Synthesis, Structures, and Some Reactions of [(Thioacyl)thio]‐ and (Acylseleno)antimony and ‐bismuth Derivatives ((RCSS) x MR $\rm{_{{\bf 3 - }{\bf x}}^{\bf 1} }$ and (RCOSe) x MR $\rm{_{{\bf 3 - }{\bf x}}^{\bf 1} }$ with M = Sb, Bi and x = 1–3)

A series of [(thioacyl)thio]‐ and (acylseleno)antimony and [(thioacyl)thio]‐ and (acylseleno)bismuth, i.e. , (RCSS) x MR $\rm{_{3 - x}^1 }$ and (RCOSe) x MR $\rm{_{3 - x}^1 }$ (M = Sb, Bi, R 1  = aryl, x  = 1–3), were synthesized in moderate to good yields by treating piperidinium or sodium carbodithioates and ‐selenoates with antimony and bismuth halides. Crystal structures of (4‐MeC 6 H 4 CSS) 2 Sb(4‐MeC 6 H 4 ) ( 9b′ ), (4‐MeOC 6 H 4 COSe) 2 Sb(4‐MeC 6 H 4 ) ( 12c′ ), (4‐MeOC 6 H 4 COS) 2 Bi(4‐MeC 6 H 4 ) ( 15c′ ), and (4‐MeOC 6 H 4 CSS) 2 BiPh ( 18c ) along with (4‐MeC 6 H 4 COS) 2 SbPh ( 6b ) and (4‐MeC 6 H 4 COS) 3 Sb ( 7b ) were determined ( Figs. 1 and 2 ). These compounds have a distorted square pyramidal structure, where the aryl or carbothioato (= acylthio) ligand at the central Sb‐ or Bi‐atom is perpendicular to the plane that includes the two carbodithioato (= (thioacyl)thio), carboselenato (= acylseleno), or carbothioato ligand and exist as an enantiomorph pair. Despite the large atomic radii, the CS ⋅⋅⋅ Sb distances in (RCSS) 2 MR 1 (M = As, Sb, Bi; R 1  = aryl) and the CO ⋅⋅⋅ Sb distances in (RCOS) x MR $\rm{_{3 - x}^1 }$ (M = As, Sb, Bi; x  = 2, 3) are comparable to or shorter than those of the corresponding arsenic derivatives ( Tables 2 and 3 ). A molecular‐orbital calculation performed on the model compounds (MeC(E)E 1 ) 3− x MMe x (M = As, Sb, Bi; E = O, S; E 1  = S, Se; x  = 1, 2) at the RHF/LANL2DZ level supported this shortening of CE ⋅⋅⋅ Sb distances ( Table 4 ). Natural‐bond‐orbital (NBO) analyses of the model compounds also revealed that two types of orbital interactions n S  →  σ $\rm{_{{{MC}}}^\ast }$ and n S  →  σ $\rm{_{{{MS(1)}}}^\ast }$ play a role in the (thioacyl)thio derivatives (MeCSS) 3− x MMe x ( x  = 1, 2) ( Table 5 ). In the acylthio‐MeCOSMMe 2 (M = As, Sb, Bi), n O  →  σ $\rm{_{{{MC}}}^\ast }$ contributes predominantly to the orbital interactions, but in MeCOSeSbMe 2 , none of n O  →  σ $\rm{_{{{MC}}}^\ast }$ and n O  →  σ $\rm{_{{{MSe}}}^\ast }$ contributes to the orbital interactions. The n S  →  σ $\rm{_{{{MC}}}^\ast }$ and n S  →  σ $\rm{_{{{MS(1)}}}^\ast }$ orbital interactions in the (thioacyl)thio derivatives are greater than those of n O  →  σ $\rm{_{{{MC}}}^\ast }$ and n O  →  σ $\rm{_{{{ME}}}^\ast }$ in the acylthio and acylseleno derivatives (MeCOE) 3− x MMe x (E = S, Se; M = As, Sb, Bi; x  = 1, 2). ▪The reactions of RCOSeSbPh 2 (R = 4‐MeC 6 H 4 ) with piperidine led to the formation of piperidinium diphenylselenoxoantimonate(1−) (= piperidinium diphenylstibinoselenoite) (H 2 NC 5 H 10 ) + Ph 2 SbSe − , along with the corresponding N ‐acylpiperidine ( Table 6 ). Similar reactions of the bis‐derivatives (RCOSe) 2 SbR 1 (R, R 1  = 4‐MeC 6 H 4 ) with piperidine gave the novel di(piperidinium) phenyldiselenoxoantimonate(2−) (= di(piperidinium) phenylstibonodiselenoite), [(H 2 NC 5 H 10 ) + ] 2 (PhSbSe 2 ) 2− , in which the negative charges are delocalized on the SbSe 2 moiety ( Table 6 ). Treatment of RCOSeSbR $\rm{_2^1 }$ (R, R 1  = 4‐MeC 6 H 4 ) with N ‐halosuccinimides indicated the formation of Se ‐(halocyclohexyl) arenecarboselenoates ( Table 8 ). Pyrolysis of bis(acylseleno)arylbismuth at 150° gave Se ‐aryl carboselenoates in moderate to good yields ( Table 9 ).