Role of Bis(phosphinimino)methanides as Universal Ligands in the Coordination Sphere of Metals across the Periodic Table

Electrosynthesis of iminophosphoranes and applications in nickel catalysis

“…Given that the modified Kirsanov reaction uses Br 2 to oxidize PPh 3 to Ph 3 PBr 2 followed by amination to access iminophosphoranes, 11 we explored using bromide-containing electrolytes to effect an anodic generation of Br 2 to mediate the oxidation of Ph 3 P (2a) in the presence of cyanamide (3) ( Scheme 3A ). The use of Et 4 NBr as an electrolyte enabled oxidation of PPh 3 in 4 : 1 (v/v) MeCN/MeOH provided 15% yield of 1a when using a graphite anode, a stainless-steel cathode along with guanidine 4 in 12% yield.…”

“…For example, synthesis through Staudinger reaction 22 involves the use of azides which are potentially explosive, and requires one or more steps to access the requisite azide. Other approaches to iminophosphoranes include the Kirsanov reaction 23 starting from hazardous PCl 5 , and the modified Kirsanov reaction, 11,24 which relies on a two-step bromination–amination process of a phosphine. Other approaches exist with limited scope, such aminations facilitated by diethylazodicarboxylate, 25 which is also a hazardous and shock-sensitive reagent.…”

“… 10 P N based structures such as iminophosphoranes are known but represent an underutilized class of ligands in earth-abundant metal catalysis. 11 There are exciting results of utilizing iminophosphoranes as ligands in catalytic cross-coupling reactions ( e.g. , Sonogashira, 12 Suzuki-Miyaura, 13 Kumada, 14 and Negishi couplings 14 b ) and hydrogenations of alkene, 15 and ketones, 16 cyclopropanation, 17 alkene oligo- and polymerizations, 18 ring opening polymerizations ( e.g.…”

“…lactide, ε-caprolactone), 19 as well as in organocatalysis, 20 amongst others. 11 Scheme 1 illustrates a selection of these examples. Iminophosphoranes have also been used as organic neutral super-electron donors in organic synthesis.…”