The non-heteroatom-sub
stituted alkynyl carbene Cp′(CO)
2Mn
C(Tol)C
CPh (
1, Cp′ ≡ (η
5-MeC
5H
4)) is fir
st shown to react at low temperature with lithium diorganophosphide LiPR
2 (R = Ph, Cy) to form an anionic species. Subsequent treatment with CF
3SO
3H affords the η
4-vinylketene complex Cp′(CO)
2Mn[η
4-{R
2P(Ph)C
CHC(Tol)
C
O}] (
2;
2a: R = Ph (70% yield),
2b: R = Cy (55% yield)) as the major compound, along with trace amounts of the η
2-allene complex
syn-Cp′(CO)
2Mn[η
2-{Ph
2P(Tol)C
C
C(Ph)H}] (
syn-
3a) for R = Ph, or along with the η
2-allene complex Cp′(CO)
2Mn[η
2-{H(Tol)C
C
C(Ph)PCy
2}] (
4b, 26% yield, 1:2 mixture of
syn/
anti isomers) for R = Cy. On the other hand, subsequent treatment with NH
4Cl
aq affords only η
2-allene comple
xes, obtained either as a ca. 1:9 mixture of
syn-
3a and Cp′(CO)
2Mn[η
2-{H(Tol)C
C
C(Ph)PPh
2}] (
4a) (75% yield) for R = Ph or as a 1:2 mixture of
syn- and
anti-
4b for R = Cy (74% yield). Combined NMR and single-cry
stal X-ray diffraction
studies (for
2a,
anti-
4b, and
syn-
4b) revealed that both type
2 and type
4 species result from a nucleophilic attack of the diorganophosphide onto the remote alkynyl carbon atom in
1 (C
γ), whereas type
3 species results from a nucleophilic attack of the carbene carbon atom (C
α). Comple
xes
3a and
4a,
b are prone to undergo a thermal rearrangement to give the η
1-phosphinoallene comple
xes Cp′(CO)
2Mn[η
1-{Ph
2P(Tol)C
C
C(Ph)H}] (
5a) and Cp′(CO)
2Mn[η
1-{R
2P(Ph)C
C
C(Tol)H}] (
6;
6a: R = Ph,
6b: R = Cy), respectively. Reaction of
1 with
p-toluenethiol in the presence of NEt
3 (20%) affords a 1.8:1 mixture of Cp′(CO)
2Mn[η
2-{TolS(Tol)C
C
C(Ph)H}] (
syn-
11), resulting from a nucleophilic attack at C
α in
1, and Cp′(CO)
2Mn[η
2-{H(Tol)C
C
C(Ph)STol}] (
12), resulting from a nucleophilic attack at C
γ, whereas treatment of
1 with lithium
p-toluenethiolate at –80 °C followed by protonation with NH
4Cl
aq gave the same
syn-
11 and
12 comple
xes now in a 1:2.3 ratio. Finally,
1 was found to react with cyclohexanone lithium enolate to afford, upon protonation, the η
2-allene complex Cp′(CO)
2Mn[η
2-{H(Tol)C
C
C(Ph)CH(CH
2)
4C(O)}] (
syn-
13), resulting from a nucleophilic attack at C
γ in
1. The solid-
state
structures of
syn-
11 and
syn-
13 are also reported.