Synthesis of Heterodinuclear (Carbene)platinum (or palladium

The Pt−C bond distances (1.970(14) Å (1·C6H6), 1.956(16) Å (2·2C6H6)) are ...... 10, NEt3, 0.1, 86, 12, 83, 100:0 ..... Yield: 58% (139.2 mg, 0...
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5368

Organometallics 2009, 28, 5368–5381 DOI: 10.1021/om900421k

Synthesis of Heterodinuclear (Carbene)platinum (or palladium) Complex That Gives μ-Alkenyl-Type Complex by Deprotonation Shin-ichi Tanaka, Nobuyuki Komine, Masafumi Hirano, and Sanshiro Komiya* Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan Received May 20, 2009

Heterodinuclear platinum (or palladium) complexes having a terminal carbene, (Ph3P)Cl(Me2NHC)M-M0 L0 n (M = Pt: M0 L0 n = Co(CO)4 (1), Mn(CO)5 (2), MoCp(CO)3 (3), FeCp(CO)2 (4); M=Pd: M0 L0 n=Co(CO)4 (33), Mn(CO)5 (34)) and (L)Cl{(PhCH2)YC}Pt-M0 L0 n (M0 L0 n=Co(CO)4, L=PMe2Ph: Y=NPh2 (5), OEt (6), OMe (7), OiPr (8); M0 L0 n =Co(CO)4, L=PPh3: Y=OEt (9); M0 L0 n = Mn(CO)5, L = PMe2Ph: Y = OEt (10)), are synthesized by metathesis reactions of dichlorocarbene complexes with metalate Naþ[M0 L0 n]-. These complexes are characterized by NMR and IR spectroscopies and elemental analysis, and the molecular structures of 1, 2, and 6 are determined by X-ray structure analysis. Deprotonation of 6-10 with base gives heterodinuclear μ-alkoxystyrylplatinum-metal complexes, (L)(CO){μ-PhHCdYC}Pt-M0 L0 n-1 (M0 L0 n-1=Co(CO)3, L=PMe2Ph: Y=OEt (13), OMe (14), OiPr (15); M0 L0 n-1=Co(CO)3, L=PPh3: Y=OEt (16); M0 L0 n-1= Mn(CO)4, L = PMe2Ph: Y = OEt (12)), where the E isomer is thermodynamically stable. Z isomers of corresponding monomeric alkoxystyrylplatinum(II) complexes are found to be more stable than the corresponding E isomers. In contrast, both the dinuclear diphenylaminostyrylplatinum-cobalt complex and its mononuclear analogue favor the Z configuration.

Introduction Heterodinuclear complexes have attracted much attention due to a cooperative effect of the two different metals.1 We previously reported the synthesis of a series of heterodinuclear complexes having both an M-M0 bond and an M-C(or H) single bond, L2RM-M0 L0 n (M=Pt, Pd; M0 = Mo, W, Mn, Re, Fe, Co; R=Me, Et, CH2CMe3, Ph, COMe, COEt, COCH2CMe3, COPh, H; L2=cod, dppe, tmeda, bpy, phen, Ph2PC2H4NEt2, Ph2PC2H4SMe, Ph2PC2H4CHdCH2; L0 =CO, Cp) as the simplest model for active intermediates in bimetallic catalyses, some of which showed remarkable reactivities and catalytic activities.2 Synthesis and reactions of heterodinuclear complexes having a metal-carbon multiple bond are also considered to be valuable subjects to study, *To whom correspondence should be addressed. E mail: komiya@ cc.tuat.ac.jp. (1) (a) Ritleng, V.; Chetcuti, M. J. Chem. Rev. 2007, 107, 797. (b) Wheatley, N.; Kalck, P. Chem. Rev. 1999, 99, 3379. (2) (a) Fukuoka, A.; Sadashima, T.; Sugiura, T.; Wu, X.; Mizuho, Y.; Komiya, S. J. Organomet. Chem. 1994, 473, 139. (b) Fukuoka, A.; Sadashima, T.; Endo, I.; Ohashi, N.; Kambara, Y.; Sugiura, T.; Miki, K.; Kasai, N.; Komiya, S. Organometallics 1994, 13, 4033. (c) Komiya, S.; Muroi, S.; Furuya, M.; Hirano, M. J. Am. Chem. Soc. 2000, 122, 170. (d) Fukuoka, A.; Fukagawa, S.; Hirano, M.; Koga, N.; Komiya, S. Organometallics 2001, 20, 2065. (e) Furuya, M.; Tsutsuminai, S.; Nagasawa, H.; Komine, N.; Hirano, M.; Komiya, S. Chem. Commun. 2003, 2046. (f) Tsutsuminai, S.; Komine, N.; Hirano, M.; Komiya, S. Organometallics 2003, 22, 4238. (g) Tsutsuminai, S.; Komine, N.; Hirano, M.; Komiya, S. Organometallics 2004, 23, 44. (h) Kuramoto, A.; Nakanishi, N.; Kawabata, T.; Komine, N.; Hirano, M.; Komiya, S. Organometallics 2006, 25, 311. (i) Tanaka, S.; Hoh, H.; Akahane, Y.; Tsutsuminai, S.; Komine, N.; Hirano, M.; Komiya, S. J. Organomet. Chem. 2007, 692, 26. pubs.acs.org/Organometallics

Published on Web 09/02/2009

since carbene complexes constitute a center of organometallic reactions.3 As an extension of our work, we synthesized new heterodinuclear complexes having a MdC double bond, which is still relatively rare.4 One known example is trans[Pt(CNC6H11){C(OEt)(NHC6H11)}{MoCp(CO)3}2], reported by Braunstein et al. by the metathesis reaction of cis-[PtCl2(CNC6H11){C(OEt)(NHC6H11)}] with Naþ[MoCp(CO)3]-.5 In this paper, we report the synthesis of Fischer-type heterodinuclear (carbene)platinum (or palladium) complexes having tertiary phosphine ligands, (Ph3P)Cl(Me2NHC)M-M0 L0 n (M = Pt: M0 L0 n = Co(CO)4 (1), Mn(CO)5 (2), MoCp(CO)3 (3), FeCp(CO)2 (4); M=Pd: M0 L0 n=Co(CO)4 (33), Mn(CO)5 (34)) and (L)Cl{(PhCH2)YC}Pt-M0 L0 n (M0 L0 n = Co(CO)4, L=PMe2Ph: Y=NPh2 (5), OEt (6), OMe (7), OiPr (8); M0 L0 n= Co(CO)4, L=PPh3: Y=OEt (9); M0 L0 n=Mn(CO)5, L=PMe2Ph: Y = OEt (10)), by metathesis reactions of corresponding dichloro (carbene)platinum complexes with metalates Naþ[M0 L0 n]-. Formation of heterodinuclear μ-(E)-alkenyl complexes by deprotonation with a base is also described. (3) (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18. (b) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42, 4592. (c) Wu, Y. T.; Kurahashi, T.; Meijere, A. J. Organomet. Chem. 2005, 690, 5900. (4) (a) Graham, T. W.; Van Gastel, F.; McDonald, R.; Cowie, M. Organometallics 1999, 18, 2177. (b) Sterenberg, B. T.; McDonald, R.; Cowie, M. Organometallics 1997, 16, 2297. (c) Breen, M. J.; Shulman, P. M.; Geoffroy, G. L.; Rheingold, A. L.; Fultz, W. C. Organometallics 1984, 3, 782. (d) Fischer, E. O.; Offhaus, E.; Muller, J.; Nothe, D. Chem. Ber. 1972, 105, 3027. (e) Fischer, E. O.; Offhaus, E. Chem. Ber. 1969, 102, 2549. (5) Braunstein, P.; Keller, E.; Vahrenkamp, H. J. Organomet. Chem. 1979, 165, 233. r 2009 American Chemical Society

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Results and Discussion Synthesis of Heterodinuclear Aminocarbene Complexes (Ph3P)Cl(R2NHC)Pt-M0 L0 n. When cis-[PtCl2(PPh3)(CHNMe2)] was treated with 1.2-2.2 equiv of Naþ[M0 L0 n]- (M0 L0 n= Co(CO)4, Mn(CO)5, MoCp(CO)3, FeCp(CO)2) in THF at -20 °C, corresponding heterodinuclear dimethylaminocarbene complexes (Ph3P)Cl(Me2NHC)Pt-M0 L0 n (M0 L0 n = Co(CO)4 (1), Mn(CO)5 (2), MoCp(CO)3 (3), FeCp(CO)2 (4)) were obtained as yellow-orange crystals or powder in 58, 43, 40, and 61% yields, respectively (eq 1). Diphenylaminocarbene complex 5 was also prepared (eq 2).

Only monosubstituted products were obtained, even in the presence of an excess amount of metalate used. The results are in contrast to the formation of trinuclear isonitrile analogues reported by Braunstein.5 This may be due to the larger steric bulkiness of the PPh3 ligand than the isonitrile, preventing coordination of two M0 L0 n moieties to Pt. Selected NMR and IR data of 1-5 are summarized in Tables 1 and 2. In the 1H NMR, two methyl groups in the dimethylamino group are unequivalent, showing that they are diastereotopic. This result suggests the restricted rotation around the Pt-C and C-N bonds as previously reported for cis-[PtCl2(PPh3)(CHNMe2)]6a and other secondary aminocarbene complexes.6b The methine proton at the carbene carbon appears as a singlet at ca. δ 10. Molecular structures of 1 and 2 were determined by X-ray structure analysis. The crystallographic data and selected bond distances and angles are summarized in Tables 3 and 4, respectively, and ORTEP drawings are depicted in Figure 1. The Pt-C bond distances (1.970(14) A˚ (1 3 C6H6), 1.956(16) A˚ (2 3 2C6H6)) are significantly shorter than those in analogous heterodinuclear methylplatinum complexes, (dppe)MePt-Co(CO)4 (2.12(2) A˚)2d and (dppe)MePtMn(CO)5 (2.131(8) A˚),2c but similar to those in the known mononuclear carbene complexes cis-[PtCl2(PPh3)(CHNMe2)] (1.96(1) A˚),6a cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] (1.920(9) A˚),7 and trans-[Pt(CNR){C(OEt)(NHC6H11)}{MoCp(CO)3}2] (2.02(1) A˚).5 The Pt-Co (or -Mn) bond distances (2.662(2) A˚ (1 3 C6H6), 2.729(2) A˚ (2 3 2C6H6)) are similar to those of heterodinuclear methylplatinum complexes (dppe)MePt-Co(CO)4 (2.676(2) A˚) and (dppe)MePt-Mn(CO)5 (2.795(2) A˚). The estimated C-N bond lengths are relatively short, consistent with their partial multiple-bond character, which may prevent rotation of the C-N bond. The geometry at platinum was (6) (a) Barefield, E. K.; Carrier, A. M.; Sepelak, D. J.; Van Derveer, D. G. Organometallics 1982, 1, 103. (b) Christian, D. F.; Clark, H. C.; Stepaniak, R. F. J. Organomet. Chem. 1976, 112, 227. (7) Anderson, G. K.; Cross, R. J.; Manojlovic-Muir, L.; Muir, K. W.; Wales, R. A. J. Chem. Soc., Dalton Trans. 1979, 684.

