A series of arenerhodium(I) complexes [(η 6 -arene)Rh(C 8 H 14 )(PiPr 3 )]PF 6 (2-6) were prepared from the highly reactive starting material cis-[Rh(C 8 H 14 )(PiPr 3 )(acetone) 2 ]PF 6 (1) and the arene in CH 2 Cl 2 in excellent yields. The related ethene compound [(η 6 -C 6 H 6 )Rh(C 2 H 4 )(PiPr 3 )]-PF 6 (7) was obtained by stirring a solution of the corresponding cyclooctene derivative 2 under an ethene atmosphere. Reaction of cis-[Rh(C 8 H 14 ) 2 (acetone) 2 ]PF 6 (10) with the new alkyldiisopropylphosphines iPr 2 P(CH 2 ) n C 6 H 5 (8, n ) 2; 9, n ) 3), which were prepared from HPiPr 2 and C 6 H 5 (CH 2 ) n Br in the presence of ammonia, in the molar ratio of 1:1 gave the half-sandwich type complexes [{η 6 -C 6 H 5 (CH 2 ) n PiPr 2 -κ-P}Rh(C 8 H 14 )]PF 6 (11, 12). They afforded upon treatment with a second equivalent of 8 or 9 the bis(phosphine) compounds [{η 6 -C 6 H 5 -(CH 2 ) n PiPr 2 -κ-P}{C 6 H 5 (CH 2 ) n PiPr 2 -κ-P}Rh]PF 6 (13, 14). The NMR spectra of 13 and 14 are not temperature-dependent, and therefore a fluxional behavior in solution can be excluded. The cyclooctene ligand of 11 could easily be displaced by ethene, maleicacid anhydride, ethyl propiolate, and triisopropylstibine to generate the substitution products 15-18 in 80-90% yield. Similarly, the ethene complex 19 was obtained from 12 and C 2 H 4 . The even more bulky alkyldi-tert-butylphosphines tBu 2 P(CH 2 ) n XC 6 H 5 (20, n ) 1, X ) CH 2 ; 21, n ) 2, X ) O) and their respective olefin and alkyne rhodium(I) complexes 22a, 23, and 24 were prepared by using the same methodology as applied for the iPr 2 P counterparts. The corresponding triflate [{η 6 -C 6 H 5 (CH 2 ) 2 PtBu 2 -κ-P}Rh(C 8 H 14 )]CF 3 SO 3 (22b) was obtained from the dimer 25 and the phosphine 20 as starting materials. The molecular structures of 11, 12, and 19 were determined by X-ray crystallography. Scheme 1 Scheme 2

The dimer [Ir(μ-Cl)(C8H14)2]2 (1) reacts with AgPF6 in acetone to give the bis(acetone) adduct cis-[Ir(acetone)2(C8H14)2]PF6 (2), which upon treatment with iPr2PCH2CH2C6H5 (L1) affords the half-sandwich-type complex [(η 6-L1-κ-P)Ir(C8H14)]PF6 (3). The methoxy-bridged dimer [Ir(μ-OMe)(C8H12)]2 (4) gives upon treatment with the phosphonium salt L1·HBF4 the compound [Ir(C8H12)(acetone)(L1-κ-P)]BF4 (5), whereas with L2·HBF4 (L2 = tBu2PCH2CH2OC6H5) the bis(chelate) complex [Ir(C8H12)(L2-κ 2-O,P)]BF4 (6) is generated. Both 5 and 6 react with hydrogen in acetone to yield the dihydridoiridium(III) derivatives [(η 6-L1-κ-P)IrH2]BF4 (7) and [(η 6-L2-κ-P)IrH2]BF4 (8), respectively. Compounds 7 and 8 react with excess ethene or propene to give the iridium(I) olefin complexes [(η 6-L1-κ-P)Ir(CH2CHR)]BF4 [R = H (9), Me (11)] and [(η 6-L2-κ-P)Ir(CH2CHR)]BF4 [R = H (10), Me (12)], which in the presence of H2 regenerate the dihydrido precursors. The reaction of 7 with 2 equiv of PhC⋮CPh affords the π-alkyne complex [(η 6-L1-κ-P)Ir(PhC⋮CPh]BF4 (14) via the stilbene derivative [(η 6-L1-κ-P)Ir(Z-PhCHCHPh)]BF4 (13) as an intermediate. Compound 13 can be isolated upon treatment of 11 with Z-stilbene and has been characterized crystallographically. The reactions of 7 and 11 with acetonitrile lead to the cleavage of the arene−metal bond and afford the octahedral iridium(III) complexes [IrH2(NCCH3)3(L1-κ-P)]BF4 (15) and [IrH(C6H4CH2CH2PiPr2-κ 2-C,P)(NCCH3)3]BF4 (16), respectively. Treatment of the C−H activation product 16 with H2 yields 15. The X-ray crystal structure analysis of 16 reveals that the Ir(NCCH3)3 fragment possesses the fac configuration.

