Trifluorosulfane Ligand as an Analogue of the Nitrosyl Ligand: Highly Exothermic Fluorine Transfer Reactions from Sulfur to Metal in the Chemistry of SF₃Metal Carbonyls of the First Row Transition Metals

Abstract

The variety of known very stable PF(3) metal derivatives analogous to metal carbonyls suggests the synthesis of SF(3) metal derivatives analogous to metal nitrosyls. However, the only known SF(3) metal complex is the structurally uncharacterized (Et(3)P)(2)Ir(CO)(Cl)(F)(SF(3)) synthesized by Cockman, Ebsworth, and Holloway in 1987 and suggested by electron counting to have a one-electron donor SF(3) group rather than a three-electron donor SF(3) group. In this connection, the possibility of synthesizing SF(3) metal derivatives analogous to metal nitrosyls has been investigated using density functional theory. The [M]SF(3) derivatives with [M] = V(CO)(5), Mn(CO)(4), Co(CO)(3), Ir(CO)(3), (C(5)H(5))Cr(CO)(2), (C(5)H(5))Fe(CO), and (C(5)H(5))Ni analogous to known metal nitrosyl derivatives are all predicted to be thermodynamically disfavored with respect to the corresponding [M](SF(2))(F) derivatives by energies ranging from 19.5 kcal/mol for Mn(SF(3))(CO)(4) to 5.4 kcal/mol for Co(SF(3))(CO)(3). By contrast, the isoelectronic [M]PF(3) derivatives with [M] = Cr(CO)(5), Fe(CO)(4), Ni(CO)(3), (C(5)H(5))Mn(CO)(2), (C(5)H(5))Co(CO), and (C(5)H(5))Cu are all very strongly thermodynamically favored with respect to the corresponding [M](PF(2))(F) derivatives by energies ranging from 64.3 kcal/mol for Cr(PF(3))(CO)(5) to 31.6 kcal/mol for (C(5)H(5))Co(PF(3))(CO). The known six-coordinate (Et(3)P)(2)Ir(CO)(Cl)(F)(SF(3)) is also predicted to be stable relative to the seven-coordinate (Et(3)P)(2)Ir(CO)(Cl)(F)(2)(SF(2)). Most of the metal SF(3) complexes found in this work are singlet structures containing three-electron donor SF(3) ligands with tetrahedral sulfur coordination. However, two examples of triplet spin state metal SF(3) complexes, namely, the lowest energy (C(5)H(5))Fe(SF(3))(CO) structure and a higher energy Co(SF(3))(CO)(3) structure, are found containing one-electron donor SF(3) ligands with pseudo square pyramidal sulfur coordination with a stereochemically active lone electron pair.

Fluorination Reactions at a Platinum Carbene Complex: Reaction Routes to SF3, S(=O)F and Fluorido Complexes

“…The frontier orbital analysis revealed that the electron pair is reflected by the HOMO (Figure 2). Hence, the λ 4 ‐trifluoro sulfanyl ligand can be considered as an one‐electron donor or two‐electron donor, when the sulfanyl group is considered to be anionic [21] …”

Reactivity of Binary and Ternary Sulfur Halides towards Transition‐Metal Compounds

“…The experimentally observed pseudo‐square‐pyramidal (trigonal‐bipyramidal) geometry at sulfur is consistent with a one‐electron‐donor ligand. In contrast, a tetrahedral arrangement at the sulfur atom is in accordance with a formal 3‐electron donation to the metal center . Calculations on the experimentally known complexes trans ‐[Ir(Cl)(F)(SF 3 )(CO)(PEt 3 ) 2 ] ( 119 ) cis , trans ‐[Rh(F) 2 (SF 3 )(CO)(PEt 3 ) 2 ] ( 122 ), and trans ‐[Pt(F)(SF 3 )(PR 3 ) 2 ] [R= i Pr ( 125 a ), Cy ( 125 b )] revealed a pseudo‐square‐pyramidal (trigonal‐bipyramidal) coordination of the sulfur atom, which was also suggested based on variable temperature NMR spectroscopic data …”

