# Activation of CO, Isocyanides, and Alkynes by Frustrated Lewis Pairs Based on Cp*M/N (M = Rh, Ir) Couples

## TL;DR

This paper explores how certain metal complexes react with molecules containing triple bonds, forming new chemical structures.

## Contribution

The study introduces new frustrated Lewis pair reactivity patterns of Cp*M/N complexes with triple-bond substrates.

## Key findings

- Rhodium and iridium complexes react differently with CO, forming distinct carbamoyl derivatives.
- Isocyanides and alkynes are activated through insertion and coordination mechanisms.
- X-ray diffraction confirms the structures of newly formed complexes.

## Abstract

The complexes [Cp*M­(κ3
N,N′,N″-L)]­[SbF6] (Cp* = η5-C5Me5;
M = Rh, 1, Ir, 2; HL = pyridinyl-amidine)
display M/N transition metal frustrated Lewis pair reactivity toward
a range of substrates containing triple bonds. Whereas the rhodium
complex 1 reacts with CO yielding compound [Cp*Rh­(CO)­(κ2
C,N-LCO)]­[SbF6] (3), which contains a terminal carbonyl and
a carbamoyl group, the iridium complex 2 generates compound
[Cp*Ir­(κ3
C,N,N′-LCO)]­[SbF6] (4), which only features the carbamoyl group. Compounds 1 and 2 react with stoichiometric amounts of the isocyanides
CNR (R = Cyclohexyl, p-C6H4(OMe), CH2SO2(p-Tolyl)) to
give the corresponding 1,1-insertion complexes [Cp*M­(κ3
C,N,N′-LCNR)]­[SbF6] (5–10). Complexes
containing inserted and coordinated isocyanide ligands of formula
[Cp*M­(CNR)­(κ2
C,N-LCNR)]­[SbF6] (11–15)
are obtained upon treating 1 and 2 with
excess of the corresponding isocyanide. Compound 2 reacts
with CN
t
Bu affording the adduct [Cp*Ir­(CN
t
Bu)­(κ2
N,N′-L)]­[SbF6] (16) which contains a terminal CN
t
Bu ligand. Complex 16 is protonated by HSbF6 to give [Cp*Ir­(CN
t
Bu)­(κ2
N,N′-HL)]­[SbF6]2 (17). The terminal alkynes HCCR
(R = Ph, CO2Et) react with 1 and 2 rendering the alkynyl complexes 18–21. Dimethyl
acetylenedicarboxylate reacts with complex 2 to give
compound 22 via the formal 1,2-addition of a basic nitrogen
atom and the metal across the alkyne triple bond. The new complexes
have been characterized by analytical, spectroscopic and X-ray diffraction
(XRD) methods.