CRYSTALLINE BINUCLEAR CIS-CHLOROTIN(II) AND TRANS-CHLOROTIN(II) AMIDES [SN(MU-CL)(NR2)]2, THE CIS-1A REVERSIBLE TRANS-1B ISOMERIZATION FOR [NR2 = NCME2(CH2)3CME2], AND THE X-RAY STRUCTURES OF 1A AND OF TRANS-[SN(MU-CL)(N(SIME3)2)]2

Crystalline binuclear chlorotin(II) amides [Sn(mu-Cl)(NR2)]2 have been X-ray characterised as cis-[NR2 = Activated NCMe2(CH2)3CMe2, 1a] and trans-(R = SiMe3, 2b) conformers [Cl-Sn-Cl' = 78.53(4) 1a or 81.33(4)-degrees 2b, Sn-Cl-Sn' 100.91(4) 1a or 98.67(4)-degrees 2b, < Sn-Cl > 2.74 1a or 2.67 angstrom 2b]; a solution of 1 in toluene undergoes rapid cis reversible trans exchange at ambient temperature, but distinct cis-1a and trans-1b forms coexist below 192 K (Sn-119 NMR spectroscopy and line-shape analysis) and evidence is presented for an intramolecular mechanism for this exchange.