Phosphorus centers of different hybridization in phosphaalkene-substituted phospholes.

ABSTRACT: Phosphole-substituted phosphaalkenes (PPAs) of the general formula Mes*P=C(CH(3))-(C(4)H(2)P(Ph))-R 5?a-c (Mes*=2,4,6-tBu(3)Ph; R=2-pyridyl (a), 2-thienyl (b), phenyl (c)) have been prepared from octa-1,7-diyne-substituted phosphaalkenes by utilizing the Fagan-Nugent route. The presence of two differently hybridized phosphorus centers (?(2) ,?(3) and ?(3) ,?(3)) in 5 offers the possibility to selectively tune the HOMO-LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5?a-c by sulfur proceeds exclusively at the ?(3) ,?(3) -phosphorus atom, thus giving rise to the corresponding thioxophospholes 6?a-c. Similarly, 5?a is selectively coordinated by AuCl at the ?(3),?(3) -phosphorus atom. Subsequent second AuCl coordination at the ?(2),?(3) -phosphorus heteroatom results in a dimetallic species that is characterized by a gold-gold interaction that provokes a change in ? conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO-LUMO gap relative to reference phosphole-containing ? systems that lack a P=C substituent.

SUBMITTER: Oberg E 

PROVIDER: S-EPMC4506554 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature