Monophosphine and diphosphine ligands for diplatinum polyynediyl complexes: Efficient syntheses of new functionality-containing systems and model compounds

Br(CH2)4Br and NaO(CH2)2CH&dbnd;CH2 react under suitable conditions to give Br(CH2)4O(CH2)2CH&dbnd;CH2 (55%), which is treated with KPPh2 to yield the ether-containing phosphine Ph2P(CH2)4O(CH2)2CH&dbnd;CH2 (83%). The reaction of CH3CH2OC(O)CH&dbnd;C(CH3)2 and BrMg(CH2)3CH&dbnd;CH2 in the presence of CuCl (cat.) and ClSiMe3 yields CH3CH2OC(O)CH2C(CH3)2(CH2)3CH&dbnd;CH2 (67%), which is reduced to an alcohol that is brominated, reacted with Grubbs’ catalyst, hydrogenated, and treated with KPPh2 to give the bis(geminally dimethylated) diphosphine Ph2P(CH2)2C(CH3)2(CH2)8C(CH3)2(CH2)2PPh2 (47% overall).

The photochemical reaction of I(CF2)8I and H2C&dbnd;CHCH2SnBu3 yields H2C&dbnd;CHCH2(CF2)8CH2CH&dbnd;CH2 (52%), which is converted with 9-BBN to a diol (92%) that is brominated and treated with LiPR2 to give the fluorinated diphosphines R2P(CH2)3(CF2)8(CH2)3PR2 (R=a, p-tol, 67%; b, t-Bu, 69%; c, o-tol, 86%).

Reactions of Br(CH2)mBr and LiPR2 similarly yield R2P(CH2)mPR2 (m/R=8/a, 95%; 14/a, 96%; 14/p-C6H4-t-Bu, 98%). Reactions of KPPh2 with Br(CH2)m′CH&dbnd;CH2and Br(CH2)7CH3 give the corresponding monophosphines Ph2P(CH2)m′CH&dbnd;CH2 (m′=7, 82%; 10, 84%) and Ph2P(CH2)7CH3 (85%). When the former is combined with [Pt(μ-Cl)(C6F5)(tht)]2 (tht=tetrahydrothiophene), trans-(C6F5)(Ph2P(CH2)m′CH&dbnd;CH2)2PtCl (77–70%) is isolated.

When the latter (excess) is combined with trans,trans-(C6F5)(p-tol3P)2Pt(C&tbnd;C)4Pt(Pp-tol3)2(C6F5) (RT, 65°C), trans,trans-(C6F5)(Ph2P(CH2)7CH3)2Pt(C&tbnd; C)4Pt(Ph2P(CH2)7CH3)2(C6F5) (53%) is isolated.