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essentially square planar in both cases, where Co (or Mn) and PPh3 are trans to each other. Coordination geometries of the cobalt and manganese atoms are considered to be distorted tetrahedral and distorted trigonal bipyramidal, respectively, suggesting the actual metal valency of the d10-Co(-1) (or d8-Mn(-1)) anion and d8-Pt(II). The Co (or Mn) moiety is considered to bind to the platinum(II) cation, as both ligands at Pt and Co (or Mn) avoid steric repulsion. Although one carbonyl ligand C(22)-O(1) in 1 lies close to the platinum atom (Pt-C(22)=2.473(14) A˚), no strong bridging character may be involved, since the Co-C(22)-O(1) angle was close to 180°. IR spectra of 1 and 2 show strong ν(CO) bands at ca. 1900-2000 cm-1, which are similar to the other dinuclear complexes2 but slightly shifted to higher frequencies, and are also slightly higher than the known metalate complexes such as [PPN]þ[Co(CO)4]- (1886 cm-1) and [PPN]þ[Mn(CO)5](1861, 1894 cm-1).8 These may be interpreted by lower electron density of the Co(-1) (or Mn(-1)) moiety than the corresponding metalate by the electron-withdrawing Cl ligand at Pt(II). Synthesis of Heterodinuclear Alkoxycarbene Complexes (L)Cl{(PhCH2)(EtO)C}Pt-M0 L0 n. Metathesis reaction of mononuclear alkoxycarbene complexes cis-[PtCl2(L){CY(CH2Ph)}] (L=PMe2Ph, PPh3; Y=OEt, OMe, OiPr), with 1 equiv of Naþ[M0 L0 n]- (M0 L0 n =Co(CO)4, Mn(CO)5) also gave analogous heterodinuclear carbene complexes, (L)Cl{(PhCH2)YC}Pt-M0 L0 n (M0 L0 n = Co(CO)4, L = PMe2Ph: Y=OEt (6), OMe (7), OiPr (8); M0 L0 n=Co(CO)4, L=PPh3: Y=OEt (9); M0 L0 n=Mn(CO)5, L=PMe2Ph: Y=OEt (10)) (eq 3). In the 1H NMR spectra, both benzylic methylene protons and ethoxy methylene protons are observed at different chemical shifts, showing that they are also diastereotopic (Table 2). Rotation around the Pt-C bond in solution is also restricted.7 The X-ray structure analysis of 6 revealed a molecular structure in which the platinum adopted a square-planar geometry, and Co and PMe2Ph lie in a trans fashion (Figure 2, Table 4). The cobalt atom is considered to have a distorted tetrahedral structure, showing a similar electronic state of Pt and Co in the dinuclear aminocarbene complexes 1. The Pt-C (1.901(11) A˚) and Pt-Co (2.6404(16) A˚) distances are similar to those for 1 3 C6H6 (1.970(14) and 2.662(2) A˚, respectively).

In contrast to the above reactions, when cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] was treated with 1 equiv of Naþ[MoCp(CO)3]-, unexpected μ-alkenyl-type complex (PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-MoCp(CO)2 ((E)11) was obtained in ca. 50% yield. The yield increased to 69% when 2 equiv of Naþ[MoCp(CO)3]- was used (eq 4). In this reaction, formation of an equimolar amount of MoHCp(CO)3 was confirmed by 1H NMR, suggesting that the [MoCp(CO)3]- acted as a base to abstract a proton from the carbene ligand formed (vide infra). At the same time one (8) Thompson, D. M.; Bengouth, M.; Baird, M. C. Organometallics 2002, 21, 4762.

CHN

9.9 (brs, 1H)

1919 (s)c 1945 (s)c 2008 (m)c 2033 (s)c 1845 (m)d 1895(s)d 1927(s)d 1997 (s)d 2014 (s)d 2089 (m)d

10.4 (brd, 7 Hz, 1H)

9.9 (brs, 1H)

10.7 (brs, 1H)

10.4 (brs, 1H)

10.4 (brs, 1H)

10.4 (brs, JPtH = 20 Hz, 1H)

10.9 (brs, 1H)

10.6 (brs, JPtH = 23 Hz, 1H)

10.9 (brs, JPtH = 20 Hz, 1H)

10.4 (brs, 1H)

1868 (s) 1892 (s)

1854 (s) 1888 (s)

1883 (s)

1885 (s) 1897 (s) 1944 (s)

1895 (s) 1952 (s) 1966 (s) 2034 (s) 1907 (s) 1931 (s) 1946 (s) 1984 (s) 2054 (s) 1812 (s) 1827 (s) 1916 (s)

IR (νCO, cm-1)a

2.51 (brs, 3H) 2.80 (brs, 3H) 3.34 (brs, 3H) 3.67 (brs, 3H)

3.06 (brs, 3H) 3.20 (brs, 3H) 2.88 (brs, 3H) 2.98 (brs, 3H) 2.49 (brs, 3H) 3.18 (brs, 3H) 2.49 (brs, 3H) 3.17 (brs, 3H) 3.20 (brs, 3H) 3.43 (brs, 3H) 2.86 (brs, 3H) 3.06 (brs, 3H) 3.85 (brs, 3H) 3.88 (brs, 3H)

3.05 (brs, 3H) 3.20 (brs, JPtH = 10 Hz, 3H) 3.04 (brs, 3H) 3.18 (brs, JPtH = 10 Hz, 3H)

N(CH3)2

4.97 (s, 5H)

5.24 (s, 5H)

Cp

21.8 (s)

21.7 (s)

16.9 (s)

40 (br) 41.0 (brs, JPtP = 2038 Hz) 20.3 (s)

18.8 (s, JPtP = 2635 Hz)

19.0 (s, JPtP = 2633 Hz)

27.2 (s, JPtP = 2873 Hz)

31.9 (s, JPtP = 3356 Hz)

25.9 (s, JPtP = 3144 Hz)

19.9 (s, JPtP = 3824 Hz)

P{1H} NMR (ppm)b

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a IR spectra were measured by the KBr pellet method. b NMR spectra were measured in acetone-d6 at room temperature. c These are data of a mixture of 33 and 35 (33:35 = 86:14). d These are data of a mixture of 34 and 36 (34:36 = 57:43).

trans-[PdCl(PPh3)2(CHNMe2)]þ[Mn(CO)5]- (36)

trans-[PdCl(PPh3)2(CHNMe2)]þ[Co(CO)4]- (35)

(Ph3P)Cl(Me2NHC)Pd-Mn(CO)5 (34)

(Ph3P)Cl(Me2NHC)Pd-Co(CO)4 (33)

[PtCl(dppe)(CHNMe2)]þ[Co(CO)4]- (32)

trans-[PtCl(PPh3)2(CHNMe2)]þ[Mn(CO)5]- (31)

trans-[PtCl(PPh3)2(CHNMe2)]þ[Co(CO)4]- (30)

(Ph3P)Cl(Me2NHC)Pt-FeCp(CO)2 (4)

(Ph3P)Cl(Me2NHC)Pt-MoCp(CO)3 (3)

(Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2)

(Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1)

complex

H NMR (ppm)b

1

Table 1. Selected IR and NMR Data of Heterodinuclear Platinum (or Palladium) Complexes Having a Terminal Carbene

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a

1950 (s br) 2000 (s) 2023 (m) 2044 (s) 1915 (s) 1964 (s) 1984 (s) 2044 (s) 1927 (s) 1965 (s) 1984 (s) 2048 (s) 1911 (s) 1965 (s) 1981 (s) 2046 (s) 1922 (s) 1947 (s) 1978 (s) 2044 (s) 1942 (s br) 2060 (s)

IR (νCO, cm-1)a

0.90 (t, 7 Hz, 3H)

1.34 (d, 6 Hz, 3H) 1.63 (d, 6 Hz, 3H) 0.65 (t, 7 Hz, 3H)

1.57 (t, 7 Hz, 3H)

O-C-CH3

4.37 (m, 1H) 4.37 (m, 1H) 4.33 (dq, 11, 7 Hz, 1H) 4.69 (dq, 11, 7 Hz, 1H)

6.09 (sep, 6 Hz, 1H)

4.92 (dq, 11, 7 Hz, 1H) 5.10 (dq, 11, 7 Hz, 1H) 4.63 (s, 3H)

O-CHn 4.20 (dd, 13, 3 Hz, 1H) 4.51 (d, 13 Hz, 1H) 4.26 (d, 14 Hz, 1H) 4.45 (d, 14 Hz, 1H) 4.28 (d, 15 Hz, 1H) 4.38 (d, 15 Hz, 1H) 4.28 (d, 14 Hz, 1H) 4.65 (d, 14 Hz, 1H) 3.47 (d, 17 Hz, 1H) 4.4 (overlapped with OCH2, 1H) 3.96 (dd, 15, 3 Hz, 1H) 4.13 (dd, 15, 3 Hz, 1H)

CH2Ph

H NMR (ppm)b

IR spectra were measured by the KBr pellet method. b NMR spectra were measured in CD2Cl2 (5, 6, 7, 8) or C6D6 (9, 10) at room temperature.

(PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Mn(CO)5 (10)

(Ph3P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (9)

(PhMe2P)Cl{(PhCH2)(iPrO)C}Pt-Co(CO)4 (8)

(PhMe2P)Cl{(PhCH2)(MeO)C}Pt-Co(CO)4 (7)

(PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6)

(PhMe2P)Cl{(PhCH2)(Ph2N)C}Pt-Co(CO)4 (5)

complex

1

PCH3

1.08 (d, 11 Hz, 3H) 1.13 (d, 11 Hz, 3H)

1.52 (d, 11 Hz, JPtH = 43 Hz, 3H) 1.61 (d, 11 Hz, JPtH = 45 Hz, 3H)

1.10 (d, 11 Hz, JPtH = 37 Hz, 3H) 1.52 (d, 11 Hz, JPtH = 37 Hz, 3H) 1.59 (d, 11 Hz, JPtH = 42 Hz, 3H) 1.61 (d, 11 Hz, JPtH = 42 Hz, 3H) 1.64 (d, 11 Hz, JPtH = 43 Hz, 6H)

Table 2. Selected IR and NMR Data of Heterodinuclear Platinum Complexes Having a Terminal Carbene

-1.4 (s, JPtP = 2804 Hz)

22.1 (s, JPtP = 3581 Hz)

-4.3 (s, JPtP = 3502 Hz)

-4.5 (s, JPtP = 3498 Hz)

-4.3 (s, JPtP = 3520 Hz)

-6.1 (s, JPtP = 3558 Hz)

P{1H}NMR (ppm)b 31

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Table 3. Crystallographic Data for (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1), (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2), and (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6)a 1 3 C6H6 empirical formula fw cryst color, habit cryst dimens (mm  mm  mm) cryst syst space group a (A˚) b (A˚) c (A˚) R (deg) β (deg) γ (deg) V (A˚3) Z Dcalcd (g cm-3) F000 μ(Mo KR) (cm-1) scan type 2θmax (deg) no. of reflns measd

2 3 2C6H6

6

C31H28ClCoNO4PPt 799.02 yellow, needle 0.37  0.17  0.05

C38H34ClMnNO5PPt 901.15 amber, prismatic 0.49  0.33  0.13

C22H23ClCoO5PPt 687.87 light orange, needle 0.50  0.10  0.08

monoclinic C2/c (No. 15) 32.165(6) 9.543(7) 20.395(7)

triclinic P1 (No. 2) 11.80(17) 16.91(7) 9.15(3) 95.6(5) 91.1(6) 96.0(9) 1806.3(283) 2 1.657 888.00 43.631 ω-2θ 55.7 total: 7171 unique: 6827 (Rint = 0.035) Patterson methods 0.0800 0.2406 0.960

monoclinic P21/n (No. 14) 9.935(4) 26.390(10) 9.775(5)

95.394(19) 6232.5(48) 8 1.703 3120.00 51.706 ω-2θ 54.9 total: 7256 unique: 7131 (Rint = 0.123) Patterson methods 0.0628 0.1978 0.957

108.42(4)

2431.6(18) 4 1.879 1328.00 66.109 ω 55.0 total: 6716 unique: 5560 (Rint = 0.084) structure solution direct methods 0.0473 R1 (I > 2σ(I))b c 0.1462 wR2 goodness of fit indicator 0.924 P P a b ˚ Diffractometer: Rigaku P P AFC7R; radiation: 0.71069 A; temperature: -73.0 °C (1 3 C6H6, 2 3 2C6H6) or -73.1 °C (6). R1 = ||Fo| - |Fc||/ |Fo|. c wR2 = [ w(F2o - F2c )2/ w(F2o)2]1/2.

carbonyl ligand on Mo also transferred to Pt to form stable square-planar and piano-stool configurations.

Complex (E)-11 was characterized spectroscopically as well as by preliminary X-ray structure analysis. An ORTEP drawing of one of the two similar independent molecules is shown in Figure 3. The structures of Pt and Mo are squareplanar and distorted three-leg piano-stool, respectively, and the (E)-μ-alkenyl ligand links these metals. Preferential formation of the E isomer is observed, probably due to steric repulsion between phenyl and the Pt moiety attached to the CdC double bond. VT 1H and 31P{1H} NMR spectra of (E)-11 are shown in Figure 4 and Table 5. The diastereotopic methylene protons of the ethoxy group appear at δ 3.8 as one broad signal at 20 °C. On lowering the temperature, the signal gradually broadened and finally separated into two pairs of ill-separated double quartets (δ 4.02, 4.14 and δ 3.16, 3.50) in 1:0.7 ratio at -60 °C, which are assigned to the diastereotopic geminal protons of two diastereomeric isomers of (E)-11. The alkenyl proton signal also split into two peaks at δ 4.86 and 4.21 in the same ratio. A very broad phosphorus resonance at 20 °C shows a similar change on cooling, and at -60 °C two sharp singlets with 195Pt satellites are observed

at δ -1.9 (JPtH = 2802 Hz) and δ -11.1 (JPtH = 3126 Hz). Such a diastereomeric mixture is considered to be formed by different face-selected coordination of a prochiral CdC double bond to the chiral Mo atom. Therefore this dynamic behavior is interpreted by the facile dissociation and association of the alkenyl group at Pt to the molybdenum center (Scheme 1). On the contrary, heating to 80 °C caused coalescence of two sets of diastereotopic protons to give two second-order double quartets at δ 3.82 and 3.87 (JHH= 10, 7 Hz). At the same time, broad methyl signals of the PMe2Ph ligand appeared as two equal doublets with 195Pt satellites at δ 1.43 and 1.54 (JPH = 10 Hz, JPtH = 31 Hz), showing these methyl groups are also diastereotopic. Such diastereotopic nature of these protons even at 80 °C suggests involvement of chirality at Pt and/or Mo atoms even after dissociation of the CdC double bond from Mo. This may be because of the restricted rotation of the Pt-alkenyl bond, giving a diastereotopic environment of these protons as shown in Scheme 1. Alternatively restricted site exchange between Cp and one of the carbonyl ligands may also interpret this dynamic behavior. In contrast to the above result, reaction with 2 equiv of tetracarbonylcobaltate gave only a dinuclear carbene complex, whereas treatment of 2 equiv of pentacarbonyl managanate with the dicholocarbene complex afforded a 1:2 mixture of heterodinuclear carbene complex 10 and μ-alkenyl complex (PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-Mn(CO)4 ((E)-12). As expected, reaction of the isolated heterodinuclear

Scheme 1. Face-Selected Interconversion in the Diastereomeric Pair of (E)-11

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Organometallics, Vol. 28, No. 18, 2009 Table 4. Selected Bond Lengths and Angles for (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1), (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2), and (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6)

Bond Lengths (A˚) for (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1) Pt(1)-Co(1) Pt(1)-P(1) C(1)-N(1) Co(1)-C(23) Co(1)-C(25) C(23)-O(2) C(25)-O(4)

2.662(2) 2.275(3) 1.262(19) 1.762(19) 1.794(16) 1.15(2) 1.14(2)

Pt(1)-C(1) Pt(1)-Cl(1) Co(1)-C(22) Co(1)-C(24) C(22)-O(1) C(24)-O(3)

1.970(14) 2.393(3) 1.721(19) 1.748(17) 1.23(2) 1.19(2)

Bond Angles (deg) for (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1) Co(1)-Pt(1)-C(1) C(1)-Pt(1)-P(1) Co(1)-C(22)-O(1) Co(1)-C(24)-O(3) C(22)-Co(1)-C(23) C(22)-Co(1)-C(25) C(23)-Co(1)-C(25)

84.4(4) 93.6(4) 168.6(11) 175.8(15) 96.1(8) 115.3(8) 101.7(8)

Co(1)-Pt(1)-Cl(1) Cl(1)-Pt(1)-P(1) Co(1)-C(23)-O(2) Co(1)-C(25)-O(4) C(22)-Co(1)-C(24) C(23)-Co(1)-C(24) C(24)-Co(1)-C(25)

92.80(9) 89.68(11) 177(2) 177.0(16) 123.8(7) 104.2(9) 110.9(8)

Bond Lengths (A˚) for (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2) Pt(1)-Mn(1) Pt(1)-P(1) C(1)-N(1) Mn(1)-C(23) Mn(1)-C(25) C(22)-O(1) C(24)-O(3) C(26)-O(5)

2.729(2) 2.275(4) 1.30(2) 1.84(2) 1.90(2) 1.19(2) 1.15(2) 1.16(2)

Pt(1)-C(1) Pt(1)-Cl(1) Mn(1)-C(22) Mn(1)-C(24) Mn(1)-C(26) C(23)-O(2) C(25)-O(4)

1.956(16) 2.373(4) 1.760(15) 1.785(17) 1.813(17) 1.14(2) 1.11(2)

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[MoHCp(CO)3], 14.1 for [MnH(CO)5]).9 The cobalt anion is much less basic, thus discouraging proton abstraction. The reactivity difference between Mo and Mn anions in proton abstraction could arise from the stability difference of the products. Deprotonation of (L)Cl{(PhCH2)(EtO)C}Pt-M0 L0 n by Amine. As we discussed above, a μ-alkenyl-type complex is considered to be formed by abstraction of a benzylic proton of (L)Cl{(PhCH2)(EtO)C}Pt-M0 L0 n by a metalate anion probably as a base. Therefore, we carried out the reaction of the heterodinuclear carbene complex with amine as an organic base. When 6 was reacted with NEt3 in CD2Cl2, the μ-alkenyl-type complex (PhMe2P)(CO){μ-PhHCd(EtO)C}Pt-Co(CO)3 (13) was formed as an E/Z (82:18) mixture, supporting the above proton abstraction mechanism (eq 5, Table 6). The assignment of E/Z isomers was performed by the coupling constant of the terminal alkenyl proton with 195Pt in 1H NMR in CD2Cl2 (Table 5).10 The alkenyl proton signal at δ 5.67 due to the Z isomer ((Z)-13) couples with 195Pt (J=36 Hz), in which the Pt and H atoms are in trans position to each other, whereas the signal at δ 4.54 assignable to the E isomer ((E)-13) shows no 195Pt satellites.

Bond Angles (deg) for (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2) Mn(1)-Pt(1)-C(1) C(1)-Pt(1)-P(1) Mn(1)-C(22)-O(1) Mn(1)-C(24)-O(3) Mn(1)-C(26)-O(5) C(22)-Mn(1)-C(24) C(22)-Mn(1)-C(26) C(23)-Mn(1)-C(25) C(24)-Mn(1)-C(25) C(25)-Mn(1)-C(26)

85.3(5) 89.9(5) 168.6(19) 178.2(15) 177.0(16) 112.8(9) 142.6(9) 171.6(8) 85.6(8) 90.7(7)

Mn(1)-Pt(1)-Cl(1) 94.54(13) Cl(1)-Pt(1)-P(1) 89.40(15) Mn(1)-C(23)-O(2) 174.4(18) Mn(1)-C(25)-O(4) 174.4(18) C(22)-Mn(1)-C(23) 89.3(7) C(22)-Mn(1)-C(25) 91.9(7) C(23)-Mn(1)-C(24) 86.2(8) C(23)-Mn(1)-C(26) 93.4(7) C(24)-Mn(1)-C(26) 104.6(8)

Bond Lengths (A˚) for (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6) Pt(1)-Co(1) Pt(1)-P(1) C(1)-O(1) Co(1)-C(20) Co(1)-C(22) C(20)-O(3) C(22)-O(5)

2.6404(16) 2.276(2) 1.312(17) 1.780(16) 1.783(13) 1.16(2) 1.169(16)

Pt(1)-C(1) Pt(1)-Cl(1) Co(1)-C(19) Co(1)-C(21) C(19)-O(2) C(21)-O(4)

