Synthesis and some coordination chemistry of the PSnP pincer-type stannylene Sn(NCH2PtBu2)(2)C6H4, attempts to prepare the PSiP analogue, and the effect of the E atom on the molecular structures of E(NCH2PtBu2)(2)C6H4 (E = C, Si, Ge, Sn)

摘要

The non-donor-stabilized PSnP pincer-type stannylene Sn((NCH2PBu2)-Bu-t)(2)C6H4 (1) has been prepared by treating SnCl2 with Li-2((NCH2PBu2)-Bu-t)(2)C6H4. All attempts to synthesize the analogous PSiP silylene by reduction of the (previously unknown) silanes SiCl2((NCH2PBu2)-Bu-t)(2)C6H4 (2), SiHCl((NCH2PBu2)-Bu-t)(2)C6H4 (3) and SiH(HMDS)((NCH2PBu2)-Bu-t)(2)C6H4 (4; HMDS = N(SiMe3)(2)) have been unsuccessful. The almost planar (excluding the tert-butyl groups) molecular structure of stannylene 1 (determined by X-ray crystallography) has been rationalized with the help of DFT calculations, which have shown that, in the series of diphosphanetetrylenes E((NCH2PBu2)-Bu-t)(2)C6H4 (E = C, Si, Ge, Sn), the most stable conformation of the compounds with E = Ge and Sn has both P atoms very close to the EN2C6H4 plane, near (interacting with) the E atom, whereas for the compounds with E = C and Si, both phosphane groups are located at one side of the EN2C6H4 plane and far away from the E atom. The size of the E atom and the strength of stabilizing donor-acceptor PE interactions (both increase on going down in group 14) are key factors in determining the molecular structures of these diphosphanetetrylenes. The syntheses of the chloridostannyl complexes [Rh{Sn-2,P-SnCl((NCH2PBu2)-Bu-t)(2)C6H4}((4)-cod)] (5), [RuCl{Sn-2,P-SnCl((NCH2PBu2)-Bu-t)(2)C6H4}((6)-cym)] (6) and [IrCl{Sn-2,P-SnCl((NCH2PBu2)-Bu-t)(2)C6H4}((5)-C5Me5)] (7) have demonstrated the tendency of stannylene 1 to insert its Sn atom into M-Cl bonds of transition metal complexes and the preference of the resulting PSnP chloridostannyl group to act as a Sn-2,P-chelating ligand, maintaining an uncoordinated phosphane fragment. X-ray diffraction data (of 6), P-31{H-1} NMR data (of 5-7) and DFT calculations (on 6) are consistent with the existence of a weak PSn interaction involving the non-coordinated P atom of complexes 5-7, similar to that found in stannylene 1.