The preparation and complexation of 5,10-bis(diphenylphosphino)phenazine

Abstract

Reaction of 5,10-dihydrophenazine with two equivalents of Ph 2PCl, in the presence of n-BuLi at −78 °C in thf gives Ph 2PN(C 6H 4)(C 6H 4)NPPh 2 ( 1) 1 Ph 2 PN ( C 6 H 4 )( C 6 H 4 ) NPPh 2 ( 1). To a −78 °C thf (40 ml) solution of 5,10-dihydrophenazine (1.053 g, 5.78 mmol) was added dropwise a hexane solution of BuLi (4.8 ml, 2.5 mol dm −3, 12.08 mmol). The mixture was stirred at −78 °C for 1 h and another 30 min at room temperature. The reaction solution was cooled to −78 °C again and to it was added dropwise a solution of diphenylchlorophosphine (2.1 ml, 2.613 g, 11.84 mmol) in thf (10 ml) over 40 min. Stirring was continued for another 1 h at −78 °C and overnight at room temperature. The solution was evaporated to dryness in vacuo and dichloromethane (30 ml) was added. Lithium chloride, which precipitated, was removed by filtration under nitrogen and then the volatiles were evaporated in vacuo to leave a yellow solid. Yield: 2.896 g, 91%; Microanalysis: Found (Calcd) C 78.5 (78.5), H 5.1 (5.1), N 4.8 (5.1)%; 31P–{H} NMR (CDCl 3): 61.0 (s) ppm; Selected IR data (KBr): ν(PN) 951 cm −1; FAB + MS: m/z 550 [M], 551 [M+H +], 573 [M+Na +]. 1 which can be oxidised with selenium to Ph 2P(Se)N(C 6H 4)(C 6 H 4)NP(Se)Ph 2 ( 2) 2 Ph 2 P ( Se ) N ( C 6 H 4 )( C 6 H 4 ) NP ( Se ) Ph 2 ( 2). To a dry and degassed toluene (10 ml) solution of selenium (0.029 g, 0.36 mmol) was added solid Ph 2PN(C 6H 4)(C 6H 4)NPPh 2 (0.100 g, 0.18 mmol). The solution was heated to reflux for ca. 2–3 h and allowed to cool to room temperature. The solution was evaporated to dryness in vacuo and the solid was dissolved in dichloromethane (2 ml). The dichloromethane solution was filtered through Celite and diethyl ether (20 ml) was added. The white product was collected by suction filtration and washed with diethyl ether (2×10 ml). Yield: 0.112 g, 88%; Microanalysis: Found (Calcd) C 60.3 (61.0), H 3.8 (4.0), N 3.8 (4.0)%; 31P–{H}NMR (CDCl 3): 58.5 (s) ppm, 1J ( 77Se– 31P) 832 Hz; selected IR data (KBr): ν(PN) 973 cm −1, ν(PSe) 565 cm −1; FAB + MS: m/z 708 [M], 709 [M+H] +. 2 or coordinated with Pt(II) in cis-[PtCl 2{Ph 2PN(C 6H 4)(C 6H 4)NPPh 2}] ( 3) 3 cis- [ PtCl 2 { Ph 2 PN ( C 6 H 4 )( C 6 H 4 ) NPPh 2 }] ( 3). To a dichloromethane (5 ml) solution of [PtCl 2(cod)] (0.068 g, 0.18 mmol) was added solid Ph 2PN(C 6H 4)(C 6H 4)NPPh 2 (0.100 g, 0.18 mmol) and the colourless solution stirred for ca. 2–3 h. The solution was concentrated under reduced pressure to ca. 1 ml and diethyl ether (10 ml) added. The white product was collected by suction filtration and washed with diethyl ether (2×10 ml). Yield: 0.118 g, 80%; Microanalysis: Found (Calcd) C 53.0 (53.0), H 3.4 (3.5), N 3.3 (3.4)%; 31P–{H} NMR (CDCl 3): 43.3 (s) ppm, 1J ( 195Pt– 31P) 3854.6 Hz; selected IR data (KBr): ν(PN) 949 cm −1, ν(PtCl) 311 and 291 cm −1; FAB +MS: m/z 781 [M–Cl −], 839 [M+Na +], 816 [M]. 3 The structure of 3 reveals a severely distorted (non-planar) phenazine backbone.