1.901(11) 2.386(3) 1.776(16) 1.754(12) 1.150(19) 1.176(15)

Bond Angles (deg) for (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6) Co(1)-Pt(1)-C(1) C(1)-Pt(1)-P(1) Co(1)-C(19)-O(2) Co(1)-C(21)-O(4) C(19)-Co(1)-C(20) C(19)-Co(1)-C(22) C(20)-Co(1)-C(22)

83.3(3) 97.9(3) 174.6(12) 177.8(13) 128.8(6) 109.7(7) 111.6(6)

Co(1)-Pt(1)-Cl(1) 92.48(8) Cl(1)-Pt(1)-P(1) 86.58(10) Co(1)-C(20)-O(3) 173.3(11) Co(1)-C(22)-O(5) 179.1(13) C(19)-Co(1)-C(21) 99.3(6) C(20)-Co(1)-C(21) 98.7(6) C(21)-Co(1)-C(22) 104.0(5)

(carbene)platinum-manganese complex 10 with excess manganate cleanly gave μ-alkenyl complex (E)-12, but (carbene)platinum-cobalt complex 6 did not react with excess metalate. From these results, the proton abstraction ability is considered to be in the order [MoCp(CO)3]->[Mn(CO)5]-.[Co(CO)4]-. The trend may partially reflect the difference of pKa values of these hydrides in acetonitrile (8.3 for [CoH(CO)4], 13.9 for

Slow isomerization of (Z)-13 to (E)-13 was observed to give a >95% E-rich mixture of 13 in 2 days at room temperature. When PhCH2NH2 was used as a base in the reaction with 6, the initial E/Z ratio (76:24) also increased to 95:5 in a day. This isomerization proceeded under dark in the same rate, implying that the isomerization is not a photoinduced reaction. The methoxy carbene complex 7 gave the μ-alkenyl-type complex 14, and the isomerization was also observed. The E/Z ratio after the isomerization of 14 was approximately equal to that of 13. When the isopropoxycarbene complex 8 and ethoxycarbene complex having PPh3 ligand 9 were reacted with NEt3, the E isomer was generated in E/Z = 92:8 and 91:9 ratio from the beginning, and no further isomerization was observed. In the case of the reaction of manganese complex 10 with NEt3, only the E isomer was obtained. The E isomer is considered to be thermodynamically more stable than the Z isomer for the dinulcear μ-alkenyl-type complex, probably due to larger steric repulsion among ligands in the Z isomer than the E isomer (Scheme 2). The fact that Pt-Mn complex 12 consists of only the E isomer may reflect the larger steric repulsion of the Mn(CO)4 unit compared to the Co(CO)3 unit. The isomerization mechanism from Z to E is not clear at present, but rotation of the C-C bond via (9) Tilset, M.; Parker, V. D. J. Am. Chem. Soc. 1989, 111, 6711. (10) (a) Mann, B. E.; Shaw, B. L.; Tucker, N. I. J. Chem. Soc. A 1971, 2667. (b) Rajaram, J.; Pearson, R. G.; Ibers, J. A. J. Am. Chem. Soc. 1974, 96, 2103.

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Figure 1. ORTEP drawings of (Ph3P)Cl(Me2NHC)Pt-M0 L0 n (M0 L0 n = Co(CO)4 (1), Mn(CO)5 (2)). All hydrogen atoms and solvent are omitted for clarity. Ellipsoids represent 50% probability.

Figure 2. ORTEP drawing of (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6). All hydrogen atoms are omitted for clarity. Ellipsoids represent 50% probability.

possible zwitterionic intermediates by resonance with an oxonium or platinum cation as shown in Scheme 3 may interpret the process. Scheme 2. Difference of Steric Environment

Scheme 3. Possible Mechanism of Isomerization

Figure 3. ORTEP drawing of (PhMe2P)(CO){(E)-μ-PhHCd (EtO)C}Pt-MoCp(CO)2 ((E)-11). One of two similar independent molecules is shown. All hydrogen atoms are omitted for clarity. Ellipsoids represent 50% probability.

It is of interest to compare the above E selectivity with the corresponding mononuclear analogue. Mononuclear alkoxystyryl complexes trans-[PtClL2{CYdCHPh}] (L = PMe2Ph: Y=OEt (23), OMe (24), OiPr (25); L=PPh3, Y=OEt (26)) were prepared by the reaction of the mononuclear carbene complexes cis-[PtCl2L{CY(CH2Ph)}] with triethylamine following treatment of 1 equiv of phosphine ligand (eq 6, Table 7). In these reactions uncharacterized alkenyl complexes (18-21)11 were initially formed, but they readily gave alkenyl complexes 23-26 by treatment with PMe2Ph at room temperature. Although initial E/Z ratios of 23-25 were different from each other, Z isomers gradually became the major product by isomerization in all cases. Complex 26, having PPh3, consisted of a mixture of Z-rich isomers from the beginning, and no further isomerization was observed. The (11) The complex is tentatively assigned as a mixture of dimeric (E)and (Z)-alkenylplatinum complexes by NMR (see Experimental Section).

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Figure 4. Variable-temperature 1H and 31P{1H} NMR spectra of (PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-MoCp(CO)2 ((E)-11).

result is unexpected, since the E isomer is generally believed to be more stable than the Z isomer for steric reasons.12 A higher thermodynamic stability of the Z isomer of the monomeric styrylplatinum complex is also found in the reaction of the heterodinuclear (E)-styryl complex with excess dimethylphenylphosphine. When in situ prepared complex 13 (E/Z=79:21) was treated with 1 equiv of PMe2Ph, a ligand exchange reaction took place to give a dinuclear bis(phosphine) complex, cis-(PhMe2P)2{μ-PhHCd(EtO)C}Pt-Co(CO)3 (28), with generation of an equimolar amount of CO (eq 7). Further addition of excess PMe2Ph led to heterolytic Pt-Co bond cleavage to give a cationic alkenyl complex, [Pt(PMe2Ph)3{C(OEt)dCHPh}]þ[Co(PMe2Ph)n(CO)m]- (29). The initial E/Z ratio (E/Z=78:22) of 29 was almost the same as the E/Z ratio of 13. However slow isomerization of (E)-29 to (Z)-29 took place to give a Z-rich (E/Z = 9:91) mixture in two days. These results indicate that the Z isomer is thermodynamically stable for monomeric alkoxystyrylplatinum(II) complexes. Such preferential formation of a Z isomer of an analogous alkenyl complex, trans-[PtMe(PPh3)2{C(OCH2(12) (a) Amatore, C.; Bensalem, S.; Ghalem, S.; Jutand, A. J. Organomet. Chem. 2004, 689, 4642. (b) Chatgilialoglu, C.; Ballestri, M.; Ferreri, C.; Vecchi, D. J. Org. Chem. 1995, 60, 3826. (13) Belluco, U.; Bertani, R.; Fornasiero, S.; Michelin, R. A.; Mozzon, M. Inorg. Chim. Acta 1998, 275-276, 515.

CH2Cl)dCH(p-tolyl)}], was known, although no details were described.13

Agostic interaction of the ortho proton of the styryl group with Pt is expected in these Z isomers. The 1H NMR chemical shift of the interacting proton with square-planar

IR (νCO, cm )

1948 (s br)c 2004 (s)c 2049 (s)c

(PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-Co(CO)3 ((E)-13)

O-CHn

0.81 (t, 7 Hz, 3H) 0.67 (t, 7 Hz, 3H)

(Ph3P)(CO){(E)-μ-PhHCd(EtO)C}Pt-Co(CO)3 ((E)-16)

CHPh

H NMR (ppm)b

d

2.04 (d, 10 Hz, JPtH = 34 Hz, 3H) 2.11 (d, 10 Hz, JPtH = 34 Hz, 3H) 2.07 (d, 11 Hz, JPtH = 40 Hz, 3H) 2.16 (d, 11 Hz, JPtH = 39 Hz, 3H)

1.1-1.4 (brm, 6H)

PCH3

P{1H} NMR (ppm)b

-14.1 (s, JPtP = 3246 Hz)

-12.2 (s, JPtP = 3339 Hz)

-2.1 (s, JPtP = 3003 Hz)

-11.1 (s, JPtP = 3126 Hz, minor) -1.9 (s, JPtP = 2802 Hz, major)

31

4.55 (s, 1H)

2.08 -12.3 (d, 11 Hz, JPtH = 40 Hz, 3H) (s, JPtP = 3329 Hz) 2.17 (d, 11 Hz, JPtH = 39 Hz, 3H) d 5.69 -14.1 (s, JPtP = 3235 Hz) (s, JPtH = 36 Hz, 1H) 4.57 2.05 -12.8 (s, 1H) (d, 11 Hz, JPtH = 40 Hz, 3H) (s, JPtP = 3385 Hz) 2.16 (d, 11 Hz, JPtH = 40 Hz, 3H) d 5.57 -13.3 (s)e (d, 1 Hz, JPtH = 37 Hz, 1H) 4.63 20.6 (s, 1H) (s, JPtP = 3384 Hz) 5.79 22.8 (s)e (d, 1 Hz, JPtH = 39 Hz, 1H) 5.15 1.65 -15.9 (d, 2 Hz, JPtH = 41 Hz, 1H) (d, 11 Hz, JPtH = 37 Hz, 3H) (s, JPtP = 3275 Hz) 1.86 (d, 11 Hz, JPtH = 38 Hz, 3H)

5.67 (d, 2 Hz, JPtH = 36 Hz, 1H)

4.54 (s, 1H)

3.73 (d, 4 Hz, 1H)

4.21 (s, 1H, minor) 4.86 (s, 1H, major)

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a IR spectra were measured by the KBr pellet method. b NMR spectra were measured in CD2Cl2 (12, 13, 14, 15, 16, 17) or C6D5CD3 ((E)-11) at room temperature (12, 13, 14, 15, 16, 17) or -60 °C ((E)-11). c These are data of a mixture of (E)-13 and (Z)-13 ((E)-13:(Z)-13 = 82:18). d These minor product peaks were not distinguished by overlapping. e 195Pt satellite peaks were too small to observe.

