Chemistry of Diazaphospholephosphines. 1. Preparation of Substituted 4-(Phosphino)-2,5-dimethyl-2 H -1,2,3σ 2 -diazaphospholes, Bifunctional Phosphines with Dicoordinate and Tricoordinate Phosphorus(III) Centers. Chromium(0) and Molybdenum(0) Difluorophosphine Complexes (original) (raw)

1999, Inorganic Chemistry

An improved preparation of 4-(dichlorophosphino)-2,5-dimethyl-2H-1,2,3σ 2-diazaphosphole (1) is described. Replacement of the two chlorine substituents with two fluorine (2), dimethylamino (3), diethylamino (4), bis(npropyl)amine (5), pyrazole (9), 3,5-dimethylpyrazole (10), 2,2,2-trifluoroethoxy (11), phenoxy (12), pentafluorophenoxy (13), 2,6-difluorophenoxy (14), and pentafluorobenzoxy (15) substituents has been accomplished to create a large suite of potentially bifunctional phosphorus(III) ligands with two-and three-coordinate P centers spanning a range of basicity and steric bulk at the exo-phosphorus center. Bulky secondary amines (such as diisopropylamine, dibenzylamine, and iminodibenzyl) replaced only one chlorine atom to give asymmetric 4-(chloroaminophosphino)-2,5-dimethyl-2H-1,2,3σ 2-diazaphospholes (6, 7, and 8, respectively). The asymmetric substitution creates a diastereotopic center in both 6 and 7 which is observed as fluxional NMR behavior at room temperature. Similar diastereotopic induced behavior was observed in the substituent methylene protons of 11. Coordination studies of the fluorinated phosphole (L) 2) with Cr(0) and Mo(0) gave Cr(CO) 5 L (16), cis-Mo-(CO) 4 L 2 (17), and fac-Mo(CO) 3 L 3 (18) (where L) 4-(difluorophosphino)-2,5-dimethyl-2H-1,2,3σ 2-diazaphosphole). The fluoro ligand displays a behavior which is similar to that of PF 3 and phosphites.