Functionalized bis(pyrazol-1-yl)methanes by organotin halide on the methine carbon atom and their related reactions

Abstract

The modification of bis(pyrazol-1-yl)methanes by organotin halide on the methine carbon atom has been successfully carried out, and their related reactions have also been studied. Bis(3,5-dimethylpyrazol-1-yl)(iododiphenylstannyl)methane [Ph 2ISnCH(3,5-Me 2Pz) 2] can be obtained by the selective cleavage of the Sn – C sp 2 bond in bis(3,5-dimethylpyrazol-1-yl)triphenylstannylmethane with I 2 in a 1:1 molar ratio, while {di( tert-butyl)chlorostannyl}bis(3,5-dimethylpyrazol-1-yl)methane [( t-Bu) 2ClSnCH(3,5-Me 2Pz) 2] and {di( tert-butyl)chlorostannyl}bis(3,4,5-trimethylpyrazol-1-yl)methane [( t-Bu) 2ClSnCH(3,4,5-Me 3Pz) 2] are easily prepared by the reaction of the bis(3,5-dimethylpyrazol-1-yl)methide or bis(3,4,5-trimethylpyrazol-1-yl)methide anion with di( tert-butyl)tin dichloride. The molecular structure of [( t-Bu) 2ClSnCH(3,5-Me 2Pz) 2] determined by X-ray structure analysis indicates that bis(3,5-dimethylpyrazol-1-yl)methide acts as a bidentate monoanionic κ 2-[C,N] chelating ligand. Reaction of these bis(pyrazol-1-yl)methanes functionalized by organotin halide with W(CO) 5THF results in the oxidative addition of the relative electrophilic Sn–X (X = Cl or I) bond instead of the Sn – C sp 3 bond to the tungsten(0) atom, yielding new metal–metal bonded complexes R 2SnCHPz 2W(CO) 3X (R = Ph or t-Bu, Pz represents substituted pyrazol-1-yl). Furthermore, treatment of the oxidative addition product ( t-Bu) 2SnCH(3,5-Me 2Pz) 2W(CO) 3Cl with n-BuLi results in known complex CH 2(3,5-Me 2Pz) 2W(CO) 4 with the loss of the organotin fragment. In addition, reaction of Ph 2ISnCH(3,5-Me 2Pz) 2 with 2-PySNa (Py = pyridyl) leads to the replacement of iodide by 2-PyS − anion to give Ph 2(2-PyS)SnCH(3,5-Me 2Pz) 2, which subsequently reacts with W(CO) 5THF to result in the decomposition of this ligand, also yielding the known bis(3,5-dimethylpyrazol-1-yl)methane derivative of CH 2(3,5-Me 2Pz) 2W(CO) 4.