Chemistry of diazaphospholephosphines. 1. Preparation of substituted 4-(phosphino)-2,5-dimethyl-2H-1,2,3 sigma(2)-diazaphospholes, bifunctional phosphines with dicoordinate and tricoordinate phosphorus(III) centers. Chromium(0) and molybdenum(0) difluorophosphine complexes

An improved preparation of 4-(dichlorophosphino)-2,5-dimethyl-2H-1,2,3 sigm a(2)-diazaphosphole (1) is described. Replacement of the two chlorine subst ituents with two fluorine (2), dimethylamino (3), diethylamino (4), bis(n-p ropyl)amine (5), pyrazole (9), 3,5-dimethylpyrazole (10), 2,2,2-trifluoroet hoxy (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 diisopropyla mine, dibenzylamine, and iminodibenzyl) replaced only one chlorine atom to give asymmetric 4-(chloroaminophosphino)-2,5-dimethyl-2H 1,2,3 sigma(2)-dia zaphospholes (6, 7, and 8, respectively). The asymmetric substitution creat es a diastereotopic center in both 6 and 7 which is observed as fluxional N MR behavior at room temperature. Similar diastereotopic induced behavior wa s observed in the substituent methylene protons of Il. Coordination studies of the fluorinated phosphole (L = 2) with Cr(O) and Mo(O) gave Cr(CO)(5)L (16), cis-Mo(CO)(4)L-2 (17), and fac-Mo(CO)(3)L-3 (18) where L = 4-(difluor ophosphino)-2,5-dimethyl-2H-1,2 The fluoro ligand displays a behavior which is similar to that of PF3 and phosphites.