(PhMe2P)(CO){(Z)-μ-PhHCd(Ph2N)C}Pt-Co(CO)3 ((Z)-17)

(Ph3P)(CO){(Z)-μ-PhHCd(EtO)C}Pt-Co(CO)3 ((Z)-16)

3.60 (m, 2H) 3.44 (m, 2H)

d

d

(PhMe2P)(CO){(Z)-μ-PhHCd(iPrO)C}Pt-Co(CO)3 ((Z)-15)

(PhMe2P)(CO){(E)-μ-PhHCd(iPrO)C}Pt-Co(CO)3 ((E)-15)

3.46 (s, 3H) 1.11 4.38 (d, 6 Hz, 3H) (sep, 6 Hz, 1H) 1.36 (d, 6 Hz, 3H)

3.16 (brm, 1H, minor) 3.50 (brm, 1H, minor) 4.02 (brm, 1H, major) 4.14 (brm, 1H, major) 1.29 3.92 (t, 7 Hz, 3 H) (m, 1H) 3.99 (m, 1H) 1.26 3.65 (t, 7 Hz, 3H) (dq, 7, 10 Hz, 1H) 3.89 (dq, 7, 10 Hz, 1H) 1.19 3.48 (t, 7 Hz, 3H) (dq, 7, 10 Hz, 1H) 3.78 (dq, 7, 10 Hz, 1H) 3.59 (s, 3H)

0.8-1.1 (brm, 3H)

O-C-CH3

(PhMe2P)(CO){(Z)-μ-PhHCd(MeO)C}Pt-Co(CO)3 ((Z)-14)

(PhMe2P)(CO){(E)-μ-PhHCd(MeO)C}Pt-Co(CO)3 ((E)-14)

(PhMe2P)(CO){(Z)-μ-PhHCd(EtO)C}Pt-Co(CO)3 ((Z)-13)

1929 (s br) 2009 (s) 2046 (s)

(PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-Mn(CO)4 ((E)-12)

(PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-MoCp(CO)2 ((E)-11) 1828 (s) 1897 (s) 2008 (s)

complex

-1 a

Table 5. Selected IR and NMR Data of μ-Alkenyl-Type Complexes

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Table 6. Formation of μ-Alkenyl-Type Complexes by Deprotonation of Heterodinuclear Carbene Complexes substrate amine 6

NEt3

6

PhCH2NH2

7

NEt3

8

NEt3

9

NEt3

10

NEt3

5

NEt3

time (h) 0.1 5 55 0.3 2 29 0.1 5 53 0.1 5 24 0.1 1 30 0.1 1 5 0.1 18 98

conversion (%) 92 100 100 82 100 100 100 100 100 100 100 100 97 100 100 86 100 100 0 26 100

product yield E:Z (%) 13 85 82:18 99 83:17 95 96:4 13 54 76:24 94 76:24 94 95:5 14 100 81:19 100 85:15 98 95:5 15 99 92:8 99 92:8 99 92:8 16 96 91:9 100 91:9 100 91:9 12 83 100:0 100 100:0 100 100:0 17 0 26 0:100 95 0:100

Figure 5. Structure of trans-[PtCl(PH3)2{C(OMe)dCHPh}] estimated by DFT calculation. Table 7. E/Z Ratio of Mononuclear Alkenyl Complexes complex

time (h)

yield (%)

23

0.1 75 0.1 80 0.2 70 0.1 76 0.1 21

85 85 99 100 83 79 79 92 93 96

24

Pt(II) is known to be used as an indicator of the agostic interaction, although the value of the 195Pt satellites is better direct evidence. Pregosin previously reported that the closer position of a certain proton above the square-planar Pt(II) metal results in lower field shift, but sometimes without 195Pt satellites.14 In the present case, the chemical shift of the ortho proton of the (Z)-ethoxystyrylplatinum complex (Z)-13 is 0.7-0.8 ppm lower than that of free (E)-β-ethoxystyrene, whereas the ortho proton of (E)-ethoxystyrylplatinum (E)-13 is shifted to higher field by 0.24 ppm than that of free (Z)-βethoxystyrene.15 This result suggests that the mononuclear (Z)-R-ethoxystyryl complex intrinsically has an interaction with Pt, but the E isomer does not. Although the reason for the unusual Z-preferred formation for the alkoxystyrylplatinum(II) complex is not well understood at present, we believe that the alkoxystyrylplatinum(II) complex has an intrinsic agnostic interaction with one of the ortho protons of the styryl group, which forces the Z structure. In order to understand the reason for the higher stability of (Z)-ethoxystyrylplatinum(II), the structures of both Z and E isomers of trans-[PtCl(PH3)2(C(OMe)dCHPh)] were estimated by DFT calculation, as shown in Figure 5. The phenyl group is slightly twisted from the CdC plane by 27.77° in the Z isomer as if one of the ortho hydrogens makes direct close contact with Pt (o-H 3 3 3 Pt=2.723 A˚), whereas both the CdC plane and phenyl ring are completely placed in the same plane due to a resonance between phenyl and the CdC bond for the E isomer (dihedral angle=4.04°). These results probably indicate a weak but significant interaction of the ortho hydrogen with Pt in the Z isomer, although no bonding orbital interaction of the ortho hydrogen with Pt was found. (14) Albinati, A.; Pregosin, P. S.; Wombacher, F. Inorg. Chem. 1990, 29, 1812. (15) 1H NMR (rt, CD2Cl2) of (E)-β-ethoxystyrene:23a δ 1.35 (t, JHH= 7 Hz, OCH2CH3, 3H), 3.92 (q, JHH=7 Hz, OCH2, 2H), 5.85 (d, JHH=13 Hz, dCH, 1H), 7.05 (d, JHH=13 Hz, dCH, 1H), 7.1-7.2 (m, p-Ph, 1H), 7.2-7.3 (m, o- and m-Ph, 4H). 1H NMR (rt, CD2Cl2) of (Z)-β-ethoxystyrene:23b δ 1.38 (t, JHH=7 Hz, OCH2CH3, 3H), 4.01 (q, JHH=7 Hz, OCH2, 2H), 5.23 (d, JHH=7 Hz, dCH, 1H), 6.27 (d, JHH=7 Hz, dCH, 1H), 7.15 (t, JHH=7 Hz, pPh, 1H), 7.30 (t, JHH=7 Hz, m-Ph, 2H), 7.60 (d, JHH=7 Hz, o-Ph, 2H).

25 26 27

E/Z 66:34 21:79 46:54 18:82 70:30 21:79 12:88 13:87 0:100 0:100

Deprotonation of diphenylaminocarbene complex 5 with NEt3 gave (Z)-diphenylaminostyrylplatinum-cobalt complex 17, which did not isomerize to the E isomer (eq 5, Table 6). The reaction of the corresponding mononuclear complex with PMe2Ph and NEt3 also gave only the Z isomer of diphenylaminostyrylplatinum complex 27 (eq 6, Table 7). In this case, the stability of the Z isomer may be mainly due to effective steric hindrance between NPh2 and Ph substitutents across the CdC double bond in addition to an agnostic interaction of the ortho hydrogen with Pt. Reaction of (Ph3P)Cl(Me2NHC)Pt-M0 L0 n with Tertiary Phosphine Ligand. When 1 and 2 were treated with an equimolar amount of PPh3 in acetone at room temperature, smooth heterolytic cleavage of the metal-metal bond took place to give ionic complexes trans-[PtCl(PPh3)2(CHNMe2)]þ[M0 L0 n] (M0 L0 n=Co(CO)4 (30), Mn(CO)5 (31)) (eq 8).

Such ionization reactions were reported for other heterodinuclear alkylplatinum complexes.2b,2f 1H NMR of 30 showed a singlet due to carbene proton resonance at δ 10.4 (brs, JPtH= 20 Hz) (Table 1). 31P{1H} NMR shows a singlet at δ 19.0 (s, JPtP=2633 Hz), indicating two triphenylphosphine ligands are located in a trans fashion. The CO stretching absorption band (1883 cm-1) was almost the same as that of [PPN]þ[Co(CO)4](1886 cm-1).8 The molar electric conductivity of 30 was found to be very large (Λ (THF, rt)=18 S cm2 mol-1), supporting its

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ionic structure. When 1 was reacted with 1,2-bis(diphenylphosphino)ethane (dppe), ligand displacement also took place to give an analogous ionic carbene complex, [PtCl(dppe)(CHNMe2)]þ[Co(CO)4]- (32) (eq 9).

Attempted Preparation of Heterodinuclear (Carbene)palladium-Metal Complexes (Ph3P)Cl(Me2NHC)Pd-M0 L0 n. To expand the scope of the synthesis, we conducted the reaction of analogous palladium carbene complex cis-[PdCl2(PPh3)(CHNMe2)] with 1 equiv of Naþ[M0 L0 n]-. As a result, expected heterodinuclear complexes (Ph3P)Cl(Me2NHC)Pd-M0 L0 n (M0 L0 n = Co(CO)4 (33), Mn(CO)5 (34)) were formed, although ionic bis(phosphine) complexes trans-[PdCl(PPh3)2(CHNMe2)]þ[M0 L0 n]- (M0 L0 n = Co(CO)4 (35), Mn(CO)5 (36)) were always contaminated (eq 10), preventing isolation of pure compounds.

The NMR and IR data of these complexes are summarized in Table 1. Addition of PPh3 to the mixture increased the signal intensity of 35 (or 36).

Summary The metathesis reactions of (carbene)platinum complexes having chloro ligands with Naþ[M0 L0 n]- gave heterodinuclear (carbene)platinum complexes (Ph3P)Cl(Me2NHC)Pt-M0 L0 n (M0 L0 n =Co(CO)4 (1), Mn(CO)5 (2), MoCp(CO)3 (3), FeCp(CO)2 (4)) and (L)Cl{(PhCH2)YC}Pt-M0 L0 n (M0 L0 n = Co(CO)4, L=PMe2Ph: Y=NPh2 (5), OEt (6), OMe(7), OiPr (8); M0 L0 n=Co(CO)4, L=PPh3: Y=OEt (9); M0 L0 n =Mn(CO)5, L = PMe2Ph: Y = OEt (10)). On the other hand, cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] reacted with Naþ[MoCp(CO)3]- to give unexpected μ-alkenyl-type Pt-Mo complex (E)-11. Heterodinuclear μ-alkyenylplatinum-metal complexes 12-17 were also prepared by deprotonation of 5-10 by metalate or amine as a base. Heterodinuclear alkoxystyryl complex favored the E form, although the corresponding mononuclear complex consisted of a Z isomer. Treatments of 1 and 2 with PPh3 or dppe caused heterolytic cleavage of the Pt-M bond to give cationic (carbene)platinum complexes 30-32. The metathesis reaction can also be applied to prepare heterodinuclear (carbene)palladium complexes 33 and 34, although contamination of the corresponding ionic bisphosphine complexes was involved.

