# Amidinatotetrylenes Donor Functionalized on Both N Atoms: Structures and Coordination Chemistry

## TL;DR

Scientists created new chemical compounds with unique structures that can form metal complexes with unusual bonding patterns.

## Contribution

The first amidinatotetrylenes with quinolyl groups on both nitrogen atoms, forming novel κ3E,N,N′-ligand metal complexes.

## Key findings

- Germylene and stannylene compounds with quinolyl arms form fluxional structures in solution.
- Reactions with gold, palladium, and platinum produce complexes with a pincer-like κ3E,N,N′-ligand configuration.
- Tin derivatives show quinolyl fragments interacting with the tetrel atom, unlike germanium compounds.

## Abstract

E(hmds)(bqfam) (E
= Ge (1a), Sn (1b);
hmds = N(SiMe3)2, bqfam = N,N′-bis(quinol-8-yl)formamidinate), which are amidinatotetrylenes equipped
with quinol-8-yl fragments on the amidinate N atoms, have been synthesized
from the formamidine Hbqfam and Ge(hmds)2 or SnCl(hmds).
Both 1a and 1b are fluxional in solution
at room temperature, as the E atom oscillates from being attached
to the two amidinate N atoms to being chelated by an amidinate N atom
and its closest quinolyl N atom (both situations are similarly stable
according to density functional theory calculations). The hmds group
of 1a and 1b is still reactive and the deprotonation
of another equivalent of Hbqfam can be achieved, allowing the formation
of the homoleptic derivatives E(bqfam)2 (E = Ge, Sn). The
reactions of 1a and 1b with [AuCl(tht)]
(tht = tetrahydrothiophene), [PdCl2(MeCN)2],
[PtCl2(cod)] (cod = cycloocta-1,5-diene), [Ru3(CO)12] and [Co2(CO)8] have been
investigated. The gold(I) complexes [AuCl{κE-E(hmds)(bqfam)}] (E = Ge, Sn) have a monodentate κE-tetrylene ligand and display fluxional behavior in solution
the same as that of 1a and 1b. However,
the palladium(II) and platinum(II) complexes [MCl{κ3E,N,N′-ECl(hmds)(bqfam)}]
(M = Pd, Pt; E = Ge, Sn) contain a κ3E,N,N′-chloridotetryl ligand that arises from the insertion of the tetrylene
E atom into an M–Cl bond and the coordination of an amidinate
N atom and its closest quinolyl N atom to the metal center. Finally,
the binuclear ruthenium(0) and cobalt(0) complexes [Ru2{μE-κ3E,N,N′-E(hmds)(bqfam)}(CO)6] and [Co2{μE-κ3E,N,N′-E(hmds)(bqfam)}(μ-CO)(CO)4] (E = Ge, Sn)
have a related κ3E,N,N′-tetrylene ligand that bridges two metal atoms through the
E atom. For the κ3E,N,N′-metal complexes, the quinolyl fragment not attached to the metal
is pendant in all the germanium compounds but, for the tin derivatives,
is attached to (in the Pd and Pt complexes) or may interact with (in
the Ru2 and Co2 complexes) the tin atom.

Amidinatotetrylenes donor functionalized
on both nitrogen
atoms have been prepared for the first time from N,N′-bis(quinol-8-yl)formamidine and Ge{N(SiMe3)2}2 or SnCl{N(SiMe3)2}. The resulting germylene
and stannylene, decorated with two quinol-8-yl arms on both sides
of the amidinato fragment, have led to metal complexes equipped with
an unexpected pincer κ3E,N,N′-ligand configuration (E = Ge, Sn). Curiously, one of the two quinolyl
fragments is pendant for the germanium compounds, but interacting
with the tetrel atom for the tin derivatives.