Rhenium i Alkynyls

CsMes)], has been isolated in three oxidation states and the magnetic, optical and electrochemical properties investigated. EPR spectra of the dirhenium complexes show undecets with Aiso.Re values half of those of related monorhenium radical cations, indicating spin delocalization over two rhenium centers [79]. The limiting HOMO-LUMO energy gap of each series of R-(C=C) -R could be 

Extension of this work to the triynyl system was accomphshed by reacting the butadiynyl complexes with an acetylenic proton, [Re(CO)3(N N)(C=C-C=CH)], with an excess of bromo- or iodoalkynes in the presence of a catalytic amount of 

The construction of carbon-rich materials using platinum(ii) phosphine systems is probably one of the most active areas of research in the past decade. The transsquare planar geometry adopted by the platinum(ii) center provides a versatile motif for the construction of one-dimensional linear structures, while the corresponding ds-geometry could serve as connectors at an angle. 

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. 

Owing to the advances in the synthesis of organoplatinum(ii) alkynyl compounds as well as the intriguing physical and photophysical properties exhibited by these materials, the evaluation of their structure-property relationship is therefore attractive and feasible. The spectroscopic properties of mononuclear nickel(ii), palladium(ii) and platinum(ii) alkynyl complexes of the type trans-[M(C=CR)2L2] (R = alkyl, aryl L = phosphine, stibine) have been widely investigated [111-114]. The electronic absorption spectra of this class of complexes have been reported by Masai et al. [115], while the emission properties of a series of closely related platinum(ii) complexes were reported by Demas and coworkers [116]. The lowest 

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Figure 42 Decanuclear silver(i)—rhenium(i) alkynyl complexes 95a-d.

Pentanedionates, with Ru and Os half-sandwiches, 6, 483 Pentanuclear silver(I)-rhenium(I) alkynyl rigid-rod complex, preparation, 2, 229-230... 

Other work has demonstrated that it is possible to switch ON and OFF luminescence by reduction/oxidation, and it has been demonstrated that such switching is possible inside an OTTLE cell. Many alkynyl complexes, especially those of rhenium, platinum,copper, silver or gold " are highly luminescent from their excited MLCT or metal perturbed 71 states. This opens up the possibility to significantly influence their emissive properties by redox processes. An interesting example is found in recent work of Wong et Unlike other rhenium(I)-alkynyl complexes, heterobimetallic... 

A series of rhenium(I) complexes [Re(CO)3(N-N) ( C=C -R)] containing conjugated alkynyl ligands displayed remarkable luminescence properties. The origin of the... 

In 1995, Yam and coworkers reported the first series of luminescent rhenium(i) diimine alkynyl complexes [Re(CO)3( Bu2bpyXC=C-R)] (R = alkyl or aryl) (Scheme... 

The robustness of the rhenium(i) diimine alkynyl systems and rich photophysical behavior have rendered them suitable as metalloligands for the synthesis of mixed-metal complexes. It is well-known that organometallic alkynes exhibit rich coordination chemistry with Cu(i), Ag(i) and Au(i) [214-218], however, photophysical properties of these r-coordinated compounds are rare. Recent work by Yam and coworkers has shown that luminescent mixed-metal alkynyl complexes could be synthesized by the metalloligand approach using the rhenium(i) diimine alkynyl complexes as the z -ligand. Reaction of the rhenium(i) diimine alkynyl complex [Re(bpy)(CO)3C=CPh] with [M(MeCN)4]PF6 in THF at room temperature in an inert atmosphere afforded mixed-metal Re(i)-Cu(i) or -Ag(i) alkynyl complexes (Scheme 10.31) [89]. Their photophysical properties have also been studied. These luminescent mixed-metal complexes were found to emit from their MLCT[d7i(Re) —> 7i (N N)] manifolds with emission bands blue-shifted relative to their mononuclear precursors (Table 10.5). This has been attributed to the stabilization of the dTi(Re) orbital as a consequence of the weaker t-donating ability of the alkynyl unit upon coordination to the d metal centers. 

Exploration of the constmction of mixed-metal luminescent materials using rhenium(i) diimine alkynyl complexes in a terminal mode has also been of interest... 

In the case of formation of the rhenium(I) complex 69 (Scheme 38), the alkynyl reagent [I(C=CSiMe3)Ph][OTf] has been used to add an additional alkyne functionality to convert a diyne to a triyne. ... 

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