ca01 only detailed ToC 1..24

124 Science of Synthesis 2.6 Complexes of Cr, Mo, and W without CO Ligands
al, with concomitant metal oxidation. Azide is the ubiquitous ligand with these characteristics,
leading to the expulsion of dinitrogen. It can be administered either as a hydrophilic
alkali metal salt or as the lipophilic trimethylsilyl derivative. The reaction between
trichloro(ç 5 -pentamethylcyclopentadienyl)molybdenum(IV) dimer and trimethylsilyl
azide generates dichloro(ç 5 -pentamethylcyclopentadienyl)nitridomolybdenum(VI)
which, however, further evolves to more complex products. [140] An alternative to the
azide reagent is the deprotonated 9,10-dihydro-9,10-epiminoanthracene, [144] leading to
the elimination of anthracene.
Other nitride compounds have been obtained by oxidation of coordinated ammonia
ligands. The deoxygenation of a nitrosyl ligand is of potentially wide applicability. The
oxygen-abstracting agent is an oxophilic metal complex such as trimesityl(tetrahydrofuran)vanadium(III).
[145] Nitride compounds are also the byproducts of the addition of nitriles
to triply bonded molybdenum and tungsten compounds (see Section 2.6.2.2). The
splitting of the dinitrogen triple bond by a metal complex is a more recent achievement
[146] but is so far limited to a sterically protected triamidomolybdenum system. [147]
Other methods include the use of nitrogen trichloride, trithiazyl chloride, or aryl azide
reagents. [143,148] Splitting of nitrous oxide (N 2O) provides mixtures of nitrido and nitrosyl
products. [148]
Scheme 36 Methods for Assembling the M”N Function in Inorganic Compounds
of Group 6 Metals
X
[M] X
X
[M] R1 R1 R1 CH2R
[M]
1
CHR1 − 3X −
[M] NO
[N 3− ]
− 3R1 NH3
H
NH3
− 2R1 Me
− [O]
[M] N
− 3e −
− 3H +
[M] NH 3
[M] + 1/2 N N
− N 2
[M] N 3
[M]
− N
N3 −
N
[M] X
Phosphide and arsenide complexes have also been synthesized for the first time in nonorganometallic
complexes. [149,150] Organometallic derivatives have yet to be reported.
2.6.7 Product Subclass 7:
Complexes with Doubly Bonded Heteroelement Ligands
The vast majority of examples in this subclass are oxo and imido derivatives. A fair number
of sulfido derivatives are also known, whereas selenido and tellurido derivatives and
compounds containing a double bond to phosphorus (phosphinidene complexes) are fewer.
The relative small number of derivatives with phosphorus and the chalcogenides may
be attributed to the weakness of the ð-interaction. The bonds between the aforementioned
groups and a transition metal are considered double according to valency; however,
these bonds are often relatively short and strong in electronically unsaturated systems,
especially for oxo and imido ligands, because of the participation of an additional
ligand lone pair to the bonding.
In many cases a mononuclear structure with a terminal, doubly bonded heteroelement
ligand may be unfavorable with respect to the alternative dinuclear structure where
the ligand adopts a bridging, singly bonded conformation (Scheme 37). Facile interconversion
of the two forms may occur, leading to analogous synthetic strategies and reactivity.
−