Neutral R₃PAuGe₉(Hyp)₃ (R=Et, ⁿPr, ⁱPr, ⁿBu, ^tBu, Cy) (Hyp=Si(SiMe₃) Clusters give new insights into the ligand strength of the metalloid [Ge₉(Hyp)₃]⁻ cluster

Abstract

Dedicated to Professor Hansgeorg Schnöckel on the occasion of his 80th birthdayWe present new insights into the ligand strength of the metalloid [Ge 9 (Hyp) 3 ] À cluster (Hyp = Si(SiMe 3 ) 3 ) alongside novel neutral Ge 9 clusters of the composition R 3 PAuGe 9 (Hyp) 3 (R=Et, n Pr, i Pr, n Bu, t Bu, Cy). These clusters are synthesized in good yields from KGe 9 (Hyp) 3 and R 3 PAuCl. Further experiments with these new clusters show that the ligand strength of [Ge 9 (Hyp) 3 ] À is in between aryl and alkyl phosphines.

Three different ways for the synthesis of the metalloid cluster [Ge9(HyptBuPh2)3]−

“…The nine germanium atoms in 2 are arranged as a distorted tricapped trigonal prism, where one Et 3 PAu group is bonded η 3 through the gold atom to one triangle of naked germanium atoms. A similar arrangement is found in the comparable intermetalloid clusters [(Hyp) 3 Ge 9 Au(PEt 3 )] ( B ) and [(Hyp) 3 Ge 9 Au(P n Pr 3 )] ( C ) [16] . Due to the bonding of the (Au(PEt 3 )‐group to a Ge 3 triangle in 2 the Ge−Ge bonds in this triangle are elongated compared to the opposite triangle in the trigonal prism, leading to a strongly distorted tricapped trigonal prismatic arrangement in 2 .…”

“…[16] In case of C, the highly bent PÀ AuÀ ctp unit leads to differences in the trigonal prism heights up to 47 pm, comparable to 2 where the differences amount to 43 pm (Table 1). This is in contrast to B, where the prism heights only differ by 7 pm, [16] showing that the unsymmetric bonding of the Finally, by the synthesis of 2 we could show, that the reactivity of 1 is similar to A, even though the substituents in 1 are sterically more demanding.…”

“…In this case, only a salt metathesis reaction occurs leading to neutral clusters [R 3 PAuGe 9 (Hyp) 3 ], showing that the ligand strength of A lies in between aryl and alkyl phosphines. [16] Linking of two Ge 9 (Hyp) 3 units by a copper atom and capping of a trigonal prismatic base of one of the units by a Cu(PPh 3 ) fragment occurs in the reaction system A/Cu(PPh 3 ) 3 Br leading to [(Hyp) 3 Ge 9 -CuÀ Ge 9 (Hyp) 3 -Cu(PPh 3 )]. [13] Linking of two Ge 9 (Hyp) 3 fragments through an iron atom by the reaction of A with FeCl 2 in the presence of dppe does not occur, instead an oxidation of A takes place.…”

“…Selected distances and angles of 2, [(Hyp) 3 Ge 9 Au(PEt 3 )] and [(Hyp) 3 Ge 9 Au(PnPr 3 )]; (ctp = center of gravity of the triangle of naked germanium atoms). [16] Distances [pm]…”

Substitution of Hyp (Hyp = Si(SiMe3)3) at metalloid [Ge9(Hyp)3]− clusters using phosphine stabilized Au(i)Cl

“…18 The recent syntheses of alkyl phosphine gold germanium clusters like (Bu 3 P)Au-Ge 9 (Hyp) 3 offered a deeper insight into the ligand strength of the germanium cluster [Ge 9 (Hyp) 3 ] − , showing that its ligand strength in transition metal chemistry is between aryl and alkyl phosphines. 19 Further reactions of functionalized intermetalloid clusters MGe 9 (Hyp) 3 give access to intermetalloid clusters where Ge 9 R x units are bound to different transition metal atoms. 20 In these presented build-up reactions, [Ge 9 (Hyp) 3 ] − or [Ge 9 (Hyp) 2 ] 2− are used as building blocks retaining the same number of Hyp-substituents.…”