based on complete ammonolysis of the phosphorus-fluorine bonds, was observed at temperatures as low as —90° to —80°. Removal of the ammonium fluoride by filtration at temperatures not higher than —50°, and subsequent slow evaporation of the ammonia from the filtrate invariably led to a brown-yellow solid, although a colorless, crystalline material was formed initially. The product was decomposed almost instantaneously by water with precipitation of elemental nickel. Analysis of the hydrolyzate obtained in aqueous hydrochloric acid revealed a nickel-phosphorus-nitrogen atom ratio close to 1 4 4, corresponding to an apparently polymeric condensation product. 

The question of the molecular structure of the adducts of tetraborane(8) has now been resolved 144>. The boron-11 nmr spectra of the carbon monoxide and trifluorophosphine adducts have been analyzed 140> in terms of the 2112 topological geometry 141> proposed by Dupont and Schaeffer 142>. The dimethylaminodifluorophosphine adduct of tetra-borane(8) 143> which was prepared by the following reaction is stable at room temperature. 

Transition metal carbonyl complexes can be suitable precursors, for example, treatment of hydrido complexes or their alkali salts with PF3 under UV irradiation followed if necessary by acidification of the reaction mixture (method E). Interestingly, vanadium forms the hydrido trifluorophosphine complex [VH(PF3)6], whereas with CO, the paramagnetic [V(CO)6] is formed. 

Several other tetranuclear complexes containing different metals have been obtained from the reaction between metal carbonyl and metal trifluorophosphine complexes (method E) or by intermolecular ligand-exchange reactions (method F) between tetranuclear complexes. The following structures have been proposed on the basis of 19F NMR and mass spectroscopic studies. 

A variety of synthetic routes to monoene and polyene tri-fluorophosphine-transition metal complexes have been devised. Direct photochemically induced reaction of a metal-PF3 complex with an activated alkene or diene (method A) has proved useful only for iron, the products being either [Fe(PF3)4(alkene)J or [Fe(PF3)3(diene)] (194). Mixed carbonyl-trifluorophosphine complexes of the type [Fe(PF3)x(CO)3 x(diene)] result from either thermal or photochemical reactions of dieneiron carbonyl complexes and PF3 (52, 53) (method B). The compounds are fluxional. 

Interestingly, although the reaction of 1,3-cyclohexadiene, chromium atoms, and PF3 yields bis(//4-cyclohexadiene)bis(trifluorophos-hine)chromium, the corresponding reaction with 1,4-cyclohexadiene yields the //5-cyclohexadienyl hydrido tris(trifluorophosphine)-chromium complex, which rearranges in the presence of silica gel to form [Cr( 4-C6H8)2(PF3)2] rather than (i/4-cyclohexadiene)tetrakis-(trifluorophosphine)chromium (40) (Scheme 2). 

Reaction of chromium atoms, l,5-cyclooctadiene(l,5-cod), and PF3 on the other hand yielded a separable mixture of [Cr(C8Hu)(PF3)3H] and (j74-cycloocta-l,5-diene)tetrakis(trifluorophosphine)chromium. The latter is readily converted to the former by warming a solution of it to 90°C (Scheme 3). This rearrangement is impaired under an atmosphere of PF3 and the 1,5-cod is preferentially displaced to give [Cr(PF3)6]. 

The first reported arene-transition metal trifluorophosphine complex [Cr(i/6-C6H6)(PF3)3] was obtained by UV irradiation of [Cr(i/6-C6H6)(C0)3] with PF3 (method A), whereas the corresponding thermal reaction afforded instead the mixed carbonyl trifluorophos-... 

A particularly interesting example of CO displacement involves the photochemical reaction of the early transition metal complexes [M(>/5-C5H5)2(CO)2] (M = Ti, Zr, Hf) with PF3 (Scheme 10). In the case of (M = Hf) this complex represented the first hafnocene-phosphine complex to be reported. A slightly better synthetic route to the mono(trifluorophosphine)titanium(II) complex involves displacement of PEt3 from [Ti( /5-C5H5)2(CO)(PEt3)]. 

Other routes involve treatment of a metal-trifluorophosphine halide with either sodium or lithium cyclopentadienide (method D), or direct reaction between a metal-PF3 complex and cyclopentadiene (method E). 

Trifluorophosphine and carbon monoxide readily undergo ligand-exchange reactions in their transition metal complexes. The close similarity in bonding characteristics of the two ligands toward transition metals has been discussed extensively in several review articles (72,174,272) and the evidence will not be repeated here. Extensive vibrational spectroscopic studies have been made on mixed carbonyl-PF3 metal complexes (72,174) and force constant calculations have been carried out in some cases. 

