PENTACOORDINATED MOLECULES .39. A NEW GEOMETRICAL FORM FOR TIN - SYNTHESIS AND STRUCTURE OF THE SPIROCYCLIC COMPLEX [(CH3)(4)N][(C7H6S2)2SNCL] AND THE RELATED MONOCYCLIC DERIVATIVE [(C2H5)(4)N][(C7H6S2)PH(2)SNCL] (REPRINTED FROM INORG CHEM, VOL 20, PG 3076, 1981)

The synthesis and X-ray structure of the tetramethylammonium chloride adduct of the spirobi(dithiolato)stannate(IV), [(CH3)(4)N](+)[(C7H6S2) (2)SnCI](-), (2), provide the first example of a tin compound having a discrete rectangular-pyramidal geometry. The synthesis and X-ray stru cture of the related monocyclic derivative [(C2H5)(4)N](+)[(C7H6S2)Ph( 2)SnCI](-) (4) shows tin to possess a trigonal-bipyramidal geometry. 2 crystallizes in the monoclinic space group Cc, with a = 14.126 (4), b = 11.385 (6) Angstrom, c = 14.609 (5) Angstrom, beta = 100.37 (3)degr ees, and Z = 4. 4 crystallizes in the monoclinic space group P2(1)/c, with a = 12.344 (4) Angstrom, b = 11.975 (5) Angstrom, c = 19.120 (5) Angstrom, beta = 96.41 (2)degrees, and Z = 4. Data for both compounds were collected on an Enraf-Nonius CAD 4 automated diffractometer out t o a maximum 2<theta(Mo<K(alpha)over bar>) of 50 degrees. The final con ventional unweighted residuals were 0.039 and 0.048 for 2 and 4, respe ctively. It is shown that the Sn-119m Mossbauer quadrupole splitting p arameter is useful in distinguishing the square (or rectangular) pyram id from the trigonal bipyramid. Comparison of pentacoordinated tin(IV) with pentacoordinated germanium(IV) and phosphorus shows that the kno wn rectangular pyramids have spirocyclic systems as a common structura l feature.