The influence of the methyl substituents at C2 carbon of Thiosemicarbazones {R1R2C2 =N3-N2H-C1(=S)N1H2) on bonding and structures of copper(I) complexes

Reaction of copper(I) halides with acetone thiosemicarbazone (Hactsc) and acetaldehyde thiosemicarbazone (Hmtsc) in CH3CN in the presence of PPh3 has formed dimeric complexes of type, [Cu-2(mu-X)(2)(eta(1)-S-Htsc)(2)(Ph3P)(2)] (Htsc: X; Hmtsc, Br, 1; I, 2; Hactsc, I, 3; Cl, 5), and a monomer, [CuBr((eta(1)-S-Hactsc)(Ph3P)(2) (4). The complexes have been characterized using analytical data, spectroscopy and X-ray crystallography (1-4). The presence of methyl substituents at C-2 carbon of thiosemicarbazone seems to alter inter- and intra-molecular hydrogen bonding. Intermolecular and intramolecular interactions by amino and imino hydrogen atoms respectively with bridging halogen atom shorten X-Cu-X bond angle, and open up Cu-X-Cu bond angle, resulting in longer Cu center dot center dot center dot Cu separation (3.50-3.61 angstrom) in complexes 1-3.