Bis(guanidinate) titanium imido complexes [{(Me2N)C(NiPr)2}2TiNAr'] (Ar' = 2,6-Me2C6H3 (1a); C6F5 (1b)) are competent catalysts for the guanylation of a variety of arylamines with carbodiimide. The reversible [2 + 2] addition of iPrN=C=NiPr to 1b is demonstrated and is proposed to be part of the catalytic cycle. Compounds 1a and 1b are also effective precatalysts for the transamination of trialkylguanidines with arylamines to yield aryldialkylguanidines.

Lithium hexamethyldisilazide (LiN(SiMe 3 ) 2 ) is an excellent precatalyst for the room-temperature guanylation of a Variety of aryl amines with carbodiimides and for the C-C coupling reaction between terminal alkynes and carbodiimides to yield propiolamidines. Tetramethylethylenediamine (TMEDA), presumably through modulation of the lithium coordination sphere, increases the reactiVity of this catalyst system.

A family of N,N‘-disubstituted perimidinium cation salts were employed as precursors to persistent monomeric carbenes with novel molecular architectures and electronic structures. Depending on the substituents, reaction of these 1,3-disubstituted perimidinium cations with LiN(SiMe3)2 led either to deprotonation and generation of new carbenes or to enetetramines. In addition to spectroscopic characterization, crystallographic analysis of C10H6( i PrN)2C (10), C10H6( i PrN)(Me3CCH2N)C (11), {C10H6[N(3,5-Me2C6H3)]2C}2 (13), and C10H6( i PrN)(3,5-Me2C6H3N)C (14) definitively confirmed the nature of these species. The mixed benzyl/cycloheptyl-substituted carbene C10H6(cyclo-C7H13N)(p-MeC6H4CH2N)C (17) was observed to undergo dimerization upon heating to yield both cis and trans isomers of the enetetramine {C10H6(cyclo-C7H13N)(p-MeC6H4CH2N)C}2, (17) 2 . Rhodium complexes of these perimidine-based carbenes were accessed via reactions with either monomeric carbene or enetetramine. Spectroscopic and crystallographic analysis of these rhodium−carbene complexes revealed the sterically demanding nature of the carbene ligands, which is manifested in the observation of hindered Rh−Ccarbene bond rotation and through %V bur measurements, and their exceptional electron-donating ability.

A simple and convergent synthetic strategy used to increase the diversity of the carbodicarbene ligand framework through incorporation of unsymmetrical pendant groups is reported. Structural analysis and spectroscopic studies of ligands and their Rh complexes are reported. Reactivity studies reveal carbodicarbenes as competent organocatalysts for amine methylation using CO2 as a synthon. A unique BH-activated boron-carbodicarbene complex was isolated as a reaction intermediate, providing mechanistic insight into the CO2 functionalization process.