New binuclear complexes of three-coordinate Cu I have been synthesized with the ligand 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb). Subsequent oxidation of the ligand unit was achieved by reaction with Br 2 or I 2 . Reaction with Br 2 leads to oxidation of both the ligand and the copper ions and formation of a bicationic dinuclear Cu II complex. On the other hand, oxidation with I 2 leads only to oxidation of the ligand during the first step. A metastable coordination polymer of ladder-type structure results, in which the coordi-

Herein we report on the synthesis of the new strong N‐base and electron donor tdmegb [1,2,4,5‐tetrakis(N,N′‐dimethylethyleneguanidino)benzene]. Compared to the previously synthesized ttmgb [1,2,4,5‐tetrakis(tetramethylguanidino)benzene], this compound turned out to be a slightly better electron donor and a slightly weaker base. In experiments in which [AuCl(PPH3)] was dissolved in CH3CN together with tdmegb, we observed the formation of the first cyanomethyl complex of Au, namely [Au(CH2CN)(PPh3)] in good yield. This reaction does not take place for ttmgb. Moreover, in CH2Cl2 solutions containing the three components [AuCl(PPh3)], tdmegb and a nitrile (in large excess), only AuI reduction leading to a [Au11Cl3(PPh3)7] cluster is observed. Possible reaction mechanisms for this unusual reaction are discussed.

In this work we report on some aspects of the chemistry of the organic electron‐donor 1,2,4,5‐tetrakis(tetramethylguanidino)benzene (ttmgb). Reactions with electron acceptors and proton donors as well as late transition metals to give binuclear complexes (including a binuclear CuII complex with antiferromagnetic coupling through the bridging ttmgb ligand) are analysed. These studies shed some light on the electron‐donor/proton‐acceptor and coordination behaviour of this compound.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Reaction between the diborane (4) B2Cl2(NMe2)2 and Li(hpp) (hpp-=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) leads to [(Me2N)B(mu-hpp)] 2. This species can be protonated by HCl.OEt2 to give [(Me2HN)B(mu-hpp)]2Cl2 featuring two B(II) cations with direct B-B bonding. The unsymmetrical monocation [(Me2N)B2(mu-hpp)2(NHMe2)]+ is also obtained. [(Me2HN)B(mu-hpp)]2Cl2 eliminates NHMe2 in a slow reaction leading to [ClB2(mu-hpp)2(NHMe2)]Cl and ultimately, presumably, to [ClB(mu-hpp)]2. We report the crystal structures of the two monocations [ClB2(mu-hpp)2(NHMe2)]Cl and [(Me2N)B2(mu-hpp)2(NHMe2)]Cl. The experimental results are accompanied by some quantum chemical density-functional theory calculations.

In this work reactions between [AuCl(PPh 3 )] and HCϵCAr (Ar = phenyl, pyridinyl, biphenyl or p-acetylphenyl) in the presence of the nitrogen base and organic electron donor 1,2,4,5-tetrakis(N,NЈ-dimethyl-N,NЈ-ethyleneguanidino)benzene (1) were studied. Two different product types were isolated and characterised: the neutral Au