Phospholes dithienophosphole

Two types of symmetric fused dithienophospholes exist, which differ according to the position of the S atoms as illustrated by compounds (53) [54] and (54) [50] (Scheme 15). The a A -dithieno[3,2-fo 2, 3 -d]phosphole (55) has recently been considered as a potential subunit for the construction of n-conjugated materials [55] (Scheme 15). Exploitation of the reactivity of the nucleophilic P-atom of (55) allows access to derivatives (56) and complexes (57) (Scheme 15). The absorption and emission behaviour of these species varies with the nature of the P-moieties. Upon oxidation of the P-centre of (55),bathochromic shifts of Ajnax Aejn were observed Aj ax 344 nm for (55) and ca. 373 nm for (56), and Agjn 422 nm for (55) and ca. 460 nm for (56) [55]. These results nicely illustrate... 

Dibenzophospholes A and dithienophospholes B and C (Fig. 4.7) do not display the typical electronic properties and reactivity patterns of phospholes, since the dienic system is engaged in the delocalized benzene or thiophene sextet [7, 10a, 51]. In fact, these building blocks have to be regarded as nonflexible diaryl-phosphines or as P-bridged diphenyl or dithienyl moieties. 

One remarkable example of the reactivity of a phosphole P-substituent is the radical copolymerization of dithienophosphole 146 with styrene using 2,2,6,6-tetramethylpiperidinyl-l-oxy (TEMPO) as the initiator (Scheme 42) <2004AGE6197>. Copolymers 48 are high molecular weight materials with relatively narrow poly-dispersities. They have been characterized by H, and P NMR spectroscopy. 

Figure 12.2 Dithienophosphole (1) and related benzannelated phosphole systems (2).

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