Platinum alkynylation

Very few rr-bonded alkyne complexes of palladium(ll) have been reported in recent years. Except for two examples of monomeric complexes, most of them are polymetallic derivatives where a metal alkynyl acts as a liquid, as discussed above for some Pd(0) derivatives. These complexes adopt interesting stmctures that conform to the types shown below. They have been synthesized by reaction of a metal alkynyl with [PdCl(7/ -C3H5)]2 or Pd(C6Fs)2(THF)2. Platinum alkynyl complexes are the most common ligand frame used, as shown in structures 76-79, but other metal alkynyls can play the same role, such as the Rh and Ir alkynyls depicted 80 and 81. The 7 -alkyne moieties bound to palladium are rotated out of the Pd-coordination plane. The angles of the vectors and the normal to the... 

The auxiliary phosphine ligands also play an important role in controlling the physical properties of platinum(ii) alkynyl complexes. Monomeric complexes of trans-[Pt(PR3)2(C=CR )2] usually exist in the crystalline state at room temperature. Cooper et al. recently communicated the synthesis and isolation of platinum alkynyls in the liquid state at room temperature using trioctylphosphine as the auxiliary ligands [97]. It was proposed that these liquids may possess enhanced nonlinear optical properties. 

Scheme 10.18. Monodisperse luminescent platinum alkynyl oligomers.

Besides the platinum and palladium diphosphine systems, platinum polypyridine complexes have also attracted attention in recent years [130-162). Their changes in spectroscopic and luminescence properties brought about by Pt Pt and n-n interactions are of particular interest [138-142). For instance, the square planar platinum(ii) diimine complex [Pt(bpy)Cl2) exhibits polymorphic behavior and rich photophysical properties [142-144). These, together with the recent growing development of platinum alkynyl systems [98, 122, 125, 145-147), mainly due to the... 

Dinuclear Pt-Rh (336a-c, 339) and Pt-Ir (337a-c, 338) complexes with doubly alkynyl bridging systems have been isolated from the reactions between platinum alkynyl complex, 40 and from cyclooctadiene complexes of rhodium and iridium (Scheme 91). ... 

Bis(alkyl) complexes, with mercury, preparation, 2, 428 Bis(alkylidene)s, in Ru and Os half-sandwiches, 6, 583 Bis(alkylimido) complexes, with chromium(VI), 5, 346 Bis(rj2-alkyne)platinum(0) complexes, preparation, 8, 640 Bis(alkynyl) complexes in [5+2+l + l]-cycloadditions, 10, 643 with manganese, 5, 819 with mercury, preparation, 2, 426 mononuclear Ru and Os compounds, 6, 409 with platinum, 12, 125 with platinum(II), 8, 539 with titanium(IV), 4, 643 with zirconium, 4, 722... 

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

Platinum(II) complexes with alkenyls, characteristics, 8, 471 with alkynyls, characteristics, 8, 538 into 7 3-allyl complexes, 8, 652 with arylenes, bisaryls, macrocycles, 8, 491 with aryls... 

Osakada, K. Hamada, M. Yamamoto, T. Inter-molecular alkynyl ligand transfer in Pd(II) and platinum(II) complexes with CCC02R and CCPh ligands. Relative stability of the alkynyl complexes and conproportionation of dialky-nyl and diiodo complexes of these metals. Organometallics 2000, 19, 458—468. 

The influence of argon and ethylene bubbling on the product ratios is consistent with expected shifts of the dissociative equilibrium shown in equation 149113. Thus, the cr-alkynyl complexes are thought to arise via reactions of the alkynyliodonium triflates with the coordinatively unsaturated bis(triphenylphosphine)platinum(0) species 34113, a pathway that should be optimized as ethylene is removed (i.e. by argon). The -complexes, on the other hand, apparently originate from the undissociated platinum(0)-ethylene complex113, their yields being maximized as ethylene is introduced. 

Work on Ptn terpyridyl complexes has not been limited to just mononuclear systems. Yam and coworkers have also investigated complexes wherein two platinum centers are attached through alkynyl bridges more specifically they studied chromophores of the type f Hu. tpy )Ptf( =C)nI>tf Hu. tpy)]2+ (3.10) [65], These structures exhibit photoluminescence in both the solid state and in room temperature solutions, the latter assigned as 3CT in nature mixed with 3IL and 3LLCT character. 

They may be readily transformed to r] -aUcynyl and vinylidene complexes. The coupling of two ) -alkynyl ligands results in platinacyclopentadiene species." A platinum(II) disilyl( -alkyne) undergoes insertion (see Insertion) and reductive elimination (see Reductive Elimination) to disilacyclohexene (Scheme 31)." Metal-diaUcynyls can also play jr-donors to form the coordination complexes of various configurations, as shown in (10-13) and so on." Such a,tt-bridging modes may have interconversion. Multi- aUcynyl complexes can even constitute clusters or higher-order stractures. ... 

Platinum(II) (See Platinum OrganometalUc Chemistry) and Palladium(II) See Palladium OrganometalUc Chemistry) Alkynyls... 

Apart from phosphine ligands, polypyridine ligands have been incorporated into platinum(II) alkynyl moieties to give luminescent complexes. The use of polypyridine ligands is interesting because their planar structure and the square-planar coordination geometry of the d platinum(II) center could modify the excited state of these luminescent complexes by tt tt and/or Pt- Pt interactions. The complex... 

Three novel Imninescent dinuclear platinum(ll) complexes with bridging alkynyls have been studied. The complexes [Pt( Bu3-terpy)- C=C -Pt( Bu3-terpy)] (n = 1, 2, 4) showed intense high-energy 1L (alkynyl and Bus-terpy) absorption bands at ca. 308-342 mn. Low-energy absorption bands at ca. 428-522mn were assigned to MLCT (dTr(Pt) 7t ( Bu3-terpy)) transitions mixed with LLCT (tt (alkynyl) r ( Bu3-terpy)) character. Remarkably, the... 

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