Petasis reagent

Not to be confused with Petasis reaction.

The Petasis reagent, named after Nicos A. Petasis, is an organotitanium compound with the formula Cp₂Ti(CH₃)₂.^[1] It is an orange-colored solid.

Petasis reagent

Structural formula of the Petasis reagent
Ball-and-stick model of the Petasis reagent
Names
IUPAC name Bis(η5-cyclopentadienyl)dimethyltitanium
Other names Dimethyltitanocene
Identifiers
CAS Number	1271-66-5 Y
3D model (JSmol)	Interactive image
ChemSpider	34981143 N
ECHA InfoCard	100.204.841
EC Number	679-889-8
PubChem CID	71308256
InChI InChI=1S/2C5H5.2CH3.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H3;/q2*-1;;;+2 N Key: AFEQRLILWYRIDQ-UHFFFAOYSA-N N InChI=1/2C5H5.2CH3.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H3;/q2*-1;;;+2/r2C5H5.C2H6Ti/c2*1-2-4-5-3-1;1-3-2/h2*1-5H;1-2H3/q2*-1;+2 Key: AFEQRLILWYRIDQ-MEMJIDHRAL
SMILES [Ti](C)(C).c1[cH-]ccc1.c2[cH-]ccc2
Properties
Chemical formula	C12H16Ti
Molar mass	208.13 g/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Irritant, incompatible with water and oxidizing agents
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H304, H315, H319, H332, H360, H370, H372
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation and use

The Petasis reagent is prepared by the salt metathesis reaction of methylmagnesium chloride or methyllithium^[2] with titanocene dichloride:^[3]

Cp₂TiCl₂ + 2 CH₃MgCl → Cp₂Ti(CH₃)₂ + 2 MgCl₂

This compound is used for the transformation of carbonyl groups to terminal alkenes. It exhibits similar reactivity to the Tebbe reagent and Wittig reaction. Unlike the Wittig reaction, the Petasis reagent can react with a wide range of aldehydes, ketones and esters.^[4] The Petasis reagent is also very air stable, and is commonly used in solution with toluene or THF.

The Tebbe reagent and the Petasis reagent share a similar reaction mechanism. The active olefinating reagent, Cp₂TiCH₂, is generated in situ upon heating. With the organic carbonyl, this titanium carbene forms a four membered oxatitanacyclobutane that releases the terminal alkene.^[5]

In contrast to the Tebbe reagent, homologs of the Petasis reagent are relatively easy to prepare by using the corresponding alkyllithium instead of methyllithium, allowing the conversion of carbonyl groups to alkylidenes.^[6]

See also

• Nysted reagent
• Titanium–zinc methylenation