Lithium Furyl and Pyridyl Amidinates as Building Blocks in Coordination Polymers, Ladder and Cage Structures

Lithium N,N′-bis(trimethylsilyl)heterocyclic amidinate complexes with 3- and 4-pyridyl and 3-furyl carbon substituents were prepared by addition of the corresponding nitriles to LiN(SiMe3)2 (LiNTMS2) solution. In the presence of N,N,N′,N′ tetramethylethylene diamine (TMEDA), both pyridyl amidinates crystallize as coordination polymers with an amidinate-Li-pyridyl backbone. The 4-pyridyl derivative (7) creates a linear polymer with amidinate-Li-TMEDA units as side chains, whereas the 3-pyridyl polymer (6) has a two-dimensional (2D) network structure in which TMEDA serves as a cross-linker. Solvation of the reaction mixture of 3-furonitrile and LiNTMS2 with TMEDA affords the monomeric 3-furyl amidinate Li TMEDA complex (3). Crystals of the Li2O complex {[3-furyl-C-(NTMS)2Li]4·Li2O}·C7H8 (4) are obtained from toluene by partial hydrolysis of the unsolvated 3-furyl amidinate (2). Degradation of the polymer (7) to monomeric units can be achieved by solvation in toluene or by reaction with TMS2NLi·TMEDA that affords crystals of the complex {NTMS2Li·[4-C5H4N−C(NTMS)2Li·TMEDA]}2·(NTMS2Li·TMEDA) (8). The formation of these aggregates can be rationalized by directed substitution of TMEDA with pyridyl moieties and by the laddering principle.