Intramolecular Cyclization and Related Reactions of (h7-C7H7)(dppe)MoCNR Isocyanide complexes

新的氰化鉬錯合物(h7-C7H7)(PPh3)Mo(CN) (1)是從[Mo]I {[Mo] = (h7-C7H7)(dppe)Mo}和KCN在甲醇中製備的。而陽離子性的有機鉬異氰錯合物{[Mo]CNCH2R}Br, (R = CN, p-C6H4CN, p-C6H4CF3, C6F5) (2~5) 和丙酮或醛類在鹼的存在下可以得到oxazolinyl 錯合物 [Mo]C=NCHRCR’R”O(R’ = CH3, Ph, C4H9; R’’ = CH3, H) (9~20)。
這些反應的過程可能先經過azirinyl的中間物，其可以透過NMR光譜的偵測分析得知可能經由carbonyl團insertion到azirine的碳氫單鍵中而形成的。錯合物1, 2, 5和 20 的分子結構已經由X-ray繞射光譜所解析。
對於含醛類的oxazolinyl錯合物，它的鏡像異構物可以藉由立體阻礙來控制其選擇性。含有酯基的異氰錯合物{[Mo]CNCH2CO2Me}Br (6)可以環化形成oxazolone錯合物[Mo]C=NCH2C(O)O (8).
Oxazolinyl 錯合物和甲基碘或乙基碘可以得到另一種在三級碳上含不對稱中心的異氰錯合物 (21~24)。 像這樣的異氰錯合物21 也可以直接從異氫錯合物5和甲基碘在鹼中反應得到。含有不對稱中心的異氰錯合物(21, 23)在含甲醇的鹼中可以得到oxazolinyl錯合物(25, 26)。 而錯合物25可以經由異氰錯合物直接和甲醛在鹼中得到。錯合物23和 26 的分子結構已經由X-ray繞射光譜所解析。
錯合物[Ru]CCPh和過量的p-xylene dibromide在THF中可以得到[(h5-C5H5)(PPh3)2Ru+=C=C(Ph)CH2C6H4CH2Br]Br- (27). 錯合物27和[M]CN {[M] = (h5-C5H5)(PPh3)2Ru 或 (h7-C7H7)(dppe)Mo} 在迴流中的THF反應4天可以得到同時含有vinylidene和isocyanide的雙核金屬錯合物{[M]CN+CH2(C6H4)CH2(Ph)C=C=Ru+(PPh3)2(h5-C5H5)}(Br-)2 (28, 29)。 雙核金屬錯合物 28, 29 在含有丙酮和鹼中可以得到中性且含有oxazolinyl和cyclopropenyl的雙核金屬錯合物{[M]C=NCH(CH3)2O(C6H4)CH(Ph)C=C-Ru(PPh3)2(h5-C5H5)} (30, 32)。 而在短時間內可以得到同時含有oxazolinyl和vinylidene的雙核金屬錯合物(31, 33)。
錯合物[Ru]CC(C4H2S)CHO和過量的benzylbromide在THF中4天可以得到錯合物 [Ru]+=C=C(CH2Ph)(C4H2S)CHO (34). 錯合物34在含鹼的去氫化反應中可以得到cyclopropenyl錯合物 Cp(PPh3)2RuC=C(CHPh)(C4H2S)CHO. (35)。
不幸的，運用了各種不同的方法來合成含有兩個異氰(isocyanide)部份的雙陽離子雙核金屬錯合物是失敗的。

The new molybdenum cyanide complex (h7-C7H7)(PPh3)Mo(CN) (1) is prepared from [Mo]I {[Mo] = (h7-C7H7)(dppe)Mo} with KCN in MeOH. The reaction of cationic isocyanide complexes of molybdenum {[Mo]CNCH2R}Br, (R = CN, p-C6H4CN, p-C6H4CF3, C6F5) (2~5) with acetone or aldehyde in the presence of base leads to the synthesis of oxazolinyl complexes [Mo]C=NCHRCR’R”O (R’ = CH3, Ph, C4H9; R’’ = CH3, H) (9~20). This reaction proceeds possibly through an azirinyl intermediate detected by NMR spectra followed by insertion of a carbonyl group into the N-C single bond of the three-membered ring. The molecular structures of 1, 2, 5 and 20 have been determined by an X-ray diffraction study.
For aldehyde, diastereoisomers are observed and diastereoselectivity is controlled by the steric effect. With an ester group, the cationic isocyanide complex {[Mo]CNCH2CO2Me}Br (6), could cyclize to give the oxazolone complex [Mo]C=NCH2C(O)O (8).
Reactions of oxazolinyl complexes with iodomethane or iodoethane give alkylated isocyanide complexes (21~24) which have a stereogenic center in the methyne carbon. Such isocyanide complex 21 could also be obtained from the reaction of the isocyanide complex 5 with MeI in the presence of base. Reaction of the isocyanide complex (21, 23) containing a stereogenic center with base in MeOH afforded oxazolinyl complexes (25, 26). Oxazolinyl complex 25 can be obtained from the reaction of the isoyanide complex 21 with formaldehyde in the presence of base. The molecular structures of 23 and 26 have been determined by an X-ray diffraction study.
Reaction of [Ru]CCPh with an excess of p-xylene dibromide in THF gave [(h5-C5H5)(PPh3)2Ru+=C=C(Ph)CH2C6H4CH2Br]Br- (27). Treatment of Complex 27 with [M]CN {[M] = (h5-C5H5)(PPh3)2Ru and (h7-C7H7)(dppe)Mo} in refluxing THF for 4 d afforded the dinuclear metal complex {[M]CN+CH2(C6H4)CH2(Ph)C=C=Ru+(PPh3)2(h5-C5H5)}(Br-)2 (28, 29) containing metal vinylidene and metal isocyanide moieties. Deprotonation of the dinuclear metal complexes 28, 29 in the presence of base in acetone afforded the neutral dinuclear metal complexes{[M]C=NCH(CH3)2O(C6H4)CH(Ph)C=C-Ru(PPh3)2(h5-C5H5)} (30, 32) containing
oxazolinyl and cyclopropenyl moieties. Alkylation reaction of complex [Ru]CC(C4H2S)CHO with excess benzylbromide in THF for 4 days affords the vinylidene complex [Ru]+=C=C(CH2Ph)(C4H2S)CHO (34). Deprotonation of complex 34 in the presence of base affords the cyclopropenyl complex Cp(PPh3)2RuC=C(CHPh)(C4H2S)CHO. (35)
Unfortunately, diunclear metal complex containing two isocyanide moieties could not be synthesized using various methods.