The reaction of either [RhCl(C 8 H 14 ) 2 ] 2 or [RhCl(C 2 H 4 ) 2 ] 2 with tBu 2 PCH 2 CH 2 C 6 H 5 (3) affords at room temperature the five-coordinate arylhydridorhodium(III) complex 4, the molecular structure of which has been determined by X-ray crystallography. The C-H metalation is completely reversible, as is shown by the formation of trans-[RhCl(CO)(3) 2 ] from 4 and CO. Compound 4 also reacts with PhCtCH, H 2 , and AgPF 6 to give products 7-9 containing the intact phosphine ligand 3.

The reaction of [[RhCl(C(8)H(14))(2)](2)] (2) with iPr(2)PCH(2)CH(2)C(6)H(5) (L(1)) led, via the isolated dimer [[RhCl(C(8)H(14))(L(1))](2)] (3), to a mixture of three products 4 a-c, of which the dinuclear complex [[RhCl(L(1))(2)](2)] (4 a) was characterized by Xray crystallography. The mixture of 4a-c reacts with CO, ethene, and phenylacetylene to give the square-planar compounds trans-[RhCl(L)(L(1))(2)] (L=CO (5), C(2)H(4) (6), C=CHPh (9)). The corresponding allenylidene(chloro) complex trans-[RhCl(=C=C=CPh(2))(L(1))(2)] (11), obtained from 4 a-c and HC triple bond CC(OH)Ph(2) via trans-[RhCl[=C=CHC(OH)Ph(2)](L(1))(2)] (10), could be converted stepwise to the related hydroxo, cationic aqua, and cationic acetone derivatives 12-14, respectively. Treatment of 2 and [[RhCl(C(2)H(4))(2)](2)] (7) with two equivalents of tBu(2)PCH(2)CH(2)C(6)H(5) (L(2)) gave the dimers [[RhCl(C(8)H(14))(L(2))](2)] (15) and [[RhCl(C(2)H(4))(L(2))](2)] (16), which both react with L(2) in the molar ratio of 1:2 to afford the five-coordinate aryl(hydrido)rhodium(III) complex [RhHCl(C(6)H(4)CH(2)CH(2)PtBu(2)-kappa(2)C,P)(L(2))] (17) by C-H activation. The course of the reactions of 17 with CO, H(2), PhC triple bond CH, HCl, and AgPF(6), leading to the compounds 19-21, 24, and 25 a, respectively, indicate that the coordinatively unsaturated isomer of 17 with the supposed composition [RhCl(L(2))(2)] is the reactive species. Labeling experiments using D(2), DCl, and PhC triple bond CD support this proposal. With either [Rh(C(8)H(14))(eta(6)-L(2)-kappaP]PF(6) or [Rh(C(2)H(4))(eta(6)-L(n)-kappaP]PF(6) (n=1 and 2) as the starting materials, the corresponding halfsandwich-type complexes 27, 28, and 32 were obtained. The nonchelating counterpart of the dihydrido compound 32 with the composition [RhH(2)(PiPr(3))(eta(6)-C(6)H(6))]PF(6) (35) was prepared stepwise from [Rh(C(2)H(4))(PiPr(3))(eta(6)-C(6)H(6))]PF(6) and H(2) in acetone via the tris(solvato) species [RhH(2)(PiPr(3))(acetone)(3)]PF(6) (34) as intermediate. The synthesis of the bis(chelate) complex [Rh(eta(4)-C(8)H(12))(C(6)H(5)OCH(2)CH(2)PtBu(2)-kappa(2)O,P)]BF(4) (39) is also described. Besides 4 a, the compounds 17, 25 a, and 39 have been characterized by Xray crystal structure analysis.

