SYNTHESIS AND STRUCTURE OF TETRAORGANOGUANIDINYL-SUBSTITUTED PHOSPHORUS-HALOGEN COMPOUNDS AND OF TRIS-N-(N′,N′,N″,N″-TETRAMETHYL) GUANIDINYL-PHOSPHONIUM SALTS

Abstract

The N-(N′,N′,N′,N′-tetraorgano)guanidine-substituted dichlorophosphines 3a - 3c were prepared by the reaction of phosphorus trichloride with the corresponding guanidine or N-lithiated guanidine. The high-field shift of the α(³¹P) values of 3a - 3c reflects the strong electron-donating effect of the guanidinyl substituents. Attempts to achieve further substitution of chlorine in PCl₃ by N′,N′,N′,N′-tehamethylguanidine (HTMG) 1a (employed as such or as its N-trimethylsilyl derivative, TMSTMG, 2) led to the formation of tris-N-(N′,N′,N′,N′-tetramethyl)guanidinylphosphonium salts such as 4. A salt containing the same cation was obtained from the reaction of bis-N-(N′,N′,N′,N′-tetramethyl)guanidinyltrichlorophosphorane 5 with magnesium. Difluoro-N-(N′,N′,N′,N′-tetramethyl)guanidinylphosphine 6 was obtained from difluorochlorophosphine and HTMG 1a. Hydrolysis of 6 led, depending upon the conditions of the reaction, either to N′,N′,N′,N′-tetramethylguanidinium phosphonofluoridate 7 or tris-N-(N′N,N′,N′-tetramethyl)guanidinylphosphonium pentafluorophosphate 8. A single crystal X-ray structure determination of 8 revealed a disordered anion and a cation with short P-N bonds, attributed to pπ-dπ: interaction. Dimethylamino-bis-N-(N′,N′,N′,N′-tetramethyl)guanidinyl-phosphine 9 and the chloro-diorganoamino-N-(N′,N′,N′,N′-tetramethyl)guanidinyl-phosphines 10 and 11 were obtained from the corresponding dichlorodiorganoaminophosphines and HTMG 1a or N-trimethylsilyl-(N′,N′,N′,N′-tetramethyl)guanidine 2.

Key Words:

• N′,N′,N′,N′-Tetramethylguanidine
• Phosphine
• N-(N′,N′,N′,N′-tetraorgano)-guanidinyl-substituted, Phosphonium salt
• N-(N′,N′,N′,N′-tetramethyl)-guanidinyl-substituted
• Phosphorane
• N-(N′,N′,N′,N′-tetramethyl)-guanidinylsubstituted
• Pentafluorophosphate anion
• Crystal structure