Experimental Section All manipulations were carried out under a dry nitrogen or argon atmosphere using standard Schlenk techniques. Solvents were dried over and distilled from appropriate drying agents under N2: hexane, benzene, toluene, diethyl ether, and THF from Na/benzophenone ketyl; CH2Cl2 from P2O5; acetone from Drierite. NMR solvents were commercially obtained and dried

Tanaka et al. with appropriate drying agents before use (C6D6, toluene-d8, and THF-d8 from Na; CD2Cl2 and CDCl3 from P2O5; acetoned6 from Drierite). [Pt(μ-Cl)Cl(PMe2Ph)]2,16,17 [Pt(μ-Cl)Cl(PPh3)]2,17 cis-[PtCl2(PPh3)(CHNMe2)],6a cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}],7 cis-[PtCl2(PMe2Ph){C(OMe)(CH2Ph)}],7 cis-[PdCl2(PPh3)(CHNMe2)],18 cis-[PtCl2(PMe2Ph){C(NPh2)(CH2Ph)}],19 Naþ[Co(CO)4]-,20 Naþ[Mn(CO)5]-,21 Naþ[MoCp(CO)3]-,22 and Naþ[FeCp(CO)2]-22 were prepared by the literature methods with minor modifications. Authentic samples of (E)- and (Z)-β-ethoxystyrene were also synthesized by the literature methods.23 NMR spectra were recorded on a JEOL LA-300 (300.4 MHz for 1H, 121.6 MHz for 31P) or a JEOL ECX-400P (399.8 MHz for 1H, 161.8 MHz for 31P) spectrometer. Chemical shifts were reported in ppm downfield from TMS for 1H and from 85% H3PO4 in D2O for 31P. IR spectra were recorded on a JASCO FT/IR-410 or JASCO FT/IR-4100 spectrometer using KBr disks. Elemental analyses were carried out with a Perkin-Elmer 2400 series II CHN analyzer. Gas chromatography was carried out using a Shimadzu GC-8A instrument. Molar electric conductivity was measured on a TOA Conduct Meter CM 7B. Synthesis of Mononuclear (Carbene)platinum Complexes. cis[PtCl2(PMe2Ph){C(OiPr)(CH2Ph)}]. This was synthesized by an analogous method to that for cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] and cis-[PtCl2(PMe2Ph){C(OMe)(CH2Ph)}].7 [Pt(μCl)Cl(PMe2Ph)]2 (96.6 mg, 0.120 mmol) was dissolved in CHCl3 (13 mL), and then 2-propanol (0.8 mL, 10 mmol) and phenylacetylene (41 μL, 0.37 mmol) were added to the solution. The solution was refluxed for 3 h. All the volatile matter was evaporated, and the resultant solid was reprecipitated from CH2Cl2/hexane to give a brown solid. Yield: 85% (114.7 mg, 0.2025 mmol). 1H NMR (rt, CDCl3): δ 1.31 (d, JHH = 6 Hz, OCH(CH3)2, 3H), 1.62 (d, JPH=11 Hz, JPtH=45 Hz, PCH3, 3H), 1.64 (d, JHH = 6 Hz, OCH(CH3)2, 3H), 1.71 (d, JPH = 11 Hz, JPtH=45 Hz, PCH3, 3H), 4.01 (d, JHH=17 Hz, CH2Ph, 1H), 4.12 (d, JHH=17 Hz, CH2Ph, 1H), 6.41 (sep, JHH=6 Hz, OCH, 1H). 31 P{1H} NMR (rt, CDCl3): δ -17.3 (s, JPtP =3770 Hz). cis-[PtCl2(PPh3){C(OEt)(CH2Ph)}]. This was prepared analogously to that above using [Pt(μ-Cl)Cl(PPh3)]2 (62.9 mg, 0.0595 mmol), ethanol (0.6 mL, 10 mmol), and phenylacetylene (33 μL, 0.30 mmol). The resultant solid was recrystallized from CH2Cl2/hexane to give pale yellow crystals. Yield: 30% (21.2 mg, 0.0362 mmol). 1H NMR (rt, CDCl3): δ 1.43 (t, JHH = 7 Hz, OCH2CH3, 3H), 3.31 (d, JHH = 19 Hz, CH2Ph, 1H), 3.97 (d, JHH=19 Hz, CH2Ph, 1H), 4.91 (dq, JHH=10, 7 Hz, OCH2, 1H), 5.76 (dq, JHH = 10, 7 Hz, OCH2, 1H). 31P{1H} NMR (rt, CDCl3): δ 9.3 (s, JPtP =4019 Hz). Synthesis of Heterodinucler (Carbene)platinum (or palladium) Complexes (1-10, 33, 34). A typical procedure for (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 3 C6H6 (1 3 C6H6) is given. Naþ[Co(CO)4]- (70.9 mg, 0.366 mmol) was dissolved in THF (18 mL). The solution was added to a THF (22 mL) solution of cis-[PtCl2(PPh3)(CHNMe2)] (176.2 mg, 0.3010 mmol) at -70 °C. Then the mixture was stirred for 3 h at -20 °C to give a yellow solution with a little white suspension. All the volatile matter was evaporated, and the resultant solid was extracted with benzene (5 mL  6). After removal of benzene in a vacuum, the residual orange solid (16) Baratta, W.; Pregosin, P. S. Inorg. Chim. Acta 1993, 209, 85. (17) Boag, N. M.; Ravetz, M. S. J. Chem. Soc., Dalton Trans. 1995, 3473. (18) McCrindle, R.; McAlees, A. J.; Zang, E.; Ferguson, G. Acta Crystallogr. 2000, C56, e132. (19) Cross, R. J.; Davidson, M. F.; Rocamora, M. J. Chem. Soc., Dalton Trans. 1988, 1147. (20) Edgell, W. F.; Lyford, J. Inorg. Chem. 1970, 9, 1932. (21) Hieber, W.; Faulhaber, G.; Theubert, F. Z. Anorg. Allg. Chem. 1962, 314, 125. (22) Piper, T. S.; Wilkinson, G. J. Inorg. Nucl. Chem. 1956, 3, 104. (23) (a) (E isomer) Park, H.; Kim, D. H.; Yoo, M. S.; Park, M.; Jew, S. Tetrahedron Lett. 2000, 41, 4579. (b) (Z isomer) Baldwin, J. E.; Walker, L. E. J. Org. Chem. 1966, 31, 3985.

Article was dissolved in a mixture of benzene and THF. The solution was then concentrated, and hexane was added to give yellow needles of 1 3 C6H6. Yield: 58% (139.2 mg, 0.1742 mmol). Anal. Calcd for C31H28ClCoNO4PPt: C, 46.60; H, 3.53; N, 1.75. Found: C, 46.67; H, 3.74; N, 1.77. Molar electric conductivity Λ (THF, rt): 0.030 S cm2 mol-1. 1H and 31P{1H} NMR and IR data are given in Table 1. Complexes 2-10, 33, and 34 were synthesized similarly. 1H and 31P{1H} NMR and IR data of 2-10, 33, and 34 are summarized in Tables 1 and 2. Following are yield, analytical data, and some physical data. Complexes 3-5, 7-10, 33, and 34 were characterized spectroscopically. (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 3 2C6H6 (2 3 2C6H6). Naþ[Mn(CO)5]- was used instead of Naþ[Co(CO)4]-. Orange crystals. Yield: 43%. Anal. Calcd for C38H34ClMnNO5PPt: C, 50.65; H, 3.80; N, 1.55. Found: C, 50.10; H, 4.15; N, 1.56. Molar electric conductivity Λ (THF, rt): 0.059 S cm2 mol-1. (Ph3P)Cl(Me2NHC)Pt-MoCp(CO)3 (3). Naþ[MoCp(CO)3]was used instead of Naþ[Co(CO)4]-. CH2Cl2 was used for extraction instead of benzene. Yellow microcrystals from CH2Cl2/ hexane. Yield: 40%. (Ph3P)Cl(Me2NHC)Pt-FeCp(CO)2 (4). Naþ[FeCp(CO)2]was used instead of Naþ[Co(CO)4]-. Orange powder. Yield: 61%. Recrystallization from benzene/hexane gave dark brown crystals, with low yield (6%). (PhMe2P)Cl{(PhCH2)(Ph2N)C}Pt-Co(CO)4 (5). cis-[PtCl2(PMe2Ph){C(NPh2)(CH2Ph)] was used instead of cis-[PtCl2(PPh3)(CHNMe2)]. The resultant brown solid after removal of benzene contained impurities. The impurities were deposited from benzene/hexane to give a brown solid of 5. Yield: 31%. (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6). cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)] was used instead of cis-[PtCl2(PPh3)(CHNMe2)]. CH2Cl2 was used for extraction instead of benzene. Orange crystals from CD2Cl2/hexane. Yield: 58%. Anal. Calcd for C22H23ClCoO5PPt: C, 38.41; H, 3.37. Found: C, 38.37; H, 3.51. (PhMe2P)Cl{(PhCH2)(MeO)C}Pt-Co(CO)4 (7). cis-[PtCl2(PMe2Ph){C(OMe)(CH2Ph)] was used instead of cis-[PtCl2(PPh3)(CHNMe2)]. CH2Cl2 was used for extraction instead of benzene. Yellow-brown solid. Yield: 76%. (PhMe2P)Cl{(PhCH2)(iPrO)C}Pt-Co(CO)4 (8). cis-[PtCl2(PMe2Ph){C(OiPr)(CH2Ph)] was used instead of cis-[PtCl2(PPh3)(CHNMe2)]. CH2Cl2 was used for extraction instead of benzene. Orange crystals from THF/hexane. Yield: 27%. (Ph3P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (9). cis-[PtCl2(PPh3){C(OEt)(CH2Ph)] was used instead of cis-[PtCl2(PPh3)(CHNMe2)]. Yellow powder. Yield: 66%. (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Mn(CO)5 (10). cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)] and Naþ[Mn(CO)5]- were used instead of cis-[PtCl2(PPh3)(CHNMe2)] and Naþ[Co(CO)4]-, respectively. Dark brown oil. Yield: 92%. The amount of Naþ[Mn(CO)5]- used should be exactly 1 equiv to platinum. When excess Naþ[Mn(CO)5]- was used, 12 was contaminated. (Ph3P)Cl(Me2NHC)Pd-Co(CO)4 (33). Reaction of cis[PdCl2(PPh3)(CHNMe2)] with Naþ[Co(CO)4]- was conducted in THF for 0.7 h at -50 to -70 °C. After the reaction, excess hexane was added to precipitate a dark brown solid, and then the solid was extracted with toluene. The extract was directly added to cold hexane to precipitate the product. A brown solid containing a mixture of 33 and 35 was obtained. Yield: 12% (33), 2% (35). (Ph3P)Cl(Me2NHC)Pd-Mn(CO)5 (34). The reaction of cis[PdCl2(PPh3)(CHNMe2)] with Naþ[Mn(CO)5]- was conducted in THF at -40 °C for 0.3 h. After the reaction, solvent was evaporated at -30 °C and the residue was then extracted with toluene. Addition of excess hexane gave a brown solid containing a mixture of 34 and 36. Yield: 44% (34), 20% (36). Synthesis of Heterodinuclear μ-AlkoxystyrylplatinumMolybdenum Complex (PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-MoCp(CO)2 ((E)-11). Naþ[MoCp(CO)3]- (148.1 mg, 0.5525 mmol) in THF (9 mL) was added to a THF (20 mL)

