Mono‐ and Diprotonation of the Superbasic Bisguanidine 1,2‐Bis( N , N , N′ , N′ ‐tetramethylguanidino)benzene (btmgb) and Pt II and Pt IV Complexes of Chelating Bisguanidines and Guanidinates

New Pt complexes of chelating bisguanidines and guanidinate ligands were synthesized and characterized. 1,2‐Bis( N , N , N′ , N′ ‐tetramethylguanidino)benzene (btmgb) was used as a neutral chelating bisguanidine ligand, and 1,3,4,6,7,8‐hexahydro‐2 H ‐pyrimido[1,2‐ a ]pyrimidinate (hpp − ) as a guanidinate ligand. The salts [btmgbH] + [HOB(C 6 F 5 ) 3 ] − and [btmgbH 2 ]Cl 2 and the complexes [(btmgb)PtCl 2 ], [(btmgb)PtCl(dmso)] + [PtCl 3 (dmso)] − , and [(btmgb)PtCl(dmso)] + [Cl − ] were synthesized and characterized. In the [btmgbH] + cation the proton is bound to only one N atom. In the other complexes, both imine N atoms are coordinated to the Pt II , thus adopting a η 2 ‐coordinational mode. The hpp − anion, which usually prefers a bridging binding mode in dinuclear complexes, is η 2 ‐coordinated in the Pt IV complex [(η 2 ‐hpp)(hppH)PtCl 2 {N(H)C(O)CH 3 }], which is formed (in low yield) by reaction between cis ‐[(hppH) 2 PtCl 2 ] and H 2 O 2 in CH 3 CN.