Since the P—F bonds are labile in these complexes some mixed trifluorophosphine-fluorophosphite nitrosyl complexes have been prepared by reactions with either diisopropyl-water mixtures or barium hydroxide (method F) to give the (PF20) compounds which can be alkylated. 

Good yields of certain rhodium(III) perfluoroalkyl derivatives have been obtained in oxidative addition reactions of perfluoroalkyl iodides (R I) with rhodium (I) trifluorophosphine complexes (method C). 

Alternatively, treatment of trifluorophosphine metallates with R3MC1 (method B) or via metal-metal bond cleavage reactions of dinuclear PF3 metal complexes with a group IV metal hydride R3MH (method C) have been useful synthetic methods, e.g.,... 

The small number of complexes of this type (listed in Table XVIII) have been obtained via the reaction of a trifluorophosphine metallate... 

The parent TMM complex (190 R = H) undergoes photochemical ligand substitution with trifluorophosphine or trimethylamine Al-oxide assisted substitution with tertiary phosphines or t-butyl isocyanide (Scheme 5A) Trimethylamine A-oxide assisted substitution using isoprene as the incoming ligand results in C-C bond formation to afford the bis-TT-allyl complex (197). An intramolecular version of this reaction is also known.The parent complex (190 R = H) reacts with electrophiles. Addition of HCl or Br2 gives the methallyl complexes (192) and (198), respectively. Tetrafluoroethylene adds across the Fe bond to afford (199) under photochemical conditions. Complex (190) undergoes Friedel-Crafts-type acylation with... 

The positive value found for PCI3 (and for other haldgenophosphines) can be understood as an inductive effect or as a very strong t bond which deshields the phosphorus atom. Many authors prefer the first explanation. In fact, in the case of PF3 the Ni-P force constant was 2.7 (206) or 2.37 mdyne/A. (123)—a rather low value which does not indicate the presence of a double bond. On the other hand, the examination of the force constants in the series Ni(CO)4 n(PF3)n (n = 0, 1, 2, 3, and 4) indicates that PF3 has about the same properties as CO (59, 123). This is supported also by the statistical distribution of the products in the exchange reaction between Ni(CO)4 and PF3 and by the little variation of NMR chemical shift on these products (56). Loutellier and Bigorgne (123) prefer to consider trifluorophosphine as a weak a donor and weak 7T acceptor for the following reasons. 

The parent compound trifluorophosphine (b.p. — 101.4°C) will only be discussed briefly since preparative methods, physical properties, and general reactions have been adequately discussed previously by Schmutzler (282) and will not be repeated here. Usually trifluorophos-... 

Oxidation of trifluorophosphine by halogens is well known (282) and although corresponding reactions with alkyl or aryl fluorophosphines have received only little attention, it has become apparent that oxidation to the pentavalent phosphorus fluorides can be brought about by a wide variety of reagents. In certain cases the reducing property of the fluoro-phosphine has been utilized in the synthesis of zero-valent transition metal fluorophosphine complexes (Section IX). 

The reaction between dialkylaminodifluorophosphines and hydrogen fluoride has not been reported, but other studies (238, 249) using bifluoride ion suggests that the resulting trifluorophosphine (or any unreacted dialkylaminodifluorophosphine) will react further with the... 

Fluorophosphites are also among the products from reactions between (a) trimethylphosphite and tungsten hexafluoride 251), (6) alcohols and dichlorofluorophosphine 55, 67, 205), (c) phosphorus pentafluoride or trifluorophosphine and trimethylphosphite 35), and d) epoxides and trifluorophosphine in the presence of a tertiary amine 150), but these are of less importance from a preparative viewpoint. The attempted... 

Trifluorophosphine complexes of nickel, palladium, and platinum have been obtained by direct reaction of PF3 with the metal at elevated temperatures and pressures (172). Similarly several fluorophosphine complexes of zero-valent nickel can be made under very mild conditions (60°C) using metallic nickel formed by decarboxylation of nickel oxalate... 

Clark and co-workers have shown that trifluorophosphine can replace all the CO groups from certain metal carbonyl complexes (56, 58, 59). Other fluorophosphines behave similarly, the reactions usually being thermally or photochemically induced (320, 57, 121, 284, 287, 61). In the case of HCo(CO)4, however, substitution by PFg occurs rapidly and spontaneously even at —20°C (320). 

Complete displacement of CO from [Rh(CO)2Cl]2 is possible using fluorophosphines RPF2 the reaction with trifluorophosphine affording [(PF3)2RhCl]2 (250). 

There is an interesting report of carbonyl substitution in the reaction between phosphorus pentafluoride and MeSiH2Co(CO)4 (114, 7). There is evidence that PF5 is reduced by the silicon-hydrogen bonds yielding HCo(CO)4, fluorosilane, and trifluorophosphine the latter subsequently displaces carbon monoxide from the hydridocarbonyl complex. 

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