Hypo-electronic triple-decker sandwich complexes: synthesis and structural characterization of [(Cp*Mo)₂{μ–η⁶:η⁶-B₄H₄E-Ru(CO)₃}] (E = S, Se, Te or Ru(CO)₃ and Cp* = η⁵-C₅Me₅)

Abstract

The syntheses and structural characterization of hypo-electronic di-molybdenum triple-decker sandwich clusters are reported. Thermolysis of [Ru3(CO)12] with an in situ generated intermediate obtained from the reaction of [Cp*MoCl4] with [LiBH4·THF] yielded an electron deficient triple-decker sandwich complex, [(Cp*Mo)2{μ-η(6):η(6)-B4H4Ru2(CO)6}], . In an effort to generate analogous triple-deckers containing group-16 elements, we isolated [(Cp*Mo)2{μ-η(6):η(6)-B4H4ERu(CO)3}] (: E = Te; : E = S; : E = Se). These clusters show a high metal coordination number and cross cluster Mo-Mo bond. The formal cluster electron count of these compounds is four or three skeletal electron pairs less than required for a canonical closo-structure of the same nuclearity. Therefore, these compounds represent a novel class of triple-decker sandwich complex with 22 or 24 valence-electrons (VE), wherein the "chair" like hexagonal middle ring is composed of B, Ru and chalcogen. One of the key differences among the synthesized triple-decker molecules is the puckering nature of the middle ring [B4RuE], which increases in the order S < Se < Ru(CO)3 < Te. In addition, Fenske-Hall and quantum-chemical calculations with DFT methods at the BP86 level of theory have been used to analyze the bonding of these novel complexes. The studies not only explain the electron unsaturation of the molecules, but also reveal the reason for the significant puckering of the middle deck. All the compounds have been characterized by IR, (1)H, (11)B, and (13)C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis.

Chemistry of Triple‐Decker Sandwich Complexes Containing Four‐Membered Open B2E2 Rings (E = S or Se)

“…Examples of metallaheteroborane clusters with heavier group 16 elements, especially Te, are limited. [14d], Thus, to isolate the tellurium analogue of nido ‐ 1 , we have performed the reaction of [Cp*CoCl] 2 and [LiBH 4 · THF], followed by thermolysis with Te powder. In contrast to the earlier results, this reaction leads to the formation of nido ‐[(Cp*Co) 2 B 5 H 5 Te 2 ], 5 , and [(Cp*Co) 2 B 4 H 6 ] (Scheme ).…”

“…For example, group 6 dimetallaheteroboranes [(Cp*Mo) 2 B 4 H 5+ m Cl n E][11c], [12a] (E = Te, m = 0, n = 1; E = S or Se, m = 1, n = 0) show diverse reactivity patterns towards many metal–carbonyl compounds, yielding metallaheteroboranes containing six‐membered middle rings. [14d], Grimes reported the first neutral and air‐stable cobalt triple‐decker compounds {[(CpCo) 2 RC 2 B 3 H 4 ] (R = Me/H)} enclosing a central [RC 2 B 3 H 4 ] 4 ring . Recently, we have also reported various triple‐decker compounds [(Cp*Mo) 2 {µ‐η 6 :η 6 ‐B 4 H 4 ERu(CO) 3 }] from the reaction of [(Cp*Mo) 2 B 4 H 6 E] (E = S and Se) and [Ru 3 (CO) 12 ] .…”

“…[14d], Grimes reported the first neutral and air‐stable cobalt triple‐decker compounds {[(CpCo) 2 RC 2 B 3 H 4 ] (R = Me/H)} enclosing a central [RC 2 B 3 H 4 ] 4 ring . Recently, we have also reported various triple‐decker compounds [(Cp*Mo) 2 {µ‐η 6 :η 6 ‐B 4 H 4 ERu(CO) 3 }] from the reaction of [(Cp*Mo) 2 B 4 H 6 E] (E = S and Se) and [Ru 3 (CO) 12 ] . Synthesis of [(CpCo) 2 B 2 H 2 S 2 ] by Sneddon and our recent studies on [(Cp*Co) 2 B 2 H 2 E 2 ] ( 1 : E = S; 2 : E: Se), led us to explore the chemistry of heavier group 9 metals.…”

Synthesis, Structures, and Characterization of Dimeric Neutral Dithiolato‐Bridged Tungsten Complexes

“…The synthesis of sulfido‐bridged borate complexes of molybdenum from suitable precursors, for example, [Cp 2 Mo 2 (µ‐SMe) 2 (µ‐Cl)(µ‐Y)] (Y = SMe, PPh 2 and Cl) and [Cp 2 Mo 2 (µ‐SMe) 3 (MeCN) 2 ](BF 4 ), presented us the opportunity to explore the reactivity of various chalcogen‐based ligands, such as Ph 2 E 2 , Li[BH 3 EPh], Li[BH 2 S 3 ], CS 2 , (CH 2 ) n (SH) 2 (E = S, Se, and Te; n = 1–4), and chalcogen powders (S, Se, and Te), with readily accessible metallaboranes of groups 4–9 , . Among them, the chemistry of CS 2 with metallaboranes turned out to be very promising.…”

Triple-Decker Sandwich Complexes of Tungsten with Planar and Puckered Middle Decks

“…Although transition metal incorporated rings are highly desirable, they are rare. [17][18][19][20] Thus, the synthesis of such type complexes became of interest.…”