Cyclometallated phosphine complexes

The formation of rings that contain a thioether linkage does not appear to be catalyzed efficiently by Ru, even when terminal olefins are present. On the other hand, molybdenum appears to work relatively well, as shown in Eqs. 30 [207] and 31 [208]. Under some conditions polymerization (ADMET) to give poly-thioethers is a possible alternative [26]. Aryloxide tungsten catalysts have also been employed successfully to prepare thioether derivatives [107,166,169]. Apparently the mismatch between a hard earlier metal center and a soft sulfur donor is what allows thioethers to be tolerated by molybdenum and tungsten. Similar arguments could be used to explain why cyclometalated aryloxycarbene complexes of tungsten have been successfully employed to prepare a variety of cyclic olefins such as the phosphine shown in Eq. 32 [107,193]. 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

A series of cyclometalated platinum(II) phosphine complexes [Pt(bzq)(P-P)](Pp6) (P-P = dppm, dppe, dppp) has been synthesized and stracturally characterized. The absorption bands at ca. 300nm (e... 

Full details have now appeared of the stereoselective synthesis of 1,5,9-triphosphacyclododecane systems by oxidative liberation from molybdenum and chromium complexes of the macrocycle, obtained by coordination-template controlled reactionsMolybdenum complexes have also been used in the coordination-template dependent synthesis of the macrocyclic P,S system 151. A non-template synthesis of the 14-membered P2S2 macrocycle, 152, isolated in two isomeric forms, has been described. Halogenation of the cyclometallated phosphine 153 leads to a rearrangement, with the formation of the di-phosphinobiphenyl system 154, from which the free diphosphine can be liberated... 

In 2003, van der Boom and Milstein [16] reported that the following three mechanistic pathways account for most metal-based aromatic C-H activation processes in a review entitled Cyclometalated Phosphine-Based Pincer Complexes Mechanistic Insight in Catalysis, Coordination, and Bond Activation. ... 

A number of cyclometallated Rh complexes have been prepared with ligands such as 2-phenylpyridine,361 2-benzylpyridine,362 l-phenylpyrazole,363 6-(2-thienyl) bipy, and 2,6-diphenylthiophenol.364 The photophysical properties of some phenylpyridinate complexes have been studied.365 The hydrometallation of vinylcyclopropane with a cyclometallated Rh complex gave quinolyl pentenyl ketones,366 and the insertion of CO into the Rh-C bond of a cyclometallated phosphine has been reported.367... 

Cyclometallation and RE of the cyclopropane should give PtHClL2 the phosphine must cyclometallate in the -CH2Nb case, which would release CHsNb and leave a cyclometalated Pd complex. 

In an account of his forty years work on metal carbonyl-liquid ammonia systems, Behrens includes information on [M(CO) Lj,] complexes (L=NH3, bipy, phen, or terpy). Reviews have also appeared on alkylaminobis(difluoro-phosphine) complexes, cyclometallations involving phosphorus donor ligands, and optically active species/... 

The preparation of carbonyl-lr—NHC complexes (Scheme 3.1) and the study of their average CO-stretching frequencies [7], have provided some of the earliest experimental information on the electron-donor power of NHCs, quantified in terms of Tolman s electronic parameter [8]. The same method was later used to assess the electronic effects in a family of sterically demanding and rigid N-heterocyclic carbenes derived from bis-oxazolines [9]. The high electron-donor power of NHCs should favor oxidative addition involving the C—H bonds of their N-substituents, particularly because these substituents project towards the metal rather than away, as in phosphines. Indeed, NHCs have produced a number of unusual cyclometallation processes, some of which have led to electron-deficient... 

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