The influence of the alkyl-substituted phosphanes (o-methylphenyl)diphenylpliosphane (o-MeP), (o-ethylphenyl)diphenylphosphane (o-EtP), bis(o-methylphenyl)phenylphosphane (o-Me2P), bis(o-ethylphenyl)phenylphosphane (o-Et2P), and (2,4,5-trimethylphenyl)diphenylphosphane (2,4,5-MeP) was screened in model reaction of rhodium-catalyzed 1-hexene hydroformylation. Compared with PPh3, the prepared phosphanes afforded lower chemoselectivity towards aldehydes, but increased the normal to branched ratio. Catalyst results are discussed in relation to stereoelectronic properties of the phosphane ligands. Electron donor capacity of the ligands was studied in terms of spectroscopic data of the trans-RhCl(CO)P-2 species, formed in reaction between Rh-2 (mu -Cl)(2)(CO)(4) and the ligands (P). Furthermore, steric attributes of free and bound phosphanes were investigated by Tolmans cone angle method. Crystal structures for ligands o-EtP, o-Me2P, o-Et2P, and complexes trans-Rh(CO)Cl(o-MeP)(2) and irans-Rh(CO)Cl(o-Et2P) were solved as well.