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solution of cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)] (151.6 mg, 0.2745 mmol) at -70 °C. Then the mixture was stirred for 3 h at -20 °C to give an orange solution with a small amount of white precipitates. Solvent was evaporated, and the resultant solid was extracted with benzene (5 mL  5). After removal of all volatile matters in a vacuum, the residual orange solid was recrystallized from THF/hexane to give orange crystals of (PhMe2P)(CO){(E)-μ-PhHCd(EtO)C}Pt-MoCp(CO)2 ((E)-11). Yield: 69% (136.8 mg, 0.1886 mmol). Anal. Calcd for C26H27MoO4PPt: C, 43.04; H, 3.75. Found: C, 43.79; H, 3.98. Reaction of (L)Cl{(PhCH2)(EtO)C}Pt-M0 L0 n (5-10) with Triethylamine. A typical procedure is given. (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6) (7.0 mg, 0.010 mmol) was dissolved in CD2Cl2. Then dibenzyl (0.0031 mmol) in CD2Cl2 was added as an internal standard. After addition of NEt3 (0.010 mmol), NMR spectra were periodically measured at 30 °C to monitor the reaction. Reaction of in Situ Prepared Alkoxystyrylplatinum(II) Complex with Tertiary Phosphine Ligand. A typical procedure was given. Ethoxystyrylplatinum(II) complex was in situ prepared by the reaction of cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] with NEt3. cis-[PtCl2(PMe2Ph){C(OEt)(CH2Ph)}] (7.8 mg, 0.014 mmol) was dissolved in CD2Cl2, and then 1,2-dimethoxyethane (0.0096 mmol) was added as an internal standard. NMR analysis immediately after addition of NEt3 (0.014 mmol) revealed the formation of a mixture of dimeric (E)- and (Z)alkenyl complexes (18) (conv. 100%, yield 56% (E), 29% (Z)), although the isolation and its full characterization were unsuccessful. Ratio of the coordinated PMe2Ph and the alkenyl group was 1:1, suggesting a dimeric structure rather than a putative three-coordinate structure for 18, [Pt(μ-Cl)(PMe2Ph){C(OEt)d CHPh}]2. 1H NMR (rt, CD2Cl2): δ 4.08 (brm, OCH2 of (E)-18 or (Z)-18, 1H), 4.19 (brm, OCH2 of (E)-18 or (Z)-18, 1H), 4.47 (brm, OCH2 of (E)-18 or (Z)-18, 2H), 5.06 (s, JPtH = 36 Hz, CHPh of (E)-18, 1H), 5.96 (brs, JPtH =76 Hz, CHPh of (Z)-18, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -16.6 (s, JPtP=4596 Hz, (E)18 or (Z)-18), -17.9 (s, JPtP =4600 Hz, (E)-18 or (Z)-18). The following complexes were also prepared in situ by the reaction of cis-[PtCl2(L){CY(CH2Ph)}] with NEt3. [Pt(μ-Cl)(PMe2Ph){C(OMe)dCHPh}]2 (19): 1H NMR (rt, CD2Cl2): δ 3.74 (s, OCH3 of (E)-19 or (Z)-19, 3H), 4.02 (s, OCH3 of (E)-19 or (Z)-19, 3H), 5.05 (s, JPtH =36 Hz, CHPh of (E)-19, 1H), 5.94 (s, JPtH=75 Hz, CHPh of (Z)-19, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -16.6 (s, JPtP=4581 Hz, (E)-19 or (Z)-19), -17.6 (s, JPtP =4589 Hz, (E)-19 or (Z)-19). [Pt(μ-Cl)(PMe2Ph){C(OiPr)dCHPh}]2 (20): 1H NMR (rt, CD2Cl2): All peaks were broad and difficult to assign. 31P{1H} NMR (rt, CD2Cl2): δ -15.9 (s, JPtP=4610 Hz, (E)-20 or (Z)-20), -17.2 (s, JPtP =4596 Hz, (E)-20 or (Z)-20). [Pt(μ-Cl)(PPh3){C(OEt)dCHPh}]2 (21): 1H NMR (rt, CD2Cl2): δ 3.86 (brm, OCH2 of (E)-21 or (Z)-21, 2H), 4.33 (brm, OCH2 of (E)-21 or (Z)-21, 2H), 5.09 (brs, CHPh of (E)-21 or (Z)21, 1H), 5.40 (brs, CHPh of (E)-21 or (Z)-21, 1H). 31P{1H} NMR (rt, CD2Cl2): δ 11.0 (s, JPtP=4885 Hz, (E)-21 or (Z)-21), 11.2 (s, JPtP =4870 Hz, (E)-21 or (Z)-21). To the above solution of 18, PMe2Ph (0.014 mmol) was added and NMR spectra were measured. 18 completely disappeared and instead formation of a mixture of new (E)- and (Z)-alkenyl complexes trans-[PtCl(PMe2Ph)2{C(OEt)dCHPh}] (23) was observed in 56% and 29% yields (66:34), respectively. The NMR sample tube was placed in an oil bath at 30 °C, and NMR was periodically monitored to follow the E/Z isomerization. After 75 h, yields of the (E)- and (Z)-alkenyl complexes became 18% and 67% (21:79). (E)-23, 1H NMR (rt, CD2Cl2): δ 1.15 (t, JHH=7 Hz, OCH2CH3, 3H), 1.81 (vt, JPH=3 Hz, 195Pt satellite peaks were not observed by overlapping, PCH3, 3H), 1.84 (vt, JPH =3 Hz, JPtH =32 Hz, PCH3, 3H), 4.10 (q, JHH = 7 Hz, OCH2, 2H), 5.12 (s, JPtH = 42 Hz, CHPh, 1H), 6.94 (t, JHH=7 Hz, p-Ph of dCHPh, 1H), 7.16 (t, JHH=8 Hz, m-Ph of dCHPh, 2H), 7.36 (d, JHH =8 Hz, o-Ph of dCHPh, 2H), 7.46

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(m, m- and p-Ph of PMe2Ph, 3H), 7.79 (m, o-Ph of PMe2Ph, 2H). 31 P{1H} NMR (rt, CD2Cl2): δ -6.06 (s, JPtP=2802 Hz). (Z)-23, 1 H NMR (rt, CD2Cl2): δ 1.14 (t, JHH =7 Hz, OCH2CH3, 3H), 1.64 (vt, JPH =4 Hz, JPtH =33 Hz, PCH3, 3H), 1.77 (vt, JPH = 4 Hz, JPtH=32 Hz, PCH3, 3H), 3.68 (q, JHH=7 Hz, OCH2, 2H), 5.93 (s, JPtH = 90 Hz, CHPh, 1H), 6.96 (t, JHH = 7 Hz, p-Ph of dCHPh, 1H), 7.11 (t, JHH=8 Hz, m-Ph of dCHPh, 2H), 7.38 (m, m- and p-Ph of PMe2Ph, 3H), 7.64 (m, o-Ph of PMe2Ph, 2H), 7.99 (d, JHH =8 Hz, o-Ph of dCHPh, 2H). 31P{1H} NMR (rt, CD2Cl2): δ -7.45 (s, JPtP =2846 Hz). Reactions of 19 and 20 with PMe2Ph were carried out analogously to give trans-[PtCl(PMe2Ph)2{C(OMe)dCHPh}] (24) and trans-[PtCl(PMe2Ph)2{C(OiPr)dCHPh}] (25), respectively. (E)-24, 1H NMR (rt, CD2Cl2): δ 1.81 (br, PCH3, 6H), 3.74 (s, OCH3, 3H), 5.12 (s, JPtH=42 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -6.2 (s, JPtP =2783 Hz). (Z)-24, 1H NMR (rt, CD2Cl2): δ 1.64 (vt, JPH =4 Hz, JPtH =33 Hz, PCH3, 3H), 1.76 (vt, JPH =4 Hz, JPtH =30 Hz, PCH3, 3H), 3.45 (s, OCH3, 3H), 5.94 (s, JPtH =88 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -7.1 (s, JPtP=2831 Hz). (E)-25, 1H NMR (rt, CD2Cl2): δ 1.070 (d, JHH = 6 Hz, OCH(CH3)2, 6H), 1.83 (vt, JPH = 4 Hz, 195Pt satellite peaks were not observed by overlapping, PCH3, 3H), 1.86 (vt, JPH=4 Hz, JPtH=34 Hz, PCH3, 3H), 4.97 (sep, JHH= 6 Hz, OCH, 1H), 5.27 (s, JPtH = 43 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): -5.03 (s, JPtP=2852 Hz). (Z)-25, 1H NMR (rt, CD2Cl2): δ 1.074 (d, JHH=6 Hz, OCH(CH3)2, 6H), 1.63 (vt, JPH=4 Hz, JPtH=34 Hz, PCH3, 3H), 1.78 (vt, JPH=4 Hz, JPtH= 28 Hz, PCH3, 3H), 4.48 (sep, JHH =6 Hz, OCH, 1H), 6.04 (s, JPtH=90 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): -7.68 (s, JPtP =2877 Hz). Reactions of 21 with PPh3 was performed analogously to give trans-[PtCl(PPh3)2{C(OEt)dCHPh}] (26). (E)-26, 1H NMR (rt, CD2Cl2): δ 0.53 (t, JHH=7 Hz, OCH2CH3, 3H), 3.78 (q, JHH= 7 Hz, OCH2, 2H), 5.06 (s, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): 20.8 (s, JPtP=3077 Hz). (Z)-26, 1H NMR (rt, CD2Cl2): δ 0.80 (t, JHH = 7 Hz, OCH2CH3, 3H), 2.50 (q, JHH = 7 Hz, OCH2, 2H), 4.94 (s, JPtH =84 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): 22.0 (s, JPtP =3170 Hz). Reaction of in Situ Prepared trans-[PtCl(PMe2Ph)2{C(NPh2)(CH2Ph)}]þCl- (22) with NEt3. cis-[PtCl2(PMe2Ph){C(NPh2)(CH2Ph)}] (5.7 mg, 0.0084 mmol) was dissolved in CD2Cl2, and then 1,4-dioxane (0.012 mmol) was added as an internal standard. Then, PMe2Ph (0.0084 mmol) was added to the solution. NMR analysis after 1 h revealed the formation of trans-[PtCl(PMe2Ph)2{C(NPh2)(CH2Ph)}]þCl- (22) (conv. 100%). 22: 1H NMR (rt, CD2Cl2): δ 1.77 (vt, JPH=4 Hz, JPtH=31 Hz, PCH3, 3H), 1.81 (vt, JPH=4 Hz, JPtH=30 Hz, PCH3, 3H), 3.76 (s, JPtH= 31 Hz, CH2Ph, 2H). 31P{1H} NMR (rt, CD2Cl2): δ -9.3 (s, JPtP =2530 Hz). To the above solution of 22 was added NEt3 (0.0086 mmol), and NMR spectra were measured. 22 completely disappeared and instead formation of trans-[PtCl(PMe2Ph)2{(Z)-C(NPh2)d CHPh}] ((Z)-27) was observed in 93% yield. The E/Z isomerization was not detected at 30 °C for 21 h. (Z)-27: 1H NMR (rt, CD2Cl2): δ 1.65 (vt, JPH =4 Hz, JPtH =28 Hz, PCH3, 3H), 1.71 (vt, JPH=4 Hz, 28 Hz, PCH3, 3H), 5.83 (s, JPtH=104 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -9.1 (s, JPtP =2907 Hz). Reaction of in Situ Prepared (PhMe2P)(CO){μ-PhHCd(EtO)C}Pt-Co(CO)3 (13) with PMe2Ph. (PhMe2P)(CO){μPhHCd(EtO)C}Pt-Co(CO)3 (13) was in situ prepared by the reaction of (PhMe2P)Cl{(PhCH2)(EtO)C}Pt-Co(CO)4 (6) with benzylamine. 6 (7.6 mg, 0.011 mmol) was dissolved in CD2Cl2. Then dibenzyl in CD2Cl2 (0.0035 mmol) and CH4 (150 μL) were added as internal standards. Then PhCH2NH2 (0.011 mmol) was added to the solution to generate 13. After 3 h at 30 °C, a mixture of (E)- and (Z)-13 was formed in 69 and 19% (E/Z = 79:21) yields, respectively. Then 1 equiv of PMe2Ph (0.011 mmol) was added to the solution. Formation of cis-(PhMe2P)2{μ-PhHCd(EtO)C}Pt-Co(CO)3 (28) was confirmed by NMR, and an equimolar amount of CO (0.013 mmol,

