A 2,2′-bipyridyl calcium complex: synthesis, structure and reactivity studies

A 2,2′-bipyridyl calcium complex based on a tridentate ligand [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]Ca(bipy)(THF) ( 1 ) was prepared by the reduction of {[CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]CaI(THF)} 2 with potassium graphite in the presence of 2,2′-bipyridine (bipy). Complex 1 is a good Ca( i )synthon, as shown by its reactivity with I 2 , PhCH 2 SSCH 2 Ph, PhCH 2 SeSeCH 2 Ph and 9-fluorenone, yielding the calcium iodide complex [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]CaI(bipy) ( 2 ), calcium thiolate [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]Ca(SCH 2 Ph)(bipy) ( 3 ), calcium selenolate [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]Ca(SeCH 2 Ph)(bipy) ( 4 ), and calcium ketyl complex [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]Ca[O-(9-C 13 H 8 &z.rad;)](bipy)·2THF ( 5 ·2THF), respectively. In addition, reactions of complex 5 with CS 2 , CH 2 &z.dbd;CHCH 2 Br and PhCH 2 Br give the corresponding dimeric bis(thiolate) complex {[S 2 CC(CMe(NAr))C(Me)NCH 2 CH 2 NMe 2 ]Ca(DME)} 2 ( 6 ), dimeric calcium bromide complex {[(9-CH 2 &z.dbd;CHCH 2 -C 13 H 8 -9)-O]CaBr(THF)(bipy)} 2 ( 7 ) and {[(9-C 6 H 5 CH 2 -C 13 H 8 -9)-O]CaBr[O-(9-C 13 H 8 )](bipy)} 2 ( 8 ). These results demonstrated that the calcium ketyl complex 5 can also be employed as a single-electron transfer reagent. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses. The first example of a 2,2′-bipyridyl radical calcium complex, [CH 3 C(N-2,6- i Pr 2 C 6 H 3 )CHC(CH 3 )NCH 2 CH 2 N(CH 3 ) 2 ]Ca(bipy)(THF), was prepared and characterized and was shown to react as a calcium( i ) synthon.