The sequential linking of alkynes at a dimolybdenum centre. Crystal structures of [Mo₂{µ-(MeO₂CC₂CO₂Me)(HC₂H)(MeO₂CC₂CO₂Me)₂}(η-C₅H₅)₂]·2CH₂Cl₂and [Mo₂{µ-(MeO₂CC₂CO₂Me)₄}(η-C₅H₅)₂]

Abstract

Reaction of [Mo,(CO)~(~-HC,H) (?-C,H,),] with Me0,CC-CC0,Me affords several products, one of which, of molecular formula [Mo,((HC,H) (Me02CC2C0,Me),)(q-C5H5)2] ( l ) , is here the subject of an X-ray diffraction study. Crystals of (1) are triclinic, space group P7 (no. 2) with Z = 2 in a unit cell of dimensions a = 11.519(7), b = 18.602(9), c = 8.709(3) A, ct = 86.65(4), p = 100.99(4), y = 97.54(5)', and they encapsulate two molecules of solvent (CH,CI,) per molecule of complex. The structure has been refined to R 0.054 for 3 450 reflections. The acetylenic moieties have joined to form a c 8 chain ; within this chain the terminal atoms and the two central atoms are attached to one of the metal atoms, while the first three and the last three form x-ally1 attachments to the other metal atom. The (C,H,)Mo=Mo(C,H,) unit and the C8 chain together form a framework of mirror symmetry, but the molecule as a whole does not possess C, symmetry because of the methoxycarbonyl ligands which are bonded to C(11), C(12), C(13), C(14), C(17), and C(18). When a similar reaction is carried out with [MO,(CO)~(~-MeO,CC,CO,Me)(q-C5H5),] as the starting material, one of the products is again a complex containing a c8 chain with methoxycarbonyl ligands on all eight carbon atoms, [Mo,{p-( Me0,CC,C02Me),}(q-C5H5)2] (2). An X-ray diffraction study of (2) reveals a remarkable difference in the bonding mode. Crystals of (2) are monoclinic, space group P2,lc (no. 14) with Z = 4 in a unit cell of dimensions a = 14.737(2), b = 11.224(2), c = 23.882(5) A, p = 11 5.92(1)', and the structure has been refined to R 0.088 for 4 897 reflections. The molecule (2) has idealised C, symmetry (not crystallographically required), and the C, chain forms a ' flyover ' from one metal atom to the other. The two groups of four carbon atoms are each planar (and co-planar with the o-bonded metal atom) and form a diene-type interaction with the other metal atom. A further marked difference from ( 1) is that the central bond of the C8 chain, which in (1) is orthogonal to the Mo=Mo link, is in ( 2 ) parallel to that direction. The metalmetal distances, 2.618(1) A in (1) and 2.635(1) A in ( 2 ) , are indicative of Mo-Mo double bonding.

Reactions of co-ordinated ligands. Part 48. Reactivity studies of the octatrienediylidenedimolybdenum complexes [Mo2(µ-C8Me8)(η-C5H5)2] and [Mo2(µ-C8H4But4)(η-C5H5)2]. Crystal structures of [Mo2(µ-C8Me7CH2)(η-C5H5)2][CF3SO3], [Mo2(µ-C8M

“…spectrum of (la) is identical to (1) except that the methyl signal at 6 0.99 has a reduced intensity from 6 to 5 in accordance with two CH3 groups becoming CH3 and CH2D. Corresponding reactions with LiCCuMe,], Li[CuPh2], and NaCSMe] afforded the derivatives (5>- (7) respectively, n.m.r. data for which are presented in Table 1.…”

“…(one signal observed, see Experimental section for details). Additional C-H couplings observed C(4), 10, 'JCC(4)H( 6)] or 'JCC(4)H( 2)]; C (7), 11 and 6, ,JcC(7)H( 6)] and ,flC(7)H( 4)].…”

“…Thus treatment of the monoethyl derivative, (S), with 1 equivalent of [CPh,][BF,] afforded the cationic species (8) analogous to (4) which, on treatment with Li[CuMe2] gave the 6,6'-diethyl complex (9) Table 2. Selected bond lengths (A) and angles (") for complex ( 4) ( 10) 72.0(7) 13 1.7 (7) 123.9( 14) 6 5) 15) F( 4)-C(28)-F( 5) 117.8 (8) 0(4)-S(2)-0(5) 116.9( 8) F( 5)-C(28)-F( 6) 102.6( 16) F( 4)-C(28)-F( 6) 10 1.4( 16) 102.4( 9 -355( 6) -852( 6) -1 852( 8) -1 681( 6) -1 157(7) -386 (7) -1 460 (7) * Atomic site occupancy OX( 1); primed atoms have occupancy 0.49( 1). -527( 7) -1 025 (7) 5 480(8) 4 838( 6) 5 455(7) 5 898 (8) -368 ( 10) -927( 7)…”

“…-2 063( 8) -2 668( 16) -2 149( 15) -1 658( 7) -36( 8) 886( 7) 145( 7) -502( 8) -1 254 (10) -189 (11) -1 090 (12) 1 195 (7) 950( 9) 258( 12) 84( 11 (Scheme 2). Protonation of ( 9) with 1 equivalent of HBF4.Et20 resulted in complex (10) containing an agostic CH interaction analogous to that in (2).…”

Reactions of co-ordinated ligands. Part 43. Alkyne linking reactions at dimetal centres. Synthesis and structures of [Mo2{µ-(σ,η3:η2:η3,σ-C8H4But4)}(η-C5H5)2], [Mo2{µ-(σ,η3:η3,σ-CHCHButC6H2But3)}(η-C5H5)2], and [FeMo(CO)2(C4Me2Ph2

“…spectroscopy and single-crystal X-ray crystallography. In Carbons C(1), C(2), C(3) and C (6), C (7), C (8) each form an q3-allylic interaction with Mo(1) with C(4) and C(5) bonded as an q2-alkene to Mo (2). In contrast, complex (2) can be described as a 5-vinyl substituted C, 'fly-over' complex where the C, ligand bonds via a C-Mo 0 bond to Mo (2) and an q4-diene-like interaction to Mo (1).…”