2-Diphenylphosphino-6- pyridine

Shieh, S.-J., Hong, X., Peng, S.-M. and Che, C.-M. (1994) Synthesis and crystal structure of a luminescent onedimensional phenylacetylide-gold(I) polymer with 2,6-bis(diphenylphosphino) pyridine as ligand. Journal of the Chemical Society, Dalton Transactions, 3067-3068. 

The coupling of secondary phosphines with aryl iodides was also extended to pyridines. 3-Iodopyridine and diphenylphosphine were coupled to give 3-diphenylphosphino-pyridine in 60% yield (7.80.), The catalyst in this reaction consisted of copper(I) iodide and N,N -dimethylethylenediamine and caesium carbonate was used again as base.102... 

A popular ligand is based on 2-(diphenylphosphino)pyridines [96CCR (147)1]. However, it does not necessarily fulfill the chelate function. Thus, the reaction of 2-(diphenylphosphino)pyridine with NEt4[Ir4(CO)nBr] gives [Ir4(CO)10(Ph2PPy)2], where the heterocycle acts as a monodentate P... 

Bis(diphenylphosphino)pyridine forms tetranuclear 111 (L = CO, S02) (83JA6332), and the carbonyl complex on interaction with carbon monoxide and ammonium hexafluorophosphate in chloroform produces [Rh2(g-L)2(CO)2(MeOH)Cl](PF6) (83JA6986). [RhAu(g-L)2](BF4)(N03)... 

Another interesting carbonylation that has been carried out in ionic liquids is that of 3-alkyn-l-ols and l-alkyn-4-ols by [Pd(OAc)2]/ PyPPh2(PyPPh2=2-(diphenylphosphino)pyridine) to give evo-a-methylene y- and 8-lactones, respectively.60 The products were isolated in almost quantitative yields by distillation under reduced pressure or by solvent extraction from the ionic liquid with diethyl ether. However, when recycling of the ionic liquid solution was attempted for the carbonylation of 3-butyn-l-ol the yield fell from 99 to 37% after only two runs. 

An interesting case of a polydentate ligand is the 2,6-bis(diphenylphosphino)pyridine.m It reacts with Ag(I) salts of the type [Ag(NCCH3)4](C104) to form polymer 133. The N-atom remains uncoordinated. 

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