The reaction of Mo(
![]()
N)(CH
2tBu)
3 (
1) and SiO
2-(700) generates (
![]()
SiO)Mo(
![]()
NH)(
![]()
CH
tBu)(CH
2tBu) (
2) when performed in C
6H
6 (material
[1/SiO2-(700)]C6H6). The grafting occurs presumably by protonation of the nitrido ligand to form an intermediate (
![]()
SiO)Mo(
![]()
NH)(CH
2tBu)
3 (
3), a pentacoordinated complex, which decomposes into
2 and 2,2-dimethylpropane. While
[1/SiO2-(700)]C6H6 is highly active in olefin metathesis,
[1/SiO2-(700)]CH2Cl2 and [
1/SiO
2-(700)]
THF are poorly active or inactive catalysts respectively. In contrast, when Mo(
![]()
N)(CH
2tBu)
3 reacts with a molecular silanol derivative, a soluble model of the surface of SiO
2-(700), it yields a very stable complex, (
c-C
5H
9)
7Si
7O
12SiO–Mo(
![]()
NH)(CH
2tBu)
3 (
3m), which does not spontaneously generate 2,2-dimethylpropane and an alkylidene complex in contrast to the surface complex. Moreover,
3m does not catalyse olefin metathesis at room temperature as it does not already contain the initiating carbene ligand, and it is necessary to heat up the reaction mixture to 110 °C to obtain low catalytic activity. Nevertheless, the complex
3m generates well-defined metallocarbenes when heated in the presence of PMe
3: (
c-C
5H
9)
7Si
7O
12SiO–Mo(
![]()
N)(
![]()
CH
tBu)(P(CH
3)
3)
2 (
4m) as a 10:1 mixture of its
syn and
anti rotamers with the loss of 2 equiv. of 2,2-dimethylpropane.