Two Successive Steps of Hypercoordination at Tin: The Gas-Phase and Solid-State Structures of (N,N-Dimethylaminoxy)trimethylstannane

Abstract

Me3SnONMe2 has been prepared from trimethyltin chloride and O-lithio-N,N-dimethylhydroxylamine and characterized by IR and NMR spectroscopy, mass spectrometry, and elemental analysis. Its gas-phase molecular structure has been determined by electron diffraction augmented by restraints taken from ab initio calculations at the MP2/DZ(P) level of theory. A secondary interaction (Sn···N, 2.731(14) Å) between the tin and nitrogen atoms has been detected and makes Me3SnONMe2 the first partially hypercoordinate tin compound studied in the gas phase. A solid-state structure of Me3SnONMe2 has been determined by X-ray diffraction of an in situ grown single crystal. In the crystal lattice the coordination sphere of tin is further enlarged by a weak intermolecular Sn···O contact (2.998(10) Å) and a 4+2 coordination geometry is achieved, which can be deduced from that of a distorted trigonal bipyramid with one of the axial substituents replaced by the two weak contacts. Important geometry parameter values are as follows (gas/solid): Sn−O 2.006(3)/2.063(6) Å, O−N 1.468(6)/1.440(9) Å, Sn−C(in plane) 2.148(4)/2.163(14) Å, Sn−C(out of plane) 2.146(3)/2.062(9) and 2.185(10) Å, Sn−O−N 102.5(8)/101.5(4)°, O−Sn−C(in plane) 99.6(10)/99.7(4)°, O−Sn−C(out of plane) 108.1(6)/119.6(4)° and 116.6(4)°.