Insertion reactions of six-membered cyclopalladated N,N′,N″- triarylguanidines, [κ2(C,N)Pd(μ-Br)]2 (III-V), with various alkynes in CH2Cl2 under ambient conditions afforded diinserted eight-membered palladacycles, [(κ2(C,N): η2(C=C)-PdBr] (1-11), in high yield (76-96%), while insertion reactions of six-membered cyclopalladated N,N′,N″-triarylguanidines, [κ2(C,N)Pd(Lewis base)Br] (VI-XI), with various alkynes under the aforementioned conditions afforded monoinserted six-membered palladacycles, [κ2(C,N)Pd(Lewis base)Br] (12-21), in high yield (81-91%) except for 14 (23%). The insertion reaction of VI with 2 equiv of dimethyl acetylenedicarboxylate (DMAD) and the insertion reaction of 12 with 1 equiv of DMAD in CH2Cl2 under ambient conditions resulted in the formation of a diinserted zwitterionic five-membered palladacycle, [κ2(C,C)Pd(2,6-lutidine)Br] (22), in 76% and 70% yields, respectively. Palladacycle 22 upon reaction with AgOTf in wet MeCN afforded the ionic palladacycle [κ2(C,C)Pd(2,6-lutidine)(H 2O)][OTf] (23) in 78% yield. The ring size of the "[κ2(C,N)Pd]" unit in the structurally characterized diinserted palladacycles (1·2CH2Cl2·H 2O, 2, 5, and 7), and monoinserted palladacycles (17, 18, and 20·C7H8·H2O) is smaller than that anticipated for mono- and diinserted palladacycles, and this feature is mainly ascribed to the proclivity of III-XI to undergo ring contraction cum amine-imine tautomerization upon alkyne insertion. Palladacycle 22 represents the first diinserted product obtained in alkyne insertion reactions of [κ2(C,N)Pd(Lewis base)X] type palladacycles. The molecular structure of 22·H2O determined by X-ray diffraction indicates that the positive charge on the guanidinium moiety is balanced by the negative charge on the palladium atom and thus represents the first structurally characterized zwitterionic palladacycle to be reported in alkyne insertion chemistry. Plausible mechanisms of formation of 12-21 and 22 have been outlined. The presence of more than one species in solution for some of the palladacycles in the series 1-7 and 12-21 was explained by invoking the C-N single-bond rotation of the CN3 unit of the guanidine moiety, while this process in conjunction with Pd-N(lutidine) bond rotation was invoked to explain the presence of four isomers of 15, as studied with the aid of variable- concentration 1H NMR experiments carried out for 14 and 15.