Alkenyls bridging

As presented in Section II, several PBs featuring unsaturated C2 linkers (-C=C—, trails or cis -CR=CR -) have been prepared. Here, only the structure of the ds-alkenyl bridged systems 22 will be discussed since these are the only systems prone to forming intramolecular P-B... 

Figure 17 Key geometric and NMR data for the alkenyl-bridged phosphine-boranes 22e and 22g.

The straightforward reaction forms aryl-, alkyl-, or alkenyl-bridged bis(triphosphapentadienes) after multiple addition of phosphaketene to bis(trimethylsilyl)phosphanes, which are coupled by carbon chains [Eq. (46)]. 

Cluster 41 with diphenylacetylene gives the alkenyl-bridged [Ru3(p3,77 -L)(g-7/ 7/2-PhC=CHPh)(CO)8] (92JMC(71)L7, 940M4352). 

The photochemical behavior of these oligomers was first examined with the dimers which were irradiated with a medium-pressure mercury lamp through a Pyrex filter to remove any wavelength below about 300 nm. In dilute methylene chloride solutions, all the dimers (la and Ila-IId) isomerized to the cis conformation until the cis/trans thermodynamic equilibrium mixture was reached. No other photoinduced reaction was detected in these conditions. Irradiation of concentrated solutions, as well as crystalline solid samples, gave rise to molecular dimerization through the alkenyl bridge with all the dimers, through the classical [n2+7t2] cycloaddition process, e.g. for dimer la ... 

A single-crystal neutron diffraction study of [Os2(CO) -(p-Ti t) -C2H4) ] has been made. The synthesis and characterisation of the alkenyl-bridged compovmds (PPh4] ... 

The kinetics and mechanism of the hydrogenation of diphenylacetylene promoted by the alkenyl-bridged cluster [Ru3(CO)8(li3-Ti2-ampy)(p,-T T 2-PhC=CHPh)] (Hampy = 2-amino-6-methylpyridine) has been investigated497. The synthesis, structure and hydrogenation catalytic activity of the related [Ru3(CO)6(PPh3)2(lt3-r 2-ampy)(n- nl Ti2-PhC=CHPh)] have been described . Tri- and hexanuclear ruthenium complexes [Ru3(CO)8(lA-RCOCH=CPh)2l and [Ru6(CO)i2(lt-CO)2( X-H)2(M4-0)(p.-RCOCH=CPh)2] (R = Me, p-Tol) have been prepared and characterised by X-ray diffraction. 

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