Jonathan Selby, Andrew Schwarz and Philip Mountford from the University of Oxford, Christian Schulten, Andreas Stasch and Cameron Jones from Monash University in Melbourne, and Eric Clot from the Charles Gerhardt Institute in Montpellier have reported the synthesis of the first structurally authenticated cycloaddition products for any transition metal M=NNR₂ functional group. 

Mountford has been excited about the potential of metal-nitrogen multiple bonds to act as reactive sites for the coupling and functionalisation of small molecules since his DPhil in transition metal imido chemistry. 'I was aware from the early work of the Chatt and Hidai labs (and later Schrock's labs) that later transition metal hydrazides could have reaction chemistry, but this largely involved cleavage of the N_alpha-N_beta bond, not reactions of the M=N_alpha bond" he explains. "I have been fascinated to explore (in particular from a theoretical point of view), the fine balance between M=N_alpha coupling and N_alpha-N_beta bond scission chemistry, that appears prevalent for the early metals.' 

The collaboration have synthesised the first [2+2] cycloaddition reactions of transition metal hydrazides with internal and terminal alkynes, and also aza- and phospha-alkynes. 'These reactions demonstrate the potential breadth of substrate functionalisation chemistry available using Group 4 hydrazides' they explain.

'The binding and coupling of small molecules and molecular fragments lies at the heart of transition metal chemistry' enthuses Mountford. 'This article demonstrates new chemistry of metal hydrazide complexes; known since the pioneering work of Chatt and his colleagues to be relevant to the chemistry of N₂, one of the hardest molecules to functionalise but also the most abundant one in our atmosphere.'

According to Mountford the next stage requires a systematic study, to find the explicit relationships between structure and the various reactivity patterns seen so far, and to determine new fundamental reactions of the M=N-NR₂ group itself.