TY - JOUR
T1 - Surface Organometallic Chemistry of Inorganic Oxides
T2 - The Synthesis and Characterization of (≡SiO)Ta(=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
2
and (≡SiO)
2
Ta(=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
AU - Dufaud, Véronique
AU - Niccolai, Gerald P.
AU - Thivolle-Cazat, Jean
AU - Basset, Jean-Marie Maurice
PY - 1995/1/1
Y1 - 1995/1/1
N2 -
The synthesis of two silica-supported tantalum(V) carbene complexes is reported. The reaction of Ta- (=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
3
(1) with a silica dehydroxylated at 500 °C produces a mixture of (≡SiO)Ta(=CHC-(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
2
(2a) and (≡SiO)
2
Ta(=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
) (2b) and neopentane gas (on average 1.3 equiv/equiv of tantalum). The reaction of 2a/2b with water produces 2.6 mol of neopentane. The reaction of 2a/2b with acetone produces 1 equiv of 2,4,4-trimethyl-2-pentene per grafted tantalum, indicating that 2a,b each bear one carbene ligand. When 1 is reacted with fully (>90%) deuterated silica, the product neopentane is only 38% monodeuterated. The product of this reaction (2
deut
) is hydrolyzed with D
2
O to produce 2.6 equiv (per Ta) of neopentane as a mixture of neopentane-d
0
, -d
1
, -d
2
, and -d
3
(3.3:54.4:36.7:5.5). The presence of neopentane-d
3
is evidence for the incorporation of deuterium into the tantalum surface complex during the synthesis of 2a/2b. The volatile product of the reaction of 2
deut
with acetone is 1 equiv of 2,4,4-trimethyl-2-pentene which is 15% monodeuterated, demonstrating some incorporation of deuterium in the carbenic positions of 2
deut
. The isotopomeric distribution in the volatile products of these reactions is traced to a mechanism of formation of 2a,b in which the first reaction of surface silanol with 1 is the addition of O—H across the Ta=C double bond.
AB -
The synthesis of two silica-supported tantalum(V) carbene complexes is reported. The reaction of Ta- (=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
3
(1) with a silica dehydroxylated at 500 °C produces a mixture of (≡SiO)Ta(=CHC-(CH
3
)
3
)(CH
2
C(CH
3
)
3
)
2
(2a) and (≡SiO)
2
Ta(=CHC(CH
3
)
3
)(CH
2
C(CH
3
)
3
) (2b) and neopentane gas (on average 1.3 equiv/equiv of tantalum). The reaction of 2a/2b with water produces 2.6 mol of neopentane. The reaction of 2a/2b with acetone produces 1 equiv of 2,4,4-trimethyl-2-pentene per grafted tantalum, indicating that 2a,b each bear one carbene ligand. When 1 is reacted with fully (>90%) deuterated silica, the product neopentane is only 38% monodeuterated. The product of this reaction (2
deut
) is hydrolyzed with D
2
O to produce 2.6 equiv (per Ta) of neopentane as a mixture of neopentane-d
0
, -d
1
, -d
2
, and -d
3
(3.3:54.4:36.7:5.5). The presence of neopentane-d
3
is evidence for the incorporation of deuterium into the tantalum surface complex during the synthesis of 2a/2b. The volatile product of the reaction of 2
deut
with acetone is 1 equiv of 2,4,4-trimethyl-2-pentene which is 15% monodeuterated, demonstrating some incorporation of deuterium in the carbenic positions of 2
deut
. The isotopomeric distribution in the volatile products of these reactions is traced to a mechanism of formation of 2a,b in which the first reaction of surface silanol with 1 is the addition of O—H across the Ta=C double bond.
UR - http://www.scopus.com/inward/record.url?scp=0001649048&partnerID=8YFLogxK
U2 - 10.1021/ja00120a010
DO - 10.1021/ja00120a010
M3 - Article
AN - SCOPUS:0001649048
SN - 0002-7863
VL - 117
SP - 4288
EP - 4294
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 15
ER -