“…DFT studies on fluoride migration reactions in trans ‐[Ir(Cl)(F)(SF 3 )(CO)(PEt 3 ) 2 ] ( 119 ), [M(SF 3 )(CO) n ] (M=V ( 131 a ), Ta ( 131 b ), n =5; M=Mn ( 131 c ), Re ( 131 d ), n =4; M=Co ( 131 e ), Ir ( 131 f ), n =3) and [CpM(SF 3 )(CO) n ] (Cp=η 5 ‐C 5 H 5 ; M=Cr ( 132 a ), W ( 132 b ), n =2; M=Fe ( 132 c ), Os ( 132 d ), n =1; M=Ni ( 132 e ), Pt ( 132 f ), n =0) to form the respective {[M](F)(SF 2 )} complexes suggest an instability of SF 3 ligands at first‐ and third‐row transition‐metal derivatives . Exceptional cases are both iridium‐based compounds, for which a fluoride shift in [Ir(SF 3 )(CO) 3 ] ( 131 f ) is almost thermoneutral and is clearly energetically not favored in trans ‐[Ir(Cl)(F)(SF 3 )(CO)(PEt 3 ) 2 ] ( 119 ) .…”

“…DFT studies on fluoride migration reactions in trans ‐[Ir(Cl)(F)(SF 3 )(CO)(PEt 3 ) 2 ] ( 119 ), [M(SF 3 )(CO) n ] (M=V ( 131 a ), Ta ( 131 b ), n =5; M=Mn ( 131 c ), Re ( 131 d ), n =4; M=Co ( 131 e ), Ir ( 131 f ), n =3) and [CpM(SF 3 )(CO) n ] (Cp=η 5 ‐C 5 H 5 ; M=Cr ( 132 a ), W ( 132 b ), n =2; M=Fe ( 132 c ), Os ( 132 d ), n =1; M=Ni ( 132 e ), Pt ( 132 f ), n =0) to form the respective {[M](F)(SF 2 )} complexes suggest an instability of SF 3 ligands at first‐ and third‐row transition‐metal derivatives . Exceptional cases are both iridium‐based compounds, for which a fluoride shift in [Ir(SF 3 )(CO) 3 ] ( 131 f ) is almost thermoneutral and is clearly energetically not favored in trans ‐[Ir(Cl)(F)(SF 3 )(CO)(PEt 3 ) 2 ] ( 119 ) . Substitution of one of the sulfur bound fluorine atoms by NMe 2 again resulted in an energetically favored fluoride shift for {M[SF 2 (NMe 2 )](CO) n } [M=Ta, n =5 ( 133 a ); M=Re, n =4 ( 133 b ); M=Ir, n =3 ( 133 c )] and {CpM[SF 2 (NMe 2 )](CO) n } [Cp=η 5 ‐C 5 H 5 ; M=Cr ( 134 a ), Mo ( 134 b ), W ( 134 c ), n =2; M=Os, n =1 ( 134 d ); M=Pt, n =0 ( 134 e )] to yield the respective {[M](F)[SF(NMe 2 )]} complexes .…”

Sulfur difluoride and sulfur monofluoride as ligands in iron carbonyl chemistry

“…Theoretical studies suggest that metal carbonyl trifluorosulfane derivatives such as M(CO) n (SF 3 ) (n = 5, M = V, Ta; n = 4, M = Mn, Re; n = 3, M = Co) with tetrahedral three-electron donor SF 3 ligands are strongly disfavored thermochemically with respect to a fluorine shift from sulfur to metal to give isomeric M(CO) n (F)(SF 2 ) complexes. 22,23 Only Ir(CO) 3 (SF 3 ), in which the SF 3 group is a pseudo trigonal bipyramidal oneelectron donor ligand rather than a tetrahedral three-electron donor ligand, has a chance of being viable toward fluorine shift to give the isomeric Ir(CO) 3 (F)(SF 2 ) derivative. These theoretical studies suggest that the SF 3 ligand, at least as a tetrahedral threeelectron donor, is too strong a fluorinating agent for trifluorosulfane metal carbonyl complexes to be viable.…”