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

Abstract

An improved preparation of 4-(dichlorophosphino)-2,5-dimethyl-2H-1,2,3sigma(2)-diazaphosphole (1) is described. Replacement of the two chlorine substituents with two fluorine (2), dimethylamino (3), diethylamino (4), bis(n-propyl)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-1,2,3sigma(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-1,2,3sigma(2)-diazaphosphole). The fluoro ligand displays a behavior which is similar to that of PF(3) and phosphites.