Acetylides bridging

Harriman and Ziessel recently reported the acetylide bridged bimetallic complex [(mpt)Os(tCCb)Ru(bpy)2]4+ (tCCb shown in Scheme 4) [62]. Excitation of the Ru(II) center resulted in nearly 100% efficient energy transfer to the Os to mpt MLCT state with a rate constant of 7 2 x 10iO s-1. Analysis of the Forster overlap factor led to the prediction of a much lower rate constant for resonant energy transfer and the authors concluded that the process was dominated by an electron exchange transfer mechanism. 

The extended Hiickel method, which is a semiempirical quantum chemistry method, is often used as a preliminary step in the DFT study of molecular orbital analysis. The acetylide-bridged organometallic dinuclear complexes 5.2 were studied by Halet et al. using the extended Hiickel method for qualitative analysis and DFT for additional electronic properties [97], The extended Hiickel analysis concluded that the main contribution of the Pt-C bond arises from ct type interactions while the n back-donation is very weak. The DFT/BP86 calculation gives a 2.371 eV HOMO-LUMO gap. The electronic communication parameter Hdb between the bis-ferrocene compound linked with platinum acetylide (5.3) was calculated to be 0.022 eV, compared with 0.025 eV obtained experimentally by Rapenne and coworkers using DFT and the extended Hiickel method [98],... 

Z-selective cross-coupling of terminal alkynes with isocyanides to exclusively yield (Z)-l-aza-l,3-enyne products has been achieved for the first time using a constrained geometry catalysts [Y(C5Me4Si(Me2)NR)(Alk) (THF)X] (Aik = R, dimethylaminobenzyl R = lBu, Ph, 2,4,6-Me3C6H2. The intermediate was shown to be the acetylide-bridged dimer [Y(C5Me4Si (Me2)NR)(p-C=CPh)]2.41 [24]... 

The synthesis of rigid-rod oligomeric Au complexes (5.17 and 5.18), with (iso-cyanoaryl)acetylide bridging ligands, has been achieved by elimination of BuC = CH from the precursor BuC = C-Au-C = N-Ar-C=CH [31, 32]. However, direct molecular weight determinations of the resultant materials were not possible due to insolubility. Similarly, the synthesis of the insoluble polymeric materials (5.19) with Au centers bridged by diisocyanides and diacetylides has also been described [33, 34]. 

Two hydride- and acetylide-bridging diplatinum(II) compounds (192,193) were characterized as products of reactions between Pt(II) and Pt(0) precursors via C-H bond activation and/or rearrangement (Scheme 10.80) [136]. 

Hurst SK, Ren T (2002) Synthesis, characterization and electrochemistry of diruthenium complexes linked by aryl acetylide bridges. J Oiganomet Chem 660 1-5... 

Photolytic reaction of metal acetylide complexes with simple metal carbonyls has been used to form heterometallic acetylide bridged complexes. For instanee, photolytic reaction of a benzene solution of [Fe(CO)5] and [( / -C5R5)Mo(CO)3 (C=CPh)] (R = H, Me) under continuous bubbling of argon results in a rapid... 

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