Synthesis and some coordination chemistry of the PSnP pincer-type stannylene Sn(NCH 2 P t Bu 2 ) 2 C 6 H 4 , attempts to prepare the PSiP analogue, and the effect of the E atom on the molecular structures of E(NCH 2 P t Bu 2 ) 2 C 6 H 4 (E = C, Si, Ge, Sn)

The non-donor-stabilized PSnP pincer-type stannylene Sn(NCH P Bu ) C H (1) has been prepared by treating SnCl with Li (NCH P Bu ) C H . All attempts to synthesize the analogous PSiP silylene by reduction of the (previously unknown) silanes SiCl (NCH P Bu ) C H (2), SiHCl(NCH P Bu ) C H (3) and SiH(HMDS)(NCH P Bu ) C H (4; HMDS = N(SiMe ) ) 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(NCH P Bu ) C H (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 EN C H 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 EN C H 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{κ Sn,P-SnCl(NCH P Bu ) C H }(η -cod)] (5), [RuCl{κ Sn,P-SnCl(NCH P Bu ) C H }(η -cym)] (6) and [IrCl{κ Sn,P-SnCl(NCH P Bu ) C H }(η -C Me )] (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 κ Sn,P-chelating ligand, maintaining an uncoordinated phosphane fragment. X-ray diffraction data (of 6), P{ H} 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.