Diorganotin(IV) Complexes of Organoselenolato Ligands with Pyrazole Moieties—Synthesis, Structure and Properties

Diorganotin(IV) compounds of types RR'Sn(SeCH₂CH₂pz)₂ [R = R' = ⁿBu (<b>2</b>), Ph (<b>3</b>); R = 2-(Me₂NCH₂)C₆H₄, R' = Me (<b>4</b>), ⁿBu (<b>5</b>), Ph (<b>6</b>)], and RR'SnX(SeCH₂CH₂pz) [R = 2-(Me₂NCH₂)C₆H₄, R' = ⁿBu, X = Cl (<b>7</b>), R' = Me, X = SCN (<b>9</b>)], as well as [2-(Me₂NCH₂)C₆H₄](Me)Sn(NCS)₂ (<b>8</b>), and the tin(II) Sn(SeCH₂CH₂pz)₂ (<b>10</b>) (pz = pyrazole), were prepared by salt metathesis reactions between the appropriate diorganotin(IV) dichloride or dipseudohalide and Na[SeCH₂CH₂pz], with the latter freshly prepared from (pzCH₂CH₂)₂Se₂ (<b>1</b>). The solution behaviour of these compounds was investigated by multinuclear NMR (¹H, ¹³C, ⁷⁷Se, ¹¹⁹Sn), and the NMR spectra showed the existence of the Se-Sn bonds in solution. Compounds <b>4</b> and <b>5</b> showed decomposition in a solution of chlorinated solvents with the formation of selenium bridged dimeric species of type {[2-(Me₂NCH₂)C₆H₄](R')Se}₂ [R' = Me (<b>4-a</b>), ⁿBu (<b>5-a</b>)], as the single-crystal X-ray diffraction studies revealed, in contrast with compound <b>9,</b> for which a monomeric structure was observed with the desired composition. The solid state structures of <b>4-a</b>, <b>5-a</b>, <b>8</b>, and <b>9</b> revealed N→Sn intramolecular coordination of the nitrogen atom in the pendant CH₂NMe₂ arm. The NMR spectra suggested such a coordination at room temperature only for compound <b>7</b>.