The bulky functionalized phosphine 2,6-Me 2 C 6 H 3 CH 2 CH 2 PtBu 2 (3) was prepared in a stepwise fashion from the Grignard reagent 2,6-Me 2 C 6 H 3 CH 2 CH 2 MgCl, tBuPCl 2 , and tBuLi. Phosphine 3 reacts with the olefin compounds [RhCl(C 2 H 4 ) 2 ] 2 and [RhCl(C 8 H 14 ) 2 ] 2 to give the substitution products [RhCl(olefin)(3)] 2 (8, 9), of which 9 (olefin ) C 2 H 4 ) has been characterized crystallographically. While 9 is rather inert toward 3, it reacts with 3 under a hydrogen atmosphere to give the dihydrido complex [RhH 2 Cl(3) 2 ] (11) via the dimer [RhH 2 -Cl(3)] 2 (10) as an intermediate. In the presence of ethene, 11 is reconverted to 9. The reaction of 8 (olefin ) C 8 H 14 ) with the phosphonium salt 3‚HCl affords a mixture of [RhHCl 2 (3)] 2 (12) and 3, which upon warming at 60 °C produces [RhHCl 2 (3) 2 ] (13). The attempted separation of 12 by column chromatography on Al 2 O 3 led unexpectedly to the formation of the novel half-sandwich-type compound [(η 6 -2,6-Me 2 C 6 H 3 CH 2 CH 2 PtBu 2 -κP)RhCl] (14). Treatment of either 8 or 14 with CO gives cis-[RhCl(CO) 2 ( 3)] ( 15), which represents the first structurally characterized dicarbonyl complex with the CO ligands in a cis disposition. In the absence of carbon monoxide, 15 is rather labile and readily converted to [RhCl(CO)(3)] 2 (16). The reaction of 9 with HCl affords the dinuclear ethylrhodium(III) compound 18, being built up by two 14-electron [RhCl 2 (C 2 H 5 )(3)] units. These units are linked by two bridging chlorides which are unsymmetrically situated between the two metal centers. Compound 18 reacts with CO to give 15 and with 3 to give 13, presumably in both cases via [RhHCl 2 -(C 2 H 4 )(3)] as an intermediate. The half-sandwich-type complexes [(η 6 -2,6-Me 2 C 6 H 3 CH 2 -CH 2 PtBu 2 -κP)Rh(olefin)]PF 6 (20, 21), obtained from [Rh(acetone) 2 (C 8 H 14 ) 2 ]PF 6 as the precursor, react in acetone in the presence of H 2 to give [RhH 2 (acetone) 3 (3)]PF 6 (22), which upon addition of diethyl ether generates the dihydride [(η 6 -2,6-Me 2 C 6 H 3 CH 2 CH 2 PtBu 2 -κP)-RhH 2 ]PF 6 (23). Compound 23 is a suitable starting material for the preparation of compounds having the general composition [(η 6 -2,6-Me 2 C 6 H 3 CH 2 CH 2 PtBu 2 -κP)Rh(L)]PF 6 , where L is acetone, CH 2 dCHR (R ) tBu, Ph), PhCtCH, and CO, respectively.