Tanaka et al. 114%/13) gas was detected by GC. Then, excess PMe2Ph (0.0984 mmol) was added to the solution to give [Pt(PMe2Ph)3{C(OEt)dCHPh}]þ[Co(PMe2Ph)n(CO)m]- (29). The NMR tube was placed in an oil bath at 30 °C, and the E/Z isomerization was periodically monitored by NMR. (E)-28, 1H NMR (rt, CD2Cl2): δ 1.39 (t, JHH=7 Hz, OCH2CH3, 3H), 3.84 (m, OCH2, 1H), 4.18 (m, OCH2, 1H), 5.04 (d, JPH = 4 Hz, CHPh, 1H). 31 P{1H} NMR (rt, CD2Cl2): δ -7.48 (d, JPP=12 Hz, JPtP=2449 Hz), -11.76 (d, JPP=12 Hz, JPtP=3685 Hz). (Z)-28, 1H NMR (rt, CD2Cl2): δ 1.31 (t, JHH = 7 Hz, OCH2CH3, 3H), 3.67 (m, OCH2, 1H), 4.1 (m, OCH2, 1H), 5.74 (d, JPH = 9 Hz, JPtH = 42 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -8.61 (d, JPP = 12 Hz, JPtP = 2409 Hz), -14.55 (d, JPP = 12 Hz, JPtP = 3628 Hz). (E)-29, 1H NMR (rt, CD2Cl2): δ 4.48 (q, JHH=7 Hz, OCH2, 2H), 5.3 (overlapped with solvent peak, JPtH = 31 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -8.75 (d, JPP = 22 Hz, JPtP=2597 Hz), -18.92 (t, JPP=22 Hz, JPtP=1813 Hz). (Z)-29, 1H NMR (rt, CD2Cl2): δ 3.92 (q, JHH = 7 Hz, OCH2, 2H), 6.55 (d, JPH =13 Hz, JPtH =64 Hz, CHPh, 1H). 31P{1H} NMR (rt, CD2Cl2): δ -12.19 (d, JPP =24 Hz, JPtP =2691 Hz), -19.92 (t, JPP =24 Hz, JPtP =1794 Hz). Reaction of Aminocarbene Complexes (Ph3P)Cl(Me2NHC)Pt-M0 L0 n with Tertiary Phosphine Ligand. Reaction of (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1) with PPh3. 1 3 C6H6 (97.6 mg, 0.122 mmol) and PPh3 (41.5 mg, 0.158 mmol) were dissolved in acetone to give a yellow solution, which was stirred at room temperature for 3 h to cause decoloration. The resultant solution was concentrated, and excess benzene was added to precipitate the product. After filtration, the precipitates were washed with benzene and hexane and then dried under a vacuum to give a white powder. Recrystallization from acetone/benzene gave trans-[PtCl(PPh3)2(CHNMe2)]þ[Co(CO)4]- 3 C6H6 (30 3 C6H6) as pale yellow needles. Yield: 64% (83.2 mg, 0.0784 mmol). Anal. Calcd for C49H43ClCoNO4P2Pt: C, 55.45; H, 4.08; N, 1.32. Found: C, 55.25; H, 4.24; N, 1.34. Molar electric conductivity Λ (THF, rt): 18 S cm2 mol-1. Reaction of (Ph3P)Cl(Me2NHC)Pt-Mn(CO)5 (2) with PPh3. The acetone solution containing 2 (94.4 mg, 0.127 mmol) and PPh3 (36.2 mg, 0.138 mmol) was stirred at 30 °C for 12 h. The orange color of the solution turned yellow. Evaporation of volatile matter gave a yellow solid, which was washed with benzene and hexane. The solid was recrystallized from acetone/ benzene to give trans-[PtCl(PPh3)2(CHNMe2)]þ[Mn(CO)5]- 3 C6H6 (31 3 C6H6) as yellow microcrystals. Yield: 55% (76.1 mg, 0.0701 mmol). Anal. Calcd for C50H43ClMnNO5P2Pt: C, 55.33; H, 3.99; N, 1.29. Found: C, 55.48; H, 4.00; N, 1.31. Reaction of (Ph3P)Cl(Me2NHC)Pt-Co(CO)4 (1) with Ph2PC2H4PPh2 (dppe). 1 3 C6H6 (111.9 mg, 0.1401 mmol) and dppe (61.9 mg, 0.155 mmol) were dissolved in acetone and stirred at room temperature for 1 h. The resultant solution was concentrated, and then excess benzene was added to precipitate the product. Filtration gave a yellow solid, which was washed with benzene and hexane and then dried under a vacuum to give a pale yellow powder of [PtCl(dppe)(CHNMe2)]þ[Co(CO)4](32). Yield: 79% (95.3 mg, 0.111 mmol). Theoretical Calculations. DFT calculation of the model complex trans-[PtCl(PH3)2{C(OMe)dCHPh}] was performed with the Spartan06 program package (Wavefunction, Inc., Irvine, CA) at the B3LYP level using the LACVP*. The optimized structures represent the equilibrium geometries of the molecules in the gas phase. The computed total energies of E and Z isomers of trans-[PtCl(PH3)2{C(OMe)dCHPh}] were -4435310.41 and -4435312.85 kJ/mol, respectively. X-ray Structure Analysis. The crystallographic data were measured on a Rigaku RASA-7R four-circle diffractometer using Mo KR (λ=0.71069 A˚) radiation with a graphite crystal monochromator at -73 °C. A single crystal was selected by use of a polarized microscope and mounted onto a capillary using Paraton N oil. The unit cells were determined by the automatic indexing of the 20 centered reflections. Intensity data were

Article collected using the ω-2θ technique to a maximum 2θ of 54.9°. Intensities were corrected for Lorentz and polarization effects. All calculations were performed using the CrystalStructure 3.824 crystallographic software package except for refinement, which was performed using SHELXL-97.25 An absorption correction was applied with the program PSI SCAN for 1, 2, and 6. Structures were solved by the heavy-atom Patterson method26 for 1 and 2 and by direct methods (SIR92)27 for 6 and expanded using Fourier techniques.28 All non-hydrogen atoms were refined by full-matrix least-squares techniques with anisotropic displacement parameters based on F2 with all reflections except the incorporated solvent molecule in 2. All hydrogen atoms were added geometrically and refined by using a riding model. For complexes 1 and 2, intensity decay was observed in 3.39 and 21.21%, respectively, and the decay corrections were applied. (24) CrystalStructure 3.8, Crystal Structure Analysis Package,; Rigaku and Rigaku/MMC: The Woodlands, TX 77381, 2000-2006. (25) Sheldrick, G. M. SHELX-97, Programs for crystal structure determination (SHELXS) and refinement (SHELXL); University of G€ ottingen: G€ ottingen, Germany, 1997. (26) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF program system, Technical Report of the Crystallography Laboratory; University of Nijmegen: The Netherlands, 1992. (27) SIR92: Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla, M.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435. (28) DIRDIF99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF99 program system, Technical Report of the Crystallography Laboratory; University of Nijmegen: The Netherlands, 1999.

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The C(15)-C(20) bond in 2 was restrained to be a six-membered ring (AFIX 66 command). The crystallographic data and selected bond distances and angles are summarized in Tables 3 and 4, respectively. For complex (E)-11, single crystals were obtained from THF/hexane. However, sufficient diffraction data could not be obtained, and only a brief structural feature was discussed in the text. Two independent molecules of (E)-11 were found in the unit cell. The only Pt, Mo, and P atoms were refined with anisotropic displacement parameters. The phenyl and Cp rings in (E)-11 were restrained as rigid groups (AFIX 66 and AFIX 59, respectively). C(12) and C(38) atoms are located and fixed at the positions of the difference Fourier peaks, and their displacement parameters were not refined. Crystal data for (E)-11: C26H27MoO4PPt, fw = 725.50, monoclinic, Cc (No. 9), a=33.381(17) A˚, b=9.06(3) A˚, c=18.360(18) A˚, β=112.18(5)°, V=5144.1(181) A˚3, Z=8, Dcalcd =1.873 g/cm3, μ(Mo Ka) = 59.891 cm-1, 2θmax = 55.0°, 5966 reflections measured (5965 unique), R1 (wR2) = 0.1283 (0.3691), GOF = 1.408.

Acknowledgment. This work was financially supported by a grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Supporting Information Available: Crystallographic data are given as CIF files for complexes 1, 2, 6, and (E)-11. This material is available free of charge via the Internet at http://pubs.acs.org.