IRON(II) COMPLEXES CONTAINING THE 1,2-DIPHOSPHOLANOETHANE LIGAND

The synthesis and crystal structure of cis-Fe(BPE5)(2)Cl-2 (BPE5 = 1,2 -diphospholanoethane). the first symmetrical cis-Fr(PP)(2)Cl-2 (PP = b identate phosphine), is reported (monoclinic. P2(1)/n, a = 12.084(3) A ngstrom, b = 14.059(2) Angstrom, c = 17.665(2) Angstrom, beta = 101.77 (1)degrees, Z = 4). The overall structure and Fe-P and Fe-CI bend leng ths of cis-Fe(BPE5)(2)Cl-2 more closely resemble those in Fe(PP3)Cl-2 complexes (PP3 = tripodal, tetradentate phosphine ligand) than in othe r Fe(PP)(2)Cl-2 complexes. In solution, cis-Fe(BPE5)(2)Cl-2 exhibits t emperature-dependent paramagnetic behavior due to reversible dissociat ion of chloride. The dissociation of chloride was exploited in the syn thesis of Fe(BPE5)(2)X-2 (X = Br, I) and [Fe(BPE5)(2)(L)(CI)](+). (L = CO, PMe3). The crystal structure of [cis-Fe(BPE5)(2)-(CO)(Cl)][BPh4] is reported (monoclinic, P2(1)/a, a = 12.938(3) Angstrom, b = 29.647(4 ) Angstrom, c = 13.131(3) Angstrom, beta = 107.89(2)degrees, Z = 4). T he relative chelation strength of BPES in Fe(PP)(2)Cl-2 complexes is B PE5 approximate to DMPE > DEPE > DPrPE [DMPE = 1,2-bis(dimethylphoshin o)ethane: DEPE = 1,2-bis(diethylphoshino)ethane; DPrPE = bis(di-n-prop ylphosphino)ethane].