Heterometallic Complexes with Rhenium- and Iron-Bismuth Bonds

Abstract

Dedicated to Professor Heinrich Nöth on the occasion of his 85 th birthdayReaction

Creating Iron– and Rhenium–Bismuth Bonds by Reactions with Organometallic Hydrides

“…The IR spectrum of 1· 2C 6 H 6 in a KBr pellet showed C–C and C–H vibration bands caused by the η 5 ‐C 5 H 5 ligands from 1390 to 1007 cm –1 as well as from 830 to 807 cm –1 , assigned by comparison with the IR spectrum of the alkoxide [(Cp 2 Re) 2 Bi{OCH(CF 3 ) 2 }] . Additionally the absorption bands found at 3097 to 3029 cm –1 can be assigned to C–H‐stretching vibrations of the eight η 5 ‐C 5 H 5 ligands and of the two C 6 H 6 molecules.…”

“…The two Bi–O bond lengths in 1 are longer [2.1285(6), 2.1544(5) Å] than those in [{(mes) 2 Bi} 2 O (2.064(7), 2.075(8) Å] or in {( o ‐tolyl) 2 Bi} 2 O [2.080(4), 2.091(4) Å]. The structural parameters of the nearly identical [(Cp 2 Re) 2 Bi] moieties [Re–Bi 2.8881(1)–2.9167(1) Å, Re–Bi–Re 113.023(1), 113.266(1)°, O–Bi–Re 97.877(12)–105.185(12)°] are in good compliance with those in the mono alkoxide [(Cp 2 Re) 2 Bi{OCH(CF 3 ) 2 }] [Re–Bi = 2.8502(4), 2.8590(4) Å, Re1–Bi–Re2 116.63(1)°, O–Bi–Re 101.53(13), 102.14(13)°] . Interestingly, the calculated positions of the protons (H6, H16, H26, H37) at the η 5 ‐C 5 H 5 rings (Cp2, Cp4, Cp6, Cp8) are found in close proximity to the oxygen atom of the [Bi–O–Bi] bridge [distances C Cp –H ··· O = 2.8797(7)–3.1736(6) Å with angles C–H ··· O 116.889(30)–135.983(31)°] (see Figure ).…”

“…Having finally fully understood the system [Cp 2 ReH] / [Bi(O t Bu) 3 ] it is clear, that the “hydride–alkoxide approach” can be utilized to create a large variety of organometallic compounds not only with Mo–Bi bonds but also such featuring Re–Bi bonds via reactions of rhenocene hydride with bismuth alkoxides . Bearing in mind the unique interplay between iron and bismuth in multiferroic bismuth ferrite (BiFeO 3 , BFO) an extension of this protocol also to the synthesis of complexes with Fe–Bi entities via reactions of bismuth alkoxides with iron hydrides was the obvious to test next, as potentially resulting molecular compounds may serve as single source precursors for BFO , .…”

“…Two routes to compounds like [{( η 5 ‐C 5 H 4 R )(CO) 2 Fe}BiMe 2 ] ( R = H), [{( η 5 ‐C 5 H 4 R)(CO) 2 Fe} 2 Bi X ] ( R = H, X = Cl, Br; R = Me, X = Cl) and [{( η 5 ‐C 5 H 4 R )(CO) 2 Fe} 3 Bi] ( R = H, Me) have been established so far: (i) salt metathesis reactions treating bismuth halides with alkali metal salts of [Fp] – [27–30] or (ii) cleavage of the Fe–Fe bond in the [Fp 2 ] dimer in reactions with bismuth halides or bismuth dithiocarbamates as first reported by Cullen and co‐workers in 1971 for the synthesis of [FpBiCl 2 ] and later for the synthesis of [FpBi X 2 ] [ X = SC(S)NEt 2 , SC(S)OMe] by Wieber and co‐workers . The latter approach was recently successfully adapted by Mehring and co‐workers to access [Fp R BiBr 2 ] {Fp R = Fp; Fp t Bu [( η 5 ‐C 5 H 3 ‐1,3‐ t Bu 2 )(CO) 2 Fe]; Fp* [( η 5 ‐C 5 Me 5 )(CO) 2 Fe]} starting from [Fp R 2 ] and BiBr 3 (Scheme ) and also by us to synthesize the carboxylates [FpBi(O 2 C R ) 2 ] 2 via reaction of [Fp 2 ] with [Bi(O 2 CR) 3 ] [ R = H ( VII ), CH 3 ( VIII ), t Bu ( IX )] (Scheme ) . Treatment of VIII with [Cp 2 ReH] even allowed to construct a heterotrimetallic compound, which illustrates the value of the availability of a variety of tools to create M–M ′ bonds.…”

“…So far Fe–Bi compounds were not synthesized via this “hydride‐alkoxide” route but recently we were able to show that [Fp‐Bi(O 2 CR) 2 ] 2 representatives can be generated via treatment of [Fp 2 ] [Fp = ( η 5 ‐C 5 H 5 )(CO) 2 Fe] with [Bi(O 2 C R ) 3 ] , . [Fp‐Bi(O 2 CCH 3 ) 2 ] 2 turned out to be a suitable single source precursor (SSP) to generate BFO .…”