Phosphido-bridged complexes

Scheme L Phosphido-bridged complexes reactivity at other sites.

Figure 11. A plot of 8 (T-31J vs. bond angle at phosphorus for phosphido-bridged complexes Fe2(CO)6(X)(PPh2) where X is a three-...

Bis(cyclopentadienyl)zirconium(III) complexes alkynyl-bridged complexes, 4, 749 dinitrogen complexes, 4, 747 electrochemical reduction, 4, 745 phosphido-bridged complexes, 4, 750 Bis(cyclopentadienyl)zirconium(IV) complexes electrochemical reduction, 4, 745 with M-C r/)-bonds, 4, 895 with M-C r/i2-bonds, 4, 887 with M-C r/i3-bonds, 4, 884 with M-H bonds, 4, 878 with M-N bonds, 4, 910 with M-0 bonds, 4, 917 with M-P bonds, 4, 927 with M-S bonds, 4, 930 with M-Si bonds, 4, 925 non-functionalized metallocene halides, 4, 870 ring-functionalized metallocene halides, 4, 874 Bis(cyclopentadienyl)zirconium(III) halides, in organic synthesis, 4, 754... 

Metal-chromium phosphido-bridged complexes, with carbonyls, 5, 217... 

The dehalogenation of arene ruthenium derivatives 299 and 300 with Co2(CO)s gives access to Ru—Co complexes stabilized by a phosphido bridge. Complexes 301 (40%) and 302 (30%) are isolated in both cases. In addition, complex 300 afforded the RuCo2 derivative 303 (10%) (170,171) [Eq. (39)]. 

It is against this background that we have developed in our laboratories a very simple one-step procedure which allows the synthesis, usually in acceptable yields, of a wide variety of and M -dppm-CO mono- and (more usually) binuclear complexes directly from metal salts. The procedure has been extendi with considerable success to the one-step synthesis of certain heterobinuclear systems and also some phosphido-bridged complexes of Co and Np. While this study has so far been largely concerned with Co and systems, preliminary work has been carried out with Rh , Pd and Fe . Some of the work described herein has been reported in preliminary communications but a complete overview of all aspects of the investigations carried out so far is given here in order that the very broad applicability of the procedure can be fully appreciated. 

Perhaps the most remarkable products of these reactions are phosphido-bridged complexes obtained from both Co and Ni. Such complexes are normally prepared [the recent literature concerning phosphido-bridged complexes has been summarized... 

T e Co and Ni Vdppm/NaBH4/CO reactions discussed above are normally carried out such that the NaBH4 is added over a period of 10-30 minutes. If, however, the addition time is decreased to one minute or less, the reactions follow an entirely different course and phosphido-bridged complexes are produced (25) in acceptable yields. Thus, with reactant ratios of 1 2 3, the reaction with C0CI2 gives the hydrido-phosphido bridged complex 12 [ P NMR 8P 47.6 (d), SPg 215.6 (quintet), J 54 Hz. H NMR SCo-H -17.75 (sextet), J values PaH = PgH = 29.2 Hz. IR Oco 1921 cm" ], in 20-30% yield after recrystallization. Small amounts of 2 are also formed and this contaminates later crops of 12 in the recrystallization process. Complex 12 can also be produced, together with the known (26) 13, in... 

Similar reactions using Ni give (25) the phosphido-bridged complex 14... 

While, because of our interest in bimetallic species, most of the work discussed in this account has concentrated upon reactions which involve dppm, the synthetic procedure outlined clearly represents a novel and extremely simple approach to metal carbonyl phosphine complexes in general. Of particular significance, however, are the one-step reactions which lead to heterobimetallic or phosphido-bridged complexes and the ready access to palladium carbonyl complexes. Further research in this area is likely to be extremely productive. 

Jones and co-workers reported the fully characterized neutral mixed valence cluster [Pd3(Cl)(/r- Bu2P)3(CO)2], Pd3(4/3). Reaction of [PdCl(CO)] with Li- Bu2P in THF at —78 °C produces a mixture of compounds (Eq. 6) from which the trinu-clear phosphido-bridged complex was isolated in low yield. 

The reaction of [RuCl3(NO)(PMePh2)2] with PhjPH and a Zn/Cu couple yields the binuclear phosphido-bridged complex [Ru(NO)( j-PPh2)(PMePh2)]2 (132) the tetranuclear species (133) (formally a mixed Ru /Ru" complex) is also obtained in poor yield. Compound (132) can also be obtained from [RuH(NO)(PMePh2)3], and the PPh, analogue is known. 

The methyliridium complex [ (CO) wTiT PPhjr rMe(CO) (PPh ) ] undergoes coupling of the methyl and phosphide ligands on heating to 110°C to afford the mono-phosphido bridged complex [(CO). (PPh Me)-... 

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