Phosphido-bridged

Various type (967) dinuclear complexes with phosphido bridges have been prepared, usually by reduction of [(R3P)2NiX2] with, for example, sodium.2372-237 The terminal phosphines can be exchanged by other phosphines or by CO, yielding (968) and (969) in the latter case.2373,2374 Diphenylphosphide Ni1 complexes have also been prepared electrochemically.2376... 

A number of complexes with carbonyl and hydride bridges have been discussed above and phosphido bridges are discussed below. The most common of the other bridges are sulfur and... 

Phosphido-bridged multinuclear complexes have been formed from zinc chloride of the form [Zn4(PPh2)4Cl4(PRR 2)2], where R and R are alkyl or phenyl groups. Related tetrameric structures can be formed with a bridging dialkyl phosphide or (trimethyl)silylphenyl phosphide.303... 

Wiped-Film Evaporator/02 Reactivation of Catalyst. In this technology [38], spent or-ganophosphine-modified rhodium catalyst is first concentrated in a wiped-film evaporator where most of the organophosphine is removed. The rhodium concentrate is contacted with air to break down phosphido bridges in rhodium clusters. This air treated concentrate may then be used as a catalyst precursor. This procedure is suitable in circumstances where most of the aldehyde dimers, trimers and tetramers are sufficiently volatile to be removed in a wiped-film evaporator. 

Equation 2.12. Reactivation of a phosphido bridged deactivated catalyst... 

Such compounds may be contacted with partially deactivated hydroformylation catalyst under non-hydroformylation conditions to effect disruption of the phosphido bridges of a rhodium cluster (Equation 2.12). After the treatment period, the catalyst solution is again suitable for hydroformylation. 

We went back and looked at that system, because we thought it had quite a bit of promise. It turns out that, with triphenyl phosphine, platinum(O) will attack the phosphorous phenyl bonds to produce red polymers which are phosphido-bridged platinum species. But we were more interested in the small alkyl phosphines, because we expect those to make the metal center even more reactive (being sterically unhindered and more basic). 

Miller (90), King (209, 210), and Bruce (211) first observed the formation of neutral metal fluoride species and metal fluoride-containing ions in the mass spectra of pentafluorophenyl derivatives of phosphorus, germanium, silicon, and phosphido-bridged iron carbonyls (90) and aliphatic and aromatic fluorocarbon derivatives of iron, cobalt (209-211),... 

In bridged metal-metal bonded dimeric complexes, the relative importance of metal-metal and bridging ligand effects are more difficult to unravel. Dahl and his co-workers have elegantly exploited systematic crystallographic analyses to detail the stereochemical consequences of valence-electron addition or removal in dimeric metal complexes (46, 47, 65, 230) and clusters (66, 88, 204, 205, 213, 216, 222). Their experimental work has been neatly underpinned by nonparameterized approximate Hartree-Fock molecular orbital calculations (217) on the phosphido-bridged dimers [Cr2(CO)80ti-PR2)2]n"2 and [Mn2(CO)g(/i.-PR2)2]n (rt = 0, + 1, or +2) ... 

Even chlorine which is bound to phosphorus coordinated to a metal atom can be exchanged for fluorine, but higher temperatures are required. So the four-membered phosphido-bridged metal complex 16 is fluorinated at temperatures over 100C, whereas the exchange reaction in the case of the corresponding iodide proceeds at room temperature and for the bromide at over 60CC in 80% yield each.77... 

CARTY Phosphido-Bridged Iron Group Clusters... 

Scheme L Phosphido-bridged complexes reactivity at other sites.

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