Trifluorophosphine Complexes of Transition Metals

Trifluorophosphine complexes of transition metals. J. F. Nixon, Adv. Inorg, Chem. Radiochem., 1985,29,1 (368). 

Trifluorophosphine Complexes of Transition Metals John F. Nixon... 

Chemical consequences of fluorocarbon phosphines The coordinating properties of pentamethylcyclopentaarsine Trifluorophosphine complexes of transition metals... 

Trifluorophosphine complexes of transition metals. T. Kruck. Angew. Chem., Int. Ed. Engl., 1967, 6,53-67(94). 

Ionization Potentials (eV) of Transition Metal Trifluorophosphine and Hydridotrifluorophosphine Complexes. Data for... 

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. 

A useful general synthetic approach involves the insertion of allene or dienes into the metal-hydrogen bond of transition metal hydrido-trifluorophosphine complexes (method C). 

Since fluorophosphines form part of a general review of phosphorus fluorides (282), and there is an excellent account of transition metal-trifluorophosphine complexes (152), the present article is not intended to be comprehensive, but rather to highlight some of the more recent developments in this expanding area of inorganic chemistry. 

A number of transition metals have been shown to react with trifluoro-phosphine [280]. Chromium, cobalt, nickel, palladium and iron all produced stable complexes. Manganese and copper also reacted at —196°C, but the products were unstable, and decomposed on warming. Nickel vapour has also been reacted with difluorochlorophosphine, yielding Ni(PF2Cl)2. Complexes produced by reaction with phosphine itself were unstable, decomposing on warming, although when a mixture of phosphine and trifluorophosphine was co-condensed with nickel vapour some mixed complexes were isolated. 

There are many similarities in the behavior of PF3 and CO as ligands. This is manifested by the existence of a large number of PF3 complexes of the transition metals (197, 226). Several UPS studies of such complexes have now appeared in the literature (20, 152, 169, 182, 221, 227). As pointed out in Section II, it is difficult to arrive at a completely unequivocal set of assignments for these compounds other than for the predominantly metal MOs. It is seen below, however, that one of the advantages of studying the UPS of the PF3 complexes is that many more ionizations pertinent to bonding discussions are discernible. Furthermore, trifluorophosphine complexes tend to be more thermally stable than their carbonyl counterparts. 

Transition metal carbonyl chemistry originated with the discovery of [Ni(C0)4] in 1890. Although the first trifluorophosphine coordination complex was prepared the following year by Moissan (263) by treating... 

An interesting feature of hydrido transition metal-PF3 complexes is that apart from a few dinuclear systems (Section VI) only mononuclear systems are so far known and there is as yet no corresponding chemistry analogous to that of polynuclear carbonyl hydrido compounds. The trifluorophosphine metal hydrido compounds are usually highly acidic and can readily form metallate ions such as [M(PF3)m]x and [MH(PF3) r. 

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. 

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)]. 

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. 

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 similarity in the coordinating ability of CO and trifluorophosphine toward transition metals is illustrated by mass spectroscopic studies on HCo(PF3)j.(CO)4, c, which show that the Co-CO and C0-PF3 bond energies are both 56 15 kcal (279). Along the series a = 4 0, the AH formation of the complex becomes progressively more negative by about 200 kcal/mole, which is approximately the difference between... 

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