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The international journal for inorganic, organometallic and bioinorganic chemistry
Paper
Dalton Trans., 2009, 202 - 209, DOI: 10.1039/b815056g
Stereoelectronic effects in a homologous series of bidentate cyclic phosphines. A clear correlation of hydroformylation catalyst activity with ring size
Mairi F. Haddow, Ann J. Middleton, A. Guy Orpen, Paul G. Pringle and Rainer Papp
The homologous series of diphosphines (CH2)n-1P(CH2)3P(CH2)n-1 where n = 5 (L5), 6 (L6), or 7 (L7) have been synthesized from the corresponding PhP(CH2)n-1. Treatment of [PtCl2(cod)] with L5–7 gave the 6-membered chelates cis-[PtCl2(L5–7)], the crystal structures for which reveal that L5–7 have very similar steric bulk and bite angles. Treatment of [Rh2Cl2(CO)4] with L5–7 gave the binuclear trans-[Rh2Cl2(CO)2(
-L5–7)2] with syn and anti orientations of the CO and Cl ligands suggested by the 31P NMR spectra and the crystal structures of syn–trans-[Rh2Cl2(CO)2(-L5)2] and anti–trans-[Rh2Cl2(CO)2(-L7)2]. The 
(CO) values for trans-[Rh2Cl2(CO)2(-L5–7)2] indicate that the donor strength increases in the order L5 < L6 < L7. A study of rhodium-catalysed hydroformylation of 1-octene using diphosphines L5–7 is described. The catalyst activity decreases with increasing phosphacycle ring size: L5 > L6 > L7.
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