Synthesis and structures of new oxidation/cycloaddition products of λ < sup > 3 < /sup > -cyclodiphosphazanes

Abstract

Reaction of the cyclodiphosphazane [(OC4H8N)P(μ-N- t-Bu)2P(HN-t-Bu)] (1) with an equimolar quantity of diisopropyl azodicarboxylate afforded the phosphinimine product [(OC4H 8N)P(μ-N-t-Bu)2P=N-t-Bu)(N(CO2 -i-Pr)NHCO2-i-Pr] (6) having a PIII-N-PV skeleton. Similar products [(t-BuNH)P(μ-N-t-Bu)2P=N-t-Bu)(N- (CO2Et)NHCO2Et] (7) and [(CO2-i-Pr)HNN(CO 2-i-Pr)](t-BuN= P(μ-N-t-Bu)2POCH2CMe 2CH2O[P(μ-N-t-Bu)2P=N-t-Bu)(N(CO 2-i-Pr)NH(CO2-i-Pr)] (8) were spectroscopically characterized in the reaction of [(t-BuNH)P-N-t-Bu]2 (2) and [(t-BuNH)P(μ-N-t-Bu)2POCH2CMe2CH 2OP(μ-N-t-Bu)2P(NH-t-Bu)] (3) with diethyl- and diisopropyl azodicarboxylate, respectively. By contrast, the reaction of [(μ-t-BuN)P]2[O-6-t-Bu-4-Me-C6H2] 2CH2 (4) and [(C5H10N)P-μ-N-t-Bu] 2 (5) with diisopropyl azodicarboxylate afforded the mono- and bis-oxidized compounds [(O)P(μ-N-t-Bu)2P][O-6-t-Bu-4-Me-C 6H2]2CH2 (9) and [(C 5H10N)(O)P-μ-N-t-Bu]2 (10), respectively. Oxidative addition of o-chloranil to 7 and its DIAD analogue [(t-BuNH)P(μ-N-t-Bu)2P=N-t-Bu)(N(CO2-i-Pr)NHCO 2-i-Pr] (11) afforded [(C6Cl4-1,2-O 2)(t-BuNH)P(μ-N-t-Bu)2P=N-t-Bu)(N(CO 2R)NHCO2R] [R = Et (12) and i-Pr (13)] containing tetra- and pentacoordinate PV atoms in the cyclodiphosphazane ring. The structures of 6, 9, 12 and 13 have been confirmed by X-ray structure determination. For comparison, the X-ray structure of the double cycloaddition product [(C6Cl4-1,2-O2)(t-BuNH)PN-t-Bu] 2 (14), obtained from the reaction of 2 with two mole equivalents of o-chloranil is also reported.